PERFORMANCE EVALUATION OF PUMP AS TURBINE

Abstract

The research on pump as turbine (PAT) at this critical phase of developing decentralized small hydro systems is appropriate for many reasons. The conventional turbine technologies like Pelton and Cross flow turbines that have been implemented in the micro hydro sector have to be custom-made and are therefore more expensive. They also need expert design and precise manufacturing skills for a good performance. This often becomes a bottleneck especially for smaller projects below 20 .kW of installed capacity. An alternative approach of using well-known `pump as turbine' concept can be contemplated and popularized. Pumps are readily available all over the world in every shape and size, mainly due to the ever-increasing demand for pumping application. Also the maintenance and operational issues in pumps are relatively much simpler. Technically there is no problem to use Pump as Turbine, but the problem is its selection. Best Efficiency Point of PAT is different compare to that of Pump as Pump. Similar to Pump PAT also runs at a single operating point for its best efficiency. So it is very essential to know the performance of Pump in reverse mode. Basic available approaches to predict the performance and selection of Pump as Turbine are experimental analysis and CFD analysis. CFD analysis may be more useful to predict the performance of a pump used in turbine mode. Under the present work of the dissertation an attempt has been made to predict the performance of commercially available Centrifugal Pump in reverse mode using CFD techniques. FLUENT software has been used for the CFD analysis of flow field inside the Different component of Pump to predict the Best Efficiency Point (BEP) of pump in turbine mode. Flow field inside the volute casing, Impeller and draft tube has been analyzed at BEP and other values of discharge. Correction factors for head and discharge have also been determined based on the results obtained by CFD techniques. These correction factors are compared with the available relation of other studies and found in good agreements.