Magnetic fluid seals for bearing assemblies of mine main ventilation fans

Abstract

The conditions of the work of main ventilation fans and their impact on the reliability of the seal bearing fan assemblies are analyzed. The application of magnetic fluid seal complexes instead of regular seals is proved. Computer simulation of nonlinear magnetic processes in the core of magnetic fluid seal (MFS) numerical finite element method using the software package Comsol by varying the gap in the range of 0.1...1.0 mm was carried out. The technique is described in detail. The calculation was performed in two stages. In the first stage distribution was calculated in static magnetic field (MF) in the active zone of the seal considering the nonlinear characteristics of magnetic circuit and the magnetic fluid in the magnetic saturation assuming M = Ms. It identifies the position of the MF boundary limited by isobars p = Ms ⋅ B == const, where B = |B| – magnetic induction vector module. In the second stage hydrodynamic processes in MF while the shaft rotates under the assumption that the magnetic fluid boundaries coincide with boundaries of liquid in static conditions were calculated. At the same time we take into account the empirical nonlinear dependence of the viscosity MF on the magnetic field and the nonlinear properties of the Navier-Stokes equations. Thus, the problem in two stages regarded as loosely coupled, which allowed to perform consistent solution. The developed mathematical model of magnetic and hydrodynamic processes occurring in the seal gap allowed to design and implement optimized design of magnetic fluid sealing complex (MFSC) for two main ventilation fans of various types considering the increasing gaps in the work area of seal. Analysis of operating experience MFSC proves the prospects of their application in the main ventilation fans (MVF). The research results are confirmed by experimental-industrial exploitation of MVF with installed with sealing complexes. MFSC tests were carried out on the mine axial fan ВОД-30M (m. Ternovskaya, Pavlograd) and centrifugal mine fan ВЦ-25 (m. Yubileinaya, Pavlograd).