Positive displacement turbine - A novel solution to the pressure differential control valve failure problem and energy utilization

Micro hydro turbines are getting renewed research interest in recovering unused energy from systems like water supply pipelines, sewage treatment and transportation plants, chemical and oil refineries, etc. and making them energy efficient for sustainable development. The present work dealt with this aspect wherein the unused energy of the hot water transportation pipelines, which was earlier throttled by pressure differential control valve (PDCV), was harvested and used elsewhere. A special class of multi-purpose micro hydro turbine known as the positive displacement turbine was developed for the present application which involved very low flow rates with high heads and very low specific speeds and to replace the PDCV which was frequently failing due to cavitation causing loss of energy. A framework was developed for designing such turbines and predicting their performance using CFD. The reasons for the occurrence of cavitation and flow pulsations were also examined and remedial measures were incorporated for their elimination. At the rated condition during experimental study, the base design generated 7.31 kW power with an overall efficiency of 67.7%. The socio-economic analysis was also carried out which concluded that the PDT will aid in energy conservation and reduction in CO2 emissions.