Brush Seal Backing Plate Layout for Compact Turbine Cavities
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Solution Overview
Problem
In gas turbine engines, the compact nature of the cavity between the blade outer air seal and vane limits the space for sealing structures, leading to bristle yield and leakage due to high pressure differentials, as the bristles of brush seals can blow-over or bend, causing gaps and inefficiencies in sealing.
Innovation Solution
A seal structure featuring a brush seal with a bristle pack and a backing plate, where a spring is used to force the bristle pack toward the axial and radial surfaces, and the bristle pack is welded to the backing plate, allowing for optimized contact and reduced overhang lengths to minimize deflection and leakage, with the backing plate made from cobalt- or nickel-based alloys for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a brush seal is used in a compact cavity, then the sealing function is provided, but the bristles blow-over or bend at high pressure differentials causing leakage
Solution Approach 1:
The backing plate is segmented into multiple surfaces (axial surface and radial surface) that contact different cavity walls, distributing the sealing function across multiple contact points. This segmentation allows the bristle pack to be supported from multiple directions, preventing blow-over and bending at high pressure differentials.
Solution Approach 2:
The spring mechanism applies a counteracting force to balance the high pressure differential acting on the brush seal. By forcing the bristle pack toward the axial surface, the spring creates a counterbalancing effect that prevents bristle deflection and maintains sealing integrity under pressure loads.
2Volume of moving object
If the cavity is made compact to reduce engine size, then the sealing space is limited, but the bristles have insufficient support leading to yield and leakage
Solution Approach 1:
The backing plate utilizes multiple dimensions by contacting both axial and radial surfaces of the cavity. This multi-dimensional contact approach maximizes the use of limited cavity space, providing adequate bristle support without requiring increased cavity volume. The bristle pack is positioned to extend beyond both axial and radial surfaces, creating a multi-directional sealing configuration.
Solution Approach 2:
Different regions of the backing plate are optimized for specific functions: the axial surface contact region provides support against axial pressure loads, while the radial surface contact region provides support against radial pressure loads. This localized optimization allows the seal to maintain high reliability in a compact cavity by tailoring the backing plate structure to local stress conditions.
3Reliability
If the bristle pack is extended beyond the backing plate to improve sealing contact, then the sealing coverage is increased, but the overhang length causes deflection under pressure
Solution Approach 1:
The patent optimizes the overhang parameters by limiting the axial overhang to ≤0.010 inches and the radial overhang to ≤0.010 inches. These controlled parameter changes ensure sufficient sealing contact while minimizing deflection under pressure. The spring force parameter is also optimized to provide adequate contact pressure without causing excessive bristle deformation.
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
The solution effectively reduces bristle deflection and leakage by ensuring consistent contact with both axial and radial surfaces, maintaining sealing integrity under pressure differentials and during engine operation, including start-up and shut-down.
Implementation Method 1
A spring may be in operable communication with retention structure. The spring may force the bristle pack toward the axial surface.
Implementation Method 2
the seal structure may further comprise a weld bonding the bristle pack to the backing plate
Data Source
AI summary
A seal structure may comprise a cavity defined at least partially by an axial surface and a radial surface. A brush seal may be disposed in the cavity. The brush seal may comprise a bristle pack and a backing plate coupled to the bristle pack. A first surface of the backing plate may contact the axial surface, and a second surface of the backing plate may contact the radial surface.