Numerical Investigations on the Heat Transfer Behavior of Brush Seals Using Combined Computational Fluid Dynamics and Finite Element Method

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Abstract
Brush seals have been applied in more and more challenging high-temperature locations. The high speed bristle-rotor friction causes a considerable heat generation which accelerates the bristles wear. The frictional heat generation at bristle-rotor interface becomes another major concern in brush seal applications. This study presented detailed investigations on the heat transfer characteristics and contact mechanics of brush seals using a combined computational fluid dynamics (CFD) and finite element method (FEM) brush seal model. The CFD model of brush seal for mass and heat transfer employed Reynolds-averaged Navier–Stokes (RANS) solutions coupled with non-Darcian porous medium approach. The nonlinear contact model of brush seal was established using FEM with considerations of internal frictions (bristle to rotor, bristle to backing plate, and bristle to bristle) and aerodynamic loads on bristles. The numerical method involved iterations between CFD and FEM models to better evaluate the heat transfer behaviors of the brush seal with consideration of bristle deflections. The frictional heat generation was calculated from the product of bristle-rotor frictional force and sliding velocity. The bristle deflections and temperature distributions of the brush seal were predicted at various operational conditions using the iterative CFD and FEM brush seal model. The effects of pressure differential and rotational speed on the contact behavior, temperature distribution and bristle maximum temperature of brush seals were numerically investigated using the developed approach. The detailed pressure contours and streamline distributions of the brush seal were also illustrated.

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