CN107061064A - A kind of equivalent combustion system and its control method based on air-fuel mixture enleanment - Google Patents

Abstract

The invention discloses an equivalent combustion system based on mixed gas dilution and its control method. The device includes a turbocharger compressor, an electric supercharger, an air intake heater, and an air intake intercooler connected in sequence through an intake manifold. One end of the EGR pipeline communicates with the intake manifold between the intake heater and the intake air intercooler, and the other end is connected to the EGR unit in turn. Directional valve, electronically controlled EGR valve, EGR intercooler and the part where the exhaust pipe is connected to the exhaust port of the cylinder; the polymethoxy dimethyl ether direct injection injector is installed in the cylinder, and the exhaust pipe is connected to the cylinder in turn The exhaust port, exhaust gas turbine, exhaust oxygen sensor and three-way catalytic converter; the intake valve late closing device is installed on the cylinder head, and the cylinder pressure sensor is installed in the cylinder. The device and the method are adopted to maintain ultra-low nitrogen oxide and soot emission while improving the fuel consumption rate.

Description

Equivalent combustion system and control method based on mixture gas dilution

technical field

The invention relates to the field of internal combustion engines, in particular to an equivalence ratio combustion system based on mixture gas dilution and a control method thereof.

Background technique

Diesel/gasoline dual-fuel high premixed compression ignition (HPCC) combustion mode uses in-cylinder direct injection of diesel fuel and gasoline fuel injected from the pilot gas channel. Through the coordinated control of fuel chemical activity and concentration stratification, it can be used in a relatively wide range of operating conditions. It partially solves the problem that the diesel engine cannot reduce NO _x and soot at the same time, while maintaining a high thermal efficiency. However, it is impossible to fundamentally break through the defects of low-temperature combustion of diesel engines. Due to the difficulty in controlling the ignition and heat release process, the expansion of large loads is firstly limited by the problem that the combustion rate is too fast and the peak pressure rise rate is too high. If you want to expand the diesel/gasoline dual The large load of fuel HPCC requires a larger proportion of waste recirculation (EGR) to dilute and reduce the compression ratio. However, it is still difficult to cover the full load condition in an actual engine. On the one hand, a large proportion of EGR will bring intake air It is not enough to ensure the demand for fresh air under heavy load conditions, and it will cause smoke emissions and incomplete combustion products to rise sharply. If the demand for air intake volume and dilution is met by increasing the air intake pressurization degree, the problem of an increase in the explosion pressure in the cylinder will arise. Under the current technical conditions and cost constraints, it is difficult to greatly increase the peak explosion pressure limit of the diesel engine. value to meet the requirements of dual-fuel HPCC low-temperature combustion mode, and excessive reduction of compression ratio is not conducive to the performance of small load or high speed conditions. In addition, in the low-load operating area of HPCC, in order to ensure the premixing degree and suppress the average temperature in the cylinder, it is necessary to ensure a certain EGR rate and the ratio of the fuel injection heat value of the port, but the lean mixture and insufficient ignition energy will ensure combustion instability. The lower oxygen concentration is not conducive to the complete oxidation of HC and CO, and the emission of incomplete combustion products is several orders of magnitude higher than that of traditional diesel engines, even under the high-efficiency medium and high load conditions of diesel/gasoline dual-fuel HPCC combustion The efficiency is still more than 2% lower than that of traditional diesel engines. Studies have shown that due to the extremely high emissions of incomplete combustion products, the conversion efficiency of HC and CO in dual-fuel HPCC low-temperature combustion mode of diesel engine oxidation catalysts is almost 0, while the conversion efficiencies of traditional diesel engine combustion modes under the same exhaust temperature conditions are 80% and 100%, respectively. In order to meet the emission requirements of HC and CO, it is necessary to develop a new low-temperature high-efficiency catalytic oxidation reactor for HPCC. It is difficult to meet the increasingly stringent emission regulations for HC/CO, and the realization of efficient and clean combustion in the full load range is still the main technical bottleneck of HPCC.

The concentration and active stratification of the in-cylinder mixture in the dual-fuel HPCC combustion mode are dominated by in-cylinder direct injection, so the physical and chemical properties of the direct injection fuel play an important role in the preparation of the in-cylinder mixture, the control of the combustion process and the generation of emissions. Impact.

