Experimental Studies on Part Load Performance of Pump Running in Turbine Mode

Abstract

Pump can be used as turbine in place of conventional turbine because of having many advantages e.g. easily available, low installation and maintenance cost, available for large range of head and discharge etc. The efficiency of pump as turbine (PAT) is usually lower than the conventional turbine, but it can be compensated by the low initial cost. One of the reasons for lower efficiency at part load of PAT is absence of flow control mechanism which is present in conventional turbines. The part load efficiency of PAT can be increased by providing low cost modification like by providing the movable guide vanes for flow control. In the present study, introduction of micro hydropower and PAT is given. The literature review related to PAT is presented. Experimental investigation were carried out on pump (Head 15 m, Discharge 1500 LPM) running in turbine mode with two different impellers (viz.  250 mm and  225 mm) at seven different rotational speeds. It was found that the efficiency remain nearly same due to decrease in impeller diameter. However, the performance was improved with decrease in rotational speed below the rated speed of 1400 rpm. Flow controlling mechanism was designed, developed and installed. The experiments were performed with 7, 5 and 4 number of guide vanes at different angles in the speed range of 1000-1400 rpm. The performance of PAT was found higher with 4 guide vanes at all the speeds. The maximum efficiency was obtained as 70.87% with 4 guide vanes at an angle of 13o at 1200 rpm.