阅读说明：本技术 燃料组合物和老化估计 (Fuel composition and aging estimation ) 是由 兰尼·基万 戈皮钱德拉·苏尼拉 克里斯多夫·保罗·格鲁格拉 马克·米恩哈特 罗斯·戴卡斯特拉 于 2020-02-20 设计创作，主要内容包括：本公开提供了“燃料组合物和老化估计”。提供用于估计车辆发动机中的燃料中的乙醇含量、燃料中的水含量以及所述燃料的使用期的方法和系统。在一个示例中,一种方法可包括：基于如在燃料喷射或泵冲程之后估计的压力脉动的共振频率(f)、燃料轨压力变化(δp)和所述燃料轨中的压力脉动的阻尼系数(α)来估计燃料乙醇含量、水含量或燃料使用期。一个或多个发动机运转参数可基于所估计燃料乙醇含量、水含量和燃料使用期来调整。(The present disclosure provides "fuel composition and aging estimation". Methods and systems are provided for estimating ethanol content in a fuel, water content in a fuel, and a lifetime of the fuel in a vehicle engine. In one example, a method may comprise: estimating a fuel ethanol content, a water content, or a fuel age based on a resonance frequency (f) of a pressure pulsation as estimated after a fuel injection or pump stroke, a fuel rail pressure variation (p), and a damping coefficient (α) of the pressure pulsation in the fuel rail. One or more engine operating parameters may be adjusted based on the estimated fuel ethanol content, water content, and fuel age.)

1. A method for an engine, comprising:

adjusting engine operation based on an estimated fuel age that is estimated based on at least two of a resonant frequency of a pressure pulsation after a fuel injection or pump stroke, a fuel rail pressure change, and a damping coefficient of the pressure pulsation in the fuel rail.

2. The method of claim 1, further comprising: estimating a fuel ethanol content and/or a fuel water content based on each of a resonant frequency of the pressure pulsation, the fuel rail pressure variation, and a damping coefficient of the pressure pulsation; and adjusting engine operation based on the estimated fuel ethanol content and/or water content.

3. The method of claim 1, further comprising: estimating a fuel rail temperature from each of a resonant frequency of the pressure pulsation, the fuel rail pressure variation, and a damping coefficient of the pressure pulsation.

4. The method of claim 1, wherein the fuel ethanol content is a percentage of ethanol in a fuel tank of an engine of a flexible fuel vehicle and wherein the fuel water content is a percentage of water in the fuel rail.

5. The method of claim 1, wherein the fuel age is a function of a storage duration of fuel in the fuel tank and a temperature and pressure of the fuel in the tank, the fuel age indicating a change in fuel composition due to vaporization of a volatile component of the fuel.

6. The method of claim 4, wherein the fuel rail pressure change is a fuel rail pressure difference as estimated via a fuel rail pressure sensor coupled to the fuel rail before and after the pump stroke of the fuel injection via an injector coupled to the fuel rail or a high pressure fuel pump.

7. The method of claim 6, wherein a resonant frequency of the pressure pulsation is estimated based on the pressure pulsation as estimated via the fuel rail pressure sensor coupled to the fuel rail immediately after the fuel injection or the pump stroke, and wherein the damping coefficient is estimated based on one or more of a fitting of an exponential function to a decay profile or envelope of the pressure pulsation, a Prony analysis, and a fast Fourier transform of the decay profile.

8. A method as defined in claim 1, wherein the fuel ethanol content is periodically estimated for at least a first threshold travel distance and/or travel duration after a refueling event, and the fuel life is periodically estimated after completion of a second threshold travel distance and/or travel duration since an immediately preceding fuel life estimation, the second threshold travel distance and/or travel duration being higher than the first threshold travel distance and/or travel duration.

9. The method of claim 1, wherein adjusting engine operation comprises: adjusting spark timing based on the estimated fuel ethanol content and/or the fuel age, the spark timing advancing to MBT in response to an increase in fuel ethanol content.

10. The method of claim 8, wherein adjusting engine operation further comprises: adjusting an amount of fuel injected during a cold start based on the estimated fuel ethanol content, fuel water content, and/or fuel age, the amount of fuel injected increasing during the cold start in response to an increase in the fuel ethanol and/or water content and an increase in fuel age.

11. The method of claim 2, further comprising: adjusting an injector pulse width during fuel injection based on the estimated fuel rail temperature.

12. The method of claim 1, further comprising: in response to one of the fuel age increasing above a threshold age and the water content of the fuel increasing above a threshold level, notifying an operator to use/replace the fuel.

13. An engine system, comprising:

a controller having computer readable instructions stored on a non-transitory memory that, when executed, cause the controller to:

upon completion of the fuel refill event,

estimating a fuel ethanol content based on a fuel rail pressure factor, and adjusting one or more of an injected fuel amount and spark timing based on the estimated fuel ethanol content; and

upon completion of the threshold duration since the immediately preceding fuel-usage estimate,

a fuel age is estimated based on a fuel rail pressure factor, and one or more of the injected fuel quantity, fuel injection timing, and spark timing are adjusted based on the estimated fuel age.

14. The system of claim 13, wherein the fuel rail pressure factor comprises: a change in fuel rail pressure in response to a stroke or injection event of a fuel pump, a damping coefficient for a pressure pulsation in the fuel rail immediately after the stroke or injection event, and a resonant frequency of the pressure pulsation in the fuel rail immediately after the stroke or injection event.

15. The system of claim 14, wherein the fuel pump is fluidly coupled to the fuel rail, and wherein the fuel rail is one of a direct injector rail and a port injector rail, the fuel rail including a fuel rail pressure sensor.

Technical Field

The present description relates generally to methods and systems for estimating ethanol content in fuel and fuel age in a vehicle engine.

Background

Flexible Fuel Vehicles (FFVs) are an alternative to conventional gasoline powered vehicles and include an internal combustion engine to burn a mixture of gasoline and a secondary fuel, such as ethanol, methanol, propanol or other alcohols and octane improvers. Fuel blends incorporating ethanol are particularly popular due to the derivation of ethanol from biomass, where various feedstocks are available from agriculture. The flexible fuel engine may be adapted to burn a 0-100% ethanol fuel mixture, thereby reducing the well-to-wheel carbon footprint compared to gasoline. In a hybrid vehicle, fuel may remain unused in the fuel tank because the vehicle may be propelled for long periods using only motor torque. Aging can lead to changes in fuel composition. For example, to determine an appropriate air-fuel ratio at a combustion chamber of an engine, the PCM may utilize an estimated or measured value of fuel composition (e.g., ethanol percentage) and fuel age to determine an amount of fuel to be injected.

Various methods are provided to estimate the ethanol content in a flex fuel. For example, in U.S. Pat. No. 7,523,723, Marriott et al discloses a method for determining the ethanol content of a fuel based on fuel rail pressure characteristics. An effective bulk modulus and a pressure disturbance signature of the fuel may be determined from the rail pressure, and the fuel ethanol content may be estimated based on one or more of the effective bulk modulus and the pressure disturbance signature of the fuel.

However, the inventors herein have recognized potential drawbacks of the above approach. As one example, Marriott et al does not disclose a method for determining the water content absorbed by ethanol or the age of the fuel in the fuel tank. Since ethanol in fuel that has been idle for a long time absorbs water, phase separation may occur, rendering the fuel ineffective for engine operation. In gasoline fuelOf lighter and more volatile moieties (molecules with fewer carbon atoms, e.g. C)₃And C₄) May evaporate leaving a heavy, less volatile portion of the aged gasoline fuel with a higher concentration. In a hybrid vehicle, fuel degradation may be significant because the engine may not be operating for a long period of time. The concentration of the lighter and heavier fractions may affect the amount of fuel required to be injected for combustion. Specialized sensors may be used for fuel composition or life determination, but adding separate components may increase manufacturing costs.

Disclosure of Invention

The inventors herein have recognized that the above-mentioned problems may be solved by a method for an engine, comprising: adjusting engine operation based on the estimated fuel age estimated based on at least two of a resonant frequency of a pressure pulsation in the fuel rail after fuel injection, a fuel rail pressure variation, and a damping coefficient of the pressure pulsation. Engine operation may be further adjusted based on the estimated ethanol content and water content in the fuel estimated based on the resonant frequency of the pressure pulsations after fuel injection, the fuel rail pressure variation, and the damping coefficient of the pressure pulsations in the fuel rail. In this way, by monitoring fuel properties as estimated by existing sensors, fuel ethanol content, fuel water content, and fuel aging may be estimated.

In one example, fuel ethanol content measurements may be taken immediately after a fuel refill event, and fuel aging and water content estimates may be taken periodically. In another example, the fuel aging estimation may be performed periodically. During operation of the fuel pump, the fuel rail pressure may be estimated via a fuel rail pressure sensor. The pulsation frequency, pressure variation, and damping coefficient of the pressure pulsation may be estimated after the fuel injection or pump stroke. In the absence of a fuel rail temperature sensor, in a flexible fuel vehicle, the fuel ethanol content may be estimated as a function of the pulsation frequency, the pressure variation, and the damping coefficient of the pressure pulsations. Furthermore, the water content in the fuel can be estimated from different functions of the pulsation frequency, the pressure variation and the damping coefficient of the pressure pulsation. In gasoline engines, fuel aging, which is a function of the concentration of lighter and heavier fractions of gasoline, may also be estimated as a function of two or more of the pulsation frequency, the pressure variation, and the damping coefficient of the pressure pulsations. Engine operating parameters (including spark timing and fuel injection amount) may be adjusted based on the estimated fuel ethanol content, fuel water content, and fuel age. If the fuel water content is above the threshold, an operator may be notified to use/replace the fuel in the fuel tank.

In this way, fuel ethanol content, water content, fuel age, and/or fuel rail temperature may be determined using fuel properties as estimated by existing fuel systems. By eliminating the need for dedicated fuel composition detection sensors and fuel rail temperature sensors, component costs can be reduced. In a flex fuel vehicle, by determining the fuel ethanol content after each refueling event, the resulting ethanol content in the fuel resulting from mixing of the fuel previously present in the tank with the newly delivered fuel may be estimated and used to determine the air-fuel ratio. The technical effect of periodically estimating fuel aging in gasoline is that degraded fuel can be identified in time and reported to an operator to maintain engine function. By adjusting engine operating parameters based on fuel ethanol content, fuel water content, or fuel age, engine performance, fuel efficiency, and emission quality may be improved.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

Drawings

FIG. 1 schematically depicts an exemplary embodiment of a cylinder coupled to an internal combustion engine of a hybrid vehicle.

FIG. 2 schematically depicts an exemplary embodiment of a fuel system that may be used with the engine of FIG. 1 configured for port injection and direct injection.

FIG. 3 shows a flow chart illustrating a first method for determining ethanol content in a flexible fuel powered vehicle.

Fig. 4 shows a flow chart illustrating a first method for determining gasoline aging.

FIG. 5 shows a flow chart illustrating a second method for determining ethanol content in a fuel.

Fig. 6 shows a flow chart illustrating a second method for determining gasoline aging.

FIG. 7 shows a plot illustrating changes in fuel rail pressure in response to fuel pump stroke.

FIG. 8 shows a plot illustrating changes in fuel rail pressure in response to fuel injection.

FIG. 9 shows a plot illustrating resonant pulsation of fuel rail pressure in response to fuel injection.

FIG. 10 shows a plot illustrating damping of pressure pulsations in the fuel rail after fuel injection.

FIG. 11 illustrates a relationship between ethanol content in fuel and damping of fuel rail pressure pulsations.

Fig. 12 shows the relationship between the ethanol content in the fuel and the damping coefficient.

FIG. 13 illustrates the relationship between the ethanol content in the fuel and the speed of sound through the fuel.

FIG. 14 illustrates an exemplary determination of fuel ethanol content using fuel rail pressure.

FIG. 15 illustrates an exemplary determination of fuel rail pressure versus fuel age.

FIG. 16 shows a flow chart illustrating a third method for determining ethanol content in a fuel.

FIG. 17 shows a flow chart illustrating a third method for determining fuel aging.

FIG. 18 illustrates an exemplary determination of fuel ethanol content using ultrasonic signals.

FIG. 19 illustrates an exemplary determination of fuel life using ultrasonic signals.

Detailed Description

The following description relates to systems and methods for estimating ethanol content, water content, and age of fuel contained in an engine fuel tank. An exemplary embodiment of a cylinder in an internal combustion engine having each of a direct fuel injector and a port fuel injector is given in FIG. 1. FIG. 2 depicts a fuel system that may be used with the engine of FIG. 1. The engine controller may be configured to execute an exemplary routine to determine the ethanol and water content of the fuel and fuel aging based on the fuel rail temperature, the change in fuel rail pressure, the fuel rail pressure pulsation frequency, and the damping coefficient of the pressure pulsation after a fuel injection or fuel pump stroke, such as in accordance with the methods described in fig. 3-6. The engine controller may also be configured to determine fuel ethanol content and fuel age based on attenuation of the ultrasonic signal in the fuel, as described in fig. 17-18. Exemplary plots 7-10 show pressure changes due to damping of fuel pump stroke, fuel injection, resonant frequency vibrations, and pressure vibrations, respectively. Exemplary relationships between fuel ethanol content and fuel rail pressure pulsations, damping coefficients for the pressure pulsations, and sound speed in the fuel are shown in fig. 11-13, respectively. Exemplary determinations of fuel ethanol content and fuel age are shown in fig. 14, 15, 18, and 19.

FIG. 1 depicts an example of a cylinder 14 of an internal combustion engine 10, which internal combustion engine 10 may be included in an engine system 100 in a vehicle 5. Engine 10 may be controlled at least partially by a control system including controller 12 and by input from a vehicle operator 130 via an input device 132. In this example, the input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The cylinders (also referred to herein as "combustion chambers") 14 of the engine 10 may include combustion chamber walls 136 with pistons 138 positioned in the combustion chamber walls 136. Piston 138 may be coupled to crankshaft 140 such that reciprocating motion of the piston is translated into rotational motion of the crankshaft. Crankshaft 140 may be coupled to at least one drive wheel of a passenger vehicle via a transmission. Further, a starter motor (not shown) may be coupled to crankshaft 140 via a flywheel to enable a starting operation of engine 10.

