阅读说明：本技术 双燃料燃烧强度 (Dual fuel combustion intensity ) 是由 J·巴塔 G·J·汉普森 S·奈尔 J·卡尔森 于 2018-05-04 设计创作，主要内容包括：一种检测内燃发动机中非受控的燃烧的方法,包括：对缸内压力传感器进行采样,该传感器被配置为测量发动机气缸中的压力并生成压力信号；基于该压力信号计算燃烧强度指标；确定参数,该参数基于燃烧强度指标描述发动机接近非受控的燃烧状况的程度；以及基于参数和燃烧强度指标的一个或多个来控制第一燃料和第二燃料的置换率。(A method of detecting uncontrolled combustion in an internal combustion engine, comprising: sampling an in-cylinder pressure sensor configured to measure pressure in an engine cylinder and generate a pressure signal; calculating a combustion intensity indicator based on the pressure signal; determining a parameter describing a degree to which the engine is approaching an uncontrolled combustion condition based on the combustion intensity indicator; and controlling the rate of substitution of the first fuel and the second fuel based on one or more of the parameter and the combustion intensity indicator.)

1. A method of detecting uncontrolled combustion in an internal combustion engine, the method comprising:

sampling a pressure signal from an in-cylinder pressure sensor, the pressure signal representing a measured pressure in a cylinder of an engine;

calculating a combustion intensity indicator based on the pressure signal, wherein the combustion intensity indicator is indicative of the engine approaching an uncontrolled combustion state;

determining engine control parameters according to the combustion intensity index; and

controlling the engine based on the engine control parameter.

2. The method of claim 1, wherein the internal combustion engine comprises a dual fuel internal combustion engine, and wherein the engine control parameter comprises a rate of substitution of a first fuel and a second fuel based on at least one of the parameter or the combustion intensity indicator.

3. The method of claim 2, wherein the first fuel is diesel and wherein the second fuel is natural gas.

4. The method of claim 1, wherein the combustion intensity indicator is calculated over the same combustion period as the sampling of the in-cylinder pressure sensor.

5. The method of claim 1, comprising:

calculating a pressure indicator, a heat release indicator and a knock indicator based on the pressure signal;

wherein the combustion intensity indicator is a function of the pressure indicator, the heat release indicator, and the knock indicator.

6. The method of claim 5, wherein the heat release indicator comprises an adiabatic heat release rate of combustion in a cylinder of the engine.

7. The method of claim 1, comprising: calculating at least one of the following combustion indicators based on the pressure signal:

peak cylinder pressure;

crank angle of peak cylinder pressure;

a rate of cylinder pressure rise;

cylinder pressure pulsation;

crank angle of cylinder pressure pulsation;

a duration of combustion;

the heat release slope;

crank angle of heat release centroid; or

Crank angle for maximum heat release rate.

8. The method of claim 7, wherein the combustion intensity indicator is a function of at least one of:

the peak cylinder pressure;

a crank angle of the peak cylinder pressure;

the rate of cylinder pressure rise;

the cylinder pressure pulses;

a crank angle of the cylinder pressure pulsation;

the duration of combustion;

the heat release slope;

a crank angle of the heat release centroid; or

Crank angle of the maximum heat release rate.

9. The method of claim 8, wherein the combustion intensity indicator is a function of at least peak pressure, rate of pressure rise, pressure pulsation, combustion duration, and heat release slope.

10. The method of claim 1, comprising: determining a fuel input signal, a throttle position signal, and an ignition timing signal for the engine based on at least one of the combustion intensity indicator or the parameter.

11. A controller for controlling operation of a dual-fuel internal combustion engine of an engine system, the engine system including a pressure sensor configured to measure pressure in a cylinder of the engine and generate a corresponding pressure signal and a crank angle sensor configured to measure crank angle of the engine and generate a corresponding crank angle signal, the controller comprising:

a processor coupleable with an internal pressure sensor and the crank angle sensor; and

at least one non-transitory computer-readable medium storing instructions operable to cause the processor of the controller to perform operations comprising:

(a) sampling the pressure signal;

(b) calculating a combustion intensity indicator based on the pressure signal, wherein the combustion intensity indicator is indicative of the engine approaching an uncontrolled combustion state;

(c) determining a rate of substitution of the first and second fuels delivered to the cylinder based on the combustion intensity indicator; and

(d) controlling the dual-fuel internal combustion engine based on the substitution rate.

12. The controller of claim 11, wherein the first fuel is diesel and wherein the second fuel is natural gas.

13. The controller of claim 11, wherein steps (b) and (c) occur in a next cycle of the cylinder.

14. The controller of claim 11, wherein the instructions include calculating a pressure indicator, a heat release indicator, and a knock indicator based on the pressure signal, and wherein the combustion intensity indicator is a function of the pressure indicator, the heat release indicator, and the knock indicator.

15. The controller of claim 11, wherein calculating a heat release indicator comprises: an adiabatic heat release rate of combustion in the cylinder of the engine is calculated.

16. The controller of claim 11, wherein the instructions include calculating at least one of the following combustion indicators based on the pressure signal:

peak cylinder pressure;

crank angle of peak cylinder pressure;

a rate of pressure rise;

pressure pulsation;

the location of the cylinder pressure pulsations;

a duration of combustion;

the heat release slope;

crank angle of heat release centroid; or

Crank angle for maximum heat release rate.

17. The controller of claim 16, wherein the combustion intensity indicator is a function of at least one of:

the peak cylinder pressure;

a crank angle of the peak cylinder pressure;

the rate of cylinder pressure rise;

the cylinder pressure pulses;

a pulsating crank angle;

the duration of combustion;

the heat release slope;

a crank angle of the heat release centroid; or

Crank angle of the maximum heat release rate.

18. The controller of claim 16 wherein the combustion intensity indicator is a function of at least a peak pressure, the rate of pressure rise, the pressure pulsation, the combustion duration, and the heat release slope.

19. The controller of claim 11, wherein the instructions comprise:

determining, based on at least one of the combustion intensity indicators or parameters, at least one of: a fuel input signal, a throttle position signal, or an ignition timing signal of the dual-fuel internal combustion engine, an

Controlling the dual-fuel internal combustion engine using at least one of: the fuel input signal, the throttle position signal, or the spark timing signal.

20. A controller for controlling operation of an internal combustion engine of an engine system, the engine system including a pressure sensor configured to measure pressure in a cylinder of the engine and generate a corresponding pressure signal and a crank angle sensor configured to measure crank angle of the engine and generate a corresponding crank angle signal, the controller comprising:

a processor coupleable with an internal pressure sensor and the crank angle sensor; and

at least one non-transitory computer-readable medium storing instructions operable to cause the processor of the controller to perform operations comprising:

(a) sampling the pressure signal;

(b) calculating a combustion intensity indicator based on the pressure signal, wherein the combustion intensity indicator is indicative of the engine approaching an uncontrolled combustion state;

(c) determining engine control parameters according to the combustion intensity index; and

(d) controlling the engine based on the engine control parameter.

