Performance of Pelton turbine using ANSYS mechanical APDL: Modal analysis

Abstract

Presently, there is huge demand of global renewable energy such as solar energy, wind energy, geothermal energy, hydropower, biomass, and wave energy. Hydro offers the most effective outcomes throughout all phases of the energy transition. Since 75% of the earth's surface is covered by water, water power represents a sizable source of free and sustainable energy on earth. The hydropower turbines, such as Pelton wheel turbine, are expected to work in severe operating conditions that may affect its structural integrity. However, the life span of the Pelton turbine can be compromised if the resonance occurs due to structural vibration and dynamic stresses. In present study, computational study is performed to detect the structural damage of bucket of Pelton turbine for both structural and modal analyses using commercial software ANSYS^®. The quantities such as overall deformation, von Mises strain and von Mises stress are determined from static analysis while various mode shapes and associated natural frequencies are predicted through modal analysis. At first, the static structural analysis is performed by applying load and then implementing the developed stress field in the modal analysis to evaluate safety limits of structure with respect to resonance. The various mode shapes and associated natural frequencies are predicted using Block Lanczos method. The deformation of 8 mm is obtained for uniform pressure load, while the maximum deformation of 25 mm is obtained by applying both pressure and force. The estimated lowest modal natural frequency is 4231.8 Hz while the maximum frequency is determined as 16126 Hz. The results show that the bucket passing frequency does not match with natural frequency resulting in safe design and operation of turbine. The present results may contribute in improvement of reliability and efficiency of turbine operation.