刷式密封的泄漏量显著低于篦齿密封，还具有振动适应性高、耐高温等优点，刷式密封越来越被广泛地应用于航空发动机以及燃气轮机关键部位的密封中，成为航空发动机中典型的高温动密封结构。刷丝尖端与跑道涂层的磨损是刷式密封性能衰减的主要因素，同时使用经验表明刷丝之间的磨损及刷丝与背板间磨损会导致长时间运转后刷丝变细甚至断裂。高温高速的工况条件对刷式密封的泄漏及磨损行为影响显著，因此研究高温高速工况下刷式密封的泄漏性能、接触状态及磨损行为日益迫切。本文为模拟刷式密封高温高速工况，提出了基于电磁感应加热原理的刷式密封高温高速实验平台设计方案，通过红外测温及反馈调节实现温度准确控制，通过设计陶瓷球轴承和陶瓷垫环隔绝感应电流，依次完成了原理分析、结构设计、强度校核、加工装配及调试验证工作，成功实现了跑道温度800 ℃、线速度100 m/s的性能指标，成功地在实验平台上开展了刷式密封高温高速泄漏和磨损实验。本文结合搭建的刷式密封实验平台结构与工况参数，进一步发展了刷式密封三维切片仿真模型，实现了流固热耦合计算，研究了刷丝和跑道之间的间隙变化以及跑道温度对密封性能的影响，对转子离心胀大和泄漏间隙、泄漏量之间的联系进行了定量的仿真分析；建立了考虑热变形的刷丝接触模型，分析了转子热膨胀对跑道和刷丝之间接触状态的影响。本文对建立的刷式密封三维切片模型进行了实验验证。实验结果表明，当线速度达到100m/s水平时，转子的离心胀大行为便会对密封性能产生显著影响，考虑离心胀大和间隙变化的泄漏量仿真计算结果与实验结果的误差不超过7%（无间隙模型计算结果与实验结果误差超过50%）；温度对泄漏量的影响很大，空气泄漏量随跑道的温度的升高会显著降低，计算值与实验值的最大误差为12%。实验结果证明了高速高温工况仿真分析的正确性。本文在搭建的实验平台上进行刷式密封刷丝尖端与跑道涂层的高温高速磨损实验，总结了不同温度下刷丝尖端的摩擦磨损机制，发现了刷丝尖端在高温工况下的熔焊现象；本文还在SRV-5标准摩擦磨损试验机上进行刷丝微动磨损实验，初步总结了在不同压差（加载力）与温度下的刷丝微动磨损机制。
The leakage of brush seals is significantly lower than that of comb seals, and it also has the advantages of high vibration adaptability and high temperature resistance. It is frequently used in the sealing of key parts of aero-engines and gas turbines, and it becomes a typical high-temperature dynamic seal structure in aero-engines. The wear between the tips of the brush bristles and the coating of the racetrack is the main factor of the degradation of the brush seal performance. At the same time, experience shows that the wear between the bristles and the wear between the bristles and the back plate will cause the bristles to become thin or even break after long-term operation. The high-temperature and high-speed working conditions have a significant influence on the leakage and wear behavior of the brush seal. Therefore, it is essential to study the leakage performance, contact state and wear behavior of the brush seal under high-temperature and high-speed working conditions through experiments.Aiming at the realization of high-temperature and high-speed working conditions of brush seal, an idea of test platform designing based on the principle of electromagnetic induction heating is proposed. The temperature is accurately controlled through infrared temperature measurement and feedback adjustment, and induced current is isolated by ceramic ball bearings and ceramic backing rings. The principle analysis, structural design, strength check, processing and assembly and debugging verification have completed in sequence. The platform successfully achieved the performance indicators, rotor temperature up to 800 ℃ and linear velocity up to 100 m/s. And the high temperature and high speed leakage and wear test was successfully carried out on the experimental platform.The research further developed the three-dimensional slice simulation model of the brush seal based on the structure and working condition parameters of the brush seal experiment platform built. The fluid-solid-heat coupling calculation was realized, and the effect of the gap change between the brush bristles and the rotor and the temperature on the seal performance was studied. The relationship between the leakage gap (influenced by the centrifugal expansion of the rotor and) and leakage was quantified by simulation analysis; And the brush bristle contact model considering thermal deformation was established, in which the impact of the thermal expansion of the rotor on the contact between the racetrack and the brush bristles was analyzed.In the research, the established three-dimensional slice model of the brush seal was experimentally verified. The experimental results show that when the linear velocity reaches 100m/s, the centrifugal swelling behavior of the rotor will have a significant impact on the sealing performance. The error between the leakage simulation calculation results and the experimental results considering the centrifugal swelling and gap changes is not more than 7% (The error between the calculation result of the gapless model and the experimental result exceeds 50%). The temperature has a great influence on the leakage, and the air leakage will decrease significantly with the increase of the temperature of the rotor. The maximum error between the calculated value and the experimental value is 12%. The experimental results prove the correctness of the high-speed and high-temperature simulation analysis.In this research, high-temperature and high-speed wear experiments on the tip of the brush bristles and the rotor coating was carried out on the experimental platform, and the friction and wear mechanism of the bristles tip under different temperatures was summarized. The fusion welding phenomenon of the brush wire tip under high temperature conditions was discovered. The research also conducted the fretting wear experiment of the brush filament on the SRV-5 standard friction and wear testing machine, and preliminarily summarized the fretting wear mechanism of the brush bristles under different pressure differences (loading force) and temperature.
