Pressure Distributions Below Brush Seals at Varying Operating Conditions

Abstract

The influences of different manufacturing methods and design parameters of brush seals and their complex interactions with the flow through the bristle pack complicate the modeling of the flow through brush seals. While radial pressure distributions along the backing plate and the leakage behaviour of various brush seal designs are published, experimental data on axial pressure distributions on the surface of the shaft is insufficient. In order to gain a better understanding of the phenomena associated with the flow through brush seals, the axial pressure distributions in the sealing gap below six different brush seals are measured on a cold air test rig at rotational speeds up to 3000rpm and pressure differences across the seals up to 500kPa with an axial resolution of 0.2mm. By investigating a welded and five different clamped brush seals, the influence of two different designs on the flow through the bristles is shown. For the clamped brush seals the design of the front and backing plate is varied. Moreover, the effects of bristle diameter and three different axial inclinations of the bristle pack on the axial pressure distribution are presented. Therefore, the effects of the major design aspects on axial pressure distributions at the interface between brush seals and rotor are examined and the results are supported by optical measurements taken on the rotating and a stationary test rig.