多点电喷天然气汽车发动机进气干涉现象的数值解析

首先采用多维数值模拟的方法解析了从天然气喷射阀喷出的突发天然气喷流的发展过程,并由纹影试验验证了这个数值解析方法的可行性。在此基础上,解析了单进气阀和双进气阀发动机进气歧管内天然气的喷射和反射过程。结果表明,大量天然气与进气阀冲突后向进气歧管入口方向反射并造成进气阀附近气体压力升高;若进气歧管较短时,天然气-空气混合气反射到歧管入口并造成各缸混合气分配不均匀是完全可能的;即使较长的进气歧管时,由于发火顺序不同,各缸间的进气干涉程度也不一样,这将引起各缸实际的进气充量发生变化。

NUMERICAL ANALYSIS OF INTAKE INTERFERENCE FOR NATURAL GAS VEHICLE ENGINE WITH MPI SYSTEM

The development process of gas jet injected from a natural gas injector is firstly analyzed using multi-dimensional numerical simulation method, which is proved feasible by the schlieren experimental results. Then based on the research above, the injection and reflection process of natural gas in intake manifold is calculated for single-valve engine and double-valve engine, respectively. According to the results predicted by numerical simulation conclusions are drawn as below, the injected natural gas is reflected back to the inlet of intake manifold after it conflicts with the intake valve, which at the same time leads to the increase of pressure near the intake valve, for engines with short intake manifold, mixture of reflected natural gas and air might reaches the inlet of intake manifold and then causes no-uniform mixture distributions between cylinders, and even for engines with longer intake manifold, different ignition timing of each cylinder will result in the different degrees of intake interference between cylinders, which further leads to the unequal of actual cylinder intake charges.