Investigations of specific modifications in pump as turbine towards performance improvement

Centrifugal pumps as turbines offer a proven green energy solution for sustainable development, potentially replacing costly custom turbines in micro-hydro power plants and providing cost savings. But the efficiency of the pump as a turbine is lower than that of the dedicatedly designed pump. In this study, new simple modifications are proposed and evaluated on a developed state-of-the-art PAT test rig with impeller of specific speed 43.7 (m-m3/s). Being simple modifications, cost benefits will remain intact without requiring specially designed turbines and trained manpower. New simple modifications in PAT, like balance holes filling, packing seal optimization with appropriate size, leading edge of impeller blade tips modification making it single curve, and inner shroud widening for increasing the width at the inlet of the impeller, were proposed and performed to investigate the influence of the modifications on PAT performance. The experimental study finds that optimal packing seal size and impeller leading edge modifications notably boost PAT efficiency by 3–3.5%, making it worthwhile to implement for resource conservation and performance enhancement. On the other side, inner shroud widening noticed a 1.2% reduction in efficiency, adversely affecting the performance of PAT. Additionally, balance hole filling is neutral and does not have any effect.