Polyoxymethylene dimethyl ether (PODE) is an acetal polymer with dimethoxymethane as the matrix and methyleneoxy as the main chain. The average cetane number of polyoxymethylene dimethyl ether (PODE) can reach more than 76, which is higher than that of traditional diesel fuel (cetane number ~ 50); its volatility is lower than that of methanol and dimethyl ether, and higher than that of diesel fuel. And the physical properties can be made closer to diesel by adjusting the ratio of different components; polyoxymethylene dimethyl ether (PODE) has no sulfur and no aromatics, no C-C bond in the molecule, and the oxygen content increases with the increase of the molecular weight, and the oxygen content The mass fraction can reach 45%-48.5%; in addition, polyoxymethylene dimethyl ether (PODE) has good compatibility with most commonly used materials, has no corrosion to engine metal parts, and is environmentally friendly. Because PODE has high oxygen content, low stoichiometric air-fuel ratio, and relatively small amount of air required for complete combustion, it can effectively reduce particulate matter, CO, and HC emissions from diesel engines. It is an ideal diesel alternative fuel or additive. However, the form of pure polyoxyl dimethyl ether (PODE) is difficult to be directly used in traditional diesel engines. About 50%, burning pure polyoxymethylene dimethyl ether (PODE) will significantly increase the volume flow rate of fuel supply, and the unit calorific value requires a longer fuel injection duration, so it is necessary to improve the fuel supply system and fuel injection strategy , which is not conducive to the improvement of engine thermal efficiency and to meet the requirements of power performance; on the other hand, the high cetane number of polyoxymethylene dimethyl ether (PODE) is also not conducive to the organization of the combustion process. However, polyoxymethylene dimethyl ether (PODE) as a direct-injection fuel to achieve dual-fuel HPCC combustion is more practical in diesel engines. For the dual-fuel HPCC combustion mode, since the proportion of direct injection in cylinder is relatively small, even if the heat value ratio of polyoxymethylene dimethyl ether (PODE) in cylinder direct injection reaches 50%, the conventional fuel system can still meet the requirements of PODE. The demand for direct injection of oxydimethylether (PODE), and the increase in the volume of direct injection per unit calorific value also contribute to the stratification of the mixture in the HPCC combustion mode and the control of multiple injection strategies. Oil duration, which helps to enhance the control of the ignition and combustion process. In addition, due to the high oxygen content of polyoxymethylene dimethyl ether (PODE), the stoichiometric air-fuel ratio is low, and the amount of air required for complete combustion is relatively small, so it can effectively reduce the intake demand and achieve a larger proportion of EGR low-temperature combustion At the same time, the high oxygen content and no C-C bond characteristics of polyoxymethylene dimethyl ether (PODE) fuel can reduce particulate matter, CO, and HC emissions under low equivalence ratio conditions, and has the ability to achieve ultra-low carbon smoke emissions under low equivalence ratio conditions ability; on the other hand, the higher cetane number of polyoxymethylene dimethyl ether (PODE) can improve the tolerance of the combustion process to EGR, improve the spontaneous ignition performance and combustion process of the fuel under low equivalence ratio conditions, While significantly reducing NOx and soot emissions while maintaining high thermal efficiency, reducing HC and CO emissions, it can improve the spontaneous ignition and combustion stability of low-temperature combustion under low-load conditions. Therefore, polyoxymethylene dimethyl ether (PODE)/gasoline dual-fuel HPCC has the potential to realize efficient and clean combustion at full load.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art, to provide a real-time online change of the heat value ratio of the two fuel injections according to the working conditions, to adjust the concentration and active stratification of the best mixture required by the working conditions, and to control the combustion At the same time, it can increase the intake air density and realize the controllable intake pressure, improve the thermal efficiency of low and medium loads, and reduce the effective compression ratio. Equivalent combustion system and its control method based on mixture dilution.

The present invention is realized through the following technical solutions:

A kind of equivalent combustion system based on mixed gas dilution of the present invention, comprises turbocharger compressor, electric supercharger, intake heater, intake intercooler, pressure sensor, temperature One end of the EGR pipeline is connected to the intake manifold between the intake heater and the intake air intercooler, and the other end is connected to the EGR check valve and the electronically controlled EGR in turn. valve, EGR intercooler, and the part where the exhaust pipe is connected to the exhaust port of the cylinder, and the turbocharger compressor is coaxially connected with the exhaust gas turbine; In the cylinder, the exhaust pipe is sequentially connected to the exhaust port of the cylinder, the exhaust gas turbine, the exhaust oxygen sensor and the three-way catalytic converter; the intake valve late closing device is installed on the cylinder head, and the cylinder pressure sensor is installed in the cylinder. The output end of the electronic control unit communicates with the electric supercharger, electronically controlled EGR valve, airway fuel injector, intake valve late closing device, polymethoxy dimethyl ether direct injection fuel injector, exhaust oxygen sensor and The cylinder pressure sensor is connected.

