Shunjun Hong

Erosive wear of centrifugal pumps under solid–liquid two-phase flow critically limits long-term stable operation of fluid transport systems. Current studies lack an in-depth understanding of particle size–solid concentration synergistic effects on internal flow structures and the hydrodynamic link between flow characteristics and wall erosion. Using a single-stage closed-impeller centrifugal pump, this work performs computational fluid dynamics–discrete phase model coupled simulations and systematic erosion tests across three particle sizes (0.6, 0.9, and 1.5 mm) and three solid volume fractions (2.5%, 5%, and 7.5%). The wear resistance and failure mechanisms of atmospheric plasma-sprayed alumina and high-velocity oxygen-fuel-sprayed tungsten carbide–10 wt. % nickel coatings are comparatively analyzed via three-dimensional (3D) optical profilometry, scanning electron microscopy, and energy dispersive spectrometry. Key findings are threefold. First, the impeller outlet average velocity shows non-monotonic variation with rising particle size at high concentrations, arising from the competition between centrifugal particle inertial migration and clustering-induced flow passage blockage. Second, erosion hotspots (blade pressure side trailing edge and volute tongue) are determined by internal flow topology; higher solid concentration intensifies erosion but does not alter hotspot locations. Third, coating failure modes are strongly flow-dependent: Low-angle high-velocity impact at passage outlets causes plastic deformation and micro-cutting, while high-angle inlet impact dominates brittle spalling. This study clarifies the hydrodynamic formation mechanism of wear hotspots and establishes the intrinsic correspondence between local flow parameters and coating failure modes, providing physical guidance for targeted anti-wear design of centrifugal pumps. The coating performance conclusions are valid under the tested conditions.

During flood seasons, gently sloping meandering rivers are prone to developing high-concentration, fine-grained sediment-laden flows with non-Newtonian behavior, which existing discrete-phase numerical models struggle to reproduce accurately in terms of sediment deposition patterns. Based on field-measured sediment parameters, this study employed an Eulerian multiphase mixture model coupled with the Krieger–Dougherty viscosity equation to represent the non-Newtonian properties of the mixture. A three-dimensional geometrically scaled numerical model of the river channel was constructed, followed by mesh-independence testing and validation against field observations. Nine scenarios combining three particle sizes and three inlet sediment concentrations were considered, and a sediment deposition intensity index was introduced to quantitatively analyze the mechanisms underlying spatial differentiation of sediment deposition. The results show that coarse sediment rapidly deposits in upstream bends, whereas fine sediment is transported downstream before settling. Increasing sediment concentration expands the spatial extent of deposition, and under high-concentration conditions, deposition becomes nearly uniform across the riverbed. Channel-widening bends act as sediment deposition hotspots. These findings provide numerical support for sediment management and reservoir operation in high-sediment meandering reaches of inland rivers.

This study presents a computational fluid dynamics investigation of hydrodynamic instabilities induced by inertial particles (Cw=14%) in a centrifugal pump under Southern Xinjiang irrigation conditions. Using high-fidelity Eulerian–Eulerian simulations with four-way coupling via the kinetic theory of granular flow, we identify a critical Stokes number (Stcrit≈0.45) that marks the transition from stable, stratified particle-laden flow to unstable regimes. Below this threshold (St≪1), fine particles follow fluid streamlines with negligible vorticity distortion, preserving the base flow stability. At the critical threshold, vorticity amplification occurs in the impeller core, characterized by the formation of coherent vortical structures, pressure distortion, and vortex-induced backflow. For coarse particles (St>1), the system enters a developed inertial instability regime featuring significant turbulence modulation and a nonlinear energy cascade from mean flow kinetic energy into particle fluctuation energy (quantified by granular temperature). Experimental validation via scanning electron microscopy confirms that simulated instability zones and high-impact regions correlate with observed material wear patterns. These findings identify a critical Stokes number threshold for instability onset under the investigated conditions, providing a reference for flow regime prediction in sediment-laden centrifugal pumps.

