No abstract

Seawater hydraulic piston pump has been widely used in ocean engineering and become a key power component for underwater equipment due to its inherent characteristic such as energy conservation and environment friendly. As one of the most important properties of seawater hydraulic piston pump, vibration would further determine the stability, reliability and stealth of underwater equipment. In this paper, the dynamic of a novel crankshaft seawater piston pump with gearbox are analyzed theoretically, illustrating the dramatically effect of the gearbox on the vibration characteristic of the seawater hydraulic piston pump. Then, a new type crankshaft seawater hydraulic piston pump system driven by a permanent magnet synchronous motor instead of asynchronies motor is proposed in order to eliminate the gearbox and improve the vibration characteristics. In addition, the vibration characteristic of this new type crankshaft seawater hydraulic piston pump system driven by asynchronous motor and permanent magnet synchronous motor are studied and compared experimentally. The experiment results indicate that the seawater hydraulic piston pump system driven by permanent magnet synchronous motor eliminating the gearbox has lower vibration acceleration level in comparison with the pump system driven by asynchronous motor and gearbox. The vibration acceleration level can be reduced from 7dB to 4.3dB. Driving the seawater hydraulic piston pump by permanent magnet synchronous motor instead of asynchronous motor is of benefit to eliminating the gearbox and reducing the vibration excitation source. Consequently, the vibration characteristic of the seawater hydraulic piston pump system driven by a permanent magnet synchronous motor is significantly improved.

Seawater-Hydraulic-Relief-Valve (SWHRV) is a significant control component for Seawater-Hydraulic-System in underwater equipment. It makes the Seawater-Hydraulic-System operate within the relief pressure range and ensure the safety of the whole Seawater-Hydraulic-System. The performance of a SWHRV with an orifice and damping chamber is researched in this paper. The nonlinear mathematic model is built based on the operation principal and the visualization graphic simulation model is built by use of AMESim software. The simulation results indicates it has well static performances and satisfies the industrial requirements. Its rated opening pressure is 100 bar, and the releasing flowrate reaches 100 l/min when the pressure increase to 107 bar. The pressure adjusting range is between 100 bar and 205 bar. And the maximum releasing flowrate is as high as 1600 l/min at the pressure of 205 bar. Due to the damping orifice and chamber, a damping force would generate accompanying with the dynamitic motion of the spool. The opening dynamic characteristic is evidently improved though the shutting time becomes longer in comparison with the relief valve without orifice. The pressure oscillation is eliminated and it could reach the steady state ultimately. Furthermore, the effect of the damping orifice and chamber’s structure parameters on the dynamitic characteristic is analyzed. The orifice’s cross-sectional area is the main effect factor and the influence of the initial chamber volume can be neglected. Finally, the relief valve achieves well dynamic characteristic with the peak time 0.003 s and the transition time 0.015 s. The overshoot is about 20%. It has well performance with fast response, small overshoot and strong robustness.

In this paper, the cavitating flow in a venturi tube is simulated by LES combined with the ZGB cavitation model. A satisfying agreement between the numerical and experimental results is obtained. The comparison among Liutex method, vorticity method, Q method, λ ci method and Ω method has shown that Liutex method could suppress interference of shearing and preserve intensity of vortex. Thus, Liutex vortex identification method was selected to analyse the interaction between cavitation and vortex based on our numerical results. It is found that the strong vortex ring in the throat induces the cavitation ring. The ring shape cavitation cloud develops into the diffuser and separates from the wall, where small vortices occur. Forced by the re-entrant flow and small vortices, the thickness of cavities reduces, resulting in the breaking and shedding of cavities. Shedding cavities rapidly collapse, strengthening the intensity of vortices around the cavities.