Analysis of internal flow characteristics and loss mechanism of Pelton turbine's water supply component

The Pelton turbine is widely used in current hydraulic development based on its high utilization rate and wide range of applicable heads. When fluid flows within its water supply component, frequent changes in flow states induces a series of adverse flows such as secondary flow and Dean vortexes, resulting in hydraulic losses. This study simulates the water-air unsteady flow characteristics by taking the water supply component of a four-nozzle Pelton turbine as the research object. Discussing the influence of nozzle openings and heads on the Pelton turbine's flow loss based on entropy production theory and pressure drop method. The results indicate that: (1) Low-speed reflux vortexes are formed in the inner side of distributor and bifurcations due to the influence of flow inertia, generating periodic pressure pulsations and inducing energy loss. Then some vortexes enter the nozzle under the force of diversion effect. As flow continues, they enter the jet domain, causing shear effects that will deform the jet shape and affect its quality. (2) At the distributor outlet #2 and #3, where curvature is the highest and the loss accounts for approximately 75 % of the total loss in distributor. As for nozzle domain, the loss of &2 and &3 also account most proportion. (3) The flow loss of water supply component is positively correlated with water head and negatively correlated with nozzle opening. Under various calculation conditions, the nozzle domain's loss accounts for over 95 % while the loss of distributor accounts for less than 5 %. The energy dissipation caused by velocity gradient always dominates the irregular flow in fluid field, so the loss caused by fluctuation entropy production is the main source of flow loss.