基于机匣加速度信号的航空发动机转静碰摩部位识别

提出了基于机匣加速度信号的航空发动机转静碰摩部位识别方法。利用航空发动机转子试验器模拟了大量不同部位的碰摩,将小波局部极大模归一化能量与直接提取的机匣加速度信号归一化均方值输入至支持向量机中,以进行识别验证及对比分析。结果表明,小波局部极大模方法提取的归一化能量特征比直接提取的加速度信号均方值能更加有效地进行转静碰摩部位的识别。     

结合复小波包变换及频谱校正的机械转子碰摩故障诊断方法研究

针对机械转子系统中碰摩故障发生时故障特征微弱及识别困难的问题,提出一种结合双树复小波包变换及频谱校正的故障诊断方法。首先对于振动位移信号中工频基波成分,采用频谱加矩形窗的频谱校正方法识别其谐波信息,通过构造补偿信号进行对消,以减少其对后续特征提取的影响。其次通过双树复小波包对补偿过的信号进行多尺度分解;最后对小波包子空间信号进行希尔伯特包络解调分析,通过瞬时幅值及瞬时频率信息诊断转子的动静碰摩故障。在转子实验台上进行了实验验证,结果表明提出的方法能有效提取转子碰摩产生的微弱故障特征。     

基于谐波分量的转子系统碰摩故障定量诊断方法

提出一种利用碰摩转子系统响应中的高次谐波分量进行碰摩位置和碰摩力定量诊断的新方法。基于谐波平衡理论分析碰摩故障转子系统的动力学特性,证明了碰摩故障转子系统中任意两节点之间高次谐波分量之比等于无故障转子系统频率响应矩阵的相关元素之比。根据此关系,提出转子系统碰摩故障模型诊断方法和步骤:利用正常转子系统与故障转子系统响应的任意一阶谐波分量之差,结合转子系统的动力学模型,就可以诊断出碰摩的位置;进而可以根据故障转子系统响应的各次谐波分量还原出碰摩力分量。为验证该方法的有效性,对一转子系统进行偏碰和整周碰摩时的数值仿真,并分析支撑刚度及噪声对诊断方法的影响;又在模型转子试验台上进行了试验。该方法仅利用一个转速下两个节点的振动响应即可实现碰摩故障的在线定量诊断,因此便于在实际旋转机械上实行。     

双转子-支承-机匣耦合系统碰摩振动响应分析及试验验证

以某型航空发动机双转子试验器为研究对象,采用Newmark-β数值积分方法求解系统的动力学响应,在考虑高低压转子中介轴承的耦合和机匣的弹性变形及其运动的基础上,建立了碰摩故障双转子-支承-机匣耦合系统动力学模型,理论分析了转速、转子偏心量和碰摩刚度对转子系统动力学特性的影响并进行了相关试验。研究结果表明：发生碰摩故障时,转子和机匣测点频谱分析图中会出现转子的倍频和组合频率,可将其作为判断系统发生局部碰摩的特征信号;随着转子偏心量和碰摩刚度的增大,碰摩幅值响应愈加明显,碰摩程度亦愈加严重;机匣测点振动量值存在衰减,后续理论建模过程中应考虑传递过程的衰减。本研究结论可为碰摩故障机理的探究和碰摩故障的诊断提供参考。     

基于传递路径的多级齿轮箱齿轮裂纹故障识别

采用集中参数法对多级齿轮传动系统的齿轮振动进行建模仿真,获得难以直接测量的齿轮箱内部振源振动信号。根据系统辨识理论,获得振源信号传递至2个不同测点下传播路径的传递函数。通过比较2测点在同种系统状态下对应的信号传播路径的传递函数特征,选取了更能反映系统振动特征的测点作为最佳测点。通过比较无故障状态与定轴齿轮齿根裂纹状态下最佳测点对应的信号传播路径的传递函数特征,找出系统刚度微小变化时传递函数的变化特征,从而能够以此辅助判断微弱故障类型。     

