发汗冷却中多孔壁面添质通道流动的实验和数值研究

Experimental and Numerical Study on Channel Flow of Porous Wall in Transpiration Cooling

发汗冷却相比常规主动冷却方式是冷却效率更高、覆盖性能更好的热防护技术。为了研究发汗冷却中的添质流动现象,通过带有红外热成像技术的发汗冷却实验平台,在雷诺数1.35×105和总温373K的来流条件下对金属颗粒烧结多孔材料的发汗冷却效果进行了研究,得到了在不同注入率条件下多孔壁面的温度分布,结果显示平均冷却效率与注入率之间近似呈线性关系,当氮气注入率为33.5%时平均冷却效率接近0.45。通过对比单温度方程的局部热平衡模型和双温度方程的局部非热平衡模型的模拟结果,显示局部非热平衡模型能正确反映发汗冷却过程中的换热过程,模拟结果和实验数据具有较高吻合度。模拟结果表明:多孔壁面边界层随注入率的增大而增厚,边界层增厚是发汗冷却具有较高冷却效率的原因之一。

Transpiration cooling has the advantages of higher cooling efficiency and better coverage compared with the conventional cooling method. It is one of the preferred technologies for the cooling system in the next generation of hypersonic vehicles. In this paper,the transpiration cooling efficiency of metal sintered porous media has been experimentally investigated under the condition of Reynolds number 1.35×105 and total temperature 373 K. The surface temperatures of the porous wall under various blowing ratio are measured using the infrared thermal imaging technique. The experimental results show that the average cooling efficiency is approximately linear with the blowing ratio,the average cooling efficiency is close to 0.45 when the blowing ratio is 33.5%. By comparing between the local thermal equilibrium model of the one-temperature equation and the local thermal non-equilibrium model of the two-temperature equation,it can be considered that the local thermal non-equilibrium model can correctly reflect the heat transfer in transpiration cooling process. The simulation results are in good agreement with the experimental data. The simulation results show that the boundary layer of the porous wall is significantly affected by the blowing ratio,and the thickening of the boundary layer is one of the reasons for the high cooling efficiency of the transpiration cooling.