激波对气膜干扰作用的抑制机理研究

Controlling Mechanism of Interaction Between Shock Wave and Cooling Film

关键词:  激波  气膜  分离  逆压梯度  边界层吸除  冷却效率

Key words:  Shock wave  Cooling film  Separation  Adverse pressure gradient  Boundary layer suction  Cooling effectiveness

摘要:

为了研究激波对气膜冷却效果的破坏机理，并消除这种影响，以平板壁面为基础设计了一种带有卸压槽的壁面结构。通过数值计算研究了主流马赫数为3.2，冷流马赫数分别为1.0、0.6和0.4三种工况下开槽壁面对激波破坏的抑制作用。结果表明，在有激波入射的条件下，开槽壁面比平板壁面具有更好的流场结构，可使激波导致的近壁气膜的分离区最多减小至原来的三分之一，并有效减弱气膜入射后在肩部产生的反向涡旋对，这很好地抑制了气膜的卷吸和与主流的掺混。计算显示开槽壁面最大能够使壁面冷却效率提高6%，且这种作用效果与通过卸压槽的气流流量大小有关。此外仿真结果表明，在相同条件下波前卸压较波后卸压效果更好。通过合理安排卸压槽位置及槽面宽度，可以将总压损失控制在合理范围内。

Abstract:

In order to study the mechanism of interaction between shock wave and cooling film and how to eliminate these influences，wall with special slots based on the flat plane model is designed. Through numerical simulation the mechanism of how the wall with slots controlling the influences of shock wave is investigated in three different conditions. The Mach number of mainstream is 3.2 and those of coolants are 1.0，0.6 and 0.4 respectively. The results of numerical simulation indicate that the wall with slots has better flow structure under the conditions of shock wave，and can reduce the size of film separation zone to a third compared with flat plane wall，and the reversed vortex pairs which are generated when film injects into mainstream are weaken to a certain extend. These changes can effectively restrict the entrainment and mixture of film. The data suggest that the film-cooling effectiveness can be improved by 6% at most when the wall is slotted and this effect is greatly related to the mass flow rate of flow through the pressure-relief slot. In addition，the results show that the model which releases the high pressure upstream has better performance than which releases the high pressure downstream under the same condition. The total pressure recovery coefficient can be maintained at a high range through reasonable arrangement of the positions and widths of slots.