Floating Non-Contact Seal With Three Beams for Stiffness and Fatigue
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Solution Overview
Problem
Existing sealing systems in aircraft engines face challenges in simultaneously meeting the requirements of sufficient stiffness to maintain clearance between static and rotating engine structures while avoiding over-stressing and low cycle fatigue, which is difficult to achieve with conventional designs.
Innovation Solution
Incorporating at least three beams in a floating, non-contact seal, where each beam has axial ends coupled to a shoe and a ring structure, allowing for increased overall stiffness without increasing stress, and enabling the seal to maintain operational flexibility and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the beams are made stiffer to satisfy the natural frequency limit and maintain clearance, then the stiffness requirement is met, but the beam thickness increases beyond the maximum threshold causing over-stressing and low cycle fatigue
Solution Approach 1:
The seal structure is divided into multiple discrete beams (at least three beams) instead of using a single thick beam. Each beam can be made thinner to reduce stress while the collective arrangement of multiple beams provides the necessary overall stiffness through distributed structural support.
2Stability of the object's composition
If a single thick beam is used to increase stiffness, then the natural frequency requirement is satisfied, but the beam becomes overly stressed during relative movements
Solution Approach 1:
The structural support function is segmented across multiple thin beams rather than concentrated in one thick beam. This distribution maintains the required natural frequency and stability while reducing the stress on any individual beam during operational movements.
Solution Approach 2:
Multiple individual beam elements are combined to function collectively as a unified structural support system. The combined stiffness of multiple thin beams achieves the required natural frequency without the excessive stress that would occur in a single equivalent-thickness beam.
3Stability of the object's composition
If the beam thickness is increased to meet stiffness thresholds, then structural stability is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of manufacturing one complex thick beam component, the structure uses multiple simpler thin beam elements. This segmentation simplifies manufacturing processes for each individual beam while achieving the required structural stability through their collective arrangement.
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 use of multiple beams enhances the stiffness of the sealing system, effectively meeting stiffness and low cycle fatigue requirements, while maintaining similar shoe travel characteristics as two-beam systems, and ensures continued operation even if one beam becomes inoperable.
Implementation Method 1
the beams must be compliant enough to avoid over-stressing them (frequently referred to as having a low cycle fatigue (LCF)) during relative movements/deflections between the structures 206 and 212
Implementation Method 2
As the air flows passes teeth 238 of the shoe 236 (where the teeth 238 are frequently formed as thin knife-edges), an associated pressure field changes. This change induces the shoe 236 to move, e.g., the radial reference direction until an equilibrium condition is obtained.
Data Source
AI summary
Aspects of the disclosure are directed to a floating, non-contact seal comprising: a shoe, and at least three beams, each beam having a first axial end and a second axial end, where the first axial ends are coupled to the shoe and the second axial ends are coupled to a ring structure. Aspects of the disclosure are directed to an engine comprising: a first structure, a second structure configured to rotate relative to the first structure, and a floating, non-contact seal that interfaces the first structure and the second structure, where the seal includes: a shoe, and at least three beams, where each beam has a first axial end and a second axial end, where the first axial ends are coupled to the shoe and the second axial ends are coupled to a ring structure.