Fan Containment Hook With Dynamic Fasteners
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Solution Overview
Problem
The existing fan containment systems face a design conflict in balancing the need for the fan track liner to be hard enough to withstand ice and foreign object impacts while allowing a detached fan blade to penetrate and be contained, without altering the preferred trajectory for interception by the hook, which affects the structural integrity and weight of the system.
Innovation Solution
The fan containment system incorporates an annular casing element with a hook that has tabs protruding in a rearward direction, which are integrally formed and connected to the fan track liner via fasteners configured to fail at a predetermined load, allowing the fan track liner to move towards the annular casing element when impacted by a released fan blade, thus mitigating the risk of cracking and enhancing containment efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the fan track liner is made hard to withstand ice and foreign object impacts, then resistance to operational impacts is improved, but the ability of a detached fan blade to penetrate and be contained deteriorates
Solution Approach 1:
The fan track liner is divided into multiple panels that can move independently relative to the hook. This segmentation allows the liner to respond differently to various forces: remaining rigid against ice impacts while allowing blade penetration through controlled panel movement.
Solution Approach 2:
The connection between the fan track liner and hook is made dynamic through fasteners configured to fail at predetermined loads. This allows the liner to transition from a fixed state during normal operation to a movable state during blade containment, resolving the contradiction between hardness and penetrability.
2Reliability
If the fan track liner is made soft to allow blade penetration, then blade containment capability is improved, but resistance to ice and foreign object impacts deteriorates
Solution Approach 1:
Dividing the liner into movable panels allows the system to exhibit soft behavior only where and when needed for blade containment, while maintaining hard resistance elsewhere during normal operation.
Solution Approach 2:
The mechanical properties of the fan track liner system are changed dynamically through fastener failure. The liner transitions from a high-strength state during normal operation to a low-strength state during blade containment, allowing optimization of both contradictory requirements.
3Reliability
If the hook is made structurally stronger to improve containment integrity, then reliability is improved, but weight increases
Solution Approach 1:
The hook system uses dynamic fasteners that remain strong during normal operation but fail at predetermined loads to allow blade containment. This eliminates the need for excessive structural strength throughout, reducing weight while maintaining reliability.
Solution Approach 2:
The structural parameters of the hook connection are changed dynamically through fastener failure. The system maintains high strength during normal operation for reliability but transitions to a lower strength state during blade containment, avoiding the need for permanently oversized structural components.
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 enhances the structural integrity of the hook and containment system, ensuring effective containment of detached fan blades while maintaining resistance to operational impacts, such as ice, without increasing weight or compromising the hook's integrity.
Implementation Method 1
when the fan track liner is impacted by a released fan blade
Data Source
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AI summary
A fan (12) containment system for fitment around an array of radially extending fan blades (40) mounted on a hub in an axial gas turbine engine (10). The fan (12) containment system comprises an annular casing element (352) for encircling an array of fan blades (40). An annular fan track liner (356) is positioned substantially coaxial to the annular casing element (352). A hook (354) projects in a generally radially inward direction from the annular casing element (352) and is positioned axially forward of an array of fan blades (40) when the fan (12) containment system is fitted around said fan blades (40). Tabs (370) protrude from the hook (354) in a generally rearward direction and are spaced circumferentially along the hook (354). Fasteners (366) connect the fan track liner (356) to the tabs (370). The fasteners are configured so as to permit movement of the fan track liner (356) towards the annular casing element (352) when the fan track liner (356) is impacted by a released fan blade (40).