混合动力系统用发动机冷起动排放

Hybrid Engine Cold Start Emissions

通过分析发动机起动点火、喷油及进气量控制策略,确定了发动机冷起动过程中影响HC和NOx排放的关键参数为:拖转转速、起始喷油转速和点火推迟.研究表明:较高的拖转转速可以减少发动机起动所需的燃油量、改善燃油雾化质量、促进完全燃烧、降低HC排放;而过高的拖转转速则会恶化NOx排放;推迟点火可以有效地加速催化器起燃、显著地降低排放,若点火太迟只能有限加速催化器起燃,而且会增加油耗、使燃烧不稳定、增加失火,HC及NOx排放同时恶化.通过研究排放规律,选定了合适的冷起动参数,为今后精确排放标定奠定了基础.

The key parameters influencing cold start HC and NOx emissions,including motoring speed,＂fuel-on＂ speed and ignition retard,were analyzed by studying engine start ignition,fuel delivery and air charging strategies.The results show that higher motoring speed helps to reduce start fuel,improves fuel atomization and completes combustion,and thus reducing the HC emission.But too high a motoring speed will deteriorate NOx emission.Ignition retard can accelerate TWC light-off effectively,but too much of it will cause unstable combustion and misfire,and deteriorate HC and NOx emissions simultaneously.By studying the law of start emission,the optimized parameters were selected,laying a foundation for further accurate emission calibration.