Thermal Analyses of Active-Cooled Strut in RBCC Engine

Fei Qin,Wenqiang Li,Zhiyuan Hou,Guoqiang He,Duo Zhang,Tingting Jing

doi:10.1051/jnwpu/20183650919

Abstract

Fuel-injection strut is an efficient way to increase the depth of fuel penetration and strengthen the mixing process of hot gas in supersonic combustor. With a validated numerical model, this article analyzed the effects of leading edge's radius, wall thickness and mass flow distribution on cooling efficiency of fuel-injection strut and proposed an optimizing strategy for active-cooled strut. Results showed that the larger radius of leading edge not only decreased the heat flux on the leading edge, but also has a negative effect on the aerodynamic performance of strut; and a thinner wall could enhance the cooling efficiency and uniformize the temperature distribution of the wedge; furthermore, the flow distribution of inlet coolant had a significant impact on the heat transfer and flow processes, an optimized way of flow distribution was obtained by comparing three different ways of distribution.

Highlights

an efficient way to increase the depth of fuel penetration
this article analyzed the effects of leading edge′s radius
Results showed that the larger radius of leading edge not only decreased the heat flux

Summary

Introduction

摘要:针对典型的宽域工作火箭冲压组合循环发动机中的主动冷却燃料支板的基准构型,采用经过校验的数值模拟方法,开展了前缘半径、壁厚、流量分配方式对支板冷却效果的影响因素分析,完成了支板主动冷却通道的几何参数及流量分配策略的参数优选研究。结果表明,在其他参数相同的条件下,前缘热流随着前缘半径的增大而减小,且横截面温度分布更加均匀,但同时对支板的气动性能影响也逐渐增大;另外,壁厚的增大会降低支板的冷却效果,且壁厚越小,在前缘上的热流分布越均匀; 同时,通过对比 3 种冷却剂分配方式的数值模拟结果可知,冷却剂更多地分配给前缘等受热严重区域可以增强特征区域的冷却效果,但全部集中在支板前缘会增大通道内压力损失,因此由尖劈部分的多个通道进入的分配方案最优,既能提高前缘冷却效率,又能保证对其他部分的有效冷却。通过开展支板主动冷却通道布局优化和影响规律分析,显著降低了燃料支板对冷却流量的需求,并为燃料支板的主动冷却结构设计提供了依据。目前,常见的高温合金材料的许用温度上限为 1 250 K[9] ,而高温陶瓷基复合材料( 如 C / SiC) ,虽然可以在 1 923 K 条件下长时间工作,但仍无法满足 RBCC 发动机燃料支板长时间可重复使用的要求,因此必须对支板进行有效的主动热防护设计。虽然国内外学者开展了关于复合材料再生冷却、液膜冷却和发汗冷却等方面的大量研究,但目前,上述本文以典型宽域多模态 RBCC 模型发动机为应用背景,采用经过校验的高精度数值仿真方法,开展基于高温合金材料的再生冷却支板传热特性的三维数值模拟研究,分析了前缘半径、壁厚、流量分配方式对支板冷却效果的影响规律,提出了燃料支板主动冷却结构的初步优化设计方法和关键设计参数的选取依据。

Results

Conclusion