发电技术 (Oct 2024)
Investigations on the Leakage Flow Characteristics and Sealing Mechanism of Turbomachinery Brush Seals Using Bristle Pack Staggered Tube Bundle Model
Abstract
ObjectivesIn order to obtain the refined leakage flow of brush seal and reveal its sealing mechanism, the mathematical model of the leakage flow characteristics of brush seals based on the bristle pack staggered tube bundle model was established.MethodsThe leakage flow rate and characteristics inside the bristle pack of brush seal were investigated by numerical solution of Reynolds-averaged Navier-Stokes (RANS) and shear stress transport (SST) k-ω turbulence model. The leakage and pressure distribution obtained by numerical simulation agrees well with the experimental data, which verifies the reliability of the numerical method. The leakage flow rate and characteristics inside the bristle pack of brush seal was analyzed at four kinds of pressure ratios and rotational speeds.ResultsWith the increase of pressure ratio, tiny vortex begins to appear inside the bristle pack and gradually develops. The obstruction effect on the leakage flow becomes larger, which slows down the trend of leakage increment with the pressure ratio. In addition, the pressure drop of the last row of bristle accounting for the overall pressure differential increases from 13.1% to 26.3%.ConclusionsIn the studied range of rotational speed, the influence of rotational speed on the leakage of brush seal can be ignored. When the pressure ratio is different, the difference in the radial flow strength of the leakage flow in the gap between the last row of bristle and the backing plate and the axial flow strength at the fence height will lead to the difference in the vortex system structure under the backing plate. The sealing mechanism of the brush seal was revealed using the refined leakage flow inside the bristle pack. The research results can provide reference for the leakage flow analysis of brush seal using three-dimensional staggered tube bundle model.
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