Specialty of rotor’s drive mechanism oscillations
Authors: V. S. Loveikin, Yu. V. Chovnyuk, A. P. Lyashko
Number of views: 281
Purpose. Scientific work is devoted to study the influence of dynamic coefficients of bearings segment (coefficients of resistance and recirculating power) on stability and subharmonics self-oscillating components of the rotor vibration in unstable region of rotational speeds. Methodology. The study is based on the methods: the theory of vibrations of mechanical systems with lumped parameters; Lagrange functions; linear algebra. Findings. The researchers made: a) justification of the discrete two-mass model of an unbalanced rotor, which takes into account the influence of rotation on dynamic coefficients; b) analysis and improvement of methods for engineering analysis of stability and parameter subharmonic self-oscillations in the unstable range of frequencies of rotation of the rotor; c) installation and classification of the main rotor causes of vibrations constructive or those arising in the manufacture, assembly and operation of the machine, and on the other hand, rotary systems specific for non-conservative forces, that lead under certain conditions to the self-oscillation; d) determination (identification) the characteristics/differences of rotor vibration, which lies in the fact that in most cases they are associated with the transverse vibrations of the rotors, while torsional or longitudinal oscillations play the incomparably smaller role, and therefore the last in this study were rejected; e)it is shown that the characteristic feature of the functioning of rotor systems of modern machines and units have no direct relationship with the level of vibration with amount of power that is transmitted through them or produced engine. Originality. In this paper the authors first considered the nonlinear response bearing lubrication layer, namely the coefficients of resistance and circulating forces that determine the dynamic coefficient of segment bearings. Practical value. The engineering calculations subharmonic stability and self-oscillations of the rotor (unbalanced) in unstable frequency of rotation are adjusted and significantly improved. The results of this work can be used to analyze rotary systems which under certain conditions can cause vibration that is not caused by some external periodic loads (or imperfections of the rotor) and the conditions of occurrence of which is not associated with some (any) resonant ratio (i.e., the system with self-excitation or self-oscillations). The latter are caused by the action of nonconservative forces of circulation type (circulation strength associated with the displacement vector of the rotor, not the velocity vector, as in systems with «negative» friction). As the circulating force vector is perpendicular to the vector displacement of the rotor, resulting in such a force can manifest themselves only in mechanical (rotary) systems with many degrees of freedom of movement greater than one. In addition, an important feature of the circulation of forces there should not be conservative, so the results can be used to study non-conservative rotor systems with asymmetric (skew-symmetric) matrix of coefficients.