Study On Design Method Of Pump Jet Thruster For Underwater Vehicles

As one of the main radiation noise of submarine, propeller noise is the importantindicator of submarine performance. The studies show that pump jet thruster has good noiseperformance at high speed by applying decelerating duct to improve cavitation performanceand using stators to increase efficiency. However, the design method of pump jet thruster is ina fledging period in domestic region. According to the characteristics of pump jet thruster, thepump jet thruster is designed by circumfluence theory combined with surface panel methodand lifting design method of axial flow pump. The main content of this paper includes:(1) The optimum circulation distribution calculation of propeller with appendage interferencein axial wake and circumferential wake is studied based on variational calculus. Accordingto the basic equation of axial flow pump and the characteristics of ducted propeller, thelifting design method of ducted propeller is established.(2) The steady and unsteady performance prediction method of propeller-appendages systembased on surface panel method is studied. The accuracies of direct method, potentialiteration and velocity iteration in the steady hydrodynamic performance prediction areanalyzed. In the unsteady calculation, the interaction between propeller and appendages isconsidered by induced velocity of every time step after propeller and appendagesperformance convergence. The availability of the method is verified by a ducted propellerperformance calculation. The influence of wake model of surface panel method oncalculation result is analyzed. The propeller wake model in the thruster assembly isimproved to raise calculation accuracy, and the availability of the wake modified methodis verified.(3) The steady and unsteady hydrodynamic performance prediction of pump jet thruster isresearched based on surface panel method. The calculation amount of pump jet thrusterperformance in un-uniform flow is largely reduced by improving modeling method ofstators. The pump jet thruster performance varying with stator position, stator size, statorangle, duct length and so on are calculated and analyzed.(4) The lifting line theory combined with surface panel method and pump lifting designmethod is established to design pump jet thruster. In the design, the optimum circulation distribution of rotor is solved by variational method; rotor section is designed by liftingdesign method, and the flow field and performance are calculated by surface panel method.The method presented is applied to a ducted propeller and a pump jet thruster design, andthe performances of designed results are further verified by CFD.(5) The pressure distribution of pump jet thruster computed through surface panel method isinput to the FW-H time domain equation as acoustic source to predict the low frequencydiscrete noise. The contribution on sound pressure from duct, stators, rotor in pump jetthruster with pre-swirl stators and post-swirl stators is analyzed, and the non-cavitationnoise characteristic is studied.The calculation results show that, the modified wake model presented can improve thecomputation precision of ducted propeller and pump jet thruster; the unsteady performanceprediction of pump jet thruster and the iteration method to calculate optimum circulationdistribution of propeller in thruster assembly are reliable. By designing pump jet thruster for asuppositional submarine, it turns out that, the performance prediction method of pump jetthruster is reliable; the designed results have higher efficiency and can satisfy design requestwell; the flow field of designed pump jet thruster is similar with axial flow pump.