Numerical Simulation Of Flow Field Characteristics Of The High-speed Craft Waterjet Propulsion

With the rapid development of high-speed vessel, more and more attention has beenpaid to waterjet propulsion because of its unique advantages. Waterjet propulsion has aspecial propulsion mode which is different from propeller propulsion. Waterjet propulsionmake use of reacting force of high-speed water erupted from boost pump, what’s more,distributing steering backing mechanism and changing the jet-flow direction couldmanipulate supporter. Increasing power, raising efficiency and reducing weight was thetrend for waterjet propulsion system. With the further research of the system, waterjetpropulsion will be more widely applied to various ships.In this paper, CFD software FLUENT was used for flow field numerical simulation ofwaterjet propulsion installed on a high-speed ship. The performance of pump、nozzle andinlet duct was calculated and analyzed.Computation model of waterjet propulsion pump in this paper was a high specificspeed mixed-flow pump. Discrete working conditions of parameter11flow values between0.05m3/s and0.4m3/s and8rotate speeds between3400r/min and4500r/min could researchstatic pressure distribution of corresponding blade and analyze possibility of cavitation. Onthe basis of parameters such as velocity, pressure and torque, power、thrust and efficiencycould be calculated in various working conditions, and the best scheme could be pickedfrom the scatter distribution, when the performance of impeller is well and proplusiveefficiency is high. Different turbulence models have different applicability in predicting theperformance of waterjet propulsion. We have got the quality sequence of the performance ofturbulence models for the waterjet propulsion of low Reynolds and rotating impeller in nearwall region. In the performance prediction, quality sequences of turbulence model wereRNG k-ε model、Realizable k-εmodel and standard k-εmodel.Numerical simulation was conducted on three-dimensional flow of waterjetpropulsion’s flat import type inlet duct, and flow field property was researched on differentIVR. From the view of quality of duct outflow and pressure distribution in duct, pressure induct greater than critical pressure value producing cavitation and avoiding cavitation shouldbe guaranteed and best IVR of duct property could be obtained. On the premise of invariantparameters, the rules of weighting average angle and efficiency was given with changedduct inclination. In allusion to duct system, impacts of9different nozzle diameters from110mm to130mm on propulsion pump efficiency, the best nozzle diameter was given. To guaranteestable flow and avoid producing eddy, adding fairy was proposed. Speed pressuredistribution was compared and analyzed in two cases：before adding fairy and after addingfairy. Meanwhile, twisted pair was used as transition curve from guide vane to nozzle. Theflow field performance was well and the thrust was obvious improved with changed nozzleshape.In this paper, CFD was used for flow field numerical simulation of waterjet propulsion,under the premise of the geometric parameters of pump, the hydrodynamic performance canbe forecast, and it could offer design reference for hydrodynamic performance and new typeof efficient waterjet propulsion.