Study of longitudinal vibrations of stab knife refiners

The subject of research is the longitudinal vibrations of stab knife refiners. A model of the fibrous layer between the rotor and stator is developed. It is shown that it is advisable to use the Maxwell-Thomson model for liquid friction of the rotor and stator, and the Hooke elastic model for boundary friction. The formula for determining the dynamic stiffness of the fibrous layer is obtained. Dynamic and mathematical models of the refiner in the longitudinal direction are developed. The mathematical model is a system of linear differential equations with periodically varying coefficients (Mathieu-Hill equations). A method for calculating the amplitude of oscillations of the refiner rotor and stator is developed. According to this technique, Andritz 54-60-1c stab refiner was designed. Oscillation parameters of the refiner rotor and stator are determined theoretically and experimentally. The stator oscillation amplitude is 1.6–2.3 times smaller than the rotor oscillation one. In case of boundary friction, the amplitude of oscillations of the stator and rotor increases by 2–3 times in comparison with liquid friction. The oscillation amplitude of the rotor and stator in the longitudinal direction is comparable with the gap between these elements. Therefore, it is recommended while designing refiners, to develop methods and means of vibration protection, and during operation, to prevent boundary friction between headsets. The developed calculation procedure can be used in other industries, for example, mining and metallurgy.