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Modal analysis strategy and nonlinear dynamic characteristics of complicated aero-engine dual-rotor system with Rub-impact

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Chinese Journal of Aeronautics 2022年第1期35卷 184-203页

作者： Pingchao YU Guo CHEN Lunxu LI College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China

This paper aims to gain insight into the nonlinear modal characteristics and the possible influence of the modes on the responses for the practical dual-rotor system with Rub-impact in aero-engine.The finite solid element method combined with a constraint stiffness model produced by Rub-impact is introduced to build the governing equation of the complicated nonlinear dual-rotor system.In order to deal with the efficiency and numerical divergence in the process of solving the nonlinear modes of this large-scale nonlinear system,an analysis strategy is proposed by integrating a two-layer reduction technique into the harmonic balance method.The effectiveness of the analysis strategy is validated by applying to a simple rotor system,which can easily obtain the theoretical result.Based on the modeling method and analysis strategy,the modal characteristics of an aero-engine dual-rotor system with Rub-impact are revealed.The results show that the modal frequency of the dual-rotor system increases when Rub-impact occurs and has the feature of interval,which allows us to obtain the critical speeds of the rubbing system by traditional Campbell diagram.The rotation direction is an important factor since it can not only affect the gyroscopic effect but also change the friction effect of the Rub-impact.It is found that the modal frequencies of the counter-rotation dual-rotor are less than those of co-rotation condition.More importantly,the forward modes of the counter-rotation dual-rotor may be instable when Rub-impact occurs at a certain rotor,while the corresponding modes under the co-rotation condition are always stable.Furthermore,by analyzing the rubbing response of the dual-rotor,it is found that the modal characteristics have an important influence on rotor’s response.The instable forward modes existing in the counter-rotation dual-rotor may lead to the divergence of the response when passing the corresponding critical speed.

关键词： Dual-rotor system Instability Modal characteristics Rub-impact Vibration response

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A Rub-impact Recognition Method Based on Improved Convolutional Neural Network

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Computers, Materials & Continua 2020年第4期63卷 283-299页

作者： Weibo Yang Jing Li Wei Peng Aidong Deng College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing210016China School of Information Engineering Nanjing Audit UniversityNanjing211815China National Engineering Research Center of Turbo-generator Vibration Southeast UniversityNanjing210009China

Based on the theory of modal acoustic emission(AE),when the convolutional neural network(CNN)is used to identify rotor Rub-impact faults,the training data has a small sample size,and the AE sound segment belongs to a single channel signal with less pixel-level information and strong local correlation.Due to the convolutional pooling operations of CNN,coarse-grained and edge information are lost,and the top-level information dimension in CNN network is low,which can easily lead to overfitting.To solve the above problems,we first propose the use of sound spectrograms and their differential features to construct multi-channel image input features suitable for CNN and fully exploit the intrinsic characteristics of the sound spectra.Then,the traditional CNN network structure is improved,and the outputs of all convolutional layers are connected as one layer constitutes a fused feature that contains information at each layer,and is input into the network’s fully connected layer for classification and identification.Experiments indicate that the improved CNN recognition algorithm has significantly improved recognition rate compared with CNN and dynamical neural network(DNN)algorithms.

关键词： Acoustic emission signal deep learning convolutional neural network spectral features Rub-impact

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Dynamic Characteristics of Multi-degrees of Freedom System Rotor-bearing System with Coupling Faults of Rub-impact and Crack

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Chinese Journal of Mechanical Engineering 2014年第4期27卷 785-792页

作者： REN Zhaohui ZHOU Shihua LI Chaofeng WEN Bangchun School of Mechanical Engineering and Automation Northeastern University

Extensive studies on rotor systems with single or coupled multiple faults have been carried out. However these studies are limited to single-span rotor systems. A finite element model for a complex rotor-bearing system with coupled faults is presented. The dynamic responses of the rotor-bearing system are obtained by using the rotor dynamics theory and the modern nonlinear dynamics theory in connection with the continuation-shooting algorithm（commonly used for obtaining a periodic solution for a nonlinear system） for a range of Rub-impact clearances and crack depths. The stability and Hopf instability of the periodic motion of the rotor-bearing system with coupled faults are analyzed by using the procedure described. The results indicate that the finite element method is an effective way for determining the dynamic responses of such complex rotor-bearing systems. Further for a rotor system with Rub-impact and crack faults, the influences of the clearances are significantly different for different Rub-impact stiffness. On the contrary, the influence of crack depths is rather small. The instability speeds of the rotor-bearing system increase due to the presence of the crack fault. The results obtained using the new finite element model, presented for computation and analysis of dynamic responses of the rotor-bearing systems with coupled faults, are in accordance with measurements in experiment. The formulations given can be used for diagnosis of faults, vibration control, and safe and stable operations of real rotor-bearing systems.

