摘要
爆震一直是汽油机提高压缩比以改善燃油经济性的主要障碍。提出了用"分层当量比"和"分区均质"的混合气组织方式抑制汽油机爆震的思路,在缸内直喷(GDI)汽油机上,通过两次喷射策略配合一定的燃烧室形状形成不同的分层混合气组织形式,对比研究了当量比下均质混合气和分层混合气对爆震的影响。结果表明:在当量比条件下利用两次喷射形成分层混合气可以显著降低爆震强度,并且随着第二次喷油时刻推后或第二次喷油比例增大,爆震强度逐渐降低;分层混合气浓区混合均匀时可加快燃烧速度,燃烧相位提前,爆震强度降低,浓区混合不均则会使得燃烧速度减小,燃烧相位推后,最大爆发压力和压力升高率降低;混合气分层之后,HC排放变化不大,NO_x排放有所降低,CO排放增加;分层混合气中间浓区混合均匀会减弱分层对燃烧和排放的恶化。
Knocking is the main obstacle to increase compression ratio for improving fuel economy. In this paper, the concept of stratified stoichiometric mixture and two-zone homogeneous charge was proposed to suppress knocking in gasoline engines. The effect on knocking of homogeneous and stratified mixture was studied in a GDI engine using the two-stage injection and the specially designed combustion chamber. The experimental results show that the stratified stoichiometric mixture can suppress the knock significantly, and the knocking intensity decreases gradually as the second fuel mass increasing or injection timing retarding. The combustion rate increases and the combustion phase advances when the rich zone of the stratified mixture is homogeneous. While the combustion rate decreases, the combustion phase retards, the peak pressure and the pressure rise rate decreases when the rich zone of the stratified mixture is inhomogeneous. HC emissions show little variation, NOx emissions decrease slightly and the CO emission increases largely, Two-zone Homogeneous Charge can eliminate combustion and emission deterioration by using the stratified mixture.
出处
《内燃机学报》
EI
CAS
CSCD
北大核心
2009年第6期534-539,共6页
Transactions of Csice
基金
国家"863"项目课题(2006AA110106)
关键词
缸内直喷
爆震
分层当量比
分区均质
GDI
Knocking
Stratified stoichiometric mixture
Two-zone homogeneous charge
