缸内直喷汽油机SI-HCCI-SI燃烧模式切换的研究

双燃烧模式是车用均质混合气压缩着火（HCCI）发动机理想的运行策略，即在中小负荷下使用HCCI燃烧模式，而在大负荷和高转速下过渡到传统的火花点火（SI）燃烧或柴油机燃烧模式运行。采用可变配气和缸内直喷技术，在一个发动机循环内改变配气策略和喷油策略，实现从SI模式所要求的常规火花点火配气相位向HCCI模式要求的负阀重叠配气相位的跳变，配合缸内直喷策略的调整，实现SI模式和HCCI模式间的切换。通过分步切换的策略，可以提高切换过程的稳定性。燃烧模式切换可在一个发动机工作循环内完成，切换过程平稳迅速可靠，无失火和爆震等异常燃烧现象的发生。

Study of SI-HCCI-SI Mode Switching in a GDI Engine

Two-mode operation engine is considered as an ideal operation strategy for HCCI engine.In low and middle load,the engine operates on HCCI mode,while in high load and high speed,the engine mode switches into the SI mode for gasoline engine and/or CI mode for diesel engine.By stepped switch,the stabilized switching process can be obtained.With two-stage cam profile,the cam shifting can be completed within one engine cycle,that is,from normal cam profile for SI mode to Negative Valve Overlap(NVO) profile for HCCI mode,or backwards.Matching with the adjustment of injection strategies,the SI/HCCI mode switching was realized.Experimental operation showed that the combustion mode switching could be completed within one cycle.Smooth,rapid and reliable switching processes were realized without abnormal combustion such as knocking and misfiring.