Numerical Analysis of Flow Phenomena in a Centrifugal Pump of Low Specific Speed

Abstract

The computational fluid dynamics (CFD) analysis of a low specific speed centrifugal pump has been done. This work aims to improve the hydraulic performance of centrifugal pump defined as efficiency and cavitation. The shear stress transport (SST) k-ω turbulence model which is RANS based model is employed for 3-D steady state analysis using Ansys CFX. In the first part, the performance of impeller is moderately improved with the parametric analysis of two design parameters: blade wrap angle and outlet blade angle. The large wrap angle of the impeller blades reduces the shaft power consumption and large outlet angle increases the head of pump marginally. In the second part, the two different volutes with radial and tangential diffusers are analyzed. The volute with tangential diffuser shifted the design condition towards higher flow rate with the efficiency rise of 8.5% as compared to the baseline volute with radial diffuser. In the third part, Rayleigh-Plesset model is used to investigate the two-phase cavitating flow. The inletblade angle is chosen as a design parameter to improve the cavitation performance of the pump. The blade inlet angle affects the suction capability of the pump and therefore affects the cavitating condition of the pump. The inlet angle of 18˚ enhanced the cavitation performance giving NPSH of 1.12 m decline as compared to the baseline pump.