直喷汽油机二次喷射改善冷起动性能的研究  

Researches on Improving GDI Engine Cold-Starting Performance by Two Stage Injection

作　　者：刘光义 柳建辉 孙玉[1] 尚翔宇 邬斌扬[2] 苏万华[2] Liu Guangyi;Liu Jianhui;Sun Yu;Shang Xiangyu;Wu Binyang;Su Wanhua(Commercial Vehicle Technology Center,SAIC Motor Company Limited,Shanghai 200438,China;State Key Laboratory of Engines,Tianjin University,Tianjin 300072,China)

机构地区：[1]上海汽车集团股份有限公司商用车技术中心,上海200438 [2]天津大学内燃机燃烧学国家重点实验室,天津300072

出　　处：《内燃机学报》2019年第6期481-488,共8页Transactions of Csice

摘　　要：通过一台直列4缸汽油机分析了喷油模式对直喷汽油(GDI)发动机冷起动过程及冷态怠速过程的影响.结果表明:通过调整喷油策略可以改变缸内混合气的燃烧过程,在二次喷油比例为0.6∶0.4、喷油定时分别为上止点前300°CA和140°CA、环境温度为-30℃条件下,发动机的燃烧特性最佳,HC排放最低.在车辆冷起动过程中,通过二次喷射可以有效缩短混合气的滞燃期和燃烧持续期,以达到缩短起动时间、提高起动性能的目的.在起动后的怠速阶段,采用二次喷射可以大幅提高发动机的燃烧稳定性,有效消除怠速不稳的问题.在闭环控制阶段,通过二次喷射合理组织缸内混合气分布,可以有效改善减稀混合气造成的车辆抖动问题.此外,缸内混合气燃烧过程的优化可以有效降低冷起动过程的HC和CO排放,但会造成NOx排放的小幅升高.Effects of injection mode on GDI engine’s performance during the cold-starting and warm-up process were studied in detail on an inline 4-cylinder gasoline engine.Bench experiment results show that the distribution of mixture around the spark plug can be changed by adjusting the injection strategy.Best combustion characteristics at low temperature of-30℃are obtained when the two-injection ratio is 0.6 to 0.4,and the injection timing is 300°CA BTDC and 140°CA BTDC respectively,meanwhile,the emission of HC reduces to the minimum level.During the cold-starting process,by adopting split injection,the ignition delay period and the combustion duration of the mixture in the cylinder are dramatically reduced,as a result the start-up time is shorten and the start-up success rate is improved.In the following idling stage,due to the improved combustion stability,the violent fluctuation of idling speed and the idle-wobbling,which is caused by the attenuating mixture in the closed-loop duration,is eliminated thoroughly.Besides,by utilizing two stage injection,the emissions of HC and CO during the cold-starting and after-start phase are greatly reduced,but it would cause a slight increase in NOx emission.

关 键 词：汽油机 冷起动 怠速稳定性 喷油策略 混合气 排放 

分 类 号：TK417[动力工程及工程热物理—动力机械及工程]