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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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Application of complex nonlinear modes to determine dry whip motion in a rubbing rotor system

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Chinese Journal of Aeronautics 2021年第1期34卷 209-225页

作者： Pingchao YU Yanhong MA Jie HONG Guo CHEN College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China School of Energy and Power Engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Achanceci Aero-Engine Beihang UniversityBeijing 100083China

Dry whip motion is an instability of rubbing rotor system and may cause catastrophic failures of rotating machinery.Up to now,the related mechanisms of the dry whip is still not well understood.This paper aims to build the relationship between the complex nonlinear modes and the dry whip motion,and propose an effective method to predict the response characteristics and existence boundary of the dry whip through complex nonlinear modes.For the first time,the paper discusses how to use the complex nonlinear modes to predict the dry whip systematically,and as a consequence,the mechanism of the relationship between the complex nonlinear mode and the dry whip is revealed.The results show that the Backward Whirl(BW)mode motion of the rubbing rotor system dominates the response characteristics and the existence boundary of dry whip.The whirl amplitude and whirl frequency of dry whip are equal to the modal amplitude and modal frequency of the BW mode at the jump up point where the modal damping is equal to zero.The existence boundary corresponds to the critical rotation speed where the minimum of the modal damping of the BW mode motion is exactly equal to zero.Moreover,the proposed nonlinear modal method in this article is very effective for the prediction of dry whip of the more complicated practical rotor system,which has been verified by applying the predicted method into a rubbing rotor test rig.

关键词： Complex nonlinear mode Dry whip Existence boundary Response characteristics

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Investigation on nonlinear lateral-torsional coupled vibration of a rotor system with substantial unbalance

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Chinese Journal of Aeronautics 2020年第6期33卷 1642-1660页

作者： Jie HONG Pingchao YU Yanhong MA Dayi ZHANG School of Energy and Power Engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Advanced Aero-Engine Beihang UniversityBeijing 100083China Beijing Key Laboratory of Aero-Engine Structure and Strength Beijing 100083China

Substantial unbalance may be caused by fan blade off during the operation period of gas turbine engines,and related dynamic problems are very critical to the safety design of rotor system in aero-engine.This article aims to understand lateral-torsional coupled vibration of the rotor system with substantial unbalance.The governing equation of a modified unbalanced rotor system is established based on Lagrangian approach.Then,a mathematical analytical method is proposed in which a linear approximation is derived and the Floquet theory and Hill’s method are incorporated,from which the modal characteristics of the unbalanced rotor are obtained.The modal characteristics of the unbalanced rotor system are revealed comprehensively for the first time.Furthermore,the relation between the modes and responses of the unbalanced rotor is discussed in detail.The results show that the lateral vibration and torsional vibration of the unbalanced rotor are coupled through the inertial terms in the governing equations.Due to the coupling,veering and lock-in phenomena occur between the frequencies of the forward whirl mode and the torsional mode.Furthermore,lock-in can lead to a kind of principal instability.With regard to the response of the unbalanced rotor,both natural vibration components and enforced vibration components appear in the lateral response,while only natural vibration components appear during torsional vibration.Moreover,natural vibration components play a crucial role in the response within the principal instability region and cause divergence of the vibration amplitudes in the lateral and torsional directions.

关键词： Instability Lateral-torsional coupled vibration Lock-in phenomenon Modes Unbalanced rotor

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Modal characteristics analysis for a flexible rotor with non-smooth constraint due to intermittent rub-impact

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Chinese Journal of Aeronautics 2018年第3期31卷 498-513页

作者： Jie HONG Pingchao YU Dayi ZHANG Zhichao LIANG School of Energy and Power Engineering Beihang University Collaborative Innovation Center of Advanced Aero-Engine Beihang University

