| In order to enhance the combat capability of torpedoes,various countries have equipped new propulsion devices——pump-jet thrusters.The thruster can not only effectively reduce the radiation noise of the thruster,but also maintain extremely high propulsion efficiency,so that the endurance,rapidity and stealth of the torpedo can be significantly improved.The high efficiency and low noise of the impeller is due to its unique structure.The effective combination of stator and rotor can greatly enhance the work efficiency of the impeller,and the duct acts as a noise shield.In order to further explore the working principle,hydrodynamic characteristics and design methods of the pumpjet,the research works are carried out including the hydrodynamic performance prediction method,fluid simulation,the hydrodynamic prediction method of the integration of torpedo and pumpjet,the design method of pumpjet blades,the optimization design method of duct,and the design method of pumpjet under the effect wake condition based lifting line/lifting surface design principle of propeller,surface element method and CFD method.As follows:1.The paper adoped surface element method to establish model of steady hydrodynamic interference model.Pumpjet is divided into rotor propulsor hub and stator pipe system,the intersystem interference is considered by induced velocity.For the geometrical shape design problem of the rotor and stator of the torpedo pumpjet,presenting grid division method based on cone surface.Then this method is used to predict the hydrodynamic value of the pre-stator pumpjet propulsor,the results are compared with the experimental results,the research results show that the simulation method of pumpjet propulsor based on surface element method,can be effectively on the flow field numerical calculation of the pre-stator pumpjet propulsor,but there are large error exist for the rear stator pumpjet.This is caused by the lake of consideration of the tip gap vortex flow of pumpjet.2.The CFD method is used for the correlational research of pumpjet to explore the working mechanism and provide the reliable comparison and verification method with the subsequent potential flow methods.The accuracy of the CFD calculation method is studied by analyzing the influent of grid uncertainty and grid stype on the calculation results using the test result of standard open water propeller.Based on the research,the CFD method is used for prediction of thrust performance of the pre-stator pumpjet in open water.The calculation results are coincide with test result.And the same computing method is used for the performance predicting and flow field characteristics of rear stator pumpjet.Finally the numerical simulation of plate clearance flow is carried out,and the motion trajectory of the gap vortex structure and the flow field pressure characteristics in the gap region are preliminarily studied.3.According to the simulation of internal flow,a tip leakage vortex model for flat top blade is proposed to improve the computational accuracy of the potential flow prediction method.And the numerical model of pumpjet performance prediction is also improved.By comparing the results of pressure,circulation volume and propulsion performance,it is found that the vortex numerical model can effectively simulate the influence of the leakage vortex on the surrounding and downstream stator.In addition the influence degree of the tip vortex is related to the inlet velocity coefficient and the string value of the rotor tip.When the influence of tip vortex is considered,the overall circulation distribution of rotor blades and the tip load are closer to the actual situation and the performance curve is in good agreement with the viscous flow.Finally,this method is used to predict the hydrodynamic value of the pre-stator pumpjet propulsor,the results are compared with the experimental results,results show that the pumpjet propulsor based on surface element method,numerical simulation method,can be on the front and rear of the stator of the stator propulsor pumpjet flow field numerical calculation effectively,and get high precision of the forecast results of hydrodynamic performance.At the beginning of pumpjet design,the main scale of the duct should be selected.In this paper the variable parameter analysis method is used,attack angle,camber degree and clearance height of the duct were systematically studied.It has been studied in depth from the performance curve,velocity distribution and pressure distribution the geometry changes impaction,and given the recommended values ranges.4.According to the structure characteristics of the torpedo pumpjet propulsor to gain thrust through momentum change,this paper is aimed at the boundary condition of the inclined flow field,it gives the method of selecting the profile of pumpjet rotor and stator blade based on the propulsor design principle,by summarizing the performance difference between the pumpjet rotor and propulsor,as well as the working principle of stator,the rotor and stator blade circulation distribution is determined respectively.Then based on the duct parameters research,the main parameters of the ducts,the diameter of the blades and the diameter of the hub were studied.Finally,based on the design method of the pumpjet blade and the prediction procedure of the hydraulic surface element method,on the basis of MK48 torpedo design requirements and conditions with a full-scale pumpjet design,and evaluate the blade circulation distribution and pressure distribution,wake field characteristics and open water performance.The evaluation results show that,under the given rotate speed and navigational speed,the pumpjet design scheme satisfies the host power requirements,and the stator can balance the rotor torque and recover the rotating potential energy of the rotor.5.For design the practical flow field in the rear-end environment of the pumpjet propulsor,this paper is built on potential flow theory with lifting and non-lifting algorithm,Combining with the induced velocity iteration method,simulating the numerically modeling between the torpedo body and the pumpjet.With the model of MK48 naked body as the model,the nominal coupled flow field and the effective wake flow field in the pumpjet surface are calculated respectively.Using stator balancing rotor torque and recovering rotor wake rotation potential energy to improve work efficiency.6.Finally,the numerical calculation method of the integration system of torpedo and pumpjet is used to combine the pumpjet design method with the pumpjet design.On the basis of the practical design scheme,the duct optimized design.This paper presents a design method to optimize the design of pumpjet duct profile with a change of axial force coefficient which based on the design principle of three-dimensional airfoil surface element method.The results show that the effective flow design scheme takes into consideration both the wake and the cavitation performance of the blades,and reduces the design of the efficiency relative open water.However,after the optimized design of the duct,the duct resistance decreased significantly,and the overall efficiency of thruster increased.And the high-speed adaptability was enhanced,and the final design efficiency reached 0.84. |
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