Numerical Investigation of Hydraulic Performance Improvement in an Optimized Pelton Turbine Runner

Abstract

Pelton turbines are widely used in high-head hydropower applications because of their high efficiency and reliable hydraulic performance. In this study, an existing Pelton turbine runner was used as the reference design, and an optimized runner was developed by modifying key geometric parameters, particularly the pitch circle diameter and bucket width. The reference runner had a pitch circle diameter of 312.5 mm and a bucket width of 90.3 mm, whereas the optimized runner was designed with a pitch circle diameter of 450 mm and a bucket width of 130 mm. The novelty of the work lies in the direct evaluation of a geometrically modified runner against its reference design under similar operating conditions while resolving the transient jet–bucket interaction through a VOF based numerical approach. Experimental measurements and three-dimensional simulations were used to analyze hydraulic efficiency, torque response, pressure development, and internal water-sheet behavior. The optimized runner demonstrated a marginal efficiency increase from 91.7% to 91.8%. This small difference should be interpreted cautiously, as it may lie within the range of numerical and experimental uncertainty. Accordingly, the main contribution of the study is not a significant efficiency improvement, but a clearer physical understanding of how runner geometry, jet diameter, and nozzle number jointly influence flow guidance and hydraulic loading. The results provide useful guidance for Pelton runner refinement, multi-nozzle matching, and future optimization studies involving coupled hydraulic, cavitation, and structural reliability assessments.