Cylinder 14 may receive intake air via a series of intake passages 142, 144, and 146. Intake passage 146 may also communicate with other cylinders of engine 10 in addition to cylinder 14. In some examples, one or more of the intake passages may include a boosting device, such as a turbocharger or a supercharger. For example, FIG. 1 shows engine 10 configured with a turbocharger including a compressor 174 disposed between intake passages 142 and 144 and an exhaust turbine 176 disposed along exhaust passage 148. Where the boosting device is configured as a turbocharger, compressor 174 may be at least partially powered by exhaust turbine 176 via shaft 180. However, in other examples, such as where engine 10 is provided with a supercharger, exhaust turbine 176 may optionally be omitted, where compressor 174 may be powered by mechanical input from the motor or the engine. A throttle 162 including a throttle plate 164 may be disposed along an intake passage of the engine to vary the flow rate and/or pressure of intake air provided to the engine cylinders. For example, throttle 162 may be positioned downstream of compressor 174, as shown in FIG. 1, or alternatively may be positioned upstream of compressor 174.

Exhaust passage 148 may receive exhaust gases from other cylinders of engine 10 in addition to cylinder 14. Exhaust gas sensor 128 is shown coupled to exhaust passage 148 upstream of emission control device 178. Sensor 128 may be selected from a variety of suitable sensors for providing an indication of exhaust gas air/fuel ratio such as, for example, a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO (as depicted), a HEGO (heated EGO), a NOx, HC, or CO sensor. Emission control device 178 may be a Three Way Catalyst (TWC), NOx trap, various other emission control devices, or combinations thereof.

Each cylinder of engine 10 may include one or more intake valves and one or more exhaust valves. For example, cylinder 14 is shown to include at least one intake poppet valve 150 and at least one exhaust poppet valve 156 located at an upper region of cylinder 14. In some examples, each cylinder of engine 10 (including cylinder 14) may include at least two intake poppet valves and at least two exhaust poppet valves located at an upper region of the cylinder.

Intake valve 150 may be controlled by controller 12 via actuator 152. Similarly, exhaust valve 156 may be controlled by controller 12 via actuator 154. During some conditions, controller 12 may vary the signals provided to actuators 152 and 154 to control the opening and closing of the respective intake and exhaust valves. The position of intake valve 150 and exhaust valve 156 may be determined by respective valve position sensors (not shown). The valve actuators may be electrically actuated or cam actuated or a combination thereof. The intake and exhaust valve timing may be controlled simultaneously, or any of the possible configurations of variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, or fixed cam timing may be used. Each cam actuation system may include one or more cams and may utilize one or more of Cam Profile Switching (CPS), Variable Cam Timing (VCT), Variable Valve Timing (VVT), and/or Variable Valve Lift (VVL) systems that may be operated by controller 12 to vary valve operation. For example, cylinder 14 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and/or VCT. In other examples, the intake and exhaust valves may be controlled by a common valve actuator or actuation system or a variable valve timing actuator or actuation system.

Cylinder 14 may have a compression ratio, which is the ratio of the volume when piston 138 is at bottom center to top center. In one example, the compression ratio is in the range of 9:1 to 10: 1. However, in some examples where different fuels are used, the compression ratio may be increased. This may occur, for example, when higher octane fuels or fuels with higher latent heats of vaporization (latent). The compression ratio may also be increased if direct injection is used due to effects on engine knock.

In some examples, each cylinder of engine 10 may include a spark plug 192 for initiating combustion. Ignition system 190 can provide an ignition spark to combustion chamber 14 via spark plug 192 in response to spark advance signal SA from controller 12, under select operating modes. However, in some embodiments, spark plug 192 may be omitted, such as where engine 10 may initiate combustion by auto-ignition or by injection of fuel, as may be the case with some diesel engines.

In some examples, each cylinder of engine 10 may be configured with one or more fuel injectors for providing fuel to the cylinder. As a non-limiting example, cylinder 14 is shown to include two fuel injectors 166 and 170. Fuel injectors 166 and 170 may be configured to deliver fuel received from fuel system 8. As detailed with reference to FIG. 2, the fuel system 8 may include one or more fuel tanks, fuel pumps, fuel rails, and fuel rail sensors. Fuel injector 166 is shown coupled directly to cylinder 14 for injecting fuel directly into cylinder 14 via electronic driver 168 in proportion to the pulse width of signal FPW-1 received from controller 12. In this manner, fuel injector 166 enables so-called direct injection (hereinafter referred to as "DI") of fuel into combustion cylinder 14. Although FIG. 1 shows injector 166 positioned to one side of cylinder 14, injector 166 may alternatively be located overhead of the piston, such as near spark plug 192. Because some alcohol-based fuels have a lower volatility, such a location may improve mixing and combustion when operating an engine with an alcohol-based fuel. Alternatively, the injector may be located overhead and near the intake valve to improve mixing. Fuel may be delivered to fuel injector 166 from a fuel tank of fuel system 8 via a high pressure fuel pump and a fuel rail. Further, the fuel rail may have a pressure sensor and a temperature sensor that provide signals to the controller 12.

Fuel injector 170 is shown disposed in intake passage 146, rather than cylinder 14, and is configured to enable so-called port injection of fuel into the intake port upstream of cylinder 14 (hereinafter referred to as "PFI"). Fuel injector 170 may inject fuel received from fuel system 8 via electronic driver 171 in proportion to the pulse width of signal FPW-2 received from controller 12. It should be noted that a single driver 168 or 171 may be used for both fuel injection systems, or multiple drivers may be used, for example, driver 168 for fuel injector 166 and driver 171 for fuel injector 170, as depicted.

In an alternative example, each of fuel injectors 166 and 170 may be configured as a direct fuel injector for injecting fuel directly into cylinder 14. In still another example, each of fuel injectors 166 and 170 may be configured as a port fuel injector for injecting fuel upstream of intake valve 150. In still other examples, cylinder 14 may include only a single fuel injector configured to receive different fuels from the fuel system in varying relative amounts as a fuel mixture, and further configured to inject this fuel mixture directly into the cylinder as a direct fuel injector or upstream of the intake valve as a port fuel injector. As such, it should be appreciated that the fuel system described herein should not be limited by the particular fuel injector configuration described herein by way of example.

During a single cycle of the cylinder, fuel may be delivered to the cylinder through both injectors. For example, each injector may deliver a portion of the total fuel injection combusted in cylinder 14. Further, the distribution and/or relative amount of fuel delivered from each injector may vary with operating conditions, such as engine load, knock, and exhaust temperature, such as described herein below. Port injected fuel may be delivered during an open intake valve event, a closed intake valve event (e.g., substantially before the intake stroke), and during both open and closed intake valve operation. Similarly, directly injected fuel may be delivered during the intake stroke and partially during the previous exhaust stroke, during the intake stroke, and partially during the compression stroke, for example. Thus, even for a single combustion event, the injected fuel may be injected from the port injector and the direct injector at different timings. Further, multiple injections of the delivered fuel may be performed per cycle for a single combustion event. Multiple injections may be performed during a compression stroke, an intake stroke, or any suitable combination thereof.

Fuel injectors 166 and 170 may have different characteristics. These different characteristics include size differences, for example, one injector may have a larger injection orifice than another injector. Other differences include, but are not limited to, different spray angles, different operating temperatures, different steering, different injection timing, different spray characteristics, different locations, and the like. Further, depending on the distribution ratio of the injected fuel among injectors 170 and 166, different effects can be achieved.

The fuel tanks in fuel system 8 may contain fuels of different fuel types, such as fuels having different fuel qualities and different fuel compositions. The differences may include different alcohol content, different water content, different concentrations of lighter and heavier hydrocarbon fractions, different octane numbers, different heat of vaporization, different fuel blends, and/or combinations thereof, and the like. One example of fuels with different heats of vaporization may include gasoline with a lower heat of vaporization as a first fuel type and ethanol with a higher heat of vaporization as a second fuel type. In another example, the engine may use a flex fuel containing an alcohol such as E85 (which is approximately 85% ethanol and 15% gasoline) or M85 (which is approximately 85% methanol and 15% gasoline) as the second fuel type. Other possible substances include water, methanol, alcohol and water mixtures, water and alcohol mixtures, and the like.

In yet another example, the two fuels may be alcohol blends with varying alcohol compositions, where the first fuel type may be a gasoline alcohol blend with a lower concentration of alcohol, such as E10 (which is about 10% ethanol), and the second fuel type may be a gasoline alcohol blend with a higher concentration of alcohol, such as E85 (which is about 85% ethanol). Additionally, the first fuel and the second fuel may also differ in other fuel qualities, such as temperature differences, viscosity differences, octane value differences, and the like. Further, the fuel properties of one or both fuel tanks may change frequently, for example, due to day-to-day changes in tank refilling.

The controller 12 is shown in fig. 1 as a microcomputer, said controller 12 comprising a microprocessor unit 106, an input/output port 108, an electronic storage medium for executable programs and calibration values (shown in this particular example as a non-transitory read only memory chip 110 for storing executable instructions), a random access memory 112, a keep alive memory 114 and a data bus. In addition to those signals previously discussed, controller 12 may receive various signals from sensors coupled to engine 10, including: a measurement of intake Mass Air Flow (MAF) from mass air flow sensor 122; engine Coolant Temperature (ECT) from temperature sensor 116 coupled to cooling sleeve 118; a surface ignition pickup signal (PIP) from Hall effect sensor 120 (or other type) coupled to crankshaft 140; a Throttle Position (TP) from a throttle position sensor; manifold absolute pressure signal (MAP) from sensor 124; a fuel rail pressure from a fuel rail pressure sensor; a fuel rail temperature from a fuel rail temperature sensor; and the ultrasonic signal amplitude from the ultrasonic signal sensor. Engine speed signal, RPM, may be generated by controller 12 from signal PIP. Manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of vacuum or pressure in the intake manifold. The controller 12 receives signals from the various sensors of FIG. 1 and employs the various actuators of FIG. 1 to adjust engine operation based on the received signals and instructions stored on a memory of the controller.

As described above, FIG. 1 shows only one cylinder of a multi-cylinder engine. Thus, each cylinder may similarly include its own set of intake/exhaust valves, one or more fuel injectors, spark plugs, etc. It should be appreciated that engine 10 may include any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Further, each of these cylinders may include some or all of the various components described and depicted by fig. 1 with reference to cylinder 14.

In some examples, the vehicle 5 may be a hybrid vehicle having multiple torque sources available for one or more wheels 55. In other examples, the vehicle 5 is a conventional vehicle having only an engine or an electric vehicle having only one or more electric machines. In the illustrated example, the vehicle 5 includes an engine 10 and a motor 52. The electric machine 52 may be a motor or a motor/generator. When one or more clutches 56 are engaged, a crankshaft 140 of engine 10 and motor 52 are connected to wheels 55 via transmission 54. In the depicted example, the first clutch 56 is disposed between the crankshaft 140 and the motor 52, while the second clutch 56 is disposed between the motor 52 and the transmission 54. Controller 12 may send a clutch-engaging or clutch-disengaging signal to an actuator of each clutch 56 to connect or disconnect crankshaft 140 from motor 52 and components connected to motor 52, and/or to connect or disconnect motor 52 from transmission 54 and components connected to transmission 54. The transmission 54 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various ways, including a parallel, series, or series-parallel hybrid vehicle.

The electric machine 52 receives electrical power from the traction battery 58 to provide torque to the wheels 55. The electric machine 52 may also operate as a generator to provide electrical power to charge the battery 58, such as during braking operations.

FIG. 2 schematically depicts an exemplary embodiment 200 of a fuel system (such as fuel system 8 of FIG. 1). The fuel system 200 may be operated to deliver fuel to an engine, such as the engine 10 of FIG. 1.

The fuel system 200 includes a fuel storage tank 210 for storing fuel on-board the vehicle, a low pressure fuel pump (LPP)212, and a high pressure fuel pump (HPP)214 (also referred to herein as fuel pump 214). Fuel may be provided to the fuel tank 210 via the fuel fill passage 204. In one example, the LPP 212 may be an electric low pressure fuel pump disposed at least partially within the fuel tank 210. The LPP 212 may be operated by a controller 222 (e.g., controller 12 of fig. 1) to provide fuel to the HPP 214 via a fuel passage 218. The LPP 212 may be configured as a so-called fuel lift pump. As one example, the LPP 212 may be a turbine (e.g., centrifugal) pump that includes an electric (e.g., DC) pump motor, whereby a pressure increase across the pump and/or a volumetric flow rate through the pump may be controlled by varying the electrical power provided to the pump motor, thereby increasing or decreasing the motor speed. For example, as the controller reduces the electrical power provided to the lift pump 212, the volumetric flow rate and/or pressure increase across the lift pump may be reduced. The volumetric flow rate and/or pressure increase across the pump may be increased by increasing the electrical power provided to the lift pump 212. As one example, the electric power supplied to the low-pressure pump motor may be obtained from an alternator or other energy storage device (not shown) on the vehicle, whereby the control system may control the electrical load used to power the low-pressure pump. Thus, by varying the voltage and/or current provided to the low pressure fuel pump, the flow rate and pressure of the fuel provided at the inlet of high pressure fuel pump 214 is adjusted.

The LPP 212 may be fluidly coupled to a filter 217, which filter 217 may remove small impurities contained in the fuel that may potentially damage the fuel processing components. A check valve 213, which may facilitate fuel delivery and maintain fuel line pressure, may be positioned fluidly upstream of the filter 217. With the check valve 213 upstream of the filter 217, the compliance of the low pressure passage 218 may increase because the volume of the filter may be physically large. Further, a pressure relief valve 219 may be employed to limit the fuel pressure in the low pressure passage 218 (e.g., output from the lift pump 212). The pressure relief valve 219 may include, for example, a ball and spring mechanism that seats and seals at a specified pressure differential. The pressure differential set point at which the pressure relief valve 219 may be configured to open may assume various suitable values; as a non-limiting example, the set point may be 6.4 bar or 5 bar (g). The orifice 223 may be utilized to allow air and/or fuel vapor to be bled off of the lift pump 212. This bleed at orifice 223 may also be used to power a jet pump used to transfer fuel from one location within tank 210 to another. In one example, an orifice check valve (not shown) may be placed in series with orifice 223. In some embodiments, the fuel system 8 may include one or more (e.g., a series of) check valves fluidly coupled to the low-pressure fuel pump 212 to prevent fuel from leaking back upstream of the valves. In this context, upstream flow refers to the fuel flow traveling from the fuel rail 250, 260 toward the LPP 212, while downstream flow refers to the nominal fuel flow direction from the LPP toward the HPP 214 and on the HPP 214 to the fuel rail.

