Numerical Study Of Fluid Rotordynamic Characteristics Of Journal Bearing And Seal In Rotating Machinery

Rotordynamic characteristics of journal bearing and seal are important contents in the study of rotor system dynamics of rotating machinery.With the development of modern rotating machinery in the direction of high pressure,high speed and high temperature,the effects of rotordynamic characteristics of journal bearing and seal on the operation efficiency of rotating machinery and the stability of rotor system are becoming increasingly prominent.It is valuable to study the rotordynamic characteristics of journal bearing and seal.In this paper,theoretical and numerical studies on rotordynamic characteristics of journal bearing and seal in rotating machinery were carried out.In the aspect of theoretical study,the theoretical basis of hydrodynamic lubrication of journal bearing and fluid dynamics of journal bearing and seal were analyzed firstly.Then,the theoretical solution models of the rotordynamic characteristics of journal bearing and seal were studied,including the solution models of uniform linear whirl orbit,single frequency whirl orbit and multi-frequency whirl orbit of the rotor.In the end,the influences of the dynamic characteristics of journal bearing and seal on the stability of rotor system were analyzed by the work of fluid exciting force.Study results show that: the frequency of oil film force is the same as the frequency of journal whirls.With the increase of the eccentricity of the journal,the absolute value of the rotordynamic coefficients increase.With the increase of whirl frequency and eccentricity of the journal,the absolute value of negative work of oil film force increases.The leakage flow of convergent-clearance hole-pattern damper seal is less than divergent-clearance hole-pattern damper seal in the case of equal average seal clearance.The convergent-taper hole-pattern damper seal has a larger positive direct stiffness coefficient,while the divergent-taper hole-pattern damping seal has larger positive direct damper coefficient.Pocket damper seal has a large radial airflow force pointing to the rotor whirl orbit center and a large tangential airflow force opposite to the rotor whirl velocity,so the pocket damper seal effectively reduces whirl amplitude and whirl velocity of the rotor.The larger whirl frequency and amplitude of the rotor,the larger absolute value of negative aerodynamic work of pocket damper seal,and the better vibration suppression effect of the pocket damper seal.When the rotor whirls with a forward or backward orbit,the pocket damper seal is more beneficial to the stability of the rotor.