Application of Improved Hybrid Interface Substructural Component Modal Synthesis Method in Vibration Characteristics of Mistuned Blisk

The large and complex structures are divided into hundreds of thousands or millions degrees of freedom（DOF） when they are calculated which will spend a lot of time and the efficiency will be extremely low. The classical component modal synthesis method （CMSM） are used extensively, but for many structures in the engineering of high-rise buildings, aerospace systemic engineerings, marine oil platforms etc, a large amount of calculation is still needed. An improved hybrid interface substructural component modal synthesis method（HISCMSM） is proposed. The parametric model of the mistuned blisk is built by the improved HISCMSM. The double coordinating conditions of the displacement and the force are introduced to ensure the computational accuracy. Compared with the overall structure finite element model method（FEMM）, the computational time is shortened by23.86%–31.56%and the modal deviation is 0.002%–0.157% which meets the requirement of the computational accuracy. It is faster 4.46%–10.57% than the classical HISCMSM. So the improved HISCMSM is better than the classical HISCMSM and the overall structure FEMM. Meanwhile, the frequency and the modal shape are researched, considering the factors including rotational speed, gas temperature and geometry size. The strong localization phenomenon of the modal shape’s the maximum displacement and the maximum stress is observed in the second frequency band and it is the most sensitive in the frequency veering. But the localization phenomenon is relatively weak in 1st and the 3d frequency band. The localization of the modal shape is more serious under the condition of the geometric dimensioning mistuned. An improved HISCMSM is proposed, the computational efficiency of the mistuned blisk can be increased observably by this method.

Vibration Characteristics of Mistuned Bladed Disks

The finite element models of blade, disk and bladed disk are built up by finite element software ANSYS. The natural frequencies of the single blade, the whole bladed disk and the bladed disk with only one sector by cyclic symmetry boundary have been calculated. Then, based on the results above, a structure dynamic model of multiple degree-of-freedom （MDOF） systems is established to simulate the bladed-disk assembly. Solve the motion equation by using the Runge-Kutta Method （Gill Method）. The dynamic response of the MDOF system is achieved. As for the given mistuning patterns, the vibration responses of bladed disks are calculated. The results have been compared and analyzed, and the optimum pattern is selected.

失谐涡轮叶片模态特性分析

针对涡轮增压器的涡轮叶片由于失谐产生的振动问题,建立涡轮叶片子结构模型并进行模态分析,绘制Campbell图,并对不同标准差失谐叶片进行固有频率和振型测量。结果表明,当叶片发生失谐时,周期性被破坏,一个或几个叶片振动异常,表现出振动局部化现象。因此,在设计时应避免应力集中导致涡轮叶片损坏,防止涡轮增压器发生故障。叶片随机失谐及叶盘结构共振特性之间的关系是研究叶片振动特性的关键,而研究这一环节可以保证运行稳定以及提升性能,对叶片失谐研究具有重要意义。

Forced response characteristics of bladed disks withmistuning non-linear friction

Aimed at the difficulty in revealing the vibration localization mechanism of mistuned bladed disks by using simple non-linear model,a mechanical model of the bladed disk with random mistuning of hysteretic dry friction damping was established.Then,the incremental harmonic balance method was used to analyze the effects of the parameters of bladed disks,such as the mistuning strength of dry friction force,coupled strength,viscous damping ratio and friction strength,on the forced response of the bladed disks.The results show that the vibrational energy localization phenomenon turns up in the tuned bladed disks if the nonlinear friction damping exists,and the random mistuning of the dry friction force intensifies this kind of vibration localization.