Background

Uncontrolled destructive combustion, such as engine knock, typically produces a rapid rate of pressure rise after high frequency pressure oscillations, in which combustion a large amount of energy is released over a short period of time, typically due to rapid combustion of the exhaust. These intense pressure waves can place high stresses on engine structural components and significantly increase heat transfer rates, ultimately leading to engine failure. Such uncontrolled combustion may occur for various reasons, such as poor fuel quality and characteristics, heterogeneity of fuel-air mixtures, hot spots in the combustion chamber, deposits, evaporated lubrication oil, unfavorable pressure-time history in the unburned cylinder charge gas, periodic variations in the cylinder or charge, insufficient cooling, and the like. The prediction of abnormal combustion is generally very difficult and is usually addressed during engine design.

Disclosure of Invention

The concepts herein contemplate the inclusion of at least one in-cylinder pressure sensor on the engine and, simultaneously with and in some cases in real time with the operation of the engine, calculating the following combustion indicators: peak pressure, rate of pressure rise, pressure pulsation, duration of combustion, and rate of heat release change. These metrics are then mathematically combined by an equation/algorithm to determine how close the engine is operating to uncontrolled combustion. This allows the engine to achieve harsher operating conditions, such as richer mixture or higher substitution rates in dual fuel operation, while maintaining safe operation. In some cases, the engine is a 2-stroke or 4-stroke engine, and in some cases, real-time refers to calculating the combustion indicator during the same cycle (e.g., before the next intake), before the next stroke is completed, or during the same stroke.

In some embodiments, contemplated herein include the ability to collect and process in-cylinder pressure information on a periodic basis and the following algorithm:

peak pressure-maximum combustion pressure during one event;

rate of pressure rise-maximum rate of pressure rise during combustion;

sum of pressure pulsations-increase P;

duration of combustion-crank angle between CAx1 and CAx 2;

heat release variation-a determinant of the first half of the combustion process as compared to the second half of the combustion process;

some aspects of the present disclosure include using the combustion indicators listed above to determine a combustion intensity value that can then be used in a control loop to safely drive the engine to a maximum gas substitution rate. In some embodiments, all of these criteria are necessary in order to cover many different situations that can be seen on a dual fuel engine. In some cases, the heat release change is determined statically or dynamically in order to accurately determine the inflection point of combustion acceleration.

In certain aspects of the present disclosure, uncontrolled combustion (detonation) is no longer considered from the traditional time-based frequency domain, but rather from low speed direct in-cylinder pressure information based on actual engine limits.

One example of the present disclosure is a method of detecting uncontrolled combustion in an internal combustion engine. The method comprises the following steps: sampling an in-cylinder pressure sensor configured to measure a pressure in a cylinder of an engine and generate a corresponding pressure signal; calculating a combustion intensity indicator based on the corresponding pressure signal; and determining a parameter describing the proximity of the engine to the uncontrolled combustion condition based on the combustion intensity indicator.

Another example is a dual fuel internal combustion engine that includes an in-cylinder pressure sensor configured to measure a pressure in an engine cylinder and generate a corresponding pressure signal, a crank angle sensor configured to measure a crank angle and generate a corresponding crank angle signal, and an engine control unit coupleable with the pressure sensor and the crank angle sensor. The engine control unit is configured to: sampling the pressure signals, calculating a combustion intensity indicator based on the corresponding pressure signals, determining a parameter describing the degree to which the engine is approaching an uncontrolled combustion condition; and controlling a rate of replacement of the first and second fuels delivered to the cylinder based on one or more of the parameter and the combustion intensity indicator.

Another example is a method of detecting uncontrolled combustion in an internal combustion engine. The method comprises the following steps: sampling a pressure signal from an in-cylinder pressure sensor, the pressure signal representing a measured pressure in a cylinder of the engine; calculating a combustion intensity indicator based on the pressure signal, wherein the combustion intensity indicator is indicative of the engine approaching an uncontrolled combustion state; determining engine control parameters according to the combustion intensity index; and controlling the engine based on the engine control parameter.

In some cases, the internal combustion engine comprises a dual-fuel internal combustion engine, and the engine control parameter comprises a rate of replacement of the first fuel and the second fuel based on at least one of the parameter or the combustion intensity indicator.

In some cases, the first fuel is diesel, and wherein the second fuel is natural gas.

In some cases, the combustion intensity indicator is calculated during the same combustion cycle as the sampling of the in-cylinder pressure sensor.

In some cases, the method includes calculating a pressure indicator, a heat release indicator, and a knock indicator based on the pressure signal, wherein the combustion intensity indicator is a function of the pressure indicator, the heat release indicator, and the knock indicator. In some cases, the heat release indicator includes an adiabatic heat release rate of combustion in the engine cylinder.

In some cases, the method includes calculating at least one of the following combustion indicators based on the pressure signal: peak cylinder pressure, crank angle of peak cylinder pressure, rate of cylinder pressure rise, cylinder pressure pulsation, crank angle of cylinder pressure pulsation, combustion duration, heat release slope, crank angle of heat release centroid, or crank angle of maximum heat release rate.

In some cases, the combustion intensity indicator is a function of at least one of: peak cylinder pressure, crank angle of peak cylinder pressure, rate of cylinder pressure rise, cylinder pressure pulsation, crank angle of cylinder pulsation, combustion duration, heat release slope, crank angle of heat release centroid, or crank angle of maximum heat release rate.

In some cases, the combustion intensity indicator is a function of at least peak pressure, rate of pressure rise, pressure pulsations, combustion duration, and heat release slope.

In some cases, the method comprises: a fuel input signal, a throttle position signal, and an ignition timing signal of the engine are determined based on at least one of the combustion intensity indicators or parameters.

Yet another example is a controller that controls operation of a dual-fuel internal combustion engine of an engine system, wherein the engine system includes a pressure sensor configured to measure pressure in a cylinder of the engine and generate a corresponding pressure signal and a crank angle sensor configured to measure crank angle of the engine and generate a corresponding crank angle signal. The controller includes a processor coupleable with the internal pressure sensor and the crank angle sensor, and at least one non-transitory computer readable medium storing instructions operable to cause the processor of the controller to perform operations. Wherein the various operations include: (a) sampling the pressure signal; (b) calculating a combustion intensity indicator based on the pressure signal, wherein the combustion intensity indicator is indicative of the engine approaching an uncontrolled combustion state; (c) determining a rate of replacement of the first fuel and the second fuel delivered to the cylinder based on the combustion intensity indicator; and (d) controlling the dual-fuel internal combustion engine based on the substitution rate.

In some cases, the first fuel is diesel, and wherein the second fuel is natural gas.

In some cases, steps (b) and (c) occur during the next cycle of the cylinder.

In some cases, the instructions include calculating a pressure indicator, a heat release indicator, and a knock indicator based on the pressure signal, and wherein the combustion intensity indicator is a function of the pressure indicator, the heat release indicator, and the knock indicator.

In some cases, calculating the heat release indicator includes calculating an adiabatic heat release rate of combustion in the engine cylinder.

