Hydraulic performance prediction of a prototype four-nozzle Pelton turbine by entire flow path simulation

This paper presents entire flow path simulations in a prototype four-nozzle Pelton turbine under three water heads, from pipe flow to nozzle jet water sheet flow on rotating bucket and drop from bucket brim on the air. Different type flows in the Pelton turbine are analyzed by adopting the three-dimensional transient air-water two-phase flow simulation method. Hydraulic performance of stationary parts and rotating runner are evaluated along the entire flow path. Flow analyses indicate that the pressure pulsation is very low and the water flow could be regarded as steady flow in the stationary parts. The hydraulic loss in these parts drops as the water head increases due to a reduction of the frictional loss. Afterwards, the interactions between the jets and buckets in the rotating runner are discussed. The pressure pulse on the bucket surface pulsates with the spreading of the water sheet flow and takes up 10%-25% water energy. The hydraulic performance of the bucket is highest at optimal water head and decreases as the water head varies. Unsteady flow analyses show that there is a potential for interference between the two adjacent jets if the water head or the angle between the two jets decreases.