Comparative assessment of novel hooped and conventional Pelton wheel turbine runner using downcomer nozzles of different materials and exit diameter through experimental investigations

Impulse turbines are significant because of their straightforward design and the lack of specialized expertise to create the runners.The hooped Pelton turbine runner with a 256 mm pitch circle diameter and a 40 mm hoop gap with a 4 mm hoop thickness was developed to reduce the bucket stress caused by water jets.The current paper investigates developed hooped and identical conventional Pelton turbine runners with a single downcomer nozzle of different sizes and materials to predict and compare performance parameters at variable flow conditions with uncertainty in measurements.In the present experimentation, two stainless steel nozzles of 17 mm and 23 mm and four polymeric material nozzles of 17mm, 18 mm,19 mm, and 23 mm were used for both runners.The nozzles have a range of convergence angles (24-32 degrees) and beta ratio (0.38 -0.49).The jet and velocity ratios of 11 to 15 and 0.362 to 0.492 were studied, respectively.The 17 mm stainless steel nozzle with conventional Pelton turbine runner combination has an 18.18% higher hydraulic performance than the hooped Pelton turbine runner under the full gate open condition.It was found that the runners experimented with 23 mm stainless steel nozzles gave maximum efficiency in the case of a hooped Pelton turbine compared to conventional runners at 20% gate opening.However, the polymeric nozzle was best for low runner speed, especially with the Hooped Pelton Turbine runner.The Hooped Pelton Turbine runner has exhibited excellent characteristics with less flow area (part gate opening) for the limited runner speed range than the Conventional Pelton Turbine runner and similar hydraulic characteristics to the conventional runner.Thus, the present study provides a maximum performance aspect of a hooped Pelton turbine runner for nozzle selection.