| Electric propulsion systems are widely used in modern ships due to their good control performance,high propulsion efficiency,low vibration and noise,and flexible installation arrangements.The rim-drive thruster is a highly integrated new type of shaftless electric propulsion device,which has attracted much attention in the military and civilian fields since it was proposed.The motor of the rim-drive thruster is in direct contact with water,and the vibration of the motor surface will cause greater noise in the water than air.Research on the electromagnetic vibration of the rim-drive motor is beneficial to improve the acoustic stealth performance of the rim thruster.Determined the performance parameters of the rim-drive motor.Studied the technical characteristics of the rim-drive motor compared to the ordinary ones.Use the equivalent magnetic circuit method and the finite element method to iteratively design the motor,then calculate the electromagnetic characteristics of the motor.The theory of the air gap electromagnetic force wave of the motor with no load and load is deduced.Finally,the electromagnetic vibration characteristic analysis model of the rim-drive motor was established,and the electromagnetic-structure-noise coupling finite element calculation model was built.The electromagnetic vibration simulation of the designed rim motor was carried out,and the electromagnetic vibration generated by the radial and tangential electromagnetic forces was compared.The influence of the stator and rotor parameters on the electromagnetic vibration of the rim motor is analyzed.Parametric modeling of the motor is carried out,and on this basis,the influence of the stator yoke and teeth on the modal parameters,the influence of the stator slot parameters on the electromagnetic force wave,the influence of the rotor permanent magnet pole arc coefficient and the outer edge shape on the electromagnetic force wave are studied.The research results show that the parameters of the stator yoke and teeth will greatly affect the modal frequency and vibration transmission.The stator notch parameters,the permanent magnet pole arc coefficient,and the shape of the permanent magnet’s outer edge will affect the harmonic amplitude of the electromagnetic force wave.The influence of pole-slot combination on the electromagnetic vibration of the motor is studied.The relationship between the time frequency and the space order of the electromagnetic force wave under no load and load is deduced,and the finite element method is used to verify it.A series of pole slots are designed to match different rim motors.Research shows that the use of integer slot distributed windings can effectively reduce electromagnetic vibration.Aiming at the characteristics of the small thickness-todiameter ratio of the rim-drive motor,the influence of different pole-slot combination on the electromagnetic vibration under the same yoke thickness is studied.Research shows that the vibration caused by high-order electromagnetic force waves cannot be ignored,and the vibration caused by the 12th-order electromagnetic force wave is equivalent to the zero-order force wave.The law of noise propagation in different media is studied.The similarities and differences of noise propagation in sea water and air are compared.An underwater sound insulation device with a cavity structure is designed,which has a significant sound insulation effect on the rim motor. |
