Sealed Torque Box in Gas Turbine Mid-Turbine Frame
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Solution Overview
Problem
Existing mid-turbine frames for gas turbine engines face challenges in efficiently managing cooling air and oil leaks, which can lead to fluid exchange between the torque box and adjacent engine sections, potentially causing damage and reducing engine efficiency.
Innovation Solution
The mid-turbine frame incorporates a sealed torque box design with redirection tubes for cooling air and sealed service lines, ensuring that cooling air bypasses the torque box and all openings are sealed to minimize fluid exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air is routed through the torque box to reach the turbine section, then the cooling function is provided, but fluid exchange between the torque box and adjacent engine sections occurs which can cause damage and reduce efficiency
Solution Approach 1:
The patent divides the mid-turbine frame into functionally separated zones: a sealed torque box for structural support and a dedicated cooling air passage for fluid flow. The spoke structure segments the cooling air path to bypass the torque box entirely, preventing oil contamination while maintaining cooling effectiveness to the turbine section.
Solution Approach 2:
The patent introduces redirection tubes as intermediary components that transfer cooling air from the spoke cooling passages to the turbine section without allowing direct communication with the torque box interior. This intermediary structure enables cooling function while blocking the harmful fluid exchange pathway.
2Reliability
If service lines are opened to allow oil flow to bearings, then bearing lubrication is provided, but openings create potential leak paths into the torque box
Solution Approach 1:
The patent employs flexible lip seals at the service line openings to create a dynamic barrier that allows bearing lubrication while preventing oil from leaking into the torque box. The lip seal configuration provides reliable sealing against rotational service lines while maintaining bearing access to lubrication.
3Reliability
If the torque box is sealed to prevent fluid exchange, then reliability is improved, but cooling air routing becomes more complex
Solution Approach 1:
The patent merges the cooling air routing function directly into the spoke structure by forming cooling passages within the spoke itself. This integration eliminates the need for separate external routing components, reducing overall system complexity while achieving reliable sealing of the torque box.
Solution Approach 2:
The patent resolves the sealing complexity by changing the dimensional approach: instead of trying to seal openings in the torque box walls, the cooling air is routed through a different dimension - the spoke structure - which naturally bypasses the torque box interior. This dimensional shift simplifies the sealing requirement.
Data Source
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AI summary
A mid-turbine frame (57) for a gas turbine engine (20) includes an inner frame case (120) defining a sealed torque box cavity (140). Multiple spokes (110) protrude radially outward from the inner frame case (120), and at least one service line (130) is connected to the inner frame case (120). A method comprises sealing every opening in the torque box such that passage of fluid from the mid-turbine frame into said torque box is minimized.