Numerical investigation of transient vortices and turbulent flow behaviour in centrifugal pump operating in reverse mode as turbine

Abstract

Operation of pump in reverse mode as turbines (PAT) can be useful in producing inexpensive energy for rural settlements in developing counties. Nonetheless, the optimal connection between the Pump geometry and flow cannot be held in reserve when operating in the PAT mode as a result, high flow instabilities are likely to occur. The pump under investigation is made up of four blades with four splitters and operates at nominal head and flow rate of 12 m and 12.5 m3/h respectively with a rotational speed of n = 29,000 rpm. This study investigates the transient flow characteristics of PAT to analyse the flow instabilities present during PAT operation at different rotational speeds (n = 1500 rpm ∼ 2000 rpm). Velocity and pressure distributions inside the impeller are discussed. An experiment has been perform to authenticate the CFD results. After analysing the results, it was observed that there is an increase in absolute velocity of the fluid. The numerical results obtained will help to understand the PAT performance when compared with pump mode experimental results. The study concludes that numerical simulation provides reliable and conceivable methods for predicting the transient flow and time mean characteristics of PAT. Keywords: Pump as turbine, Flow structure, Vortex in impeller chamber, Centrifugal pumps