In some cases, the instructions include calculating at least one of the following combustion indicators based on the pressure signal: peak cylinder pressure, crank angle of peak cylinder pressure, rate of cylinder pressure rise, cylinder pressure pulsation, crank angle of cylinder pressure pulsation, combustion duration, heat release slope, crank angle of heat release centroid, or crank angle of maximum heat release rate.

In some cases: peak cylinder pressure, crank angle of peak cylinder pressure, rate of cylinder pressure rise, cylinder pressure pulsation, crank angle of cylinder pulsation, combustion duration, heat release slope, crank angle of heat release centroid, or crank angle of maximum heat release rate.

In some cases, the combustion intensity indicator is a function of at least peak pressure, rate of pressure rise, pressure pulsations, combustion duration, and heat release slope.

In some cases, the instructions include determining, based on at least one of the combustion intensity indicator or the parameter, at least one of: a fuel input signal, a throttle position signal, or an ignition timing signal of the dual-fuel internal combustion engine, and controlling the dual-fuel internal combustion engine using at least one of: a fuel input signal, a throttle position signal, or an ignition timing signal.

Yet another example is a controller for controlling operation of an internal combustion engine of an engine system, wherein the engine system includes a pressure sensor configured to measure pressure in a cylinder of the engine and generate a corresponding pressure signal, and a crank angle sensor configured to measure crank angle of the engine and generate a corresponding crank angle signal. The controller includes a processor coupleable with the internal pressure sensor and the crank angle sensor, and at least one non-transitory computer readable medium storing instructions operable to cause the processor of the controller to perform operations. The various operations include: (a) sampling the pressure signal; (b) calculating a combustion intensity indicator based on the pressure signal, wherein the combustion intensity indicator is indicative of the engine approaching an uncontrolled combustion state; (c) determining engine control parameters according to the combustion intensity index; and (d) controlling the engine based on the engine control parameter.

Some aspects of the present disclosure have the following advantages: reducing the risk of damaging the high substitution rate dual fuel engine. Since the combustion intensity indicator uses known mechanical engine limits, the calibration effort for detecting uncontrolled combustion is greatly reduced. Certain aspects also allow the engine to be controlled to operate at maximum substitution rate at all times without having to increase a safety margin, which provides a better value location for dual fuel engine operators.

Drawings

FIG. 1A is a schematic cross-sectional view of a cylinder of an internal combustion engine including an engine control system.

FIG. 1B is a schematic diagram of an engine control system.

FIG. 1C is a block diagram of an exemplary engine control system having a processor and memory.

FIG. 2 is a graph of the accelerometer detection effect processed as a function of gas displacement.

Fig. 3 is a graph of in-cylinder pressure and vibration trace at 0%, 60%, and 90% gas substitution rate.

FIG. 4 is a graph of vibration and pressure knock intensity versus gas displacement ratio.

FIG. 5A is a 2-dimensional contour plot of pressure knock intensity versus gas displacement at various velocities.

FIG. 5B is a 2-dimensional contour plot of vibration knock intensity versus gas displacement at various speeds.

FIG. 6 is a graph illustrating combustion intensity indicator effect versus a classical knock intensity indicator as an approximate measure of uncontrolled combustion and as a function of gas displacement.

FIG. 7 is a graph of the smooth heat release trace at 0%, 60% and 90% gas substitution.

FIG. 8 is a 2-dimensional contour plot of combustion intensity versus gas displacement at various speeds.

FIG. 9 is a graph of angular position of 10%, 50% and 90% total heat release versus gas displacement.

FIG. 10 is a graph of in-cylinder pressure versus crank angle at 0%, 60%, and 90% gas substitution.

FIG. 11 is a graph of smooth heat release trajectory versus crank angle at 0%, 60%, and 90% gas substitution.

Fig. 12 is a graph of the combustion intensity and the knock intensity index as a function of the Gas Substitution Rate (GSR).

Fig. 13 is a graph of in-cylinder pressure traces at 0%, 10%, and 15% propane gas substitution rates (PSRs) at 80% GSR.

Fig. 14 is a graph of smooth exotherm traces at 0%, 10%, and 15% propane gas substitution (PSR) at 80% GSR.

Fig. 15 is a graph of combustion intensity and knock intensity index versus propane gas substitution rate (PSR) at 90% GSR.

FIG. 16 is a plot of combustion intensity and knock intensity indicator versus Manifold Air Temperature (MAT).

FIG. 17A is a graph of GSR and PSR versus time.

FIG. 17B is a graph of combustion intensity versus time during FIG. 17A, illustrating the effect of a sine wave GSR command with propane addition on the CI index response.

FIG. 18A is a graph of Manifold Air Temperature (MAT) versus time.

FIG. 18B is a graph of time versus combustion intensity of FIG. 18A, illustrating the effect of the MAT on the combustion intensity indicator response.

Fig. 19 is a flow chart of an exemplary aspect of the present disclosure.

Detailed Description

A new means of detecting uncontrolled combustion, Combustion Intensity (CI), is disclosed that monitors a mathematical combination of pressure and heat release indicators to accurately predict the onset of uncontrolled combustion. Data from spark ignition and dual fuel engines show the disadvantages of the traditional knock type, vibration frequency based approach, which works best under severe conditions where the burning rate of the extremely abrupt end gas is followed by high frequency oscillations. This technique is not satisfactory, particularly in dual fuel combustion where the signal is obscured by diesel combustion pulsations and in some modes where the frequency content falls below a normal detection threshold. In contrast, embodiments of the CI indicators described herein provide a monotonic trend as gas substitution increases at all operating points, even if gas mass, manifold air temperature, or other engine operating conditions change. This provides a defined control action path, which in some cases may be designed as a combustion intensity target. The Gas Substitution Rate (GSR) and the severity of the combustion intensity encountered by these phases may vary for different engine configurations, but the basic combustion phenomena disclosed herein should be generally relevant.

Bringing a gas engine to lean/low NOx and high BMEP limits, and a gas-diesel dual fuel engine to high displacement rates, typically results in sudden uncontrolled combustion that limits performance, such as knock. Knowing and detecting the progress of abnormal combustion is critical to protecting the engine. Aspects of the present disclosure include the ability to detect the progress of uncontrolled combustion using in-cylinder pressures of both spark-ignition and dual-fuel engines. For gas engines, pressure-based knock detection may capture all knock periods, while vibration-based knock detection may miss a significant proportion of the knock periods. For dual fuel engines, conventional frequency-based detection means can detect severe combustion events but cannot provide a good signal that continuously increases. This makes control and calibration of the engine very difficult and therefore typically drives to a lower rate of replacement in order to maintain a safety margin. This behavior is due to the diesel combustion process, which produces pressure pulsations in the cylinders.

