燃烧室长度对固体燃料超燃冲压发动机燃烧室性能的影响

基于国外研究者完成的固体燃料超燃冲压发动机的实验数据,通过分别改变燃烧室等直段长度和扩张段长度,对不同总长的燃烧室工作过程进行数值模拟.采用基于压力的2阶迎风差分数值方法,物理模型为轴对称结构,燃烧模型采用有限速率/涡耗散模型(finite-rate/eddy-dissipation),湍流模型采用SST(shear stress transport) k-ω模型.聚甲基丙烯酸甲酯(PMMA)燃料进口边界由用户自定义函数的方式给定,分别分析了不同长度,即不同等直段长度或扩张段长度下超燃冲压发动机燃烧室内流场特性及其性能变化.结果表明:随着等直段长度的增大,燃烧室出口处燃烧效率逐渐减小,从72.74%降低至66.81%,而燃烧室内总压损失逐渐减小,燃烧室推力逐渐增大,可由85.83N增加至108.55N;改变扩张段长度,发现扩长段长度变化对燃烧室流场结构的影响较小,随着扩张段长度的增大,燃烧室出口燃烧效率和燃烧室推力都略微减小.在燃烧室长度的设计范围内,增大等直段的长度要比增大扩张段长度对提升燃烧室各项性能有帮助. 

Effects of combustor length on solid fuel scramjet combustor performance

Based on foreign researchers' experimental data about solid fuel scramjet's, the numerical simulations concerning about the characteristics of the flow field in the solid fuel scramjet and the combustor performance were described by changing the length of the cylindrical section and the length of the diverging section respectively. A second-order-upwind difference scheme and the pressure-based solver were used for simulating the dynamic flow associated with an axis symmetric physical model. The combustion model in the numerical simulations was finite-rate/eddy-dissipation and the turbulence model was the shear stress transport(SST) k-ω model. The boundary of polymethyl methacrylate(PMMA) solid fuel was defined by the user-defined function. Results indicate that as the length of the cylindrical section increases, the combustion efficiency at combustor outlet decreases from 72.74% to 66.81%, while the total pressure loss decreases, the thrust in the combustor increases from 85.83N to 108.55N. The variation of the length of diverging section makes rarely difference on the flowfield characteristics of the combustor, as the length of the diverging section increases, both the combustion efficiency at combustor outlet and the thrust in the combustor slightly decrease. In the design range of combustor length, if the length of the combustor needs to be increased, it's better to increase the length of the cylindrical section rather than the length of the diverging section.