CN106545426A - A kind of control method of partial pre-mix compression ignition combustion electromotor - Google Patents

Abstract

The invention discloses a control method of a partially premixed compression ignition combustion engine. The ECU judges the load of the engine; when the engine is cold started, the fuel injector in the cylinder is controlled to work independently; The fuel injector works alone, and the opening time of the intake valve is controlled to be greatly advanced, and the hot exhaust gas is used to lead back to the vicinity of the intake port to heat the intake port; under medium load conditions, the fuel injector of the intake manifold and the in-cylinder fuel injector are controlled All work normally, when the load increases, adjust the ratio of the premixed gas mixture, control the fuel injected by the intake manifold injector to gradually decrease, and the fuel injected by the in-cylinder injector gradually increase; when the load is high, The in-cylinder fuel injector is controlled to work independently to achieve maximum knock control effect; in addition, the ECU controls the working condition of the spark plug, which not only ensures the engine starts quickly and reduces knock, but also obtains higher thermal efficiency.

Description

A Control Method of Partially Premixed Compression Ignition Combustion Engine

technical field

The invention relates to the technical field of internal combustion engines, in particular to a control method for a partially premixed compression ignition combustion engine with mixed injection of gasoline intake port injection and in-cylinder direct injection.

Background technique

The massive consumption of energy has caused a series of serious problems such as environmental pollution and global climate change. Especially in urban areas, various air pollutants (such as PM and NOx) emitted by engines have brought many negative effects on human health and the environment. . In mid-2012, the number of cars in China had increased to 114 million. Whether it is air pollution or the energy crisis, China is facing a more severe test than other countries on environmental, climate and energy issues. With the continuous strengthening of the world's emission regulations, reducing pollutant emissions has also become an important issue. Therefore, the internal combustion engine faces a huge challenge.

Before the 1990s, the fuel supply method of most gasoline engines has always been the "extra-cylinder mixing" method, that is, gasoline is sprayed into the intake manifold through the fuel injector, and mixed with fresh air in the intake manifold. The mixed gas is mixed to form a mixed gas. Before the intake valve of the engine cylinder is opened, the mixed gas is stored in the intake manifold, and the mixed gas cannot enter the combustion chamber due to the negative pressure of the combustion chamber until the valve is opened. The disadvantage of this "external cylinder mixing" is obvious. The mixed gas entering the combustion chamber can only be passively controlled by opening and closing the valve, and the adaptability to different working conditions of the engine is not ideal, and the response speed is not fast enough. Moreover, there is a certain distance between the fuel injector and the combustion chamber, the mixing of gasoline and air is greatly affected by the intake air flow, and tiny oil particles will be adsorbed on the pipe wall, which cannot be fully utilized.

In order to achieve high efficiency and clean combustion of internal combustion engines, many advanced combustion concepts have been developed, such as the GDI engine with in-cylinder direct injection lean combustion technology. Different from the traditional port injection engine, the GDI engine injects gasoline directly into the cylinder through the fuel injector at an appropriate crank angle, and realizes stratified combustion through reasonable organization of the airflow in the cylinder, while taking into account the diesel engine The advantages of high thermal efficiency and high power per gasoline engine, but in the face of increasingly stringent emission regulations, the main technical difficulty restricting the development of GDI engines is the emission problem, such as when the load is small and medium, due to the use of stratified mixed gas, the flame will flow from the rich area Extinguishing towards the lean zone, the working condition of lean air-fuel ratio causes the temperature in the cylinder to be low, which is also not conducive to the subsequent continued oxidation of unburned hydrocarbons. The combustion system organized in a long-distance way has more unburned hydrocarbons because the spray hits more walls, and the temperature of the piston top and cylinder wall is low. Insufficient mixing of the mixture and flame delay caused by other improper design will also cause the flame propagation speed to decrease, resulting in high emissions of unburned hydrocarbons. Moreover, the fuel of the GDI gasoline engine is directly injected into the cylinder, and the phenomenon of fuel collision occurs from time to time. In addition, the fuel atomization time is short, resulting in insufficient mixing of fuel and air before combustion, and there is a local rich mixture area, so the soot emission increases significantly. The development of the GDI engine still has the following technical difficulties: it is difficult to control the organization and combustion of the stratified mixture within the range required by the theory; the injection strategy required for the smooth transition of the load when the working conditions change is relatively complicated, etc. Fig. 1 is the structural schematic diagram of the part premixed compression ignition combustion engine of existing gasoline port injection and in-cylinder direct injection mixed injection, intake manifold injector 3 is installed on the intake manifold 4, in-cylinder injection The oiler 2 is installed on the cylinder 6, and the spark plug 1 is installed on the cylinder. There is currently no systematic control method for the device.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a control method for a partially premixed compression ignition combustion engine. According to the operating conditions of different working conditions, either the simple direct injection operation in the cylinder or the combined operation of the two systems are adopted. , to maximize the respective advantages of in-cylinder direct injection and port injection.

