Summary And Quantitative Study On The General Trends Of The Gas Exchange Process Of Gasoline Engines

The challenge from the energy crisis and the electric vehicle industry has put forward higher requirements for further improving the thermal efficiency and performance of gasoline engines.The degree of the gas exchange process of gasoline engines directly influences its power,economy and emission.The same size of the cylinder volume,in the same intake state,if you can breathe in more fresh air,you can spray more fuel,produce more effort.Therefore,it is important to summarize and quantify the general trends of gas exchange process to improve the efficiency of the cylinder and improve the performance of the engine.Experimental research is carried out under multiple working conditions in the two car gasoline engines prototype,analyzing the variation of gas exchange process parameters on the test data,and derived the quantitative equation of volumetric efficiency,RGF and pumping loss,summarizes the influencing factors the gas exchange process parameters.Firstly,the change rule of gasoline engine ventilation process parameters with speed and load is analyzed.It is concluded that the intake density is the key influence parameter of gasoline engine power,the pumping gas loss ratio and RGF are the key influencing factors of gasoline engine economy.However,the pumping loss ratio is not very different between the different gasoline engines.Then,the governing equations of the volumetric efficiency,the simplified equation of RGF and the approximate equation of the pumping loss are obtained by reasonable hypothesis and theoretical deduction.The accuracy of the quantized equation is verified by comparing the measured parameters with the simulated values.Finally,the general trends of the gas exchange process of gasoline engines are summarized as follows,(1)the volumetric efficiency is mainly affected by cylinder volume when the gasoline engine intake valve closed and the RGF.(2)RGF is mainly affected by the inlet and exhaust pressure difference and the volume of the cylinder when the valve is closed.The greater the inlet air pressure difference is,the bigger the overlap angle of the valve is,the higher the RGF is.(3)the pumping loss is mainly affected by the pressure difference between inlet and outlet.The influence of overlap angle of air valve on pumping loss is only secondary.The general trends of the above gas exchange process can be used to provide the data support for the choice of modeling boundary data and the determination of key design parameters and the optimization of operating parameters.