4G15D缸内直喷发动机油气分离模拟分析及试验验证

某4G15D缸内直喷发动机由于在缸盖罩位置布置高压油泵,导致气缸盖罩油气分离部分空间被占用,需要重新设计该款缸内直喷发动机油气分离结构型式。使用CFD仿真分析软件对发动机油气分离器内气液两相流场进行了数值模拟,分析了3种不同结构(改进前后)迷宫式油气分离器的流动分布、压力损失,采用离散模型模拟油滴粒子喷射,假定油滴粒子与壁面碰撞后即被捕捉,进而得出不同直径油滴的油气分离效率,根据仿真分析结果选择最优化设计方案;设计了一种简单而有效的试验方法对油气分离器分离效率间接进行验证。结果表明,采用CFD软件模拟计算方法能够计算出油气分离器油气分离效率,获得的结果反映了流动本质。在模拟分析过程中,油滴直径设定在1～15μm范围内时,根据所需要的油气分离效率优化设计油气分离结构,满足了最终产品要求。同时,在计算分析准确的前提下,提出了相应试验验证方法。

Simulation Analysis and Experiment Verification of Oil-gas Separation Based on 4G15DIn-cylinder DI Engine

The oil-gas separation mode needed to be redesigned due to the high pressure fuel pump layout in the cylinder head cover of 4G15D in-cylinder DI engine leaving little space for the oil-gas separator.By using the CFD software,the gas-liquid two-phase flow field in the oil-gas separator was simulated and the flow distribution and pressure loss of three different labyrinth oil-gas separators were analyzed.During the simulation,the discrete model was used to simulate the droplet injection.Assuming that the droplets were captured after they impinged on the wall,the separation efficiency of different diameter droplets could be acquired.According to the simulation results,the optimum design scheme was chosen.With a simple and effective test method,the separation efficiency of oil-gas separator was verified.The result shows that the simulation and calculation method of CFD software can calculate the separation efficiency of oil-gas separator.The simulated result reflects the nature of flow.During the process of simulation and analysis,the configured oil droplet diameter is 1-15 μm,and the oil-gas separation structure is optimized and designed according to the required separation efficiency,which satisfies the final product requirement.Moreover,the corresponding verification method is put forward based on the accurate calculation and analysis.