Improving the theoretical cycles of four-stroke internal combustion engines and their simulation calculations

This paper is based on conventional theoretical cycles of reciprocating four-stroke spark ignition (SI) internal combustion engines (ICEs). The authors have analysed the theoretical thermodynamic cyclical processes of modern gasoline direct injection (GDI) engines and then put forward the theory and the method for improving theoretical cycles of ICEs that are different from traditional theoretical cycles. Moreover, theoretical analyses and engine bench tests showed that the theory and the method could be applied not only to improve the cyclical thermal efficiency, power performance, and economic performance of ICEs but also to improve the engine emission characteristics, reduce rough operation, and reduce maximum heat loads, which lowered the maximum working pressure and the maximum working temperature and improved the mean heating temperature. Thus, the working reliability of the engine was improved. The improvement in theoretical cycles is one of the advantages of GDI engines. As is the trend with ICEs, energy conservation, purification, and environmental protection are among the main aspects of GDI engine development.