Abstract: Detail numerical investigation have been carried out for two typical turbine blade tip structures of flat and cavity-squealer, and the difference of the tip leakage flow mode for both type of tip geometries has been compared. The aim is to gain the interaction flow mechanism between the leakage flow and the vortexes of the endwall. Then three main factors of tip leakage flow are identified. There are the sources of the leakage fluid ,driving force and loss. The tip leakage flow mode was put forward. The results showed that both the high pressure fluid beside the pressure side of the blade and the boundary layer flow of the shroud wall were the sources of the leakage fluid. The transverse pressure gradient between the suction side and the pressure side of the blade and the relative motion of the tip and shroud wall were the main source of the driving force of the leakage flow. The leakage vortex formed by the high speed shear flow of the leakage and the main stream, the interaction between the leakage and the passage vortex were the main source of loss. The “low pressure trap” of the passage vortex was the main cause why the leakage flow can reinforce the passage vortex.

Key words: Turbine;Tip;Flow mode;Flow mechanism;Leakage vortex;Passage vortex

摘要： 采用数值模拟方法研究了涡轮叶片平叶尖和凹腔叶尖两种典型叶尖结构泄漏流动的差异，目的是获取叶尖泄漏流与端壁涡系的相互作用机理认识。识别了涡轮叶尖泄漏流动的三个主要因素：流体源、动力源和损失源，提出叶尖流动模式。结果表明：叶尖泄漏流动的流体源包括压力面侧高压流体、上端壁附面层流体；驱动泄漏流动的动力源为吸力面和压力面之间的横向压力梯度、叶尖与上端壁的相对运动；主要损失源为泄漏流体与主流流体高速剪切形成的泄漏涡、泄漏流体与上端壁通道涡相互作用；通道涡的“低压陷阱”是泄漏流参与通道涡发展的主要原因。

关键词: 涡轮;叶尖;流动模式;流动机理;泄漏涡;通道涡