均质压燃的燃烧循环变动试验

为研究均质压燃的燃烧循环变动规律，在单缸发动机上进行了不同辛烷值燃料的均质压燃试验．结果表明，在恒定的平均指示压力下循环变动随辛烷值的增大而增大，在恒定的辛烷值下循环变动随平均指示压力的增大而减小；对于高辛烷值燃料，转速对循环变动的影响非常明显，尤其在较高转速时，循环变动随转速的升高急剧增大；在不发生爆震的情况下，燃烧效率、指示热效率以及HC和CO排放随循环变动的减小而改善，而NOx排放几乎没有变化，但一旦出现爆震情况，则指示热效率降低，NOx排放急剧升高．

Cycle to Cycle Variation Experiment of Homogeneous Charge Compression Ignition Combustion

The experiment on homogeneous charge compression ignition (HCCI) combustion with different octane rating fuels was carried out on a single cylinder engine to research cycle to cycle variation of HCCI combustion. The results indicate that cycle to cycle variation increases with increasing octane rating for constant indicated mean effective pressure (p_i),and at constant octane rating, cycle to cycle variation decreases with increasing p_i.For the fuel with high octane rating, cycle to cycle variation is largely influenced by the engine speed. Especially when engine speed is high, cycle to cycle variation sharply increases with increasing engine speed.Under knocking limit, both the improvements in combustion efficiency and in indicated thermal efficiency and the decreasing in HC and CO emissions can be obtained with decreasing cycle to cycle variation, while almost no increase in NO_x emissions. But when knocking occurs, the indicated thermal efficiency decreases, and NO_x emissions rise sharply.