A control method for an equivalent combustion system based on mixture gas dilution, comprising the following steps:

Step 1. The engine electronic control unit respectively reads the speed signal of the sensor installed on the engine crankshaft and the position signal of the sensor installed on the accelerator pedal, and judges the load of the engine according to the read signals;

Step 2. If the judgment result of step 1 is the cold start and idling condition, then use the polyoxyl dimethyl ether direct injection injector to perform 100% polyoxyl dimethyl ether in-cylinder direct injection;

Step 3. If the result of step 1 is the light load condition, the electronic control unit reads the calibrated MAP, and then outputs a control signal to the PDM direct injection injector to inject the PDM The angle is controlled in the AATDC range of -20～-40°C, and the pulse width control signal is output to the airway injector and polymethoxy dimethyl ether direct injection injector to control the proportion of the airway injection calorific value between 50% and 70% % range, according to the exhaust oxygen concentration signal of the exhaust oxygen sensor to judge the dilution of combustion in the cylinder, change the EGR rate by adjusting the EGR valve to control the concentration of the mixture in the cylinder so that the equivalence ratio is equal to 1;

Step 4. If the judgment result of step 1 is the medium load condition, the electronic control unit reads the calibration MAP, adopts the early injection strategy of polyoxymethylene dimethyl ether, and controls the injection angle within the range of -45～-90℃CA ATDC, and Output pulse width control signals to the airway fuel injector and polyoxymethylene dimethyl ether direct injection injector to control the ratio of the heat value of the airway injection within the range of 75% to 95%, and the electronic control unit adjusts the EGR valve to control the EGR The rate is controlled within the range of 40-50%. The electronic control unit judges the dilution of combustion in the cylinder according to the exhaust oxygen concentration signal of the exhaust oxygen sensor. By adjusting the supercharging degree of the electric supercharger connected in series with the turbocharger The gas mixture concentration in the cylinder is controlled at an equivalence ratio equal to 1;

Step 5. If the judgment result of step 1 is a heavy load condition, the electronic control unit reads the calibrated MAP, adopts the late injection strategy of polyoxymethylene dimethyl ether, and controls the injection angle within the range of -5～-20℃ CA ATDC, and Output pulse width control signals to the airway fuel injector and polyoxymethylene dimethyl ether direct injection injector to control the proportion of the airway injection calorific value within the range of 50% to 80%; the electronic control unit adjusts the EGR valve to control the EGR At the same time, the electronic control unit judges the dilution of combustion in the cylinder according to the exhaust oxygen concentration signal of the exhaust oxygen sensor, improves the supercharging capacity of the electric supercharger, and reduces the concentration of the mixed gas in the cylinder Control the equivalence ratio to be equal to 1, and the electronic control unit adjusts the late closing angle of the intake valve by controlling the late closing device of the intake valve according to the cylinder pressure signal output by the cylinder pressure sensor, reduces the effective compression ratio, and controls the peak cylinder pressure within a limit. within the value.

Compared with the prior art, the present invention has the following three advantages:

First, through different direct injection fuel injection modes under different working conditions, efficient and clean combustion can be realized in a wide range of working conditions, and ultra-low nitrogen oxides and soot emissions can be maintained while improving fuel consumption.

Second, through the combination of supercharging and EGR under different working conditions to dilute the intake charge, it can effectively reduce the maximum temperature in the cylinder and control the combustion rate. In order to meet the demand for fresh air intake under heavy load conditions, the intake pressure and intake air volume are increased by controlling the boosting capacity of the electric supercharger connected in series with the turbocharger.

Third, by controlling different direct injection injection timings to flexibly control the concentration stratification and activity stratification of the fuel, the dual-fuel high premixed compression ignition strategy can ensure high combustion efficiency and low fuel consumption under different operating conditions. nitrogen oxide and soot emissions.

Fourth, in the range of all working conditions, by controlling the overall charge concentration of the mixture in the cylinder to the stoichiometric equivalent (that is, the excess air coefficient λ=1), it is allowed to use a cheap and efficient three-way catalytic converter on the diesel engine to treat HC/CO , to achieve efficient and clean combustion.

Fifth, by adopting the variable intake valve technology, a higher geometric compression ratio can be adopted, and the effective compression ratio can be reduced by adopting the late intake valve closing technology as the load increases. On the one hand, the thermal efficiency of small and medium loads is improved, on the other hand Expanded the range of heavy load operating conditions.

