Turbine Case Seal Baffle for Cantilever Wall Vibration Damping
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Solution Overview
Problem
Existing aircraft engine turbine case structures face challenges in managing dynamic excitation and vibration-induced stress due to the cantilevered configuration of inner walls, which can lead to crack formation and increased stress levels.
Innovation Solution
Incorporation of a damping seal baffle, such as a compliant sheet metal body, mounted to the inner case and configured to move along a seal platform surface, which dampens the inner wall's deflection and reduces vibration-induced stresses by maintaining contact over varying thermal conditions, with an axial baffle stopper limiting further deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cantilevered inner wall configuration is used in the turbine case, then the structural support for the turbine section is improved, but vibration-induced stress and deflection increase leading to potential crack formation
Solution Approach 1:
A damping seal baffle is introduced as an intermediary component between the inner case and the cantilevered inner wall. This baffle acts as a mediator that absorbs and dissipates vibration-induced stresses through friction and deformation, preventing stress transmission to the cantilevered wall while maintaining structural support. The baffle includes a damping portion that contacts the inner wall and a seal portion that maintains sealing while allowing controlled movement.
Solution Approach 2:
The damping seal baffle utilizes material parameter changes through elastomeric or compliant materials that can deform and absorb vibrations. The baffle's material properties are selected to provide optimal damping characteristics, changing its stiffness and friction characteristics based on thermal and vibrational conditions to reduce stress on the cantilevered structure.
2Reliability
If a rigid seal structure is used at the interface between inner case and cantilevered wall, then sealing is maintained, but thermal expansion and contraction cause stress and potential failure
Solution Approach 1:
The seal portion of the damping seal baffle is designed to be dynamic rather than rigid, allowing it to move axially and radially in response to thermal expansion and contraction. The seal maintains contact with the cantilevered inner wall through controlled elastic deformation, accommodating thermal movements while maintaining sealing effectiveness throughout the operating temperature range.
Solution Approach 2:
The damping seal baffle incorporates flexible elastomeric or compliant material portions that can deform to maintain sealing contact. The seal portion acts as a flexible element that conforms to thermal expansion and contraction of the metal components, maintaining reliable sealing without transmitting thermal stress to the cantilevered structure.
3Stress or pressure
If the damping seal baffle is allowed to move freely along the seal platform surface, then vibration damping is improved, but excessive deflection may occur
Solution Approach 1:
A stopper feature is provided that preliminarily prevents excessive deflection of the damping seal baffle. The stopper acts as a mechanical constraint that engages if the baffle deflects beyond a predetermined amount, providing counter-action to prevent excessive movement while allowing normal vibration damping operation within safe deflection limits.
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 damping seal baffle effectively reduces vibration-induced stresses and maintains structural integrity by damping the inner wall's deflection, thereby preventing crack formation and enhancing the durability of the turbine case structure.
Implementation Method 1
The damping seal baffle is disposed in contact with the seal platform surface and configured to move along the seal platform surface, which dampens the inner wall's deflection and reduces vibration-induced stresses
Implementation Method 2
The damping seal baffle... configured to move along the seal platform surface, which dampens the inner wall's deflection and reduces vibration-induced stresses
Implementation Method 3
maintaining contact over varying thermal conditions
Implementation Method 4
Incorporation of a damping seal baffle, such as a compliant sheet metal body
Data Source
AI summary
A gas turbine engine includes a turbine section, a turbine case, an inner case, and a damping seal baffle. The turbine section extends along a rotational axis of the gas turbine engine. The turbine case includes a cantilevered inner wall. The cantilevered inner wall extends circumferentially about the rotational axis. The cantilevered inner wall extends between and to an upstream axial end and a downstream axial end. The upstream axial end is disposed at and downstream of the turbine section. The cantilevered inner wall forms a seal platform surface. The inner case extends circumferentially about the rotational axis. The inner case is disposed radially inward of the upstream axial end. The damping seal baffle extends circumferentially about the rotational axis. The damping seal baffle is mounted to the inner case. The damping seal baffle is disposed in contact with the seal platform surface.