加力燃烧室双层壁隔热屏综合冷却效率的实验研究

Experimental Study on Overall Cooling Effectiveness of Afterburner Double-Wall Heat Shield

关键词:  加力燃烧室  隔热屏  冲击发散冷却  模化理论  匹配原则  开孔率  综合冷却效率

Key words:  Afterburner  Heat shield  Impingement/effusion cooling  Analogy theory  Matching principle  Opening rate  Overall cooling effectiveness

摘要:

为了研究加力燃烧室双层壁隔热屏的冷却特性，进行了综合冷却效率的模化及关键参数的匹配，通过红外测温技术测量了气膜板主流侧的综合冷却效率分布，研究了冲击孔板开孔率（φ=0.5%，0.6%，0.7%，0.8%）和动量比（I=0.02~1.38）对双层壁隔热屏综合冷却效率的影响。研究结果表明：实验室工况（主流与二次流温度比T_g/T_c=2）相对于发动机工况（T_g/T_c=4）的综合冷却效率偏差在0.054以内。沿着主流的流动方向，气膜平板主流侧的综合冷却效率波动增长。随着动量比的增大，冲击驻点区附近的综合冷却效率得到提升，气膜平板中下游的气膜覆盖形状逐渐消失，气膜平板上游的综合冷却效率增幅较大。随着开孔率的提高，冲击孔和气膜孔排布变密，冲击换热增强及气膜叠加效果提升，使开孔率由0.5%增大到0.8%时，面平均综合冷却效率提高21.2%，而主流和二次流的掺混加强了气膜平板主流侧的换热，导致综合冷却效率的增幅下降。

Abstract:

In order to study the cooling characteristics of the afterburner double-wall heat shield， the overall cooling effectiveness was modeled and the key parameters were matched. The overall cooling effectiveness distribution on the mainstream side of the film plate was measured by using IR thermography. Effects of opening rates of the impingement plate （φ=0.5%，0.6%，0.7%，0.8%） and momentum flux ratios （I=0.02~1.38） on the cooling characteristics were investigated experimentally. The results indicate that the deviation of the overall cooling effectiveness between laboratory conditions （the temperature ratio of mainstream flow to secondary flow T_g/T_c=2） and engine conditions （T_g/T_c=4） is within 0.054. Along the mainstream direction， the overall cooling effectiveness on the mainstream side of the film plate fluctuates and increases. As the momentum flux ratio increases， the overall cooling effectiveness near the impingement stagnation point increases.The shape of the film cover in the middle and downstream region of the film plate gradually disappeared， and the overall cooling effectiveness of upstream region of the film plate increased the most. With the increase of the opening rate， the arrangement of impingement holes and film holes becomes denser， the impingement heat transfer and the film superimposition effect are enhanced， so that when the opening rate increases from 0.5% to 0.8%， the area averaged overall cooling effectiveness increases 21.2%， and the mixing of the mainstream flow and the secondary flow enhances the heat transfer on the mainstream side of the film plate， which leads to a decrease of the overall cooling effectiveness growth rate.