Study on Secondary Flow of Turbine Cascade

• Main Authors: Shiang-Shiu Liao, 廖祥旭
• Other Authors: Jiun-Jih Miau
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/81658457189226358565

碩士 === 國立成功大學 === 航空太空工程學系 === 83 === The purpose of this work is to investigate the secondary flow phenomenon while flow passes through a two-dimensional turbine cascade. The experiments were conducted in a low- speed wind tunnel. The cascade was designed with the capability of varying the incidence angle and the stagger angle. A blower was employed to suck out a portion of the inlet boundary layer fluid, for the purpose to improve the two-dimensionality of the flow. In the present study, the Reynolds number based on blade chord was approximately 50,000, and the incidence angle could be set at -20 ° and 0 °, respectively. Measurement of the secondary flow structures and the total pressure losses on 4 specified downstream planes were made. Besides, a oil flow visualization techni-que was employed to survey the interaction of the flows from the blade suction surface and the endwall corner, which revealed the signature of the passage vortices and the endwall limiti ng streamline patterns. The results show organized secondary flow structures at the incidence angle -20 °, accompanied with higher pressure losses near the endwalls. Different inlet boundary layers seemed to have only minor influences on the size and location of the secondary vortices. In the region downstream of the turbine blade, vertical component of the kinetic energy dissipated much faster than that of the horizontal component. When boundary-layer suction was applied, the pressure loss was increased, but the two-dimensionality of the flow was improved. At the incidence angle 0 °, the secondary flow structures were comparatively small. The separated flow originated from the blade suction surfaces dominated the total pressure loss. Also noticed is that the pressure loss along the spanwise direction were quite uniform.