动叶顶部蜂窝面迷宫密封对涡轮级气动性能的影响

采用计算流体动力学软件数值研究了某1.5级轴流涡轮转子叶尖蜂窝面迷宫密封泄漏流动对主流流场的影响,分析了不同的顶部间隙下叶尖密封泄漏流对主流流场的影响以及泄漏流与主流的掺混对下游静叶流场的影响,并对带与不带蜂窝面的迷宫密封对涡轮级气动性能的影响进行了比较.研究结果表明:泄漏流与主流在动叶下游掺混后导致掺混区域流体速度发生偏转,以负攻角进入下游静叶,带来攻角损失.泄漏流体带有较高的径向速度,在静叶栅通道中会向中间叶展处发展,使得静叶栅上半通道的流场结构发生改变,带来额外的二次流损失.并且随着叶顶间隙的增大,损失也随之增大.蜂窝的特殊六边形结构极大地降低了密封腔中流体的周向速度,减小了泄漏流重新进入主流时与主流的速度差异,从而减小了掺混损失.并且蜂窝结构能改变迷宫腔内气体的流动形态,采用蜂窝面的迷宫密封能有效地降低泄漏. 

Effect of labyrinth-honeycomb seal of shrouded rotor blades on the aerodynamic performance of the turbine stage

A commercial CFD(computational fluid dynamics) software was used to research the effect of rotor labyrinth-honeycomb seal leakage on the main flow in a 1.5-stage axial turbine.Effects of rotor seal leakages on the main flow,and mixing between leakage and main flows on the downstream stator with different tip clearances were analyzed;in addition,the effect of labyrinth seal with and without honeycomb facings on the aerodynamic performance of turbine stages was compared.The simulation results show that,mixing between leakage and main flows leads to velocity deflection in the mixing zone,and the suction side incidence of the re-entering leakage flow in the subsequent stator causes additional losses.The re-entering leakage flow in the subsequent stator which has a high radial velocity,alters the flow structure of the upper half channel,and causes extra secondary losses,besides,the losses are increasing with a growing tip clearance.The honeycomb acts to kill swirl velocity development for the rotating labyrinth-honeycomb seal due to the specific hexagon structure,which weakens the flow over the circumferential direction.Thus,it decreases the velocity gradients produced by the different velocity components of main and leakage flows,and the mixing of the leakage jet and main flow is greatly decreased.The honeycomb changes the flow pattern of labyrinth-honeycomb seal which leads to a reduction in leakage compared to the labyrinth seal.