SPH simulation of Pelton turbine jet–runner–casing interaction and overspeed transients during emergency shutdown

Although Eulerian Computational Fluid Dynamics (CFD) approaches are well established for reaction turbines, the numerical modeling of impulse turbines, such as Pelton turbines, remains challenging due to the strongly transient and multiphase nature of the flow, and complex jet–runner interactions. This study presents the analysis of a Pelton turbine considering two critical scenarios. First, operational conditions, such as efficiency and optimization of the runner–casing–jet interaction, and second, emergency shutdown maneuvers in which the electrical load is suddenly removed while the jet is still acting on the runner, causing overspeed. These tests are performed using the open-source DualSPHysics, which is based on the meshless Lagrangian Smoothed Particle Hydrodynamics (SPH) method, validated against experimental data with a resolution convergence study and completed with a joint sensitivity analysis over 199 simulations, which quantifies the relative influence of the principal numerical parameters. The investigation of the casing configuration has driven a critical flow optimization, leading to the redesign of the casing and its testing on a physical rig. Finally, an emergency shut-down maneuver is simulated as a fully coupled three-dimensional transient, in which the runner speed evolves dynamically under the computed hydraulic torque, and the SPH results are compared against a reference code for hydraulic transients. The two predictions of the maximum overspeed agree to within 1%.