This work presents a three-objective design optimization of a centrifugal pump impeller to reduce flow recirculation and cavitation using three-dimensional (3D) Reynolds-averaged Navier–Stokes equations. A cavitation model was used to simulate the multiphase cavitating flow inside the centrifugal pump. The numerical results were validated by comparing them with experimental data for the total head coefficient and critical cavitation number. To achieve the optimization goals, blockage at 50% of the design flow rate, hydraulic efficiency at the design flow rate, and critical cavitation number for a head-drop of 3% at 125% of the design flow rate were selected as the objective functions. Based on the results of the elementary effect (EE) method, the design variables selected were the axial length of the blade, the control point for the meridional profile of the shroud, the inlet radius of the blade hub, and the incidence angle of tip of the blade. Kriging models were constructed to approximate the objective functions in the design space using the objective function values calculated at the design points selected by Latin hypercube sampling (LHS). Pareto-optimal solutions were obtained using a multi-objective genetic algorithm (MOGA). Six representative Pareto-optimal designs (POD) were analyzed to evaluate the optimization results. The PODs showed large improvements in the objective functions compared to the baseline design. Thus, both the hydraulic performance and the reliability of the centrifugal pump were improved by the optimization.

Multi-objective design optimization was applied to the impeller and volute of a centrifugal pump using surrogate-based optimization techniques and three-dimensional Reynolds-averaged Navier–Stokes (RANS) analysis. The objective functions used to improve the hydraulic performance and operating stability of the pump were the hydraulic efficiency at the design condition and the flow rate at which the maximum volute pressure recovery coefficient occurs. Three design variables were selected based on the results of a sensitivity analysis: the blade outlet angle, the constants in determining the impeller outlet width, and the cross-sectional area of the volute. Using response surface approximation (RSA), surrogate models were constructed for the objective functions based on numerical results at experimental points obtained by Latin hypercube sampling (LHS). The representative Pareto-optimal solutions obtained by the multi-objective genetic algorithm (MOGA) show enhanced objective function values compared to the baseline design. The results of unsteady calculation show that the flow instability of the centrifugal pump was successfully suppressed by the optimization.

Submersible pumps are now in high demand due to the sporadic occurrence of recent torrential rains. The current study was carried out to investigate the hydraulic characteristics of a submersible axial-flow pump with a swept impeller and to optimize the impeller and diffuser shapes of the pump to enhance the hydraulic performance. Three-dimensional Reynolds-averaged Navier–Stokes equations were solved with the shear stress transport turbulence model. The governing equations were discretized using the finite volume method, and unstructured tetrahedral and hexahedral meshes were used in the grid system. The optimal grid system was selected through a grid dependency test. A performance test for the submersible axial-flow pump was carried out experimentally, and the results of the numerical analysis were validated against the experimental results. The hydraulic efficiency and the total head were used as objective functions. For the first optimization, a multi-objective optimization was carried out to simultaneously improve the objective functions through a hybrid multi-objective evolutionary algorithm coupled with a response surface approximation by varying the swept angle and pitch angle of the blades of the rotating impeller. The second multi-objective optimization was performed using two design variables, i.e., the inlet angle and the length of the diffuser vanes, to simultaneously increase the objective functions. Clustered optimum designs in the Pareto optimal solutions yielded significant increases in the objective function values as compared with the reference design.

The effects of the cross-sectional area of a volute on suction recirculation and cavitation in a centrifugal pump were investigated. The pump performance and fluid flow were analyzed using both steady and unsteady three-dimensional Reynolds-averaged Navier–Stokes analyses. The shear stress transport (SST) model was adopted as a turbulence closure model, and a simplified Rayleigh–Plesset cavitation model and a homogeneous two-phase mixture model were used to simulate the cavitating flow inside the pump. A constant to determine the designed circumferential velocity of the volute was selected as the geometric parameter for a parametric study. The hydraulic efficiency, head coefficient, blockage in front of the impeller, and critical cavitation number for a head-drop of 3% were selected as the performance parameters to evaluate the hydraulic performance. The results show that unlike the blockage, the hydraulic and suction performances were affected significantly by the volute shape. Both steady and unsteady flow analyses showed that the onset and development of suction recirculation were relatively unaffected by the volute geometry and the best efficiency point of the pump.

The effects of a rotor–stator interface model on the hydraulic and suction performance of a single-stage centrifugal pump have been evaluated. A three-dimensional Reynolds-averaged Navier–Stokes (RANS) analysis was performed using the shear-stress transport turbulence model. The cavitating flow was simulated using a homogeneous two-phase mixture model and a simplified Rayleigh–Plesset cavitation model. Three performance parameters were selected to compare different cases: the hydraulic efficiency, head coefficient, and critical cavitation number for a head-drop of 3%. Frozen-rotor and stage models were evaluated for the rotor–stator interface. The evaluation was done using three different computational domains: one with a single passage of the impeller with a vaneless diffuser, one with a single passage of the impeller with the whole shape of volute casing, and another with the whole passage of the impeller with the whole shape of volute casing. Two different volute shapes were also tested. The results show that it is desirable to use the whole domain of the impeller and volute with the frozen-rotor model for accurate prediction of the suction performance. The stage model is not recommended for the prediction of the suction performance of the centrifugal pump with the volute in severe off-design conditions.

Flow instability and its correlations with performance characteristics were investigated for a centrifugal pump with a volute. Unsteady three-dimensional Reynolds-averaged Navier–Stokes analysis was performed to analyze the flow and performance characteristics using the shear stress transport (SST) turbulence model. The grid dependence and temporal resolution were tested to evaluate the numerical uncertainties, and the numerical solutions were validated using experimental data. The total-to-static head coefficient, the impeller's total-to-static head coefficient, and the volute static pressure recovery coefficient were selected as performance parameters. To identify the flow instability, pressure fluctuations were monitored upstream of the impeller, at the volute inlet, and on the shroud wall of the impeller. Three different types of flow instability were detected in partial-load conditions: inside the volute, upstream of the impeller, and at the interface between the impeller and volute. The time-dependent flow structures were investigated to obtain insight into the onset of the flow instability. The correlation of the onset of the flow instability with the performance curves was discussed.