The axial-flow pump is a widely used piece of general machinery which consumes large amounts of energy. In this study, an axial-flow pump with the specific speed of 536 is firstly designed and experimentally measured; then, the orthogonal method is employed to conduct the energy performance optimization. Five optimization parameters, including hub control point, hub stagger angle, shroud stagger angle, camber angle and centroid position were set with four levels. Sixteen individual pumps were designed according to the orthogonal method; then, a numerical simulation was implemented to obtain the energy performance and flow pattern. Results showed that the shroud stagger angle has the maximum influence on the pump head and efficiency, and the hub stagger angle and camber angle are also very important. At a design point of flow rate 70 kg/s, the efficiency of the optimal pump is 86.29%, which improved by 2.05% in comparison with the baseline pump. The pressure gradient of the optimal pump from blade inlet to outlet becomes more fluent than that of baseline pump, and the low-velocity region of the optimal pump at the blade head shrinks, compared to that of the baseline pump.

Compared with traditional propellers, the pump jet has the characteristics of low noise, large thrust, and high efficiency, which is widely used in underwater ships, unmanned underwater vehicles, and underwater rescue equipment. It is difficult to design and evaluate the performance of a pump jet because of its complex structure and the many changes in its component parameters. In this paper, high-efficiency pump jet design and optimization methods are presented. Based on the center-of-gravity accumulation line control, a design method is proposed to design the pump jet rotor. The thrust performance and hydraulic performance of the pump jet are obtained through numerical simulation, and the influence of various parameters on performance is studied. Finally, based on a single-factor analysis and orthogonal optimization, a multi-parameter orthogonal optimization of pump jet was carried out. The angle of attack, chord length, camber angle, and number of blades were selected to establish a four-factor and three-level orthogonal table. The thrust efficiency was taken as the optimization goal. Compared to the original pump jet, the optimized pump jet thrust coefficient and thrust efficiency are significantly improved at various speed conditions, with the maximum thrust efficiency increased by 7.23%, meeting the design requirements. This research provides a theoretical basis and technical guidance for the structural optimization design of a pump jet propulsion system.