端壁相对运动对超声速膨胀器间隙流动的影响

Influence of relative motion of the end wall on tip clearance flow in a supersonic expander

为了揭示端壁相对运动对超声速膨胀器间隙流动影响的规律,采用数值方法研究了机匣与隔板不同相对运动速度时超声速膨胀器间隙流动特性。结果表明:泄漏流与主流和附面层的掺混损失是超声速膨胀器间隙区域流动损失的主要来源,吸力面靠近分离线右侧区域的流动损失最大,压力面附近除尾缘外流动损失均较低;机匣与隔板相对静止降低了黏性剪切力的作用,但端壁的壁面效应对间隙流动却存在影响;端壁相对运动抑制了泄漏涡的横向发展,分离线向吸力面靠近,泄漏流量增加,泄漏流、主流和端壁附面层的掺混严重,附面层内低能流体的迁移、潜流和摩擦也加剧,三维流道内总的流动损失增加,超声速膨胀器效率降低。

To reveal the effect of the relative motion of the end wall on the tip clearance flow of a supersonic expander, the three-dimensional Reynolds-averaged Navier-Stokes equations and the k-ε turbulent model were used to nu- merically simulate the tip-clearance flow. Relative motion between the strake wall and casing was considered at different speeds. The simulation results show that the loss due to mixing of the leakage flow, mainstream flow, and boundary layer is the main source of loss in the clearance zone of a supersonic expander. The flow loss at the suction-surface zone near the separation line is maximum, but the flow loss near the pressure surface is lower beside the trailing edge. It would be expected that the viscous shear force be weakened due to relative stagnation between the strake wall and the casing, but the effect of the end wall has a significant impact on the clearance flow. When relative motion of the end wall exists, transverse motion of the leakage vortex is inhibited, the separation line approaches the suction surface, and the tip-leakage flow increases. The mixing process of the leakage flow, mainstream flow, and end-wall boundary layer is significant. The migration, subsurface flow, and friction of the low-energy fluid within the boundary layer are also intense. The efficiency of the supersonic expander decreases due to an increase in the total loss in the three-dimensional flow passage.