Ignition unit and low-energy-consumption diesel engine tail gas treatment system based on ignition unit
阅读说明:本技术 点火单元及基于点火单元的低能耗柴油机尾气处理系统 (Ignition unit and low-energy-consumption diesel engine tail gas treatment system based on ignition unit ) 是由 齐宝华 于 2019-12-04 设计创作,主要内容包括:本发明公开了一种点火单元及基于点火单元的低能耗柴油机尾气处理系统,包括具有入口和出口的点火壳体以及喷嘴管、用于避免高温尾气回流的第一摆动止回阀、具有空气入口和火焰出口的腔体和用于点燃的电热塞,所述喷嘴管通过燃油电磁阀与外设燃油供给单元相连接并穿过第一摆动止回阀伸入腔体内,电热塞固定于点火壳体上并伸入腔体内。本发明新鲜空气和燃油在点火单元中混合后点燃,三通空气通道接收高温混合气流和尾气气流,形成的总气流进入DPF并在其中氧化去除积的炭烟;降低了DOC和DPF中对PGM涂层的要求,并降低了系统对燃油中硫含量的敏感性,而低尾气流量的再生降低了能耗;提高了燃油经济性,从而适合于在用车改装应用。(The invention discloses an ignition unit and a low-energy-consumption diesel engine tail gas treatment system based on the ignition unit, which comprise an ignition shell with an inlet and an outlet, a nozzle pipe, a first swing check valve for avoiding high-temperature tail gas from flowing back, a cavity with an air inlet and a flame outlet and a glow plug for ignition, wherein the nozzle pipe is connected with an external fuel supply unit through a fuel electromagnetic valve and extends into the cavity through the first swing check valve, and the glow plug is fixed on the ignition shell and extends into the cavity. Fresh air and fuel oil are mixed in an ignition unit and then ignited, a three-way air channel receives high-temperature mixed air flow and tail gas air flow, and formed total air flow enters a DPF and is oxidized in the DPF to remove accumulated soot; the requirements on PGM coatings in DOC and DPF are reduced, the sensitivity of the system to the sulfur content in the fuel is reduced, and the low-tail gas flow regeneration reduces the energy consumption; the fuel economy is improved, so that the method is suitable for refitting and application in vehicles.)
1. An ignition unit, characterized by: the ignition device comprises an ignition shell with an inlet and an outlet, nozzle pipes, a first swing check valve, a cavity and a glow plug, wherein the nozzle pipes are arranged in the ignition shell along the direction of an ignition flame, the first swing check valve is used for avoiding backflow of high-temperature tail gas, the cavity is provided with an air inlet and a flame outlet, the glow plug is used for ignition, the nozzle pipes are connected with an external fuel supply unit through a fuel electromagnetic valve and penetrate through the first swing check valve to extend into the cavity, and the glow plug is fixed on the ignition shell and extends into the cavity.
2. The ignition unit of claim 1, wherein: the first swing check valve comprises a first check plate obliquely arranged on the cross section of the ignition shell, and the side surface of the first check plate is connected with the air inlet of the cavity; the first check plate is provided with a through hole for the nozzle pipe to penetrate and be connected with the cavity and a first valve hole for circulating gas, and the first valve hole is hinged with a first valve plate for one-way conduction.
3. The ignition unit of claim 1, wherein: and a support frame for fixing the nozzle pipe is arranged in the ignition shell.
4. A low energy consumption diesel exhaust treatment system based on an ignition unit according to any one of claims 1 to 3, characterized in that: the device comprises a controller, an air supply unit, an ignition unit, a three-way air channel and a packaging unit wrapped with a DPF, wherein the air supply unit, the ignition unit, the three-way air channel and the packaging unit are sequentially arranged along the airflow direction; the controller is respectively and electrically connected with the air supply unit, the glow plug, the fuel electromagnetic valve, the fuel supply unit, the first temperature sensor, the second temperature sensor, the pressure sensor, the differential pressure sensor and the mass flow sensor.
