【摘要】 在一个单缸排量为1.14 L、压缩比为17∶1的自然吸气发动机上,使用乙醇燃料采用进气道低压喷射,进行了HCC I燃烧区域的实验研究.结果表明,在进气温度为150℃时,乙醇燃料可以在较宽的范围内(a=1~9)实现HCC I燃烧,并且以过量空气系数为标志存在着明显的边界.当过量空气系数a>9时,燃烧不完全、甚至熄火,a=9为该实验条件下的稀燃界限.当过量空气系数a<3时,不加EGR则产生爆震燃烧;加入EGR则爆震现象消失,可以实现HCC I燃烧,a=3为该实验条件下的爆震限.当过量空气系数a<1时,加入较多的EGR可以实现HCC I燃烧,但由于燃烧不完全,CO排放大幅度增加,指示效率下降,a=1为该实验条件下的浓燃界限.更多还原

【Abstract】 HCCI(homogeneous charge compression ignition) combustion boundaries of ethanol as the fuel of a naturally aspirated engine with 1.14 L displacement per cylinder and compression ratio of 17∶1 was studied experimentally, which was injected under low pressure into the inlet manifold. The experimental results show that the excess air ratio _a can be regarded as a criterion to distingwish HCCI combustion boundiaries and HCCI combustion occurs in a wide range of _a=1~9 when the intake charge is preheated to 150 ℃. When _a is larger than 9,the mixture is too lean, which is characterized by the incomplete combustion and even misfire. So _a=9 is the lean limit for the tested conditions.When _a is less than 3 and without EGR, knock combustion occurs and NO_x increases remakably. When EGR is introduced sufficiently, knock combustion disappears and HCCI combustion is achieved. So _a=3 is the knock combustion limit for the tested conditions. When _a is less than 1,although HCCI combustion occurs with a large rate of EGR, CO emission increases rapidly and the indicated efficiency decreases because of incomplete combustion. So _a=1 is the rich limit for the tested conditions.更多还原