分层当量比混合气抑制爆震的燃烧排放特性研究

针对汽油缸内直喷式(GDI)发动机,利用两次喷射策略形成分层当量比混合气抑制爆震的思路进行了研究,着重分析了两次喷射策略中第二次喷射时刻和比例对燃烧、爆震和排放的影响,并对比了分层当量比混合气与传统的推迟点火时刻和加浓混合气抑制爆震方法的燃烧排放特性差异.研究结果表明:分层当量比混合气能够实现抑制爆震的效果,且浓区混合均匀时可减弱分层对燃烧效率和平均指示压力的降低;分层当量比混合气可利用三效催化剂高效地降低HC、CO和NOx的排放;分层混合气会由于混合不均造成碳烟生成,分区均质的分层混合气组织形式将有助于降低分层带来的碳烟排放;分层当量比混合气抑制爆震可减弱推迟点火时刻对负荷的降低;与加浓抑制爆震方法相比,可显著提高燃油经济性并降低排放.

Research on Combustion and Emissions of Stratified Stoichiometric Mixture for Knocking Suppression

To suppress knocking in GDI engine by stratified stoichiometric mixture(SSM) the two-stage injection strategy was studied.The effects of second injection fraction and timing on combustion and emissions were emphatically analyzed and SSM scheme was also compared with two conventional knock suppressing methods,retarding ignition timing and burning rich mixture.The results show that the SSM can suppress knocking significantly and the deterioration of combustion efficiency and IMEP caused by stratified mixture ...