On the impeller wear of vertical centrifugal pump carrying water–sand two-phase flow with fine particles: Characteristics and mechanisms

Large-scale vertical centrifugal pumps are widely used in the water diversion projects in China, and the pumping stations often operate in the river environments with suspended sediments. The problem of impeller wear caused by sediment-laden flow is very prominent, seriously affecting the safety, stability, and efficient operation of the units. The sediment-laden flows in large-scale vertical centrifugal pumps exhibit the features of high volumetric concentration and small particle size (huge number of particles per unit volume). Under these service conditions, the characteristics and mechanisms of impeller wear are still not fully understood. This study takes a vertical centrifugal pump model as an example and conducts research in combination with hydraulic model experiments. First, a new Eulerian–Eulerian two-phase flow model suitable for high concentration and fine particle water–sand two-phase flows in centrifugal pumps is established. Second, a new wear model applicable to the base material of the impeller wall of a centrifugal pump is calibrated. Third, the water–sand two-phase flows in the vertical centrifugal pump under the conditions of different fine particle sizes are simulated, and the characteristics of erosion rate, particle impact velocity, and particle impact angle in the impeller are quantified. Moreover, based on the dynamic balance relationship of the relative motions, the mechanism behind the impeller wear under this condition is revealed, which originates from the special balance between the potential rothalpy gradient, the Coriolis force, and the drag force. In summary, the above results can provide valuable guidance for the anti-wear protection of large-scale vertical centrifugal pumps.