The fuel lifted by the LPP 212 may be supplied at low pressure into a fuel passage 218 leading to the inlet 203 of the HPP 214. The HPP 214 may then deliver fuel to a first fuel rail 250, the first fuel rail 250 coupled to one or more fuel injectors of a first group of direct injectors 252 (also referred to herein as a first injector group). The fuel lifted by the LPP 212 may also be supplied to a second fuel rail 260, which second fuel rail 260 is coupled to one or more fuel injectors of a second set of port injectors 262 (also referred to herein as a second injector set). The HPP 214 is operable to raise the pressure of fuel delivered to a first fuel rail to above a lift pump pressure, where the first fuel rail coupled to the direct injector group operates at high pressure. Thus, high pressure DI may be enabled while PFI may be operated at lower pressures.

While each of the first and second fuel rails 250, 260 is shown as distributing fuel to four fuel injectors in the respective injector groups 252, 262, it will be appreciated that each fuel rail 250, 260 may distribute fuel to any suitable number of fuel injectors. As one example, the first fuel rail 250 may distribute fuel to one fuel injector of the first injector group 252 for each cylinder of the engine, while the second fuel rail 260 may distribute fuel to one fuel injector of the second injector group 262 for each cylinder of the engine. Controller 222 may independently actuate each of port injectors 262 via port injection driver 237 and each of direct injectors 252 via direct injection driver 238. The controller 222, drives 237, 238 and other suitable engine system controllers may comprise a control system. While the drivers 237, 238 are shown external to the controller 222, it should be appreciated that in other examples, the controller 222 may include the drivers 237, 238 or may be configured to provide the functionality of the drivers 237, 238. Controller 222 may include additional components not shown, such as those included in controller 12 of fig. 1.

The HPP 214 may be an engine-driven positive displacement pump. As one non-limiting example, the HPP 214 may be a BOSCH HDP5 high pressure pump that utilizes solenoid activated control valves (e.g., fuel volume regulators, magnetic solenoids, etc.) to vary the effective pump volume per pump stroke. The outlet check valve of the HPP is mechanically controlled by an external controller, rather than electronically. In contrast to the motor-driven LPP 212, the HPP 214 may be mechanically driven by the engine. The HPP 214 includes a pump piston 228, a pump compression chamber 205 (also referred to herein as a compression chamber), and a step-room 227. The pump piston 228 receives mechanical input from the engine crankshaft or camshaft via the cam 230, thereby operating the HPP according to the principles of a cam-driven, single cylinder pump. A sensor (not shown in fig. 2) may be positioned near the cam 230 to enable determination of the angular position of the cam (e.g., between 0 and 360 degrees), which may be relayed to the controller 222.

A lift pump fuel pressure sensor 231 may be positioned along the fuel passage 218 between the lift pump 212 and the high pressure fuel pump 214. In this configuration, the reading from the sensor 231 may be interpreted as an indication of the fuel pressure of the lift pump 212 (e.g., the lift pump outlet fuel pressure) and/or the inlet pressure of the high pressure fuel pump. Readings from sensor 231 may be used to evaluate the operation of various components in fuel system 200 to determine whether sufficient fuel pressure is being provided to high-pressure fuel pump 214 to enable the high-pressure fuel pump to draw in liquid fuel rather than fuel vapor, and/or to minimize the average electrical power supplied to lift pump 212.

The first fuel rail 250 includes a first fuel rail pressure sensor 248 and a first fuel rail temperature sensor 232 for providing indications of the direct injection fuel rail pressure and the first fuel rail temperature, respectively, to the controller 222. Likewise, the second fuel rail 260 includes a second rail pressure sensor 258 and a first rail temperature sensor 232 for providing port injection rail pressure and second rail temperature, respectively, to the controller 222.

The fuel rail pressure sensors 248 and/or 258 and the fuel rail temperature sensors 232 and/or 234 may be used to determine the ethanol content and/or the age of the fuel in the fuel tank 210. For flex fuels (containing ethanol), the fuel ethanol content is the percentage of ethanol in the fuel contained in the fuel tank 210 of the engine fuel system. For gasoline, fuel age is an indication of the change in fuel composition over time due to vaporization of the lighter, more volatile portion of the fuel. The vaporized portion of the fuel may be routed to a fuel vapor storage tank or to the atmosphere. The fuel aging process is a function of the duration and conditions (such as temperature changes during the diurnal cycle) that the fuel is stored in the fuel tank. In one example, if the fuel is stored at a higher temperature (such as in hot ambient conditions) for a longer period of time, the vaporization process may be accelerated, thereby increasing the fuel life. In a hybrid vehicle, fuel life may be estimated periodically after completion of a threshold travel distance and/or travel duration since an immediately previous fuel life estimation. In a flex fuel vehicle, fuel ethanol content may be periodically estimated for at least a first threshold travel distance and/or travel duration after a refueling event, and fuel water content may be periodically estimated after completion of a second threshold travel distance and/or travel duration since an immediately previous fuel life estimation, the second threshold travel distance and/or travel duration being higher than the first threshold travel distance and/or travel duration.

The volume fraction of ethanol in the fuel contained in the fuel tank 210, the volume fraction of water in the fuel, and the age of the fuel may be estimated based on the estimated fuel rail temperature and one of the pulsation frequency, the pressure variation, and the damping coefficient of the pressure pulsation as estimated after the fuel injection or pump stroke. The pressure change during a fuel pump stroke or fuel injection may be a function of the bulk modulus of the fuel, the damping coefficient of pressure pulsations in a fuel rail (such as the first fuel rail 250) immediately after the fuel pump stroke or fuel injection may be a function of the viscosity of the fuel, and the resonant frequency of the pressure pulsations in the fuel rail may be a function of the speed of sound in the fuel. One or more engine operating parameters may be adjusted in response to the estimates of fuel ethanol content, water content, and fuel age. As an example, the amount of fuel injected during a cold start may be increased in response to an increase in the volume fraction of ethanol or an increase in the fuel age, and the commanded air-fuel ratio may be decreased in response to an increase in the volume fraction of ethanol, and spark timing may be advanced in response to an increase in the volume fraction of ethanol. Methods for fuel ethanol content, water content, and/or aging determination are discussed in detail with reference to fig. 3-6.

In an alternative embodiment, the fuel rail temperature sensors 232 and 234 may be eliminated and the fuel rail temperature may be determined based on the fuel rail pressure change. If the fuel rail temperature is unknown, such as in a port injection system without a fuel rail temperature sensor, the volume fractions of ethanol and water in the fuel in the flexible fuel vehicle and the fuel rail temperature may be estimated based on at least three of the pulsation frequency, the pressure variation, and the damping coefficient of the pressure pulsation as estimated after fuel injection or pump stroke. In a hybrid vehicle, the fuel life and the fuel rail temperature may be estimated based on at least two of the pulsation frequency, the pressure variation, and the damping coefficient of the pressure pulsation as estimated after the fuel injection or the pump stroke. The method for fuel rail temperature determination is discussed in detail with reference to fig. 5-6.

An engine speed sensor 233 may be used to provide an indication of engine speed to the controller 222. Since the pump 214 is mechanically driven by the engine 202, e.g., via a crankshaft or camshaft, an indication of engine speed may be used to identify the speed of the high pressure fuel pump 214.

The first fuel rail 250 is coupled to the outlet 208 of the HPP 214 along a fuel passage 278. A check valve 274 and a pressure relief valve (also referred to as a pump relief valve) 272 may be positioned between the outlet 208 of the HPP 214 and the first (DI) fuel rail 250. Pump relief valve 272 may be coupled to bypass passage 279 of fuel passage 278. The outlet check valve 274 opens to allow fuel to flow from the high pressure pump outlet 208 into the fuel rail only when the pressure at the outlet of the direct injection fuel pump 214 (e.g., the compression chamber outlet pressure) is higher than the fuel rail pressure. The pump relief valve 272 may limit the pressure in the fuel passage 278 downstream of the HPP 214 and upstream of the first fuel rail 250. For example, pump relief valve 272 may limit the pressure in fuel passage 278 to 200 bar. When the fuel rail pressure is greater than the predetermined pressure, pump relief valve 272 allows fuel to flow out of DI fuel rail 250 toward pump outlet 208. Valves 244 and 242 work together to maintain low pressure fuel rail 260 pressurized to a predetermined low pressure. The pressure relief valve 242 helps to limit pressure that may build up in the fuel rail 260 due to thermal expansion of the fuel.

Based on engine operating conditions, fuel may be delivered by one or more port injectors 262 and direct injectors 252. For example, during high load conditions, fuel may be delivered to the cylinder in a given engine cycle via direct injection only, with port injector 262 disabled. In another example, during mid-load conditions, fuel may be delivered to the cylinder in a given engine cycle via each of direct injection and port injection. As yet another example, during low load conditions, engine start, and warm idle conditions, fuel may be delivered to the cylinder in a given engine cycle via port injection only, with the direct injector 252 disabled.

It should be noted here that the high-pressure pump 214 of fig. 2 is presented as an illustrative example of one possible configuration of a high-pressure pump. The components shown in FIG. 2 may be removed and/or replaced, while additional components not currently shown may be added to the pump 214, while still maintaining the ability to deliver high pressure fuel to both the direct injection fuel rail and the port injection fuel rail.

In an alternative embodiment, the fuel system may include only port injector 262, rather than both a direct injector and port injector 262. Also, in the case of fuel injection via port injector 262, the second fuel rail 260 may be eliminated. A fuel temperature sensor 243 may be housed in the fuel tank to help estimate the fuel temperature in the tank. An ultrasonic signal generator 240 may be coupled to a wall of the fuel tank 210, and an ultrasonic sensor 241 may be coupled to the generator 240. The ultrasonic signal generator 240 may generate ultrasonic waves, which may pass through the fuel in the tank. The waves may reflect off of a stationary object, such as a wall of the tank opposite the wall on which the signal generator 240 is mounted. In this way, the ultrasonic signal may be generated by an ultrasonic signal generator coupled to the first wall of the fuel tank, and the ultrasonic signal may be detected by an ultrasonic sensor coupled to the first wall adjacent to the ultrasonic signal generator, each of the ultrasonic signal generator and the ultrasonic sensor being immersed in the fuel. The speed of sound in the fuel may be estimated based on a travel time of the reflected ultrasonic signal to and from a second wall opposite the first wall and a distance between the first wall and the second wall. Also, an attenuation coefficient of the ultrasonic signal in the fuel may be estimated based on an amplitude difference between the generated ultrasonic signal and the reflected ultrasonic signal. The volume fraction of ethanol in the fuel contained in the fuel tank or the age of the fuel may be estimated based on each of the fuel temperature, the speed of sound in the fuel, and the attenuation coefficient of the ultrasonic signal in the fuel. Methods for fuel ethanol content and/or aging determination using ultrasonic signals are discussed in detail with reference to fig. 15-16.

The controller 222 may also control the operation of each of the fuel pumps 212 and 214 to adjust the amount, pressure, flow rate, etc. of fuel delivered to the engine. As one example, the controller 222 may change a pressure setting of the fuel pump, a pump stroke amount, a pump duty cycle command, and/or a fuel flow rate to deliver fuel to different locations of the fuel system. A driver (not shown) electronically coupled to the controller 222 may be used to send control signals to the low pressure pump to adjust the output (e.g., speed, flow output, and/or pressure) of the low pressure pump as needed.

In this manner, the system discussed above at fig. 1 and 2 may activate an engine system that includes: a controller having computer readable instructions stored on a non-transitory memory that, when executed, cause the controller to: upon completion of the fuel refill event, a fuel ethanol content and a water content are estimated based on the temperature of the fuel rail and each of the two fuel rail pressure factors and one or more of an amount of fuel injected and a spark timing is adjusted based on the estimated fuel ethanol content and the water content, or a fuel age is estimated based on each of the temperature of the fuel rail and the fuel rail pressure factors and one or more of an amount of fuel injected and a fuel injection timing is adjusted when a threshold duration since an immediately preceding fuel age estimation is completed. The fuel rail pressure factor may include one or more of: a change in fuel rail pressure in response to a stroke of the fuel pump or fuel injection, a damping coefficient of a pressure pulsation in the fuel rail immediately after the stroke or injection, and a resonant frequency of the pressure pulsation in the fuel rail immediately after the stroke or injection.

FIG. 3 illustrates an example method 300 that may be implemented to estimate the volume fractions of ethanol and water in fuel. The instructions for implementing the method 300 and the remaining methods included herein may be executed by the controller based on instructions stored on a memory of the controller in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference to fig. 1 and 2. The controller may employ engine actuators of the engine system to adjust engine operation according to the method described below.

At 302, current vehicle and engine operating parameters may be determined. The parameters may include vehicle speed, torque demand, engine speed, engine temperature, and the like. The controller may estimate the amount of fuel supplied to the fuel injectors (direct and/or port injectors) via a first fuel rail (such as first fuel rail 250 in FIG. 2) coupled to a direct injector (such as direct injector 252 in FIG. 2) and a second fuel rail (such as second fuel rail 260 in FIG. 2) coupled to a port injector (such as port injector 262 in FIG. 2). The controller may monitor operation of a fuel pump (such as high-pressure pump 214 in fig. 2), such as timing of fuel pump strokes.

At 304, the routine includes determining whether the conditions for fuel ethanol content determination are met. Ethanol content determination may be practiced in engines using flexible fuels containing ethanol, such as E85 containing 85% ethanol. Thus, in some examples, the ethanol content determination may be carried out only in vehicles configured to operate using ethanol fuel (e.g., flexible fuel vehicles). In one example, the ethanol content estimation may be performed after vehicle refueling is detected.

