Performance evaluation of high discharge low head pumps

Abstract

Paddy cultivation in Kuttanad and Kole lands is made possible only after large scale dewatering operations. These water logged lands have to be drained in the shortest possible time to initiate seed bed preparation. The short time available for seed bed preparation need adoption of high discharge low head pumps. The most commonly used centrifugal pump is incapable of giving corresponding increase in discharge rate even if the lift required is reduced to a minimum. So this study was undertaken to help to identify a suitable portable pump for meeting the specific requirement of drainage in Kerala. Mixed flow and axial flow pumps imported from Thailand were used for this purpose. The study included testing of lS-cm mixed and axial flow pump at the specially designed and constructed test bed at different speeds and at different water levels in the pumping sump. For each test, from the data obtained discharge, input power and efficiency were calculated. Using the calculated values performance characteristic curves were plotted and regression equations were developed for discharge efficiency, discharge - total head and discharge - input power relationship at each speed. Performance curves were also plotted keeping total static head const ant and regression

equations of speed - discharge, speed - total head, speed - input power and speed efficiency relationships were developed. The maximum efficiency of IS-cm mixed flow pump was 42.16 per cent at a speed of 1000 rev/min, against a total head of 217.33 cm and a discharge rate of 49.47 L/s. The input power corresponding to this efficiency was 3.4 hp. The best performance of mixed flow pump was noted at a working speed of 1000 rev/min. The maximum efficiency of IS-cm axial flow pump tested was only 18.05 per cent at a total head of 160.55 cm and a discharge of 24.88 L/s. The corresponding speed was 2500 rev/min and input power was 2.95 hp. The best performance of axial flow pump was noted at a working speed of 2500 rev/min.