Intermittent rub-impact, during which the contact between rotor and stator is characterized by a ‘‘bouncing＂ or intermittent type of behavior, is one of the most common rubbing forms in rotating machinery. When the intermittent rub-impact occurs, the non-smooth constraint, which is the phenomenon that the system stiffness changes with respect to the state of contact and noncontact, will appear. The paper aims at discovering the possible effects of the non-smooth constraint on the flexible rotor＇s modal characteristics by theoretical and experimental methods. The qualitative description for non-smooth constraint is given for the intermittent rub-impact process, and the dynamic modeling for a rotor system with non-smooth constraint is carried out. Meanwhile, the analysis method is developed by Floquet theory and Hill＇s method to obtain the rotor＇s modal characteristics. The results reveal that the non-smooth constraint produced by the intermittent rubimpact will increase the modal frequencies and critical speeds of the rotor system significantly.Due to the time-varying features of the constraint stiffness, the modal frequencies for the intermittent rub-impact rotor present fluctuant changes with the increase of rotation speed, which is different from the general linear rotor system. The non-smooth constraint is possible to lead the rotor＇s instability, and the rotor＇s instable regions can be expanded significantly for the increase of average constraint stiffness, constraint amplitude and contact time ratio. Non-smooth constraint could also expand the resonance speed and resonance sideband of the rotor system, which sometimes results in amplitude jump phenomenon.

关键词： Flexible rotor Intermittent rub-impact Instabifity Modal characteristics Non-smooth constraint

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一种静态转子系统连接参数辨识方法

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振动与冲击 2021年第8期40卷 10-18,27页

作者：杨默晗陈果于平超南京航空航天大学民航学院南京211106

针对转子系统连接参数辨识问题,研究一种转子系统连接参数的辨识方法。以某型含膜盘联轴器的转子试验器为研究对象,建立转子系统有限元模型,将支承刚度、支承位置和膜盘联轴器连接刚度作为辨识参数,并进行参数灵敏度分析。基于大量仿真... 详细信息

针对转子系统连接参数辨识问题,研究一种转子系统连接参数的辨识方法。以某型含膜盘联轴器的转子试验器为研究对象,建立转子系统有限元模型,将支承刚度、支承位置和膜盘联轴器连接刚度作为辨识参数,并进行参数灵敏度分析。基于大量仿真样本,采用支持向量回归(SVR)算法建立连接参数和固有频率之间的计算代理模型。在模态试验基础上,采用第二代非支配排序遗传算法(NSGA-II),基于多阶固有频率建立多目标函数,利用多目标优化法,寻找转子连接参数在修正区间中的Pareto最优解,最终识别出转子系统的多个连接参数。与试验结果相比,修正后的动力学模型固有频率仿真结果:第1阶的精度达到97.62%;第2阶的精度达到99.70%。

关键词：转子系统膜盘联轴器有限元计算代理模型修正参数辨识多目标遗传算法

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基于深度学习的航空发动机不平衡故障部位识别

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航空动力学报 2020年第12期35卷 2602-2615页

作者：陈果杨默晗于平超南京航空航天大学民航学院南京211106

针对基于机匣测点的航空发动机不平衡故障部位识别问题,提出了基于深度卷积神经网络的航空发动机不平衡故障部位诊断方法。针对某典型双转子航空发动机,建立整机耦合动力学模型,并利用数值积分算法实现不平衡故障数值仿真;在从发动机压... 详细信息

针对基于机匣测点的航空发动机不平衡故障部位识别问题,提出了基于深度卷积神经网络的航空发动机不平衡故障部位诊断方法。针对某典型双转子航空发动机,建立整机耦合动力学模型,并利用数值积分算法实现不平衡故障数值仿真;在从发动机压气机端到涡轮端的高、低压转子上选择4个不平衡故障部位作为诊断对象,通过仿真分析得到发动机典型转速下的转子不同部位不平衡故障的仿真样本;计算4个机匣测点信号的规范化频谱,通过对大量仿真数据的处理得到反映不同不平衡故障部位的故障样本集;利用仿真得到的大量不平衡故障样本,训练深度卷积神经网络,利用深度卷积神经网络的优良特征学习能力实现航空发动机不平衡故障的不同部位进行识别,数值试验结果表明该方法对航空发动机不平衡故障部位的识别准确率达到95%。

关键词：深度卷积神经网络航空发动机转子系统机匣测点不平衡故障故障部位识别

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Omicron variants breakthrough infection elicited higher specific memory immunity than third dose booster in healthy vaccinees

