Abstract
Brush seals are plausible replacements for conventional labyrinth seals in gas turbines for managing internal air system flows and leakages. They can offer superior leakage performance compared to labyrinth seals due to their compliant nature, and a reduced effective clearance during operation. Despite their improved sealing performance, highly swirling flow and aerodynamic forces on the upstream bristles could lead to aero-elastic instability within the bristle pack. This study investigates grooves as a means of improving brush seal robustness in high-shaft speed locations by reducing the inlet swirl that is incident on the bristle pack. The material removed and implied manufacturing effort and cost are considered. A parametric study of a simple groove geometry was conducted using CFD and a porous medium representation of the bristle pack whose resistance coefficients were calibrated to Bayley and Long’s data to achieve representative seal leakages. This identified groove length, width, angle and pitch as the important groove parameters for swirl reduction and demonstrated that the performance of ribs from previous research can be replicated and improved upon. A Design of Experiments (DOE) approach was adopted to investigate a novel groove design geometry. Combining a horizontal channel with an inclined groove enables a higher pitch to achieve the same swirl reduction by increasing drag and exploiting fluidic effects. The results indicate that the novel groove design performs as intended in substantially reducing the swirl incident on the bristle pack. Adding these features to the traditional front plate may improve brush seal robustness by reducing the effect of aerodynamic forces which could drive bristle pack instabilities, thus having the potential to aid their deployment in high-radius or high-shaft speed engine locations.
