Performance analysis and improvent of submersible pumps

Abstract

The prediction of performance and efficiency of turbomachines based on test results with geometrically similar physical models using scale effect formulae has been done for the past several decades. Now, with the introduction of large, fast micro and macro computers and advancements in computational techniques in turbomachinery flows, analytical modelling has become feasible. Experience gained through various numerical and empirical works has brought more insight into key turbomachinery flow problems and has also made possible the modelling of complicated three dimensional flows that occur in machines. Such newly developed computational methods predict well the true performance of centrifugal hydraulic machines with reasonable accuracy. However, the capability of predictive techniques reported so far is not good enough in the extreme operating range of centrifugal pumps and in predicting the performance of very low–specific speed pumps. The present investigation reports such a performance prediction procedure applicable for low–specific speed pumps with good selection of empirical quantities and improved loss correlations. The results of this investigation show good agreement between the calculated and actual test performance over the whole operating range of low–specific speed submersible pumps. Though there exists a small discrepancy at low flow rates, the accuracy of prediction of overall performance is comparatively better. A complete understanding of the distribution of losses in the components of the pumps, in the present analysis, provides means for improving the performance and identifying the problem areas in existing pump designs. The work also provides a basis for selection of parameters for optimal design of pumps in which maximum efficiency is an important design parameter. The scope for improvement in the prediction procedure, particularly with respect to the nature of flow phenomena in the low flow region, has been discussed in detail. Recommendations have been made in the design techniques of low–specific speed pumps for better performance.