含涂层的航空发动机转子-机匣系统的碰摩故障研究

Rub-impact and vibration caused by it are not only an important issue for stability and safety of aero-engine but also a technical problem, which has been concerned by the scientists involved in the research of rotor dynamics. As one of important technical means for increasing the strength and service life of an aero-engine, the existence of coating gives rise to the difficulty of rub-impact force characterization to some extent. As for rotor-stator rub, the current studies focus on the dynamic characteristics of the rub rotor without surface coating. In the other hand, there is little literature about the effects of coating distribution and coating hardness on the rub-impact mechanism of rotor-stator and rub-impact response of fault system. Thus, this project will investigate the rub-impact mechanism of aero-engine with surface coating and the nonlinear dynamic characteristic of rotor-casing system. According to the operating environment of aero-engine, the influence of the coating softening caused by the temperature increment on the dynamic variation and frequency feature of the fault rotor system is discussed in the different condition of rub-impact. On this basis the inner relation between coating characteristic, structural parameter and rub-impact coupling fault, such as imbalance, axial preload, initial bowed shaft and pedestal looseness, will be further revealed. This work may be used to guide rub-impact fault diagnosis of aero-engine with surface coating.

碰摩以及由此引发的振动既是涉及航空发动机运行稳定性与安全性的重要问题，也是从事转子动力学研究的科学家们长期关注的技术难题。作为提高发动机结构件强度与延长其工作寿命的重要技术手段之一，涂层的使用在一定程度上造成了转-静子碰摩力表征的困难。针对航空发动机的碰摩问题，目前的研究多分析无涂层情况下碰摩转子的动力学特性，而部件表面上涂层的分布和涂层的软硬程度等因素对转-静子碰摩机理及故障系统的非线性振动响应的影响尚不清楚。由此，本项目将对含涂层的航空发动机碰摩机理及转子-机匣系统的非线性动力学特性展开研究。结合其实际工作环境，讨论温度升高引起的涂层软化对不同碰摩形式下故障转子的动态变化和频谱特征的影响规律。在此基础上，进一步揭示涂层特性、结构参数与不平衡、轴向预紧力、转轴初始变形、支座松动等碰摩耦合故障间的内在联系。所得结果以期为含涂层的航空发动机碰摩故障诊断提供理论指导。

为提高航空发动机效率、降低燃油消耗，转静子之间普遍采用小间隙设计。然而，过小的叶尖间隙，加之柔性结构设计和附加较大载荷，使得转静子碰摩风险大大增加，将对结构件造成不容忽视的损伤。再者，涂层技术作为“两机”关键零部件制造的核心技术之一，对推动我国制造水平起到举足轻重的作用。截至目前，尚缺乏对含涂层的转静子碰摩机理及动态特征的合理认识。为此，本项目围绕涂层影响下转静子碰摩机理及碰摩转子非线性动力学特性两方面进行研究工作。通过理论分析和实验研究相结合的方式，探究了软/硬涂层在不同接触形式下的等效刚度，从而厘清接触形式和碰摩侵入深度对含涂层的转静子碰摩机理的影响规律。另一方面，在转子动力学和非线性动力学的理论体系下，研究涂层影响下碰摩转子系统的非线性动态特征，揭示系统响应随全周碰摩、偏摩、定点碰摩等故障形式的演变规律。同时，针对转盘不平衡、转轴初始弯曲、止推轴承轴向预紧力、支座松动等典型故障，借助分岔图、时间历程曲线、瀑布图、轴心轨迹图、相图等分析工具，分别研究了各类故障对涂层转子系统动力学行为的影响机制，建立了故障类型和系统响应之间的关联性。此外，为了验证理论分析和数值仿真的有效性，本项目基于搭建的转子实验台分别开展了碰摩机理和故障响应的实验研究工作。以转子实验台转速、支座螺栓松动程度、转盘不平衡配重等为控制参数，从时域和频域角度实验研究了多类故障系统的振动行为，进一步加深了对非线性故障系统的机理性认识。