To accurately predict the leakage flow and resistance characteristics of brush seals, the multi-block structured mesh and the mesh motion technique are applied to the three-dimensional (3D) staggered tube bundle model of brush seals. The multi-block structured mesh can easily add nodes and set boundary layers in the inter-bristle gap between adjacent bristles, which can ensure good mesh quality . The mesh motion technique realizes the overall axial compactness of the bristle pack. The effects of pressure ratio , sealing clearance c and bristle pack compactness on the leakage flow and resistance characteristics are investigated. To analyze the aerodynamic resistance of the brush seals, Euler number (Eu) is applied in the present study. The numerical results are in good agreement with the experimental data. Thus the accuracy of the presented numerical method is validated. For the contacting brush seal, ?"?S" ?_"x,i" has a significant effect on the leakage flow rate reduction. For the clearance brush seal, ?"?S" ?_"x,i" has little effect on the leakage flow rate reduction. The leakage flow passing through the sealing clearance keeps almost constant. As for aerodynamic resistance, the presence of the sealing clearance can effectively convert the pressure energy of the leakage flow into the kinetic energy. As a result, the leakage flow velocity exiting the bristle pack of the clearance brush seal is 1.5 to 2.0 times larger than that of the contacting brush seal.

This paper numerically investigates the leakage flow characteristics of two types of HLBSs (bristle pack installed upstream or downstream of helical-labyrinth tooth named as HLBS-U and HLBS-D, respectively) at various pressure ratios (1-1.3) and rotational speeds (0-10000r/min). In parallel, the leakage flow characteristics of the HLBS-D with the constant cb of 1.0 mm are experimentally measured at the pressure ratio up to 1.3 and rotational speed up to 2000 r/min. The effective clearance of the HLBS-U is smaller than that of the HLBS-D in the case of cb=0.5mm and rotational speed n<10000r/min, and the case of cb=1.0mm. However, for the case of cb=0.5mm and n=10000r/min, and the case of cb=0.1mm, the situation is opposite. The brush seal sections of the HLBS-U and the HLBS-D offer over 55% and 65% total static pressure drop in the case of cb=1.0 mm, respectively; The brush seal sections of two HLBSs bear almost the same static pressure drop of the over 97% total static pressure drop as cb equals to 0.1 mm. The HLBS-U has lower turbulent kinetic energy upstream of the bristle pack than the HLBS-D does, which means that intensity of bristles flutter of the HLBS-U is lower. The HLBS-U possesses significantly lower absolute value of aerodynamic forces than the HLBS-D does as cb=1.0 mm.

The blade tip shroud brush seal is applied to replace the labyrinth seal for the aerodynamic performance improvement of turbine stage. The leakage flow characteristics of the brush seal are numerically predicted by using the Reynolds-Averaged Navier–Stokes equations and non-linear Darcian porous medium model. The numerical leakage flow rate of the brush seal is in well agreement with the experimental data. The last and first long teeth of the labyrinth seal were designed to bristle pack named as the postposed and preposed brush seals based on the 1.5 turbine stage. The leakage flow rate and aerodynamic performance of the turbine stage with blade tip shroud labyrinth seal and brush seal are numerically investigated. The effect of the sealing clearance between bristle pack and tip shroud on the aerodynamic performance of turbine stage is conducted which ranged from 0 mm to 0.4 mm. The axial deflection of the bristle pack is analyzed with consideration of the aerodynamic forces and contact frictional force. The obtained results show that the leakage flow rate of the tip shroud brush seals with bristle tip 0.4 mm clearance which decreases by up to 18% in comparison with the labyrinth seal, and the aerodynamic efficiency increases by 0.6%. Compared to the tip labyrinth seal, tip shroud brush seals can decrease the relative deflection angle of exit flow. This flow behavior results in reducing the mixing loss between the tip leakage flow and mainstream. The similar axial deflection of the bristle pack for two kinds of brush seals is observed at the same sealing clearance. The deflection of the bristle pack under the function of the aerodynamic forces is protected by the backing plate. This work provides the theoretical basis and technical support for the brush seal application in the turbine industries.

In comparison to the traditional brush seal, the rotating brush seal installed on a rotating shaft eliminates the influence of friction heat effects and improves the operational stability of the rotating shaft system. Relevant investigations give sparse detailed parameters and experimental data for the rotating brush seal providing insufficient data support and prompting further investigation for the sealing characteristics of the rotating brush seal. In this article, the three-dimensional tube bundle model was regarded as the computational fluid domain of the rotating brush seal. The multi-block structured mesh was applied to discrete the computational domain. The effect of the pressure ratio and rotational speed on the leakage flow and aerodynamic characteristics of the brush seal were numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes solutions and [Formula: see text] turbulence model. Similar to the traditional brush seal, the leakage flow rate of the rotating brush seal increases linearly with the pressure ratio. The effect of the pressure ratio on the flow coefficient is more significant at low pressure ratio. When the pressure ratio increases from 1.5 to 2.5, the flow coefficient increases by 44.40%. However, when the pressure ratio increases from 3.5 to 4.5, the flow coefficient just increases by 4.12%. It means that the flow coefficient shows a trend independent of the pressure ratio at higher pressure ratio. The flow coefficient obtained by computational fluid dynamics model is found to increase lightly as the rotational speed increases. The rear bristles are subjected to large axial aerodynamic force and are prone to axial deformation. The investigation provides the reference for the performance analysis and design of rotating brush seal.

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