Historically, the term "detonation" has been used broadly to denote any form of "uncontrolled combustion" which is generally associated with the phenomenon of "self-ignition" due to the compression and heating of the combustible gas mixture outside the flame front. Controlled combustion will be characterized as a regular progression of the burned mass fraction, which will be associated with the propagating flame. Traditional detonation occurs when the terminal gas in front of the flame self-ignites due to the pressure and temperature generated by the flame, but this does not occur in the flame. When auto-ignition occurs, it will transmit pressure waves over the cylinder, which are detected as high frequency pressure oscillations and potential vibration noise.

Uncontrolled combustion may be characterized by a discontinuous sudden increase in heat release rate, and this sudden increase in heat release rate will be manifested in the pressure trace shape, but it may or may not cause high frequency pressure oscillations. Unlike spark ignition engines, where the harshness of uncontrolled combustion may escalate from incipient to severe knock, providing sufficient time for control action, the onset of "uncontrolled combustion" for a dual fuel engine may be abrupt and non-monotonic. When such "uncontrolled combustion" occurs, high frequency oscillations are not always observed in the in-cylinder pressure or vibration-based knock sensor signal, and are typically not observed until late.

When the replacement rate increases beyond a certain point, it is found that the vibration knock signal decreases. If the engine relies on knocking to protect the engine from excessive gas substitution rates, varying gas quality, or other effects, a robust control system and incremental signal feedback are required to maximize the substitution while maintaining safe engine operation.

To achieve this, a new means of detecting uncontrolled combustion is described that monitors a mathematical combination of pressure and heat release indicators that accurately predicts the progress of uncontrolled combustion, thereby providing a deterministic control action path. By this means, the rate of replacement can be maximized and maintained at a desired safety margin on a diesel dual fuel engine.

Tests were conducted to vary the rate of displacement at various speeds and loads to indicate the different combustion modes seen in diesel dual fuel engines. This data was used to determine a better means of detecting uncontrolled combustion in a dual fuel engine, and thus the term Combustion Intensity (CI) was proposed. The combustion intensity indicator described herein provides a measure of continuous increase in combustion state to provide better controllability, while improving protection against uncontrolled combustion because it is based on direct monitoring of in-cylinder pressure simultaneously with the combustion cycle.

For dual fuel engines, as described above, conventional frequency-based sensing means can detect severe combustion events but cannot provide a continuously increasing good signal corresponding to harshness. This makes control and calibration of the engine very difficult, usually driven to a lower rate of replacement in order to maintain a safety margin. For low gas substitution rates, the diesel combustion process dominates as diesel auto-ignition creates pressure pulsations in the cylinder. As gas is added to the fresh charge, the intensity of the diesel ignition combustion increases and the gas amplifies the effect of the diesel-induced combustion. However, as the rate of displacement increases beyond a certain point, the vibration knock signal decreases as the mode of combustion transitions from "diesel" to "premixed gas", and the frequency-based content begins to decrease with additional gas displacement. If the engine relies on vibration-based knock sensors to protect the engine from excessive gas substitution rates, varying gas quality, or other effects, a robust control system and incremental signal feedback are required to maximize the substitution while maintaining safe engine operation. To address this problem, a new approach is needed to detect uncontrolled combustion in a dual fuel engine.

One exemplary approach described herein is to include at least one in-cylinder pressure sensor on the engine, and, simultaneously with and in some cases in real time with the operation of the engine, calculate the following combustion indicators: peak pressure, location of peak pressure, boost rate, pressure pulsations, location of pulsations, combustion duration and heat release slope, location of centroid of heat release rate, location of maximum heat release rate. In some cases, these indicators are then used together to determine how close the engine is operating to uncontrolled combustion. Based on this determination, it is possible to allow the engine to reach a higher replacement rate while maintaining safe operation.

Although the most demanding dual fuel gas/diesel combustion profile refers herein to adding gaseous fuel to an existing diesel engine, the reserve compression ratio, valve timing and piston are constant, and the method is applicable to all dual fuel gas/diesel engines including micro-pilot. The fuel gas, which is typically composed of natural gas, propane or biogas, may be introduced at a single location where it is fumigated into the intake system or injected through a port near the intake valve. In some cases, dual fuel will refer to the continuous addition of natural gas to the combustion chamber of a reserve diesel engine. As the gas substitution rate increases, the diesel will be "controlled" by decreasing the amount of diesel at an equal energy rate to maintain the target load.

Referring initially to FIG. 1A, an exemplary engine system 100 is illustrated that may employ aspects of the present disclosure. The engine system 100 includes an engine control unit 102, an air/fuel module 104, an ignition module 106, and an engine 101 (shown here as a reciprocating engine). Fig. 1A shows, for example, an internal combustion engine 100. For purposes of this disclosure, the engine system 100 will be described as a reciprocating piston engine powered by gaseous fuel. In some cases, the engine is operated using natural gas fuel. The engine may be any other type of internal combustion engine, referring both to the fuel type (gaseous, liquid (e.g., gasoline, diesel, and/or others), in-phase or mixed-phase multi-fuel, and/or other configurations) and to the physical configuration of the engine (reciprocating, Wankel rotary, and/or other configurations). Although the engine control unit 102, the air/fuel module 104, and the ignition module 106 are shown separately, the modules 102, 104, 106 may be combined into a single module or may be part of an engine controller having other inputs and outputs.

Reciprocating engine 101 includes an engine cylinder 108, a piston 110, an intake valve 112, and an exhaust valve 114. The engine 101 includes an engine block that includes one or more cylinders 108 (only one shown in fig. 1A). Engine 100 includes a combustion chamber 160 formed by cylinder 108, piston 110, and head 130. Spark plug 120 or a direct fuel injector or pre-chamber is positioned within cylinder head 130, which enables the ignition device to access the combustible mixture. In general, the term "spark plug" may refer to a direct fuel injection device within a pre-combustion chamber and/or a spark plug or other ignition device. In the case of a spark plug, the spark gap 122 of the spark plug 120 is located within the combustion chamber 160. In some cases, the spark gap 122 is an arrangement of two or more electrodes with a small space between them. When a current is applied to one of the electrodes, an arc is generated that bridges a small space (i.e., a spark gap) between the electrodes. Other types of igniters may be used, including laser igniters, hot surface igniters, and/or other types of igniters. A piston 110 within each cylinder 108 moves between a Top Dead Center (TDC) position and a Bottom Dead Center (BDC) position. Engine 100 includes a crankshaft 140, which crankshaft 140 connects each piston 110 such that piston 108 moves between TDC and BDC positions within each cylinder 108 and rotates crankshaft 140. The TDC position is the position of the piston 110 that gives the combustion chamber 160 the smallest volume (i.e., the piston 110 is closest to the top of the spark plug 120 and the combustion chamber 160), while the BDC position is the position of the piston 110 that gives the combustion chamber 160 the largest volume (i.e., the piston 110 is furthest retracted from the top of the spark plug 120 and the combustion chamber 160).

