圆形斜孔气膜冷却性能的试验研究

Experimental Study on Film Cooling Effectiveness of Slant Holes

设计了高温低速风洞试验台,并利用红外热成像测温技术对平板单孔和排孔的射流冷却特性进行了试验研究.使用具有高精度和高空间分辨率的红外热像系统测量了平板表面温度,通过埋在平板内的热电偶校正红外热像仪温度并建立了校正关系.通过气膜冷却效率分布分析了气膜冷却效果,给出了在50℃、196℃和267℃时不同位置的气膜冷却效率.结果表明:在吹气比M=0.5时,动量较低的冷却射流易贴附于壁面形成一层冷却气膜对其加以保护;当吹气比M不断增大时,换热增强,冷却效率提高;当M=0.1左右时,孔下游冷却区域增大,有良好冷却效果;当M>2时,射流的动量已大于主流动量,射流孔附近两股换热增强,孔附近冷却效果好,而下游冷却面积变小.

A low-speed high-temperature wind tunnel was designed to study the film cooling effectiveness with injection respectively through a single hole and a row of holes in a flat plate using infrared thermography technique.An infrared thermography data acquisition system with high accuracy and high spatial resolusion was used for obtaining surface temperature mappings on the flat plate.Accurate local temperature data were achieved by an in situ calibration procedure with the help of thermocouples embedded in the test plate,while a correction relationship established.To describe the integral film cooling performance,detailed film-cooling effectiveness distributions at 50 ℃,196 ℃ and 267 ℃ were used for evaluating the thermal performance of a single hole and a row of slant holes.Results show that in the case of a blowing rate M=0.5,the injection flow of low momentum is easy to form a cooling and protection film on the wall;when M grows,the heat transfer is to be enhanced,resulting in higher cooling effectiveness;when M is around 0.1,the cooling area in downstream of hole shall be enlarged,hence better cooling effect achieved;when M2,the momentum of injection flow is already larger than that of the main flow,leading to enhancement of heat transfer between the two flows around the injection hole,resulting in better cooling effect at that area,but reduced cooling area in the downstream.