复合HCCI与进气道喷射HCCI燃烧特性及运行范围对比

【目的】为了进一步改善HCCI的燃烧状况,并拓展其运行范围.【方法】对缸内直喷与进气道喷射结合下的复合HCCI和仅进气道喷射模式下的HCCI发动机的燃烧特性及运行范围进行了对比.【结果】复合HCCI的峰值缸内压力、峰值缸内温度和峰值瞬时放热率均有所升高,且对应的曲轴转角有所提前,表明燃烧时刻有所提前.其中,峰值缸内压力较单纯进气道喷射时升高了0.6 MPa,峰值压力对应的曲轴转角平均值提前了1.2°CA,燃烧持续期也缩短至10°CA左右.【结论】缸内直喷正庚烷可明显改善正丁醇HCCI的燃烧状况,降低HCCI的循环变动,在一定程度上控制正丁醇HCCI的燃烧相位,使得平均指示压力和指示热效率有所提高,并且使得HCCI发动机的运行范围得到拓展.

Comparison of combustion characteristics and operation range between compound HCCI mode and intake pipe inj ection HCCI mode

[Obj ective]The aim of this research was to improve homogeneous charge compression igni-tion (HCCI)combustion and extend the operation range.[Method]The combustion and operation range were compared between compound HCCI (direct inj ection and pipe inj ection combined)and only pipe inj ec-tion HCCI mode.[Result]The result showed that the peak of in-cylinder pressure,in-cylinder temperature and instantaneous heat release rate all increased and crank angle also occurred in advance which showed the start timing of combustion was advanced compared to only pipe inj ection HCCI mode,the peak in-cylinder pressure increased by 0.6 MPa,the crank angle corresponding to the peak pressure was advanced nearly 1.2°CA and the combustion duration reduced about 10°CA.[Conclusion]It was found that HCCI combus-tion fuelled with n-butanol was significantly improved by using n-heptane direct inj ection and cyclic varia-tion was reduced.To some extent,the combustion phase could be controlled,both indicated mean effective pressure(IMEP)and indicated thermal efficiency were improved,so the operation range of compound HCCI was extended.