Numerical simulation of flow through vaneless diffuser

Abstract

Flow through vaneless diffuser in the centrifugal compressor stage is studied at varied flow conditions using finite volume method based commercial code, ANSYS CFX. The contour of static pressure, stagnation pressure, absolute velocity, as well as meridional velocity divulges the nature of flow that happens in the centrifugal compressor stage. Circumferential non-uniformity due “jet-wake” formation is seen at the impeller exit. These lead to mixing of fluid having varied energy levels which happens within the vaneless diffuser. Total pressure rises along the radius ratio and its distribution is higher near the shroud for all flow conditions. Absolute velocity reduces along radius ratio as area of the flow passage increase indicating diffusion. The meridional velocity is seen as non-uniform at Ф = 0.15 but, it is uniform at diffuser exit at Ф = 0.25.