Experimental study on particle movement and erosion behavior of the elbow in liquid-solid flow

Recent investigations into the erosion of elbow junctions predominantly focus on identifying and predicting peak erosion points. Notably, these studies rely heavily on computational fluid dynamics methods, a valid approach but limited by its lack of empirical physical data. Additionally, the majority of these studies concentrate on the extrados, or outer curve of the elbow, neglecting the intrados or the inner curve. To provide a more comprehensive understanding of particle movements and the micro-mechanics of erosion on the elbow intrados, this study utilizes advanced observational technologies. High-speed camera technology, coupled with scanning electron microscopy, is employed to capture and record particle motion and micro-erosion patterns. The erosion rate is then estimated via the weight-loss method. The findings suggest that in low-speed liquid-solid flows (2.5 m/s), particles released from the intrados side of the elbow inlet exhibit a significant trajectory deviation from the centreline at an elbow angle of 60° from the inlet. Particles released from the extrados deviate towards the intrados side at an elbow angle of 30°. Secondary flow contributes to particle acceleration, unexpected trajectory deviation within the elbow, and an upward inclination in erosion on the intrados. The presence of partially overlapping scratches and cracks suggests that continuous ploughing and material fracturing are significant contributors to the micro-mechanics of erosion. When comparing the intrados and extrados, the extrados exhibits longer and shallower scratches, indicating a smaller impact angle. This research provides a more comprehensive understanding of particle trajectories and erosion patterns within elbow junctions during liquid-solid flows, offering new insights into the mechanisms underpinning these processes.