The conditions may include the vehicle being propelled via engine torque while fuel is supplied to the injectors via a fuel rail (such as a first fuel rail). The condition may also include a refueling event that has occurred within a threshold amount of time. When using a fuel that may contain ethanol for refueling, the fuel remaining in the fuel tank may mix with the fuel being dispensed, resulting in a fuel blend of the existing fuel with the new fuel. The ethanol content and water content of the fuel blend may be different than the ethanol content and water content of the existing fuel or the delivered fuel, and the ethanol content of the fuel blend may be estimated within a threshold duration (or threshold travel distance) after the refueling event. For example, such an estimation may be made within 1 day of refueling or within 10 miles of travel after refueling. Since the amount of water absorbed by ethanol may change over time (between refueling events), the conditions may also include a threshold duration since a previous fuel ethanol content estimate. For example, such estimation may be carried out periodically, such as every 15 days. If it is determined that the conditions for the fuel ethanol content determination are not met, then at 306, current engine operation may continue without making the fuel ethanol content determination. Engine operation may include supplying fuel to one or more fuel injectors via one or more fuel rails.

If it is determined that the conditions of the fuel ethanol content determination are met, at 308, a fuel rail temperature may be estimated via a fuel rail temperature sensor (such as the first fuel rail temperature sensor 232 in FIG. 2) coupled to the fuel rail. Alternatively, the fuel rail temperature may be estimated using empirical models that are based on physics or that correlate fuel rail temperature to engine operating conditions and states.

At 310, two or more of a resonant frequency (f) of the pressure pulsation, a fuel rail pressure change (p), and a damping coefficient (α) of the pressure pulsation in the fuel rail may be estimated after a fuel injection or pump stroke. In one example, the fuel bulk modulus may be estimated based on a function of a fuel rail pressure change (p) due to a pump stroke or an injection event, the speed of sound in the fuel may be estimated based on a function of a resonant frequency (f) of a pressure pulsation in the fuel rail due to a pump stroke or a fuel injection, and the fuel viscosity may be estimated based on a function of a damping coefficient (α) of the pressure pulsation in the fuel rail after the pump stroke or the fuel injection.

To estimate one or more of the fuel rail pressure change (p), the resonant frequency (f) of the pressure pulsation, and the damping coefficient (α) of the pressure pulsation, the pump stroke of a high-pressure fuel pump (such as the HP fuel pump 214 in fig. 2) housed in the fuel tank may be determined. The pump stroke may correspond to operation of a pump to deliver fuel from a fuel tank to a direct injector fuel rail via a fuel line. The fuel rail pressure change (increase) may be determined via a fuel rail pressure sensor (such as pressure sensor 248 in fig. 2) immediately after the pump stroke. The fuel rail pressure may increase during a pump stroke when the pump is operated to transfer fuel from the fuel tank to the fuel rail. As an example, the controller may estimate the change in pressure magnitude or pressure slope during the pump stroke.

The controller may determine a direct fuel injection event that results in at least a threshold change (decrease) in the amount of fuel remaining in the rail. Fuel may be injected via one or more direct injectors (such as direct injector 252) coupled to the fuel rail. The duration of the fuel injection may be estimated. The duration may include the time elapsed between the start of fuel injection to a particular cylinder and the completion of fuel injection in a single fuel injection event. Fuel may be pumped from the fuel tank to the direct injectors via fuel lines and rails. The reduction in the amount of fuel remaining in the rail after the injection event may result in a decrease in fuel rail pressure. The fuel rail pressure change (decrease) may be determined via a fuel rail pressure sensor (such as pressure sensor 248 in fig. 2) immediately after fuel injection. In this way, the fuel rail pressure change may be estimated immediately after fuel injection or fuel pump stroke.

After a pump stroke or fuel injection, pressure pulsations may be generated at the fuel rail. The fuel rail pulsation may have a resonant frequency. The resonant frequency of the pressure pulsations in the fuel rail may be determined after a pump stroke or fuel injection via processing a pressure signal from a fuel rail pressure sensor (such as pressure sensor 248 in fig. 2).

Pressure pulsations generated at the fuel rail after a fuel injection or pump stroke may be dampened as the magnitude of the pulsations decrease over time. The amplitude of the pressure pulsations may decay at an exponential rate. A damping coefficient for pressure pulsations in the fuel rail may be determined. An exponential curve may be fitted to the decay amplitude profile of the pressure pulsations and/or an exponential function may be fitted to the pressure signal envelope. In one example, the damping coefficient may be constant in an exponential function. In another example, an exponentially decreasing sinusoid may be fitted to the decaying pressure pulsations. The damping coefficient may be constant in an exponential function (multiplied by a sinusoid). In yet another example, the damping coefficient may be estimated using a Prony analysis. A Fast Fourier Transform (FFT) of the pressure signal may also be used to estimate the damping coefficient, since the amplitude of the resonant frequency component obtained from the FFT is a function of the damping coefficient.

FIG. 7 shows an exemplary plot 700 illustrating fuel rail pressure over time. The y-axis represents fuel rail pressure (in psi) and the x-axis represents time (in seconds). The pressure may be estimated via a pressure sensor (such as pressure sensor 248 in fig. 2) coupled to the fuel rail.

At time t1, a fuel pump stroke may begin and continue until time t 2. Between times t1 and t2, the fuel tank pressure steadily increases as shown by line 702. After the pump stroke is complete, the pressure may reach equilibrium. The pressure differential (Δ P1) between the pressure at time t1 and the pressure at time t2 may be the change in fuel rail pressure immediately after the fuel pump stroke. Also, the slope of the fuel rail pressure plot between times t1 and t2 may be estimated.

FIG. 8 shows an exemplary plot 800 illustrating fuel rail pressure over time. The y-axis represents fuel rail pressure (in psi) and the x-axis represents time (in seconds). The pressure may be estimated via a pressure sensor (such as pressure sensor 248 in fig. 2) coupled to the fuel rail. The map is generated based on an experiment in which the fuel injection duration is set at 2 ms.

The first fuel injection may occur at time t1, followed by the second fuel injection at time t 2. As seen in line 802, Δ P2 may be the fuel rail pressure differential immediately before and after the first fuel injection, and Δ P3 may be the fuel rail pressure differential before and after the second fuel injection.

FIG. 9 shows an exemplary plot 900 illustrating resonant frequency pulsations in the fuel rail after a pump stroke. The y-axis represents fuel rail pressure (in psi) and the x-axis represents time (in seconds). The pressure may be estimated via a pressure sensor (such as pressure sensor 248 in fig. 2) coupled to the fuel rail. As seen in line 902, pressure pulsation troughs occur at times t1, t2, t3, and so on. The frequency may be determined using a Fast Fourier Transform (FFT) or Prony analysis.

FIG. 10 shows an exemplary plot 1000 illustrating damping of pressure pulsations in a fuel rail after fuel injection. The y-axis represents fuel rail pressure (in psi) and the x-axis represents time (in seconds). The pressure may be estimated via a pressure sensor (such as pressure sensor 248 in fig. 2) coupled to the fuel rail. As seen in line 1002, an exponential curve can be fitted to the amplitude of decay of the pressure pulsation. The damping coefficient may be estimated based on an exponential function of the fitted curve. The damping coefficient may also be estimated based on an exponential function of the damped sinusoid or using Prony analysis or FFT.

At 312, the fuel ethanol content (volume fraction) may be estimated based on the fuel rail temperature, the resonant frequency (f) of the pressure pulsations, the fuel rail pressure variation (p), and the damping coefficient (α) of the pressure pulsations in the fuel rail as estimated after the fuel injection or pump stroke. During conditions when fuel water content is unknown, fuel ethanol content may be estimated from fuel rail temperature and two of the resonant frequency (f) of the pressure pulsations, the fuel rail pressure change (p), and the damping coefficient (α) of the pressure pulsations in the fuel rail. In other words, the fuel ethanol content may be estimated based on the fuel rail temperature and at least two of the estimated fuel bulk modulus, the speed of sound in the fuel, and the fuel viscosity. In one example, a first estimate of ethanol content may be calculated as a function of fuel rail temperatures f and α, and a second estimate may be calculated as a function of fuel rail temperatures p and α. The ethanol content may then be estimated based on a weighted average of the first estimate and the second estimate. A weighted average from estimates based on different functions may be used to improve accuracy.

During conditions where the fuel water content is known, the fuel ethanol content may be estimated according to one of the following: a first function of the resonant frequency (f) and the fuel rail temperature, a second function of the fuel rail pressure change (p) in the fuel and the fuel rail temperature, and a third function of the damping coefficient (α) and the fuel rail temperature.

FIG. 11 illustrates an exemplary plot 1100 depicting ethanol content in fuel versus a normalized Root Mean Square (RMS) envelope of fuel rail pressure pulsations. The x-axis represents time, and the y-axis represents the RMS envelope of rail pressure pulsations in fuels containing 0%, 50% or 100% ethanol. As can be seen from the plot, the rate of decay of the pressure pulsations becomes faster as the ethanol content of the fuel increases due to the higher viscosity of ethanol relative to gasoline.

FIG. 12 illustrates an exemplary plot 1200 depicting the relationship between ethanol content in fuel and the damping coefficient (α) of fuel rail pressure pulsations. The x-axis represents the number of measurements, while the y-axis represents the damping coefficient (in Hz) in fuels containing 0%, 50% or 100% ethanol. As can be seen from the plot, the damping coefficient increases with increasing fuel ethanol content.

FIG. 13 illustrates an exemplary plot 1300 depicting the relationship between ethanol content in a fuel and the speed of sound through the fuel. The speed of sound may be estimated based on the resonant frequency (f) of the pressure pulsations in the fuel. The x-axis represents the volume fraction of ethanol in the fuel (in%) and the y-axis shows the speed of sound in the fuel (in m/s). The speed of sound may vary with ethanol content rather than monotonically. Up to a 30% ethanol fraction, the sound velocity is inversely proportional to the ethanol fraction, while above a 30% ethanol fraction, the sound velocity is proportional to the ethanol fraction.

Returning to FIG. 3, at 312, fuel ethanol content may be estimated based directly on two or more of the damping coefficient for pressure pulsations α, the fuel rail pressure pulsation frequency f, the fuel rail pressure change during the pump stroke p, the fuel rail temperature T, and the fuel rail pressure p. As an example, if the water content is not significant, the damping coefficient α, the fuel rail pressure pulsation frequency f, and the fuel rail pressure change during the pump stroke p are the ethanol volume fraction y, the fuel rail temperature T, and the fuel rail pressure pAndas a function of (c).

The relationship between the above mentioned variables is given by:

wherein 1, 2.

Inverse mappingAndso thatAndcan be used to estimate the ethanol volume fraction. Can be determined from a fit (plot) or a look-up tableAnd

in this way, the ethanol volume fraction (y) can be determined using the relationship (1), (2), or (3):

if the dependence on fuel rail pressure (p) is negligible (such as less than 2%), the fuel rail pressure (p) may be deleted from the estimate, and the ethanol volume fraction may be estimated from the damping coefficient (α) and the fuel rail temperature (T) or from the fuel rail pressure pulsation frequency (f) and the fuel rail temperature (T)OrOrAndis estimated by the weighted average of (a). The inverse mapping may give two possible ethanol contents due to non-monotonic behavior. For example, 1160m/s sound velocity may correspond to 9% or 90% ethanol content. In this case, another parameter (e.g., a damping coefficient) may be used to determine which of the two estimates based on the speed of sound is the correct estimate. For example, if the ethanol content estimated based on the damping coefficient is 10%, the estimated value of 90% may be ignored, and the ethanol content may be estimated from a weighted average of 9% and 10%.

As another example, if the water content is significant but unknown, the damping coefficient α, the fuel rail pressure pulsation frequency f, and the fuel rail pressure change p during a pump stroke are the ethanol volume fraction y, the water volume fraction x, the fuel rail temperature T, and the fuel rail pressure Andas a function of (c).

The relationship between the above mentioned variables is given by:

the ethanol volume fraction (y) can be determined using the inverse relationship (1), (2) or (3):

in some countries, the flex fuel dispensed to a vehicle fuel tank may include water. Also, ethanol in the fuel may absorb water over time. At 313, the water content (volume fraction) in the fuel may be estimated based on the fuel rail temperature, the resonant frequency (f) of the pressure pulsations, the fuel rail pressure change (p), and the damping coefficient (α) of the pressure pulsations in the fuel rail as estimated after the fuel injection or pump stroke. The fuel water content may be estimated from the fuel rail temperature and two of a resonant frequency (f) of the pressure pulsations, a fuel rail pressure change (p), and a damping coefficient (α) of the pressure pulsations in the fuel rail. A weighted average of the estimated values based on the different inverse relations (1), (2) and (3) can be used to improve the accuracy of the estimated water content.

During conditions when the fuel ethanol content is known (such as estimated), the fuel water content may be estimated according to one of the following: a first function of the resonant frequency (f) and the fuel rail temperature, a second function of the fuel rail pressure change (p) in the fuel and the fuel rail temperature, and a third function of the damping coefficient (α) and the fuel rail temperature.

In this way, in one example, a map that is a function of two or more of bulk modulus, speed of sound, and viscosity may be used to estimate ethanol and water fractions. In another example, a direct mapping relating two or more of p, f, and a to ethanol and water fractions may be used. When direct mapping is used, the calculation of bulk modulus, speed of sound, and viscosity as intermediate variables may not be performed.

At 314, engine operation may be adjusted based on the estimated fuel ethanol content and/or the estimated fuel water content. The adjusted engine operating parameter may include adjusting an amount of fuel injected, a spark timing, and/or a fuel injection timing based on the detected change in fuel composition.

For example, if the ethanol percentage is increased, the octane level becomes higher and spark timing may be advanced due to the higher activation energy of ethanol compared to gasoline, which in turn extends the ignition period (for ethanol). Also, as the ethanol content increases, the octane number also increases, and the cooling effect from the DI injectors also increases, so spark timing may be advanced from boundary conditions to MBT timing in response to the increase in ethanol content. As another example, the amount of fuel injected at cold start may be increased in response to an increase in ethanol content such that sufficient fuel is vaporized prior to starting the engine. As another example, the amount (mass) of fuel injected may increase in response to an increase in ethanol content due to a decrease in the stoichiometric air-fuel ratio of ethanol. Also, each fraction of fuel delivered via DI and PFI may be adjusted based on an increase in ethanol content.

