组喷孔喷嘴对双对置柴油机喷雾及燃烧的影响

针对双对置柴油机混合气形成困难的特点，采用CONVERGE CFD软件，建立双对置柴油机数值仿真模型。设计3种汇聚型组喷孔喷嘴的喷孔布置方案，研究在保持喷油压力不变的前提下，对3种方案下喷雾、混合气形成和燃烧过程进行分析。结果表明:与传统喷嘴相比，改进后的组喷孔喷嘴对喷雾贯穿距影响较小，有利于缸内湍流动能的提高，加快缸内混合气的形成速率。同时，组喷孔喷嘴使燃油分布更加均匀，分布区域也更广，有利于改善油气混合质量，提高双对置发动机气缸压力和燃烧效率，达到提升双对置发动机性能的效果。其中，第3种组喷孔布置方案下发动机指示功率可提高7.6%。 

Influence of group-hole nozzles on spray and combustion of an opposed piston opposed cylinder diesel engine

With focus on the difficulty of mixture formation of an opposed piston opposed cylinder diesel engine, CONVEGE CFD software was employed to establish the numerical simulation model of an opposed piston opposed cylinder diesel engine. Three arrangements of the converging group-hole nozzle were designed,and without modifying the injection pressure,the fuel spray, mixture formation and combustion process of an opposed piston opposed cylinder diesel engine model were analyzed. The results indicated that the group-hole nozzle had negligible influences on spray penetration distance compared with conventional nozzle. The group-hole nozzle was helpful in improving the in-cylinder turbulence kinetic energy and accelerating the air-fuel mixing rate. Meanwhile, the mixture was evenly distributed and widely spread, helping to improve the quality of mixture and increase the in-cylinder pressure and combustion efficiency as well as improve the engine performance. Among three designs, the indicated power of the engine with the third pattern of converging group-hole increased by 7.6%.