The Numerical Simulation For Mixture Formation Process Of GDI Engine With Ignition Chamber

Compared with conventional gasoline, GDI engine has its own advantages of higher fuel economy, more rapid response and lower HC in cold start condition. With the increasing consumption of petroleum and the strict emission control regulations, GDI engine is exploited by most of automobile corporations.Mixture formation process, which connects spray process with ignition and combustion processes, is the key to control and determine combustion process. In order to increase Air-Fuel ratio and compression ratio, improve fuel economy, as well as to ensure the reliability of the ignition and combustion stability, formatting appropriate mixture is extremely important. Therefore, it is significant to investigate the mixture formation process.This paper is the first phase of research production of GDI Engine with ignition chamber. The following research work has been conducted. 1) The ignition-chamber GDI engine and its fuel injection strategy were presented; 2) The in-cylinder turbulence flow, spray process with two injection pulses, and stratified mixture formation process are simulated by multi-dimensional fluid dynamic (CFD) code -AVL FIRE 8.6. Effects of mixture formation, especially mixture in ignition chamber with the diverse injection timing and different shapes of ignition chamber on in-cylinder are analyzed. Meanwhile, influence of mixture formation during main injection process and ignition chamber concentration control volume spray process with different speed are also studied. The fuel injection strategy is proved feasible in large region wok condition.The results show that: 1) the ignition-chamber GDI engine has a good ignition reliability and combustion stability, which also has the potential of decreasing emissions and enhancing the combustion speed and stability; 2) After comparison of different shapes of ignition-chamber and injection timing, the mixture distribution in ignition chamber is optimized; 3) The fuel injection strategy presented is feasible. Furthermore, it can be ensured that there is flammable mixture with appropriate concentration distribution near the spark plug to enhance the ignition reliability and make it possible to enlarge ignition timing window.