Effect of Particle Size and Solid Concentration on Sediment Erosion of High Head Francis Turbine

Abstract

The hydro-turbines installed in the Himalayan region have the problem of sediment erosion due to sand-laden water. In the current study, an estimation of erosive wear is numerically performed for the high head Francis turbine of the Bhilangana- III hydropower plant. The effect of operating parameters by varying the particle size from 100-300 micron and solid concentration from 1000-4000 ppm is studied at best efficiency point (BEP) operation. The erosion rate calculation is performed using the modified Grant and Tabakoff model for martensitic stainless steel (contain Carbon 0.067%) due to quartz sand. The predicted erosion patterns were similar for both, particle size and solid concentration. The leading edge of guide vane and stay vane are found as high erosion-prone zone due to high absolute velocity in these regions. In runner, mainly erosion is found on the outlet of pressure side vane and shroud due to high relative velocity and high solid volume fraction. Also, cross flow in runner flow passages due to incorrect blade leaning angle may enhance erosion wear. It is found that the runner is a highly eroded component of the Francis turbine in the present operating conditions. The numerically identified eroded zone of different components of Francis turbine are compared with the on-site observation. The numerical identification of these zones may be helpful for the design modification and optimization of turbine components.