干气密封是一种依靠端面螺旋槽产生的动压效应实现非接触运转的机械密封，因其运行无损耗、工作可靠性高、使用寿命长等优点，广泛应用于石油石化、航空航天等领域。但因干气密封失效事故频繁，对密封端面状态进行实时化、精确化的监测，对密封乃至整个主机装备的安全稳定运行具有极其重要的意义。本文以基于声发射技术的干气密封状态监测为主要研究对象，通过数值仿真和实验测试相结合的方法，对导致密封端面接触和损伤的两种典型工况——具有连续性接触摩擦特征的多次启停工况及具有短时轻微接触摩擦特征的压力突变工况条件下，密封端面摩擦磨损和性能劣化的发生发展规律及其机理开展了研究。通过构建密封界面微间隙流场、固体变形模型，以及界面参数传递和耦合迭代关系，建立了密封端面的流固耦合模型，研究了干气密封在启动过程中的膜厚、变形的密封状态，及颗粒堆积等状态劣化对密封性能的影响规律；通过瞬态密封流场和密封环动力学模型，形成了密封补偿环的动特性分析方法，研究了在外部干扰时密封端面的接触状态变化，及动环偏摆和静环所受力矩对密封抗干扰能力的影响。数值仿真模型的建立为密封的劣化过程实验研究提供了理论基础。通过声发射监测的标准摩擦磨损实验，研究了碳化硅、谈石墨等典型密封材料的声发射信号特征，及材料磨损过程声发射信号的变化。在此基础上开展了干气密封多次启停条件下的声发射监测实验，发现在声发射能量信号表征下，随着启停次数的增加，干气密封劣化过程具有明显的磨合段、稳定工作段、过渡段、严重磨损段的四阶段性特征，而声发射开启转速和全速阶段能量可以作为评价密封端面状态的指标。结合数值仿真和端面检测，分析了各阶段密封端面接触的典型特征，获得了密封性能在反复启停过程中的发生性能劣化的内在机理。通过干气密封压力突变实验，研究了压力变化造成的端面轻微接触状态下，声发射信号特征和监测方法的有效性。发现在由压力突变等造成的端面轻微接触情况下，气流的声发射信号也构成端面声发射信号的重要来源之一，且在低频信号中的占比较重。通过声发射信号接触特征频率带能量的占比追踪，可以清晰地显示密封端面不同的接触状态。进一步结合密封动力学模型仿真，分析获得了压力突变情况下密封端面接触的发生和信号特征变化机理。
Dry gas seal is a mechanical seal that achieves non-contact operation by relying on the dynamic pressure effect generated by the end face spiral groove. Due to its advantages of no loss during operation, high reliability, and long service life, it is widely used in fields such as petroleum, petrochemical, and aerospace. However, due to frequent failures of dry gas seals, real-time and accurate monitoring of the seal face condition is of great significance for the safe and stable operation of the seal and the entire host equipment. This article mainly focuses on the state monitoring of dry gas seals based on acoustic emission technology. Through the combined method of numerical simulation and experimental testing, the development rules and mechanisms of seal face friction wear and performance degradation under two typical working conditions that cause seal face contact and damage are studied: the multi-start-stop working condition with continuous contact friction characteristics and the pressure fluctuation working condition with short-term slight contact friction characteristics. By constructing a micro-gap flow field model of the sealing interface, a solid deformation model, as well as the interface parameter transfer and coupling iteration relationship, a fluid-solid coupling model of the sealing face is established to study the sealing state of membrane thickness and deformation during the start-up process of the dry gas seal, as well as the influence of state deterioration such as particle accumulation on sealing performance. By analyzing the dynamic characteristics of the sealing compensation ring using transient sealing flow field and sealing ring dynamics model, this study investigates the changes in the contact state of the sealing face when subjected to external disturbances, as well as the influence of dynamic ring offset and static ring torque on the sealing‘s anti-interference ability. The establishment of a numerical simulation model provides a theoretical basis for experimental research on the degradation process of the seal.Standard friction and wear experiments were conducted using acoustic emission monitoring to study the acoustic emission signal characteristics of typical sealing materials such as silicon carbide and carbon graphite, as well as the changes in acoustic emission signals during material wear. Based on this, acoustic emission monitoring experiments were carried out under the multiple start-stop conditions of dry gas seals. It was found that, characterized by the energy signal of acoustic emission, the degradation process of dry gas seals has a four-stage characteristic of running-in, stable operation, transition, and severe wear with increasing number of start-stops, and the opening speed and full-speed stage energy of acoustic emission can be used as indicators for evaluating the seal face status. Combined with numerical simulation and surface inspection, the typical characteristics of seal face contact in each stage were analyzed, and the intrinsic mechanism of performance degradation during repeated start-stop processes of seal performance was obtained.Through dry gas seal pressure fluctuation experiments, the effectiveness of acoustic emission signal characteristics and monitoring methods were studied under the condition of slight contact between seal faces caused by pressure changes. It was found that, under slight contact conditions caused by pressure fluctuations, the airflow acoustic emission signal also constitutes an important source of seal face acoustic emission signal, with a relatively heavy proportion in the low-frequency signal. By tracking the proportion of energy in the contact characteristic frequency band of the acoustic emission signal, different contact states of the seal face can be clearly displayed. Further combined with sealing dynamic model simulation, the mechanism of seal face contact occurrence and signal feature changes under pressure fluctuation conditions were analyzed and obtained.
