MODIFICATION IN CENTRIFUGAL PUMP USED AS TURBINE

Abstract

The major problem associated with micro hydropower schemes is the non-availability of standardized equipments like turbines because micro hydropower sites are having different head and discharge. Since there is non-availability of standardized equipments, therefore particular type and dimension turbines need to be ordered for particular sites. This may not be economically viable. An option for such sites is to use a standard pump used in reverse mode (PAT) instead of a conventional turbine. The use of standard pumps as turbines (PAT) may often be an alternative with a considerable economic advantage and might therefore contribute to a broader application of micro-hydropower. Technically there is no problem to use a pump as turbine in reverse mode, but the problem is its selection. The performance characteristics of pump as turbine will be different than pump as pump. Another problem with pump as turbine is that, pump has fixed flow control mechanism, which restricts its application at those sites, where there is variation in flow. Many investigators suggested the ways and means for selection of pump as turbine, however no work has been reported for the modification of pumps to facilitate the variable flow control mechanism. In this dissertation an attempt has been made to modify a commercially available centrifugal pump by providing movable guide vanes. In order to compare the efficiency of modified pump, a centrifugal pump was tested for its efficiency in turbine mode. After designing suitable guide vanes and their regulating mechanism, six movable guide vanes have been provided around the pump impeller and it has again been tested for its efficiency after such modification. After conducting the experiments and analyzing the results it has been found that after its modification, its efficiency has been found to be increased by 4%. Further, it has been found that the operating range of the modified pump as turbine is also increased substantially.