Performance Analysis and Cavitation Prediction of Centrifugal Pump Using Various Working Fluids

Abstract

Background: The application of centrifugal pumps is found in domestic and petrochemical industries. Industrial centrifugal pumps are designed and tested using water as working fluid before supplied to industries, as water is commonly available. However, centrifugal pumps are used in industries for various applications, which involve the handling of fluids other than water- like saline-water, crude oil, gasoline, etc. Consequently, hydraulic performance of the pump differs from the designed and tested values and pump performance becomes unpredictable. Cavitation characteristics of the pump handling different fluids other than water are also changed and many a time, cavitation starts prematurely. As a result, the operating cost of pump is increased. Objective: A CFD based computational analysis of a single-stage, single-entry industrial centrifugal pump having double-volute casing is carried out to compare the performance and cavitation characteristics for various working fluids, namely water, saline water with varying salinity, gasolene and crude oil. Methods: Multiple Reference Frame method (MRF) available in Reynolds-Averaged Navier-Stokes (RANS) equations based CFD solver Ansys-CFX is used in the present study. CFD simulation is carried out for five flow rates with Standard k-ε turbulence model. Rayleigh-Plesset equation describing the growth of a single vapor bubble in a liquid is used for predicting the cavitation flow behaviour. Results: Minimum static pressure is computed at the suction side of saline water as compared to the other working fluids studied here. Hydraulic efficiency of crude oil is found to be the lowest as compared to other fluids. Supercavitation (excessive formation of vapor bubbles and sudden drop in head up to 3%) starts early for saline water with 40g/kg salinity. Conclusion: The results show little variation in pump efficiency when water and saline water are used as working fluids. However, cavitation characteristics differ considerably with the working fluids. Recent patents filed/published in this area revealed that efforts are needed to develop effective cavitationresistant centrifugal impellers and pumps.