The cylinder head 130 defines an intake passage 131 and an exhaust passage 132. The intake passage 131 directs air or an air and fuel mixture from the intake manifold 116 into the combustion chamber 160. Exhaust passage 132 channels exhaust gases from combustion chamber 160 into exhaust manifold 118. The intake manifold 116 communicates with the cylinder 108 through an intake passage 131 and an intake valve 112. The exhaust manifold 118 receives exhaust gas from the cylinder 108 through an exhaust valve 114 and an exhaust passage 132. The intake and exhaust valves 112, 114 are controlled by valve actuation assemblies for each cylinder, which may include electronic, mechanical, hydraulic, or pneumatic control or control via a camshaft (not shown).

The movement of the piston 110 between the TDC and BDC positions within each cylinder 108 defines an intake stroke, a compression stroke, a combustion or power stroke, and an exhaust stroke. The intake stroke is the movement of the piston 110 away from the ignition plug 120 with the intake valve 112 open and the fuel/air mixture drawn into the combustion chamber 160 via the intake passage 131. The compression stroke is the movement of the piston 110 toward the spark plug 120 with the air/fuel mixture in the combustion chamber 160 and with both the intake valve 112 and the exhaust valve 114 closed, thereby enabling the movement of the piston 110 to compress the fuel/air mixture in the combustion chamber 160. The combustion or power stroke is the movement of the piston 110 away from the spark plug 120 that occurs after the combustion stroke when the spark plug 120 ignites the compressed fuel/air mixture in the combustion chamber by creating an arc in the spark gap 122. The ignited fuel/air mixture combusts and causes a rapid rise in pressure in combustion chamber 160, thereby imparting an expansive force to the movement of piston 110 away from spark plug 120. The exhaust stroke is the movement of the piston 110 toward the spark plug 120 after the combustion stroke, at which time the exhaust valve 114 opens to allow the piston 110 to exhaust combustion gases to the exhaust manifold 118 via the exhaust passage 118.

The engine 100 includes a fuel supply 124, such as a fuel injector, gas mixer, or other fuel supply, to direct fuel into the intake manifold 116 or directly into the combustion chamber 160. In some cases, engine 100 is a dual fuel engine having two fuel sources entering combustion chamber 160.

In some cases, the engine system 100 may include another type of internal combustion engine 101 that does not have pistons/cylinders, such as a Wankel engine (i.e., a rotor in a combustion chamber). In some cases, engine 101 includes two or more spark plugs 120 in each combustion chamber 160.

During engine operation, i.e., during a combustion event in the combustion chamber 160, the air/fuel module 104 provides fuel to the intake air flow in the intake manifold prior to entering the combustion chamber 160. The spark module 106 controls ignition of the air/fuel in the combustion chamber 160 by adjusting the timing of the creation of the arc and the spark gap 122, which initiates combustion of the fuel/air mixture within the combustion chamber 160 during a series of ignition events between each successive compression and combustion stroke of the piston 110. During each ignition event, the spark module 106 controls ignition timing and energizes a primary ignition coil of a spark plug 120. The air/fuel module 104 controls a fuel injection device 124 and may control a throttle 126 to deliver air and fuel to the engine cylinders 108 at a target ratio. The air/fuel module 104 receives feedback from the engine control module 102 and adjusts the air/fuel ratio. The spark module 106 controls the spark plug 120 by controlling operation of an ignition coil electrically coupled to the spark plug and supplied with current from a power source. In addition to the aspects of the present system disclosed below, the ECU 102 also regulates operation of the spark module 106 based on engine speed and load.

In some cases, the ECU 102 includes the spark module 106 and the fuel/air module 104 as integrated software algorithms that are executed by a processor of the ECU 102, and thus operates the engine as a single hardware module in response to inputs received from one or more sensors (not shown) that may be located throughout the engine. In some cases, the ECU 102 includes separate software algorithms corresponding to the described operations of the fuel/air module 104 and the spark module 106. In some cases, the ECU 102 includes separate hardware modules that facilitate implementation or control of the described functions of the fuel/air module 104 and the spark module 106. For example, the spark module 106 of the ECU 102 may include an ASIC to regulate the delivery of current to the ignition coil of the spark plug 120. There are a number of sensor systems to monitor operating parameters of engine 100, which may include, for example, a crankshaft sensor, an engine speed sensor, an engine load sensor, an intake manifold pressure sensor, an in-cylinder pressure sensor, and the like. Typically, these sensors generate signals in response to operating parameters of the engine. For example, crankshaft sensor 171 reads and generates a signal indicative of an angular position of crankshaft 140. In the exemplary embodiment, high speed pressure sensor 172 measures in-cylinder pressure during operation of engine 100. The sensors 171, 172 may be directly connected to the ECU 102 for sensing, or in some cases integrated with a real-time combustion diagnostic and control (RT-CDC) unit configured to acquire high speed data from one or more sensors and provide a low speed data output to the ECU 102. In some cases, the ignition control described herein is a stand-alone ignition control system that provides for operation of the ECU 102 and the spark module 106. The sensor may be integrated into one of the control modules, such as the ECU 102 or the RT-CDC. Other sensors are possible, and the system described herein may include more than one such sensor to facilitate sensing the engine operating parameters described above.

FIG. 1B is a schematic diagram of an engine control system 200 of the engine system 100 of FIG. 1A. FIG. 1B shows ECU 102 within engine control system 200, which is configured to control engine 101. As described above, the high speed pressure data 272 is generated by the pressure sensors 172, each of which is mounted so as to be able to enter the combustion chamber directly. The pressure signal 272 is captured at a high crank sync rate, for example, 0.25 ° resolution or 2880 samples per cycle of the engine 101. The composite crank angle signal is generated from the lower resolution crank position signal. For example, for a typical crank angle encoder 171 that generates a crank angle signal 215 by sensing the passage of a tooth edge on a disc mounted to rotate with the crank, the resolution of the crank position is determined based on the number of teeth. A typical 60-2 gear resolution is 6. However, in some cases, interpolation is used to determine the crank angle in the space between the edges. Thus, the spacing between edges uses the previously observed tooth period divided by the number of edges required to achieve the desired angular sampling resolution. The encoder system is resynchronized at each edge to account for slight variations between the crank teeth that can be seen even if the average engine speed is constant.

In some cases, the resulting high score is used by a combustion diagnostic routine in a real-time combustion diagnostic and control (RT-CDC)211 moduleResolution of the pressure signal 272 to generate a combustion diagnostic 219, e.g., IMEP, P, for each cylinder cycle_{Maximum of}CA50, combustion quality, and combustion intensity, as discussed in more detail below. The indicator 218 is then used by the ECU 102 as a feedback signal to adjust the key combustion performance characteristics by modulating the engine control actuator settings 219.

FIG. 1C is a block diagram of an exemplary engine control unit 102 configured with aspects of the systems and methods disclosed herein. The exemplary engine control unit 102 includes a processor 191, a memory 192, a storage device 1930, and one or more input/output interface devices 194. Each of the components 191, 192, 193, and 194 may be interconnected, for example, using a system bus 195.

