Dynamic Modeling And Rub-impact Of Rotor System In Acomplicated Temperature Environment

High temperature, high pressure, fluid-solid coupling are typical operating environment of aircraft engine. Structural size and material properties among the engine components would be changed due to the complicated operating environment. For example, the non-uniform temperature distribution of operating environment will produce the thermal stresses and associated axial displacements on shaft, and when displacement is large enough, the contact or rubbing between the rotor and stator would occur. They are all the main factors that affecting the performance of dynamics and breeding potential failure on engine, especially, the influence on the vibration characteristics of the rotor is a new topic in the field of rotor dynamics, which is worth to be explored.In this subject, the rotor structure and complicated operating temperature of aero-engine is taken as the research background, and the complicated temperature environment with time-varying characteristics and the structural characteristics of the rotor system are also taken into consideration. The axial displacement of the shaft and the axial clearance variation, caused by non-uniform temperature field and different thermal expansion coefficients between the rotor and stator, are investigated. The contact and squeeze problems due to axial displacement are important factors which could result in rubbing and vibration of the system. The entire research procedure is combined with the methods of theoretical modeling, numerical calculation and dynamic analysis. The main contents of this subject are list as follows:(1) A new dynamical modal of the shaft is established for axial displacement analysis based on temperature internal force due to non-uniform temperature field. Based on the influence of temperature internal forces, the analytical formulae of a point axial displacement are derived, respectively, when the shaft is in a continuous temperature field and a discretized temperature field. Assumed that the temperature distribution in accordance with gauss function, then the accelerated warming formula is used to simulate the warming up and constant temperature time periods, and the variation regularity of the two formulae are compared and analyzed. Finally, the feasibility and relevance of the new model are verified by the process of the equivalent proof.(2) The rubbing between rotor and stator caused by the axial displacement of the shaft is approximated as surface contact/squeeze process and the surface contact/rubbing model is established. Then the rotor-bearing system is built by using the lumped-mass approach. After the numerical integration method is employed for the model, the effect of annulus surface rubbing on the system is investigated during both warming and constant temperature periods. The results show that rubbing failure caused by the axial displacement of shaft is as important as other rubbing phenomena, and the surface rubbing is also an important factor that affects the normal operation.(3) Nonlinear factors are considered when building the single disc rotor-bearing dynamics model, the sum of cube term and linear term is used to describe the physics nonlinear factors of bearing supports and shaft bending. The shaft axial displacement and surface rubbing are introduced into the analysis. The rotor dynamics and nonlinear analysis methods are used for the analysis of entire circumference rubbing, and the radial/axial coupling rubbing and their effect on the response. Results show that when surface rubbing occurs, the energy, the vibration response amplitude and the nonlinear dynamic behavior of system would be changed.(4) According to the structural characteristics, the main rotor is simplified as a rotor-bearing system with double-disk. The lumped mass method is employed to establish the dynamic model with8-degrees of freedom for the bending vibration analysis of the main rotor in a complicated temperature environment. The axial displacement of the shaft, with three temperature sections, driven by the thermal expansion is calculated. Further the model of annulus surface rubbing is formulated. The structure of rotor would be changed due to thermal expansion, so that the bending stiffness and natural frequency are all affected. Results show that the effects of different disk rubbing would produce different degrees of friction on system vibration response.(5) For the dynamics analysis of double-disk rotor bearing system, using the Lagrange method to establish the bending/torsion coupling differential equations, with the consideration of unbalanced excitation force and thermal expansion. Focus on characteristics of torsional vibration analysis, as well as torsional vibration caused by the thermal expansion and surface contact rubbing. The shaft axial thermal deformation and disk contact rubbing are key factors that causing the torsional vibration on the rotor shaft.