Aeroelastic Analysis of a Transonic Fan Blade with Low Hub-to-Tip Ratio including Mistuning Effects

This paper presents a comprehensive investigation of aeroelastic stability for a high aft-swept transonic fan blade with low hub-to-tip ratio. The evolution of the blade’s aeroelastic stability in the first bending modes is studied. A 3D flutter computation representing today’s industry standard is performed. Steady state flow field and motion-induced unsteady pressures acting on the blade have been determined by a 3D Reynolds-Averaged Navier-Stokes (RANS) equations with a standard k-ε turbulence model. A weakly coupled (one-way) method has been employed to describe the interaction between fluid and structure. The results of aerodynamic damping indicate a significant shock-driven risk. To increase the flutter margin by a viable method, a statistical mistuned aeroelastic stability investigation has been performed. It has been found that alternately intentional mistuning with a small blade frequency offset stabilizes the system effectively. However, as the standard deviation of random mistuning reaches some critical values, the introduction of alternately intentional mistuning does not provide any additional stabilizing effects.

失谐整体叶盘的改进子结构建模方法

针对复杂失谐叶盘结构振动分析中的计算效率问题,提出一种改进的子结构建模及分析方法。根据整体叶盘结构的几何特征,将其划分为轮盘及叶片子结构。然后,对叶片-轮盘交界面均匀选取减缩自由度;通过转换矩阵将减缩自由度转换为子结构的内部自由度。最后,使用子结构模态综合法完成减缩自由度的凝聚,建立整体叶盘结构的减缩模型。以某型整体叶盘为例,利用改进的子结构分析模型,在典型危险工况下评估了结构的失谐水平。研究结果表明该方法在确保计算精度的前提下能够高效求解随机失谐整体叶盘的振动响应。

压气机叶片非同步振动机理及气动布局优化研究

针对航空发动机叶片中的非同步振动诱发叶片断裂失效问题,基于时域推进的方法建立了压气机全周物理域的流固双向耦合模型,旨在对周向非定常扰流和叶片气动弹性特征进行更合理的描述。通过该模型揭示了叶片非同步振动的发生机理,并通过一定的气动布局手段优化了叶片表面气动力和振动幅值。研究表明:叶尖泄漏流与主流掺混后形成的通道涡是诱发叶片产生非同步振动的根本原因,而掺混流的周向传播强度仅在一适中的范围内时才具有产生明显通道涡的能力,并提出以通道前缘截面上的流动相对周向动量Wmix为判断通道涡和振动幅度强弱的依据。导叶偏转角或导叶栅距非谐程度的增大,均会对掺混流的周向强度有一定的加强作用,使得通道涡强度和非同步振动幅值呈现先增大后减小的趋势。

失谐整体叶盘多模态振动抑制的吸振器阵列方法

整体叶盘是新一代高性能航空发动机的关键部件,具有结构紧凑、重量轻和推重比高等优点,但也存在结构阻尼低、模态密度高和随机失谐问题,导致其通过共振区域时振幅大,显著影响整体叶盘结构的可靠性和疲劳寿命.为有效抑制失谐整体叶盘的多模态振动,提出一种由一系列吸振器环状布置而成的吸振器阵列减振方法,通过设置多组匹配不同模态的吸振器,实现对多模态共振峰值的抑制.为揭示吸振器阵列方法的多模态减振机理,采用具有代表性的集中参数模型构建整体叶盘−吸振器阵列系统的动力学分析模型,结合解析形式的功率流分析方法,分析吸振器质量、频率调谐精度、阻尼水平以及吸振器个数等关键参数对吸振器阵列减振性能的影响.搭建了吸振器阵列方法验证实验台,并通过实验验证了吸振器阵列方法的效果.分析结果表明:吸振器阵列方法能够有效控制叶片主导与叶片−轮盘耦合型模态,能够以较小的质量实现对谐调与失谐整体叶盘多模态共振的高效抑制,减振性能的鲁棒性较好.

