Performance of a submerged impulse hydro turbine

This study is focused on performance of a developed submerged impulse turbine, which is suitable for small hydropower generation in drinking water pipelines around mountainous region. The turbine works as a pressure reducing valve and can be generated electricity. Loss for submerged operation of the runner should be clarified to estimate accurately the turbine performance. The performance tests were conducted with changing the casing pressure, supplying flow rate and number of nozzles. As a result, turbine performance for submerged operation drops down comparing that for non-submerged operation. The water jet issuing from the nozzle occurrs cavitation. The cavitation degradates turbine performance. The cavitation phenomenon can be suppressed by increase the casing pressure. It is also revealed that the number of nozzles is important for the turbine performance. This is because of that the input energy from the nozzle is increased with the number of nozzles, on the other hand disc friction and mixing loss on the runner is only depended on the runner rotation speed.