3-Dimensional Simulation Research On Combustion Organization Optimum For Gasoline Directly Injection Engine

With the emergency to solve the energy and environment problem, no choice is left but promoting edge cutting high efficiency and low emission combustion mode for internal combustion engine to face up to the severe emission regulation and the cost control. Up to now, massive study on compression ignition engine has shown its flexibility on varies fuel with the help of specific control of inlet charge, fuel injection, EGR and other engine Parameters. Among which gasoline compression ignition stands out as a potential commercial combustion mode for the easy access to the fuel, high efficiency and ultra-low PM emission. Fuel that has long ignition delay can be supplied to partially premixed charge compression ignition. With injection strategy, fuel injection and the combustion are separated, allowing the fuel and fresh charge to have more time to mix. Unlike homogeneous charge compression ignition, the ignition of PPCI depends on the distribution of the stratified mixture. Hence the ignition can be controlled by the fuel injection strategy.In this Paper, a 3-Dimensional engine model based on a ZH1130 diesel engine is established by AVL FRIE, and modified with experiment data. Numerical calculations are conducted to study the effect of different Parameters on this combustion mode. The result shows that:Flow characteristics of the intake charge: compare with the open combustion chamber,the “?” shaped chamber can generate Stronger air flow which can do benefit to the ignition process. When the initial swirl number varies from 1 to 2, it makes little difference to the combustion. Continue increase the SN can lead to a delayed combustion phase with a fierce heat release. The position of the nozzle: the vertical position of the nozzle and the angle between the spray axis have similar effect on the combustion, they both can adjust the position of the spray, thus make change on the turbulent kinetic energy where and when ignition process takes place. Take all Parameters above as a whole into consideration, and the result of the calculations show that low NOx emission and high efficiency cannot be achieved without EGR. Intake charge composition with adjusted injection timing: with optimized fuel injection timing and EGR, ultra-low NOx emission can be realized with high efficiency. Also in this research, inlet air throttle valve is simulated to figure out the combustion feature under the situation of equivalent ratio=1, and the results demonstrate that it is a feasible way to reduce the NOx emission. Multiple injection strategy simulation research shows no obvious benefit to change the “trade off” relationship between NOx emission and the fuel economy, but can improve the ignition process as it can provide stratified mixture. Certain method like EGR or inlet throttle valve has to be taken to avoid the NOx zone on the equivalent-temperature table.This research proves that under the gasoline direct injection compression ignition situation, both low NOx emission and high efficiency can be realized with the help of optimized injection timing and EGR or throttle valve. The result of this Paper can provide guidance for further experiment research on gasoline or gasoline-like fuels on the compression ignition engine.