Influence of Non-uniform Parameter of Bolt Joint on Complexity of Frequency Characteristics of Cylindrical Shell

Bolt connection is one of the main fixing methods of cylindrical shell structures.A typical bolted connection model is considered as a tuned system.However,in the actual working conditions,due to the manufacturing error,installation error and uneven materials of bolts,there are always random errors between different bolts.To investigate the influence of non-uniform parameters of bolt joint,including the stiffness and the distribution position,on frequency complexity characteristics of cylindrical shell through a statistical method is the main aim of this paper.The bolted joints considered here were simplified as a series of springs with random features.The vibration equation of the bolted joined cylindrical shell was derived based on Sanders’thin shell theory.The Monte Carlo simulation and statistical theory were applied to the statistical analysis of mode characteristics of the system.First,the frequency and mode shape of the tuned system were investigated and compared with FEM.Then,the effect of the random distribution and the random constraint stiffness of the bolts on the frequency and mode shape were studied.And the statistical analysis on the natural frequencies was evaluated for different mistuned levels.And some special cases were presented to help understand the effect of random mistuning.This research introduces random theory into the modeling of bolted joints and proposes a reference result to interpret the complexity of the modal characteristics of cylindrical shells with non-uniform parameters of bolt joints.

失谐螺栓连接对薄壁圆筒的动力特性影响

螺栓连接结构的性能退化是航空发动机安全运行必须考虑的问题,螺栓连接预紧失谐这个概念可以表征螺栓连接结构的性能退化,并用预紧失谐量和预紧失谐比例说明预紧失谐的状态。在此基础上,将预紧失谐的概念与螺栓连接改进薄层单元法相结合,研究失谐螺栓连接对薄壁圆筒动力特性的影响。针对预紧失谐对薄壁圆筒的确定性动力特性进行分析,包括固有特性、稳态响应的影响,考虑螺栓预紧力的随机性,研究失谐螺栓连接对薄壁圆筒的概率性动力特性分析。研究结果表明:薄壁圆筒同阶固有频率的分离程度随着预紧失谐量的减小而增大,随着预紧失谐比例的增大呈现“双峰”特点;预紧失谐使得薄壁圆筒响应峰值对应的频率减小但幅值增大,随机预紧失谐使得响应峰值点的频带更宽,并且输入参数为指数分布时,输出参数为威布尔分布。

气动非谐对叶片非定常气动激振力影响

为降低转子叶片在前排静子叶片尾流激振情况下的共振应力,提高转子叶片疲劳寿命,对静子叶片的气动非谐设计进行研究.对静子叶片的气动非谐设计考虑了两种方案,一种为非均匀叶栅设计,另一种为不对称叶栅设计.通过对静子-转子模型流场进行非定常计算,比较了两种非谐设计思想下转子叶片表面气动激振力频谱成分和幅值大小.分析结果标明:非均匀叶栅非谐设计并不能降低转子叶片表面激振力,同时会引起频率成分和幅值都较大的倍频成分;不对称叶栅非谐设计虽然会引起与转速同频的较大幅值激振力成分,但从整体考虑可有效降低叶片振动应力.

失谐叶盘结构振动响应局部化实验研究

基于作者提出的预测失谐叶盘结构最大失谐幅值放大系数及最坏失谐模式的方法,利用搭建的行波激励实验系统,针对典型的整体叶盘结构模型试件进行了失谐振动响应局部化实验。首先通过有限元仿真确定失谐叶盘振动响应局部化实验所需的最坏失谐模式,然后经过数据采集与后处理得到行波激励下失谐叶盘结构的强迫响应,通过实验验证了失谐跳变-强迫响应局部化现象,实验结果与理论分析取得较好一致性。

失谐叶片-轮盘结构系统振动局部化问题的研究进展

对近２０年来国内外关于失谐叶片－轮盘结构系统振动局部化问题研究的进展进行了较为详细的评述和讨论，文中首先说明了振动局部化问题的基本概念，然后对失谐叶片－轮盘结构系统模态局部化和动态响应局部化在分析模型、求解方法及其基本性质和规律等方面的研究进展进行了较为全面的评述，最后提出了今后应深入研究的问题．

