| Summary: | 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.
|
|---|
