Abstract: During external characteristic experiments of centrifugal pumps conveying fiber suspensions with varying concentrations,it was observed that the 0.2% concentration fiber suspension exhibited universal applicability in pump efficiency enhancement,demonstrating efficiency improvement across all flow-rate conditions.In contrast,the 0.6% concentration suspension only improved pump efficiency under high-flow-rate conditions.To elucidate this phenomenon from a microscopic perspective,MATLAB-based image recognition techniques were employed to statistically analyze the orientation angles of fibrous particles within the CFD-DEM coupled flow field.The results revealed distinct orientation trends in fiber distribution: low-concentration suspensions exhibited fibers predominantly aligned with the fluid flow direction,characterized by higher orientation stability,smaller orientation angle variations,and a higher proportion of high-velocity particle clusters.