固体燃料凹腔结构对超声速流动的影响

Effects of cavity on solid fuel scramjet combustor characteristics under supersonic cross flow

针对在超声速来流下燃烧室中增加凹腔结构能否提高固体燃料的掺混效果进行研究。采用基于密度的二阶迎风差分数值方法模拟了固体燃料超燃冲压发动机燃烧室内不同凹腔结构的流场特性,并对燃料气体与来流气体掺混效果进行了分析。对比有无凹腔结构的燃烧室内流场各项特性,结果表明,超声速气流下凹腔结构对增强燃料掺混有明显的效果。对比不同长深比凹腔结构燃烧室中燃料与来流气体的掺混效率,结果表明,随着凹腔深度的增大,燃料和氧气的掺混效率逐渐增大;掺混效率达到了最大值后,再继续增大凹腔深度,掺混效率不会继续增大反而减小。在掺混效率达到最大值时,燃烧室出口处的总压损失也最大。

The goal of this study is to investigate whether the cavity structure can enhance the mixing efficiency in solid fuel scramjet（SFSCRJ）. A numerical simulation of a non-reactive supersonic flowfield in solid fuel scramjet combustor was presented.The turbulence model in the numerical simulations was the Stander k-ε model. A second-order-upwind difference scheme was used for simulating the dynamic flow associated with an axial symmetry. Compared with the combustor without cavity,the combustor with cavity was found to be able to enhance the mixing efficiency apparently. Compared with six combustors with different length-to-depth ratio（L /D）of the cavity,as the cavity L /D ratio decreased,the mixing efficiency firstly increased and then decreased. Results show that the mixing efficiency is not monotonically increasing or decreasing with the variation of the cavity L /D ratio. It reveals that there exists an appropriate cavity L /D ratio regarding the mixing or combustion efficiency and the total pressure loss. So there exists a best L /D ratio to get the best performance of the combustor. The investigation of the cavity L /D ratio would provide some insight into the design considerations of cavity for scramjet.