Fault Rotor Bending And Bending - Torsional Coupled Vibration Characteristics Of The Study

In the modern production, rotating machineries are developing in facing the direction of a high speed, overlap, automation and function diversified. As the key component of rotating machinery, the rotor system is often induced many problems. Due the harsh operating environment and the error of equipment during the installation process, rotor system often induces a variety of complex and nonlinear factors, and that’s why the rotating machinery stimulates fierce vibrations. For example, the rubbing between the moving parts and the stationary parts will produce vibrations. Rubbing fault usually behaves the indirect result of other failures. May be it caused by the mass unbalanced, rotor bending, also may be caused by rotor misalignment or thermal expansion, etc. Once the rubbing happens, rotor components are likely to cause destructive faults which duo to reverse fatigue or excessive bending motion. Light affect will influence the work efficiency, and then heavy affect will cause a machine crash. Unbalanced fault is often hidden in the units, and it could easily trigger a vicious vibration incidents. On general circumstances, damage casualties, social harm and economic loss caused by these accidents are usually immeasurable.In the past, the vibration characteristic research of rotor system generally unable set up a simple model, however, this model has not been able to qualify for more complex units. So. the paper was applied modern numerical analysis theory and rotor dynamics theory to study rotor system of composite faults modeling, solving and coupled bending-torsional vibration characteristics. It has become a hot research topic at home and broad today.This paper set up four rotor system models from single failure and composite failure to study the vibration characteristics of coupled bending and torsion. Step1. the paper established a dynamic model of rotor with unbalanced mass, support by two rolling bearings. In this model, influence of nonlinear Hertzian contact force between the rolling bodies and inner-outer rings of the rolling bearings on dynamic property of the rotor-bearing system is considered. Step2, aimed at both ends of the rigid support for single rotor disc, this paper established a rubbing rotor model. Step3, it established a coupled bending-torsional vibration model of the unbalanced rotor system which under external forces and external torques. Step4, it established a finite element model of rotor system which contains both the type of unbalance and rubbing fault.For these four models, this paper used two numerical methods which are the fourth-order Runge-Kutta method and Newmark method to solve the response of system. Moreover, it analyzed the motion characteristics of each rotor system under the particular parameters by means of the displacement diagram, the spectrogram, the envelope diagram, the carrier diagram, the phase diagram, the chart of axes track and the Poincare mapping. Through the above related graphic, it analyzed the response of the rotor system with certain parameters (speed, rotor mass, bearing equivalent mass, eccentricity, shaft equivalent stiffness, etc.) changes in a system. What’s more, it researched the vibration characteristics of coupling failure. This laid a theoretical basis for the fault diagnosis of different conditions.