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Virologica Sinica 2023年第2期38卷 233-243页

作者： Pei yu Zijian Liu Zhuoqi Zhu Jiaqing Yang Min Deng Mingxiao Chen Changchun Lai Weiya Kong Shilong Xiong Li Wan Weikang Mai Lu Chen yu Lei Shahzad Akbar Khan Jianfeng Ruan An Kang Xuguang Guo Qiang Zhou Wenrui Li Zheng Chen yuemei Liang pingchao Li Lei Zhang Tianxing Ji Clinical Laboratory Medicine Department The Second Affiliated Hospital of Guangzhou Medical UniversityGuangzhou510260China State Key Laboratories of Respiratory Diseases Guangdong-Hong Kong-Macao Joint Laboratory of Infectious Respiratory DiseaseGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhou510535China Clinical Laboratory Medicine Department Dongguan Ninth People's HospitalDongguan523016China State Key Laboratory of Respiratory Disease Guangzhou Institute of Respiratory HealthThe First Affiliated Hospital of Guangzhou Medical UniversityGuangzhou510120China Clinical Laboratory Medicine Department Maoming People's HospitalMaoming525000China Laboratory of Pathology Department of PathobiologyUniversity of Poonch Rawalakot Azad Kashmir Pakistan 12350Pakistan Hospital Infection-Control Department The Second Affiliated Hospital of Guangzhou Medical UniversityGuangzhou510260China Medical Examination Department The Second Affiliated Hospital of Guangzhou Medical UniversityGuangzhou510260China Department of Clinical Laboratory Medicine The Third Affiliated Hospital of Guangzhou Medical UniversityGuangzhou510140China Kidney Transplant Department The Second Affiliated Hospital of Guangzhou Medical UniversityGuangzhou510260China Department of Organ Transplantation The Third Affiliated Hospital of Sun Yat-sen University510630China Guangzhou Key Laboratory for Clinical Rapid Diagnosis and Early Warning of Infectious Diseases KingMed School of Laboratory MedicineGuangzhou Medical UniversityGuangzhou511436China

Homologous booster,heterologous booster,and Omicron variants breakthrough infection(OBI)could improve the humoral immunity against Omicron variants.Questions concerning about memory B cells(MBCs)and T cells immunity against Omicron variants,features of long-term immunity,after booster and OBI,needs to be explored.Here,comparative analysis demonstrate antibody and T cell immunity against ancestral strain,Delta and Omicron variants in Omicron breakthrough infected patients(OBIPs)are comparable to that in Ad5-nCoV boosted healthy volunteers(HVs),higher than that in inactivated vaccine(InV)boosted HVs.However,memory B cells(MBCs)immunity against Omicron variants was highest in OBIPs,followed by Ad5-nCoV boosted and InV boosted HVs.OBIPs and Ad5-nCoV boosted HVs have higher classical MBCs and activated MBCs,and lower naïve MBCs and atypical MBCs relative to both vaccine boosted HVs.Collectively,these data indicate Omicron breakthrough infection elicit higher MBCs and T cells against SARS-CoV-2 especially Omicron variants relative to homologous InV booster and heterologous Ad5-nCoV booster.

关键词： Inactivated vaccine booster Ad5-nCoV booster Omicron variants breakthrough infection Memory immunity Binding antibody

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碰摩约束下柔性转子模态特性及其计算方法

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航空学报 2020年第12期41卷 251-263页

作者：于平超陈果王存杨默晗南京航空航天大学民航学院南京211106 北京动力机械研究所北京100074

以航空发动机低压(LP)转子为代表的柔性转子,通常具有两端大质量、细长轴和长跨度支承的"弱刚度"结构力学特征,这使得碰摩产生的约束作用不可忽视,其将会导致柔性转子模态特性改变,进而造成临界转速等动力学目标偏于设计状态。本文以典... 详细信息

