Analytical Approach for Investigating Bristle/Backplate Hysteresis Phenomenon in Brush Seals

Zhao, Haifang; Stango, R. J.

doi:10.2514/1.20682

Cited by 7 publications

(4 citation statements)

References 6 publications

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“…During a rotor excursion, bristles are pushed radially outwards to accommodate an eccentric or thermally expanded rotor, and after such transient conditions, the rotor returns to its original or steady-state position. With the action of a pressure difference, the brush pack is pressed tightly against the back plate, and obstructed by friction, the deformed bristles 'hang up' as they are locked in position against the back plate and cannot recover their original positions, which is called the hysteresis effect (HE) [2]. To weaken the HE of a conventional brush seal, a low-hysteresis structure [3] was proposed that incorporates a pressure relief chamber (PRC) between the brush pack and the back plate, as shown in Figure 1 The HE causes a gap between the brush pack and the rotor, resulting in increased leakage and decreased sealing performance; as can be seen, the hysteretic bristle deformation directly affects the sealing performance.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of deformation hysteresis effect of the bristles of brush seals

Li,

Hu,

2024

J. Phys.: Conf. Ser.

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Because of their good sealing performance, brush seals are used widely in turbomachinery as alternatives to traditional labyrinth seals. However, obstructed by friction, the flexible bristles cannot recover fully after deformation, resulting in a hysteresis effect and decreased sealing performance. In the present study, a three-dimensional multi-row bristle model is established that considers the friction between the neighbouring bristles and back plate. Then the deformation and recovery of the bristles during the radial reciprocating offset of the rotor in the presence of a pressure difference are studied. To evaluate the hysteresis effect, analysis is directed at the unrecovered bristle deformation in the radial direction affected by bristle diameter, bristle lay angle, fence height and width of pressure relief chamber. The results show that the larger the bristle diameter and fence height, the weaker the hysteresis effect and the larger the bristle lay angle, the stronger the hysteresis effect. With increasing width of the pressure relief chamber, the hysteresis effect weakens and then strengthens, meaning that the pressure relief chamber has an optimal axial width that departure from enhances the hysteresis effect. The present results offer a reference for selecting the structural parameters of brush seals in engineering design.

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Section: Introductionmentioning

confidence: 99%

Numerical simulation of deformation hysteresis effect of the bristles of brush seals

Li,

Hu,

2024

J. Phys.: Conf. Ser.

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“…Stango et al [7] further extended their models to include the aerodynamic blowdown effects. Zhao and Stango [8] developed a model to include the bristle-backing ring friction effects, that were able to qualitatively capture the seal hysteresis. However, the shaftbristle friction was not considered simultaneously.…”

Section: Introductionmentioning

confidence: 99%

Insights Into Frictional Brush Seal Hysteresis

Phan,

Pekris,

Chew

2024

Journal of Engineering for Gas Turbines and Power

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Brush seals offer a superior sealing effectiveness compared to labyrinth seals. However, widespread use of brush seals is constrained by deleterious behaviors such as pressure-stiffening and hysteresis. For the latter, the bristles bend during the shaft incursion process and do not fully recover during the shaft retraction process. An opening gap is created, which increases seal leakage unless the pressure load drops to a certain level. In the present work, analytical and numerical models based on a single bristle are proposed to capture the seal's response to shaft displacement with and without pressure loading. The models are validated using static stiffness tests at an unpressurized condition from literature. The main results show that modeling of the backing ring friction is essential to capture the bristle hang-up behavior. Shaft friction dominates at unpressurized conditions, while backing ring friction dominates at high pressure loading. An expression for shaft hang-up displacement has been derived. A sensitivity study shows that seals with shallow lay angle, short bristle length, and large bristle diameter are less prone to hang-up problems. The models developed in the present framework have been shown to qualitatively capture the pressure stiffening, hysteresis, bristle hang-up, and shaft rotation effects.

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Section: Introductionmentioning

confidence: 99%

Insights Into Frictional Brush Seal Hysteresis

Phan,

Pekris,

Chew

2023

Volume 7B: Heat Transfer — General Interest/Additive Manufacturing Impacts on Heat Transfer; Internal Air Systems; Internal Coo

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Brush seals offer a superior sealing effectiveness compared to labyrinth seals. However, widespread use of brush seals is constrained by deleterious behaviors such as pressure-stiffening and hysteresis. For the latter, the bristles bend during the shaft incursion process and do not fully recover during the shaft retraction process. An opening gap is created, which increases seal leakage unless the pressure load drops to a certain level. In the present work, analytical and numerical models based on a single bristle are proposed to capture the seal’s response to shaft displacement with and without pressure loading. The models are validated using static stiffness tests at an unpressurized condition from literature. The main results show that modeling of the backing ring friction is essential to capture the bristle hang-up behavior. Shaft friction dominates at unpressurized conditions, while backing ring friction dominates at high pressure loading. An expression for shaft hang-up displacement has been derived. A sensitivity study shows that seals with shallow lay angle, short bristle length, and large bristle diameter are less prone to hang-up problems. The models developed in the present framework have been shown to qualitatively capture the pressure stiffening, hysteresis, bristle hang-up, and shaft rotation effects.

show abstract

Analytical Approach for Investigating Bristle/Backplate Hysteresis Phenomenon in Brush Seals

Cited by 7 publications

References 6 publications

Numerical simulation of deformation hysteresis effect of the bristles of brush seals

Numerical simulation of deformation hysteresis effect of the bristles of brush seals

Insights Into Frictional Brush Seal Hysteresis

Insights Into Frictional Brush Seal Hysteresis

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