基于微动滑移摩擦模型的失谐叶盘系统振动分析

在航空发动机叶-盘系统中,由于叶片失谐导致严重的振动局部化,造成局部叶片的高周疲劳,拟采用增加叶根干摩擦的方法降低失谐叶-盘系统振动幅值,减轻其振动局部化程度。基于微动滑移摩擦模型建立叶根阻尼器干摩擦力本构关系,采用等效椭圆代替阻尼器力与位移函数关系的迟滞回线,获得阻尼器的等效阻尼、等效刚度;将等效阻尼、等效刚度作用于叶-盘系统集中参数模型上,建立单个扇区三自由度整周失谐叶-盘系统动力学方程;采用谐波平衡法对其进行振动特性分析,讨论了叶根干摩擦对失谐叶盘系统振动特性的影响。结果表明:叶根摩擦能显著降低系统共振幅值;有叶根摩擦系统较无叶根摩擦系统的共振峰在频率上延后;增加叶根摩擦可有效降低失谐叶-盘系统的振动局部化程度。

多级叶盘结构随机失谐响应特性分析

为研究多级叶盘结构最大失谐强迫响应幅值及最坏失谐模式,通过设置失谐变量为优化变量,提出了运用遗传算法和序列二次规划混合方法确定最大的失谐强迫响应幅值及最坏失谐模式的通用方法。针对典型三自由度扇区单级和耦合两级叶盘结构集中参数模型计算了相应谐调系统叶片刚度失谐时的最大失谐幅值放大系数及最坏失谐模式,揭示了失谐跳变-局部化现象,通过算例说明在失谐跳变的叶片位置,叶片出现了强烈的振动响应局部化,构建了与振动响应局部化直接关联的表达因素。运用提出的方法分析了三自由度扇区单级叶盘集中参数模型谐调系统叶片刚度失谐时的敏感度特性,研究表明,随着失谐强度的增加,最大幅值放大系数逐渐增大,并在失谐强度上界处取得极值,并没有所谓的失谐"阈值"现象。

基于蚁群算法的航空发动机失谐叶片减振排布优化分析

在实际航空发动机叶盘结构中叶片失谐是不可避免的,并严重影响叶盘系统的振动特性和整个航空发动机的工作性能及使用寿命。通过分析得到对于一组既定的失谐叶片,其在轮盘上的安装排布顺序能很大程度上影响叶盘系统的振动情况,在此基础上,提出了一种新的振动局部化参数来表征失谐系统振动局部化程度大小,同时提出采用人工蚁群算法对叶片安装排序进行优化。研究表明:选择适当的叶片排布顺序可以有效降低叶盘系统受迫振动幅值、减轻系统振动局部化程度,同时也证明本文所采用的方法可行、有效。研究结果对降低叶盘系统振动幅度、减轻系统振动局部化具有重要意义。

失谐叶盘振动模态局部化定量描述方法

基于实际叶盘结构失谐振动模态局部化的基本特性和物理含义,提出了三种模态振型局部化程度三定量描述方法,并利用这三种模态局部化因子进行了典型叶盘结构失谐振动模态局部化程度的定量确定。讨论了典型叶盘结构失谐振动模态特性。分析说明和实例计算表明,相应的局部化因子计算过程简单、物理意义明确,可以有效定量确定实际叶盘结构的叶片失谐导致振动模态产生局部化的程度。

航空发动机失谐叶盘动态特性研究进展

航空发动机叶盘结构中不可避免存在的失谐会严重影响发动机的结构完整性和可靠性,国内外针对这一问题进行了大量深入的研究。详述了失谐叶盘建模、模型减缩、动态特性分析及评价等方面的研究现状,重点介绍多级叶盘和几何失谐叶盘的建模和动态特性分析等方面的最新研究进展,并对失谐叶盘未来研究方向进行了预测。

频率转向特征对失谐叶盘模态局部化的作用

基于叶盘集中参数模型,分析了叶片刚度失谐对频率转向区内的系统固有频率及叶片模态振型的影响,提出了一个描述模态局部化程度的参数,仿真研究了频率转向特征对失谐叶盘模态局部化程度的作用规律。研究表明,频率转向曲线之间关于节径的最小间隙(转向频率间隙)是反映频率转向特征的重要参数,并存在一个转向频率间隙的极小值点,在该极值点附近,频率转向区内的模态对叶片失谐非常敏感,并会导致模态局部化程度剧烈变化。