Study On Dynamic Characteristics Of Small Flow Area Of ​​Water Jet Propulsion Pump Based On Fluid - Solid Coupling

Waterjet pump has gained tremendous development in the last 20 years especially in the high-speed performance ship, amphibious vehicles and some shallow water operations. The water jet propulsion system with the core of the jet propulsion pump has better efficiency, anti-cavitation performance, convenient maneuverability and operational advantages, less resistance and able to adapt to constantly changing operating conditions and littler underwater acoustic radiation so that the water jet propulsion system has been applied in many developed countries. In this century, the waterjet technology has been widely implemented with the gradual growth of demand and advancement and development of related key technology in our country. However, there will be vibration, noise caused by the instability of the flow in the small flow rate condition in the pump startup process in the high-speed operation of the boat. The life of the service and the operating efficiency will be reduced and the national economy will be lost largely caused by the fatigue failure resulted in the unsteady flow. Thus, it is significance of the design and optimization of the structure to analyze the flow field and static structural of the water jet propulsion pump.The propulsion pump models produced by the Wartsila Company were researched under the support of the research of Jiangsu Province prospective joint research project, the National Natural Science Foundation of China.Work of 3D modeling including structure model(impeller, fairing cap, guide vane and pump axis) and fluid model( inlet, impeller, guide vane and outlet) was completed with UG. Meshing of fluid was completed with software ICEM CFD and meshing of structure is completed with software WORKBENCH. Then, simulated the steady flow of fluid domain under various working condition with turbulence model LES.The pressure pulsation of different monitoring points was conducted time domain and frequency domain analysis. The results showed that the main frequency was blade passing frequency at the inlet of the impeller, the pressure pulsation was attenuated more quickly and the amplitude of the low-frequency increased with the monitoring points near the wall. The range of the low-frequency increased and the main frequency shifted to the low-frequency. The random pulsation occupied a major position and the amplitude decreased significantly at the outlet of the guide vane.The pressure from the inlet to the outlet, from the hub to the tip increased gradually which the pressure gradient was distributed along the radial distribution seen from the internal flow field analysis. The high-pressure region moved from the upper portion of the blade to the outlet. There existed a lot of eddy swirls which the vortex scale increased and then decreased from the inlet to the outlet near the suction surface of the guide vanes. The vortex core was attached to the smallest pressure fluctuation in the suction surface intermediate high leaf area and the unsteady vortex decreased significantly with the increased flow. The axial force decreased with the increased flow before the hump area, however, the axial force increased with the increased flow while the pump was run in the hump area condition. The presented relationship curve between head and the axial force was nearly linear.Calculate the effects of fluid on structure based on FSI and analysis the deformation and strength of key components of structure. The result showed that the maximum deformation appears at tip of impeller inlet which the deformation increased from the hub to the tip. The blade radial deformation decreased and then increased from the hub to the tip which the radial deformation was far less than the total deformation. The regularity and the value of circumferential deformation was similar with the total deformation. High stress exists where is close to hub and inlet of the working face. The structure has been significant stress stiffening by the various forces worked on the structure.The hump area has been improved significantly and the low-frequency pressure pulsation has been weakened by using J-Groove. The hydraulic performance was improved with the increased parameter d and n. The efficiency of the pump has an optimal value with the increased parameter.