考虑气隙变化的高速电主轴热特性仿真

Simulation of thermal characteristics of high speed spindle considering air gap variation

为了解决电主轴高速旋转时结构变化引起的自身热特性改变的问题,提出离心膨胀和热膨胀会影响电主轴内定、转子间对流换热的观点.基于弹性力学理论,计算电主轴定、转子受离心力和热载荷而产生的径向膨胀量及由此导致的气隙变化量;根据对流换热理论得出离心力影响下泰勒数随转速和气隙长度的变化规律以及对流换热系数的变化规律.计算发现,气隙长度随定、转子的膨胀而减小,该减小量占设计值的37.7%;泰勒数随转速升高而增大,随气隙长度增大而减小;对流换热系数随气隙长度增加而降低,使得定、转子间传热受到抑制.结果表明,若能提高气隙间对流换热系数,适当提升油水冷却功率,能够大幅度降低主轴转子温升和热位移,提高加工精度.

A viewpoint on the centrifugal expansion and thermal expansion which would affect the convection heat transfer between stator and rotor of high speed spindle was proposed to solve the problem that the thermal characteristics caused by structure variation of high speed spindle would be changed under high rotation speed.Based on the theory of elastic mechanics,radical expansion and air gap changes which caused by the radical expansion were calculated considering the two expansions acting on the stator and rotor of spindle.Variation rules of air gap and convection heat transfer coefficient that affected by the centrifugal force were obtained according to the convection heat transfer theory.The calculation results show that the air gap length decreases with the expansion of the rotor,and the reduction is 37.7% of the design value.The Taylor number increases with the increase of the rotating speed,while decreases with the increase of the air gap length.The heat transfer coefficient of air gap decreases with the increase of air gap length,so that the heat transfer between the stator and rotor is restrained.Results show that the temperature rises and thermal displacement can be significantly reduced if the convection heat transfer coefficient and the cooling power can be properly promoted,then the machining accuracy can be improved.