INVESTIGATION ON COMBINED EFFECT OF CAVITATION AND SILT EROSION ON HYDRO TURBINE

Abstract

In the present scenario of growing-- luxurious and developing world the energy demand .-is continuously increasing and, on-. the other hand the conventional resources of . energy generation (coal, -oil, natural..gas) or -fossil fuels are continuously depleting. Due to the use of fossil fuel the environmental! pollution problem occurs and the trend changes towards the -renewable energy generation. The. hydro power generation is one of the economical and environmental • friendly renewable energy systems. But due to environment constraints large hydro schemes are always not considered, socially and politically feasible. Hence the small, mini, and micro hydropower schemes came into existence. In hydropower sector, cost-effective design of different components is always a challenging task. For cost-effective design of -hydraulic components highly complex flow, -which is turbulent and three dimensional in nature, is to be analyzed critically. As such, there are various components which come in contact with the water, but turbine is the most critical component - because it has a considerable influence on the cost of civil works, overall performance as well as life of any hydropower project. But hydro turbine faces various problems during its working life. The major problem associated with the hydro turbine used in hilly region is that of silt erosion and cavitation, which erodes the turbine parts due to which the fall in efficiency occurs in hydro turbine. In present study, a Francis turbine of rated capacity of 3 MW is simulated for the CFD analysis to investigate the combined effect _of the cavitation and silt erosion on the hydro turbine. Flow analysis of the Francis turbine is carried out by using `Fluent' module available in 'ANSYS . - 14'. The flow simulation was carried out in four different flow conditions namely under pure water flow condition; cavitation flow condition, sediment flow condition and combined flow condition. The efficiency of the Francis turbine was calculated in each case and the comparison was made. It has been observed that the drop in efficiency was much higher in case of combined flow condition rather than the other two cases of cavitation flow and sediment flow. The :affected zones of the runner blade were identified and the erosion rate was found to be highest in the case of combined flow condition.