大轴径离心压缩机磁流体密封传热特性研究

高温会降低磁流体饱和磁化强度，造成永磁铁退磁，影响磁流体密封装置的可靠性及稳定性。为探讨磁流体密封装置传热特性，以大轴径离心压缩机磁流体密封为研究对象，同时考虑磁流体摩擦热和轴承摩擦热对磁流体密封装置传热特性的影响，利用有限元数值计算与磁流体、轴承摩擦功耗理论分析相结合的方法，研究磁流体密封装置温度分布规律，分析齿宽、密封间隙和转速对永磁铁和磁流体最高稳态温度的影响，并确定相关工况所需冷却液质量流率。结果表明：由于轴径尺寸较大，表面线速度高，磁流体黏性摩擦热及轴承摩擦热对密封装置传热特性有显著影响，在无冷却工况下，密封装置最高温度超过磁流体和永磁铁的极限使用温度，需通过强制对流换热的方式进行降温处理；永磁铁及磁流体最高稳态温度随着齿宽增加而升高，随着密封间隙增加而减小；随着转速的增加，永磁铁及磁流体最高稳态温度升高，且转速越大，相同转速梯度差之间的温度差越大。

Study of Heat Transfer Characteristics of Magnetic Fluid Seal in Large Shaft Diameter Centrifugal Compressor

High temperature will reduce the saturation magnetization strength of the magnetic fluid and cause demagnetization of the permanent magnet,which affects the reliability and stability of the magnetic fluid seal device.In order to explore the heat transfer characteristics of the magnetic fluid seal device,the magnetic fluid seal of large shaft diameter centrifugal compressor was used as the research object,the influence of magnetic fluid friction heat and bearing friction heat on the heat transfer characteristics of magnetic fluid sealing devices was considered simultaneously,and the method of combining finite element numerical calculation with theoretical analysis of magnetic fluid and bearing frictional power consumption was used to study the temperature distribution law of the seal device.The effect of tooth width,seal gap and rotational speed on the maximum steady-state temperature of permanent magnet and magnetic fluid was analyzed,and the required coolant mass flow rate for relevant working conditions was determined.The results show that due to the large shaft diameter and high surface linear velocity of the centrifugal compressor,the viscous frictional heat of the magnetic fluid and the frictional heat of the bearing have a significant effect on the heat transfer characteristics of the seal device.The maximum temperature of the seal device exceeds the ultimate operating temperature of the magnetic fluid and the permanent magnet under the non-cooling condition,and cooling treatment needs to be carried out through convection heat transfer.The maximum steady-state temperature of the permanent magnet and magnetic fluid increases with the increase of tooth width,and decreases with the increase of seal gap.The maximum steady-state temperature of the permanent magnet and magnetic fluid increases with increase of rotational speed,and the higher the speed,the greater the temperature difference between the same speed gradient.