Processor 191 is capable of processing instructions for execution in engine control unit 102. The term "executing" as used herein refers to a technique in which program code causes a processor to execute one or more processor instructions. In some implementations, the processor 191 is a single-threaded processor. In some implementations, the processor 191 is a multi-threaded processor. The processor 191 is capable of processing instructions stored in the memory 192 or on the storage device 193. Processor 1910 may perform operations such as calculating a burn intensity.

The memory 192 stores information in the engine control unit 102. In some implementations, the memory 192 is a computer-readable medium. In some implementations, the memory 192 is a volatile memory unit. In some implementations, the memory 192 is a non-volatile memory unit.

The memory device 193 can provide mass storage for the engine control unit 102. In some implementations, the storage 193 is a non-transitory computer-readable medium. In various different embodiments, the storage 193 may include, for example, a hard disk device, an optical disk device, a solid state drive, a flash drive, a magnetic tape, or some other mass storage device. The input/output interface devices 194 provide input/output operations for the engine control unit 102. In some embodiments, the input/output interface device 194 may include an in-cylinder pressure sensor 172, a crank angle sensor 171, or other engine sensors.

In some examples, the engine control unit 102 is contained within a single integrated circuit package. Such an engine control unit 102 is sometimes referred to as a microcontroller, wherein both the processor 191 and one or more other components are housed within a single integrated circuit package and/or fabricated as a single integrated circuit. In some embodiments, the integrated circuit package includes pins corresponding to input/output ports, which may be used, for example, for signal communication with one or more input/output interface devices 1140.

Some aspects of the concepts described herein encompass the ability to collect and process in-cylinder pressure information on a periodic basis and the following algorithms:

(I) peak pressure-maximum combustion pressure during one event;

(II) rate of pressure rise-maximum rate of pressure rise during combustion;

(III) the sum of the pressure pulsations-delta P, also known as the "pressure-based knock index";

(IV) duration of combustion-crank angle between CAx1 and CAx 2;

(V) heat release slope-determinant of the first half of the combustion process compared to the second half of the combustion process;

(VI) location of peak pressure;

(VII) the location of the pulsation;

(VIII) the location of the heat release rate centroid;

(IX) location of maximum heat release rate;

some aspects of the present disclosure use the combustion indicators listed above to determine a combustion intensity value, which can then be used in a control loop to safely drive the engine to a maximum gas substitution rate. All of these criteria are necessary in order to cover the many different situations that can be seen on a dual fuel engine.

One example of an enabling technique disclosed herein is a heat release change algorithm and a combustion duration. The heat release change may be statically determined or dynamically determined to accurately determine the inflection point of combustion acceleration.

Previously, in dual fuel engines, vibration sensors were used, but they only allowed the controller to detect severe knock due to the presence of extreme auto-ignition. Conventional solutions use accelerometers to determine frequency and amplitude to detect detonation. However, the conventional solution is not suitable for dual fuel engines because the signal decays as higher substitution rates are achieved. This makes it difficult to understand near uncontrolled combustion. If a higher rate of substitution is required, the threshold at which the controller takes action must be greater than the highest signal during normal dual fuel combustion. To keep the engine running safely, the knock threshold should be below the maximum intensity, however, this will limit the allowable rate of displacement, as shown in FIG. 2. FIG. 2 shows a graph of accelerometer measurements processed as a function of gas substitution rate in an exemplary engine, as discussed in more detail below. This technique fails particularly in dual fuel combustion because the diesel combustion vein obscures the signal in some dual fuel modes and subsequently when all frequency components disappear at high GSR, thereby not clearly indicating the safety margin for uncontrolled combustion. There is a need for a more robust detection method that can capture combustion conditions. In view of this, a Combustion Intensity (CI) index is prepared.

Some aspects of the present disclosure relate to using direct in-cylinder pressure measurements to calculate an engine index that can be used in some combination to give an increasing detection signal as the rate of substitution continues to increase. This allows the engine controller to achieve a maximum rate of displacement while knowing how close the engine is to uncontrolled combustion, thus keeping the engine running safely. One example of a CI index is represented as a weighted sum of heat release rate and pressure rise rate indices, while including classical indices such as pressure pulsation and peak pressure. In some cases, CI may be any mathematical combination of any of the parameters identified above, such as a polynomial, a weighted sum, an exponential or power law sum, or a non-linear function, CI ═ function (peak pressure, rate of pressure rise, pressure pulsation, duration of combustion, rate of heat generation change, knock exponent);

one exemplary combustion intensity index is expressed as a linear sum of parameters, as shown in equation 1 below.

Equation 1:

CI ═ (a1 · peak pressure) + (a2 · rate of pressure rise) + (a3 · pressure pulsation) + (a3 · duration of combustion) + (a4 · rate of change of heat release) + (a5 · knock index)

The CI index uses pressure-based information and heat release information and does not have the limitations of traditional vibration-based detection. In some cases, the CI indicator is a sum of a pressure indicator, a heat release indicator, and a classical knock indicator.

In some cases, the CI indicator incorporates actual engine limits, which can be easily calibrated by knowing the mechanical limits of the engine. In some cases, the CI indicator also combines classical knock detection and peak pressure limits to have an auxiliary safety measure. The CI indicator correlates well with qualitative combustion sensing that may be observed in the pressure trace during laboratory calibration. The combustion intensity index shown in fig. 6 gradually increases from 30% to 94% with an increase in the gas replacement ratio. FIG. 6, discussed in more detail in example 1 below, illustrates a combustion intensity indicator versus gas substitution rate, which illustrates a comparison between the combustion intensity indicator and a classical knock intensity indicator as a measure of near uncontrolled combustion. A well-defined linear control action path can be set and the controller can aim at this to maximize the gas displacement rate while maintaining a desired safety margin with uncontrolled combustion. In some cases, the combustion intensity indicator describes (or is used to determine) how close the engine is operating to uncontrolled combustion. For example, by using a combustion intensity indicator to control an increase in GSR without causing uncontrolled combustion, by maintaining safe engine operation while allowing an increase in GSR, this allows the engine to achieve a higher replacement rate while maintaining safe operation. The combustion intensity indicator allows for such an increase in safety, for example, by providing a more accurate "picture" of the current combustion state, since the CI indicator may increase with the likelihood of uncontrolled combustion. Thus, using the CI index in engine control may, for example, enable selection of a target CI value, and then using the CI index in the control loop to maximize GSR within the target CI. In some cases, the CI indicator may reduce the calibration requirements.

Aspects of the present disclosure enable consideration of uncontrolled combustion (detonation) no longer in the traditional time-based frequency domain, but from direct in-cylinder pressure information based on actual engine limits. These aspects can reduce the risk of damage to the high-substitution-rate dual-fuel engine. Since the combustion intensity indicator uses known mechanical engine limits, the calibration effort for detecting uncontrolled combustion is greatly reduced. The exemplary embodiment also allows the engine to be controlled to operate at maximum substitution rate at all times without having to increase a safety margin, which provides a more valuable recommendation to bi-fuel engine operators.

