Experimental Investigations of the Three-DimensionalFlow in a Large Deflection Turbine Cascade with Tip Clearance

作     者：M.Govardhan S.S.S.R.K.Sastri V.S.Vishnubhotla 

作者机构：ThermalurbomachinesLabDepartmentofMechanicalEngineeringIndianInstituteofTechnologyMadrasChennai600036IndiaThermalurbomachinesLabDepartmentofMechanicalEngineeringIndianInstituteofTechnologyMadrasChennai600036IndiaThermalurbomachinesLabDepartment 

出 版 物：《Journal of Thermal Science》 (热科学学报（英文版）)

年 卷 期：1998年第7卷第3期

页      面：149-164页

核心收录：

学科分类：080703[工学-动力机械及工程] 080704[工学-流体机械及工程] 08[工学] 0807[工学-动力工程及工程热物理] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

主　　题：turbine cascade tip clearance vortex tip separation vortex horse-shoe vor-tex total pressure loss coefficient discharge coefficient 

摘      要：Results obtained from an experbontal study of the threedimensional flow survey within and exit of a large defiection linear turbine cascade are presented for a tip clearance levels of 0.08, 1.5, 3.0 percent of chord and compared with the help of boundary layer probes and that within and exit of a blade passage was done with a miniaturised five hole probe. End wall and blade tip surface static pressures were also obtained, in addition to flow visualisation studies. A strong horse-shoe vortex forms in front of the leading edge for zero clearance whereas this vortex does not appear for 3 percent clearance indicating that for large clearance the pressure forces have dominating infiuence than the viscous forces. In addition to normally known clearance vortex, a small tip separation vortex was noticed on the blade tip surface inside the tip gap. Due to the area contraction caused by the tip separation vortex, the fluid movign towards the tip gap from the pressure side is accelerated. Downstream of the vortex, the endwall pressure increases due to flow mixing. Both vortices increase in size and strength along the chord. The miring is incomplete in the aft portion of the blade. The tip gap velocity profiles exhibit wak like characteristics especially at axial positions where the mixing is incomplete. The passage vortex in the present investigations did not diminish with increase in clearance. The discharge coefhcient and the total pressure loss coefficient within the tip gap show similar tendency with lower values near the leading and trailing edge regions.