支板构型超燃冲压燃烧室流场数值模拟

Numerical simulations of flowfields in a scramjet combustor with a strut

关键词:  高超音速冲压发动机  燃烧室  支板  湍流  数值仿真

Key words:  Hypersonic ramjet engine  Combustion chamber  Strut~+  Turbulent flow  Numerical simulation

摘要:

数值模拟了带凹腔的支板构型超燃冲压燃烧室内部的流场结构。在计算过程中, 控制方程采用了含组分守恒方程, 并与k ω双方程湍流模型紧耦合的质量平均Navier Stokes方程, 对方程中的对流项采用了空间为二阶精度的TVD格式, 扩散项则采用了二阶中心差分离散。采用在流体力学时间步内的当地积分法克服了非平衡源项的刚性问题, 保持了LU SSOR隐式求解算法的高效率。通过数值模拟, 对比研究了凹腔构型的位置、长深比 (S/H) 对燃料混合性能的影响。结果表明, 长深比大的凹腔增加了燃料在腔内的停留时间, 相应地改善了燃料的混合。位于燃料喷嘴之后的凹腔比位于下游的凹腔更有助于提高燃料的混合效率。

Abstract:

In the present paper, the internal flow fields in scramjet combustion chamber with strut and cavities were simulated numerically by using the Favre-Averaged Navier-Stokes equations with the k-ω two-equation turbulence model. The second order TVD scheme is used for the inviscid flux terms of the equations and a central difference is used for the diffusion terms. Furthermore, using the local integral of the nonequlibrium source terms within local fluid time step and the LU factorization technique, an implicit LU-SSOR hybrid arithmetic without computing the inversion of the iteration matrix is established, guaranteeing the high efficiency of the method in simulating nonequlibrium flow fields. During the simulations, the effects of cavity position and length-to-depth ratio on the performance of fuel mixing are studied comparatively. The results show that, the cavity with large ratio of length to depth increases the residual time of fuel in the cavity field, and accordingly improve the fuel/air mixing. Additionally, the cavity behind normal-wall fuel injectors will give more helps in enhancing the fuel/air mixing efficiency than the cavity locating at the downward far from the injectors does.