For example, if the fuel water content increases, the fuel burn rate may decrease and the ignition period may be extended, and the spark timing may be advanced to allow the ignition period to be longer. Moreover, as the water content of the fuel increases, the fraction of gasoline and/or ethanol in the fuel may decrease, and thus the amount of fuel injected may be increased by increasing injection timing and injection pulse width to maintain a desired amount of combustible (gasoline and/or ethanol) constituents. Further, as the water content of the fuel increases during cold start, the amount of fuel injected may be increased to maintain a desired amount of vaporized combustible components.

At 316, the routine includes determining whether the water content of the fuel is above a threshold level. The threshold level may be based on the fuel water content at which phase separation (between ethanol and water) may occur, thereby rendering the fuel ineffective for engine operation. The threshold may be pre-calibrated to be below the amount of fuel water that the fuel may become ineffective, so that the fuel may be used up before it degrades.

If it is determined that the fuel water content is above the threshold water content, at 320, an operator may be notified via a dashboard indicator that fuel needs to be depleted within a threshold time. The threshold time may be based on the water content of the fuel at which the fuel will become ineffective. In one example, the operator may refuel (add new fuel) so that the older fuel may mix with the newer fuel, thereby reducing the effect of the diluted fuel. If it is determined that the water content of the fuel is below a threshold level, it may be inferred that the fuel may continue to be used for engine operation. At 318, the current fuel may be indicated as being suitable for combustion.

The above mentioned method may be used to estimate the fuel ethanol content of the fuel in the fuel rail (non-fuel tank). In one example, if fuel in the fuel rail (such as injected to a cylinder) is not used between the fuel refill and the ethanol content estimation, there may be a difference in the ethanol content as estimated (based on the fuel in the fuel rail) relative to the ethanol content of the fuel in the fuel tank. The method described in FIG. 16 may be used to estimate fuel ethanol content in a fuel tank. Thus, because the composition of the fuel dispensed by the port injector may be different than the composition of the fuel dispensed by the direct injector, some vehicles may use two methods for fuel ethanol estimation as shown in FIGS. 3 and 16.

FIG. 4 illustrates an example method 400 that may be implemented to estimate a lifetime of a fuel, such as gasoline in a fuel tank. Fuel age is an indication of the change in fuel composition over time due to vaporization of the lighter, more volatile portion of the fuel. The fuel aging process varies with the duration and conditions of fuel storage in the fuel tank. At 402, current vehicle and engine operating parameters may be determined. The parameters may include vehicle speed, torque demand, engine speed, engine temperature, and the like. The controller may estimate the timing of fuel injection and the amount of fuel supplied to the fuel injectors (direct and/or port injectors) via a first fuel rail (such as first fuel rail 250 in FIG. 2) coupled to the direct injectors (such as direct injector 252 in FIG. 2) and a second fuel rail (such as second fuel rail 260 in FIG. 2) coupled to the port injectors (such as port injector 262 in FIG. 2). The controller may monitor operation of a fuel pump (such as high-pressure pump 214 in fig. 2), such as timing of fuel pump strokes.

At 404, the routine includes determining whether the conditions for the fuel life determination are met. The fuel age determination may be performed in an engine that uses gasoline as fuel. Thus, in some examples, the fuel age determination may be carried out only in a vehicle configured to operate using gasoline. In another example, if the alcohol content is known (such as based on an ethanol content fuel tank sensor and/or an adaptive algorithm using an exhaust gas oxygen sensor), fuel life estimation may be carried out in a vehicle configured to operate using a flexible fuel (such as containing alcohol).

The conditions may include the vehicle being propelled via engine torque while fuel is supplied to the injectors via a fuel rail (such as a first fuel rail). The condition may also include a first threshold duration of vehicle operation using motor torque (fuel not combusted). For example, if the vehicle is operating for 7 days without the engine running, the fuel life determination may be carried out at the immediately subsequent engine start. The internal electronic control unit preparation time (soak time), connecting the vehicle (vehicle to vehicle, infrastructure to vehicle), and/or a cell phone connected to the vehicle controller may be used to access the date and determine the time elapsed since the previous fuel usage. The condition may also include a second threshold duration of time elapsed since a previous fuel life estimate. For example, such estimation may be carried out periodically after every 15 days. Also, the condition may include a third threshold duration during which less than a threshold amount of fuel is consumed. If it is determined that the conditions for the fuel life determination are not met, then the current engine operation may continue without a fuel life determination at 406. Engine operation may include supplying fuel to one or more fuel injectors via one or more fuel rails.

If it is determined that the conditions of the fuel life determination are met, at 408, a fuel rail temperature may be estimated via a fuel rail temperature sensor coupled to the fuel rail (such as the first fuel rail temperature sensor 232 in FIG. 2). Alternatively, the fuel rail temperature may be estimated using empirical models that are based on physics or that correlate fuel rail temperature to engine operating conditions and states.

At 410, one or more of a resonant frequency (f) of the pressure pulsation, a fuel rail pressure change (p), and a damping coefficient (α) of the pressure pulsation in the fuel rail may be estimated after a fuel injection or pump stroke. The fuel bulk modulus may be estimated from a fuel rail pressure change (p) due to a fuel quantity change in the fuel rail, such as at a pump stroke or injection event, the speed of sound in the fuel may be estimated from a resonant frequency (f) of a pressure pulsation in the fuel rail due to a fuel pump stroke or fuel injection, and the fuel viscosity may be estimated from a damping coefficient (α) of the pressure pulsation in the fuel rail after the fuel pump stroke or fuel injection. The estimation of each of the resonant frequency (f) of the pressure pulsations, the fuel rail pressure variation (p), and the damping coefficient (α) of the pressure pulsations in the fuel rail is discussed in detail in step 310 of fig. 3 and will not be repeated.

At 412, fuel age may be estimated based on the fuel rail temperature as estimated after the fuel injection or pump stroke and at least one of a resonant frequency (f) of the pressure pulsation, a fuel rail temperature change (p), and a damping coefficient (α) of the pressure pulsation in the fuel rail.

As the fuel ages, lighter fractions (molecules with fewer carbon atoms, e.g., C) may occur₃And C₄) And the concentration of the heavier fraction changes. As an example, fuel aging may result in an increase in the concentration of the heavier portion and a decrease in the concentration of the lighter portion. Each of the fuel bulk modulus, the speed of sound in the fuel, and the fuel viscosity may be a function of the concentration of lighter and heavier portions of the gasoline (indicative of fuel age). In other words, fuel age may be estimated based on the fuel rail temperature and at least one of the estimated fuel bulk modulus, the speed of sound in the fuel, and the fuel viscosity.

In this way, fuel ethanol content may be estimated from a first function of the fuel rail temperature and two or more of the resonant frequency of the pressure pulsation, the fuel rail pressure variation, and the damping coefficient of the pressure pulsation, fuel age may be estimated from a second function of the fuel rail temperature and one or more of the resonant frequency of the pressure pulsation, the fuel rail pressure variation, and the damping coefficient of the pressure pulsation, and fuel water content may be estimated from a third function of the fuel rail temperature and two or more of the resonant frequency of the pressure pulsation, the fuel rail pressure variation, and the damping coefficient of the pressure pulsation. In calculating the first and third functions, the effect of fuel aging may be assumed to be insignificant, while in calculating the second function, the fuel ethanol content and the fuel water content may be assumed to be known or insignificant.

At 414, engine operation may be adjusted based on the estimated fuel age. The adjusted engine operating parameters may include the amount of fuel injected, spark timing, and fuel injection timing based on the detected change in fuel composition. For example, the aged fuel may have a greater concentration of the heavier, less volatile portion of gasoline, and thus a greater amount of fuel may be injected during a cold start. As an example, fuel injection timing and injection pulse width may be adjusted based on fuel age and/or different vaporization rates due to components of aged fuel. The fuel injection timing and injection pulse width may increase as the fuel age increases. As another example, spark timing may be advanced to MBT to account for ignition period variations due to fuel aging.

At 416, the routine includes determining whether the fuel life is above a threshold life. The threshold age may be based on an increased concentration of heavier portions where the fuel may be ineffective. The threshold may be pre-calibrated to be below a fuel age at which the fuel may become ineffective, so that the aging fuel may be used up before the fuel degrades.

If it is determined that the fuel life is above the threshold life, the operator may be notified via a dashboard indicator that fuel needs to be depleted within a threshold time at 418. The threshold time may be based on a fuel age over which the fuel will become ineffective. In one example, on a hybrid vehicle, the controller may increase the contribution of the engine to the total required electric power to consume the remaining fuel before it becomes ineffective. In another example, the operator may also refill (add new fuel) so that older (aged) fuel may be diluted, thereby reducing the effect of aged fuel. If it is determined that the fuel age is below the threshold age, it may be inferred that fuel may continue to be used for engine operation. At 420, the current fuel may be indicated as being suitable for combustion.

The above mentioned method may be used to estimate the fuel life of the fuel in the fuel rail (non-fuel tank). In one example, if the vehicle is not operating via engine torque (consuming fuel) for a long period of time, there may be a difference in fuel usage as estimated (based on fuel in the fuel rail) relative to the usage of fuel in the fuel tank. The method described in FIG. 17 may be used to estimate the life of fuel in a fuel tank. Thus, because the age of the fuel dispensed by the port injectors may be different than the age of the fuel dispensed by the direct injectors, some vehicles may use two methods for fuel age estimation as described in FIGS. 4 and 17.

In this way, during a first condition, a fuel rail temperature may be estimated, a volume fraction of ethanol and water in the fuel contained in the fuel tank may be estimated based on the estimated fuel rail temperature and two of the estimated bulk modulus of fuel, the estimated viscosity of fuel, and the speed of sound in the fuel, engine operation may be adjusted based on the estimated volume fraction of ethanol, while during a second condition, a fuel rail temperature may be estimated, a lifetime of the fuel contained in the fuel tank may be estimated based on the estimated fuel rail temperature and one of the estimated bulk modulus of fuel, the estimated viscosity of fuel, and the speed of sound in the fuel, and engine operation may be adjusted based on the lifetime of the fuel. The first condition may include completion of a refueling event, the fuel being a flexible fuel, and the second condition may include completion of a threshold travel distance and/or travel duration since an immediately previous fuel life estimate, the fuel being gasoline.

FIG. 5 illustrates an example method 500 that may be implemented to estimate a volume fraction of ethanol in fuel and a fuel rail temperature. Unlike the method of fuel ethanol content estimation described in FIG. 3, in this method, the fuel rail temperature is not used as an input for estimating fuel ethanol content. At 502, current vehicle and engine operating parameters may be determined. The determined parameters are detailed in step 302 in fig. 3 and will not be repeated.

At 504, the routine includes determining whether the conditions for fuel ethanol content determination are met. The conditions for the ethanol volume fraction are detailed in step 304 in fig. 3 and will not be repeated. If it is determined that the conditions for the fuel ethanol content determination are not met, then at 506, current engine operation may continue without making the fuel ethanol content determination. Engine operation may include supplying fuel to one or more fuel injectors via one or more fuel rails.

If it is determined that the conditions of the fuel ethanol content determination are satisfied, each of the resonant frequency (f) of the pressure pulsation, the fuel rail pressure variation (p), and the damping coefficient (α) of the pressure pulsation in the fuel rail may be estimated after the fuel injection or pump stroke at 508. The estimation of each of the resonant frequency (f) of the pressure pulsations, the fuel rail pressure variation (p), and the damping coefficient (α) of the pressure pulsations in the fuel rail is discussed in detail in step 310 of fig. 3 and will not be repeated. The fuel bulk modulus may be estimated from a fuel rail pressure change (p) as a result of a change in the amount of fuel in the fuel rail, such as at a pump stroke or injection event, the speed of sound in the fuel may be estimated from the resonant frequency (f) of the pressure pulsation in the fuel rail due to the fuel pump stroke or fuel injection, and the fuel viscosity may be estimated from the damping coefficient (α) of the pressure pulsation in the fuel rail after the fuel pump stroke or fuel injection.

At 510, fuel ethanol content (volume fraction) may be estimated based on a resonant frequency (f) of the pressure pulsations as estimated after fuel injection or pump strokes, a fuel rail pressure change (p), and a damping coefficient (α) of the pressure pulsations in the fuel rail. During conditions when the fuel water content is unknown, the fuel ethanol content may be estimated from each of a resonant frequency (f) of the pressure pulsations, a fuel rail pressure variation (p), and a damping coefficient (α) of the pressure pulsations in the fuel rail. In other words, the fuel ethanol content may be estimated based on each of the estimated fuel bulk modulus, the speed of sound in the fuel, and the fuel viscosity.

The fuel ethanol content may be estimated directly based on two or more of the damping coefficient of the pressure pulsations α, the fuel rail pressure pulsation frequency f, the fuel rail pressure change during the pump stroke p, and the fuel rail pressure p Andas a function of (c).

The relationship between the above mentioned variables is given by:

wherein 1, 2.

Inverse mapping l such thatCan be used to estimate ethanol volume fraction without knowledge of fuel rail temperature. L can be determined from a fit (plot) or a look-up table.

In this way, ethanol volume fraction (y) can be determined using relationship (4):

if the dependence on fuel rail pressure (p) is negligible (such as less than 2%), the fuel rail pressure (p) may be deleted from the estimate and the ethanol volume fraction may be estimated from the damping coefficient (α) and the fuel rail pressure pulsation frequency (f).OrThe fuel rail pressure (p) may also be deleted from the alternative inverse map if the dependence on the fuel rail pressure (p) is negligible.

If the fuel water content is significant and unknown, the damping coefficient α, the fuel rail pressure pulsation frequency f, and the fuel rail pressure change p during the pump stroke are the ethanol volume fraction y, the water volume fraction x, the fuel rail temperature T, and the fuel rail pressure Andas a function of (c). In this way, the ethanol content is estimated using an inverse mapping

In some countries, the flex fuel dispensed to a vehicle fuel tank may include water. Also, ethanol in the fuel may absorb water over time. At 511, the water content (volume fraction) in the fuel may be estimated based on each of the resonant frequency (f) of the pressure pulsation, as estimated after the fuel injection or pump stroke, the fuel rail pressure change (p), and the damping coefficient (α) of the pressure pulsation in the fuel rail.

