Experimental Analysis of Small Diameter Brush Seals and Comparisons With Theoretical Predictions

Abstract

The paper presents the experimental results obtained for brush seals of 38 mm diameter operating with air at pressure differences up to 7 bars and rotation frequencies up to 500 Hz. The seals had bristles of 70 μm diameter, made of Haynes 25. Seals with two radial interferences (0 and 100 μm) between the brush and the rotor were tested. The presented running in procedure underlines the influence of the initial wear on the brush temperatures. The test results consisted of leakage mass flow rates. The temperatures of a limited number of points on the brush and on the rotor were also recorded. The results confirmed the important impact of the radial interference on the leakage. The test data were further confronted with theoretical predictions obtained with an original model. The model considers the brush as a deformable porous medium. Its local porosity and permeability are obtained from a fluid–structure interaction between the bristle pack and the leakage flow. The comparisons showed nearly close values of the mass flow rates. The differences between experimental and theoretical predictions are considered to be due to an underestimation of the porosity because the model neglects the friction forces between bristles and between the bristles and the rotor.

Using a three-dimensional tube bundle model to investigate the leakage flow characteristics of the rotating brush seal

“…When the pressure ratio is in the range of 2.5-4.0, the leakage flow rate of the threedimensional tube bundle model is in good agreement with the experimental data. In Ma's investigation, 32 the experimental data in literature 35 and 22 were also used to validate the three-dimensional tube bundle model.…”

“…When the pressure ratio is in the range of 2.5– 4.0, the leakage flow rate of the three-dimensional tube bundle model is in good agreement with the experimental data. In Ma’s investigation, 32 the experimental data in literature 35 and 22 were also used to validate the three-dimensional tube bundle model.

Figure 6.Comparison of the leakage flow rate between the numerical results and the experimental data of the traditional brush seal obtained by Bayley and Long. 35

…”

“…The maximum axial deformation of the bristle tip is about 0.1 mm. 21 Deville 22 presented the experimental data obtained for the clamped brush seal operating with air at pressure differential up to 7 bars. A model considering the bristle pack as deformable porous medium was used to predict the sealing performance of the clamped brush seal.…”

Brush seal design and secondary air system modification of a heavy-duty gas turbine to improve the output power

“…It should be noted that the implementation of pressure-balanced brush seal is preferred at turbine inter-stage packings. 15 The design contact between bristle and rotor (with clearance, with interference, or line-to-line) affects the hysteresis loop as presented in Deville and Arghir 11 and Zhang et al 12 Deville and Arghir 11 indicated that brush seals with the line-to-line configuration show a higher levels of hysteresis compared to the interference configuration. Furthermore, interference results in hysteresis reduction according to Zhang et al 12 In addition, they noticed that increasing the rotational speed of the rotor results in less hysteresis effect.…”

“…8 The hysteresis loops are illustrated in most research in the literature. 2,[9][10][11][12][13] Berard and Short 14 and Dinc et al 15 investigated the pressure-balanced brush seals and reported that 1 School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran hysteresis could be reduced using relief back-plate design. It should be noted that the implementation of pressurebalanced brush seal is preferred at turbine inter-stage packings.…”