Abstract: Hydraulic machinery operating on sediment-laden rivers suffers from sediment erosion, which causes the deformation of flow passages, reduction of hydraulic efficiency, and even shutdown of the unit. By taking advantage of a rotary jet device, this study conducts a sediment abrasion and erosion experiment on materials used for hydraulic turbines under different impact velocities and impact angles, and investigated the measured sediment abrasion characteristics using the weight loss method along with microstructure analysis. The results indicated that for three types of materials, the weight loss and the facilitation of cavitation on sediment abrasion take an exponential increase with impact velocity, along with the increase in the surface roughness, the size of cutting scratches as well as cavitation pits. For all materials, the impact angles that maximize weight loss are roughly 40° and 45° for abrasion and erosion respectively. The vertical impact effect and horizontal removal of particles match best at 45° impact angle, and the particle impact forms disc-shaped pits of which the surface lip edges are removed by horizontal cutting, resulting in significant weight loss. At 45° impact angle, cavitation induced by the jet nappe is the most severe, and the combined abrasion-erosion damage causes relatively deep pits on the material surface, which leads to the weight loss twice of that in abrasion test.

Key words: hydraulic machinery, sand abrasion, erosion, impact velocity, impact angle, rotary jet device