柴油转子发动机缸内混合气分层燃烧特性的研究

Investigation of the mixture stratified combustion characteristics in a diesel rotary engine

基于实验验证的三维动态数值计算模型,研究了柴油转子发动机的分层燃烧特性,获得了喷油角度对缸内混合气运动、燃烧和排放特性的影响。结果表明:增大喷油角度,混合气整体向燃烧室的后部转移;引燃时刻,燃料集中在点火腔周边且呈现前浓后稀的分层规律。结合转子发动机独特的火焰向前传播特性,在浓度适中的条件下,较多的燃料集中燃烧室后部且靠近点火腔是较理想的方案。增大喷油角度,缸内的混合气燃烧速率加快,燃烧压力和压力峰值(P_(max))增大。采用较大的喷油角度,发动机的燃烧性能和动力性能得到提升,但是碳烟(soot)和二氧化碳(CO_(2))有一定增加。

Based on the experimentally verified three-dimensional dynamic numerical calculation model,stratified combustion characteristics of the diesel rotary engine were studied.Then,the influence of different fuel injection angles on the mixture movement,combustion and emissions performance in the combustion chamber were obtained.The result showed that with the increase of the fuel injection angle,the mixture moved towards the rear of the combustion chamber.At the ignition timing,the fuel was concentrated around the ignition chamber and presented a stratified distribution rule that was richer in the front region and thinner in the back region.Combined with the unique flame-forward-propagation of the rotary engine,at a moderate fuel concentration condition,more fuel distributed at the rear of the combustion chamber and close to the ignition chamber was better.With increasing the fuel injection angle,the mixture burnt rate was accelerated,both the combustion pressure in-cylinder and the peak pressure(P_(max))were also increased.Overall,when a large fuel injection angle was used,the engine combustion and power performance were improved,while the soot and carbon dioxide(CO_(2))increased a little.