Stability Of The Rotor-Bearing System With Air Excitation

Large-scale rotating machinery, as a kind of industrial infrastructure, has become one of key equipments in national foundation establishment and industry. With the increment of the speed and efficiency, higher requirements for dynamic characteristic, reliability and stability to large-sized rotating machinery has been made along. These realistic demands have promoted the development of rotor dynamics. With the development of the theory of modern nonlinear dynamics, nonlinear dynamics connects with rotor dynamics more tightly, which makes the research on rotor dynamics present a new outlook.Recently, it is the focus of domestic and international research to study the nonlinear forces acting on shaft, which generated by the small gap restraint between the motional and immobile parts, and to analyze and study the nonlinear dynamics actions of large-scale rotating machinery. In the study of rotor system, sources of self-exciter vibration (e.g., asymmetric bearing stiffness and non-asymmetic clearance in labyrinth seals) have been identified and extensively analyzed by investigators. However, the rotor dynamic forces due to clearance in turbines and compressors have received little attention.A Jeffcott rotor which is simple supported at its two ends is established first in this article. The disc comes under the effect of the air exciting-vibration force due to the eccentricity. Based on the hydrodynamic, by using momentum theory to the liquid in the flow channel, the computational formula of the air exciting-vibration force is acquired. By using four-step Runge-Kutta method, the periodic response results of the elastic rotor system with one single-disc are gained. Then the dynamic characteristics of the rotor system at the certain rotate speed and the certain physic parameter of system are analyzed by using the phase spaces and Poincare maps of this system.Second, a Jeffcott rotor model supported by two seals bearings in its two ends is established to simulate the shafting of simple turbines (only short-and-straight-blades are included in the shafting). And periodical response of the system is obtained by using the Newmark method. Then, the dynamic characteristics of rotor system at the certain rotate speed and the certain physic...