Abstract：To study the performance of twostage contrarotating axial waterjet propulsion pump under different rotational speed ratios, the fluid flows in a waterjet pump are simulated under different working conditions by using computational fluid dynamics(CFD) method, and the relationship between the performance and speed ratio is established, further the flow structure and turbulent energy dissipation rate are analyzed. The results show that the performance of the pump depends largely on rotational speed ratio. Through comparison, the optimum speed ratio for the best efficiency is obtained at different flow rates. When a flow rate is less than 1.0Qd, the optimum speed ratio can be realized by controlling the front impeller speed. When a flow rate is higher than 1.0Qd, however, the optimum speed ratio can be achieved by altering the rear impeller speed. Through an analysis of the velocity triangle and internal flow field at 0.9Qd, it is identified that the reduction of the front impeller speed is helpful to low angle of attack experienced by the front impeller, causing improved internal flow field and decreased hydraulic losses. These results confirm the method of speed control for the contrarotating axialflow waterjet pump is feasible.