Description of drawings

Fig. 1 is a schematic structural diagram of an equivalent combustion system based on mixture dilution in the present invention.

detailed description

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Fig. 1, a kind of equivalent combustion system based on mixed gas dilution of the present invention comprises turbocharger compressor 1, electric supercharger 2, intake heater 3, Intake intercooler 5, pressure sensor P, temperature sensor T, airway fuel injector 8 and the air intake port of the cylinder, the inlet between one end of the EGR pipeline 14 and the intake heater 3 and the intake intercooler 5 The airway main pipe 6 communicates and the other end is connected to the EGR one-way valve 4, the electronically controlled EGR valve 7, the EGR intercooler 9 and the part where the exhaust pipe 17 is connected to the exhaust port of the cylinder in sequence. The turbocharger The compressor 1 is coaxially connected with the exhaust gas turbine 15; the polyoxyl dimethyl ether (PODE) direct injection fuel injector 11 is installed in the cylinder, and the exhaust pipe 18 is sequentially connected to the exhaust port of the cylinder, the exhaust gas turbine 15, the exhaust gas An oxygen sensor 16 and a three-way catalytic converter 17; an intake valve late closing device 10 is installed on the cylinder head, and a cylinder pressure sensor 13 is installed in the cylinder.

The output end of the electronic control unit 12 communicates with the electric supercharger 2, the electronically controlled EGR valve 7, the airway fuel injector 8, the intake valve late closing device 10, and the direct injection of polyoxymethylene dimethyl ether (PODE) through the control line. Oil tank 11, exhaust gas oxygen sensor 16 and cylinder pressure sensor 13 are connected.

The flow rate of the intercooled exhaust gas recirculation exhaust gas is controlled by the electronically controlled EGR valve 7 , and an EGR check valve 4 is installed behind the electronically controlled EGR valve 7 in order to prevent backflow of fresh intake air. Intake supercharging is achieved by a turbocharger compressor 1 connected in series with an electric supercharger 2 to achieve two-stage supercharging.

A kind of control method of the equivalence combustion system based on mixed gas dilution of the present invention, comprises the following steps:

Step 1, the engine electronic control unit 12 respectively reads the speed signal of the sensor installed on the crankshaft of the engine, the position signal of the sensor installed on the accelerator pedal, and judges the load of the engine according to the read signals;

Step 2. If the judgment result of step 1 is cold start and idling condition, use polyoxyl dimethyl ether (PODE) direct injection injector 11 to carry out 100% polyoxyl dimethyl ether (PODE) in-cylinder Direct injection;

Step 3: If the judgment result of step 1 is a small load condition, the electronic control unit 12 reads the calibration MAP, and then outputs a control signal to the polyoxymethylene dimethyl ether (PODE) direct-injection injector 11, and the PODE The injection angle of PODE is controlled within the range of -20～-40°C ATDC (that is, -20～-40 degrees crankshaft angle after top dead center), and the injector 8 and polymethoxy PODE direct injection injector 11 outputs a pulse width control signal to control the ratio of the heat value of the airway injection (that is, the ratio of the heat value of the fuel injected by the airway injector 8 to the total heat value of the fuel entering the cylinder) In the range of 50% to 70%. According to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16, the dilution of combustion in the cylinder is judged, and the EGR rate is changed by adjusting the EGR valve 7 to control the concentration of the mixture in the cylinder so that the equivalence ratio is equal to 1;

Step 4. If the judgment result of step 1 is a medium load condition, the electronic control unit 12 reads the calibration MAP, adopts the early injection strategy of polyoxymethylene dimethyl ether (PODE), and controls the injection angle at -45～-90°C ATDC range, and output a pulse width control signal to the airway injector 8 and polyoxyl dimethyl ether (PODE) direct injection injector 11 to adjust the proportion of the airway injection calorific value (that is, the ratio of the airway injector 8 injection The ratio of the calorific value of the fuel to the total calorific value of the fuel entering the cylinder) is controlled within the range of 75% to 95%. The electronic control unit 12 controls the EGR rate within the range of 40-50% by adjusting the EGR valve 7. The electronic control unit 12 judges the dilution of combustion in the cylinder according to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16. The supercharging degree of the electric supercharger 2 connected in series with the compressor controls the concentration of the gas mixture in the cylinder so that the equivalence ratio is equal to 1;

