ANALYSIS OF INFLUENCE OF SHORT MAGNETORHEOLOGICAL DAMPING ELEMENTS ON VIBRATIONS ATTENUATION OF RIGID ROTORS

Abstract eng:
A frequently used technological solution for reducing lateral vibrations of rotating machines as a result of their unbalance consists in adding damping devices to the rotor supports. To achieve their optimum performance their damping effect must be adaptable to the current operating conditions. This is offered by magnetorheological squeeze film dampers. Magnetorheological oils belong to the class of liquids with a yielding shear stress. In the developed mathematical model of a short magnetorheological squeeze film damper the lubricant is represented by Bingham material. Then the pressure distribution in the lubricating layer is governed by the Reynolds equation adapted for Bingham fluid. The yielding shear stress depends on magnetic induction. Its stationary value can be approximated by a power function and its dependence on its time history in the past (characterized by a time constant) by a convolution integral that is consequently transformed to a linear differential equation of the first order. Efficiency of the studied magnetorheological damper was investigated by means of computational simulations. The obtained results show that the rising magnetic flux passing through the layer of the magnetorheological oil arrives at increasing attenuation of the rotor vibrations. On the other hand the damping effect is going down with increasing magnitude of the delayed yielding time constant.

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