Establishment of correlation for the pressure fluctuations on the low-head Francis turbine in the draft tube cone from the model test

Abstract

Pressure fluctuation is an essential metric for assessing the effectiveness of the functioning of a hydraulic turbine. During the operation of the hydraulic turbine, pressure fluctuations occur under varied load conditions. An advanced data acquisition system and measurement setup were designed to investigate the pressure fluctuation characteristics in the Francis turbine model with three pressure heads. The operating points for pressure fluctuations investigations ranged from lower part load to overload condition. The plant sigma condition is studied extensively under three different heads, i.e. 30.45 m, 31.98 m and 38.78 m. The miniature-type pressure transducers are used for the investigations. Three pressure sensors, one in the inlet of the spiral case, second and third in the draft tube upstream and downstream respectively, are installed. The measurements were conducted in different operating conditions considering the prototype output power of 16.7 MW, 20.3 MW, 27.8 MW, 34.3 MW and 40.4 MW. A correlation has been developed to represent the variation of draft tube cone pressure fluctuations concerning head and output power.