新欧拉模型下不同湍流模型对喷雾的数值分析

摘要

For a fuel spray in internal combustion engine,there is actually a continuous liquid phase near the nozzle outlet,hence,a continuous phase model is necessary to study the near-field characteristics.However,up to now,most studies on engine spray have ignored this phenomenon.In this work,a new mass-averaged Eulerian model is used to simulate the injection process of ECN spray A.Five different turbulence models are tested to study their effects on the spray characteristics.Comparisons of the spray penetrations,fuel volume fraction distributions,spray profiles and radial development to the measurement data show that in the range of 3 mm downstream from the nozzle outlet,the Realizable κ-ε,RNG κ-ε,high density ratio κ-ε turbulence models provide similar results.However,in the area beyond 3 mm,the high density ratio κ-ε turbulence model shows an evident advantage.%内燃机燃油喷雾中喷嘴近场实际为连续液相状态,需要采用连续相模型来进行研究.然而,目前大多数研究均忽略此现象,采用Vallet提出的质量平均新欧拉模型对ECN Spray A的喷射过程进行模拟.在RANS框架内,研究了5种不同湍流模型对喷射过程的影响.分别计算了喷雾的贯穿距、体积分数分布及喷射外形等特性,并与试验数据进行对比.结果表明:在喷射出口下游的3mm范围内,Realizable κ-ε、RNG κ-ε和高密度比κ-ε (HDR κ-ε)模型具有相似的求解结果;但在3mm以外的区域,HDR κ-ε表现出了明显的优势.除HDRκ-ε湍流模型外,其他所有模型均给出较大的喷雾锥角和较小的贯穿距,表明HDR κ-ε模型中的修正项产生了增大喷雾速度和贯穿距的效果.所以,对于具有大密度比的近场喷射流,HDR κ-ε具有较好的适用性.