Numerical Prediction of NPSHR Characteristics of Double Suction Centrifugal Pump

Abstract

The pressure at inlet of pump is mostly below atmosphere pressure and may come below the vapour pressure of water depending on installation and operating condition. This situation may lead to cavitation in pump and it is one of the leading causes for reduced reliability on performance of centrifugal pumps. NPSH (net positive suction head) is used to check the cavitation condition in centrifugal pumps and it is the absolute total pressure energy available above vapour pressure. The NPSHR is the net positive suction head required at pump inlet for working of pump without cavitation and special test rig is required to predict the values of NPSHR of pump experimentally. CFD has minimized the experimental work for prediction of cavitation characteristics of hydraulic machines where selection of turbulence model plays important role on the accuracy of simulation results. In this paper, an effort has been made to predict NPSHR characteristics of double suction centrifugal pump at three different operating points using Computational Fluid Dynamics (CFD) approach with two turbulence models. The results from CFD using κ-ε and SST turbulence models have been compared with experimental results at pump design condition and found to be in close comparison. The losses in different pump components are also computed to study pattern of hydraulic loss with the growth of cavitation.