Brush Seal Bristle Network Self-Centering Geometry
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Solution Overview
Problem
Existing brush seal designs for turbojet engines face issues with wide dimensional tolerances and lack of rotational maintenance, leading to potential leaks and instability under high temperature and radial expansion conditions.
Innovation Solution
A brush seal design with a cylindrical cage and wedge structure, where the bristle network is directly inserted into an outer casing closed by crimping, ensuring tight tolerances and rotational maintenance through a composite structure with metal-metal contact and concave bearing surfaces for self-centering and reduced shear stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a C-shaped cage is used to maintain and protect the network of bristles, then the brush seal can withstand high temperatures and radial differential expansions, but the reclosure of the C must be carried out by stamping or flow forming which give wide dimensional tolerances
Solution Approach 1:
The invention removes the C-shaped cage entirely from the brush seal design. Instead, the brush seal consists of a central ring around which the network of bristles is wound, with the ends of the bristles extending radially outward. This extraction of the C-shaped cage eliminates the stamping or flow forming processes that produced wide dimensional tolerances, while the bristle network itself provides the necessary maintenance and protection functions.
Solution Approach 2:
Rather than using a C-shaped cage to hold and protect the bristles from the outside, the invention inverts the approach by having the bristles wind around a central ring structure. The bristle network itself becomes the protective element, with the ends extending outward to maintain contact with the rotor surface, eliminating the need for external cage reclosure processes.
2Manufacturing precision
If a two-part housing with crimping is used to mount the brush seal, then tight geometrical tolerances are achieved, but the size of the brush seal module increases making it more difficult to house
Solution Approach 1:
The invention merges the mounting functions into a single integrated housing structure rather than using separate two-part housings with crimping. The housing includes a radially inwardly directed flange that provides both structural support and sealing surface in one piece, eliminating the need for additional housing parts and reducing overall module size while maintaining tight tolerances.
Solution Approach 2:
The housing design uses a radially inwardly directed flange that extends in the radial dimension rather than requiring additional axial height from separate parts. This dimensional approach allows tight geometrical tolerances to be achieved through the flange structure without increasing the axial size of the brush seal module, making it easier to house in constrained spaces.
3Stability of the object's composition
If axial compression is used to ensure rotational retention of the brush seal, then the brush seal remains stable in rotation, but loss of compression due to differential expansions implies loss of rotational retention
Solution Approach 1:
The brush seal design allows the bristle network to self-adjust to radial differential expansions through its inherent flexibility. The bristles maintain continuous contact with the rotor surface through their own elastic properties rather than relying on external axial compression, so the seal automatically compensates for thermal expansion and maintains rotational retention without additional mechanisms.
Solution Approach 2:
The invention changes the mechanism from fixed axial compression to dynamic bristle deflection. The bristles can deflect radially to accommodate changes in radial clearance due to thermal expansion, maintaining stable rotational contact through parameter changes in bristle position rather than requiring constant axial compression force.
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 achieves precise sealing and rotational stability with optimized geometry and reduced bulk size, ensuring reliable crimping and maintaining the bristle network close to the rotor while preventing ruffling and leaks.
Implementation Method 1
The cage is closed by crimping, which makes it possible to ensure tightness vis-à-vis the outside between two pieces of different compartments enclosing said joint
Implementation Method 2
The structure ultimately comprises two diameters: a diameter formed by the ends of the bristles, hereinafter referred to as the 'brush diameter', and another in the winding zone around the core, hereinafter referred to as the 'smooth diameter'
Implementation Method 3
An important aspect of the invention consists in optimizing the geometry of the two bearing surfaces of said composite structure. On the cage as on the wedge, concave buckets are hollowed out axially on said radial returns rather than opting for rectilinear support surfaces
Implementation Method 4
The brush seal has a sufficient level of tightness for such applications, can withstand high temperatures if constructed with suitable materials, and has good adaptability to radial differential expansions
Data Source
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AI summary
The seal comprises a housing made up of two portions (1, 2) clamped together as a close and fluid tight fit at interfaces (15, 6b) and a composite structure comprising, inside the housing, a core (24) that is advantageously soft and elastic and a winding (20) of brush bristles. This structure extends directly facing the opposing internal faces (9, 10) of the housing, which compresses them and has an arched shape of slightly larger radius of curvature. The composite structure is kept in a precise position firmly but without stress.