Micro-control of automobile emission-internal purification technology of gasoline engine

Since the national compulsory implementation of the National Sixth OBD remote emission management terminal, Deep Speed Reid has conducted some research on the internal purification of gasoline engines based on the micro-control technology of motor vehicle emissions with traffic characteristics, and customized the National Sixth OBD remote emission management terminal according to its characteristics. Among the emission control technologies of motor vehicles, the main internal purification technologies of gasoline vehicles mainly include electronically controlled fuel injection system, delayed ignition advance angle, exhaust gas recirculation, optimized design of combustion system, variable intake system, stratified intake engine and direct injection technology of gasoline engine.

First, the electronic fuel injection system

The electronic controller has an injection system (electronic? Fuel? Injection? System) followed by EFI, the name is too long. It can use various sensors to detect various states of the engine, and through the judgment and calculation of the microcomputer, the engine can obtain the mixture with appropriate air-fuel ratio under different working conditions. The air-fuel ratio of gasoline vehicles is generally 14.7: 1, which will be automatically adjusted according to different working conditions. The EFI system is developed on the basis of modern computer technology and testing technology, which can be regarded as a significant progress in the field of emission technology and can effectively reduce the emission of motor vehicles. Therefore, we always say that air-fuel ratio refers to the electronically controlled fuel injection system designed by multi-point injection gasoline vehicles to ensure emissions. However, it is very common. When we use OBD to read data, it can generally be displayed around 14.7: 1. At high speed, it will be adjusted to about 12: 1 to output higher power.

The invention has the advantages of uniform distribution of mixed gas in the cylinder, high inflation efficiency, good instantaneous response characteristics and good gasoline atomization quality. There are two ways: open-loop control and closed-loop control.

1, open-loop control? Open-loop control is to store the optimal fuel supply parameters of the engine in various working conditions determined by experiments into the computer. When the engine is running, the computer judges the working condition of the engine according to the input signals of various sensors in the system, so as to calculate the optimal fuel supply, and controls the injection time of the electromagnetic injector through the power amplifier, so as to accurately control the air-fuel ratio of the mixture.

2. Closed loop control? Closed-loop control means adding an oxygen sensor in the exhaust pipe, measuring the air-fuel ratio of the combustible mixture entering the cylinder according to the change of oxygen content in the exhaust pipe, and constantly comparing it with the set value, and correcting the fuel injection amount according to the comparison result, so as to finally keep the air-fuel ratio near the set value. The advantage of closed-loop control lies in the cooperation with three-way catalytic converter, and the air-fuel ratio is controlled at around 14.7: 1, so as to achieve the most effective purpose of reducing pollution emissions.

Open-loop control is still needed for transient conditions such as starting, warming-up and acceleration to ensure the stability of engine operation. We often encounter vehicle emission failures. The lights are on because the emissions are not up to standard. More than 80% of the cases are related to the voltage of the oxygen sensor and the temperature of the three-way catalyst. Therefore, this data is necessary for OBD remote emission management in countries IV, V and VI.

Second, delay the ignition advance angle.

Ignition advance angle has an important influence on engine power, economy, emission characteristics and noise, but delaying ignition advance angle has always been the simplest and most commonly used emission control technology.

With the decrease of ignition advance angle and ignition delay, the emissions of HC compounds and nitrogen oxides are obviously reduced. The decrease of HC is due to the increase of exhaust temperature, which promotes the oxidation of HC in cylinder and exhaust pipe during exhaust. The reason for the decrease of nitrogen oxides is that the maximum combustion temperature decreases linearly with the delay of ignition advance angle. However, with the delay of ignition advance angle, the combustion pressure will decrease and the average effective pressure will increase. Therefore, it is limited to reduce emissions by delaying the ignition advance angle. Under the condition of no obvious deterioration of power performance and fuel consumption, nitrogen oxides can only decrease by 65,438+00-30%. During calibration, emission characteristics, power and economy will be considered comprehensively to determine the best ignition advance angle.

Third, exhaust gas recirculation.

Exhaust gas recirculation (exhaust gas? Gas? Recirculation (EGR) is the main measure to control the emission of nitrogen oxides, which is widely used and only effective for nitrogen oxides. Because the oxygen content in the exhaust gas is very low, it is mainly connected by inert gas nitrogen and carbon dioxide, and part of the exhaust gas flows back to the intake system through EGR valve. After mixing with fresh air mixture, the oxygen concentration in fresh air mixture is diluted, which leads to the decrease of combustion efficiency and the increase of specific heat capacity of fresh air mixture.

If EGR is increased too much, the combustion speed will be too slow, the combustion will become unstable and easy to stall, and HC compounds will also increase. If the EGR is too small, the emission of nitrogen oxides will not meet the regulatory requirements, which will easily lead to overheating of the engine. When we formulate vehicle control strategy, EGR control strategy mainly includes the following aspects:

1. When the EGR rate is less than 10%, the fuel consumption basically does not increase. When the EGR rate is greater than 20%, the engine combustion is unstable and HC compounds increase 10%. If the EGR rate is controlled in the range of 10%-20%, the allowable value of ER rate will also increase with the increase of load.