An exemplary improvement in vibration-based detection is to incorporate heat release while burning, as this is the primary effect of adding natural gas, as can be seen in the plot of smoothed heat release trajectories at 0%, 60%, and 90% Gas Substitution Rate (GSR) shown in fig. 7 and discussed in more detail below in example 1. After the addition of natural gas, the conventional diesel premixing spike decreases and then develops a very high heat release rate at 60%. It can be monitored for the current state of combustion intensity. At 90% GSR or above, combustion becomes fully gas dominated and the engine behaves almost like a spark-ignited or micro-pilot ignited gas engine.

The CI indicator is a progressive measure of combustion state and is a good indicator of near uncontrolled combustion, as can be seen in the examples below.

Example 1

A study was conducted of the effect of adding gas on the original diesel combustion characteristics of a diesel-natural gas dual fuel engine, wherein the stand-by engine compression ratio of the original diesel engine was kept constant. The specifications of the dual fuel engine used in this study are shown in table 1. Any uncontrolled combustion on a Dewetron combustion analyzer was captured using a Woudet knock sensor (WLEKS) and a Kistler (Kistler)6058A piezoelectric in-cylinder pressure sensor and sampled at 200 kHz. The engine was always placed in steady operating condition at the 100% diesel target set point for IMEP and MAT before using the chemical energy split calculation to replace diesel with gas. Diesel is injected between 2 and 8 degrees before top dead center, depending on the operating position of the engine in the speed load map. The Gas Substitution Rate (GSR) was increased in 10% increments and repeated at different speeds and load points. The data shown in the following figures (fig. 2-11) are averages of 300 combustion cycles. The methane number of the natural gas used in this study was about 82, with 84% methane, 9% ethane and 1% propane.

Table 1: specification of dual-fuel engine

An example of raw in-cylinder pressure and vibration knock trace captured at 10 bar IMEP, 1400 rpm is plotted in FIG. 3. Fig. 3 is a graph of in-cylinder pressure and vibration trace at 0%, 60% and 90% gas substitution rates 301, 302, 303(GSR) at 1400 rpm and 10 bar IMEP. Figure 3 shows that pressure pulsations are visible when 0% gas (100% diesel) is running (diesel combustion). As the gas increases from 0% to 30% GSR (not shown), the overall combustion begins to become more stable, with diesel combustion still predominating. Further increase to 60% (second curve) shows a noisier diesel-gas combustion region with increased knock frequency components detected by the vibration and in-cylinder pressure sensors. This can be seen in fig. 2, where pressure and vibration knock intensity reach maximum values at 60% GSR. At 90% GSR, the vibration signal is at the most stable position (third curve).

FIG. 4 is a graph of vibration and pressure knock intensity versus gas displacement rate. Fig. 3 and 4 illustrate the following challenges: the intensity of the vibration knock signal at this operating point increases from 0% GSR to 60% GSR, which is also captured in fig. 4, but then decreases and falls to a minimum at 90% displacement-i.e., just before a very strong combustion knock is observed (which is also indicated in fig. 2, but 300 cycles cannot be recorded). As the gas substitution rate increases from 60% to 85%, gas combustion becomes more and more dominant in the latter half of combustion. At this stage, all frequency components disappeared, as seen in fig. 4. Classical methods of pressure pulsation or knock spectral content become difficult to detect close to knocking or uncontrolled combustion. This presents a very difficult control problem for the engine controller, because it is difficult to accurately perform closed-loop control when the engine is operating near uncontrolled combustion. This is in contrast to spark ignition gas engines, where vibration-based knock can detect mild, moderate, and severe knock, thus enabling the controller to adjust engine parameters before severe/severe knock occurs. In dual fuel engines, vibration sensors may be used, but they only allow the controller to detect severe knock due to the presence of extreme auto-ignition. It is sensible to use an open loop table or a much lower allowed GSR to keep the knock level within a monotonic range. If a higher rate of substitution is required, the threshold at which the controller takes action must be greater than the highest signal during normal dual fuel combustion. To keep the engine running safely, the knock threshold should be below the maximum intensity, however, this will limit the allowable rate of displacement, as shown in FIG. 2.

Fig. 5A is a 2-dimensional contour plot of pressure knock intensity versus gas substitution rate at various speeds, and fig. 5B is a 2-dimensional contour plot of vibration knock intensity versus gas substitution rate at various speeds. Fig. 5A and 6B indicate non-monotonic and non-linear trends, which would prove difficult to design a robust control. Pressure knock intensity and vibration knock intensity techniques fail in dual fuel combustion because diesel combustion veins obscure the signal in certain dual fuel modes and subsequently when all frequency components disappear at high GSR, thereby not clearly indicating the safety margin for uncontrolled combustion.

FIG. 6 is a graph showing Combustion Intensity (CI) indicator effect versus a classical knock intensity indicator as an approximate measure of uncontrolled combustion and as a function of gas displacement. The CI indicator of the present disclosure is a more robust detection method that can capture the combustion state. FIG. 6 shows that the CI indicator provides a good indication of near uncontrolled combustion, and in some cases, the CI indicator is a progressive measure of combustion state. The CI indicator incorporates actual engine limits which can be calibrated by knowing the mechanical limits of the engine. In some embodiments and as shown above in equation 1, CI is a weighted sum of the heat release rate and pressure rise rate indicators, in addition to classical indicators such as pressure pulsation and peak pressure. In some cases, the CI indicator uses pressure-based information and heat release information, which does not have the limitations of traditional vibration-based detection. In some cases, the CI indicator also combines classical knock detection and peak pressure limits to have an auxiliary safety measure. In some embodiments, the CI indicator correlates well with qualitative combustion sensing that may be observed in the pressure trace during laboratory calibration.

Fig. 7 is a graph of the smooth heat release trace at 0% (701), 60% (702), and 90% (703) gas substitution rate. The main improvement of vibration-based detection is the incorporation of real-time heat release, as this is the main effect of adding natural gas, as can be seen in the plots of smoothed heat release traces at 0%, 60% and 90% Gas Substitution Rate (GSR) shown in fig. 7. After the addition of natural gas, the conventional diesel premixing spike decreases and then develops a very high combined heat release rate at 60%. It can be monitored for the current state of combustion intensity. At 90% GSR or above, combustion becomes fully gas dominated and the engine behaves almost like a spark-ignited or micro-pilot ignited gas engine.

Referring again to fig. 6, the CI index gradually increases as the gas substitution rate increases from 30% to 94%. A well-defined linear control action path can be set and the controller can aim at this to maximize the gas displacement rate while maintaining a desired safety margin with uncontrolled combustion. This linearity can be seen even in the 2-dimensional contour plot of combustion intensity shown in FIG. 8, which has a monotonic trend at all speeds. One of the indicators in the CI calculation that helps to linearize this indicator is the heat release rate, since the latter half of the combustion duration will burn faster as more gas is added, as shown in fig. 9.

