【作者】 蒋熙馨；

【导师】 周祖德；

【作者基本信息】 武汉理工大学 ， 机械制造及其自动化， 2014， 博士

【摘要】 以航空发动机为代表的叶片类旋转机械是工业领域一类重要装备,随着科学的发展、技术的进步、效率的提高,此类装备不断向大型化、高速化、柔性化发展。叶片作为功能转化的核心,所承受的单位负载不断增加,设计安全系数甚至达到1。这种情况下,对旋转叶片实时、在线的检测、监测手段成为提高装备性能、可靠性的关键。光纤光栅(FBG)是一种新型光学应变传感器,具有质量轻、体积小、一线多点、分布式测量、抗电磁干扰、光信号可在空气中传输的特点。利用FBG传感器的这些特点,可对旋转叶片的动应变及相关参量进行测量,可满足旋转叶片在空间狭小、高速旋转、高温、高压等苛刻工况条件下的测量要求,对加深高速旋转叶片力学行为的认识,提高我国叶片类旋转机械的研究、设计、分析、加工、制造水平都具有重要意义。同时,旋转也是工业装备的普遍特征,此项研究也可推广至通用装备的旋转部件测量,提高对所有具备旋转特征的工业装备的认识,对提高这些工业装备的研究、设计、分析、加工、制造水平都具有重要意义。本文首先建立了航空发动机旋转叶片动应变测量的方法。介绍了FBG应变测量的原理,利用FBG光信号可在空气中传输的特性,分析了旋转叶片上FBG应变测量信号传输的几种方法,在此基础上选择C-LENS透镜法进行了深入分析,并基于分析的结果利用两个C-LENS透镜进行了实验。实验结果表明,C-LENS透镜法可在旋转轴端跳动最大0.8mm的工况下传输光信号。但C-LENS透镜法对旋转轴夹角的变化非常敏感,最终实验装置在最大4000r/min下实现了旋转部件动应变FBG检测光信号的传输。随后,通过分析动应变与振动间的关系,提出通过旋转叶片动应变估计旋转叶片振动的方法。由弹性力学、动力学的基本理论,任意结构的强迫振动方程均可利用假设模态法近似求解,各阶模态可视为强迫振动方程解空间的基,则不同位置振动可用振动体各阶模态的组合或振动方程解空间的基来逼近,而不同模态在不同位置的名义应变是唯一的,从而通过动应变可估计旋转叶片的振动情况；然后,将变截面、变厚度、预扭曲的旋转叶片简化为旋转等截面梁,将旋转等截面梁简化为静态等截面梁,依次求解等截面悬臂梁、旋转等截面悬臂梁、旋转叶片动应变→振动的方程。以动应变→振动理论分析和旋转信号传输的实验工作为基础,分别测试了等截面悬臂梁、旋转等截面悬臂梁、某型发动机二级动叶片旋转态的动应变,并分析了实验结果,估计了实验对象的振动。其中针对某型发动机二级动叶片旋转态的动应变的测试结果表明,存在一个频率簇,此频率簇对发动机的动态响应特性有非常大的影响,应在设计中予以充分的考虑。在研究单个旋转叶片的动应变后,得益于FBG一线多点、分布式测量的优点,测量了两个叶片8个点的动应变。从多个叶片/轮毂组成的系统的角度出发,实验研究了旋转态叶片——轮毂系统的振动特性,指出由于加工误差、安装误差、磨损程度的不一致,叶片——轮毂系统不可简单视为循环对称结构,从循环对称的特征出发建立模型将导致计算结果的偏差,错误的估计安全系数,导致重大安全隐患。更多还原

【Abstract】 Blade-like rotating mechanical is the core equipment in the field of industry. Along with the development of science, advancement of technologies and improvement of efficiency, this kind of equipment is developed continuously with a trend toward large scale, high speed and flexibility. The blade, as the core component of equipment, bored enormous unit load and the design safety factor even reaches1. In this case, the real-time and online detection and monitoring means of rotating blade becomes the key to improve equipment performance and reliability.The optical fiber bragg grating (FBG) is a kind of optical sensor and a strain measurement sensor characteristic of light weight, small volume, one line with multiple points, distributed measurement, electromagnetic interference resistance, optical signal transmission in the air. These characteristics of the FBG sensor could be utilized in measuring the dynamic strain and related parameters of rotating blades, meeting the requirements of rotating blade measurement under the extreme conditions like narrow space, high-speed, high temperature and high pressure, which is significant for understanding the mechanical behavior of the high-speed rotating blade and improving China’s blade-like rotating equipment research, design, analysis, processing and manufacturing level.In the meanwhile, rotating is a common feature of industrial equipment. This study can also be extended to the measurement of rotating parts of common equipment and improve knowledge of all industrial equipment with rotating feature, which is significant for improving the research, design, analysis, processing and manufacturing level of the industrial equipment.Firstly, the measurement method of rotating blade’s dynamic strain of jet engine is established.Based on the characteristics of optical signal can transmit in the air, the author analyzes several transmission methods of FBG signal on the rotating blade, and select the C-LENS lens method as further analysis, and design experiments by using two C-LENS lens based on the analysis results. The results show that the optical signal could be transmitted under the condition of maximum rotating shaft end run-out of0.8mm by using the C-LENS lens method. However, the C-LENS lens method is very sensitive to the variation of the included angle of rotating shaft. The result shows the dynamic strain of rotating component can transmit under the condition of4000RPM. A patent is applied for based on these studies.Subsequently, the relationship between the dynamic strain and vibration is analyzed in this paper. The equation of rotating blade’s dynamic strain→vibration is established. According to the basic theories of the elastic mechanics and dynamics, approximation solution of the forced vibration equation of any structure can be obtained by using the assumed mode method. Dynamic strain at different positions can be regarded as the solution of forced vibration equation at this point; each mode can be regarded as the base of solution space of forced vibration equation; then, dynamic strain at different positions can be approximated by the modal combinations of vibrating body or the bases of solution space of vibration equation so as to estimate the vibration status of the rotating blade. Then follow the route from complexity to simplicity/from simplicity to complexity to simplify the pre-twisted rotating blade of variable cross section and variable thickness to the constant cross-section rotating beam and simplify the constant cross-section rotating beam to the constant cross-section static beam, which solve the equations of constant cross-section cantilever beam, constant cross-section rotating beam and rotating blade dynamic strain→vibration in theory. Dynamic strain of constant cross-section cantilever beam, constant cross-section rotating beam and secondary rotating blade of some model of jet engine under rotating status is tested respectively on the basis of theoretical analysis of the dynamic strain→vibration and experiments of rotating signal transmission, and experimental results are analyzed to estimate the experimental subject. Among which, the result of testing the dynamic strain of secondary rotating blade of some model of engine under rotating status indicates that a frequency cluster exists and this frequency cluster has significant influence on the dynamic characteristics of the engine and should be fully taken into account in the design.After the study on the dynamic strain of single rotating blade, dynamic strain at eight points of two blades are measured by utilizing FBG’s advantage of one line with multiple points and distributed measurement. The vibration characteristics of the rotating blade/hub system are studied through experiment from the point of a system consisting of multiple blades/hubs. It points out that the blade/hub system could not be regarded as a cyclic symmetric structure simply due to the inconsistency of machining error, installation error and degree of wear. Model building based on the cyclic symmetric feature will result in deviation of the calculation results, erroneous estimation of the safety factor and significant security hazards.更多还原