Investigations on the Leakage Flow Characteristics and Sealing Mechanism of Turbomachinery Brush Seals Using Bristle Pack Staggered Tube Bundle Model

doi:10.12096/j.2096-4528.pgt.24098

Abstract

Abstract:

Objectives In 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. Methods The 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. Results With 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%. Conclusions In 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.

Key words: turbomachinery, brush seal, bristle pack, staggered tube bundle model, leakage flow, sealing mechanism

CLC Number:

TK 14

Pengfei SONG, Jie QU, Qing GAO, Zhigang LI, Jun LI. Investigations on the Leakage Flow Characteristics and Sealing Mechanism of Turbomachinery Brush Seals Using Bristle Pack Staggered Tube Bundle Model[J]. Power Generation Technology, 2024, 45(5): 826-837.

Figures/Tables 18

Fig. 1 Screenshot of the unloaded bristle pack

Fig. 2 Bristle arrangement under different sections

Fig. 3 Computational domain of the brush seal

Tab. 1 Main geometric parameters of the brush seal

结构参数	数值
转子直径D/mm	121.76
前夹板内径D_fp，in/mm	142.40
总外径D_out/mm	151.71
刷丝束厚度w/mm	0.672
前夹板厚度w_fp/mm	1.625
后夹板厚度w_bp/mm	1.625
刷丝直径d/mm	0.076 2
围栏高度H_F/mm	1.4
刷丝间隙δ/mm	0.007
刷丝倾斜角 $ϕ$ /(°)	45

Tab. 1 Main geometric parameters of the brush seal

结构参数	数值
转子直径D/mm	121.76
前夹板内径D_fp，in/mm	142.40
总外径D_out/mm	151.71
刷丝束厚度w/mm	0.672
前夹板厚度w_fp/mm	1.625
后夹板厚度w_bp/mm	1.625
刷丝直径d/mm	0.076 2
围栏高度H_F/mm	1.4
刷丝间隙δ/mm	0.007
刷丝倾斜角 $ϕ$ /(°)	45

Fig. 4 Schematic of the mesh for the brush seal

Fig. 5 Leakage flow rate for different grid numbers

Fig. 6 Topology and node distribution of multiblock structured grid for brush seal

Tab. 2 Boundary conditions of numerical simulation

参数	数值
进口压力/kPa	150，200，250，300
出口压力/kPa	100
进口温度/K	293.15
转速/(r∙min^-1)	0，3 000，6 000，9 000

Fig. 7 Axial pressure distribution under the bristle tips

Fig. 8 Radial pressure distribution along the backing plate

Fig. 9 Leakage flow rate of brush seal versus pressure ratios and rotational speeds

Fig. 10 Flow property distribution along the axial direction

Fig. 11 Static pressure contours in axial-circumferential plane (1/2HF)

Fig. 12 Axial velocity contours and streamline distribution in axial-circumferential plane (1/2HF)

Fig. 13 Static pressure contours in axial-radial plane

Fig. 14 Axial velocity contours and streamline distribution in axial-radial plane

Fig. 15 3D streamline distribution at fence height region

Fig. 16 3D streamline distribution on rotor surface (Rp=3.0)

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