Gas Turbine Shroud Deflection Control via Segmented Design
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Solution Overview
Problem
The existing systems for gas turbine engines face challenges in preventing the deflection and dislodgment of fan exit stators due to ingestion of objects like birds, which can lead to undesirable movement of the outer diameter shroud.
Innovation Solution
The proposed solution involves an outer diameter shroud with an annular body and a shroud flange that is coupled to the engine case, featuring increased thickness transitions and integral brackets, as well as a bayonet or band system to resist radially outward movement, ensuring the stators remain securely in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the outer diameter shroud uses a thin-walled annular body for weight reduction, then the weight decreases, but the shroud becomes prone to radial deflection and stator dislodgment under impact loads
Solution Approach 1:
The outer diameter shroud is divided into a thin-walled annular body and separate radial support elements (ribs or struts) that extend from the annular body to the shroud flange. This segmentation allows the main body to remain lightweight while the support elements provide necessary radial strength to prevent deflection and stator dislodgment under impact loads.
Solution Approach 2:
The outer diameter shroud employs a composite structure combining a thin-walled annular body with integrated radial support elements. This composite design achieves optimal balance between weight reduction and structural strength, allowing the shroud to resist radial forces from bird strikes or foreign object damage while maintaining minimal weight.
2Weight of moving object
If the shroud flange is made thin for weight reduction, then the overall weight decreases, but the flange becomes insufficient to resist radially outward movement under impact
Solution Approach 1:
The shroud flange incorporates increased thickness specifically in the radial dimension where strength is needed to resist outward movement, while maintaining thin walls in the axial and circumferential dimensions. This selective dimensional reinforcement ensures stator retention reliability under impact without unnecessarily increasing overall weight.
Solution Approach 2:
The shroud flange features localized thickness variation, being thicker at critical regions that resist radially outward movement during impact events, while remaining thin in non-critical areas. This local quality approach provides necessary reliability for stator retention while minimizing overall weight penalty.
3Strength
If the annular body axial length is increased to improve stator retention, then the retention strength improves, but the engine inlet area and airflow are reduced
Solution Approach 1:
The stator retention function is segmented between the annular body (which provides circumferential positioning) and the radial support elements (which provide axial retention). This allows the annular body to maintain a minimal axial length that preserves engine inlet area, while the radial support elements provide the necessary retention strength through their structural configuration.
Solution Approach 2:
Instead of increasing the annular body axial length to improve retention, the design uses radial support elements that extend in the radial dimension to provide the necessary retention strength. This dimensional shift allows adequate stator retention without encroaching on the engine inlet area.
Data Source
AI summary
An outer diameter shroud for retaining a stator of a gas turbine engine having an axis includes an annular body positioned around the axis, extending in an axial direction, and defining a plurality of slots each configured to receive a portion of one of a plurality of stators. The outer diameter shroud further includes a shroud flange coupled to the annular body, extending in a direction perpendicular to the annular body, and configured to be fastened to a case of the gas turbine engine.