关键词： rotor-bearing system Rub-impact crack dynamic characteristic instability

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DETECTION OF EARLY Rub-impact IN ROTORS VIA HIGHER-ORDER TIME-FREQUENCY ENTROPY

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Chinese Journal of Mechanical Engineering 2004年第4期17卷 614-617页

作者： ChenZhongsheng YangYongmin HuZheng ShenGuoji CollegeofMechatronicsEngineenngandAutomation NationalUniversityofDefenseTechnologyChangsha410073China

Due to the calculation problem of classical methods (such as Lyapunovexponent) for chaotic behavior, a new method of identifying nonlinear dynamics with higher-ordertime-frequency entropy (HOTFE) based on time-frequency analysis and information theorem is proposed.Firstly, the meaning of HOTFE is defined, and then its validity is testified by numericalsimulation. In the end vibration data from rotors are analyzed by HOTFE. The results demonstratethat it can indeed identify the early Rub-impact chaotic behavior in rotors and also is simpler tocalculate than previous methods.

关键词： Higher-order time-frequeney entropy(HOTFE) Chaotic behavior Early faults Rub-impact

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Dynamics of Rotor-Bearing System with Coupling Faults of Pedestal Looseness and Rub-impact

Dynamics of Rotor-Bearing System with Coupling Faults of Ped...

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第十一届IFTOMM世界大会

作者： Bangchun Wen Hongliang Yao Changli Liu School of Mechanical Engineering & Automation Northeastern University Shenyang 110004 China Zhenping Li State Key Lab of Automotive Safety and Energy Tsinghua University Beijing 100084 China

＜正＞The dynamical model of elastic rotor-bearing system with coupling faults of pedestal looseness and Rub-impact is formulated by using modern nonlinear dynamics and rotor dynamics. In view of the strong nonlinear characteristics of the oil film force in the short bearing and the coupling faults of the rotor-bearing system, the system is numerically studied by using Runge-Kutta method. The bifurcation diagrams with rotating speed as controlling parameter, some representative figures of Poincare sections, journal center trajectories and frequency spectrum diagrams are provided. It’s found that Rub-impact affects the dynamics of the coupling faults system much when rotating speed is near the first order critical speed. When rotating speed is high, the dynamics of the coupling faults system resembles that of the pedestal looseness rotor system. The results may bring up theoretical references for the fault diagnosis of rotor-bearing system with coupling faults mentioned above.

关键词： Rotor-bearing system Pedestal looseness Rub-impact Coupling fault Bifurcation Chaos

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DYNAMICS OF ROTOR-BEARING SYSTEM WITH COUPLING FAULTS OF CRACK AND Rub-impact

DYNAMICS OF ROTOR-BEARING SYSTEM WITH COUPLING FAULTS OF CRA...

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第五届国际振动工程会议

作者： Li Zhenping Yao Hongliang Liu Changli and Wen Bangchun School of Mechanical Engineering &Automation Northeastern University Shenyang China 110004

＜正＞ An elastic rotor-bearing system withcoupling faults of crack and Rub-impact is studied on thebasis of nonlinear dynamics and rotor dynamics theory inthis paper.A dynamic model of the rotor-bearing systemis established considering the oil-force and the couplingfaults of crack and Rub-impact.In view of the strongnonlinear characteristics of the oil film force in the shortbearing and the rotor-bearing system with coupling faults,nonlinear dynamic behavior that is induced by couplingfaults of the crack and the Rub-impact,is numericallystudied by bifuration diagrarms,amplitude spectrums,and Poincare sections Runge-Kutta method.Abundantnonlinear phenomenon such as periodic motion,quasi-periodic motion and chaos are found,the resultsmay bring up theoretical references to fault diagnoses,dynamic design,and security running to rotor-bearingsystem.

关键词： coupling faults Rub-impact crack rotor-bearing-system chaos bifurcation

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Fault Diagnosis of a Rotor Based on a Lifting Wavelet and Local Wave

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International Journal of Plant Engineering and Management 2010年第1期15卷 13-17页

作者： WANG Feng-li GAO Hong-tao ZHAO De-you School of Ship Engineering Dalian University of Technology Dalian 116024 China College of Marine Engineering Dalian Maritime University Dalian 116026 China

Aiming at the mode mixture in local wave decomposition（LWD） caused by a noise signal, the original data is preprocessed using the lifting wavelet transformation to suppress abnormal interference of noise and improve the quality of decomposition. It is employed to analyze the vibration signal of rotor Rub-impact for extracting the weak impulsive feature. The signal is decomposed into intrinsic mode functions by LWD, then the high-frequency components are analyzed by Hilbert envelop demodulation. The period of the impulse response can be achieved, and the modulate fault feature of the vibration signal of a rotor system with Rub-impact fault can be extracted exactly. Analysis results show that the proposed method is accurate and efficient, and is expected to be applied in engineering practice effectively.

关键词： local wave lifting scheme fault diagnosis envelope demodulation Rub-impact

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