5. Low energy consumption diesel engine exhaust treatment system according to claim 4, characterized in that: the fuel supply unit comprises an oil tank, a fuel pump and a stop valve which are connected in sequence, the stop valve is connected with the ignition unit through a fuel line, an oil pressure sensor is further arranged on the stop valve, and the controller is respectively electrically connected with the stop valve, the oil pressure sensor and the fuel pump.
6. Low energy consumption diesel engine exhaust treatment system according to claim 4, characterized in that: the air supply unit includes a fan connected to the ignition unit through an air passage and a driver located within the fan and electrically connected to the controller.
7. Low energy consumption diesel engine exhaust treatment system according to claim 4, characterized in that: tee bend air passage is connected with engine exhaust through interface channel, is equipped with the second swing check valve that is used for avoiding high temperature tail gas backward flow in this interface channel, second swing check valve includes that the slant sets up the second check plate on the passageway cross section, offers the second valve opening that is used for circulating gas on the second check plate, and it has the second valve block that is used for one-way conduction to articulate on this second valve opening.
8. Low energy consumption diesel engine exhaust treatment system according to claim 4, characterized in that: a heat exchanger is connected between the air supply unit and the ignition unit, a shell-side inlet of the heat exchanger is connected with the air supply unit, a shell-side outlet of the heat exchanger is connected with the ignition unit, a pipe-side inlet is connected with an outlet of the packaging unit through an exhaust passage, and a pipe-side outlet is connected with an external device.
Technical Field
The invention relates to a tail gas treatment system, in particular to an ignition unit and a low-energy-consumption diesel engine tail gas treatment system based on the ignition unit.
Background
Exhaust gas emitted from an engine has been identified as a major factor causing air pollution. In order to remove air pollutants from exhaust gas, an exhaust gas treatment system is used. A commonly used exhaust treatment system uses a diesel particulate trap (DPF) to trap Particulate Matter (PM), which may include unburned hydrocarbon particles or soot and small amounts of other particles, such as metal oxide particles or ash, among others. PM particles accumulate in the DPF, increasing the engine back pressure, and a regeneration process is required to remove the accumulated soot before the engine back pressure becomes too high.
Typically, during regeneration, it is necessary to use a heating device to raise the exhaust gas temperature to a level where soot can be efficiently oxidized by oxygen, which may be provided by the exhaust gas in a lean-burn engine. The high temperature exhaust gas then passes through the DPF, where the accumulated soot is oxidized to carbon dioxide and water.
A wide variety of heating devices may be used to regenerate the DPF. Of these, the more widely used are fuel burners and Diesel Oxidation Catalyst (DOC) devices. In a fuel burner, hydrocarbon is supplied by a fuel metering device from which hydrocarbon fuel is injected into a combustion chamber. In the DOC device, hydrocarbon may be provided by the engine fuel system during the post-injection process, or may be injected directly into the catalyst by an external hydrocarbon injection device.
When regenerating a DPF, the fuel burner is not limited by exhaust gas temperature. However, for burning the fuel, a fresh air flow is required and additional heat energy is required to heat the fresh air flow, which results in higher energy consumption. In addition, the fresh air flow needs to be mixed with the exhaust flow before entering the DPF, thus requiring more fuel and fresh air flow to reach regeneration temperatures. This in turn requires a powerful air supply to provide more fresh air flow because of the high fresh air flow and high exhaust flow creating a high pressure differential across the DPF. High power air supplies further increase energy consumption and system cost. Also, as previously described, to bring the mixed exhaust and fresh air flow to DPF regeneration temperature, a higher temperature fresh air flow is required. The high temperature fresh air flow resulting from fuel combustion can cause difficulties in DPF temperature control, especially when exhaust flow is suddenly reduced, such as when the engine is rapidly brought down from high speed and high torque operation to idle. These difficulties require complex high temperature control equipment and methods, resulting in higher system costs.
In contrast to oil burners, DOCs do not require fresh air to burn the oil. However, the DOC requires a high PGM (precious metal) loading and only when the exhaust temperature is above the light-off temperature (typically above 200 ℃), does the fuel start to be metered. At the same time, PGM in DOC is sensitive to sulfur content in the fuel oil, as high sulfur content in the exhaust gas can poison and render PGM catalysts ineffective. The requirement of high temperature exhaust gas limits certain applications of the DOC, such as low power output industrial applications and frequent start-stop vehicle applications.
