Experimental Investigation and Mathematical Modeling of Clearance Brush Seals

Abstract

In this paper, an experimental program and a CFD based mathematical model using a brush seal at two bristle to rotor clearances (0.27 mm and 0.75 mm) are presented. The experimental program examined the radial pressure distributions along the backing ring, the axial pressure distribution along the rotor, and the mass flow through the seal through a range of pressure ratios while exhausting to atmosphere. The results from this experimental program have been used to further calibrate a CFD-based model. This model treats the bristle pack as an axisymmetric, anisotropic porous region, and is calibrated by the definition of nonlinear resistance coefficients in three orthogonal directions. The CFD analysis calculates the aerodynamic forces on the bristles, which are subsequently used in a separate program to estimate the bristle movements, stresses, and bristle and rotor loads. The analysis shows that a brush seal with a build clearance produces a very different flow field within the bristle pack to one with an interference, and the need to understand the bulk movements of the bristles. These are shown to be affected by the level of friction between the bristles and the backing ring, which has an important effect on the bristles wear and seal leakage characteristics.

The effects of clearance sizes on labyrinth brush seal leakage performance using a Reynolds-averaged Navier—Stokes solver and non-Darcian porous medium model

“…As shown in Fig. 4, the numerical leakage flowrate is in agreement with the experimental data [9] for three densities of computational grid with 16 000, 22 000, and 32 000 points. The grid numbers independent for this case were illustrated through comparison of the experimental data and numerical results.…”

“…Recently, Dogu et al [21] applied this approach to study the leakage flow characteristics in the clearance brush seal with 0.27 and 0.75 mm under blow-down and no blow-down conditions. Comparison of the numerical results and experimental data [9] confirmed the reliability of this approach.…”

“…The accuracy and stability of the utilized approach are validated by experiments of clearance brush seals [9] at different pressure ratios. The numerical results of the leakage flow analyses for a shaft labyrinth brush seal with four clearance sizes and the comparison of the referenced shaft labyrinth seal are presented.…”

Turbomachinery Clearance Control

“…[97][98][99][100] Though these models are more complex, they permit a more detailed investigation of the subtleties of flow and stresses within the brush pack. figure 45 (and aspirating seal of section V.E).…”

Advanced seal design for rotating machinery

“…The model predictions confirmed the trend of linear pressure drop across the seal thickness. Turner et al [18] presented experimental investigation and a CFD mathematical modeling of clearance brush seals with the rotor to measure the distribution of axial and radial pressure and their leakage characteristics. They used 0.27mm and 0.75 mm clearances, with pressure ratios up to 4, with the seal flow exhausting to atmospheric conditions.…”