喷雾引导分层燃烧部分负荷喷油点火策略研究

Study on Injection and Ignition Strategy of Spray-Guided Stratified Combustion at Part Load

在一台中置多孔喷油器的直喷汽油机上进行试验,研究了喷雾引导分层燃烧技术在部分负荷(n=2 000r/min、BMEP=0.2MPa)下,喷油点火策略对发动机油耗和排放的影响。研究结果表明:点火(IGN)时刻处于喷油结束(EOI)时刻附近时,可以实现稳定的分层稀薄燃烧。在IGN时刻与EOI时刻等高线图中,THC排放与NOx排放呈现矛盾折中关系,CO排放随EOI时刻的推迟而逐渐降低。有效燃油消耗率受到燃烧效率和燃烧相位两个矛盾因素的共同影响,在EOI为上止点前34°的曲轴转角而IGN为上止点前35°的曲轴转角时获得最低值(329g/(kW·h))。采用两次喷射策略时,小的喷射间隔下,喷射比例对分层燃烧的燃烧稳定性和排放影响较小。

The influence of injection and ignition strategy of spray-guided stratified combustion on fuel economy and emissions at part load was experimentally studied on a direct injection gasoline engine with center-mounted injector. The results show that a stable-stratified lean combustion is achieved when ignition （IGN） timing is near the end of injection （EOI）. On the contour of EOI timing and IGN timing, THC and NO~ emissions present trade-off relation and CO emission reduces as EOI timing is delayed. Brake specific fuel consumption （BSFC） is influenced by combustion efficiency and combustion phase, and the lowest BSFC is 329 g/（kW · h） when EOI timing is 34° BTDC and IGN timing 35° BTDC. The combustion stability and emissions are not sensitive to the injection ratio with a small interval when a two-stage fuel injection strategy is used.