乙醇-柴油混合燃料燃烧和颗粒尺寸分布

摘要

通过台架试验研究了乙醇的添加对柴油机燃烧和排放的影响,尤其对排气中颗粒物尺寸分布进行了深入探讨.结果表明:随着混合燃料中乙醇质量分数的增加,滞燃期增长,燃烧持续期缩短,同时发动机的等效燃油消耗率降低,热效率略有增加;在颗粒物(PM)排放方面,乙醇的添加使得积聚态颗粒数量减少,核态颗粒数量明显增加,尺寸分布的峰值向小粒径方向移动;颗粒的总数量浓度呈上升趋势,但颗粒物的总质量浓度减少.此外,乙醇的添加会增加氮氧化物(NOx)排放.%An experiment was performed to investigate the combustion and emission on a four-cylinder compressionignition direct-injection (CIDI)engine fuelled with ethanol-diesel blends.Especially,the particle size distribution function (PSDF) in the exhaust system was explored in detail.The results show that the ignition delay becomes longer and the combustion duration becomes shorter with the addition of ethanol.The brake thermal efficiency is improved with the increase of ethanol fraction.Furthermore,ethanol addition decreases the number of accumulation particles slightly,but increases the number of nucleation particles.With the increase of ethanol addition,the number concentration of all soot particles shows an ascendant trend.On the contrary,the mass concentration of soot particles decreases.Meanwhile,the peak of PSDF moves toward the small size direction.In addition,NOx emissions increase with the increase of ethanol fraction.