等直段直径对固体燃料超燃冲压发动机燃烧室性能的影响

Effects of Diameter of Cylindrical Section on Flowfield Characteristics of Solid Fuel Scramjet Combustor

关键词:  固体燃料超燃冲压发动机  数值模拟  流场特性  燃烧效率  总压损失  燃烧室推力

Key words:  Solid fuel scramjet  Numerical simulation  Flow field characteristics  Combustion efficiency  Total pressure loss  Combustor thrust

摘要:

为了研究燃烧室内等直段直径的尺寸对固体燃料超燃冲压发动机燃烧室性能及流场特性的影响，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，对不同等直段直径燃烧室工作过程进行数值模拟。采用基于压力的二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 k-ω模型。PMMA燃料进口边界由用户自定义函数的方式给定，分析不同等直段直径下超燃冲压发动机燃烧室内流场特性及其性能变化。数值模拟结果显示:随着等直段直径的增大，燃烧室可由壅塞状态转变为超声速流动状态，增大至某一数值(约为16.5mm)附近时，燃烧室出口可以达到完全膨胀状态。同时，燃烧室的燃烧效率逐渐增大，出口处燃烧效率由62.45%增大至72.74%。总压损失也逐渐增大，出口处最大值可达52%，而燃烧室推力逐渐减小。

Abstract:

In order to investigate the effects of the diameter of cylindrical section on the solid fuel scramjet combustor performance and the flowfield characteristics，based on a solid fuel scramjet experimental data，the numerical investigations concerning about the characteristics of the flow field in the solid fuel scramjet and the combustor performance are carried out when the diameter of the cylindrical section is changed. 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 SST k-ω model. The boundary of PMMA solid fuel was defined as the user defined function way. The numerical simulation results indicate that with the increasing of the diameter of the cylindrical section，until the cylindrical section is open，the combustor will not be choked and the mainstream in the combustor becomes supersonic. In certain size of the cylindrical section diameter (about dcyl=16.5mm)，the outlet of the combustor is optimum-expansion. Generally，as the diameter of the cylindrical section increases，the combustion efficiency increases from 62.45% to 72.74% at outlet，while the total pressure loss also increases，which gets an maximum value of 52% at outlet in certain model，and the combustor thrust decreases.