双层壳型涡轮叶片中冲击旋流换热增益效果试验

Experiments on heat transfer enhancement with vortex in a double-decker jet/film cooling structure

关键词:  涡轮  涡轮叶片  冲击  旋流+  换热+

Key words:  Tubine  Turbine blade  Shock  Vortex+  Heat transfer+

摘要:

以双层壳型涡轮叶片内冷通道中旋流换热特性为研究对象,采用热膜法,对双层壳型冷却结构中的狭小受限通道中,旋流作用下换热特性的变化规律开展了细致的试验研究。重点分析了冷却空气的旋流作用对换热的强化增益效果。试验中通过改变冲击Re数(10 000～20 000),冲击间距和冲击孔直径之比H/D(0.35～1.7)等参数,研究了其对旋流的形成及内表面局部换热系数的影响规律。研究发现:由于双层壳型叶片内冷通道的空间受限,冷却空气在通道内形成了旋流结构,该旋流结构显著影响了内表面的局部换热系数并可以有效提高换热效果。研究结果表明:内表面局部换热系数对冲击间距和冲击孔直径之比H/D最为敏感,对于不同冲击Re数,存在一个最佳的H/D使得旋流换热增益效果达到最大(Re=10 000时,最佳H/D为0.95;Re=15 000,20 000,最佳H/D=0.63)。

Abstract:

Experiments were conducted to investigate the local heat transter in the narrow space of a double-decker impingement/film structure.And the heat transfer enhancement according to vortex were also studied.The jet Reynolds number Re(10 000～20 000) and the ratio of jet impingement distance to the diameter of jet holes H/D(0.35～1.7) were changed to study the induced vortex with impingement.Then the rules of local heat transfer coefficients of inner face varying with these parameters were concluded.All the results show that the local Nusselt number of inner surface is affected greatly by the vortex,which is induced by the jet in a limited space,and the heat transfer rate can be enhanced by the vortex.Under different jet Reynolds number conditions,there exists a certain H/D which results in the maximum Nusselts number.In experiments,H/D equals 0.95 when the jet Reynolds number is 10 000,and the value of H/D changs to be 0.63 while the Re are 15 000 and 20 000.