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This paper focuses on the single stage and multistage performance characteristics of centrifugal mixed flow submersible borewell pump. This study reveals that the performance of single stage pump is higher than that of multistage pumps. The head, input power and efficiency of single stage pump are higher than the per stage head, per stage input power and efficiency of multistage pumps. This study is divided into three parts. In the first part, five prototype pumps were made in single stage and multistage construction and the performance tests were conducted. In the second part, numerical validation has been done for different turbulence models and grid sizes. k-Omega SST model has been selected for the performance simulation and was validated with the performance of the test pump with static pressure tappings .In the third part, single and three stage pump performance were simulated numerically and compared with experimental results. The detailed analysis of pressure and velocity distributions reveals the difference in performance of single and three stage pump, due to non-uniform flow and difference in averaged flow velocities at the subsequent impeller inlets except the 1st stage impeller inlet. keywords: Submersible bore well pump, Multistage, Single stage, k-Omega SST, Per stage input power , Efficiency, Averaged flow velocity, Non uniform flow, Recirculation. 1.Introduction At present, in the pump industry it is assumed that the efficiency of single stage and lower stage pumps is lower compared to that of higher stage pumps. Manufacturers of multistage submersible pumps all over the world give performance catalogue [1] which contains family curves of series of different discharge rates with a foot note to reduce the efficiency points for 2 stage and single stage pumps from the given average efficiency curve. Also various national pump standards [2] specifies the same practice of reducing the efficiency values for lower stages. This study focuses on the single stage and multistage performance characteristics of centrifugal mixed flow submersible borewell pumps. The multistage centrifugal mixed flow pumps are used in the borewell pumping of water .The pumps are submersible type and coupled directly with the wet winding submersible induction motors. The number of pumps used for this purpose is increasing in the last two decades all over the world and in India. More and more borewells are drilled for tapping the ground water sources. The sizes of borewells range from diameters 100mm, 150mm, 200mm, 250mm and upto350mm.The majority of the borewells is in 100mm and 150mm sizes. The present study is of the pumps used in the 150mm diameter bore wells. The submersible pump of mixed flow type is shown in Fig.1.The inlet bracket(1)is used to guide the water flow into the first stage mixed flow impeller(2).The rotating blade system in the impeller imparts energy to the water and the high velocity water comes out in a conical spiral pattern. The diffuser (3) blade passages collect the water and diffuse its velocity. Also they direct the water to the next stage impeller. The velocity of the water at the second stage is kept same as that of the first stage, but the pressure energy is higher which is gained at the first impeller. The same process repeats in all the subsequent stages and the energy is added in all the stages by the work done at the impeller passages. The discharge casing (4) is at the end of the stages. It collects the high energy water and directs it to the column pipe (5) which is transferring the water to the ground level. Also column pipe is supporting the entire pumpset i.e. pump coupled with the motor and the axial down thrust caused by the pump impellers during running. In the last decade, various studies were conducted on the impeller and volute interaction of centrifugal pumps and the results were published. The numerical simulation of the dynamic effects due to impeller-volute interaction in a centrifugal pump was given by Jose Gonzalez, et al. [3] which explains the capability of numerical simulation in capturing the dynamic and unsteady effects inside the centrifugal pump. The head and flow distribution within the volute of a centrifugal pump in comparison with the characteristics of the impeller without casing and unsteady behavior of velocity at impeller exit was given by P.Hergt et al..[4]. Also Akhras.A et al.[5] discussed the flow rate influence on the interaction of a radial pump impeller and the diffuser. Jianjun Received March 16 2015; accepted for publication December 2

Numerical And Experimental Study Of Single stage And Multistage Centrifugal Mixed Flow Submersible Borewell Pumps