Studies On The Dynamics Of Transient Heat Vibrations And Rubbings Of The Complicated Rotor System

With the development of industries and the improvement of science-technologies, the rotating machinery plays an even more important role in industrial producing, especially in aviations; it is of utmost importance to advance aero gas turbine engines in military and economic constructions. The key point to advance the engine is to improve its thrust-weight ratio and decreasing the gap between rotor and stator is one of the most effective approaches to increase the output power of the engine. But because of the existence of large unbalance and thermal bending, etc, the rubbing probability of rotor and stator increased greatly. However, at present in china and overseas, the studies on transient responses, heat shocks and rubbings of rotor and stator mostly have the limitations, such as the models are quite simple and the physical fields are very single, and it is rare to study the dynamics of complicated rotor system and multi-physics coupling rotor system. For examples, the study on transient responses and heat rubbings of multi-disc rotor during its starting and stopping period; study on rubbing of the double cantilever continuum rotor-bearing-receiver coupled system; study on rubbings of continuum dual-rotor-receiver coupled system; An analysis on thermal aviations of the three-dimensional solid element rotor system. All the complicated rotor systems have an even more complicated dynamics than the simple ones, to reveal its dynamics more precisely, in connection with the above problems, the author did a study on the dynamics of the complicated rotor system of the aircraft engines, here are the main contents and fruits of the study:(1) Since the starting and stopping of the multi-disc rotor system are transient, and the transient response of the multi-disc rotor system is more complex, often larger, than the steady-state response, this transient response is even more approaching to the real condition of the starting period of the rotor system. Therefore, with the application of Riccati transfer matrix-direct integration method(Wilson-θ), considering to the unbalanced force and unbalanced moments of the disc, the author works up a new force model of the disc, exporting the transient response transfer matrix expression of the multi-rotor system, working out the relevant analysis program of algorithm of the article, analyzing the transient response of the elastic support of the multi-disc rotor system, and discussing the influence of parameters on the transient response of the multi-disc rotor system, such as acceleration, unbalance, damp,(2)To reveal the dynamics of complicated rotor system during the hot starting process, the author applies the transient transfer matrix method which is combined the Riccati transfer matrix with Wilson-θ method, analyses the transient response of the multi-disc rotor system during the hot starting process in a steady-state temperature field. To simulate the transient response of the multi-disc rotor system when the rotor system have the heat bending in the steady-state temperature field, the author establishes a new computational model of massless shaft cross section in the steady-state temperature field, deriving creatively the transient response transfer matrix expression of the drive shaft unit during the hot starting process, working out the relevant analysis program, doing the numerical simulation of the transient response of the multi-disc rotor in the steady-state temperature, revealing some dynamics during the hot starting process, and providing theoretical and calculated basis for improving the stability of the rotor system.(3) Since the working environment of the rotor system of the aircraft engines are very bad, when starting the rotor with a great heat bending, which will result in the great vibration of the rotor, then, the ratio of hot rubbing of the rotor and stator increased sharply. To reveal the dynamics of transient heat rubbing of the beat bending rotor system, the author applies the approach which is combined the Riccati transfer matrix and the Wilson-θ method, establishing the dynamic equations of heat rub of the multi-disc rotor system, deriving creatively the transient response transfer matrix expression of the drive shaft unit during the hot starting process. Through establishing the relevant analysis program of the calculation, the author calculates and analyses the hot rub of the multi-disc rotor during the hot starting process, and find several non-linear dynamics of the transient unbalanced force rub, unbalanced force and the hot bending coupled rubbing. The calculating results shows that the non-linear dynamics of the transient unbalanced force rub, unbalanced force and the hot bending coupled rubbing is totally different from the steady unbalanced response of the single rotor rubbing.(4) Considering the real conditions of the rotor systems of engines whose qualities are mainly focused on the compressors and turbines, the author establishes a new double cantilever continuum rotor-bearing-receiver coupling dynamic model with rubbing, deriving the forth-order partial differential equations of motion of the double cantilever continuum rotor. Through establishing the relevant analysis program of calculations, the author researches on the rub of receiver and bearing coupling, bearing and rotor coupling, receiver and disc of a machine dynamic model with a double cantilever continuum rotor, which was simplified into coupling dynamic models of freedom, simulates the rub response of the system through the variable step forth-order Runge-Kutta method, and discusses the influences of speed and eccentricity on the rub response of the system, and finds several non-linear dynamics of the model when rub happens, which provides certain theoretical basis of solving the real engineering problems. Through comparing the vibrations of the models in the article with the single-disc rotor model, the author proves the essentiality of establishing the models in the papers.(5) In connection with the double rotor-receiver coupling system of the real aircraft engines of certain type, the author creatively establishes a dynamic model of continuum multi-disc double rotor-receiver coupling system, which simplified the bearing into spring and damp, considering the coupling of low-pressure rotor and high-pressure rotor through the medium bearing and the coupling of rubbings of high-pressure rotor and receiver, deriving the forth-order partial differential expression of motion of the continuum double rotor-receiver coupling system. Applying the variable step forth-order Runge-Kutta method, the author simulates the rub response of the double rotor system, establishing the relevant analysis program of calculation, analyzing the influence of speed, rub stiffness and stiffness of medium bearing on the rub response of the system, and finds several non-linear dynamics which differs from the rub responses of simple rotor systems, which provides a theoretical basis for solving the real engineering problems and has certain engineering meanings.(6) Taking the high-pressure rotor system of the aircraft engines of a certain type to study, the author brings forward some practical methods, such as2D sub-block series numbering and surface interpolation node coordinates, etc., and set up an elastic supported finite element model of three-dimensional solid elements of the high-pressure rotor. On the ground of the stopping of engines of the rotor system and the inadequate warm-up and basket in the process of starting, the temperature in the receiver is warm upper and cold lower and distributes unbalanced along with the bearing, basing on this conditions of steady-state temperature field and considering the function, its elastic modulus is temperature, applying the heat-structure-dynamics coupling theory and indirect coupling methods, the author analyses the influence of steady-state temperature field to the natural frequency of high-pressure rotor system, unbalanced response, unbalance and heat bending coupling response, discovers the sensitive factors which influence the heat vibration of rotor system and finds the dynamics which cannot be found in two-dimensional beam element models. The results show that, in the vibration researches on the rotor systems of the aircraft engines, it is very necessary to build the three-dimensional solid element model and consider the affection of steady-state temperature field on the vibrations of the rotor system.