关键词: 涡轮;叶尖;流动模式;流动机理;泄漏涡;通道涡

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