Numerical Simulation Of Leakage Flow And Contact Heat Transfer Through Brush Seal

The appearance of brush seal has greatly reduced the leakage of turbo machine .Because of its special structure , the flow phenomenon is complex. The leakage and tip friction heat transfer has become hot research point nowadays. In the present research, the two-dimensional staggered tube array model was set up; computational fluid dynamics (CFD) was employed to simulate the block effects of staggered tube bundle. In combined with the porous media model, we can acquire the leakage of brush seal in different geometry. Finite element model (FEM) was employed to study the contact force of brush tip. In combined with the porous media model ,we acquired the heat transfer phenomenon in the brush tip.The fluid flow across the compact staggered tube array were analyzed and we acquired the exponential dependency of the pressure loss on the Reynolds number (power=1.6～1.77). The numerical results demonstrated that the velocity distribution tends to be stabilized after the first row of the compact tube array (s/d<1.12). Computational fluid dynamics and porous media model was employed to simulate the leakage flow of brush seal at five difference radial clearances, e.g., 0, 0.1, 0.2, 0.3 and 0.4mm. In computation, three different pressure ratio conditions were considered, e.g., 1.5, 2.0 and 3.5. We acquired that the one order of increase of the leakage flow through the brush seal with 0.1mm radial clearance in comparison to the contact case. With increasing pressure ratio, the leakage flow is significantly intensified. For the systems of the radial clearance 0.3~0.4mm, 75~85% of the total leakage fluid flows through the clearance channel. In addition, the radial pressure gradient at the free-end of the brush seal near the back plate is peaked, indicating that the leakage fluid inside the brush seal region would be pushed to the clearance channel and intensify the leakage flow. The different location of the brush seal can not affect the leakage . But the leakage can be reduced to 20% of the original level in using three brush seal. The contact force showed hysteresis effect with the interference. We acquired the exponential dependency of the temperature decrease on the radial direction from the brush tip .