弹性箔片轴承-盘式永磁电机转子系统轴向冲击响应

轴向磁通永磁(Axial Flux Permanent Magnet,AFPM)电机在给转子输出周向电磁转矩的同时,还作为一种“磁轴承”,与弹性箔片轴承(Gas Foil Bearings,GFBs)并联工作.当GFBs支承的单定子单转子AFPM电机转速发生突变时(如加、减速),叶轮或者透平会产生一个瞬时轴向力.为揭示此轴向冲击对转子系统振动的影响机理,针对采用2个径向GFBs和1个轴向GFB支承的单定子单转子AFPM电机,建立了系统的刚性转子动力学方程,计入了永磁体的轴向吸力、径向回复力以及轴向GFB的推力对转子振动的影响.计算显示：轴向冲击对横向振动的影响非常小,箔片结构刚度的非线性效应会对转子振荡幅值和时间均产生影响,永磁体的负刚度绝对值越大,轴向振幅越大.在设计时,要注意永磁轴承刚度、箔片结构刚度和结构阻尼的合理匹配,以保证转子在轴向冲击下的轴向振荡时间和振幅均不超过允许值.

Axial impulse response of a rotor system composed of gas foil bearing and axial flux permanent magnet machine

The axial flux permanent magnet (AFPM) motor severs as a passive magnetic bearing and works in parallel with the gas foil bearings (GFBs), while it outputs a circumferential electromagnetic torque to the rotor system. When the single stator single rotor AFPM motor supproted by GFBs suffers from a sudden change of rotating speed, the impeller or turbine generates a transient axial force acting noto the rotor. To reveal the effect of the axial shock on the vibration of the rotor system, a rigid rotor dynamic model of the single stator-single rotor AFPM motor supported by 2 radial GFBs and 1 axial GFB was established, considering the axial attraction force, radial restoring force of the PM and the thrust of the axial GFB. Results show that the influence of the axial impact on lateral vibration is very small, the nonlinear stiffness of the foil affects both the amplitude and time of rotor oscillation, and the axial amplitude increases with the increase in the absolute value of PM negative stiffness. A reasonable matching among PM stiffness, structural stiffness and damping of the foil is important to ensure that the time and amplitude of rotor oscillation under the axial impact do not exceed the allowable value.