Particulate flow and erosion modeling of a Pelton turbine injector using CFD-DEM simulations

Abstract

Hydro-abrasive erosion of the injector assembly is a critical issue that affects the operational economy and efficiency of Pelton turbines operating in sediment-laden water. The current study focuses on determining the critical zones of erosion for the Pelton turbine injector. Computational fluid dynamics coupled discrete element method (CFD-DEM) simulations have been adopted to model the sediment-laden flows. The effects of particle rotation and collisions between the particles have been considered while modeling the particle motion. Multi-size particles in the range 75 μm to 350 μm have been considered for the simulation. A semi-empirical erosion model has been developed to predict the erosion of the injector, which includes the effect of particle size on the erosion of the target material. The developed erosion model is calibrated with the available experimental data for the target material, namely turbine steel (CA6NM). The simulated results discuss the physical processes underlying particulate flow and hydro-abrasive erosion. It has been found that the erosion of injector parts namely, nozzle and spear, is asymmetrical. The variation in particle size in the flow is one of the major sources of asymmetrical erosion distribution. The erosion distribution in the nozzle is similar for different nozzle opening conditions. However, the nozzle opening conditions have a significant impact on the erosion distribution and the location of maximum erosion on the spear. At full nozzle opening the tip of the spear is having relatively higher erosion. The present work provides important engineering insights to control the erosion and the problem of jet breakage for the Pelton turbine injector.