Step 5. If the judgment result of step 1 is a heavy load condition, the electronic control unit 12 reads the calibration MAP, adopts the late injection strategy of polyoxymethylene dimethyl ether (PODE), and controls the injection angle at -5 ~ -20°C ATDC range, and output a pulse width control signal to the airway injector 8 and polyoxyl dimethyl ether (PODE) direct injection injector 11 to adjust the proportion of the airway injection calorific value (that is, the ratio of the airway injector 8 injection The ratio of the calorific value of the fuel to the total calorific value of the fuel entering the cylinder) is controlled within the range of 50% to 80%; the electronic control unit 12 reduces the EGR rate to within the range of 30% to 40% by adjusting the EGR valve 7, and at the same time the electric The control unit 12 judges the dilution of combustion in the cylinder according to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16, increases the supercharging capacity of the electric supercharger 2, and controls the concentration of the mixture in the cylinder so that the equivalence ratio is equal to 1. And the electronic control unit 12 adjusts the late closing angle of the intake valve by controlling the late closing device 10 of the intake valve according to the cylinder pressure signal output by the cylinder pressure sensor 13 , reduces the effective compression ratio, and controls the peak cylinder pressure within the limit value. Different engines have different limits, generally at 16MPa. The method for adjusting the late-closing angle of the intake valve by the intake valve late-closing device 10 can be specifically referred to: Hu Wang, Laihui Tong, ZunqingZheng, Mingfa Yao. Experimental Study on High-load Extension of Gasoline/PODE Dual-fuel RCCI Operation Using LateIntake ValveClosing.SAE Paper2017-01-0754, 2017. ("Wang Hu, Tong Laihui, Zheng Zunqing, Yao Mingfa. Experimental research on gasoline/PODE dual-fuel RCCI large-load expansion based on late intake valve closing strategy. SAE paper 2017-01- 0754, 2017.").

Example 1

In this embodiment, an engine with a high geometric compression ratio (18:1) is used, the direct injection fuel in the cylinder is polyoxymethylene dimethyl ether (PODE), and commercial gasoline with an RON octane value of 95 is injected into the airway.

Step 1, the engine electronic control unit 12 respectively reads the speed signal of the sensor installed on the crankshaft of the engine, the position signal of the sensor installed on the accelerator pedal, and judges the load of the engine according to the read signals;

Step 2. If the judgment result of step 1 is cold start and idling condition, use polyoxyl dimethyl ether (PODE) direct injection injector 11 to carry out 100% polyoxyl dimethyl ether (PODE) in-cylinder Direct injection;

Step 3. If the judgment result of step 1 is a small load condition: the speed is 1500r/min, the load is 0.20MPaIMEP, the electronic control unit 12 reads the calibration MAP, and then outputs a control signal to the polyoxymethylene dimethyl ether (PODE) to directly Inject the fuel injector 11, control the injection angle of polyoxymethylene dimethyl ether (PODE) in the range of -40°C ATDC, and directly inject into the airway injector 8 and polyoxymethylene dimethyl ether (PODE) The fuel injector 11 outputs a pulse width control signal to control the ratio of the heat value of the port injection (that is, the ratio of the heat value of the fuel injected by the port injector 8 to the total heat value of the fuel entering the cylinder) at 50%. According to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16, the dilution of combustion in the cylinder is judged, and the EGR rate is changed by adjusting the EGR valve 7 to control the concentration of the mixture in the cylinder so that the equivalence ratio is equal to 1;

Step 4. If the judgment result of step 1 is a medium load condition: the speed is 1500r/min, the load is 0.8MPaIMEP, the electronic control unit 12 reads the calibration MAP, adopts the early injection strategy of polyoxymethylene dimethyl ether (PODE), and injects The angle is controlled in the -45°C ATDC range, and the pulse width control signal is output to the airway injector 8 and the polyoxyl dimethyl ether (PODE) direct injection injector 11 to control the ratio of the heat value of the airway injection (that is, the gas The ratio of the calorific value of the fuel injected by the fuel injector 8 to the total calorific value of the fuel entering the cylinder) is controlled at 75%. The electronic control unit 12 controls the EGR rate at 40% by adjusting the EGR valve 7. The electronic control unit 12 judges the dilution of combustion in the cylinder according to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16. The supercharging degree of the electric supercharger 2 controls the concentration of the mixture gas in the cylinder so that the equivalence ratio is equal to 1;

