发动机工况下透平级凹槽叶顶冷却传热性能研究

Investigations on the Heat Transfer and Film Cooling Effect at Squealer Tip of a Turbine Stage under Engine Conditions

采用数值方法研究了发动机工况下透平级凹槽叶顶的冷却传热性能,获得了3种吹风比(M=0.5,1.0,2.0)和2种气膜孔布置(单排叶顶气膜孔、叶顶+压力面侧气膜孔)下凹槽叶顶的传热系数和气膜冷却效率分布。研究表明:凹槽腔室涡、刮削涡和冲击流是影响凹槽叶顶冷却传热性能的主要流场结构。在凹槽腔室涡的作用下,冷却流对凹槽底部前缘及压力侧形成了有效的冷却。在腔室涡与刮削涡的共同作用下,冲击流导致凹槽底部吸力侧形成高传热区。采用单排叶顶气膜孔时,随着吹风比的增大,凹槽叶顶的传热系数减小,气膜冷却效率提高。采用叶顶+压力面侧气膜孔时,与采用单排叶顶气膜孔相比,在吹风比为2.0的条件下,凹槽肩壁的平均传热系数降低了13.89%,平均气膜冷却效率升高了61.45%。

Heat transfer and film cooling effect at squealer tip of a turbine stage were numerically investigated under engine conditions.The heat transfer coefficient and film cooling effectiveness at squealer tip with two cooling hole array arrangements(tip hole-array,and both tip and pressure-side hole-arrays)were obtained at three blowing ratios(M=0.5,1.0 and 2.0).The results show that the squealer cavity vortex,scraping vortex and impingement flow are the three main flow structures that influence the heat transfer and film cooling effect at squealer tip.Due to the influence of squealer cavity vortex,the cooling flow can effectively cool the cavity floor near the leading edge and the pressure side.Under the influences of cavity vortex and scraping vortex,the impingement flow induces a high heat transfer area on cavity floor near suction side.When the tip hole-array is employed,with the increase of blowing ratio,the overall heat transfer coefficient at squealer tip is decreased,and the overall film cooling effectiveness is increased.When both tip and pressure-side hole arrays are employed,compared with the tip hole array,the area-averaged heat transfer coefficient at squealer tip is decreased by 13.89%,and the area-averaged film cooling effectiveness is increased by 61.45%at M=2.0.