冲击式水轮机作为高水头、低流量的理想设备，常被布置在高海拔山地。其在运行过程中，高速含沙水流极易对给水机构造成破坏。为探究不同泥沙粒径对配水环及喷射机构的磨损特性，该文采用湍流模型和DPM（discrete phase model）离散相模型，对六喷嘴给水机构进行水-气-沙三相非定常数值模拟。结果表明：多喷嘴配水系统的分流作用，使下游流道内的颗粒数量大幅减少，因此磨蚀区域主要集中于上游流道和1-3号喷射机构内；在配水环流场中二次流现象显著，由于惯性效应和Dean涡的共同作用，磨蚀区域主要集中于弯管、分岔管附近和喷射机构内的涡流区域，表明给水机构内磨蚀主要受二次流主导；颗粒属性对喷射机构磨蚀具有显著影响，小粒径泥沙由于具有更强的随流特性，主要对喷针表面产生磨蚀。残留Dean涡在喷针收缩段被重新激发，强化了涡流区域颗粒聚集，使其和喷针表面的碰撞率增高，加剧了小颗粒对喷针的磨蚀；大粒径泥沙惯性效应强、随流性差，其运动轨迹和流线偏差大，主要对喷嘴外壳产生磨蚀；对于级配颗粒群，则呈现出明显的协同磨蚀效应，细颗粒主要集中作用于喷针表面，造成磨蚀性破坏，而大颗粒则更易冲击喷嘴壳体，导致该区域磨蚀加剧。

Objective: As ideal hydraulic machines for high-head, low-flow hydraulic energy conversion, Pelton turbines are widely deployed in high-altitude mountainous regions. They play a crucial role in hydropower generation and water resource utilization. However, long-term operation with high-velocity sediment-laden water leads to severe erosion of key components such as the water distribution ring, injectors, and runner buckets. This erosion reduces turbine efficiency, shortens service life, increases maintenance costs, and poses safety risks. Thus, systematically investigating how sediment particle size affects the erosion characteristics of these components is theoretically and practically crucial, thereby providing technical support for optimal design, anti-erosion modification, and safe operation of the Pelton turbine. This study aims to examine the influence of sediment particle size on the erosion characteristics of the water distribution system. Methods: This study employs the SST k–ω turbulence model, coupled with the discrete phase model, to perform unsteady three-phase (water–air–sand) numerical simulations of a six-nozzle distribution system. Results: The results show the following: 1) The multi-nozzle distribution system exhibits a notable flow-diversion effect. Particle trajectories show that the downstream channel receives a substantially reduced number of particles; consequently, erosion damage is primarily concentrated in the upstream channel and the first three injectors. 2) Secondary flow phenomena, particularly Dean vortices, arise from the combined effects of inertia and curvature within the water distribution ring. Erosion distribution correlates strongly with these flow structures, with damage concentrated near elbow sections, bifurcated pipe junctions, and internal vortex regions within the injectors. This indicates that erosion in the water distribution system is predominantly governed by secondary flow dynamics. 3) Particle properties have a remarkable impact on injector erosion. Fine sediment particles, due to their strong flow-following characteristics, mainly erode the needle surface. Moreover, residual Dean vortices are reactivated in the contraction section of the injector, intensifying particle accumulation in the vortex region and increasing the collision rate with the needle surface, thereby exacerbating needle erosion. 4) Large sediment particles exhibit strong inertial effects and poor flow-following characteristics, causing their trajectories to deviate considerably from streamlines and mainly erode the nozzle shell. 5) In a mixed particle-size group, a notable synergistic erosion effect is observed: fine particles primarily damage the needle surface, whereas large particles are more likely to impact the nozzle shell, further intensifying erosion in that area. Conclusions: The multi-nozzle water distribution system demonstrates a pronounced flow diversion effect, substantially reducing the number of particles in the downstream channel. Consequently, erosion is primarily concentrated in the upstream channel and the first three injectors. Secondary flow and Dean vortices are prominent in the water distribution ring, with erosion predominantly occurring near elbows, bifurcated pipes, and internal vortex regions of the injectors, driven by secondary flow dynamics. Sediment particle size considerably affects the distribution and intensity of injector erosion. Fine particles, with strong flow-following abilities, erode the needle surface, whereas residual Dean vortices in the contraction section exacerbate this erosion. By contrast, large particles, with strong inertia and poor flow following abilities, deviate from streamlines and erode the nozzle shell. Mixed particle sizes exhibit a synergistic erosion effect, intensifying overall injector damage.