INVESTIGATION OF STRESSES IN ALUMINIUM A356 ALLOY PELTON TURBINE BUCKETS

Abstract

The need to predict performance of Pelton turbines in terms of efficiency and dynamic behavior under different operating conditions is paramount. It has been established that an increase in performance leads to a decrease of the ratio between the bucket width and the jet diameter. This leads to an increase in cyclic load and therefore an increase in stresses on the buckets and the turbine hub leading to failure. This paper seeks to demonstrate how to optimize the bucket profile in order to hence performance of Pelton turbine buckets for Pico hydro electric systems. Two models of 152mm pitch circle diameter Pelton turbine buckets were designed using Computer Aided Design (CAD) software and investigation on forces and stresses done using structural analysis on ANSYS software. The simulations results were compared with experimental results for the two models casted from recycled aluminium A356 alloy. The investigation indicated that there was a 14.2% reduction on stresses developed by introducing a ridge on the buckets backside. The result was a higher power output achieved by optimizing the buckets profile without altering the bucket width in relation to water jet diameter.