薄壁回转体表面岛屿状高凸台结构旋印电解加工成形过程研究

以航空发动机机匣为代表的薄壁回转体表面分布有大量岛屿状的高凸台结构，此类零件普遍存在加工变形大、刀具损耗严重等制造难题。旋印电解加工采用回转体工具电极，通过工件与工具的同步对转实现阳极材料的逐层均匀溶解，对于机匣等薄壁回转体零件加工具有独特优势。开展了旋印电解凸台成形过程的仿真研究，建立了电极等效运动分析模型和阳极溶解数学模型，掌握岛屿状高凸台结构旋印电解加工成形规律。仿真结果表明，阴极进给深度和窗口宽度对凸台轮廓形状有着很大的影响。随着阴极工具的不断进给，阴极窗口运动轨迹的包络线逐渐由尖锥形变为纺锤形，凸台侧壁锥度不断减小，呈现从正锥形→垂直→倒锥的变化趋势。阴极窗口宽度的增加会导致窗口运动轨迹倾斜角度增大，有利于获得锥度较小的凸台侧壁轮廓。对于任意阴极窗口宽度的凸台侧壁轮廓均可以通过某一宽度的轮廓通过角度旋转偏置获得。此外，旋印电解加工间隙呈现出非平衡态变化趋势。在仿真分析的基础上，进一步开展了旋印电解加工试验研究，在镍基合金GH4169薄壁回转体表面加工出岛屿状高凸台结构。试验结果表明旋印电解加工技术对于具有较大高度复杂异形岛屿状凸台结构的薄壁回转体零件具有较好的加工能力。     

Gear fault detection and diagnosis under speed-up condition based on order cepstrum and radial basis function neural network

Varying speed machinery condition detection and fault diagnosis are more difficult due to non-stationary machine dynamics and vibration. Therefore, most conventional signal processing methods based on time invariant carried out in constant time interval are frequently unable to provide meaningful results. In this paper, a study is presented to apply order cepstrum and radial basis function (RBF) artificial neural network (ANN) for gear fault detection during speedup process. This method combines computed order tracking, cepstrum analysis with ANN. First, the vibration signal during speed-up process of the gearbox is sampled at constant time increments and then is re-sampled at constant angle increments. Second, the re-sampled signals are processed by cepstrum analysis. The order cepstrum with normal, wear and crack fault are processed for feature extracting. In the end, the extracted features are used as inputs to RBF for recognition. The RBF is trained with a subset of the experimental data for known machine conditions. The ANN is tested by using the remaining set of data. The procedure is illustrated with the experimental vibration data of a gearbox. The results show the effectiveness of order cepstrum and RBF in detection and diagnosis of the gear condition.     

航空发动机系统复杂管路结构振动特性

针对高速运转带来的处于高温环境、狭小空间内复杂管路不平衡振动问题,开展航空发动机系统复杂管路的结构振动特性研究。从系统直管和弯管结构振动特性分析提出复杂管路结构数值建模方法,并基于航空发动机复杂管路一般具有对称的结构特点,对系统复杂管路从总体结构和径向结构角度开展振动特性分析与结构优化。分析结果表明:作为轴对称复杂管路结构,3个对称加载的总体结构呈现刚体模态,而20°的管路径向结构在基本加载下振动变形集中于异面支管,且总管增加不同载荷对其结构变形减小无正向影响,故从运行角度为狭窄空间内管路设置结构限制条件,有助于减少系统复杂管路运行故障的发生。     

改进PCA算法及其在转子特征提取中的应用

为探索航空发动机轴承装配条件对支承刚度的影响,支撑发动机转子系统的动力学设计和整机振动控制,在动力学方程的基础上,建立了振动测试和理论计算相结合的支承刚度辨识方法,并以某型航空发动机的五号支点轴承为对象,试验研究了圆柱滚子轴承内、外环配合参数、锁紧螺母拧紧力矩等参数对支承刚度的影响规律。结果表明：建立的支承刚度辨识方法准确可行;轴承内、外环为过盈配合时,过盈量增大,支承刚度增大,支承刚度对锁紧螺母拧紧力矩不敏感;轴承内、外环为间隙配合时,转子出现非线性共振,支承刚度大幅度地随机跳动,不符合线性条件假设。设计时应合理考虑轴承内、外环配合参数,避免导致转子系统振动特性恶化。     

