Effects of Geometry on Leakage Flow Characteristics of Brush Seal
摘要
In order to better application of brush seal in rotating machinery,the leakage flow characteristics of the brush seal considering geometry effects are numerically analyzed using Reynolds-Averaged Navier-Stokes( RANS) model coupling with a non-Darcian porous medium model. The reliability of the present numerical method is proved,which is in agreement with the experimental and numerical results from literatures. Three different bristle pack thicknesses,fence heights and initial clearances under different pressure ratios,rotational velocities and other operating conditions are utilized to investigate the effects of geometry modification on the brush seal leakage flow behaviors. It discusses the effectiveness of various geometry configurations outlining important flow features. The results indicate that the increase of fence height and clearance would lead to the increase of leakage rate. But the leakage is not linearly with respect to the bristle pack thickness,and the effect of rotational velocity is not obvious. Moreover,the detailed leakage flow fields and pressure distributions along the rotor surface,free bristle height,and fence height of the brush seals are also presented. The static pressure drop amplitude through the bristle pack and the pressure rise amplitude through the cavity would increase while the pressure differential increases. And the axial pressure is the main reason of bristle blow down. The results provide theoretical support for the brush seal structure optimal design.