In order to achieve the above object, a control method of a partially premixed compression ignition combustion engine of the present invention comprises the following steps:

(1) In the working condition of engine cold start, the electronic control unit controls the intake manifold injector installed on the intake manifold to close, controls the in-cylinder injector to inject fuel, and the fuel injected by the in-cylinder injector Mixed with the air flowing into the intake manifold and ignited by the spark plug;

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

(3) If the result of the judgment in step (2) is the light load condition, the electronic control unit controls the in-cylinder injector to close, and the intake manifold injector injects fuel. In addition, the electronic control unit controls the cylinder exhaust stroke The intake valve is opened in the middle, the exhaust valve is opened near the bottom dead center of the exhaust, and closed near the top dead center of the exhaust; at the same time, the electronic control unit controls the spark plug to not work;

(4) If the judgment result in step (2) is the medium load condition, the electronic control unit controls both the intake manifold injector and the in-cylinder injector to inject fuel, and the gas mixture in the cylinder consists of two parts, one part It is the homogeneous mixture formed by the pre-mixing of the fuel injected by the intake manifold injector, and the other part is the fuel injected by the in-cylinder injector. When the load of the engine is increased, the uniformity of the mixture in the cylinder is controlled. The proportion of air-to-air mixture is reduced. In addition, the electronic control unit controls the spark plug to not work;

(5) If the result of the judgment in step (2) is the high-load condition, the electronic control unit controls the intake manifold injector to close, controls the in-cylinder injector to inject fuel, and the fuel injected by the in-cylinder injector The air flowing into the intake manifold is mixed, and in addition, the electronic control unit controls the spark plug to ignite the mixture.

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

First, according to the operating conditions of different working conditions, either a simple direct injection operation or a combination of the two systems is used to maximize the respective advantages of direct injection in cylinder and port injection. In addition, the control of spark plug Working conditions: cold start and high load work, small load and medium load do not work, not only to ensure rapid engine start and reduce knocking, but also to obtain higher thermal efficiency.

Second, when the load is small, the hot exhaust gas is used to lead back to the vicinity of the intake port to heat the intake port, and the fuel reforming process is performed on the mixture gas in the intake port. The high-temperature exhaust gas heats the mixture gas in the intake port, which will produce some incomplete combustion. Hydrocarbons and some active atomic groups can reduce the self-ignition temperature of the mixture, promote combustion in the cylinder at low load, and further reduce the unburned hydrocarbon content. Third, at medium loads, as the load changes, optimize the injection ratio to adapt to the load change, and adjust the ratio of the pre-mixed gas mixture; when the engine load increases, the ratio of the pre-mixed gas mixture controlled to The fuel injected by the injector gradually decreases, while the fuel injected by the in-cylinder injector gradually increases. As the load increases, the fuel supply system of the engine is changed from intake pipe injection to in-cylinder injection, which shortens the response time, provides a rich mixture, and better meets the requirements of different working conditions for the concentration of the engine mixture.

Description of drawings

Fig. 1 is a structural schematic diagram of an existing partially premixed compression ignition combustion engine.

Fig. 2 is a control schematic diagram of the control method of the partial premixed compression ignition combustion engine of the present invention.

Labeled in the figure:

Spark plug 1, in-cylinder injector 2, intake manifold injector 3, intake manifold 4, intake valve 5, cylinder 6, exhaust valve 7.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

According to the control method of a partly premixed compression ignition combustion engine of the present invention, according to the operating conditions of different working conditions, either simple in-cylinder direct injection operation or combined operation of two systems is used to maximize the use of in-cylinder direct injection and port injection have their respective advantages.