2. At low speed and idle speed, the emission concentration of nitrogen oxides is low. In order to ensure stable combustion, EGR was not carried out. Therefore, the core reason is that the internal combustion engine cannot emit zero emissions.

3. When the engine is a hot engine, EGR is performed. When the cooler temperature is low, the emission concentration of nitrogen oxides is also low, and the gas supply of mixed gas is uneven. At this time, the idle speed and air intake will be too large to ensure the normal combustion of the engine, and EGR will not be carried out when the engine is cold.

4. At high load and high speed, in order to ensure the power of the engine, the air mixture is thick at this time, and you see that the air intake system of the sports car is somewhat exaggerated. At this time, nitrogen oxides emit relatively few products, so EGR is not carried out or the EGR rate is reduced.

5. The influence of exhaust gas recirculation on NOx emission and fuel consumption is also affected by air-fuel ratio, ignition advance angle and other factors. Therefore, better engine performance can be obtained when EGR is controlled and ignition is controlled comprehensively, so there is a close correlation between them.

Fourth, the optimization design of combustion system

1, compact combustion chamber shape? At present, the engine is getting smaller and smaller, and the power is getting more and more sufficient. However, different combustion chamber shapes may cause great differences in power performance, which is why so many engine factories have painstakingly studied how to make it smaller, use the original cylinder block, improve power, and even have a set of mature technologies. In addition, under the protection of the high pressure bag, the position of the spark plug is set in the center of the combustion chamber, which shortens the flame propagation distance. The purpose of the diagram is to shorten the combustion time, improve the equal capacity of the thermal cycle, improve the thermal efficiency and reduce the emissions of hydrocarbons and carbon monoxide.

2. Improving the airflow movement in the cylinder and increasing the degree of vortex and turbulence of the mixture in the cylinder will help to strengthen the oil-gas mixing and ensure the rapid and complete combustion.

3. Reasonably improve the compression ratio. Because the thermal efficiency of gasoline engine is lower than that of diesel engine, the compression ratio is not enough. Increasing compression ratio is the improvement direction of gasoline engine for many years.

4. Increasing the intake air, changing the traditional two-valve arrangement per cylinder into three-valve, four-valve or five-valve arrangement, or adopting turbocharging, can obviously improve the intake air charge and reduce the pumping loss, which not only reduces the fuel efficiency consumption of gasoline engines, but also reduces the emission of pollutants. This is why adding a car with a turbine is more expensive than adding a car without a turbine. This device is not only for improving engine power.

5. Reduce the gap volume that does not participate in combustion? The compact combustion chamber and piston ring design have reduced a lot of hydrocarbons.

Verb (abbreviation of verb) variable intake system and stratified intake engine

In order to improve the inflation coefficient, in addition to using multi-valves, high-end cars also introduce various variable parameter intake systems. The exhaust process of the engine is a periodic pulsating process, and there is strong pressure fluctuation in the intake and exhaust system. Using pressure wave to increase the intake pressure before the intake valve closes can increase the intake charge, which is the so-called dynamic effect, also known as inertial supercharging. Variable-length intake pipe has been used in many modification fields, which can increase the torque at various speeds by 8% on average, with the maximum increase of 12- 14%, thus greatly improving the power, economy and emission characteristics of the engine. Changing intake valve timing has more obvious influence on engine performance than changing exhaust valve customization, but changing exhaust valve is easier to operate and realize. In fact, the modified car that bombed the street is worth recommending modification, if it is not noisy. Whether it is a wave or not depends entirely on the scene.

In order to ensure ignition, a rich mixture is formed near the spark plug and a lean mixture is provided in other areas. The engine designed according to this requirement is called stratified charge engine. To meet this requirement, the combustion chamber is generally divided like a diesel engine, and the auxiliary combustion chamber is equipped with a spark plug, which is equivalent to the role of the combustion chamber and provides rich mixture for the auxiliary combustion chamber.

Six, gasoline vehicle direct injection technology

This is familiar to everyone. Direct injection engine is a widely used internal combustion engine technology in contemporary automobile technology. It directly injects gasoline into the combustion chamber to mix with air for combustion. At the same time, it has the advantages of gasoline engine and diesel engine, which makes uniform combustion and stratified combustion become a reality, greatly improves the mixing degree of mixed gas, and controls the air-fuel ratio in the combustion process more accurately, thus realizing complete combustion and reducing the emission of unburned hydrocarbons.

The direct injection technology of gasoline engine can improve the compression ratio of the engine, improve the thermal efficiency of the engine and save energy by more than 30%.

For the online OBD remote emission monitoring platform implemented in China, it is necessary to update the in-use vehicles whose indicators can still meet the requirements of national emission standards, or urge non-standard vehicles and engine vehicles to move out of key cities through tax adjustment mechanism.

Nowadays, the development of automobile technology is getting faster and faster, which also reflects the future, and the future is now. Faced with such harsh environmental problems, the automobile group always takes sustainable development as its responsibility, actively responds to the national environmental protection requirements, adheres to green development as the core, and takes technology research and development as the leading factor to produce more environmental protection products.

In the future, the automobile group will give full play to its own technological advantages in a more macro pattern, so that the automobile can live in harmony with nature.

This article comes from car home, the author of the car manufacturer, and does not represent car home's position.