Mechanical Damping Analysis of a Vibrating Labyrinth Seal Structure With Frictional Contact

Abstract

Gas turbines incorporate throughout the engine many labyrinth air seals, which can suffer vibration excitation from a number of potential sources. This paper presents an analytical study of an example design of seal, for which vibration test data were available. Understanding of the observed vibration displacements was gained from (i) an investigation of the forcing excitation mechanism and (ii) non-linear vibration analysis of the seal structure, including estimates of work extracted by frictional contacts (mechanical damping). This paper presents only the mechanical damping analysis as an example of an industrial application of advanced multi-harmonic balance non-linear vibration techniques. The paper includes an overview of the non-linear model construction, including sensitivity studies in model reduction and contact element parameter choices. Once established, it is shown how the vibration model is used to assess the performance of a ring damper for the labyrinth seal in relation to the background mechanical damping provided by contact with adjacent components. The damping is a function of both friction coefficient and displacement amplitude and it is shown how the robustness of the damper design relates to friction assumptions.