煤油超燃冲压发动机两相流场数值模拟(I)数值校验及总体流场特征

Numerical investigation on two phase flow of akerosene-fueled scramjet with 3D cavity(I) Numerical calibration and characteristics of general flow

关键词:  冲压喷气发动机  超音速燃烧  二相流  湍流  数值仿真

Key words:  Ramjet engine  Supersonic combustion  Two phase flow, Turbulent flow  Numerical simulation

摘要:

针对一种带三维导流型凹槽的煤油超燃冲压发动机,考虑两相(颗粒随机轨道方法)、湍流(Menter的SSTk ω模型)和多步燃烧机理(代用燃料C12H23的17组分30步化学反应机理),对飞行马赫数M0为4和6的典型工况开展了初步数值研究。结果流道壁面压强分布与试验值取得了较好的吻合,不过M0=6工况的第一凹槽组附近的存在约23%的数值误差。给出了误差原因。进一步分析表明(1)M0=6工况的分段燃料喷注对整体燃烧产生了有利影响,导致了较高的燃烧效率。(2)M0=4工况采用了不合理喷注参数,结果煤油穿透深度不足,获得了较低的燃烧效率。(3)三维导流型凹槽附近的湍流效应明显,对掺混产生了有利影响。不过超声速主流的湍流强度远大于亚声速主流情况。

Abstract:

A kerosene-fueled scramjet with 3D cavity was numerically investigated.The main characteristic of this kind of cavity is its special designed slots opened in the upstream of the cavity.The simulations include two typical cases of flying mach number,which are 4 and 6,respectively.One-staged injection is used in the first case while two-staged injection is used in the latter. The mathematical methods include particle stochastic trajectory model for two phase flow, SST k-ω model for turbulence, and C₁₂H₂₃’s 17 species and 30 step reactions model for kerosene’s multi-step chemistry.The side wall’s numerical results　for static pressure were calibrated with experimental values　and　it which shows a good agreement, except an error of 23% occurs in the cavity part of M₀=6 case. The general flow analysis shows particle collision and secondary atomization caused by the asymmetry injection and combustion exist in that case but it was ignored by present numerical model because of huge computational cost.Further analysis shows: （1） M₀=6 case has a high combustion efficiency by staged fuel injection,while M₀=4 case has a low combustion efficiency by low fuel injection pressure.（2） The supersonic state of primary flow above the cavity gives much higher turbulence intensity than subsonic state, which is helpful for mixing.