Partial jet cutting and torque evaluation on cut-in jet deflector for Pelton turbine

Deflectors of Pelton turbine divert the jet completely and prevent the turbine from going to run away speed in case of load rejection. Moreover, partial cutting of the jet using cut-in jet deflector plays a role in fast controlling of power and the associated positive effect on the stabilization of the electrical grid. During this control operation cut-in jet deflectors are subjected to forces and torques which must be handled by the servomotor. Therefore, experimental measurements at different angular positions of the cut deflector are required to determine the torque for the design of the deflector and its servomotor. During the partial jet cutting the jet quality is also important as the remaining jet has to impact the Pelton runner for active power generation. In this study, an experimental investigation was carried out using a torque transducer. In addition, CFD simulations were conducted to observe the flow behavior of the jet during cutting. It is observed that the torque acting on the cutin jet deflector increases with increasing the jet cutting angle but shows a decreasing tendency after reaching the maximum value. At lower jet cutting angles of 3 degrees and 6 degrees, the jet remains nearly straight, indicating minimal deviation.