Multi-Cycle Three Dimensional Simulation Of The Working Process In A Direct Injection 4-Valve Gasoline Engine

The numerical simulation of the working process in the internal combustion engine has become increasingly important and effective aided method during the development and the design of the internal combustion engine. By the simulation calculation and optimization design, researchers can select the best design scheme which can save lots of time, funds and material and shorten the period of research on the engine. Both the simulation and experiment promote the research and development of the internal combustion engine.In the previous study, the numerical simulation research of the different parts of engine was separated or contained only one or two parts. The working process of the internal combustion engine includes the intake, compression, expansion and exhaust strokes. Recently the study on the engines just based on the one working process cycle. As a result of the complex of the initial conditions and the boundary conditions of the numerical simulation of the process in the internal combustion engine, the conclusions of these methods can not completely reveal the actual facts and they could deviate from the true working process of engine. Therefore, it is necessary to simulate the complete working process with multi-cycle 3D numerical method in the internal combustion engine. Meanwhile, it's valuable and important for the research of the engine.This paper discussed the multi-cycle 3D numerical simulation of the GDI gasoline engine. The mathematical model of 3D flow computation of the system was built, which contained the intake port, intake valves, cylinder, exhaust valves and exhaust port, and the fuel spray mixing model and the chemical reaction mechanism were improved, after that, the multi-dimension simulation of the ignition and combustion model were completed. The convergence criteria, initial conditions, boundary conditions were proposed and their treatment method of the multi-cycle 3D numerical simulation was perfected. All of these provide an important way for the multi-cycle 3D numerical simulation on the computer.The multi-cycle 3D numerical simulation of a four-valve GDI gasoline engine was studied. Flow field, pressure field, temperature field, fuel injection, mixture combustion and turbulent kinetic energy of the working process of the engine were described in detail and contrastive analysis of the results in different cycle was made. The variations of the pressure, temperature, flow field and the turbulent kinetic energy were obtained, which varied with the growing of the times of the calculation cycles during the working process. The principle and the method of the generation of the structure grids were developed. To take example for the complex combination intake manifold with a helical port and a tangential port, the blocking technique of the generation of the grids was illustrated. The multi-block structure body-fitted grid of a four-valve GDI gasoline engine for the multi-cycle 3D numerical simulation calculation was also built, and the dynamic grids with the motion of the valve were adjusted and corrected.