Step 5. If the judgment result of step 1 is a heavy load condition: the speed is 1500r/min, the load is 1.3MPaIMEP, the electronic control unit 12 reads the calibration MAP, adopts the late injection strategy of polyoxymethylene dimethyl ether (PODE), and injects The angle is controlled in the range of -20°C ATDC, and the pulse width control signal is output to the airway injector 8 and the polyoxyl dimethyl ether (PODE) direct injection injector 11 to control the proportion of the heat value of the airway injection (i.e. gas The ratio of the heat value of the fuel injected by the fuel injector 8 to the total heat value of the fuel entering the cylinder) is controlled at 80%; the electronic control unit 12 controls the EGR rate at 40% by adjusting the EGR valve 7, and the electronic control unit 12 According to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16, the dilution of the combustion in the cylinder is judged, the supercharging capacity of the electric supercharger 2 is increased, and the concentration of the mixture in the cylinder is controlled at an equivalence ratio equal to 1. And the electronic control unit 12 delays the intake valve late closing angle by 25°CA by controlling the intake valve late closing device 10 according to the cylinder pressure signal output by the cylinder pressure sensor 13, reduces the effective compression ratio, and controls the peak cylinder pressure at 1.6 Within MPa.

After testing, under the working conditions of the embodiment of the present invention, the combustion mode design method can be used to achieve different mixture activity and concentration stratification under different loads, control the combustion rate, and control the intake pressure at full load through EGR coupling In the range of working conditions, by controlling the equivalence ratio to be equal to 1, the use of a three-way catalytic converter can achieve efficient and clean combustion.

Example 2

In this embodiment, an engine with a high geometric compression ratio (18:1) is used, the direct injection fuel in the cylinder is polyoxymethylene dimethyl ether (PODE), and commercial gasoline with an RON octane value of 95 is injected into the airway.

Step 1, the engine electronic control unit 12 respectively reads the speed signal of the sensor installed on the crankshaft of the engine, the position signal of the sensor installed on the accelerator pedal, and judges the load of the engine according to the read signals;

Step 2. If the judgment result of step 1 is cold start and idling condition, use polyoxyl dimethyl ether (PODE) direct injection injector 11 to carry out 100% polyoxyl dimethyl ether (PODE) in-cylinder Direct injection;

Step 3. If the judgment result of step 1 is a small load condition: the speed is 1500r/min, the load is 0.35MPaIMEP, the electronic control unit 12 reads the calibration MAP, and then outputs the control signal to the polyoxymethylene dimethyl ether (PODE) directly. Inject the fuel injector 11, control the injection angle of polyoxymethylene dimethyl ether (PODE) in the range of -30°C AATDC, and directly inject oil to the airway injector 8 and polyoxymethylene dimethyl ether (PODE) The controller 11 outputs a pulse width control signal to control the port injection heating value ratio (ie the ratio of the heating value of the fuel injected by the port injector 8 to the total heating value of the fuel entering the cylinder) at 65%. According to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16, the dilution of combustion in the cylinder is judged, and the EGR rate is changed by adjusting the EGR valve 7 to control the concentration of the mixture in the cylinder so that the equivalence ratio is equal to 1;

Step 4. If the judgment result of step 1 is a medium load condition: the speed is 1500r/min, the load is 1.0MPaIMEP, the electronic control unit 12 reads the calibration MAP, adopts the polyoxymethylene dimethyl ether (PODE) early injection strategy, and injects The angle is controlled in the CA ATDC range of -60°C, and a pulse width control signal is output to the airway injector 8 and the polyoxyl dimethyl ether (PODE) direct injection injector 11 to control the proportion of the heat value of the airway injection (i.e. gas The ratio of the calorific value of the fuel injected by the fuel injector 8 to the total calorific value of the fuel entering the cylinder) is controlled at 85%. The electronic control unit 12 controls the EGR rate at 45% by adjusting the EGR valve 7. The electronic control unit 12 judges the dilution of combustion in the cylinder according to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16. The supercharging degree of the electric supercharger 2 controls the concentration of the mixture gas in the cylinder so that the equivalence ratio is equal to 1;

Step 5. If the judgment result of step 1 is a heavy load condition: the speed is 1500r/min, and the load is 1.6MPaIMEP. The angle is controlled in the range of -15°C ATDC, and the pulse width control signal is output to the airway injector 8 and the polyoxyl dimethyl ether (PODE) direct injection injector 11 to control the ratio of the heat value of the airway injection (i.e. gas The ratio of the calorific value of the fuel injected by the fuel injector 8 to the total calorific value of the fuel entering the cylinder) is controlled at 70%; the electronic control unit 12 reduces the EGR rate to 35% by adjusting the EGR valve 7, and the electronic control unit 12 According to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16, the dilution of the combustion in the cylinder is judged, the supercharging capacity of the electric supercharger 2 is increased, and the concentration of the mixture in the cylinder is controlled at an equivalence ratio equal to 1. In addition, the electronic control unit 12 delays the closing angle of the intake valve by 35°CA by controlling the intake valve late closing device 10 according to the cylinder pressure signal output by the cylinder pressure sensor 13, reduces the effective compression ratio, and controls the peak cylinder pressure at 1.6MPa within.

