变工况条件下HCCI/SI燃烧模式转换的实现

Combustion Mode Transition Between HCCI and SI in Load Transition

为了满足车用发动机的要求,在HCCI燃烧的运行范围之外,仍需要使用火花点火(SI)燃烧模式.目前HCCI/SI模式转换的方法和策略都是在相同工况下完成的,这增加了控制上的难度并会带来负荷波动.针对此问题,采用全可变气门机构结合外部废气再循环的方法,在变工况条件下,完成HCCI和SI燃烧模式的转化.并将HCCI燃烧模式中废气率调整负荷的方法延伸进SI燃烧控制中.由于在控制策略层面,采用模式过渡的方法,消除了HCCI/SI模式转换的概念,因而简化了控制策略.

In order to satisfy the request of vehicle engine,SI combustion still needs to be used beyond HCCI operat-ing range.At present,all the methods of HCCI/SI combustion mode transition are realized at the same load,which increases controlling difficulties and brings load fluctuation.To solve the problem of mode transition,a gradual tran-sition from HCCI to SI combustion in load transition was performed by using the variable valve actuation system and external exhaust gas recirculation,and the strategy that the load of engine is controlled by exhaust gas fraction in HCCI combustion was introduced into the SI combustion.The control strategy for all-load is simplified,due to the fact that the complicated control of mode switching has been eliminated.