Numerical and experimental investigation of influencing factors on blow-down effect in brush seal

Brush seal experiences blow-down effect during operation, which accelerates bristle wear and directly shortens their operational lifespan. A theoretical model for blow-down effect in brush seal was established, along with a three dimensional transient numerical model based on Arbitrary Lagrange-Euler (ALE) method for fluid-structure interaction. A visible experimental device for bristle deformation was designed, and radial deformation was experimentally recorded. After verifying the numerical model's accuracy, axial, radial, and cross-sectional deformation characteristics of bristles were investigated, respectively. Radial blow-down displacement was quantitatively analyzed, and effects of different factors on this displacement were compared. Mechanisms inducing blow-down effect were specifically examined. Results showed that inherent circumferential inclination angle of bristles and radial pressure gradient within bristle pack region formed inducing conditions for blow-down effect. Moreover, normal compressive force and tangential friction between bristles caused deformation, which subsequently influenced blow-down effect. While blow-down effect reduced leakage, it increased frictional wear between bristle tips and rotor surface. Increasing circumferential tilt angle of bristles was found to mitigate blow-down effect. Additionally, blow-down effect manifested as non-steady deformation accompanied by bristle disturbance. Radial blow-down displacement increased with rising pressure ratio (up to 18.5%) but decreased with larger circumferential tilt angles (reduction up to 27%).