After testing, under the working conditions of the embodiment of the present invention, the combustion mode design method can be used to achieve different mixture activity and concentration stratification under different loads, control the combustion rate, and control the intake pressure through EGR coupling By controlling the equivalence ratio to 1 in the full load range, the three-way catalytic converter can realize efficient and clean combustion.

Example 3

In this embodiment, an engine with a high geometric compression ratio (18:1) is used, the direct injection fuel in the cylinder is polyoxymethylene dimethyl ether (PODE), and commercial gasoline with an RON octane value of 95 is injected into the airway.

Step 1, the engine electronic control unit 12 respectively reads the speed signal of the sensor installed on the crankshaft of the engine, the position signal of the sensor installed on the accelerator pedal, and judges the load of the engine according to the read signals;

Step 2. If the judgment result of step 1 is cold start and idling condition, use polyoxyl dimethyl ether (PODE) direct injection injector 11 to carry out 100% polyoxyl dimethyl ether (PODE) in-cylinder Direct injection;

Step 3. If the judgment result of step 1 is a small load condition: the speed is 1500r/min, the load is 0.5MPaIMEP, the electronic control unit 12 reads the calibration MAP, and then outputs a control signal to the polyoxymethylene dimethyl ether (PODE) to directly Inject the fuel injector 11, control the injection angle of polyoxymethylene dimethyl ether (PODE) in the range of -20°C AATDC, and directly inject oil to the airway injector 8 and polyoxymethylene dimethyl ether (PODE) The controller 11 outputs a pulse width control signal to control the port injection heating value ratio (ie the ratio of the heating value of the fuel injected by the port injector 8 to the total heating value of the fuel entering the cylinder) at 70%. According to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16, the dilution of combustion in the cylinder is judged, and the EGR rate is changed by adjusting the EGR valve 7 to control the concentration of the mixture in the cylinder so that the equivalence ratio is equal to 1;

Step 4. If the judgment result of step 1 is a medium load condition: the speed is 1500r/min, the load is 1.2MPaIMEP, the electronic control unit 12 reads the calibration MAP, adopts the early injection strategy of polyoxymethylene dimethyl ether (PODE), and injects The angle is controlled in the range of -90°C ATDC, and the pulse width control signal is output to the airway injector 8 and the polyoxymethylene dimethyl ether (PODE) direct injection injector 11 to control the ratio of the heat value of the airway injection (i.e. gas The ratio of the calorific value of the fuel injected by the fuel injector 8 to the total calorific value of the fuel entering the cylinder) is controlled at 95%. The electronic control unit 12 controls the EGR rate at 50% by adjusting the EGR valve 7. The electronic control unit 12 judges the dilution of combustion in the cylinder according to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16. The supercharging degree of the electric supercharger 2 controls the concentration of the mixture gas in the cylinder so that the equivalence ratio is equal to 1;

Step 5. If the judgment result of step 1 is a heavy load condition: the speed is 1500r/min, and the load is 1.8MPaIMEP. The angle is controlled in the -5°C ATDC range, and the pulse width control signal is output to the airway injector 8 and the polyoxyl dimethyl ether (PODE) direct injection injector 11 to control the ratio of the heat value of the airway injection (that is, the gas The ratio of the heat value of the fuel injected by the fuel injector 8 to the total heat value of the fuel entering the cylinder) is controlled at 50%; the electronic control unit 12 reduces the EGR rate to 30% by adjusting the EGR valve 7, and the electronic control unit 12 According to the exhaust oxygen concentration signal of the exhaust oxygen sensor 16, the dilution of the combustion in the cylinder is judged, the supercharging capacity of the electric supercharger 2 is increased, and the concentration of the mixture in the cylinder is controlled at an equivalence ratio equal to 1. And the electronic control unit 12 delays the closing angle of the intake valve by 55°CA by controlling the intake valve late closing device 10 according to the cylinder pressure signal output by the cylinder pressure sensor 13, reduces the effective compression ratio, and controls the peak cylinder pressure at 1.6MPa within.

After testing, under the working conditions of the embodiment of the present invention, the combustion mode design method can be used to achieve different mixture activity and concentration stratification under different loads, control the combustion rate, and control the intake pressure at full load through EGR coupling In the range of working conditions, by controlling the equivalence ratio to be equal to 1, the use of a three-way catalytic converter can achieve efficient and clean combustion.

