Brush Seal Bristle Segmentation for Hydrodynamic Lift

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Solution Overview

Problem

Conventional brush seals in gas turbine engines experience excessive wear and reduced efficiency due to high blow-down effects from differential fluid pressures, leading to undesirable bristle and shaft deterioration.

Innovation Solution

The introduction of a brush seal design featuring a plurality of bristles with discontinuities in the sealing surface, creating a hydrodynamic lifting force that reduces contact pressure and wear by varying bristle lengths and angles, allowing some bristles to lift off or reduce contact with the shaft, thereby mitigating the blow-down effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional brush seals use uniform bristle contact with the rotating shaft, then sealing effectiveness is maintained, but excessive wear occurs on both the bristles and shaft due to high contact pressure from differential fluid pressures

Engineering Contradiction:

Improvesealing effectivenessVSAvoidservice life

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The brush seal is segmented into multiple zones with different bristle lengths. The bristles are divided into a first group with longer lengths that contact the shaft, and a second group with shorter lengths that do not contact the shaft, creating discontinuities in the sealing surface. This segmentation allows different regions to perform different functions: sealing and hydrodynamic lift generation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the brush seal are given different local properties through varying bristle lengths. The upstream region has longer bristles for sealing contact, while the downstream region has shorter bristles that create gaps for hydrodynamic lift. This local differentiation optimizes both sealing effectiveness and wear reduction in specific zones.

Inventive Principle:

Principle #3Local quality

2Reliability

If brush seal bristles are made longer to improve sealing, then sealing effectiveness increases, but wear and deterioration of bristles and shaft increase due to higher contact pressure

Engineering Contradiction:

Improvesealing effectivenessVSAvoidwear and deterioration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The bristle population is segmented into two distinct length groups. Longer bristles in the first group provide the necessary sealing contact, while shorter bristles in the second group create discontinuities that generate hydrodynamic lift forces, reducing the overall contact pressure and wear on both bristles and shaft.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The differential fluid pressure that causes harmful blow-down effects and wear is converted into a beneficial hydrodynamic lift force. The discontinuities in the sealing surface allow fluid to generate lift forces that raise the bristles off the shaft, transforming the harmful high-pressure effect into a protective lifting action that reduces wear.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If brush seal bristles contact the rotating shaft continuously, then sealing is maintained, but efficiency decreases due to the blow-down effect from differential fluid pressures

Engineering Contradiction:

ImprovesealingVSAvoidefficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The continuous bristle contact is segmented into discrete contact regions. The first group of bristles provides sealing contact while the second group creates gaps for fluid flow. This segmentation allows the seal to maintain reliability through the first group while improving efficiency through the lift-generating flow paths created by the second group.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The discontinuities created by the shorter bristles act as intermediaries that allow fluid to pass through and generate hydrodynamic lift. These intermediary gaps mediate between the sealing function and the efficiency requirement, enabling both goals to be achieved simultaneously through the fluid-mediated lift mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design effectively reduces wear on the brush seal and the shaft by generating a hydrodynamic lifting force that offsets the blow-down effect, enhancing the seal's efficiency and service life by minimizing contact force and potential leakage.

Implementation Method 1

the sealing surface includes a plurality of discontinuities around the circumference of the brush seal for providing hydrodynamic lift force in use

Methodology Applied

Scientific EffectHydrodynamic lift:

Data Source

PatentUS9784371B2Brush seal

Publication Date: 2017.10.10 ROLLS ROYCE PLC

AI summary

Described is a brush seal for sealing between a first component and a second component which relatively rotate during normal use, comprising: an annular housing which is attached to a first component in use; a plurality of bristles each having a fixed end attached to the housing and a free end, wherein the free ends of at least some of the plurality of bristles contact the second component during normal use to provide a sealing surface, wherein the sealing surface includes a plurality of discontinuities around the circumference of the brush seal for providing hydrodynamic lifting force in use.