磁流体密封在水轮机主轴中的应用

为了解决目前常用的水轮机主轴密封装置易磨损、泄漏量大的问题,在水轮机主轴上采用磁流体密封技术.该密封技术具有无刚性接触,无磨损,可自行修复,寿命长等优点,选择适合密封水介质的油基四氧化三铁磁流体作为密封材料,磁性能高且价格低廉的钕铁硼永磁材料提供外磁场,并使用电磁场分析软件进行仿真计算.仿真结果表明:轴向密封靠近转轴处,径向密封靠近导磁体处,密封能力最差,最易失效;齿形、密封间隙等结构参数对密封性能影响较大,且在一定的数值范围内密封能力较强. 结合水轮机主轴密封的特点,设计出适合水轮机主轴的轴向与径向密封组合的矩形齿磁流体密封装置,轴向密封总级数为48级,径向密封总级数为20~24级,总的密封压差Δp>0.5 MPa.

Application of magnetic fluid seal in hydraulic turbine shaft

At present the main shaft sealing device of hydraulic turbine is easy to wear and tear, and the leakage is great. In order to solve it, the magnetic fluid seal with the advantages of no contact, no wear, self-healing, long life and so on would be used on the turbine shaft. The oil-based oxide ferromagnetic fluid suitable for sealing water medium was used as sealing material and NdFeB permanent magnet material with high magnetic properties and low prices was used to provide an external magnetic field.Through simulation analysis by using analysis software of electromagnetic field, it is shown that the seal ability is the worst and first to seal fail in the places close to the shaft side in the axial seal and close to the magnetic conductor side in the radial seal, the parameters of the sealing device such as tooth and seal gap have great effect on the sealing performance which is stronger in a certain range of values of tooth and gap.Based on the result above and the characteristics of the turbine shaft seal, the magnetic fluid sealing device with rectangle tooth combined of axial and radial was designed for turbine, while number of axial total poles is 48, the radial is 20-24, the sealing pressures Δp>0.5 MPa.