Theoretical method of selecting number of buckets for the design and verification of a Pelton turbine

Abstract

In this study, we develop a theoretical formula for determining the optimum number of buckets required for achieving the maximum possible efficiency of a Pelton turbine. In addition, by deriving an improved formula for determining the speed ratio limit at which a missing jet begins, we obtain a valid condition for the selection of the number of buckets. To validate these formulas, we conduct a performance test on a pico-scale Pelton turbine by using runners with different numbers of buckets. The results of the performance test validate both the formula for bucket selection, by confirming that the calculated number of buckets maximizes the efficiency of the Pelton turbine, and the formula for the speed ratio limit. We conduct an additional performance test on a micro-scale Pelton turbine, the results of which also verify the formula for selecting the number of buckets. This study should help researchers determine the appropriate number of buckets when designing a highly efficient Pelton turbine.