Study of Pressure Pulsations in a Francis Turbine Designed for Frequent Start-Stop

Abstract The energy market aims for high flexibility that allows guaranteed power to the consumers with minimum carbon footprint. Over the last three decades, hydropower has been a reliable and an efficient option to meet the fluctuating energy demand as it allows high-ramping rate and quick start-stop. However, such critical operations bring certain challenges for hydro turbines, i.e., high-amplitude stochastic loading and the fatigue. Credible investigation of unsteady pressure pulsations and their signature is important to understand the consequences. The present work aims to study pressure pulsations in a model Francis turbine, which is designed for the frequent start–stop operations. A total of 112 numerical simulations, across the hill diagram, are conducted. Pressure pulsations in the vaneless space, blade channels, and draft tube are investigated. The results show distinct patterns of rotor-stator interaction frequencies in the turbine. In the regions of high rotational speed and low flow rate, stochastic pulsations are predominant.