Porosity Modeling of Brush Seals

Abstract

A new model for predicting leakage flows through the bristle pack of brush seals is developed. In the model, the bristle pack is treated as a porous medium. Good agreement is demonstrated between predictions from a one-dimensional form of the model and a wide range of experimental data available from the literature, for seals with a bristle pack to rotor interference fit. The results demonstrate that both viscous and inviscid effects contribute significantly to the drag on the bristles within the pack. The model uses a linear superposition of viscous and inertial losses, with a resistance coefficient assigned to each contribution. Formulas that have been deduced for flow in packed beds, are adapted for use in assigning values to the resistance coefficients in the one-dimensional model. Finally, extension of the method to multiple dimensions is discussed, with a view to incorporating the model into a CFD code to form a general predictive capability for brush seal flows.