高海拔共轨柴油机煤基复合燃料排放的数值模拟

Numerical Simulation on Coal-Based Composite Fuel Emission of Diesel Engine at High Altitude

为分析煤基复合燃料对共轨柴油机高海拔碳烟和NOx排放的影响,基于AVL FIRE数值分析软件,建立煤基复合燃料柴油机高海拔燃烧过程仿真模型并进行试验验证。探究煤基复合燃料柴油机高海拔缸内物理场变化规律和碳烟(Soot)与NOx形成历程。结果表明:随着海拔的升高,煤基复合燃料柴油机缸内气流运动速度最大值减小,最高燃烧温度和燃空当量比增大,NO质量分数减少,但Soot质量分数增多且最大值对应曲轴转角增大。与海拔3 500 m相比,海拔5 500 m煤基复合燃料柴油机燃烧后期NO减少69.8%,Soot增多18.6倍。与燃用柴油相比,煤基复合燃料柴油机燃空当量比降低,NO增多,Soot减少,且海拔越高Soot减少幅度越大,海拔5 500 m时Soot减少83.1%。

To analyze the influence of coal-based composite fuel on the soot and NOx emitted by a diesel engine operating at high altitude,the paper applies AVL FIRE numerical analysis software to simulate the combustion process of the engine,and studies the change of in-cylinder physical field as well as the generation of soot and NOx.Experimental results show that with the elevation of altitude,although the maximal speed of in-cylinder air flow and NO mass fraction would decrease,the maximal combustion temperature and fuel-air equivalence ratio increase as well as the maximum corresponding to the craft angle.At the end of combustion,an engine working at an altitude of 5 500 meters would decrease NO by 69.8 percent while increase soot by 18.6 times more than that at 3 500 meters.Compared to a diesel engine,the engine using coal-based fuel has a lower fuel-air equivalence ratio,more NO emission and less soot.The higher the altitude,the quickly loot would decrease with on 83.1 percent reduction at the altitude of 5 500 meters.