Abstract
In order to investigate the transient hydrodynamic characteristics of water-jet propulsion with a screw mixed pump during the startup period and to overcome the difficulties in measuring the transient process parameters over a very short period of time, a method based on a flume experiment combined with computational fluid dynamics (CFD) is proposed. The thrust and torque of the pump-jet propulsion according to mooring status at different rotational speeds were measured by the test, which provided a group of data for the boundary and initial conditions of the numerical calculation of the user-defined function (UDF). Consecutive changes in the parameters of the water-jet propulsion dynamics can be captured from the numerical simulation of the startup process with the UDF. Thus, the transient hydrodynamic characteristics of water-jet propulsion according to time or rotation speed were obtained. The results show that the relationship between the thrust or torque of the water-jet propeller and pump rotational speed is close to the quadratic functions. The energy characteristic parameters of screw mixed water-jet pump, such as the flow rate, head, shaft power, and efficiency, rapidly increase and decrease and then remain relatively stable.
Highlights
Tsukamoto et al [4, 5] found that the dimensionless head and flow rate began to decrease from initially large values, reaching steady-state values after a certain time below the steady-state curve during the centrifugal pump’s startup processes
Li et al [7] established a closed circulatory system with the centrifugal pump to study the transient characteristics during the startup period, which avoided the calculation error caused by the uncertainty regarding the boundary conditions of the inlet and outlet
Tanaka and Tsukamoto [8,9,10] studied cavitation in centrifugal pumps during the startup period by flow field visualization and found that the rapidly changing pressure and flow rate were related to the cavitation behavior of the pump
Summary
As an advanced propulsion mode, thrust is generated by water-jet propulsion with a screw mixed pump relying mostly on the difference in momentum between the inlet and outlet water flows [1, 2]. is method has many advantages over traditional propeller propulsion, such as higher efficiency, lower noise, more stable operation, and better resistance to cavitation, and it has been widely used in high-performance warships and new submarines. e thrust and power of waterjet propulsion with a screw mixed pump are usually altered by adjusting the rotational speed and are scarcely affected by the sailing speed. e rotational speed of the impeller rapidly reaches the designated value during the startup period, and the flow pattern changes from laminar to complex turbulent flow causing a rapid fluctuation in pressure, a high-water flow impact, and a transient high load on the blade which all affect the stability and longevity of the pump. erefore, it is of great significance to investigate the transient characteristics of this type of water-jet propulsion during the startup period. Wang et al [13, 14] set up a model to analyze the startup process of the mixed-flow pump based on the internal characteristics of the pump and the one-dimensional unsteady motion equations of the pipeline. Li et al [15] analyzed the starting characteristics of the mixed-flow pump based on a quasi-steady-state assumption, which provides a new idea for revealing the transient internal characteristics of the startup process of the mixed-flow pump. Li et al [17] found that in the startup process of the mixed-flow pump, the flow stabilized in the impeller, the scale of vortex decreased gradually as the rotating speed approached the rated speed, and the transient effect disappeared. The control of impeller speed realized by the userdefined function (UDF), in a numerical simulation, and a technique for controlling the frequency, in an experiment to reveal the transient hydrodynamic coefficients during the startup period of the water-jet pump, are described
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
