Cavitation erosion at runner blades in a Francis turbine at the Tarbela Dam Hydro Project

Cavitation erosion damage in hydro turbines used in power generation stations requires continuous and costly maintenance. Initiation and growth of cavitation damage depends upon factors like atmospheric pressure, suction pressure, flow velocity, temperature, amount of vapor, and the operating time of the turbines. The foregoing factors vary from site to site for a particular turbine and are used to quantify cavitation damage. The Tarbela Dam Hydel Project (TDHP) is facing cavitation problems on the turbine runner in its Francis Turbines. Numerical analysis of the scaled down TDHP unit has been conducted to model and quantify the cavitation rate and efficiency losses as a function of suction head (SH) and flow velocity (FV). A homogeneous cavitation model was used. Furthermore, mass loss as a function of SH and FV is also discussed to quantify the runner blade wear effects. Validation of the numerical results is achieved using published experimental data for situations having similar geometry and operating conditions. Modeling results show good agreement with experimental data for given rated load conditions.