Influence of Impeller–Diffuser Side-Gap Flow with a Simplified Leakage Model on the Performance and Internal Flow of a Centrifugal Pump

This study conducts a numerical analysis to understand the effect of flow through the impeller–diffuser side gap on the performance and internal flow of a centrifugal pump. Three-dimensional steady-state Reynolds-averaged Navier–Stokes simulations are performed, employing the shear stress transport turbulence model for turbulence closure. To analyze the effects of side-gap flow on the main passage flow, a simplified fluid domain for the side gap is constructed and applied with a one-dimensional loss model for the leakage flow. The numerical results are validated with experimental data for performance curves and velocity components at the diffuser inlet. For a detailed analysis of the leakage flow, flow simulations are carried out for three cases: flow absence, inflow, and outflow (leakage) in the impeller–diffuser gap. Significant performance deviations are observed according to the flow direction in the gap, and the detailed fluid flow structures are examined to assess its impact on the performance.