Loss Analysis And Fluid-thermal Coupling Study Of Shaftless Flange Propeller

Shaftless rim thruster is a new type of underwater propulsion equipment,the rotor directly drives the propeller rotation to generate propulsion,with the advantages of simple structure,lightweight,low vibration and noise,etc.,in the field of underwater propulsion has broad application prospects.Due to the limited space of the shaftless rim thruster duct,the small size of the motor and the high power density,there is a strong electromagnetic-fluid-thermal coupling inside its operation and it directly determines the effective operation of the thruster.Therefore,revealing the internal coupling of the shaftless rim thruster and clarifying the key factors of temperature rise are the keys to thruster design and performance improvement.In this paper,the finite element method(FEM)and the finite volume method(FVM)are combined to establish an integrated motor electromagnetic field finite element calculation model and a thruster flow-thermal coupling calculation model to simulate and analyze the electromagnetic-flow-thermal coupling problem of the shaftless rim thruster.The main research contents are as follows:(1)The research progress of shaftless rim thruster and the research status of motor electromagnetic loss and thruster gap runner are briefly described.A 2.2k W shaftless rim thruster integrated motor is designed for the characteristics of the shaftless rim thruster,and its performance is analyzed by finite element analysis.The Joule-Flute law and the Bertotti iron consumption separation model were used to calculate the copper and iron consumption of the stator of the 2.2k W integrated motor,and the eddy current loss of the sheath was analyzed using the two-dimensional finite element method.(2)The modeling of a shaftless rim thruster containing key components such as propellers and ducts was carried out.A computational model of the fluid-thermal coupling of a 2.2k W shaftless rim thruster was established based on the finite volume method,and studies related to the division of the computational domain,mesh independence,and selection of simulation methods were carried out.To verify the accuracy of the coupled calculation model,the hydrodynamic performance and the fluid-thermal coupling simulation were verified by using the ducted propeller and the glued stator module as the research objects respectively.(3)Based on the computational model established for the fluid-thermal coupling of the 2.2k W shaftless rim thruster,a study of the temperature field of the shaftless rim thruster with different sheath materials and different feed coefficients was carried out using the integrated motor losses calculated by the finite element method as the heat source.Combining the torque characteristics of the integrated motor and the propeller load characteristics,the formulae for calculating the losses of the integrated motor with different propeller speeds and different gap sizes are derived,and the temperature rise and heat dissipation of the shaftless rim thruster under the corresponding operating conditions are studied using the calculated electromagnetic losses as the heat source.The results show that: the influence of external water flow on the propeller gap water flow is small,and the improvement effect on heat dissipation is not significant,and the propeller speed and the size of the propeller gap size will affect the propeller heat dissipation,and the design scheme should be reasonably selected to increase the propeller thermal conductivity and convective heat transfer coefficient to improve the heat dissipation efficiency.(4)Around the problem of high stator end temperature of the shaftless rim thruster,a "concave" gap runner heat dissipation structure is proposed.By comparing the analysis with the traditional gap runner structure,the "concave" gap runner heat dissipation structure and the traditional gap runner have significantly reduced the maximum temperature of the thruster compared with the straight and stepped gap runner structure under the condition that the friction losses are comparable,which shows a better heat dissipation effect.