Abstract: 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 mani-fold 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.

Key words: Intake interference, Intake process, Natural gas engine, Numerical simulation