转子叶片径向受限的“冲击-气膜出流”冷却结构流动与换热

Flow and heat transfer characteristics of “impingement-film cooling”configuration in limited space of rotating blade

关键词:  冲击冷却  旋转  涡轮叶片冷却  航空推进  换热特性  流动特性  

Key words:  Impinging cooling  Rotation  Cooling of turbine blade  Aerospace propulsion system  Heat transfer characteristic  Fluid characteristic

摘要:

为揭示转子叶片径向受限的“冲击-气膜出流”冷却结构流动换热规律,以某型双层壁叶片肋化分割形成的冷却单元为研究对象,通过数值模拟的方式,对冲击雷诺数Re_j,旋转数Ro,无因次温比(T_w-T_f)/T_w等参数变化下流场和换热特性变化规律展开研究。结果表明:在哥氏力和离心力作用下,受限空间内存在射流偏转、径向二次流动以及二次冲击等现象；流动的径向受限可抑制射流偏转,强化冲击换热；相同的旋转数Ro下,逆转向冲击(叶背区)换热努赛尔数Nu比顺转向冲击(叶盆区)高8%。在研究的参数范围内,数值模拟和试验结果说明径向受限周向出流结构能有效的抑制旋转对换热的削弱。

Abstract:

In order to obtain the rule of flow and heat transfer of “impingement-film cooling” configuration in limited space of rotating blade, numerical investigation was carried out to study the effects of jet Reynolds numbers Re_j, rotation numbers Ro and wall-to-jet temperature difference ratios (T_w-T_f)/T_w. The results show that in the cooling cell, there is deflexion of impinging flow,secondary flow due to Coriolis and centrifugal forces and so on. Besides, the limited space and sparse film cooling stream can increase high heat transfer coefficient on the stagnation point of impingement. Moreover, rotation negative effects to impingement is stronger with same direction impingement (in basin region) than with reverse direction impingement (in back region).Finally, the results about Nu with varying condition of rotation prove that the structure with limited space and sparse film holes can leash the reduction of efficiency of heat transfer due to the rotation.