燃气透平动密封磨损变形过程中的热流固耦合机理和流动传热特性研究

In this study, numerical methods, theoretical analysis and experimental tests are ultilized to investigate the flow, heat transfer and rub mechanism of the dynamic seals in gas turbine engines. The thermal-fluid-structure interaction model involved with rub, structure deformation and conjugate heat transfer are established for the dynamic seals operating in high temperature and high speed conditions during the seal rotor and stator contacting process. The codes based on CFD/FEA theories, as well as the corresponding analytical system, are developed and validated with the obtained experimental data. A test rig, which is aiming at obtaining the multi-physical parameters, is also established to visualize the transient flow field, measure the heat transfer coefficient distributions and reveal the rub mechanism of the non-contacting dynamic seals in realistic operation conditions. The rub and deformations of the clearance surfaces, as well as the conjugate heat transfer characteristic in the dynamic seals during contacting process are investigated with the experimental tests and analysis system. Moreover, the influence of seal structure deformation, which is indued by the transient fluid forces and thermal stress, on the flow and heat transfer characteristics are studied. The rub meachanism and performance degradation under different geometrical parameters, material properties and operation conditions are systematically investigated. The relations between the rub damage, heat transfer performance and unsteady leakage flow are revealed. The transient variations of the seal structure deformation,local metlting, rubbing and heat transfer during the contacting process are also analyzed in detail. This project will provide an effective foundamental basis for designing the advanced dynamic seals in the gas turbine engine, and it is profitable for enhancing the cooling effect and safety operation of the dynamic seal in high speed and high temperature environment.

本项目拟采用数值模拟、理论分析和实验测量相结合的方法针对燃气透平动密封动静碰磨过程中的流动传热特性和磨损机理开展详细的研究。建立高温高速旋转动密封在动静界面碰触条件下的磨损变形和耦合传热作用模型，开发基于CFD/FEA的热流固耦合数值求解程序和分析系统，搭建测量动密封流动传热特性和磨损特性的多物理参数综合实验平台，研究碰磨条件下动密封动静界面的磨损变形规律和耦合传热性能，分析磨损过程中流体力、热应力对动密封结构破坏的影响机制。系统研究不同的几何参数、材料属性和运行条件下的磨损破坏机理和性能退化规律，阐明动静碰磨过程中动密封的传热性能和非定常泄漏流动间的相互作用机制，揭示磨损过程中动密封的动态结构变形和局部烧融、磨损传热的非定常变化规律。为研发高性能燃气透平动密封、增强内部冷却效果和提高动密封运行安全提供理论依据。

搭建了适用于燃气透平动密封动静碰磨机理研究的高速旋转磨损实验台、流动传热、流场可视化综合实验平台，并在该实验平台上开展了磨损前后动密封泄漏量、压力分布和流场结构测量实验，研究了磨损型式、磨损程度、磨损结构对动密封性能的影响。建立了燃气透平高速旋转动密封动静碰磨过程的磨损变形有限元分析模型，提出了基于热流固耦合求解的动密封磨损数值求解方法，并利用实验测量获得的动密封流场结构、非定常温度分布、磨损形状对CFD/FEA方法的有效性和精度进行了考核。利用热流固耦合求解方法，研究了动静碰磨过程中磨损界面变形规律和耦合传热特性，分析了关键参数对动密封磨损程度的影响，揭示了热应力、接触压力、传热系数对动密封磨损变形影响规律。结合热流固耦合数值求解方法和磨损变形模型，系统研究了磨损型式、磨损程度对不同结构的动密封泄漏流动的影响机制，阐明了磨损条件下动密封封严性能退化机理。将动密封磨损研究应用于透平级中，研究了动密封磨损对上下游叶栅内的流场结构和气动性能影响规律，阐明了叶顶密封磨损对泄漏流和透平级总体性能的影响机制。提出了减轻动密封动静磨损的措施和方法，并研究了新型弹性密封在透平级应用中的可行性。研究表明：接触压力和碰磨过程中的传热特性是影响动密封磨损变形程度的主要原因，热流固耦合数值求解方法在预测动密封磨损变形特性方面具有较高精度，动密封磨损不仅显著影响到密封内的泄漏量和流场结构，还会对上下游流场以及主流与泄漏的掺混发展产生影响，采用具有较大径向刚度的前弯弹性密封可以有效减轻动密封磨损、提高透平级气动性能。