A control method of a partially premixed compression ignition combustion engine of the present invention as shown in the accompanying drawings, comprising the following steps:

(1) In the working condition of engine cold start, the electronic control unit ECU controls the intake manifold injector 3 installed on the intake manifold to close, controls the in-cylinder injector 2 to inject fuel, and the in-cylinder injector The injected fuel mixes with the air flowing into the intake manifold and ignites the mixture in the cylinder by the spark plug 1;

During this process, the fuel injected by the in-cylinder injector 2 is mixed with the air flowing in from the intake manifold 4, and the movement of the vortex is used to propagate the mixture. By simply relying on the fuel injection in the cylinder, the gasoline with a better atomization degree can be obtained, and it can be started quickly. And if it is injected in the intake manifold 4, the fuel is sprayed on the back of the intake valve 5 and the wall near the intake port. The evaporation of gasoline and the mixing with air mainly depend on the high temperature of the wall. Low, the evaporation rate of gasoline is slow, and the mixture of oil and gas is seriously uneven, and the engine can only be started by relying on excessive fuel supply to obtain a richer mixture, which results in high HC emissions when starting at low temperature. Therefore, in-cylinder fuel injection is used during cold start. The quality of oil-air mixture mainly depends on the spray of in-cylinder fuel injector 2 and the air movement in the cylinder. It does not need to inject a large amount of gasoline like a manifold injection gasoline engine, resulting in a very rich mixture. HC emissions increase. In addition, during cold start, in order to avoid the difficulty of compression ignition due to the low temperature in the cylinder, the electronic control unit ECU controls the spark plug 1 to ignite the mixture in the cylinder.

(2) The electronic control unit ECU reads the speed signal of the sensor installed on the engine crankshaft and the position signal of the sensor installed on the accelerator pedal respectively, and judges the load of the engine according to the read signals.

(3) If the judgment result in step (2) is a light load condition (load mean effective pressure (BMEP) <0.5MPa when the engine is running), the electronic control unit ECU controls the in-cylinder injector 2 to close, and the intake manifold The fuel injector 3 injects fuel. In addition, the electronic control unit ECU controls the cylinder to open the intake valve 5 during the exhaust stroke, and the exhaust valve 7 opens near the exhaust bottom dead center and closes near the exhaust top dead center; at the same time, the electronic The control unit ECU controls the spark plug 1 not to work.

During this process, the in-cylinder fuel injector 2 is closed, and the intake manifold fuel injector 3 injects fuel to make the fuel and air mix for a longer time, forming a more homogeneous mixture. If direct fuel injection is used in the cylinder, the atomization time of the fuel is short, so that the fuel and air cannot be fully mixed before combustion, and there is a local rich mixture area, so the soot emission is significantly increased, and the mixture will cause the flame to flow from the rich area. Extinguishment towards the lean zone, the lean air-fuel ratio working condition causes the temperature in the cylinder to be low, which is also not conducive to the subsequent continuous oxidation of unburned hydrocarbons, and the combustion system organized in a long-distance way has more walls due to the spray, and the piston top and cylinder wall The lower the temperature, the more unburned hydrocarbons are formed. Therefore, a simple port injection method is adopted. In addition, the electronic control unit ECU controls to open the intake valve 5 during the exhaust stroke, and the exhaust valve 7 is the same as that of a traditional gasoline engine, opening near the exhaust bottom dead center and closing near the exhaust top dead center. However, the opening time of the intake valve 5 is greatly advanced. According to needs, it can even be advanced to the middle of the exhaust stroke, so that the exhaust gas can be discharged into the intake port during the exhaust stroke, and then discharged into the intake port during the intake stroke. The exhaust gas in the intake channel is sucked back into the cylinder; the hot exhaust gas is used to lead back to the vicinity of the intake port to heat the intake port. This process can be regarded as a fuel reforming process. The high-temperature exhaust gas heats the mixed gas in the intake port, which will produce some unnecessary Completely burned hydrocarbons and some active atomic groups can reduce the self-ignition temperature of the mixture, promote combustion in the cylinder at low load, and further reduce the unburned hydrocarbon content. In addition, under the condition of light load, the electronic control unit ECU controls the spark plug 1 not to work, and the combustion adopts compression ignition to obtain higher thermal efficiency.

