Session: 14-06 Compliant Seals

Paper Number: 128820

128820 - Tracking of Bristle Tip Deflections to Demonstrate Blow-Down in Brush Seals 

Brush seals are used for sealing in gas turbines as an alternative to the more common labyrinth seal. They consist of a ring of densely packed, flexible fine bristles. When subjected to a pressure load, these bristles deflect axially, compacting together to provide enhanced resistance to the flow. The bristles are typically fitted at a lay angle to the radius, such that the flow imparts a bending moment in the orthogonal and tangential planes; therefore, the bristle deflections occur in three-dimensions. Deflections in the orthogonal plane, known as bristle blow-down, close clearances during off-design conditions and maintain seal performance as the bristles wear. However, excess blow-down can lead to excessive contact forces and seal wear.

This study employs Digital Image Correlation (DIC) to track individual bristles in three spatial axes in a representative large-scale brush seal test facility. To the authors’ knowledge, it is the first experimental study to directly measure bristle blow-down displacement. Measurements of bristle blow-down and axial deflection were taken for a pressure relieving brush seal at two clearance conditions and studied in conjunction with the inter-bristle pressure fields. These findings were used to demonstrate the benefits of pressure relieving brush seals compared to conventional back plate configurations.

Presenting Author: Joshua Bowen University of Bath

Presenting Author Biography: Josh is a PhD student at the University of Bath.

Authors:

Joshua Bowen University of Bath
Aaron Bowsher Cross Manufacturing Company (1938) Ltd
Peter Crudgington Cross Manufacturing Company (1938) Ltd
Sam Bull University of Bath
Carl Sangan University of Bath
James Scobie University of Bath