Transient Characteristics of Start-up Process of an Axial Flow Water-jet Propeller

The propulsion performance of an axial flow water-jet propeller during start-up process is improved to study its transient characteristics and self-priming performance. The SST k-ω turbulence model, Zwart cavitation model and Free Surface model are used to study the start-up process of the proposed axial flow water-jet propeller under the framework of Reynolds-averaged Navier-Stokes equation. The effects of start-up time and waterline height on the transient characteristics of water-jet propeller were analyzed. The steady-state numerical method was verified based on the experimental data of water-jet pump, which is in good agreement with the numerical results. The results indicate that the start-up process show significant transient characteristics. The flow rate and the head reach the stable state later than the rotation speed, and the lag becomes more severe as the start-up time decreases. Cavitation occurs on the suction surface around the leading edge of the blade when the rotation speed is 0.6 times higher than the designed rotation speed. The dimensionless cavity area increases with the increase in the rotation speed. At the same rotation speed, the dimensionless cavity aera is negatively correlated with the start-up time, while the working capacity of the blade is positively correlated with the start-up time. When the waterline height is greater than or equal to 0.15 times larger than the impeller diameter with the center line of the pump shaft as zero reference line, the gas inside the water-jet propeller can be completely discharged in a short time, and the lag of flow rate and head becomes more severe as the waterline height decreases. © 2021, Editorial Board of Acta Armamentarii. All right reserved.