Numerical Investigation of Pelton Turbine Distributor Systems with Axial Inflow

Abstract

In an agile power grid environment, hydroelectric power plants must operate flexibly to follow the demand. Their wide operating range and high part-load efficiencies allow for multi-injector Pelton turbines to fulfil these demands as long as the water jet quality is maintained. The water jet shape is governed by the flow in the distributor system. Pelton distributor systems with axial feed can potentially reduce the costs of the power station. Providing the flow quality at the nozzle outlet challenges the design of such Pelton distributors. Therefore, numerical simulations are performed to optimise a parameterised Pelton distributor system with axial feed. The effects of geometric parameter variations on its performance are studied. The criteria to evaluate the flow in distributor systems are presented, which are applied to quantify the power losses and secondary flows. Additionally, the second law analysis illustrates where the losses are generated. Due to various pipe bends, all designs exhibit a distinct S-shaped secondary flow pattern at the nozzle inlet. The simulations reveal that the power losses are greatly reduced by shaping the initial part of the branch line as a conical frustum. Deviation angles of the branch line close to 90° allow for lower secondary flow magnitudes at the nozzle inlet.