支板增强混合超声速燃烧的大涡模拟研究

Large eddy simulation of strut enhanced mixing for supersonic combustion

基于开放源代码软件Open FOAM,建立了三维可压缩反应流动大涡模拟求解器,采用了Pa SR亚格子燃烧模型和27步的氢气-空气反应动力学机理,开展了支板增强混合的超声速燃烧大涡模拟研究,对比了滑移和粘性2种不同壁面边界条件的影响。计算结果表明,不同截面上的平均轴向速度和温度与实验数据吻合良好,较好捕捉了超声速扩散燃烧的火焰空间发展过程。详细讨论了剪切层增长、发展和破碎对燃烧过程的影响,揭示了支板后旋涡脱落与燃烧过程的耦合作用,区分了支板下游亚声速区和超声速区内不同的掺混模式。利用化学爆炸模式分析方法,获取了爆炸化学过程及其特征时间尺度,得到了详细的火焰结构及其稳定机制。

Large Eddy Simulation（ LES） of supersonic combustion in a model scramjet combustor based on an Open Source Field Operation and Manipulation（ Open OAM） computing platform was established,with two different wall boundary conditions,i.e. slip and viscous walls applied. The three-dimensional LES solver,which adopts a Partially Stirred Reactor（ Pa SR） sub-grid combustion model along with a skeleton 27 steps hydrogen chemical kinetics,was used to study strut-enhanced mixing and combustion. LES results show that mean axial velocity and temperature at different cross sections match well with experimental data,and spatial evolution of the supersonic diffusion flame is well captured. Effects of shear layers growth,development and breaking down on combustion processes were discussed in detail,and the coupling effects with vortex shedding at the strut base were revealed. Different mixing modes were recognized after the strut where subsonic and supersonic flows co-exist. Explosive chemical processes and their characteristic time scales were acquired by the Chemical Explosive Mode Analysis（ CEMA） method,and the detailed structure and stabilization mechanism of the flame was identified.