In order to reduce the effect of operating condition changes on DPF temperature control during DPF regeneration, it is common for DPF controllers to obtain information on engine operating conditions, such as in a DOC-equipped DPF system where the engine air-fuel ratio is used to determine the highest fuel delivery rate above which fuel cannot be efficiently oxidized in the DOC. In DPF systems with fuel burners, close monitoring of engine exhaust flow is required. The DPF controller should react in time to sudden drops in exhaust flow to avoid overheating problems. The requirement for engine operating information limits the use of DPF systems in systems that do not have suitable sensing and communication means, such as modifications to engines that mechanically control fuel systems.
Thus, there is a need to solve the above problems.
Disclosure of Invention
The purpose of the invention is as follows: a first object of the present invention is to provide an ignition unit that can effectively prevent backflow of high-temperature exhaust gas.
A second object of the invention is to provide a low energy diesel exhaust gas treatment system based on an ignition unit.
The technical scheme is as follows: in order to achieve the above purpose, the invention discloses an ignition unit, which comprises an ignition shell with an inlet and an outlet, a nozzle pipe, a first swing check valve, a cavity and a glow plug, wherein the nozzle pipe is arranged in the ignition shell along the direction of an ignition flame, the nozzle pipe is arranged in the ignition shell, the first swing check valve is used for avoiding the backflow of high-temperature tail gas, the cavity is provided with an air inlet and a flame outlet, the glow plug is used for ignition, the nozzle pipe is connected with an external fuel supply unit through a fuel electromagnetic valve and penetrates through the first swing check valve to extend into the cavity, and the glow plug is.
The first swing check valve comprises a first check plate obliquely arranged on the cross section of the ignition shell, and the side surface of the first check plate is connected with the air inlet of the cavity; the first check plate is provided with a through hole for the nozzle pipe to penetrate and be connected with the cavity and a first valve hole for circulating gas, and the first valve hole is hinged with a first valve plate for one-way conduction.
Preferably, a support frame for fixing the nozzle pipe is arranged in the ignition housing.
The invention relates to a low-energy-consumption diesel engine tail gas treatment system based on an ignition unit, which comprises a controller, an air supply unit, the ignition unit, a three-way air channel and an encapsulation unit wrapped with a DPF, wherein the air supply unit, the ignition unit, the three-way air channel and the encapsulation unit are sequentially arranged along the airflow direction; the controller is respectively and electrically connected with the air supply unit, the glow plug, the fuel electromagnetic valve, the fuel supply unit, the first temperature sensor, the second temperature sensor, the pressure sensor, the differential pressure sensor and the mass flow sensor.
Preferably, the fuel supply unit comprises a fuel tank, a fuel pump and a stop valve which are connected in sequence, the stop valve is connected with the ignition unit through a fuel line, an oil pressure sensor is further arranged on the stop valve, and the controller is electrically connected with the stop valve, the oil pressure sensor and the fuel pump respectively.
Furthermore, the air supply unit includes a fan connected to the ignition unit through an air passage and a driver located inside the fan, the driver being electrically connected to the controller.
Further, tee bend air passage is connected with engine exhaust through interface channel, is equipped with the second swing check valve that is used for avoiding high temperature tail gas backward flow in this interface channel, second swing check valve includes that the slant sets up the second check plate on the passageway cross section, offers the second valve opening that is used for circulating gas on the second check plate, and it has the second valve block that is used for one-way conduction to articulate on this second valve opening.
