Analysis and Improvement of Mixed Flow Submersible Pump using CFD

Abstract

Submersible pump is a device mainly used for oil and water extraction. The roll of CFD technique becomes vital in the design of submersible pump due to the increased requirement of high efficiency submersible pumps. In the present study, vertical turbine type three-stage mixed flow submersible pump (discharge: 30 lps and head: 8 m per stage) manufactured by M/s Duke Plasto Technique Pvt. Ltd., Palanpur is analyzed using the CFD software ANSYS-CFX. The analysis is carried out on two main components i.e. impeller and bowl of only first stage as all three stages are identical. The computational models of impeller and bowl were prepared using ANSYS DesignModeler. The impeller is analyzed using rotating frame of reference with rotation speed of 2880 rpm, while the bowl is analyzed in stationary frame of reference and the interface is taken as frozen rotor. To consider turbulence effects, k-ε turbulence model is used with turbulence intensity of 5%. The first order upwind scheme is used for discretization. As boundary conditions, mass flow rate is specified at impeller inlet while relative (gauge) pressure is defined at bowl outlet. At design condition, the pump efficiency was found as 73.54% and 57.71% respectively with CFD and experimentally respectively. The efficiency predicted by CFD is higher than the experimental one. This may be due to negligence of mechanical losses, volumetric losses and surface friction as well as modelling errors. To improve the efficiency, impeller is modified by reducing number of blades from 8 to 7. The efficiency and head of modified impeller were increased by 0.95% and 2.65% respectively and power input to pump is decreased by 3.5%. To further improve the performance of pump, new design of impeller was done from the first principle.