变配气正时对HCCI燃烧的影响研究

试验研究了变进排气正时对缸内早喷柴油均质充量压燃燃烧(HCCI)的影响。柴油在排气上止点附近喷入缸内,研究改变进排气门负重叠期对HCCI燃烧放热率、排放及综合性能的影响。试验研究结果表明,增大气门负重叠期,有利于早喷燃油的快速蒸发和均质混合气的形成,有利于减少柴油湿壁,但是容易使燃烧相位提前,易于产生爆振。增加气门负重叠期,HCCI燃烧的运行范围向低工况扩展,但是中高负荷受到限制。在HCCI燃烧可运行范围内,有害排放产物和指示油耗均下降。

Effects of Variable Valve Timing on Diesel Fuel HCCI Combustion

The effects of variable valve timing on diesel fuel HCCI combustion with direct in-cylinder early injection were investigated. Diesel fuel was injected into cylinder with mechanical fuel pump near TDC of exhaust stoke, and the valve negative overlap duration was changed to study its effects on HCCI heat release rates, emissions and general performances. The experiment result showed that it was advantageous to increase negative valve overlap duration for early injected fuel evaporating fast, formation of homogenous charge and reduction of wall wetting. Meanwhile, increasing negative valve overlap duration was prone to cause excessively early start of combustion and cylinder knock. The operating range of HCCI combustion would extend to lower load but more limit at medium and high load when increasing negative valve overlap duration. In the operating range of HCCI combustion,exhaust emissions and indicated fuel consumption would decrease with negative valve overlap duration increasing.