甲醇缸内直喷发动机分层燃烧和均质燃烧的试验研究

摘要

In a methanol direct-injection spark-ignition (DISI) engine retrofitted from a 4-cylinder diesel engine, the fuel needs to be injected into the cylinder near the end of compression stroke to realize the stratified combustion at partial loads for improving fuel economy. However, at high loads, the fuel needs to be injected into cylinder during intake stroke to realize the homogeneous combustion for achieving high power output. The results show that the methanol DISI engine can operate within the excessive air ratio of 2. 23 and its maximum brake thermal efficiency reaches 35. 3%. The methanol DISI engine exhibits higher power output than that of the original diesel engine. The cyclic variations of imep maintains low under a wide range of operating conditions, which shows a stable combustion. NO_x and soot emissions can be de-creased simultaneously.%在一台4缸柴油机改造的火花点火甲醇缸内直喷发动机上,中低负荷时采用分层燃烧来实现好的燃油经济性,高负荷时采用均质燃烧来获得好的动力性能.试验结果表明,甲醇缸内直喷发动机可以实现过量空气系数为2.23的分层稀薄燃烧;发动机的有效热效率最高可达35.3%,远高于普通汽油机;低速转矩大,动力性超过原机水平;在宽广的转速和负荷范围下平均指示压力的循环变动较小,燃烧稳定性好;该甲醇发动机可以实现NO_x和碳烟的同时降低.