Although the present invention has been described above with reference to the schematic diagrams, the present invention is not limited to the above-mentioned specific embodiments, and the above descriptions are only illustrative and not restrictive. Under the enlightenment of the present invention, those skilled in the art can also carry out multiple deformations (such as direct injection of oxygen-containing biodiesel in the engine cylinder, etc., airway injection of alcohol fuel, natural gas, etc.) etc.), these all belong to the protection of the present invention.

Claims (2)

1. a kind of equivalent combustion system based on air-fuel mixture enleanment, it is characterised in that：Including being sequentially connected by air intake duct house steward Turbocharger air compressor, electric booster, air intake heater, air intake intercooler, pressure sensor, temperature sensor, gas The air inlet of road fuel injector and cylinder, EGR line one end and air intake duct house steward's phase between air intake heater, air intake intercooler The logical and other end is sequentially connected EGR check valves, electric control EGR valve, EGR charge air coolers and blast pipe and is connected with the exhaust outlet of cylinder The part connect, described turbocharger air compressor is coaxially connected with exhaust gas turbine；Polymethoxy dimethyl ether direct-injection fuel injector is pacified In cylinder, blast pipe is sequentially connected exhaust outlet, exhaust gas turbine, exhaust gas oxygen sensor and the triple-effect catalytic unit of cylinder；In vapour Inlet valve evening pass device is installed on cylinder cap, cylinder pressure sensor is installed in cylinder, ECU output end passes through control line Device, polymethoxy dimethyl ether direct-injection fuel injector, row are closed with electric booster, electric control EGR valve, air flue fuel injector, inlet valve evening Gas lambda sensor and cylinder pressure sensor are connected.

2. a kind of control method of the equivalent combustion system based on air-fuel mixture enleanment of use claim 1, comprises the following steps：

Step 1: engine electric-controlled unit reads on engine crankshaft the tach signal of sensor, installed in oil respectively Door pedal on sensor position signalling and according to the signal read judge engine operation load；

If Step 2: the judged result of step one is cold start-up and idling operation, using the spray of polymethoxy dimethyl ether direct-injection Oily device carries out 100% polymethoxy dimethyl ether in-cylinder direct-jet；

Step 3: if the judged result of step one is small load condition, ECU reads demarcation MAP, then output control Signal gives polymethoxy dimethyl ether direct-injection fuel injector, by the control of polymethoxy dimethyl ether spray angle in -20~-40 °C of A ATDC Scope, and to air flue fuel injector and polymethoxy dimethyl ether direct-injection fuel injector output pulse width control signal by gas-duct jetting calorific value ratio Example control judges the dilution feelings of in-cylinder combustion according to the density of oxygen contained in discharged gas signal of exhaust gas oxygen sensor in the range of 50%~70% Condition, controls in-cylinder mixture strength to be equal to 1 in equivalent proportion by adjusting EGR valve change EGR rate；

Step 4: if the judged result of step 1 is moderate duty operating mode, ECU reads demarcation MAP, using polymethoxy The early spray strategy of dimethyl ether, spray angle is controlled in -45~-90 °C of A ATDC scopes, and to air flue fuel injector and polymethoxy two Methyl ether direct-injection fuel injector output pulse width control signal controls gas-duct jetting calorific value ratio in the range of 75%~95%, automatically controlled list Member is controlled EGR rate in the range of 40-50% by adjusting EGR valve, and ECU is dense according to the exhaust oxygen of exhaust gas oxygen sensor Degree signal judges the dilution situation of in-cylinder combustion, and the supercharging level of the electric booster connected by adjustment with turbocharger is by cylinder Interior mixture strength control is equal to 1 in equivalent proportion；

Step 5: if the judged result of step 1 is high load working condition, ECU reads demarcation MAP, using polymethoxy two Methyl ether evening spray strategy, spray angle is controlled in -5~-20 °C of A ATDC scopes, and to air flue fuel injector and polymethoxy dimethyl ether Direct-injection fuel injector output pulse width control signal controls gas-duct jetting calorific value ratio in the range of 50%~80%；ECU leads to Overregulate EGR valve EGR rate is reduced in the range of 30%-40%, while exhaust oxygen of the ECU according to exhaust gas oxygen sensor Concentration signal judges the dilution situation of in-cylinder combustion, the boosting capability of electric booster is improved, by in-cylinder mixture strength control It is equal to 1 in equivalent proportion, and the cylinder that ECU is exported according to cylinder pressure sensor presses signal, by controlling inlet valve evening to close device Inlet valve evening pass angle is adjusted, effective compression ratio is reduced, by peak in-cylinder pressure control within limit value.