Preferably, a heat exchanger is connected between the air supply unit and the ignition unit, a shell-side inlet of the heat exchanger is connected to the air supply unit, a shell-side outlet is connected to the ignition unit, a tube-side inlet is connected to an outlet of the packing unit through an exhaust passage, and a tube-side outlet is connected to an external device.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:
the ignition unit can effectively prevent the backflow of high-temperature tail gas; in the regeneration process of the DPF, fresh air and fuel oil are mixed in the ignition unit and then ignited, the three-way air channel receives high-temperature mixed air flow and tail gas air flow, the formed total air flow enters the DPF and is oxidized in the DPF to remove accumulated soot, wherein the air supply unit provides fresh air flow to the ignition unit only when the pressure in the three-way air channel is lower, and the fresh air flow is lower when the pressure is higher; the ignition device reduces the requirements on PGM coatings in DOC and DPF, reduces the sensitivity of the system to the sulfur content in fuel, and reduces the energy consumption by regenerating low tail gas flow; in addition, the low PGM coating in the DPF also reduces engine backpressure, thereby improving fuel economy, and regeneration with low exhaust flow and even zero exhaust flow allows regeneration control to be independent of engine control, thereby making the DPF control system suitable for in-vehicle retrofit applications; the invention also reduces the energy consumption during regeneration by adding a heat exchanger for recycling heat energy, namely the heat exchanger between the air supply unit and the ignition unit is used for 'recovering' heat energy in DPF regeneration, and in the heat exchanger, high-temperature air flow can exchange heat energy with fresh air flow after oxidizing particulate matters accumulated in DPF; the thermal energy released by burning the fuel in the ignition device is used only to compensate the energy loss in the DPF and the air passage, thereby minimizing the energy consumption; in addition, when the system is not regenerated, only a part of the heat exchanger has influence on the back pressure of the engine, and the fuel economy and the renewable energy consumption of the engine can be balanced more easily.
Drawings
FIG. 1 is a schematic structural diagram of a low energy consumption diesel exhaust treatment system according to the present invention;
FIG. 2 is a schematic view showing the construction of an ignition unit and an air supply unit according to the present invention;
FIG. 3 is a schematic view of a second swing check valve in the connecting passage according to the present invention;
FIG. 4 is a schematic flow diagram of a DPF temperature control system based on a low energy diesel exhaust treatment system according to the present invention;
FIG. 5 is a schematic flow chart of a control method of the DPF temperature control system of the present invention;
FIG. 6 is a schematic view of the structure of the present invention equipped with a heat exchanger;
FIG. 7 is a schematic diagram of a low energy diesel exhaust treatment system suitable for use at high exhaust flow rates in accordance with the present invention;
FIG. 8 is a flow chart illustrating a control method of the low energy consumption diesel exhaust treatment system according to the present invention, which is suitable for use at high exhaust flow rates.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
As shown in fig. 1, the low energy consumption diesel engine exhaust gas treatment system of the present invention includes a controller 130, an
When fuel is supplied to the
As shown in fig. 1, during regeneration, the
As shown in fig. 2, the
In the
In order to prevent the high temperature air from flowing into the engine, as shown in fig. 3, a second
As shown in fig. 1, when regenerating a DPF, after reaching an equilibrium state, the energy balance equation is:
wherein T is161Is a temperature sensing value, T, obtained from the
In order to fully combust the injected fuel, the flow of fresh air must be above a certain value determined by the equivalence air-fuel ratio:
wherein λ0Is the equivalent air-fuel ratio, λ is the relative air-fuel ratio, and λ has a value greater than 1.0.
From the energy balance equations (1) and (2), at the target regeneration temperature, the mass flow of injected fuel can be calculated by the following equation:
equation (3) shows that when regeneration is re-triggered after engine shutdown, i.e.,
the mass flow of injected fuel can be significantly reduced. While the value may be further reduced when the DPF system is insulated, i.e., when the thermal energy exchange rate is reduced.
In fact, equation (3) also shows that, at equilibrium, the energy released when burning the injected fuel compensates for the heat lost to the environment by the mixed flow through the DPF. The higher the heat loss rate, i.e. the higher the Q value, the more fuel injection is required. Furthermore, according to equation (1), "pure" energy loss, i.e. energy not used to compensate for heat losses from the gas stream, is the first part of the equation, i.e. energy not used to compensate for heat losses from the gas stream
Wherein E islIs a pure energy loss. According to equation (4), when the engine is being regenerated at shutdown
The net energy loss or energy waste is determined by the heat loss rate Q. The higher the value, the more energy is removed from the DPF system by the gas stream to compensate for the heat loss.In order to reduce energy consumption, the mass flow of fresh air and tail gas needs to be reduced during regeneration. Thus, when regeneration is initiated, the DPF temperature can be controlled using a control system such as that shown in FIG. 4.
The invention discloses a DPF temperature control system based on a low-energy-consumption diesel engine tail gas treatment system, which comprises a change rate limiter 402, a feedforward controller 403, a PID controller 404, a PWM calculation module 405 and a protection module 406, wherein the change rate limiter 402 calculates a temperature instruction value according to a DPF target temperature DPFT _ target and a DPF inlet temperature DPFinT measured by a
The change rate limiter 402 calculates a temperature command value based on the DPF target temperature DPFT _ target and the DPF inlet temperature DPFinT measured by the
temp _ CtrlCmd ═ minimum value (DPFT _ target, DPFinT + deltaT)
Where Temp _ ctrl cmd is a temperature command value, and deltaT is a set value for limiting the DPF inlet temperature change rate.
For the feedforward controller 403, according to the energy balance equation (1), the calculation formula for obtaining the feedforward control command in the feedforward controller is:
Fuel_MF=[(DPFinT-Exh_T)×Cp_2×Exh_MF+(DPFinT-Ambient_T)×Cp_1×Fresh_MF]/LHV
wherein Fuel _ MF is a feedforward control instruction, Cp _1 and Cp _2 are two constants, and LHV is the low heating value of the Fuel.
The feedback control command may be generated using PID control in the PID controller 404, and the PWM duty ratio value may be calculated in the PWM module 405 by a table look-up method using the sum of the feedback control command and the feedforward control command and the fuel pressure value as inputs, the values in the table being calibrated by experimental results.
As shown in fig. 1, to minimize energy consumption during regeneration of the DPF159, the flow of fresh air generated by the
The invention relates to a DPF temperature control method based on a low-energy-consumption diesel engine tail gas treatment system, which comprises the following steps of:
transmitting the DPF target temperature DPFT _ target and the DPF inlet temperature DPFinT measured by the first temperature sensor 166 to the change rate limiter 402, the change rate limiter 402 calculating a temperature command value based on the DPF target temperature DPFT _ target and the DPF inlet temperature DPFinT measured by the first temperature sensor 166, and transmitting the temperature command value to the feedforward controller 403; transmitting the tail gas temperature Exh _ T, the Ambient temperature Ambient _ T, the Fresh air mass flow Fresh _ MF and the exhaust mass flow Exh _ MF to a feedforward controller 403, and calculating a feedforward control instruction by the feedforward controller 403 according to the tail gas temperature Exh _ T, the Ambient temperature Ambient _ T, the Fresh air mass flow Fresh _ MF, the exhaust mass flow Exh _ MF and the temperature instruction value; the temperature error signal obtained by comparing the temperature instruction value with the DPF inlet temperature DPFinT is transmitted to the PID controller 404, the PID controller 404 calculates a feedback control instruction according to the temperature error signal, a calculated value obtained by adding the feedback control instruction and the feedforward control instruction is transmitted to the PWM calculation module 405, the PWM calculation module 405 calculates a PWM duty ratio value according to the calculated value and the fuel pressure value and transmits the PWM duty ratio value to the protection module 406, the Fresh air mass flow Fresh _ MF is transmitted to the protection module 406, and the protection module 406 calculates a PWM duty ratio instruction for controlling the fuel solenoid valve 225 according to the PWM duty ratio value and the Fresh air mass flow Fresh _ MF.
The calculation formula of the temperature command value in the change rate limiter 402 is:
temp _ CtrlCmd ═ minimum value (DPFT _ target, DPFinT + deltaT)
Where Temp _ ctrl cmd is a temperature command value, and deltaT is a set value for limiting the DPF inlet temperature change rate.
The calculation formula of the feedforward control command in the feedforward controller 403 is:
Fuel_MF=[(DPFinT-Exh_T)×Cp_2×Exh_MF+(DPFinT-Ambient_T)×Cp_1×Fresh_MF]/LHV
wherein Fuel _ MF is a feedforward control instruction, Cp _1 and Cp _2 are two constants, and LHV is the low heating value of the Fuel.
The control method of the protection module 406 comprises the following steps: firstly, checking the regeneration state of the DPF, and if the DPF is in the regeneration state, calculating the change rate of Fresh air mass flow Fresh _ MF; if the decrease rate of the value of the Fresh _ MF is detected to exceed the threshold value Thd _ MFR or the value of the Fresh _ MF < the threshold value Thd _ MF, the PWM duty ratio is set to 0, and the regeneration process is stopped.
In the DPF regeneration process, it can be seen from equation (3) that lower exhaust gas flow can achieve lower energy consumption, and this energy consumption is minimized when the exhaust gas flow is zero. However, according to equation (4), even when the exhaust flow is zero, in order to compensate for the heat loss in the DPF system, additional thermal energy is required in addition to the heat loss itself, and this thermal energy is carried away by the air flow. To further reduce energy consumption, heat exchange devices may be used to further "recover" this excess heat energy. As shown in fig. 6, the
where α is the heat exchanger efficiency coefficient, this value is 1 when the heat transfer is most efficient, i.e., all the thermal energy gained in the
As shown in fig. 1, in the DPF system, in order to reduce energy consumption, the DPF159 is regenerated only when the exhaust gas flow rate is low. In mobile applications, when the DPF system is mounted on a vehicle, low-flow regeneration can be achieved by regenerating the DPF only when the vehicle is stopped. In this case, the engine will be stopped or at idle and its exhaust gas flow will be low. For applications requiring DPF regeneration with high exhaust gas flow, another regeneration system may be selected, as shown in fig. 7, the low-energy-consumption diesel engine exhaust gas treatment system suitable for high exhaust gas flow rate of the present invention comprises a controller 130 and two regeneration systems used alternately, one regeneration system comprises an air supply unit 120, an ignition unit 140, a three-way air channel 144 and an encapsulation unit 150 wrapped with a DPF159, which are arranged in sequence along an air flow direction, the three-way air channel 144 is further externally connected with engine exhaust gas, the ignition unit 140 is connected with a fuel supply unit, a first temperature sensor 166 and a second temperature sensor 161 are arranged on the upper and lower streams of the DPF159, a pressure sensor 163 and a differential pressure sensor 164 for measuring the outlet pressure of the DPF and the pressure difference passing through the DPF are connected with the DPF159, and a mass flow rate sensor 125 for measuring the mass flow rate of fresh air is arranged at the outlet of the air supply unit 120; the other regeneration system comprises a secondary air channel 414, a secondary ignition unit 440, a secondary three-way air channel 444 and a secondary packaging unit 450 wrapped with a secondary DPF459, which are sequentially arranged along the air flow direction and connected with an air supply unit 120 and an ignition unit 140 through a three-way channel 413, wherein the secondary three-way air channel 444 is also externally connected with engine exhaust, the secondary ignition unit 440 is connected with a fuel supply unit, the upper and lower parts of the secondary DPF459 are provided with a third temperature sensor 466 and a fourth temperature sensor 461, and the secondary DPF459 is connected with a secondary pressure sensor 463 and a secondary pressure difference sensor 464 which are used for measuring the outlet pressure of the secondary DPF and the pressure difference passing through the secondary DPF; the controller 130 is electrically connected to the air supply unit 120, the ignition unit 140, the sub ignition unit 440, the fuel supply unit, the first temperature sensor 166, the second temperature sensor 161, the third temperature sensor 466, the fourth temperature sensor 461, the pressure sensor 163, the sub pressure sensor 463, the differential pressure sensor 164, the sub differential pressure sensor 464, and the mass flow rate sensor 125, respectively. The ignition unit and the sub-ignition unit of the present invention have the same structure, and the
In low energy diesel exhaust treatment systems suitable for high exhaust flow rates, the secondary DPF459 in the
As shown in FIG. 7, the DPF159 and the
As shown in FIG. 8, the method may be used to control the DPF system of FIG. 7. In this method, the DPF159(DPFA) is regenerated first, and then the control valve 411 (exhaust valve a) is closed with the sub-control valve 412 (exhaust valve B) open. When regeneration of DPF159(DPFA) is complete, secondary control valve 412 (exhaust valve B) is closed and control valve 411 (exhaust valve a) is opened to regenerate
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