Brush seal dynamic stiffness behavior

Abstract

Brush seals are emerging as alternative to labyrinth applications in turbomachinery. Seal stiffness determines wear rate and long-term leakage performance. Stiffness increases under pressure as bristles get stuck at the backing plate. Complex brush structure does not allow simple modeling of operating conditions. Common static-unpressurized measurements do not represent operating stiffness due to changes in bristle behavior under pressure load. This work presents brush seal stiffness under combined pressure and speed conditions. Contact forces are measured via load cells. Static and combined dynamic stiffness results are presented for various operation conditions. Testing methodology, calibration procedure, and stiffness results are discussed.