FIG. 9 is a graph of angular position of total heat release versus gas substitution rate for 10% (901), 50% (902), and 90% (903). In fig. 9, crank angle positions for 10%, 50%, and 90% of the total heat release are shown, which is helpful in understanding combustion phasing, spark retard, and combustion rate. As diesel was replaced by gas, start of injection (SOI) and CA50 were unaffected at this operating point, indicating that combustion phasing did not change much. As the GSR increases, the angular separation between CA90 and CA50 decreases dramatically, indicating faster combustion of the end gas. Further, as GSR increases from 0% to 70%, CA10 increases slightly, indicating a longer spark retard. As the gas displaces air, the oxygen concentration will be lower and therefore the mixture will be richer and the ignition delay will be longer. Accordingly, as the gas/air mixture becomes richer, the flame speed continues to increase until a very short duration of combustion occurs, which is a condition for terminal gas auto-ignition. At the operating point shown above, the terminal gas auto-ignition condition is not reached, and the GSR reaches 94%, at which time the limit for diesel injector output is reached.

The increased GSR results in auto-ignition of the end gas with greater pulsations in pressure as shown by the pressure and heat release rate traces in fig. 10 and 11. Fig. 10 and 11 show plots of in-cylinder pressure versus crank angle for 0% (1001), 60% (1002), and 90% (1003) gas substitution, and smoothed heat release trajectories versus crank angle for 0% (1101), 60% (1102), and 90% (1003) gas substitution. Fig. 12 is a graph of combustion intensity and knock intensity indicator versus Gas Substitution Rate (GSR) showing that when there is severe end gas knock, both the pressure knock intensity indicator and the vibration knock intensity indicator increase sharply with combustion intensity. Thus, it appears that the spectral content of frequency-based detection techniques, such as vibrations or pressure pulsations, cannot be clearly seen until intense knock occurs. At low loads, these vibration or pressure techniques have difficulty clearly determining margins to knock because the trend is non-monotonic. If a simple threshold-based severity is to be determined, this example shows that high threshold levels will only capture knock events that may suddenly occur that are so severe as to damage the engine. If a lower threshold level is used to quantify harshness, the engine should not be allowed to exceed a 50-60% gas substitution rate. In contrast, the CI indicator of the present invention provides a continuously increasing measure of combustion state to provide better controllability and increase the maximum safe gas substitution rate (e.g., up to 95% gas substitution rate), while improving protection against uncontrolled combustion.

Example 2

In example 2, the effect of gas quality was simulated by replacing natural gas with propane. Fig. 13 and 14 show traces of pressures 1301, 1302, 1303 and smoothed heat release rates 1401, 1402, 1403 with increasing propane displacement ratio (PSR) from 0% to 15% at 1800 rpm, 16 bar IMEP at a fixed (total) gas displacement rate of 80%. In this test, the contribution of diesel was kept at 20%, while propane displaced natural gas in 5% PSR increments using the chemical energy distribution calculation. These figures show that even a small proportion of propane causes a severe exotherm and rate of pressure rise, and produces large and visible pressure oscillations. Fig. 15 is a graph of CI (1503) and knock intensity indicators (1501, 1502) versus propane gas substitution rate (PSR) and shows that as propane is added, the CI indicator is still reliable indicating highly unstable combustion.

Fig. 16 is a graph of combustion intensity (1603) and knock intensity index (1601 ) versus Manifold Air Temperature (MAT). FIG. 16 illustrates the effect of charge air temperature or density on detecting near uncontrolled combustion. The increase in charge air temperature affects spark retard, the rate of in-cylinder temperature increase, and the engine's propensity for auto-ignition. These criteria were compared as the Manifold Air Temperature (MAT) increased from 40 ℃ to 60 ℃ at 1800 rpm at 16 bar IMEP. The results show that only the CI indicator increases linearly with MAT and can be reliably used as a close measure of uncontrolled combustion, while other knock intensity indicators do not provide a clear trend.

Example 3 and example 4

The wood wad Large Engine Control Module (LECM) is used to test CI indicators on a real embedded ECU, allowing real-time combustion feedback to be performed using the AUX (auxiliary) module. Two cases were tested to show the sensitivity of the CI indicator to detect combustion changes. Fig. 17A and 17B show a first test case in which the sine wave command of the GSR (1701) is issued with a displacement of 50% and an amplitude of 20%, as shown in fig. 17A. FIG. 17B shows that the CI measure responds well to changes when the indicator changes from 0% intensity to 90% intensity. The amplitude was then reduced to 10% and the CI indicator showed 50% intensity at the peak. Then, while still commanding the sine wave, the natural gas is replaced with 10% propane (1702) to simulate the gas quality change, which can be seen by the CI indicator (1701) detecting by indicating a higher intensity.

For the second case, as shown in fig. 18A, the Manifold Air Temperature (MAT) is allowed to increase to about 55 ℃, and then rapidly cooled. FIG. 18B shows that the CI index increases with increasing MAT, as expected. The results show that the CI indicator can detect external disturbances well. In some cases, the CI indicator is used to control the engine to a defined limit. Aspects of the CI indicators disclosed herein may significantly reduce the amount of calibration and safety margin typically considered for dual fuel engines. Such a detection method should allow a higher substitution rate to be achieved.

Fig. 19 is a flow chart 1900 of an exemplary aspect of the present disclosure. An engine controller (e.g., ECU 102) samples (1910) a pressure signal from an in-cylinder pressure sensor, calculates (1920) a combustion intensity indicator based on the pressure signal, wherein the combustion intensity indicator is indicative of an engine approaching an uncontrolled combustion condition, determines (1930) an engine control parameter from the combustion intensity indicator, and controls (1940) the engine based on the engine control parameter.

Embodiments of the subject matter described in this specification, such as calculating a combustion intensity indicator, may be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a tangible program carrier, such as a computer readable medium for execution by, or to control the operation of, a processing system. The computer readable medium can be a machine readable storage device, a machine readable storage substrate, a storage device, or a combination of one or more of them.

The term "engine control unit" may encompass all devices, apparatus, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. In addition to hardware, the processing system can include code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

A computer program (also known as a program, software application, script, executable logic or code) can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile or volatile memory, media and storage devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks or tapes; magneto-optical disks; and CD-ROM, DVD-ROM, and Blu-ray discs. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

Acronyms/abbreviations:

after ATDC-top dead center

BTDC before top dead center

CA50 position of 50% mass fraction burn (crank angle ATDC)

Controller area network

Coefficient of variation (COV)

ECU (electronic control Unit)

EGR-exhaust gas recirculation

HCCI-homogeneous charge compression ignition

IMEP mean effective pressure (bar) as indicated

IVC-intake valve closing angle

LTC (low temperature co-fired ceramic) combustion

MAP manifold absolute pressure (bar)

MAT manifold absolute temperature (K)

NOx (nitrogen oxide)

PCCI-premixed charge compression ignition

Ploc ═ location of peak pressure (crank angle ATDC)

Pmax ═ maximum cylinder pressure (bar)

Research and development of R & D ═

RCCI-reactivity controlled compression ignition

RPR ═ rate of pressure rise (bar/crank angle)

Real-time combustion diagnosis and control

SOC (start of combustion) (crank angle ATDC)

A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims.