双阶段燃烧低温阶段HC及CO排放的优化路径

Strategies to Optimize HC and CO Emissions in Low-Temperature Stage of Two-Stage Combustion

通过一台CA6DL电控高压共轨柴油机探究了降低双阶段燃烧低温阶段HC和CO排放的方法.结果表明:在具有低温燃烧(LTC)典型特性的低温燃烧阶段中,采用单次喷射可以通过增加喷油量及推迟喷油正时的方式提高缸内燃烧温度,降低HC和CO排放;增加喷油次数可以减少每次喷射的喷油量,在维持氮氧化物(NO_x)排放基本不变的情况下,可通过调节喷油参数的方式优化油气混合状态,从而达到更好的燃烧和排放效果;在不同喷油策略中,均匀分配油量的喷油策略可避免因油量分配不均所造成缸内燃烧温度过高或过低而带来的NO_x或HC、CO的急剧增长,其综合效果最佳.

Optimization strategies of reducing HC and CO emissions were studied experimentally on a turbocharged and inter-cooled common rail diesel engine of CA6DL during the low temperature stage of two-stage combustion proc- ess. The results show that during the typical low-temperature combustion （LTC）stage with single injection case, increasing fuel injection quantity and delaying the injection timing can increase the combustion temperature and thus reduce HC and CO emissions. Furthermore, better combustion efficiency and HC/CO emissions can be obtained with NOx emissions almost unchanged by increasing injection times due to the decrease of the fuel amount per injection and improving fuel/air mixing condition. The best optimization strategy among different injection strategies is the uniform distribution of fuel injection strategy as it can avoid the sharp increase of NOx or HC and CO caused by extremely high or low combustion temperature in cylinder.