At 512, a fuel rail temperature may be estimated based on each of a resonant frequency (f) of the pressure pulsations, a fuel rail pressure change (p), and a damping coefficient (α) of the pressure pulsations in the fuel rail. The fuel rail temperature (T) may be estimated directly based on two or more of a damping coefficient (α) of the pressure pulsation, a fuel rail pressure pulsation frequency (f), a fuel rail pressure change (p) during a pump stroke, and a fuel rail pressure (p). In one example, the fuel water content is not significant, and the fuel rail temperature (T) may be determined using an (inverse mapping) relationship (5):

if the dependence on the fuel rail pressure (p) is negligible (such as less than 2%), the fuel rail pressure (p) may be deleted from the estimated value and the fuel rail pressure may be estimated from the damping coefficient (α) and the fuel rail pressure pulsation frequency (f). In another example, the fuel water content is significant and unknown, and the fuel rail temperature (T) may be determined using the (inverse map) relationship (5):

the fueling may be adjusted based on the estimated fuel rail temperature. Since fuel volume is a function of pressure and temperature, the injector pulse width must be modified based on the fuel rail temperature to inject the target fuel quantity.

At 514, engine operation may be adjusted based on the estimated fuel ethanol content and water content. Exemplary adjustments are detailed in step 314 of fig. 3 and will not be repeated. In this way, engine operation may be estimated based on an estimated fuel ethanol content, which is estimated based on two or more of the fuel bulk modulus, the fuel viscosity, and the speed of sound in the fuel.

At 516, the routine includes determining whether the water content of the fuel is above a threshold level. The threshold level may be based on the fuel water content at which phase separation (between ethanol and water) may occur, thereby rendering the fuel ineffective for engine operation. The threshold may be pre-calibrated to be below the amount of fuel water that the fuel may become ineffective, so that the fuel may be used up before it degrades.

If it is determined that the fuel water content is above the threshold water content, at 520, an operator may be notified via a dashboard indicator that fuel needs to be depleted within a threshold time. The threshold time may be based on the water content of the fuel at which the fuel will become ineffective. In one example, the operator may refuel (add new fuel) so that the older fuel may mix with the newer fuel, thereby reducing the effect of the diluted fuel. If it is determined that the water content of the fuel is below a threshold level, it may be inferred that the fuel may continue to be used for engine operation. At 518, it may be indicated that the current fuel is suitable for combustion.

FIG. 6 illustrates an example method 600 that may be implemented to estimate a life of fuel in a fuel tank and a fuel rail temperature. As previously described, fuel aging may result in an increase in the concentration of the heavier portion and a decrease in the concentration of the lighter portion. Each of the fuel bulk modulus, the speed of sound in the fuel, and the fuel viscosity may be a function of the concentration of lighter and heavier portions of the gasoline (indicative of fuel age). Unlike the method for fuel life estimation described in FIG. 4, in this method, the fuel rail temperature is not used as an input for estimating fuel life. At 602, current vehicle and engine operating parameters may be determined. The parameters are detailed in step 402 in fig. 4 and will not be repeated.

At 604, the routine includes determining whether the conditions for the fuel life determination are met. The conditions are detailed in step 404 in fig. 4 and will not be repeated. If it is determined that the conditions for the fuel life determination are not met, then the current engine operation may be continued without making a fuel life determination at 606. Engine operation may include supplying fuel to one or more fuel injectors via one or more fuel rails.

If it is determined that the conditions for the fuel life determination are met, two or more of a resonant frequency (f) of the pressure pulsation, a fuel rail pressure change (p), and a damping coefficient (α) of the pressure pulsation in the fuel rail may be estimated after the fuel injection or pump stroke at 608. The estimation of each of the resonant frequency (f) of the pressure pulsations, the fuel rail pressure variation (p), and the damping coefficient (α) of the pressure pulsations in the fuel rail is discussed in detail in step 310 of fig. 3 and will not be repeated. The fuel bulk modulus may be estimated from a fuel rail pressure change (p) as a result of a change in the amount of fuel in the fuel rail, such as at a pump stroke or injection event, the speed of sound in the fuel may be estimated from the resonant frequency (f) of the pressure pulsation in the fuel rail due to the fuel pump stroke or fuel injection, and the fuel viscosity may be estimated from the damping coefficient (α) of the pressure pulsation in the fuel rail after the fuel pump stroke or fuel injection.

At 610, fuel age may be estimated based on two or more of a resonant frequency (f) of the pressure pulsations, a fuel rail pressure change (p), and a damping coefficient (α) of the pressure pulsations in the fuel rail. The fuel age indicative of the concentration of the lighter and heavier portions of the gasoline may be estimated from one of: a function of the resonant frequency (f) and the damping coefficient (α), a second function of the fuel rail pressure change (p) in the fuel and the damping coefficient (α), and a third function of the damping coefficient (α) and the resonant frequency (f). A weighted average of estimates from two or three of the previously mentioned functions may be used to improve accuracy. In other words, the fuel life may be estimated based on at least two of the estimated fuel bulk modulus, the speed of sound in the fuel, and the fuel viscosity.

At 612, a fuel rail temperature may be estimated from at least two of a resonant frequency (f) of the pressure pulsations, a fuel rail pressure change (p), and a damping coefficient (α) of the pressure pulsations in the fuel rail.

At 614, engine operation may be adjusted based on the estimated fuel age. Exemplary adjustments are detailed in step 414 in fig. 4 and will not be repeated. At 616, the routine includes determining whether the fuel life is above a threshold life. The threshold age may be based on an increase in the concentration of heavier portions of the fuel that may be ineffective. The threshold may be pre-calibrated to be below a fuel age at which the fuel may become ineffective, so that the aging fuel may be used up before the fuel degrades. If it is determined that the fuel life is above the threshold life, the operator may be notified via a dashboard indication that fuel needs to be depleted within a threshold time at 620. In one example, on a hybrid vehicle, the controller may increase the contribution of the engine to the total required electric power to consume the remaining fuel before it becomes ineffective. In another example, the operator may refuel (add new fuel) so that older (aged) fuel may be diluted, thereby reducing the effect of the aged fuel. At 618, the current fuel may be indicated as suitable for combustion and no fuel change notification may be provided.

In this way, during a first condition, the volume fractions of ethanol and water in the fuel contained in the fuel tank may be estimated based on (at least) two of the estimated fuel bulk modulus, the estimated fuel viscosity, and the sound speed in the fuel, the engine operation may be adjusted based on the estimated ethanol volume fraction, while during a second condition, the age of the fuel contained in the fuel tank may be estimated based on (at least) two of the estimated fuel bulk modulus, the estimated fuel viscosity, and the sound speed in the fuel, and the engine operation may be adjusted based on the age of the fuel, and during each of the first and second conditions, the fuel rail temperature may be estimated based on (at least) two of the estimated fuel bulk modulus, the estimated fuel viscosity, and the sound speed in the fuel. The first condition may include completion of a refueling event, the fuel being a flexible fuel, and the second condition may include completion of a threshold travel distance and/or travel duration since an immediately previous fuel life estimate, the fuel being gasoline.

FIG. 16 illustrates an example method 1600 that may be implemented to estimate a volume fraction of ethanol in a flex fuel containing ethanol. In contrast to the method for fuel ethanol content estimation, this method may be used to determine the ethanol content of fuel in a fuel tank rather than a fuel rail, as described in FIG. 3. Because this method uses a sensor housed in the fuel tank to make the ethanol content estimate, this method may be used in systems that do not have a direct injector coupled to the fuel rail and/or may be practiced during engine operation when fuel is dispensed by a port injector.

At 1602, current vehicle and engine operating parameters may be determined. The parameters may include vehicle speed, torque demand, engine speed, engine temperature, and the like. The controller may estimate the amount of fuel supplied from the fuel tank to a fuel injector, such as port injector 262 in FIG. 1.

At 1604, the routine includes determining whether conditions for fuel ethanol content determination are met. The condition may include a refueling event. During refueling, the fuel remaining in the fuel tank may be mixed with the dispensed fuel, resulting in a fuel blend of existing fuel and new fuel. The ethanol content of the fuel blend may be estimated within a threshold duration (or threshold travel distance) after a refueling event. For example, such an estimation may be made within 1 day of refueling or within 10 miles of travel after refueling. The conditions may also include a threshold duration of time elapsed since a previous fuel ethanol content estimate. For example, such estimation may be carried out periodically after every 15 days.

If it is determined that the conditions for the fuel ethanol content determination are not met, then at 606, current engine operation may continue without making a fuel ethanol content determination. Engine operation may include supplying fuel from a fuel tank to one or more fuel injectors. If it is determined that the conditions of the fuel ethanol content determination are met, a fuel tank ultrasonic signal generator (such as ultrasonic signal generator 240 in FIG. 2) coupled to the interior of the fuel tank (coupled to the first tank wall) may be activated at 1608. The ultrasonic signal generator may generate an ultrasonic signal that may travel through the fuel from a first wall of the fuel tank (where the generator is positioned) to an opposing second wall of the fuel tank. The ultrasonic signal generator may reflect from the second wall of the tank and may return to the first wall. The reflected ultrasonic signal may be received at an ultrasonic sensor (such as ultrasonic sensor 241 in fig. 2) coupled to the first wall adjacent to the ultrasonic signal generator.

At 1610, a travel time of the reflected ultrasonic signal from the second fuel tank wall may be estimated. As an example, the timer may be set when the generator located at the first wall first generates an ultrasonic signal, and the timer may be stopped when the reflected ultrasonic signal (from the second wall) returns as detected by the ultrasonic sensor proximally coupled to the generator. The duration of time elapsed between the start and stop of the timer may be the travel time of the ultrasonic signal to and from the second wall.

At 1612, a speed of sound in the fuel may be estimated based on the estimated travel time. The distance between the first wall and the second wall may be retrieved from the controller memory. The speed of sound in the fuel may be estimated from the distance between the first wall and the second wall and the estimated travel time of the ultrasonic signal.

At 1616, attenuation of the ultrasonic signal in the fuel may be estimated. The ultrasonic signal may be attenuated as it travels through the fuel between the first wall and the second wall. In other words, the amplitude of the ultrasonic signal generated at the first wall may be higher than the amplitude of the ultrasonic signal received at the first wall after travelling back and forth through the fuel. The ultrasonic sensor may estimate an amplitude difference between the generated ultrasonic signal and the reflected ultrasonic signal to infer an attenuation coefficient of the ultrasonic signal. The damping coefficient may also depend on the material of the fuel tank. The level of attenuation of the ultrasonic signal in the fuel may vary based on the material of the fuel tank wall where the signal is reflected. As an example, certain materials (such as metals) may absorb a portion of a signal when the signal is reflected off a wall. Also, the level of attenuation may be based on the thickness of the wall from which the signal is reflected. The controller may determine an attenuation coefficient of the ultrasonic signal in the fuel using a look-up table calibrated based on the material and thickness of the fuel tank wall, with one or more of an amplitude difference of the signal, a distance between the first wall and the second wall, and a travel time of the ultrasonic signal to and from the second wall as inputs and the attenuation coefficient as an output. The attenuation coefficient may be a function of the viscosity of the fuel and may be based on the fuel ethanol content.

At 1618, the temperature of the fuel in the fuel tank may be estimated based on input from a fuel temperature sensor coupled to the fuel tank (such as temperature sensor 243 in fig. 2). At 1620, the fuel ethanol content (volume fraction) may be estimated based on the speed of sound in the fuel, the temperature of the fuel, and the attenuation coefficient in the fuel. Further, the fuel ethanol content may also be based on the fuel pressure, however, the fuel pressure may remain substantially constant during and among the measurements.

At 1622, engine operation may be adjusted based on the estimated fuel ethanol content. The adjusted engine operating parameters may include an amount of fuel injected, spark timing, and/or fuel injection timing based on the current fuel ethanol content. For example, if the ethanol percentage is increased, spark timing may be advanced due to higher activation energy of ethanol compared to gasoline and thus longer ignition timing of ethanol. As another example, the amount of fuel injected at cold start may be increased in response to an increase in ethanol content such that enough fuel is vaporized to start the engine. As another example, the amount (mass) of fuel injected may increase in response to an increase in ethanol content due to a decrease in the stoichiometric air-fuel ratio of ethanol.

In this way, engine operation may be adjusted based on the estimated fuel ethanol content, which is estimated based on each of the fuel temperature, the speed of sound in the fuel, and the attenuation coefficient of the ultrasonic signal in the fuel.

FIG. 17 illustrates an example method 1700 that may be implemented to estimate a life of fuel in a fuel tank. In contrast to the method for fuel age estimation, this method may be used to determine the age of fuel in a fuel tank rather than a fuel rail, as described in FIG. 4. Because this method uses sensors housed in the fuel tank for fuel age estimation, this method may be used in systems that do not have a direct injector coupled to the fuel rail and/or may be practiced during engine operation when fuel is dispensed by a port injector.

At 1702, current vehicle and engine operating parameters may be determined. The parameters may include vehicle speed, torque demand, engine speed, engine temperature, and the like. The controller may estimate the amount of fuel supplied from the fuel tank to a fuel injector, such as port injector 262 in FIG. 1.

At 1704, the routine includes determining whether the conditions for the fuel life determination are met. The condition may include a first threshold duration of vehicle operation using motor torque (fuel not combusted). For example, if the vehicle is operating for 7 days without the engine running, the fuel life determination may be carried out at the immediately subsequent engine start. The condition may also include a second threshold duration of time elapsed since a previous fuel life estimate. For example, such estimation may be carried out periodically after every 15 days. Also, the condition may include a third threshold duration during which less than a threshold amount of fuel is consumed. If it is determined that the conditions for the fuel life determination are not met, then the current engine operation may continue without a fuel life determination at 1706. Engine operation may include supplying fuel to one or more fuel injectors via one or more fuel rails.

