A Multi-Physics Behavior Assessment Framework for Brush Seals: Effects of Geometry Parameters

Abstract Owing to their superior sealing characteristics compared to labyrinth seals, brush seals have seen increasingly widespread adoption in turbomachinery. Their excellent performance is primarily attributed to the flexible bristles, with geometric parameters also playing a critical role. During operation, the bristles experience complex phenomena including slip, friction, and heat generation, which collectively impact the leakage behavior and service life. This article presents a comprehensive coupled model to investigate the multiphysics behavior of brush seals. The integrated framework incorporates two components: a three-dimensional dynamic bristle model and a two-dimensional leakage flow model. The three-dimensional bristle dynamic model captures the slip friction and large deformation of the bristle pack under mechanical and aerodynamic loads. Additionally, this model can capture contact forces exerted by the rotor and backing plate and inter-bristle collision and squeeze forces, enabling accurate prediction of bristle deformation and the hysteresis effect in the rear part of the bristle pack. The two-dimensional leakage flow model calculates the compressible flow field and the pressure distribution within the bristle pack to obtain a more accurate aerodynamic force around each bristle. Based on these two models, a fully bidirectional coupling can be established in the future: aerodynamic forces from the leakage models are incorporated into the dynamic bristle model, while the permeability changes due to bristle deformation and friction are fed back into the leakage flow models. An extensive parametric investigation is conducted to evaluate the influence of key geometric parameters. Specifically, the study examines the effects of fence heights, rotor incursion into the bristle pack, and bristle lay angle. The results indicate that hysteresis is enhanced with increasing pressure differential, accompanied by a larger bristle tip force. Hysteresis continuously weakens with increasing bristle diameter, yet the bristle tip force increases. As the lay angle increases, hysteresis is progressively intensified, bristles become less deformable, and bristle tip force decreases. The hang-up height decreases with larger bristle diameters and increases with larger lay angles. Leakage increases with higher pressure ratios and decreases with larger bristle diameters. With larger bristle diameters, the aerodynamic forces on the upstream and downstream bristles become more nonuniform, and the downstream pressure variation becomes more pronounced. Leakage increases with greater fence height. Higher fence heights lead to smoother pressure variation and more uniform bristle loading.