The Analysis On General Trends Of Gas Exchange Process’ Performance Of Gasoline Engines

Gas exchange process is the assurance of the working of engines, which will make an effect on engine power performance, fuel economy and emission performance. In China, there’re few papers which analyze the general trends of gas exchange process. This paper make an analysis on general trends of Gas exchange process of gasoline engines which is based on experimental data and theory. It focuses on the gas exchange parameter and its effects on engine performance. The analysis is very important to the improvement of gas exchange process and the paper provides a certain guidance for the concept design, optimization of mathematical model and bench calibration of the same type engine.At first this paper introduces the information of prototype engines, test and some simulation made by GT-Power. It shows the general trends and reasons of pumping loss, in-cylinder RGF and filling coefficient along with the change of engine speed and load.Then, this paper analyzes the influence that gas exchange parameters make on the engine performance. The results show that the most important parameter is the inlet density, and then is the filling coefficient. Through the engine fuel consumption formula, we find that the thermal efficiency will be increased and fuel economy of the engine will be improved by optimizing pumping loss and reducing its ratio in average indicated pressure of cylinder high pressure cycle. At the same time, according to data analysis, we find that an appropriate increasing in in-cylinder RGF can improve fuel economy and emissions of nitrogen oxides in partial load, but excessive in-cylinder RGF will lead to combustion deterioration and sharply rising of carbon monoxide and hydrocarbon emissions.After that, this paper analyzes the factors which have an influence on gas exchange parameters. It shows that intake and exhaust system’s pressure fluctuation have an influence on the filling coefficient. And also, this paper decomposes the influence factors of pumping loss into three parts, and analyzes the changes after synthesizes the factors. We find that the changes of synthetic value and pumping loss are very similar. It reveals the changes of the internal causes of pumping loss along with engine speed and load. And this paper applies a simple and cost-saving measurement methods of pumping loss on research of gas exchange process. When engine is at low speed, pumping loss is equal to intake and exhaust pressure differential; when engine is at high speed, pumping loss is equal to the sum of intake and exhaust pressure differential and inlet-exhaust valve pressure drawdown. And we find that the most important factors is intake pressure.At last, a software of engine transient performance analysis and control is written. It is used to analysis and display the changes of operating parameters.