以航空发动机低压(LP)转子为代表的柔性转子,通常具有两端大质量、细长轴和长跨度支承的"弱刚度"结构力学特征,这使得碰摩产生的约束作用不可忽视,其将会导致柔性转子模态特性改变,进而造成临界转速等动力学目标偏于设计状态。本文以典型航空发动机低压柔性转子为对象,结合梁单元法提出了此类复杂转子在碰摩约束下的动力学建模方法;将谐波平衡思想与频域的自由度缩减技术结合,提出了相适用的非线性模态求解方法;在此之上基于ANSYS和MATLAB平台,建立了含碰摩约束的复杂转子非线性模态分析的一般流程。将方法应用到某型柔性转子系统,成功获得其模态特性,结果表明:碰摩约束使转子模态频率增加,且随转子振幅增加而增加,尤其是对风扇碰摩较为敏感的一阶弯曲模态,正/反进动模态频率变化率可达16%和29%,但模态频率的变化始终在特定区间内;碰摩对转子模态频率的影响程度与陀螺效应、转子振型及机匣刚度密切相关,但对摩擦系数不敏感。由于接触点处摩擦力做功影响,柔性转子各阶反进动模态阻尼在碰摩严重时小于0,反进动模态能发生失稳。

关键词：柔性转子碰摩谐波平衡非线性模态稳定性

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止口螺栓连接结构解析建模与阻尼特性分析

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航空动力学报 2021年第12期36卷 2490-2502页

作者：于平超赵芝梅侯丽陈果南京航空航天大学民航学院南京211106 中国航空发动机集团有限公司商用航空发动机有限责任公司上海200241

针对止口螺栓连接,论文从连接结构轴向拉压力学行为分析出发,提出了可模拟连接非线性刚度和阻尼耗散的扇区模型,基于此进一步构建了弯矩载荷下的非线性解析模型。通过与三维实体有限元模型计算结果的对比分析,验证了所提出模型的有效性... 详细信息

针对止口螺栓连接,论文从连接结构轴向拉压力学行为分析出发,提出了可模拟连接非线性刚度和阻尼耗散的扇区模型,基于此进一步构建了弯矩载荷下的非线性解析模型。通过与三维实体有限元模型计算结果的对比分析,验证了所提出模型的有效性,并揭示了连接的非线性刚度特性和迟滞阻尼特性。基于所提出模型研究了关键参数对止口螺栓的阻尼特性的影响规律,结果表明:连接的阻尼耗散能力随弯矩载荷幅值和摩擦因数的增加呈现先增加后降低趋势,而随止口紧度和法兰长度的增加单调增加;法兰长度除对连接的阻尼耗散存在一定影响外,还能显著降低连接结构的等效刚度。

关键词：止口螺栓连接迟滞回线阻尼特性损耗因子解析力学模型

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基于整机的中介轴承外圈剥落故障振动分析

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航空动力学报 2020年第3期35卷 658-672页

作者：陈果贺志远尉询楷于平超南京航空航天大学民航学院南京210016 北京航空工程技术研究中心北京100076

针对某典型双转子航空发动机中介轴承外圈疲劳剥落故障诊断问题,基于整机振动耦合动力学模型,导入中介轴承外圈早期剥落故障模型,通过数值积分方法获取故障激励下的整机振动响应。提取并分析了中介轴承外圈剥落故障特征,从信号分析中发... 详细信息

针对某典型双转子航空发动机中介轴承外圈疲劳剥落故障诊断问题,基于整机振动耦合动力学模型,导入中介轴承外圈早期剥落故障模型,通过数值积分方法获取故障激励下的整机振动响应。提取并分析了中介轴承外圈剥落故障特征,从信号分析中发现:①出现了4倍外圈故障特征频率及其两侧以外圈旋转频率为间隔的调制边频带;②随着不平衡量增加,特征频率分量基本不变,边频带变得更加突出;③随着轴承游隙的增加,外圈故障引起的冲击更为强烈,特征频率及其调制边频均显著增加。通过比较从轴承座到机匣各测点信号的故障特征,结果表明中介轴承早期疲劳剥落产生的冲击通过轴承座传递到机匣将产生很大程度的衰减,在机匣测点信号中轴承故障特征基本消失。

关键词：双转子发动机整机振动中介轴承疲劳剥落故障振动分析

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