If it is determined that the conditions for the fuel life determination are met, a fuel tank ultrasonic signal generator (such as ultrasonic signal generator 240 in FIG. 2) coupled to the interior of the fuel tank (coupled to the first tank wall) may be activated at 1608. The ultrasonic signal generator may generate an ultrasonic signal that may travel through the fuel from a first wall of the fuel tank (where the generator is positioned) to an opposing second wall of the fuel tank. The ultrasonic signal generator may reflect from the second wall of the tank and may return to the first wall. The reflected ultrasonic signal may be received at an ultrasonic sensor (such as ultrasonic sensor 241 in fig. 2) coupled to the first wall adjacent to the ultrasonic signal generator.

At 1710, a travel time of the reflected ultrasonic signal from the second fuel tank wall may be estimated. As an example, the timer may be set when the generator located at the first wall first generates an ultrasonic signal, and the timer may be stopped when the reflected ultrasonic signal (from the second wall) returns as detected by the ultrasonic sensor proximally coupled to the generator. The duration of time elapsed between the start and stop of the timer may be the travel time of the ultrasonic signal to and from the second wall.

At 1712, a speed of sound in the fuel may be estimated based on the estimated travel time. The distance between the first wall and the second wall may be retrieved from the controller memory. The speed of sound in the fuel may be estimated from the distance between the first wall and the second wall and the estimated travel time of the ultrasonic signal.

At 1716, attenuation of the ultrasonic signal in the fuel may be estimated. The ultrasonic signal may be attenuated as it travels through the fuel between the first wall and the second wall. The ultrasonic sensor may estimate an amplitude difference between the generated ultrasonic signal and the reflected ultrasonic signal to infer an attenuation coefficient of the ultrasonic signal. The damping constant may also depend on the material of the fuel tank. The level of attenuation of the ultrasonic signal in the fuel may vary based on the material of the fuel tank wall where the signal is reflected. As an example, certain materials (such as metals) may absorb a portion of a signal when the signal is reflected off a wall. Also, the level of attenuation may be based on the thickness of the wall from which the signal is reflected. The controller may determine an attenuation coefficient of the ultrasonic signal in the fuel using a look-up table calibrated based on the material and thickness of the fuel tank wall, with one or more of an amplitude difference of the signal, a distance between the first wall and the second wall, and a travel time of the ultrasonic signal to and from the second wall as inputs and the attenuation coefficient as an output. The decay factor may be a function of the viscosity of the fuel and may be based on the fuel age.

At 1718, the temperature of the fuel in the fuel tank may be estimated based on input from a fuel temperature sensor coupled to the fuel tank (such as temperature sensor 243 in fig. 2). At 1720, a fuel age indicating a concentration of lighter and heavier portions of gasoline may be estimated based on each of the estimated speed of sound in the fuel, a attenuation coefficient in the fuel, and a fuel temperature.

At 1722, engine operation may be adjusted based on the estimated fuel age. The adjusted engine operating parameters may include the amount of fuel injected, spark timing, and/or fuel injection timing based on the detected change in fuel composition. For example, the aged fuel may have a higher concentration of the heavier, less volatile portion of gasoline, and thus a greater amount of fuel may be injected during a cold start.

At 1724, the routine includes determining whether the fuel life is above a threshold life. The threshold age may be based on an increase in the concentration of heavier portions of the fuel that may be ineffective. The threshold may be pre-calibrated to be below a fuel age at which the fuel may become ineffective, so that the aging fuel may be used up before the fuel degrades.

If it is determined that the fuel life is above the threshold life, the operator may be notified via a dashboard indication that fuel needs to be depleted within a threshold time at 1726. The threshold time may be based on a fuel age over which the fuel will become ineffective. In one example, on a hybrid vehicle, the controller may increase the contribution of the engine to the total power demand to consume the remaining fuel before it becomes ineffective. In another example, the operator may refuel (add new fuel) so that older (aged) fuel may be diluted, thereby reducing the effect of the aged fuel. If it is determined that the fuel age is below the threshold age, it may be inferred that fuel may continue to be used for engine operation. At 1728, the current fuel may be indicated as being suitable for combustion.

In this manner, an ultrasonic signal may be generated via an ultrasonic signal generator positioned on a first wall of the fuel tank, a reflected ultrasonic signal reflected from a second opposing wall of the fuel tank may be received via an ultrasonic sensor, a sound speed in the fuel contained in the fuel tank and an attenuation coefficient of the ultrasonic signal in the fuel may be estimated based on the generated signal and the reflected signal, an ethanol percentage in the fuel or a lifetime of the fuel may be estimated based on the estimated sound speed in the fuel, the estimated attenuation coefficient of the ultrasonic signal in the fuel, and a fuel temperature, and engine operation may be adjusted based on the estimated ethanol percentage in the fuel or the lifetime of the fuel.

FIG. 14 shows an exemplary timeline 1400 illustrating the use of fuel rail pressure to determine fuel ethanol content in an alcohol containing fuel (flex fuel) in gasoline. In one example, fuel ethanol content estimation may be performed on a vehicle engine, such as a flexible fuel engine. The horizontal line (x-axis) represents time, while the vertical markers t 1-t 4 identify a significant amount of time in the routine for fuel ethanol content and fuel age determination.

A first plot, line 1402, illustrates a change in fuel rail temperature as estimated via a fuel rail temperature sensor (such as the temperature sensor 232 in fig. 2) coupled to a fuel rail (such as the fuel rail 250 in fig. 2). A second plot, line 1404, shows the change in fuel rail pressure as measured via a fuel rail pressure sensor (such as pressure sensor 248 in fig. 2) coupled to the fuel rail. The third plot, line 1406, shows a fuel direct injection pulse. At each pulse, fuel is delivered from the fuel rail to the combustion chamber via a direct injector (such as direct injector 252 in fig. 2). The fourth plot, line 1410, shows a refueling event as fuel is dispensed at a refueling station to the fuel tank via an external nozzle. The fifth plot, line 1412, shows an ethanol content estimation event. The sixth plot, line 1416, shows spark timing relative to Maximum Brake Torque (MBT) timing.

Prior to time t1, fuel is injected via direct injection and the pump is operated to deliver fuel from the fuel tank to the fuel rail for injection. The fuel rail pressure fluctuates based on the fuel injection event. Spark timing is adjusted based on engine operating conditions. At this point, no fuel ethanol content is implemented. At time t1, a refueling event is initiated and fuel is dispensed into the fuel tank from an external source. Between times t1 and t2, during a fuel refill, fuel is not injected into the combustion chamber because the vehicle is not being propelled. As the newly added fuel mixes with the existing fuel in the fuel tank, the ethanol content of the mixed fuel may change.

At time t2, the fueling is completed and engine operation is resumed. Between times t2 and t3, fuel is pumped from the fuel tank to the fuel rail and injected into the combustion chamber via the fuel injector. At time t3, the ethanol content estimation is initiated and the fuel rail pressure change during the fuel injection is recorded. The fuel rail pressure change is a fuel rail pressure difference before and after fuel injection. Each of a resonance frequency of a pressure pulsation in the fuel rail immediately after fuel injection and a damping coefficient of the pressure pulsation in the fuel rail is estimated. The fuel ethanol content is estimated from three or more of a fuel rail temperature, a fuel rail pressure change, a resonant frequency of a pressure pulsation in the fuel rail, and a damping coefficient of the pressure pulsation. The fuel ethanol content estimation is completed at time t 4. As seen from dashed line 1413, it is confirmed after ethanol content estimation that the fuel ethanol content has increased (between times t1 and t 2) after the fueling event. The activation energy of ethanol is higher compared to gasoline, so higher ethanol content will require longer ignition periods. Thus, in response to the increased fuel ethanol content, after time t4, the engine is operated with spark timing advanced to MBT. Engine efficiency is improved due to the advanced spark timing.

FIG. 15 shows an exemplary timeline 1500 illustrating determination of fuel life based on fuel rail pressure. The horizontal line (x-axis) represents time, while the vertical markers t 1-t 3 identify a significant amount of time in the routine for fuel life determination. In one example, fuel life estimation may be performed in a vehicle that uses gasoline as a fuel. In another example, fuel life estimation may be performed for a flexible fuel vehicle, where the ethanol content of the fuel is known.

The first plot, line 1502, shows the change in engine speed as estimated via the crankshaft sensor. A second plot, line 1504, shows the fuel rail temperature as estimated via a fuel rail temperature sensor (such as temperature sensor 232 in fig. 2) coupled to the fuel rail (such as fuel rail 250 in fig. 2). The third plot, line 1506, shows the fuel rail pressure change as measured via a fuel rail pressure sensor (such as pressure sensor 248 in fig. 2) coupled to the fuel rail. The fourth plot, line 1508, shows a fuel direct injection pulse. At each pulse, fuel is delivered from the fuel rail to the combustion chamber via a direct injector (such as direct injector 252 in fig. 2). The fifth plot, line 1510, shows a fuel life estimation event. Dashed line 1511 shows the estimated fuel life. Dashed line 1512 shows a threshold fuel use period above which the operator is notified of an end of fuel. The threshold may be pre-calibrated to be below a fuel age at which the fuel may become ineffective, so that the aging fuel may be used up before the fuel degrades. The sixth plot, line 1514, shows spark timing relative to Maximum Brake Torque (MBT) timing.

Before time t1, the engine is not running while the vehicle is not being propelled via engine torque. Fuel injection and spark are disabled during engine shutdown. At time t1, the engine is started from a stationary condition and fuel is injected into the engine cylinder via direct injection. The fuel rail pressure fluctuates based on the fuel injection event. Spark timing is adjusted based on engine operating conditions. No fuel life estimation is performed at this time.

At time t2, a threshold duration that has elapsed since a previous fuel life determination is inferred. Thus, at time t2, a fuel life estimation is initiated. Fuel age is estimated from two or more of fuel rail temperature, fuel rail pressure variation, resonant frequency of pressure pulsations in the fuel rail, and damping coefficient of pressure pulsations. The fuel life estimation is completed at time t 3. After the fuel life estimation, it is confirmed that the fuel life has increased. However, since the fuel life lasts below the threshold life 1512, the operator is not notified. In response to the increased fuel use period, after time t3, the engine is operated with spark timing advanced to MBT. Engine efficiency is improved due to the advanced spark timing.

In this way, fuel ethanol content or fuel age may be estimated based on fuel rail pressure, and engine operation, such as spark timing, may then be adjusted to improve fuel efficiency and engine performance.

FIG. 18 shows an exemplary timeline 1800 that illustrates a determination of fuel ethanol content based on ultrasonic signals. The horizontal line (x-axis) represents time, while the vertical markers t 1-t 4 identify a significant amount of time in the routine for fuel ethanol content determination.

A first plot, line 1802, shows a change in fuel temperature as estimated via a fuel temperature sensor (such as temperature sensor 243 in fig. 2) coupled inside the fuel tank. A second plot, line 1804, illustrates the generation of an ultrasound signal from an ultrasound signal generator (such as ultrasound signal generator 240 in fig. 2). An ultrasonic signal generator is coupled to a first wall of the fuel tank and the generated ultrasonic signal is reflected from a second opposing wall of the fuel tank. The reflected ultrasonic signal is recorded by an ultrasonic signal sensor (such as ultrasonic signal sensor 241 in fig. 2) coupled to the first wall at the proximal end of the ultrasonic signal generator. The third plot, line 1806, shows a refueling event as fuel is dispensed at a refueling station to the fuel tank via an external nozzle. The fourth plot, line 1808, shows an ethanol content estimation event. Dashed line 1809 shows the estimated fuel ethanol content during and after the ethanol content estimation event. The fifth plot, line 1812, shows spark timing relative to Maximum Brake Torque (MBT) timing.

Prior to time t1, the vehicle is propelled via engine torque, and spark timing is maintained at MBT. The fuel temperature changes depending on the engine operation, and fuel is not supplied to the fuel tank. No fuel ethanol content or fuel age estimation is performed at this time and the ultrasonic signal generator and sensor remain inactive. At time t1, a fueling event is initiated and fuel is dispensed into the fuel tank. Between times t1 and t2, during fueling, the engine is not running because the vehicle is not being propelled. As the newly added fuel mixes with the existing fuel in the fuel tank, the ethanol content of the mixed fuel may change.

At time t2, the fueling is completed and engine operation is resumed. Between times t2 and t3, fuel is injected into the combustion chamber via the fuel injector. At time t3, an estimation of the ethanol content of the fuel in the tank is initiated. To estimate fuel ethanol content, an ultrasonic signal generator is activated to generate an ultrasonic signal. The ultrasonic signal is detected by the ultrasonic sensor when reflected from the opposing wall of the fuel tank. The speed of sound in the fuel is estimated based on the ultrasonic signal by the travel time of the fuel to and from a first wall of the fuel tank and a second opposing wall of the fuel tank and the distance between the first wall and the second wall. The attenuation coefficient of the ultrasonic signal is estimated based on the change in the amplitude of the ultrasonic signal that reaches the ultrasonic signal sensor after reflection from the second wall. The fuel ethanol content is estimated based on the fuel temperature, the speed of sound in the fuel, and the attenuation coefficient in the ultrasonic signal in the fuel. The fuel ethanol content estimation is completed at time t 4. As seen from dashed line 1809, it is confirmed after the ethanol content estimation that the fuel ethanol content has decreased after the fueling event (between times t1 and t 2). As the ethanol content decreases, the spark timing is retarded by MBT between times t4 and t 5.

FIG. 19 shows an exemplary timeline 1900 illustrating determination of fuel life based on ultrasonic signals. The horizontal line (x-axis) represents time, while the vertical markers t 1-t 3 identify a significant amount of time in the routine for fuel life determination.

The first plot, line 1902, shows the engine speed variation as estimated via the crankshaft sensor. A second plot, line 1904, shows the fuel temperature variation as estimated via a fuel temperature sensor (such as temperature sensor 243 in fig. 2) coupled inside the fuel tank. The third plot, line 1906, shows the generation of an ultrasound signal from an ultrasound signal generator (such as ultrasound signal generator 240 in fig. 2). An ultrasonic signal generator is coupled to a first wall of the fuel tank and the generated ultrasonic signal is reflected from a second opposing wall of the fuel tank. The reflected ultrasonic signal is recorded by an ultrasonic signal sensor (such as ultrasonic signal sensor 241 in fig. 2) coupled to the first wall at the proximal end of the ultrasonic signal generator. The fourth plot, line 1908, shows a fuel life estimation event. Dashed line 1909 shows the estimated fuel life during and after the fuel life estimation event. Dashed line 1910 shows a threshold fuel use period above which the operator is notified to change fuel. The fifth plot, line 1912, shows spark timing relative to Maximum Brake Torque (MBT) timing.

