【摘要】 利用数值模拟方法分析了可变涡流GDI发动机在2 000r/min、5 500r/min全负荷工况下,涡流调节阀开启和关闭不同状态的进气-喷雾-油气混合及燃烧整个过程,评价了缸内滚流对进气流动、混合气浓度分布及燃烧特性的影响。研究结果表明:在低转速时,滚流阀关闭使缸内滚流强度明显提高,是相同气门升程涡流调节阀开启时的4~6倍,较大的滚流强度加快了缸内燃油雾化速度,有助于在点火时刻缸内形成浓度均匀一致的混合气,同时增加了点火时刻的湍动能,配合较晚的点火时刻可以形成稳定而快速的燃烧;在高转速时,通过关闭滚流阀来提高缸内滚流比的水平有限,同时进气道流通能力受到抑制,缸内进气质量仅为滚流阀开启时的2/3,较大的滚流比使点火时刻缸内湍动能过大,不利于稳定快速的火焰传播。更多还原

【Abstract】 By numerical simulation method,the whole process of intake,spray,mixture formation and combustion in a DI gasoline engine with Tumble Control Valve(TCV)was calculated.In TCV opening and closing conditions,the effect of in-cylinder tumble on fuel-air mixing and combustion characteristics was examined in 2 000r/min and 5 500r/min,full load conditions.The results show that at low speed,the TCV closed enhances greatly in-cylinder tumble intensity,reaching 4~6times as the TCV open,promoting fuel droplet evaporation and generation of homogeneous charge mixture with high turbulent kinetic energy(TKE) at ignition moment,the tumble flow matched with late ignition timing can achieve a stable and faster combustion characteristics;and at high speed,the closed TCV cannot increase obviously in-cylinder tumble, and restrained by the intake port flow capacity,in-cylinder charge mass lowers to 2/3 as the TCV open,high tumble intensity provides too much TKE at ignition moment,unfavorable to the flame stable and faster propagation.更多还原