COMPUTED EFFECTS OF ROTOR-INDUCED SWIRL ON BRUSH SEAL PERFORMANCE .2.BRISTLE FORCE ANALYSIS

This paper analytically investigates the aerodynamic bristle force dis tributions in brush seals used in aircraft gas turbine engines. These forces are responsible for the onset of bristle tip lift-off from the rotor surface which significantly affects brush seal performance. In o rder to provide an enhanced understanding of the mechanisms governing the bristle force distributions, a full Navier-Stokes, flow simulation is performed in a streamwise periodic module of bristles correspondin g to the staggered square configuration. As is the case with a compani on paper (Sharatchandra and Rhode, 1996), this study has the novel fea ture of considering the combined effects of axial (leakage) and tangen tial (swirl) flows. Specifically, the effects of intra-bristle spacing and bristle inclination angle are explored. The results indicate that the lifting bristle force increases with reduced intra-bristle spacin g and increased inclination angle. It was also observed that increases in the axial or tangential flow rates increased the force component i n the normal as well as the flow direction.