Gas Turbine Fan Case Liner Torque Stop Design
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Solution Overview
Problem
During fan blade out events in gas turbine engines, the high deceleration torque and axial loads generated by fan blade interaction with rubstrips can exceed the operating loads of the thermally conformable liner, leading to potential damage from bird strikes.
Innovation Solution
A fan section design with a spaced aluminum liner and frangible torque stops between the fan case and the liner, which includes a low-friction coating and an abradable rubstrip, along with a Kevlar layer, to absorb and distribute the tangential loads generated by bird strikes, ensuring the liner remains stable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the TCL is arranged directly adjacent to the fan case, then thermal growth consistency is improved, but the liner becomes vulnerable to damage from FBO-induced loads generated by bird strikes
Solution Approach 1:
The torque stops are pre-installed on the liner before assembly, positioned to engage with the fan case in the event of FBO. This preliminary positioning ensures that when a bird strike occurs, the torque stops are already in place to immediately absorb and redirect the rotational forces, protecting the liner from damage while maintaining thermal growth consistency
Solution Approach 2:
The frangible torque stops act as a cushioning mechanism designed to fail in a controlled manner during FBO events. By being pre-positioned and designed to fracture at specific load thresholds, they absorb the shock of bird strikes before the forces can damage the liner, thereby protecting the thermal growth consistency of the TCL
2Strength
If frangible torque stops are introduced to protect against FBO loads, then resistance to bird strike damage is improved, but device complexity increases
Solution Approach 1:
The torque stop system is segmented into multiple discrete units distributed around the liner circumference. Each torque stop is a separate, simple component that can be independently manufactured and installed. This segmentation allows the system to handle FBO loads through distributed failure modes while keeping each individual component simple and the overall assembly straightforward
Solution Approach 2:
The torque stops are designed as frangible, disposable components that are relatively simple and inexpensive to manufacture. In the event of FBO, they are intended to fracture and be replaced rather than protect the more expensive liner. This approach reduces device complexity by using simple, replaceable parts instead of complex, permanent protective structures
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 solution effectively reduces the transmission of high FBO-induced loads to the fan case, decreasing the risk of damage and maintaining consistent tip clearance, with the torque stops and adhesive capable of withstanding the loads generated by a 1.3 Kg bird strike, and reducing other hardware loads by 5-20%.
Implementation Method 1
rails glued with an adhesive to the aluminium liner and blocks glued with the adhesive to the fan case
Implementation Method 2
at least one of a radially inner surface of the fan case and a radially outer surface of the liner includes a low-friction coating
Implementation Method 3
the liner includes an abradable rubstrip adjacent to tips of the fan blades
Data Source
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AI summary
A fan case for a gas turbine engine includes a fan case surrounding a fan with fan blades. A liner is disposed between the fan case and the fan and is spaced a radial distance from the fan case. A torque stop is arranged between the fan case and the liner. A method for reducing fan case liner loads is also disclosed.