EFI Engine Cylinder Combustion Process Numerical Simulation

As the competition, the energy and emission targets in auto industry market becoming strictly, the engine's modifications and optimization design has been put on agenda by enterprises. Experimental method and simulation analysis are the mainly methods for the engine's research. The simulation analysis is gradually replacing the traditional expensive experimental method because of the rapid development of computer and calculation models. Besides, the simulation can get some special data and avoid affected by the environment.The intake and combustion process can affect the engine's performance. So the accurate simulation on the intake and combustion process can provide basis for engine's optimization. The author first do the steady state simulation use the software of AVL FIRE, and evaluate the intake port's performance through the parameters of flow coefficient and tumble ratio. The tolerance between simulation results and experimental results is within 5%.Using the function of FEP build the moving meshes and does the transient simulation on the intake and combustion process. According to the experiment data, the turbulence models, combustion model and ignition model is to be calibrated. And the character of the velocity field, pressure field and turbulence intensity is been analyzed. The influence of the ignition angle to the combustion process is been researched as well. The flow in the cylinder is mainly swirl and tumble. The turbulent kinetic energy mainly comes from the accumulation of intake energy. With the piston moves, the initial double vortexes gradually become many small vortexes. The large eddies gradually dissipative into small vortexes. The turbulent kinetic energy decrease and finally tends to isotropic. On combustion temperature field analysis found that due to spark plug bias, the flame propagation distance is too large so that some mixture gas cannot combustion in time, and leads to the efficiency decline.Then, some parameters are changed to do some contrast analysis. The flow and burning situation at different rotating speed, double spark plugs and the influence of various ignition pattern and angles on engine performance are researched. The results show that the backflow becomes much serious at low speed which will make the engine's performance decline. Along with the increase of the ignition angle, there is more mixture gas burning near the top dead center (TDC), and the rate of heat release is much higher. The combustion efficiency will be increased. But excessive increasing the angle easy to cause the compression negative power and mechanical load increase. Finally, through the double spark plugs study found that the double spark plug can shorten the flame propagation distance, reduce deflagration tendency and can improve the burn rate effectively. So we can increase the compression ratio to improve the combustion efficiency.