激波对超声速气膜冷却流动换热特性影响研究

Effects of Incident Shock on Flow and Heat Transfer Characteristics of Supersonic Film Cooling

关键词:  主动热防护  超声速气膜冷却  入射激波  绝热冷效  换热系数

Key words:  Active thermal protection  Supersonic film cooling  Incident shock  Adiabatic cooling efficiency  Heat transfer coefficient

摘要:

为研究激波对超声速气膜冷却流动换热的影响机理，利用数值模拟方法在三种冷气射流马赫数（Ma=1.2，1.5，1.8）下改变激波入射角度（θ=2°，4°，8°），对绝热冷效与壁面换热系数的变化开展研究。结果表明，激波对绝热冷效与壁面换热系数的影响可以根据当地流动情况与主射流掺混程度划分为四个影响区域；入射激波增强使逆压增大，引起分离涡范围增加并使边界层再附影响区内的主射流掺混强度增强，导致冷却效果的恶化；高冷气射流马赫数通过推移边界层分离位置与减弱分离涡后主射流掺混强度来对冷却效果受激波影响的恶化起到补偿作用。综合来看，激波入射引起超声速气膜冷却综合冷效下降，而在低射流马赫数时提高射流马赫数可使综合冷效最大提高80.6%。

Abstract:

To study the influence mechanism of incident shock on the flow and heat transfer characteristics of supersonic film cooling， based on the method of numerical simulation， the changes of adiabatic cooling effectiveness and wall heat transfer coefficient were studied by changing the incident angle of shock wave （θ=2°，4°，8°） under three kinds of cooling air injection Mach number（Ma=1.2， 1.5， 1.8）. The results show that the effects of shock wave on adiabatic cooling effectiveness and wall heat transfer coefficient could be divided into four regions according to the local flow characteristic and the interaction intensity between the mainflow and cooling jet. The strengthened incident shock wave increased the adverse pressure， caused the separation vortex enlarged and made the interaction intensity enhanced in the boundary layer reattachment region， which will deteriorate the cooling performance. The increase of the cooling jet Mach number shifted the boundary layer separation position and weakened the interaction intensity after the separation vortex which could compensate for the deterioration of the cooling performance caused by the incident shock. In general， the overall cooling performance decreased with the action of incident shock， but it could be greatly improved by increasing the jet Mach number when the injection Mach number was relatively low， which the maximum increase was 80.6%.