Before time t1, the engine is not running while the vehicle is not being propelled via engine torque. Fuel injection and spark are disabled during engine shutdown. At time t1, the engine is started from a stationary condition and fuel is injected into the engine cylinder via direct injection. The fuel temperature changes based on engine operation, and fuel is not supplied to the fuel tank. No fuel life estimation is performed at this time and the ultrasonic signal generator and sensor remain inactive.

At time t2, a threshold duration that has elapsed since a previous fuel life determination is inferred. Thus, at time t2, a fuel life estimation is initiated. To estimate fuel life, an ultrasonic signal generator is activated to generate an ultrasonic signal. The ultrasonic signal is detected by the ultrasonic sensor when reflected from the opposing wall of the fuel tank. The speed of sound in the fuel is estimated based on the ultrasonic signal by the travel time of the fuel to and from a first wall of the fuel tank and a second opposing wall of the fuel tank and the distance between the first wall and the second wall. The attenuation coefficient of the ultrasonic signal is estimated based on the change in the amplitude of the ultrasonic signal that reaches the ultrasonic signal sensor after reflection from the second wall. The age of the fuel contained in the fuel tank is estimated based on each of the fuel temperature, the speed of sound in the fuel, and the attenuation coefficient of the ultrasonic signal in the fuel. The fuel life estimation is completed at time t 3.

After the fuel life estimation, it is confirmed that the fuel life has increased. However, since the fuel life continues to be below the threshold life 1910, the operator is not notified. In response to the increased fuel use period, after time t3, the engine is operated with spark timing advanced to MBT. Engine efficiency is improved due to the advanced spark timing.

In this way, fuel ethanol content or fuel age may be estimated based on reflections of ultrasonic signals inside the fuel tank, and engine operation, such as spark timing, may then be adjusted to improve fuel efficiency and engine performance.

An exemplary method for an engine includes: adjusting engine operation based on an estimated fuel age that is estimated based on at least two of a resonant frequency of a pressure pulsation after a fuel injection or pump stroke, a fuel rail pressure change, and a damping coefficient of the pressure pulsation in the fuel rail. In any of the preceding examples, the method further comprises: additionally or optionally, estimating a fuel ethanol content and/or a fuel water content based on each of a resonant frequency of the pressure pulsation, the fuel rail pressure variation, and a damping coefficient of the pressure pulsation; and adjusting engine operation based on the estimated fuel ethanol content and/or water content. In any or all of the preceding examples, the method further comprises: additionally or optionally, a fuel rail temperature is estimated from each of a resonant frequency of the pressure pulsations, the fuel rail pressure variations, and a damping coefficient of the pressure pulsations. In any or all of the preceding examples, additionally or optionally, the fuel ethanol content is a percentage of ethanol in fuel in the fuel tank of an engine of a flexible fuel vehicle and wherein the fuel water content is a percentage of water in fuel in the fuel rail. In any or all of the preceding examples, additionally or optionally, the fuel age is a function of a storage duration of fuel in the fuel tank and a temperature and pressure of the fuel in the tank, the fuel age indicating a change in fuel composition due to vaporization of a volatile component of the fuel. In any or all of the preceding examples, additionally or optionally, the fuel rail pressure change is a fuel rail pressure difference as estimated via a fuel rail pressure sensor coupled to the fuel rail before and after the pump stroke of the fuel injection or high pressure fuel pump via an injector coupled to the fuel rail. In any or all of the preceding examples, additionally or optionally, a resonant frequency of the pressure pulsation is estimated based on the pressure pulsation as estimated via the fuel rail pressure sensor coupled to the fuel rail immediately after the fuel injection or the pump stroke. In any or all of the preceding examples, additionally or optionally, the damping coefficient is estimated based on one or more of a fit of an exponential function to a decay profile or envelope of the pressure pulsation, a Prony analysis, and a fast fourier transform of the decay profile. In any or all of the preceding examples, additionally or optionally, the fuel ethanol content is periodically estimated for at least a first threshold travel distance and/or travel duration after a refueling event, and the fuel usage period is periodically estimated after completion of a second threshold travel distance and/or travel duration since an immediately previous fuel usage period estimation, the second threshold travel distance and/or travel duration being higher than the first threshold travel distance and/or travel duration. In any or all of the preceding examples, additionally or optionally, adjusting engine operation comprises: adjusting spark timing based on the estimated fuel ethanol content and/or the fuel age, the spark timing advancing to MBT in response to an increase in fuel ethanol content. In any or all of the preceding examples, additionally or optionally, adjusting engine operation further comprises: adjusting an amount of fuel injected during a cold start based on the estimated fuel ethanol content, fuel water content, and/or fuel age, the amount of fuel injected increasing during the cold start in response to an increase in the fuel ethanol and/or water content and an increase in fuel age. In any or all of the preceding examples, the method further comprises, additionally or alternatively, adjusting an injector pulse width during fuel injection based on the estimated fuel rail temperature. In any or all of the preceding examples, the method further comprises, additionally or optionally, notifying an operator to use/replace the fuel in response to one of a period of fuel usage increasing above a threshold period of usage and a water content of the fuel increasing above a threshold level.

Another exemplary engine method comprises: estimating volume fractions of ethanol and water in the fuel contained in the fuel tank based on each of the estimated fuel bulk modulus, the estimated fuel viscosity, and the sound velocity in the fuel during a first condition, and adjusting engine operation based on the estimated ethanol volume fraction, estimating a lifetime of the fuel contained in the fuel tank based on at least two of the estimated fuel bulk modulus, the estimated fuel viscosity, and the sound velocity in the fuel during a second condition, and adjusting engine operation based on the lifetime of the fuel; and during each of the first and second conditions, estimating a fuel rail temperature based on the estimated volume fraction of ethanol in the fuel, the volume fraction of water in the fuel, or the age of the fuel, and one of the estimated bulk modulus of the fuel, the estimated viscosity of the fuel, and the speed of sound in the fuel. In any of the preceding examples, additionally or optionally, the first condition comprises completing a refueling event for the flexible fuel vehicle, and wherein the second condition comprises completing a threshold travel distance and/or travel duration since an immediately previous fuel life estimate. In any or all of the preceding examples, additionally or optionally, the fuel bulk modulus is a function of a change in pressure after a fuel pump stroke or injection event, wherein the fuel viscosity is a function of a damping coefficient of a pressure pulsation in a fuel rail immediately after the fuel pump stroke or injection event, and wherein a speed of sound in the fuel is a function of a resonant frequency of the pressure pulsation in the fuel rail. In any or all of the preceding examples, additionally or optionally, the adjusting engine operation based on the estimated ethanol volume fraction comprises: advancing spark timing to MBT in response to an increase in the volume fraction, and wherein the adjusting engine operation based on the age of the fuel comprises: the fuel injection amount during the cold start is increased in response to an increase in the fuel age.

Yet another exemplary engine system includes: a controller having computer readable instructions stored on a non-transitory memory that, when executed, cause the controller to: upon completion of a fuel refill event, estimating a fuel ethanol content based on a fuel rail pressure factor and adjusting one or more of an amount of fuel injected and spark timing based on the estimated fuel ethanol content; and upon completion of a threshold duration since an immediately preceding fuel age estimation, estimating a fuel age based on the fuel rail pressure factor and adjusting one or more of an amount of fuel injected, a fuel injection timing, and a spark timing based on the estimated fuel age. In any preceding example, additionally or optionally, the fuel rail pressure factor comprises: a change in fuel rail pressure in response to a stroke or injection event of a fuel pump, a damping coefficient for a pressure pulsation in the fuel rail immediately after the stroke or injection event, and a resonant frequency of the pressure pulsation in the fuel rail immediately after the stroke or injection event. In any or all of the preceding examples, additionally or optionally, the fuel rail is one of a direct injector rail and a port injector rail, the fuel rail including a fuel rail pressure sensor.

It should be noted that the exemplary control and estimation routines included herein may be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in a non-transitory memory and may be carried out by a control system, including a controller, in conjunction with various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various acts, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described acts, operations, and/or functions may graphically represent code to be programmed into the non-transitory memory of the computer readable storage medium in the engine control system, wherein the described acts are carried out by executing instructions in conjunction with the electronic controller in the system including the various engine hardware components.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above techniques may be applied to V6 cylinders, inline 4 cylinders, inline 6 cylinders, V12 cylinders, opposed 4 cylinders, and other engine types. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

As used herein, unless otherwise specified, the term "about" is to be interpreted to mean ± 5% of the range.

The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.

According to the invention, a method for an engine is provided, having: adjusting engine operation based on an estimated fuel age that is estimated based on at least two of a resonant frequency of a pressure pulsation after a fuel injection or pump stroke, a fuel rail pressure change, and a damping coefficient of the pressure pulsation in the fuel rail.

According to an embodiment, the invention is further characterized by estimating a fuel ethanol content and/or a fuel water content based on each of a resonant frequency of the pressure pulsation, the fuel rail pressure variation, and a damping coefficient of the pressure pulsation; and adjusting engine operation based on the estimated fuel ethanol content and/or water content.

According to an embodiment, the invention is further characterized by estimating a fuel rail temperature from each of a resonant frequency of the pressure pulsation, the fuel rail pressure variation, and a damping coefficient of the pressure pulsation.

According to an embodiment, the fuel ethanol content is a percentage of ethanol in fuel in the fuel tank of an engine of a flexible fuel vehicle and wherein the fuel water content is a percentage of water in fuel in the fuel rail.

According to an embodiment, the fuel lifetime is a function of the duration of storage of the fuel in the fuel tank and the temperature and pressure of the fuel in the tank; the fuel age indicates a change in fuel composition due to vaporization of a volatile component of the fuel.

According to an embodiment, the fuel rail pressure variation is a fuel rail pressure difference as estimated via a fuel rail pressure sensor coupled to the fuel rail before and after the pump stroke of the fuel injection or high pressure fuel pump via an injector coupled to the fuel rail.

According to an embodiment, the resonance frequency of the pressure pulsation is estimated based on the pressure pulsation as estimated via a fuel rail pressure sensor coupled to the fuel rail immediately after the fuel injection or the pump stroke.

According to an embodiment, the damping coefficient is estimated based on one or more of fitting of an exponential function to a decay profile or envelope of the pressure pulsation, Prony analysis, and a fast fourier transform of the decay profile.

According to an embodiment, the fuel ethanol content is periodically estimated at least for a first threshold travel distance and/or travel duration after a refueling event, and the fuel usage period is periodically estimated after completion of a second threshold travel distance and/or travel duration since an immediately preceding fuel usage period estimation, the second threshold travel distance and/or travel duration being higher than the first threshold travel distance and/or travel duration.

According to one embodiment, adjusting engine operation comprises: adjusting spark timing based on the estimated fuel ethanol content and/or the fuel age, the spark timing advancing to MBT in response to an increase in fuel ethanol content.

According to an embodiment, adjusting engine operation further comprises: adjusting an amount of fuel injected during a cold start based on the estimated fuel ethanol content, fuel water content, and/or fuel age, the amount of fuel injected increasing during the cold start in response to an increase in the fuel ethanol and/or water content and an increase in fuel age.

According to an embodiment, the invention is further characterized by adjusting injector pulse width during fuel injection based on the estimated fuel rail temperature.

According to one embodiment, the invention is further characterized by: in response to the fuel life increasing above a threshold life and the water content of the fuel increasing above a threshold level, an operator is notified to use/replace the fuel.

According to the present invention, there is provided an engine method having: estimating volume fractions of ethanol and water in the fuel contained in the fuel tank based on each of the estimated fuel bulk modulus, the estimated fuel viscosity, and the sound velocity in the fuel during a first condition, and adjusting engine operation based on the estimated ethanol volume fraction, estimating a lifetime of the fuel contained in the fuel tank based on at least two of the estimated fuel bulk modulus, the estimated fuel viscosity, and the sound velocity in the fuel during a second condition, and adjusting engine operation based on the lifetime of the fuel; and during each of the first and second conditions, estimating a fuel rail temperature based on the estimated volume fraction of ethanol in the fuel, the volume fraction of water in the fuel, or the age of the fuel, and one of the estimated bulk modulus of the fuel, the estimated viscosity of the fuel, and the speed of sound in the fuel.

According to an embodiment, the first condition comprises completion of a refueling event for a flexible fuel vehicle, and wherein the second condition comprises completion of a threshold travel distance and/or travel duration since an immediately preceding fuel life estimate.

According to an embodiment, the fuel bulk modulus is a function of a pressure change after a fuel pump stroke or injection event, wherein the fuel viscosity is a function of a damping coefficient of a pressure pulsation in a fuel rail immediately after the fuel pump stroke or injection event, and wherein a speed of sound in the fuel is a function of a resonant frequency of the pressure pulsation in the fuel rail.

According to an embodiment, said adjusting engine operation based on estimated ethanol volume fraction comprises: advancing spark timing to MBT in response to an increase in the volume fraction, and wherein the adjusting engine operation based on the age of the fuel comprises: the fuel injection amount during the cold start is increased in response to an increase in the fuel age.

According to the present invention, there is provided an engine system having: a controller having computer readable instructions stored on a non-transitory memory that, when executed, cause the controller to: upon completion of a fuel refill event, estimating a fuel ethanol content based on a fuel rail pressure factor and adjusting one or more of an amount of fuel injected and spark timing based on the estimated fuel ethanol content; and upon completion of a threshold duration since an immediately preceding fuel age estimation, estimating a fuel age based on the fuel rail pressure factor and adjusting one or more of an amount of fuel injected, a fuel injection timing, and a spark timing based on the estimated fuel age.

According to an embodiment, the fuel rail pressure factor comprises: a change in fuel rail pressure in response to a stroke or injection event of a fuel pump, a damping coefficient for a pressure pulsation in the fuel rail immediately after the stroke or injection event, and a resonant frequency of the pressure pulsation in the fuel rail immediately after the stroke or injection event.

According to an embodiment, the fuel rail is one of a direct injector rail and a port injector rail, the fuel rail comprising a fuel rail pressure sensor.