PERFORMANCE ANALYSIS OF MODIFIED PUMP AS TURBINE

Abstract

In the present scenario of growing, luxurious and developing world the energy demand is continuously increasing and on the other hand the conventional resources of energy generation (coal, oil, natural gas) or fossile fuels are continuously depleting .Due to the use of fossile fuel the environmental pollution problem occurs and the trend changes towards the renewable energy generation. The hydro power generation is one of the economical and environmental friendly renewable energy systems. But large hydro schemes are always not considered economically, socially and politically feasible. Hence the small, mini, and micro hydropower schemes came into existence. The major problem associated with micro hydropower schemes is the non-availability of standard equipments like turbines because micro hydropower sites are having different head and discharge. Different type and size of turbines are required for different sites. This may not be economically feasible for any standard turbine manufacturer. Use of centrifugal pump in reverse mode as pump as turbine (PAT) could be an economically viable solution for micro hydro. Technically there is no problem to use a pump as turbine in reverse mode because it is similar as Francis turbine having fixed flow regulation system. However the performance of pump as turbine will be different than pump as pump and main constraint is its single point operation. The part load efficiency is very poor because of the absence of the flow control mechanism, hence it is a major constraint to use pump as turbine at those sites, where the variation in flow occurs. Many investigators suggested many methods for the selection of pump as turbine; however no work has been reported for the modification of pumps to improve its operation for flow variation. Under the present study an attempt has been made to predict the performance characteristics of a centrifugal pump on the basis of theoretical analysis of functioning in both modes of operation for the same machine. The performance characteristics of a centrifugal pump used in turbine mode has. been determined based on the actual testing of pump before providing any modifications. There are certain losses appear when a pump running in reverse mode, which reduces the efficiency. To improve the efficiency in turbine mode need to reduce the certain losses, which directly affect the performance of iii machine. For the reduction of shock loss at inlet in turbine mode a modification has been provided in runner vane shape. In order to improve the part load efficiency of pump as turbine concept of providing movable guide vanes with the commercially available pump has been suggested. Attempt has been made to design the movable guide vanes and fitted the same with pump. Experiments have been conducted to find out the correct position of guide vanes. The efficiency of modified pump has been compared with the pump as turbine without modification. Based on the experimental study, part load efficiency of the pump as turbine is found to be improved substantially. ry