混响系统源波形间接恢复的研究

多源非平稳冲击激励、时变的传递路径、宽频非平稳振声响应以及混响、消散、模态密集等现象 ,是发动机、柴油机等混响系统的重要特性 ,制约着激励源波形和故障信息的直接测取 ,使利用包容着激励源特征和路径因素的振动响应间接恢复源波形的研究思路成为当前的研究热点。本文对制约混响系统源波形间接恢复的主要动力学特性——混响与消散进行了深入的理论分析和探讨 ,提出了基于非精确传递函数以最佳傅里叶滤波与复倒谱相结合的激励源波形间接恢复方法。气缸缸套试验验证了该方法的有效性     

Weak fault detection method of rolling bearing based on testing signal far away from fault source

In some cases, because of the complex internal structure of the machines, the positions of the vibration sensors are far away from the rolling bearings, such as in an aeroengine, causing the fault features to become extremely weak, which brings great challenge to the detection of rolling bearings. To address this problem, an integrated detection method is proposed. First, a method named MEDL is proposed to determine the optimal filter length in minimum entropy deconvolution (MED) to enhance the periodic fault impulse component in the weak signal, which accuracy is 1. After that, the MEDL is combined with variational mode decomposition (VMD) and autocorrelation to extract fault features from strong background noise. A series of fault simulation experiments for rolling bearings were conducted by using an aeroengine rotor experimental rig with casing. The results verify that the accuracy of the integrated detection method is 100 % in different measuring points, speeds and fault types. At the same time, it compared with spectral kurtosis (SK) and empirical wavelet transform (EWT). It proves that the integrated detection method is more robust in extracting the weak fault characteristic of rolling bearings from the casing signals effectively.     

松动-碰摩发展过程中的非线性慢变问题

利用非线性动力学及转子动力学,建立了一个松动发展的模型,对松动发展的不同阶段进行振动试验,找出了转子系统发生支承松动和碰摩的特点和规律。     

钻柱信道中声信号传输的接收特性分析

针对周期性管结构信道特征,构建钻柱内一维低频纵波传输的有限差分模型,应用单个加速度传感器作为声接收器,在时、频域仿真分析了换能器接收位置对声信号传输特性的影响规律。在此基础上,考虑信道内多重回波对声通信信号检测的影响,基于信道容量的分析,引入上、下行信道的单位脉冲激励响应,设计了一种基于双声接收器模式的回波噪声抑制方法,并利用倒频谱解析算法,求解接收信号中的回波信息,分析了单、双接收器工作模式下信道响应特征。数值仿真结果表明,双接收模式可有效抑制井下回波噪声,改善信噪比,从而实现更佳的信道接收性能。     

某型航空发动机轴承环下润滑结构试验

以某型航空发动机轴承环下润滑结构为基础开展了轴承环下润滑结构的试验。通过对试验轴圆心位置在轴向集油环端面内侧和外侧2种方案试验对比发现,在内侧时改进润滑油入射点位置和集油腔空间后,试验过程中轴承温度和箱体振动变化平稳,试验后轴承未出现由于润滑不良而失效的情况。     

大型轴流压缩机焊接机壳的动态特性分析

根据轴流压缩机的运行特性及工况条件,用有限元法对大型轴流压缩机焊接机壳进行了动态特性分析,获得了机壳的各阶固有频率和振型,明确了焊接机壳的薄弱环节.通过热稳态及瞬态动力学有限元分析,得到了焊接机壳的温度、应力和变形分布云图,以及危险区域的瞬态应力和变形曲线.提出了焊接机壳的改进方案,通过分析比较取得了改进参数,并验证了其合理性.     

