Paper IX (i) Brush Seals in Vehicle Tribology

Hendricks, R. C.; Braun, M. J.; Canacci, Victor A.; Mullen, Robert L.

doi:10.1016/s0167-8922(08)70138-x

Cited by 9 publications

(14 citation statements)

References 9 publications

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“…17 Cloth seals are composite structures that make use of tightly woven typically metallic mesh. Most of the issues cited herein are applicable to the design of both metallic and nonmetallic cloth seals-providing proper attention is given to weaves and patterns, such as the multiple strands used in textile fabrics that require modifications for wear volume and contact area calculations.…”

Section: B Metallic Cloth Sealsmentioning

confidence: 99%

“…Design similitude, analysis and modeling of brush and woven seals were established earlier in the works of Flower 76 and Hendricks et al 17 Within in the confines of this section we are only able to address a few sealing types, their locations, and their material constraints. For further details, see Hendricks and coworkers 27,77,78 and NASA Conference Publications.…”

Section: Brush Sealsmentioning

confidence: 99%

“…Comprehensive brush seal design algorithms have been proposed by Chupp et al, 41 Dinc et al, 83 Hendricks et al, 17 and Holle and Krishan. 84 An iterative process must be followed to satisfy seal basic geometry, stress, thermal (especially during transient rub conditions), leakage, and life constraints to arrive at an acceptable design.…”

Section: Brush Seal Design Considerationsmentioning

confidence: 99%

“…Flow models proposed by Hendricks et al 17,90,96 are based on a bulk average flow through the porous media. These models account for brush porosity, bristle loading and deformation, brush geometry parameters and multiple flow paths.…”

Section: Brush Seal Flow Modelingmentioning

confidence: 99%

“…In other related developments, Hendricks et al 17 discussed the modeling and application of several types of brush seals including hairpin woven or wrapped (see hybrid seal), taconite, selfpurging and buffer.…”

mentioning

confidence: 99%

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Turbomachinery Clearance Control

Chupp

Hendricks

Lattime

et al. 2014

Turbine Aerodynamics, Heat Transfer, Materials, and Mechanics

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Section: B Metallic Cloth Sealsmentioning

confidence: 99%

Section: Brush Sealsmentioning

confidence: 99%

Section: Brush Seal Design Considerationsmentioning

confidence: 99%

Section: Brush Seal Flow Modelingmentioning

confidence: 99%

mentioning

confidence: 99%

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Turbomachinery Clearance Control

Chupp

Hendricks

Lattime

et al. 2014

Turbine Aerodynamics, Heat Transfer, Materials, and Mechanics

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Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach

Doğu

2005

Journal of Engineering for Gas Turbines and Power

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The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis, and bristle flutter. In this study, an axisymmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data: leakage, axial pressure on the rotor surface, and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for the fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while the fence height region is free to spread and bend in the axial direction. It is found that flow resistance for the upper region should be 20% higher than the fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.

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Thermal and Flow Phenomena Associated With the Behavior of Brush Seals in Aero Engine Bearing Chambers

Flouros

Hendrick

Outirba

et al. 2015

Journal of Engineering for Gas Turbines and Power

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Due to the increasing fuel cost and environmental targets, the demand for more efficient gas turbines has risen considerably in the last decade. One of the most important systems in a gas turbine is the secondary air system, which provides cooling air to the disks and to the blades. It also provides air for sealing of the bearing chambers. The amount of secondary air that is extracted from the compressor is a performance penalty for the engine. In aero engines, bearing chambers are in most cases sealed by the most traditional type of seal, the labyrinth seal. Bearing chambers contain the oil lubricated components like bearings and gears. In order to avoid oil migration from the bearing chamber into the turbomachinery, the seals are pressurized by secondary air; thus, a pressure difference is setup across the seal, which retains the lubricant into the bearing chamber. Oil loss can lead to a number of problems like oil fire or coking with the probability of an uncontained destruction of the aero engine. Oil fumes can also cause contamination of the air conditioning system of the aircraft thus cause discomfort to the passengers. Beside labyrinth seals, other types of seals such as brush seals and carbon seals are used. Both the latter are contact type seals, that is, they may be installed with zero gap and lift during operation when they get pressurized. Brush seals particularly may be installed having an overlap with the rotating part. An original aero engine bearing chamber was modified by MTU Aero Engines to run with brush seals in a simulating rig in Munich. Two types of brush seals were used for testing: (a) a brush seal with bristles made of Kevlar fibers and (b) a brush seal with bristles made of steel. Both types were installed with an overlap to the rotor. The targets set were twofold: (a) to measure the transient temperatures in the rotor and particularly in the contact zone between the bristles and the rotor and (b) to calculate the heat generation by the seals which could enable predictions of the heat generation in future applications (i.e., scaling to bigger rotor diameters). For the heat transfer calculations, numerical models using ansys cfx were created. Additionally, a coupled computational fluid dynamics (CFD) and finite element analysis (FEA) approach was applied to simulate flow and bristle's behavior. In order to obtain the transient temperature measurements with high fidelity, a new pyrometric technique was developed and was applied for the first time in brush seals as reported by Flouros et al. (2013, “Transient Temperature Measurements in the Contact Zone Between Brush Seals of Kevlar and Metallic Type for Bearing Chamber Sealing Using a Pyrometric Technique,” ASME J. Gas Turbines Power, 135(8), p. 081603) and Flouros et al. (2012, “Transient Temperature Measurements in the Contact Zone Between Brush Seals of Kevlar and Metallic Type for Bearing Chamber Sealing Using a Pyrometric Technique,” ASME Turbo Expo 2012, Copenhagen, Paper No. GT2012-68354). This technique has enabled positioning of the pyrometer (SensorthermGmbH, www.sensortherm.com) into the bristles pack of the seal adjacent to the rotating surface. The pyrometer could record the frictional temperature evolution in the bristles/rotor contact zone during accelerations or decelerations of the rotor. The sealing air demand can be reduced up to 97% with brush seals compared to traditional three fin labyrinth. It has been estimated that this can result in a reduction in fuel burned up to 1%. Further, the reduction in air flow has additional potential benefits such as a possible simplification of the bearing chamber architecture (vent less chamber). Even though the rotor was accelerated up to 19,500 rpm, the temperature induced overshoots in the seal/rotor contact zone have caused no deterioration in either the materials or the oil.

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Paper IX (i) Brush Seals in Vehicle Tribology

Cited by 9 publications

References 9 publications

Turbomachinery Clearance Control

Turbomachinery Clearance Control

Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach

Thermal and Flow Phenomena Associated With the Behavior of Brush Seals in Aero Engine Bearing Chambers

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