The Detecting And Analyzing Of Operation Parameters And Performance Parameters Of Gasoline Engine Under The Automobile Transient Condition

Energy crisis and environmental issues are two challenges that the world has to face.As the fuel economy regulations and emission regulations becoming more and more stringent,various countries pay more and more attention to the energy conservation and emissions reduction of vehicle engines.Engine is the heart of the automobile.In the past,the study of the engine was often limited to steady-state performance,further,engine's transient performance was often poorly understood.However,most of the time engine work on vehicle is under transient conditions,its transient performance is closer to the actual performance.In order to improve its dynamic performance,fuel economy performance and emission performance,it is necessary to study the transient performance of engine under transient conditions.We carried out steady-state bench test,transient bench test and vehicle road test conditions test based on two sets of automotive gasoline engine.Using the method developed by our research group,the on-line continuous detection of the key parameters of the engine under transient conditions was realized.By analyzing a large number of test data,the following rules were summarized.1)50%combustion position and 10-90%combustion duration are two important combustion characteristic parameters,they have very important influence to engine performance.50%combustion position and peak cylinder pressure position have a corresponding relationship,peak cylinder pressure position often lags behind 50%combustion position.10-90%combustion duration is mainly affected by excess air ratio,load,RGF and other factors,it tends to increase with the increase of excess air ratio,and it tends to shorten with the increase of load.2)RGF which called residual gas fraction is a very important parameter that affects the combustion process of the engine,it also has very important influence to emission performance,dynamic performance and fuel economy performance of the engine,but its impact on the engine indicated thermal efficiency is less than the impact that excess air ratio on the engine indicated thermal efficiency.3)The indicated thermal efficiency is mainly affected by the factors such as RGF,ignition advance angle,load,excess air ratio,engine speed and so on.It is the combination of these factors that determine the level of indicated thermal efficiency.4)Transient condition is a special condition of steady-state condition.The difference between transient conditions and steady-state conditions performance parameters in some areas is caused by the difference of control parameters.In particular,when the car is shifting gears,rapidly decelerating and rapidly accelerating,the engine parameters tend to have a lot of fluctuations.A great difference between transient performance and steady-state performance will appear.Through this study,the change rule and internal connecting link of the operating parameters and performance parameters of the gasoline engine under transient conditions were cracked;the reason of the performance difference of the gasoline engine in transient state and steady state was analyzed.All of them provided a method and tool to improve the actual transient performance of gasoline engine.