Research On The Unbalance Response Characteristics Of Nonlinear Bearing-rotor System

As the important equipment in the industry of petroleum,chemical,metallurgy,machinery and electric power,the rotating machinery which core components arebearing-rotor systems. In order to ensure the efficient and stable operation of therotating equipment, the accurate condition monitoring and fault diagnosis to the rotorsystem is used. Traditional rotor vibration analysis is based on the single channel andwe can judge the rotor’s unbalance,stiffness and damping information via theamplitude and the other information which are acquired by single channel. Because ofthe support components of bearing-rotor systems are anisotropic, which may lead to agreat difference between the vibration information obtained in the two verticaldirections. It will inevitably lead to misjudgment when using the single channelinformation to determine the rotor’s status. To solve the above problems, full vectorspectrum is applied to the research of unbalance response of the bearing-rotor system.Based on homologous fusion full vector spectrum technique can integrate thefault information of two channels, so it can reflect the real situation of the rotormovement. As the rotor system structure parameters have a significant impact on itsown dynamics, so establishing the links between full vector spectrum parameters androtor system parameters can provide an important basis for fault diagnosis of rotorsystems. The main contents are as follows:1. The dynamics equation of bearing-rotor system model is constructed whichusing the nonlinear stiffness coefficients, then the rotor imbalance fault mechanism isstudied. The paper has a brief introduction to the theoretical basis of the nonlinearrotor dynamics, and the dynamic characteristics of the nonlinear modal is studied.The results show that: nonlinear stiffness coefficient will cause the amplitudefrequency characteristic curve has a hard or soft characteristic properties, the jumpphenomenon of the unbalance response may occur.2. The relationship of the full vector spectrum parameters and rotor system parameters was established under the linear model, then the rotor’s unbalanceresponse was solved by fourth-order Runge-kutta method.The effect of stiffnessvariation in the two vertical directions on all parameters of full vector spectrum isstudied with different nonlinear stiffness coefficients. The results show that: stiffnessin two vertical directions has strong regularity influence on vibration vectors,ratio ofvibration vectors and the azimuth angle at a constant revolving speed.3. By using the method of full vector spectrum, the changing law of rotor’sunbalance response was studied on the conditions of ignoring and thinking aboutnonlinear stiffness coefficients respectively. At the same time, the results wereverified by influence coefficient method and the related experiment. The results showthat: for the linear modal, the trajectory of unbalance responses of different imbalanceare a set of concentric ellipses. The ratio of vibration vector and azimuth angle ofellipses remain unchanged; for the nonlinear modal, the azimuth angle and the ratio ofvibration vector of unbalance response due to different imbalance may change. Atnow, using the main vibration vectors to evaluate unbalance response will be morereasonable This results provide theoretical basis for the application of full vectordynamic balancing.