Numerical Analysis of Traditional and Hooped Pelton Runner at Various Operating Conditions

Abstract Pelton turbine is an impulse turbine that converts kinetic energy of incoming jet of water into mechanical energy. Due to impingement of high-speed jet on buckets, Pelton turbine experience high stress at the tip of bucket and at the connection of bucket and rim. To provide the structural strength to the runner, a hoop is attached to it which allows better distribution of forces. However, the impact of hoop on the hydraulic performance of runner is important to assess. For this, a numerical analysis based on Computational Fluid Dynamics has been performed on both traditional and hooped Pelton runner. Transient analysis has been done to calculate the efficiency of both runners under same boundary conditions. The analysis was performed at different openings of needle. Numerical study showed that the efficiency of hooped Pelton runner is less compared to traditional Pelton runner at higher and medium openings. However, at lower openings hooped runner is more efficient. The efficiency drop was in the range of 3.56% to 1.25%. Flow contours reveal that obstruction of fluid is more prominent at higher opening than lower openings, which is the main reason for efficiency drop. Hoop, despite giving structural strength to the runner, is detrimental to the hydraulic performance of traditional runner.