| As the most complicated rotating machine,the aero-engine is excited by multiple excitation loads such as rotor unbalanced force simultaneously,which causes the vibration problems of components and the overall engine extremely serious.In addition,to further increase the thrust-to-weight ratio,aero-engines have been developed in the direction of light-weight and high-thrust,which has further led to the deterioration of rotor vibration conditions and the strengthening of vibration coupling of different components.To ensure the safety and reliability of the operation for aero-engines,the research on the vibration characteristics of the overall engine has received widespread attention.At present,the research on the aero-engine's overall structural dynamics has achieved fruitful achievements in the aspects of overall engine modeling technology,high-efficiency solution technology of complex dynamic models,linear/nonlinear dynamic response analysis,and overall engine vibration control and suppression.However,most of these studies were based on linear/nonlinear transient and steady-state dynamic response analyses,which can only provide limited information such as transient/steady-state displacements,velocities,accelerations,stresses,and mode shapes to predict,analyze,and judge the vibration conditions of overall engine.It is difficult to give a rational explanation for the vibration transmission and coupling characteristics between the aero-engine rotation and static components,and vibration control and suppression mechanisms as well.In order to overcome the above-mentioned limitations,this study applied the structural intensity method to the field of aero-engine overall structural dynamics,visualizing the invisible and intangible instantaneous/steady-state vibration energy in the aero-engine rotor-support-casing coupling system in the time/frequency domain,and analyzing the instantaneous/steady-state vibration energy transmission and coupling characteristics between the rotor and casing components.Based on this,from the perspective of instantaneous/steady-state vibration energy transmission control,the mechanism of vibration suppression of the components and the overall engine was analyzed,and corresponding vibration attenuation measures were proposed.The main research contents involved in this paper are listed as follows:(1)Theoretical Foundation: This study begun from the perspective of vibration waves,and theoretically analyzed the types and propagation characteristics of vibration waves in structures.Based on this,the general expression of the structural intensity was expressed as the forms of different types of vibration waves and different types of structural elements.The decomposition of the total structural intensity field into different types of vibration waves was realized by expanding into the matrix form.This part lays a solid theoretical foundation for this study.(2)Realization Approach: This study combined the ANSYS secondary development program APDL with powerful finite element modeling and solving functions and MATLAB software with powerful matrix calculating and processing capabilities to compile and develop a structural intensity vector field solution and visualization program,and the fully automatic solution and visualization of the instantaneous/steady-state structural intensity fields of the aero-engine rotor-support-casing complicated coupling system have been achieved base on the proposed FLAG communication mechanism.This part provides a powerful realization approach for the study in this paper.(3)Research on Instantaneous/Steady-State Vibration Energy Transmission Characteristics: Based on the above theoretical foundation and realization approach,a model of the aero-engine rotor-support-casing coupling system was established.The visualization analyses of the transmission and coupling characteristics of the instantaneous/steady-state total vibration energy and the vibration energy components carried by different types of vibration waves among the rotors,the supports and the casings were realized.Based on the general equation of motion,the inherent physical relationship between vibration energy transmission characteristics and structural vibration characteristics was derived theoretically,and the transmission,conversion,and balance processes between instantaneous vibration energy and mechanical energy and damping dissipated energy in different mode shapes of rotors were analyzed.Moreover,the vibration energy flux ratio and the vibration energy transmission ratio were proposed and defined in this study,and the quantitative analysis of the vibration energy transmission characteristics was realized.(4)Research on Instantaneous/Steady-State Vibration Energy Transmission Control: Based on the above understanding of instantaneous/steady-state vibration energy transmission and coupling characteristics,from the perspective of the shunting and dissipating mechanisms of vibration energy vortex fields,the instantaneous vortex fields induced by the circumferential grooves of the rotor shaft and the steady-state vortex fields induced by the mounts and the ring-stiffeners were proposed to attenuate the vibration of the rotor and casing;from the perspective of vibration energy coupling characteristics,it was proposed to apply secondary reverse excitations to block the transmission of the vibration energy and attenuate the structural vibration.And the mechanisms and effects of these approaches on the vibration suppression of aero-engine components and the overall engine were analyzed.(5)Research on Nonlinear Vibration Energy Transmission Characteristics: Based on a plate assembly with bolted preload flange joints,the transmission characteristics of instantaneous vibration energy in nonlinear structures were investigated.Combining phase plane method and structural intensity method,corresponding analysis of the system's macroscopic motion state change process and microscopic vibration energy transmission process was achieved,which realizes the prediction of structural vibration energy transmission characteristics only through the state quantities of displacements and velocities,and avoids the difficulties caused by the experimental measurements of instantaneous structural intensity vector fields.The structural intensity method was applied to the field of aero-engine overall structural dynamics,and the visualization analysis of the instantaneous/steady-state vibration energy transmission characteristics in a complicated rotor-support-casing coupling system was realized.From the perspective of vibration energy transmission,the vibration problems of the aero-engine subjected to the rotor unbalanced forces were studied,and the vibration energy transmission and coupling characteristics between various components of the aero-engine were revealed.In addition,some vibration attenuation measures were proposed from the perspective of instantaneous/steady-state vibration energy transmission control,which can provide powerful theoretical support and engineering guidance of the vibration suppression methods for various components and the overall aero-engine. |
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