ANALYSIS OF NONLINEAR RIGIDITY CHARACTERISTICS OF AIR BLOWER COMPRESSOR ELASTIC SUPPORTS

Abstract

Vibrations of rotor systems are largely determined by elastic characteristics of supports. In the general case, the dependence of displacements on force for such supports is nonlinear. This applies to bearing supports of various types. In addition to bearings, elastic elements are also used in supports of rotor systems. They are designed to change the overall stiffness of the supports. The paper analyzes the radial stiffness of flexible ring dampers used in rotor supports. For this, two main approaches are proposed. The first is a conventional simulation of this problem of contact mechanics using the finite element method. The second is an analytical method that can be used as an alternative to expensive numerical calculations. This method is based on the principle of minimum additional energy. A special closed-form variational formulation is developed using the Euler-Bernoulli beam approximation for an elastic ring and a simplified model of normal contact on the ring flanges. It was shown that the surface tolerances of parts have a significant effect on the radial response of a flexible ring, which can become nonlinear. Tight fit of the ring on both sides makes it much stiffer, and non-tight fit leads to free movement of the rotor and much weaker damping of its movement. Both methods gave results that are consistent for the considered cases. By varying their design parameters, it is possible to adjust the rotor systems from critical modes of operation. Keywords: rotor system, elastic support, rigidity, finite element analysis, stress-strain state, contact interaction, principle of minimum additional energy