Aerodynamic instability of brush seals in gas turbine engines based on a fluid-structure interaction method.

This article investigates the circumferential slip instability of brush seal bristles—mechanical seals composed of flexible bristles used in gas turbine engines—under high swirling flow and pressure conditions. Using a two-way fluid-structure coupling method combining three-dimensional computational fluid dynamics and mechanical analysis, the study identifies the ratio of normal to axial aerodynamic forces (Fn/Fax) on the first row of bristles as the key parameter governing slip instability, with slip occurring when this ratio exceeds approximately 0.91. The research shows that higher pressure differentials and downstream pressures influence this force ratio and the critical swirl velocity for slip, with increased downstream pressure reducing axial force but increasing normal force, thereby lowering the swirl velocity threshold for instability. Additionally, the presence and length of a front plate covering the bristles alter upstream flow patterns, increasing Fn/Fax and promoting earlier slip rather than preventing it. These findings provide quantitative criteria for predicting bristle slip and offer insights for the design and stability improvement of brush seals in aeroengine applications.