基于火焰面模型的超声速燃烧混合LES/RANS模拟

Hybrid LES/RANS simulation of supersonic combustionusing flamelet model

关键词:  燃烧室  大涡模拟  火焰面  湍流燃烧

Key words:  Combustion chamber  Large eddy simulation  Flame-let  Turbulent combustion

摘要:

为了明晰超燃冲压发动机燃烧室内部燃烧过程的细节,建立了超声速湍流燃烧稳态火焰面亚格子模型,并采用混合LES/RANS方法对氢燃料超燃冲压发动机进行算例验证。控制方程对流项用五阶精度WENO格式离散,时间方向采用二阶Runge-Kutta方法。研究表明:(1)冷流流场中燃料分布与大尺度结构分布相似,说明混合过程受大涡控制；(2)燃烧流场中涡的尺寸明显变大,且仅存在于火焰面上,另外温度分布和主要生成物分布与涡量云图基本相同,说明燃烧过程也由大涡控制；(3)时均计算结果与实验阴影基本符合,速度剖面和温度剖面与实验测量值定性一致,说明本文的数值模拟方法和燃烧模型可以较好地描述和预测超声速流动燃烧过程。

Abstract:

To investigate detailed combustion process in scramjet,flamelet sub-grid model is presented for supersonic turbulent combustion, and hybrid LES/RANS method is used to simulate supersonic flow and combustion in the hydrogen fueled scramjet．Governing equations of large scale eddies were solved with fifth-order WENO scheme, and Runge-Kutta scheme was adopted for time iteration. The results show:(1) the distribution of fuel in non-reacting flow is similar to vortex, which reveals that mixing is controlled by large eddy scales; (2)vortex becomes larger and lies on the flame surface in reacting flow, also the distribution of temperature and water are similar to vortex, which reveal that combustion is controlled by large eddy scales; (3)numerical results obtained good agreement with shadow pictures, velocity measurements, and temperature measurements qualitatively and quantitatively, which reveal that the method and combustion model in this paper can predict both the non-reacting and reacting flow-fields reasonably well.