Effects of blade exit angle and liquid viscosity on unsteady flow in centrifugal pumps

Abstract

Unsteady flows in centrifugal pumps have been extensively studied by means of computational fluid dynamics (CFD) till now. However, effects of viscosity of fluid pumped and blade exit angle on flow steadiness were omitted. Thus, the unsteady flow in an experimental centrifugal pump with two different blade exit angles was explored when the pump handles the liquids with different viscosities by CFD code Fluent to quantitatively clarify the effects in this article. The heads estimated using the unsteady flow model were compared with experiments at two viscosities. The effects of mesh density and turbulence model on the fluid velocity and pressure profiles behind the impeller were clarified. The velocity profiles at the two impellers discharge were validated with the results of laser Doppler velocimetry measurements for water. It was shown that an increasing viscosity of fluid reduces the fluctuation in flow variables at the inlet and outlet to impeller, a larger blade exit angle results in a more remarked fluctuation in the variables.