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Effect of the fence height on the leakage flow characteristics of brush seals is investigated by means of experimental measurements and numerical simulations. The leakage flow rate of brush seal with three sizes of fence height is measured at six rotor surface velocities ranged from 0m/s to 62.8m/s among pressure differences 9.64kPa to 192.8kPa and the working fluid is air. The detailed leakage flow field of the experimental brush seals is numerically analyzed using threedimensional Reynolds-Averaged Navier-Stokes (RANS) and SST turbulence model based on the Non-Darcian porous medium. The accuracy of the numerical method is validated by comparison of experimental data. The obtained results show that the effective clearance of brush seal decreases with the fence height decreases at the fixed rotor surface velocity and pressure difference. The effective clearance of brush seal with three sizes fence height increases significantly with the increases of pressure differences at the fixed rotor surface velocity. The effective clearance of interference brush seals slightly decrease with the increasing rotor surface velocity due to the friction heat generation. Effect of the rotor surface velocity on the effective clearance of brush seal is limited when the bristles wear and friction heat generation is not considered. The detailed leakage flow field of the brush seal is also illustrated. INTRODUCTION The leakage rate of brush seal is only 10%-20% of that of the traditional labyrinth seal. Flexible bristles have strong adaptability to the eccentric operation of the rotor. Therefore, brush seals are widely used in turbomachinery (Aslan-zada, 2012; Schur, 2018 ). The research on leakage flow characteristics of brush seals mainly focuses on experimental measurement and numerical analysis. Carlile et al. (1993) measured the leakage rate of brush seals for three different working fluids including helium, air and carbon dioxide at low and zero rotor surface velocities. The results show that the leakage flow rate of brush seals decreases slightly at low rotating speeds compared with zero rotor surface velocity. Li et al. (2012) analyzed effect of clearance sizes on the leakage performance of a labyrinthbrush seal and found that the blow-down effect should be considered for clearance brush seals. Hildebrandt et al. (2019) experimentally investigated the effect of bristle pack density, rotor-bristle interference, rotational speed and pressure difference on leakage flow of a kind of clamped brush seal with an axially inclined bristles pack. At present, the numerical study of leakage flow behaviors of brush seals is mainly based on the non-Darcian porous medium model due to the limitations of cross-flow models and bulk flow models (Dogu, 2016). Li et al. (2010) numerically studied the clearance on the leakage flow characteristics of brush seal. Dogu and Aksit (2006) numerically investigated the influences of the front plate and backing plate geometries on leakage flow behaviors of the brush seals. Dogu et al. (2016) numerically analyzed the leakage rates of brush seals under different working conditions and different geometric conditions and found that the geometric parameters and working conditions that play decisive roles in leakage flow are bristle pack thickness, clearance between bristle pack and rotor, fence height, and pressure difference. Considering the thermal deformation of the rotor and transient operating conditions, there should be an appropriate radial distance between the rotor and the front/backing plate of brush seals. The radial distance between the backing plate

Effect of the Fence Height on the Leakage Flow Characteristics of Brush Seals