| The magnetic coupling is composed of three parts:the inner rotor,the outer rotor and the isolation sleeve.It is a new type of coupling that achieves the effect of non-contact transmission and static sealing through the action of magnetic force.Applying it to the natural gas pressure energy power generation device can effectively solve the sealing safety problem of natural gas.However,heating caused by eddy current effect is an unavoidable problem when using magnetic coupling.When the temperature of permanent magnet exceeds the allowable range,it will affect the normal use of magnetic coupling.In view of the above problems,this paper takes the magnetic coupling applied in the natural gas pressure energy power generation device as the research object,and conducts in-depth research from three aspects:magnetic field characteristics,eddy current loss,temperature rise and heat dissipation under the action of eddy current.By establishing a two-dimensional analytical model of the magnetic field of the magnetic coupling,the analytical formula of the magnetic flux density distribution of the air-gap magnetic field of the magnetic coupling is deduced.The three-dimensional magnetic field finite element model of the magnetic coupling is constructed,the periodic distribution characteristics of the air gap magnetic field of the magnetic coupling are obtained,and the axial difference of the value and direction distribution of the air gap magnetic density under the influence of the end effect is analyzed.The three-dimensional eddy current loss finite element calculation model of the magnetic coupling is established,and the instantaneous induced current and eddy current loss distribution characteristics on the isolation sleeve are analyzed through transient calculation.The influence of angle difference,rotational speed,coupling situation,center radius of spacer sleeve,wall thickness,and material conductivity on eddy current loss is studied in depth.From the perspective of reducing eddy current loss,reasonable suggestions are put forward for the selection of magnetic couplings and the setting of operating conditions.The heat-fluid interaction model of the magnetic coupling and its flow field is established,and the eddy current loss on the isolation sleeve is loaded into the heat-fluid interaction model as a heat source.The temperature distribution characteristics of the magnetic coupling under rated operating conditions are obtained by simulation,and the flow state of the flow field around the magnetic coupling and the heat transfer characteristics on the outer wall of the isolation sleeve are further analyzed.Aiming at the problem that the air in the air gap is difficult to circulate in the axial direction and the internal magnetic temperature is close to the maximum allowable working temperature,the heat dissipation structure of the magnetic coupling is improved by changing the eccentricity of the heat dissipation holes on the outer rotor,increasing the number of heat dissipation holes and increasing the aperture diameter.Thereby,,the maximum convection heat transfer coefficient of the outer wall of the isolation sleeve is increased from 23.6 W/(m~2·℃)to 61.7 W/(m~2·℃),and the temperature of the inner magnet in the magnetic coupling is kept below 50.9℃.The strength of the isolation sleeve and the outer rotor after the improved heat dissipation structure was checked,and the deformation amount and stress of the two did not exceed the allowable range,meeting the requirements for use. |
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