Abstract
In centrifugal turbomachines, guide vanes, namely circular cascades, are installed to change the circulation of the radially outward and/or inward flow in the fixed channel. There are many studies on guide vanes for the outward flow, such as diffusers. On the contrary, studies on guide vanes for the inward flow are limited, so it is desirable to study this aspect further. From such a viewpoint, this review presents the recent progress of research in Japan on circular cascades for the inward flow. Circular cascades include wicket gates of water turbines, return vanes of multistage centrifugal turbomachines and diffuser vanes of mixed-flow pumps. The cascades installed in the machines for high head or high pressure are composed of thick vanes with a small aspect ratio. The most important problem in these cases is a flow separation on the vane surface, this separation complicates Kutta's condition for the cascade theory. Moreover, a secondary flow also considerably affects the through-flow. These are all considered as main problems in this review.
