Measurement and analysis of sediment erosion of a high head Francis turbine: A field study of Bhilangana-III hydropower plant, India

Abstract

The problem of silt erosion is prevalent in hydropower plants of the Himalayan region. In the present study, a measurement methodology is undertaken to investigate the erosion damages of the Francis turbine components of unit-2 of Bhilangana-III Hydro Electric Plant. For the operation of 6993.12 h, a total sediment load of 29,291 MT was passed through the turbine. Around 90% of suspended silt particles were less than 300 μm size, with a modified shape factor of 0.75. The maximum overall weight loss is found as 29 kg for the tungsten carbide coated runner. The initial clearance gap of the guide vanes was increased from 0.04 to 0.55 mm to 0.65 mm and 0.69 mm at leading and trailing edges, respectively. In the runner, the average thickness loss at the blade trailing edge was found as 3 mm, 1.25 mm, and 1.56 mm from shroud to hub for three different templates as per IEC-62364. The maximum erosion depth of 13 mm is measured for the curved part of the runner. The ripple pattern of erosion is observed to be responsible for the material loss from the runner. The observed erosion-prone zones of turbine components are further investigated through CFD analysis at the best efficiency point.