(4) If the judgment result in step (2) is the medium load condition (BMEP: 0.5~1.05MPa), the electronic control unit ECU controls both the intake manifold injector 3 and the in-cylinder injector 2 to inject fuel, The mixed gas in the cylinder 6 is composed of two parts, one part is the homogeneous mixed gas formed by the pre-mixing of the fuel injected by the intake manifold injector 3, and the other part is the fuel injected by the in-cylinder injector 2, when increasing When the engine is under load, the proportion of the homogeneous air-fuel mixture in the air-fuel mixture in the control cylinder 6 is reduced. In addition, the electronic control unit ECU controls the spark plug 1 not to work.

In this step, a part of the mixed gas in the cylinder 6 is a homogeneous mixed gas formed by pre-mixing the fuel injected by the intake manifold injector 3. The atomization and evaporation of the gasoline have a good spread effect, ensuring that the far end of the cylinder will not Flameout occurs; another part of fuel is provided by the in-cylinder injector 2 to form concentration stratification in a small area, which is conducive to the formation and propagation of fire nuclei. Better mixture formation is achieved by port injection and in-cylinder direct injection. This kind of coordinated injection changes the situation that the direct injection medium-rich mixture is the majority in the cylinder, forming a state where the main part of the cylinder is a homogeneous mixture with only a small part of the rich mixture, which basically reaches the value of the theoretical mixture. It solves the problems of soot emission caused by local over-rich mixture and hydrocarbon emission caused by local too-lean, which are easy to occur in direct-injection gasoline engines. As the load changes, the injection ratio should be optimized to adapt to the load change. Adjust the ratio of the premixed gas mixture to achieve the best power and fuel consumption under each load. The ratio of the premixed gas mixture is adjusted by calibrating each engine. ; When the load of the engine is increased, the proportion of the premixed gas mixture is controlled to decrease, the fuel injected by the intake manifold injector 3 gradually decreases, and the fuel injected by the in-cylinder injector 2 gradually increases. As the load increases, the fuel supply system of the engine is changed from intake pipe injection to in-cylinder injection, which shortens the response time, provides a rich mixture, and better meets the requirements of different working conditions for the concentration of the engine mixture. Changing the ratio of in-cylinder direct injection and port injection allows it to obtain better torque and fuel economy than either of the injection methods alone. For example, in the test of air-fuel ratio analysis, the research results show that: 30% in-cylinder direct injection can obtain a more uniform air-fuel mixture than 100% intake port injection, and there is also a certain area of concentration stratified mixture , which is beneficial to compression ignition ignition, and the ignition lag period is shortened, and the combustion speed is accelerated, thereby improving combustion. Therefore, the in-cylinder fuel injector 2 and the intake manifold fuel injector 3 work together for injection in the middle load, in order to inject a certain amount of fuel required under different working conditions, so as to obtain a better combustion mixture and complete combustion , to achieve the lowest emission of pollutants. In addition, under medium load conditions, the electronic control unit ECU controls the spark plug 1 not to work, and the combustion adopts compression ignition to obtain higher thermal efficiency.

(5) If the judgment result in step (2) is high load condition (BMEP>1.05MPa), the electronic control unit ECU controls the intake manifold injector 3 to close, and controls the in-cylinder injector 2 to inject fuel. The fuel injected by the in-cylinder injector 2 is mixed with the air flowing into the intake manifold, and besides, the electronic control unit ECU controls the spark plug 1 to ignite the mixture.

In this step, the fuel is injected solely by the direct injection in the cylinder, and the gasoline is directly injected into the cylinder through the in-cylinder injector 2, and the evaporation of the oil droplets mainly depends on absorbing heat from the air instead of absorbing heat from the wall. The temperature and volume of the mixture is reduced, resulting in increased charging efficiency and high power output, while the tendency to knock is greatly reduced. Therefore, direct injection in the cylinder is adopted at high loads, and the latent heat of vaporization of fuel injected into the cylinder is fully utilized to achieve cooling effect, thereby improving the charging efficiency, reducing the pressure and temperature of the charge in the cylinder, and achieving the effect of controlling knocking. In addition, when the load is high, the electronic control unit ECU controls the spark plug 1 to ignite the mixture, and the combustion depends on flame propagation, so that the ignition time is controllable, thereby reducing the maximum pressure and pressure rise rate in the cylinder under heavy load, and further reducing the tendency of knocking .

