Centrifugal pumps are the critical components in deep-sea mining. In order to investigate the particle motion in the curved channel of the impeller, three different types of curvature conform to blade profile to simplify the impeller design of pumps. A numerical study is conducted to investigate the flow field in a varying-curvature channel for solid-liquid two-phase flow. The flow of particles within the varying curvature channel is studied by combining the discrete element method (DEM) with computational fluid dynamics (CFD) and a comparison with Particle Image Velocimetry (PIV) test results. The results show that a polyhedral mesh with a small mesh number yields very accurate results, which makes it very suitable for CFD-DEM. Based on this method, the movement of a single particle is compared and analyzed, and the particle-motion law is obtained. The effects of the curvature ratio Cr and area ratio Ar on the motion law for a single particle are studied, and the simulation results are analyzed statistically. The results show that the effect of Cr on both the particle slip velocity and the turbulent kinetic energy only changes its strength, while the distribution law does not change significantly. Compared with the curvature ratio Cr, the area ratio Ar has a greater impact on the particles, and its distribution law becomes clearly different. As the area ratio Ar increases, the arc radius and length of the corresponding particle trajectory decrease.

A new type of dishwasher pump without a pipeline system was invented for the first time to form an original sink-type dishwasher avoiding the accumulation of dirt in the hydraulic system. In order to improve the hydraulic performance of this new type of dishwasher pump with twin-volute passive rotation driven by a compound impeller, an orthogonal optimal design method was first introduced to optimize the compound impeller composed of axial cascades and radial blades. Six geometric parameters were selected as the main factors to design the orthogonal table L₁₈(3⁶). All impeller models were manufactured via high-precision 3D printing and tested to determine the optimal solution. Firstly, the hydraulic performance was measured using a specially designed test bench under the assumption of static-volute conditions. Then, the optimization scheme was verified in real machine experiments under the rotating-volute condition, and numerical calculations were used to assess the performance improvement due to optimization under the static- and rotating-volute conditions. The results show that the main factors affecting the pump head and efficiency are impeller outlet diameter D₂ and profile line L. The optimized pump head and efficiency are significantly higher than those of the original scheme. Furthermore, the entropy production of each flow passage component of this new type of dishwasher pump is significantly reduced after optimization. Under the static-volute condition, the scheme obtained using the range analysis displays an increase of 0.3 m in the pump head and 2.99% in pump efficiency. Under the rotating-volute condition, the optimization scheme is also effective (pump head increased by 0.54 m, and pump efficiency by 7.46%). At the same time, the passive rotation speed of the twin-volute increases from 60 rpm to 70 rpm, verifying that both the optimization method is reliable and can be used when developing and optimizing dishwasher pumps.

To improve the hydraulic performance of a new type of dishwasher pump and solve the multi-parameter optimization problem, a genetic algorithm was introduced to optimize the special design of the twin-volute structure. Six curvature radii of the twin-volute structure were defined as the optimization parameters, and 100 groups of design samples were generated based on the Latin hypercube sampling (LHS) method. The pump head and the efficiency were taken as the optimization objectives, i.e., to improve the efficiency as much as possible while ensuring that the head would not be lower than 2 m. The important parameters were identified via sensitivity analysis, and the optimization problem was solved in detail by using the multi-objective genetic algorithm (MOGA). The results showed that the external profile of the first to the fourth section of the twin-volute structure had the most significant effect on the pump head and efficiency. The response surface method (RSM) was used to select the intervals of optimization, and a comparative simulation of the pump schemes before and after optimization was performed. The head curve did not significantly change before and after optimization. By contrast, the efficiency of the dishwasher pump significantly increased, showing an increase of 2.7% under the design point. Compared with the original model, the impeller of the optimal model pump had a lower overall distribution of turbulent kinetic energy, reduced the vorticity in the twin-volute inlet area, and increased the pressure in the flow channel. Our research results confirm that the combination of RSM and MOGA can effectively solve the problem of optimization for new types of dishwashers and can provide a reference for the development of subsequent hydraulic models.