Hydraulic cavitation is the primary cause of cavitation erosion in Francis turbine runners. Under the special hydrological conditions prevalent in the desert margin areas of southern Xinjiang, cavitation erosion damage to the runner is particularly severe. Taking the HLJF2062-LJ-200 Francis turbine as the research object, this study employs unsteady numerical simulations of the full flow passage, incorporating the shear stress transport k–ω turbulence model, the volume of fluid multiphase flow model, and the Zwart–Gerber–Belamri cavitation model. It investigates the cavitation characteristics and erosion patterns of the runner under three guide vane openings (14° for low-load, 21° for rated-load, and 28° for high-load conditions) and within a cavitation coefficient range of 0.06–0.20. The results show that cavitation is concentrated on the suction side of the blades near the band side, which constitutes the core cavitation erosion zone. The critical cavitation coefficient increases as the guide vane opening decreases, with values of (σ = 0.06–0.08, 0.08–0.10, and 0.10–0.12) for large, design, and small openings, respectively. The simulation results are consistent with the field measurements of cavitation erosion of the prototype turbine under high-load conditions, providing a theoretical and engineering reference for the operational regulation and anti-cavitation protection of hydraulic turbines in high sediment-laden water regions.

Research methodology flowchart illustrating the four-stage approach: pump model building, CFD Fluent simulation, experimental wear testing with SEM microanalysis, and conclusion synthesis identifying wear thresholds and operational optimization strategies. The diagram includes pump geometry renderings, velocity contour visualizations, and experimental apparatus photographs. This study investigates flow characteristics and wear evolution in centrifugal pumps handling fine-sand-laden water via numerical simulations and experiments. Using a validated Realizable model, five rotational speeds (2030-3480 r/min) for clear water and five sediment concentrations (6%-20%) were analyzed. Results demonstrate that 2900 r/min achieves optimal flow stability with minimal turbulence kinetic energy (TKE), while exceeding 3190 r/min induces flow separation. A critical sediment concentration of 14% was identified: below this threshold, flow fields remain orderly; above it, particle enrichment on blade pressure surfaces amplifies localized TKE and causes severe velocity fragmentation. Experimental wear tests and SEM analysis confirmed cutting wear and dimple-lip deformations at inlets/outlets, aligning with numerical predictions. Maintaining operation at 2900 r/min with concentrations ≤14% minimizes wear. It is recommended to optimize speed, control inlet sediment below 14%, and reinforce critical wear areas.

Graphical abstract based on characteristics of low velocity, vortices near the main flow region, and low turbulent kinetic energy, revealing the relationship between hydraulic performance and clogging of low-flow drip irrigation emitters under sediment-laden conditions This study evaluates the anti-clogging performance of two inline patch-type drip irrigation emitters (high-flow: 2.4 L/h; low-flow: 1.4 L/h) under high fine-sediment conditions (5 g/L, median particle size 0.10–0.11 mm) typical of Southern Xinjiang. Hydraulic performance tests, intermittent clogging experiments, and numerical simulations (Eulerian multiphase flow and discrete phase model) were combined for analysis. Results show that the low-flow emitter, despite a lower flow behavior index (0.404) indicating better hydraulic stability, exhibited weaker anti-clogging capacity: its average flow rate decreased by 28%, with a clogging rate of 23%. In contrast, the high-flow emitter (flow behavior index: 0.535) experienced only a 16% flow reduction and a 10% clogging rate. Simulations revealed that the high-flow emitter maintains vortex structures under sediment-laden flow, promoting particle resuspension and resulting in a shorter average particle residence time (0.1579 s) compared to the low-flow emitter (0.3392 s). Clogging primarily occurred at low-velocity zones such as inlets, turns, and outlets. Operational recommendations include maintaining system pressure at 60–80 kPa, controlling sediment concentration ≤5 g/L, and implementing a two-stage filtration system with regular flushing to enhance long-term reliability.

To address the severe performance degradation (head reduction ≤43%) and shortened service life of centrifugal pumps caused by high-concentration fine-sand water in Southern Xinjiang irrigation districts, this study establishes a multiphase flow-wear coupling analysis framework. Using experimentally validated realizable k-ε modeling, we investigate flow patterns and wear mechanisms under both clear and sediment-laden conditions (15%/16.5% concentration, 0.06–0.40 mm particles). Under clear water, 0.95Q ensures optimal pressure-streamline synergy, whereas 0.75Q induces vortex breakdown with TKE surges, and 1.15Q accelerates efficiency decay. At 15% sediment concentration, 0.15–0.25 mm particles achieve hydraulic compatibility. Increasing to 16.5%, fine sand (<0.1 mm) triggers nested ‘vortex-in-vortex’ structures, while 0.15 mm particles exhibit a 25% steeper concentration gradient. Coarse sand (0.40 mm) forms settling nuclei in the impeller. The impeller outlet shows maximal wear, validated experimentally. This study offers theoretical and technical support for pump operation in sediment-laden flows.