Study on Influence of Cylinder Liner Surface Texture on Lubrication Performance for Cylinder Liner–Piston Ring Components

A marine diesel engine, where the cylinder liner–piston ring (CLPR) pair is one of the most important rubbing pairs, is the heart of a marine system. Studying the lubrication characteristics of the CLPR will provide a guide for rational design of the CLPR to reduce wear and prolong its service life. The surface texture features have a significant impact on the lubricating performance of the CLPR. In this study, the tribological system of the CLPR was investigated. Different surface textures (such as different sizes of surface concaves and grooves, etc.) were designed and produced on the cylinder liners using surface treatment. A series of experimental tests were then carried out in a specially designed diesel engine tester to investigate the tribological characteristics of the treated CLPR pairs. The comparison analyses of the worn surface texture features, element content of the lubrication oil, and abrasive particle characteristics were conducted under different wear surface texture features and cylinder liner speeds. The analysis results showed that there were significant differences in the tribological and lubrication properties of the rubbing pairs in different wear surface texture features. The wear performance of the CLPR pair with a regular concave texture was superior to that of the concave and groove, and regular groove textures. In addition, the regular concave with a depth-diameter ratio of 0.1 was the most effective surface texture to improve the lubrication and wear properties of the CLPR pairs. It is believed that the knowledge obtained in this study provides the real practical basis for tribological design and manufacturing of CLPR pair in marine diesel engines.     

Experimental study on the mean flow characteristics of forward-curved centrifugal fans

Measurements have been made in an automotive HVAC blower for two different centrifugal fans. This work is directed at improving the performance of a conventional forward-curved centrifugal fan for a given small blower casing. Mean velocities and pressure have been measured using a miniature five-hole probe and a pressure scanning unit connected to an online data acquisition system. First, we obtained the fan performance curves versus flow rates showing a significant attenuation of unstable nature achieved with the new fan rotor in the surging operation range. Second, aerodynamic characterizations were carried out by investigating the velocity and pressure fields in the casing flow passage for different fan operating conditions. The measurements showed that performance coefficients are strongly influenced by flow characteristics at the throat region. The main flow features were common in both fans, but improved performance is achieved with the new fan rotor, particularly in lower flow rate regions. Based on the measured results, design improvements were carried out in an acceptable operation range, which gave considerable insight into what features of flow behavior were most important.     

ICA在航空发动机振动信号盲源分离中的应用

研究了基于独立分量分析(independent component analysis,简称ICA)的发动机振动信号盲源分离技术,旨在将发动机振动信号按照不同的激振源进行分离。首先阐述了基于最大信噪比的盲源分离算法原理,通过对仿真信号进行分离,判断了分离输出信号与仿真信号的一致性,验证了该算法的可行性;然后将该算法与FFT分离法相结合,应用于某型双转子航空发动机高、低压转子实测振动信号盲源分离中,取得了很好的分离效果,表明应用ICA技术建立的基于最大信噪比的盲源分离算法具有迭代次数少、计算复杂度低、效果好及稳定等优点。     

散斑运动模糊复原的直线电机动子位置检测

图像测量技术具有非接触性、抗干扰性等优点被越来越多地应用到双次级永磁直线电机动子位置检测中。针对图像采集过程中所产生的图像模糊问题,提出了一种精确辨识运动模糊参数的方法,实现了直线电机动子位置的精确测量。采用数字散斑图像作为原始拍摄面,通过相机获得包含动子位置信息的序列运动模糊图像。利用奇异值分解对运动模糊图像进行去噪重构预处理,降低噪声对运动模糊参数辨识精度的影响。求取预处理后图像的倒谱图,通过主成分分析找到倒谱图二值化后亮线的主矢量方向即为模糊方向;同时作出倒谱三维图,利用其负峰值中两个最小值坐标求出模糊长度。根据计算的模糊参数值复原模糊散斑图像,再利用图像亚像素测量方法获得动子位置。实验结果表明:本文算法的计算耗时比Radon算法缩短了5倍多,不同位移下的平均绝对误差仅为0.084 7mm,满足直线电机动子位置检测的实时性和高精度要求。     

转子接触摩擦故障的模糊诊断（一）：模糊诊断方法与模拟试验

本文从转子发生碰摩时产生的振动信息特征出发,分析了碰摩产生振动量的机量;确认由于这类故障的振动征兆的不确定性,从而采用模糊数学方法来识别故障的可行性.文章介绍了一种新的碰摩故障模拟试验系统及试验结果,对是否出现碰摩故障、碰摩的程度和碰摩的位置进行了模拟试验与诊断.