LAUSR

Abstract The quality of the jet injected from a nozzle is one of the key factors that affects the performance of Pelton turbines. In this study, for the first time, experiments and numerical simulation were conducted to investigate the effect of the spear needle eccentricity on the jet flow in micro Pelton turbines. Results show that the eccentricity of the spear needle causes jet diffusion under low flow conditions and significantly increases the loss of the spear nozzle (injector). Furthermore, the increase in the eccentricity ratio causes extreme jet separation and jet diffusion, and the loss of the spear nozzle increases by 52% (from 453 W to 688 W) when the eccentricity ratio increases by 6%. Analysis of the results confirmed that the pressure deviation and jet velocity imbalance caused by eccentricity are the primary causes of jet diffusion. Furthermore, the results confirm that the eccentricity of the spear needle in the case of a low-capacity Pelton turbine has a significant effect on the jet quality. Thus, further studies on the eccentricity are required to improve the performance of the Pelton turbine.