火花塞对汽油机缸内湍流的影响

针对4种不同火花塞,利用三维模拟软件建立了缸内直喷汽油机的仿真计算模型,在2 000r/min冷态情况下,对缸内湍流进行了计算,得到发动机在进气冲程、压缩冲程、点火时刻气缸内及火花塞附近的流场,评价了缸内速度场、湍动能参数。结果表明:在进气初期,火花塞对周围湍动能和缸内速度场影响最大,决定了缸内初期涡团的形成以及此后缸内湍流的发展变化;随着进气门的关闭和气缸容积的增大,火花塞对缸内湍流的影响越来越小;直至活塞靠近上止点,火花塞对局部流场的影响再一次显现。采用恰当的火花塞结构,使点火位置气流处于低速且具有足够湍流强度,对点火的稳定性和火焰的传播具有深远的影响。

Influence of Spark Plug on In-cylinder Turbulent Flow of Gasoline Engine

For four kinds of spark plugs for gasoline direct injection(GDI)engine,the simulation and computation model was established by using 3D simulation software and the in-cylinder turbulence in cold state at 2 000 r/min was calculated.Then the flow field distributions inside cylinder and near spark plug during the intake stroke,compression stroke and ignition timing were acquired and the velocity field and turbulent kinetic energy in the cylinder were evaluated.The results showed that the spark plug had a strong influence on the turbulent kinetic energy and in-cylinder velocity field at the initial stage of intake stroke,which determined the formation of initial vortex and the development of in-cylinder turbulence.With the closing of in-take valve and the increase of cylinder volume,the effect of spark plug on turbulence became weaker.Until the piston ap-proached the top dead center,the effect of spark plug on local flow field became obvious again.Accordingly,an appropriate spark plug structure could lead to a low velocity and sufficient turbulence strength at the ignition timing and hence ensure the ignition stability and flame fast propagation.