Example 1

(1) In the working condition of engine cold start, the electronic control unit ECU controls the intake manifold injector 3 installed on the intake manifold to close, and controls the in-cylinder injector 2 to inject fuel, and the fuel injection timing is compression 13-17 degrees crankshaft angle before top dead center, the fuel injected by the in-cylinder injector is mixed with the air flowing into the intake manifold, and the mixture in the cylinder is ignited by the spark plug 1.

(2) The electronic control unit ECU reads the speed signal of the sensor installed on the engine crankshaft and the position signal of the sensor installed on the accelerator pedal respectively, and judges the load of the engine according to the read signals.

(3) If the judgment result in step (2) is a light load condition (the load mean effective pressure (BMEP) of the engine running = 0.4MPa), the electronic control unit ECU controls the in-cylinder injector 2 to close, and the intake manifold The fuel injector 3 injects oil during the intake stroke. In addition, the electronic control unit ECU controls the cylinder to open the intake valve 5 during the exhaust stroke, and the exhaust valve 7 opens near the bottom dead center of the exhaust, and opens near the top dead center of the exhaust. Close; at the same time, the electronic control unit ECU controls the spark plug 1 not to work.

(4) If the judgment result in step (2) is the medium load condition (BMEP=0.55MPa), the electronic control unit ECU controls the intake manifold injector 3 to inject fuel during the intake stroke, and the in-cylinder injector 2 Fuel is injected at a crank angle of 13-17 degrees before compression top dead center. The mixture in cylinder 6 is composed of two parts. The amount of fuel injected by intake manifold injector 3 in the intake stroke accounts for 75% of the total fuel injection mass. -85%, part of the cylinder is the homogeneous mixture formed by the pre-mixing of the fuel injected by the intake manifold injector 3, and the other part is the fuel injected by the in-cylinder injector 2. In addition, the electronic control unit ECU controls Spark plug 1 is not working.

(5) If the judgment result in step (2) is high load condition (BMEP=1.1MPa), the electronic control unit ECU controls the intake manifold injector 3 to close, and controls the in-cylinder injector 2 to inject fuel. The oil timing is 13-17 degrees crankshaft angle before the compression top dead center, the fuel injected by the in-cylinder injector 2 is mixed with the air flowing into the intake manifold, and the electronic control unit ECU controls the spark plug 1 to ignite the mixture.

This method maximizes the respective advantages of in-cylinder direct injection and intake port injection.

Claims (1)

1. a kind of control method of partial pre-mix compression ignition combustion electromotor, it is characterised in that comprise the following steps：

(1) under the operating mode of engine cold starting, inlet manifold oil spout of the electronic control unit control in inlet manifold Device cuts out, and controls in-cylinder injector oil spout, and the fuel oil of in-cylinder injector injection is mixed with inlet manifold leaked-in air and by fire Hua Sai lights gaseous mixture in cylinder；

(2) electronic control unit read on engine crankshaft the tach signal of sensor respectively, installed in gas pedal The position signalling of upper sensor simultaneously judges the load that electromotor runs according to the signal for being read；

(3) if the judged result in step (2) is small load condition, electronic control unit control in-cylinder injector is closed, and is entered Gas manifold injector oil spout, additionally, inlet valve is opened in electronic control unit control in cylinder exhaust stroke, exhaust valve is in aerofluxuss Lower is opened, and is closed near exhaust top dead center；The spark plug of electronic control unit control simultaneously does not work；

(4) if the judged result in step (2) be moderate duty operating mode, electronic control unit control inlet manifold fuel injector and In-cylinder injector all oil spouts, the gaseous mixture in cylinder are made up of two parts, and a part is the combustion sprayed into by intake manifold injectors The homogeneous charge that oily premixing is formed, another part are the fuel oil that in-cylinder injector is sprayed into, when the load of electromotor is increased, The ratio of the homogeneous charge in gaseous mixture in control cylinder reduces, additionally, electronic control unit control spark plug does not work；

(5) if the judged result in step (2) is high load capacity operating mode, electronic control unit control inlet manifold fuel injector is closed Close, control in-cylinder injector oil spout, the fuel oil sprayed by in-cylinder injector is mixed with inlet manifold leaked-in air, additionally, electric Sub-control unit controls spark ignitor gaseous mixture.