Start-up test of ferrofluid seal based on rheometer

Sealing is one of the most successful applications of ferrofluid. However, the seal often has a sudden change in speed during the start-up process, which causes unstable vibration of the system and may result in accidental failure of the seal. In this work, we designed a ferrofluid seal test equipment based on rheometer to study the start-up characteristics of ferrofluid seal. We scan the rotational speed of the ferrofluid seal to determine the torque range of the fixed torque start, and found that the magnetic field strength and the number of pole teeth will affect the torque value and the slope of the curve. We experimentally analyzed three start-up modes of ferrofluid seal. During the start-up process at a fixed rotating speed, the torque fluctuates periodically, and the fluctuation amplitude increases with the increase of magnetic field strength or the number of pole teeth. During the start-up process of fixed torque, the rotating speed fluctuates periodically, and the fluctuation amplitude declines with the increase of torque. In the process of variable torque start-up, as the number of torque changes increases, the rotation speed increases more slowly and the fluctuation range is smaller, which leads to a more stable start-up of the ferrofluid seal. Ultimately, we believe that variable torque starting will be used to promote the application of ferrofluid seals in high-end precision applications.