Acoustic Structure Thermal Fuse Fire Protection
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Solution Overview
Problem
Existing acoustic structures in bypass ducts of gas turbine engines face challenges in withstanding fire without compromising structural integrity or increasing weight and cost, as current fire protection methods are thermally protective but not structurally active and complicate maintenance.
Innovation Solution
Incorporating a thermal fuse in the radially-outward skin of the bypass duct, which melts at a threshold temperature to open a cooling path, allowing bypass air to flow across the skin and provide cooling while maintaining structural integrity, thereby preventing pressure resisting wall failure during a fire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If external blankets, coatings or metallic shields are added to protect the acoustic structure from fire, then the thermal protection is improved, but the structural parasitism, cost, maintainability and inspectability are worsened
Solution Approach 1:
The patent merges the fire protection function with the acoustic structure itself by making the second skin load-bearing and integrating the cooling flow path directly into the skin structure. This eliminates the need for separate external blankets, coatings or metallic shields, as the acoustic structure becomes its own fire protection system through the thermal fuse mechanism that opens cooling paths when exposed to fire temperatures.
2Temperature
If external blankets, coatings or metallic shields are added to protect the acoustic structure from fire, then the thermal protection is improved, but the cost and maintainability are worsened
Solution Approach 1:
The patent combines multiple functions into the acoustic structure itself: the second skin serves as both a load-bearing structural element and a fire protection barrier. The thermal fuse blocks integrate fire response functionality directly into the skin, eliminating the need for separate protective layers that would increase cost and complicate maintenance procedures.
3Temperature
If external blankets, coatings or metallic shields are added to protect the acoustic structure from fire, then the thermal protection is improved, but the inspectability and reparability are worsened
Solution Approach 1:
The patent makes the fire protection system transparent to inspection by integrating it into the visible acoustic structure. The second skin and thermal fuse blocks form part of the acoustic assembly itself, allowing inspectors to examine the fire protection features alongside the acoustic components during routine inspections, rather than requiring separate access to hidden protective layers.
4Strength
If the second skin is made load-bearing to support pressure differential, then the structural integrity is improved, but the fire resistance is worsened without cooling paths
Solution Approach 1:
The patent prepares the second skin in advance for fire exposure by pre-configuring thermal fuse blocks at strategic locations. These blocks remain closed during normal operation to maintain structural integrity, but are designed to automatically open when exposed to fire temperatures, thereby pre-establishing cooling paths that will activate only when needed for fire protection.
Solution Approach 2:
The patent makes the second skin dynamically responsive to temperature changes by incorporating thermal fuse blocks that transition from closed to open states based on thermal conditions. This dynamic behavior allows the skin to maintain structural integrity during normal operation while automatically providing fire protection when exposed to high temperatures, adapting its permeability to cooling flows based on the thermal environment.
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 thermal fuse solution effectively enhances the structural resistance of the acoustic structure to fire by allowing controlled cooling, preventing pressure resisting wall failure and maintaining structural integrity without adding parasitic weight or cost, while simplifying maintenance and inspection.
Implementation Method 1
the thermal fuse is configured to melt upon reaching a threshold temperature, thereby opening a gas path from the bypass air passage across the second skin
Implementation Method 2
cooling the second skin by circulation of cooling air flowing across the second skin
Data Source
AI summary
A bypass air passage can be provided between a radially-outer wall of a bypass duct and an engine core, the radially-outer wall having a first, radially inner skin apertured and exposed to the bypass air passage, and a second skin radially-outwardly offset from the first skin, the second skin having an aperture blocked by a thermal fuse, wherein the thermal fuse is configured to melt upon reaching a threshold temperature, thereby opening a gas path from the bypass air passage across the second skin, via the aperture.