航空发动机主轴轴承局部故障激励机理与特征提取方法研究

Widely used in the modern aero-engine to transform the flight power, the main bearings are key components at several support points in the dual-rotor. The rotor vibrations produced by the thermal bending, unbalance, eccentricity, etc. are disturbing more and more prominently the condition monitoring and fault diagnosis of the main bearings, since the operation temperature and running speed of the dual-rotor are gradually increasing more and more higher. In this instance, starting at the point of the description of the localized fault with un-uniform shape, a rotor-bearing system dynamic model is proposed at first in this project in order to discuss the excitation mechanism of the localized faults such as the pitting, fatigue spalling and slip rub damage and reveal the effect law of these bearing faults on the dynamic characteristic of the rotor system. Then, the envelope analysis theory suitable for the multi-component signal is further improved and a signal decomposition method which can obtain the vibrations produced by rotor and bearing fault from only one single channel is proposed. Finally, by mastering the determination law of corresponding parameters, a feature enhancement and extraction method is proposed to adaptively solve the main bearing fault diagnosis in a complex environment involving even varying speed and interferences produced by the rotor thermal bending or unbalance. The research in this project will provide theoretical basis and technical support for the condition monitoring and fault diagnosis of the main bearing in aero-engine. The research results have significant theoretical and practical merit for enhancing the test level and operation stability of aero-engines in our country.

现代航空发动机普遍采用双转子多点支承方案，通过主轴轴承实现飞行动力的传递。随着发动机转子的工作温度和运行转速不断提升，转子热弯曲、不平衡等产生的振动对主轴轴承的状态监测与故障诊断的干扰越来越突出。鉴于此，本项目从表征轴承故障的非规则形貌出发，构建转子轴承动力学模型，探讨点蚀、疲劳剥落和滑蹭损伤等局部故障的激励机理，揭示轴承故障对转子系统动力学特性的影响规律。在此基础上，探索多分量信号的包络分析理论，提出基于单通道信号的转子、轴承故障振动成分分离方法；掌握复杂变速工况下轴承故障特征增强与提取过程中相关参数的优化选择规律，提出具有较好自适应性的主轴轴承故障特征提取方法，实现具有转子热弯曲、不平衡等振动干扰环境下主轴轴承早期微弱故障的诊断，为航空发动机主轴轴承的状态监测与故障诊断提供理论支撑和技术支持。研究成果对于提高我国航空发动机的测试水平和运行可靠性具有重要的理论和实用价值。

现代航空发动机普遍采用双转子多点支承方案，通过主轴轴承传递飞行动力，因此，主轴轴承关系发动机安全可靠运行的关键部件，其状态监测与故障诊断也一直是航空发动机研制的重点与难点。鉴于此，课题首先从轴承故障的实际形貌出发，采用引入随机数据数列模拟故障表面形貌的方法，建立了轴承的非规则故障模型。通过仿真与试验分析了缺陷长度、深度和粗糙度对于系统振动的影响。其次，参考典型的航空发动机转子系统，考虑了机匣运动、弹性支承、挤压油膜器产生的非线性油膜力、轴承间隙、滚珠与滚道之间的非线性赫兹接触力等因素影响，按照先局部后整体的方式建立了航空发动机双转子系统-滚动轴承-机匣的耦合动力学模型，研究了中介轴承出现非规则故障时的系统动力学特性。第三，建立了转子系统振动测试信号解析模型，推导了测试信号的包络表达式，将包络分析推广应用到多分量信号分析范围，揭示了转子偏心、弯曲、不对中以及齿轮啮合等确定性振动信号对轴承故障特征提取的干扰机理。在此基础上，采用迭代地减去信号/包络直流分量的方式，创造性地提出了基于Hilbert变换的迭代包络分析方法，实现了微弱轴承故障特征的提取。第四，以包络谱的相关峭度最大化为目标并根据信号频谱的包络极大值进行分段，提出了一种基于最大相关峭度解卷积与改进经验小波变换相结合的滚动轴承早期故障识别方法。第五，针对峭度易受大幅值异常数据或随机冲击干扰的问题，结合经验小波变换提出了线性峭度图方法。通过仿真与试验表明：线性峭度比峭度更适合表征信号的循环冲击特征，提出的线性峭度图方法具有更强的循环冲击特征提取能力。最后，推导了变转速工况下振动测试信号的包络表达式。结合低通滤波器设计、迭代包络分析与计算阶比跟踪方法，提出了适用于任意转速工况下的轴承故障特征增强方法，解决了变转速工况下的轴承故障特征提取与增强问题。