乙醇燃料均质压燃(HCCI)燃烧边界

HCCI Combustion Boundiaries of Ethanol as Engine Fuel

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HCCI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(φa=1～9)实现HCCI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φa＞9时,燃烧不完全、甚至熄火, φa=9为该实验条件下的稀燃界限.当过量空气系数φa＜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HCCI燃烧, φa=3为该实验条件下的爆震限.当过量空气系数φa＜1时,加入较多的EGR可以实现HCCI燃烧,但由于燃烧不完全,CO排放大幅度增加,指示效率下降, φa=1为该实验条件下的浓燃界限.

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 φa can be regarded as a criterion to distingwish HCCI combustion boundiaries and HCCI combustion occurs in a wide range of φa = 1 - 9 when the intake charge is preheated to 150 ℃. When φa is larger than 9,the mixture is too lean, which is characterized by the incomplete combustion and even misfire. So φa =9 is the lean limit for the tested conditions. When φa is less than 3 and without EGR, knock combustion occurs and NOx increases remakably. When EGR is introduced sufficiently, knock combustion disappears and HCCI combustion is achieved. So φa = 3 is the knock combustion limit for the tested conditions. When φa is less than 1 ,although HCCI combustion occurs with a large rate of EGR, CO emission increases rapidly and the indicated effciency decreases because of incomplete combustion. So φa = 1 is the rich limit for the tested conditions.