Evaluation of uncertainties in pressure fluctuations measurement on low-head Francis turbine model during part-load operation

Abstract

The Francis turbines are often operated at the part load (PL) conditions to meet the electricity demand while maintaining system stability. During PL operations, the turbine experiences flow instabilities and vortex formation in the draft tube, leading to potential damage to the turbine. This experimental study focused on measuring pressure fluctuations in a model low-head Francis turbine at PL operation, i.e. 70% of rated load condition. Eight pressure sensors were installed at various locations to measure the pressure fluctuations. In-situ calibrations were performed for various measuring instruments used in testing, such as flow meters, pressure transducers, torque transducers, and speed sensors. The uncertainty evaluation for hydraulic turbine efficiency and pressure fluctuations in the draft tube cone was carried out at the PL operations. Quantifying the uncertainty for both Type A and Type B was conducted. The maximum estimated uncertainty for measuring hydraulic turbine model efficiency is ±0.272% and for pressure fluctuations during PL operation is ±1.358%.