基于RANS和LES湍流模型的二甲醚超临界喷雾数值模拟

Numerical simulation of DME supercritical spray based on RANS and LES turbulence models

分别采用RANS和LES湍流模型耦合KH-RT破碎模型对二甲醚超临界非燃烧喷雾实验进行数值模拟,研究两种湍流模型的适用性,并对比分析二甲醚亚临界喷雾和异辛烷超临界喷雾的发展过程。同时,基于LES湍流模型探讨了环境温度和压力以及喷射温度和压力的变化对二甲醚超临界工况下喷雾贯穿距的影响。结果表明,RANS和LES湍流模型均能较好地模拟二甲醚超临界喷雾,LES湍流模型的模拟结果与喷雾实验观察结果更吻合;与二甲醚亚临界喷雾相比,其超临界喷雾的雾化效果更好;在相同初始条件下,二甲醚超临界喷雾的雾化效果要优于异辛烷超临界喷雾;二甲醚超临界喷雾贯穿距随环境温度、燃油喷射温度和喷射压力的升高而增大,随环境压力的升高而减小。

Coupled with KH-RT breakup model,RANS and LES turbulence models were used to simulate dimethyl ether(DME)supercritical non-combustion spray experiment respectively.Applicability of two turbulence models was discussed,and the developing processes of DME subcritical spray and isooctane supercritical spray were also studied,serving as contrasts.Meanwhile,based on LES turbulence model,the effects of ambient temperature and pressure as well as injection temperature and pressure on the penetration distance of DME supercritical spray were analyzed.The results show that both RANS and LES models can simulate DME supercritical spray very well while the results of LES model are in better agreement with experimental observations.The atomization effect of DME supercritical spray prevails over that of DME subcritical spray,and that of isooctane supercritical spray in the same initial conditions.DME spray penetration distance increases as the ambient temperature,fuel temperature and injection pressure rise,but decreases as the ambient pressure rises.