Investigation for Loss Generation Mechanisms of Flow in Turbomachinery by Using Curved Square Duct (2nd Report, Influence of Cross-Sectional Aspect Ratio)

Abstract

In the secondary flow within a passage of a turbomachinery, the passage vortex generates a major part of the losses. In a series of studies, the passage vortex is closely analyzed by the numerical computations using curved ducts as fundamental models for the generation of the passage vortex. The flows in the curved ducts are examined by relating the bend of curved duct to the blade-to-blade surface of an axial flow turbine cascade and to the meridional plane of a centrifugal impeller. The cross-sections of passage of a turbomachinery have various aspect ratios. In this study, the cross-sectional aspect ratio is chosen as the major parameter affecting the loss generation cuased by the passage vortex. The computed results clarified that the decrease of the aspect ratio strengthened the passage vortex and consequently, increased the loss caused by the passage vortex.