Doubler Attachment System for Engine Casing Load Distribution
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Solution Overview
Problem
Military gas turbine engines face significant load stresses due to the high-speed rotation of fan assemblies, particularly during a 'blade out' condition, which existing attachment systems fail to adequately manage without impeding airflow or adding excessive weight.
Innovation Solution
A doubler attachment system that includes a doubler plate with radial surfaces and bolts to securely couple struts to engine casings, enhancing the structural integrity of the front frame assembly while maintaining aerodynamic airflow by using T-flanges and doubler assemblies to distribute loads effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If additional struts are added to connect inner and outer casings, then load stress resistance is improved, but airflow is impeded and weight increases
Solution Approach 1:
The doubler attachment system divides the strut assembly into modular components: the doubler plate, the strut with T-flanges, and the bolt connections. This segmentation allows the load-bearing function to be concentrated in specific reinforcement zones without requiring additional full-length struts that would impede airflow across the entire engine inlet.
Solution Approach 2:
The doubler plate provides localized reinforcement at critical attachment points where struts connect to the engine casing. This local quality enhancement concentrates structural strength where needed most (at the connection interfaces) without adding material throughout the entire flowpath, thus maintaining airflow efficiency while improving load stress resistance.
2Reliability
If additional bolts or welded joints are added within inlet flowpath, then attachment security is improved, but airflow is impeded
Solution Approach 1:
The T-flange configuration extends the attachment interface into a three-dimensional structure that distributes bolts across multiple planes and surfaces. This dimensional approach allows secure attachment with fewer individual bolt holes in any single airflow cross-section, reducing the cumulative blockage effect compared to traditional flat plate attachments.
Solution Approach 2:
The doubler plate acts as an intermediary element between the strut T-flanges and the engine casing. It provides a reinforced intermediate surface that distributes attachment loads more effectively, allowing for secure bonding with reduced numbers of fasteners and smaller fastener holes, thereby minimizing airflow interference while maintaining attachment security.
3Strength
If greater quantity of struts is used, then load stress resistance is improved, but weight increases
Solution Approach 1:
The attachment system employs composite construction combining the doubler plate, T-flange strut components, and bolt assemblies. This composite approach creates a structurally optimized system where each material and component is positioned to maximize strength-to-weight ratio, providing enhanced load stress resistance without the linear weight increase that would result from simply adding more traditional struts.
Data Source
AI summary
A doubler attachment system is provided for fixedly coupling a strut to an engine casing. The strut includes at least one flanged end configured to mate with the engine casing. The doubler attachment system includes a doubler plate having a first radial surface and a second opposing radial surface. The first radial surface is configured to mate with and conform to a contour of the at least one flanged end of the strut. The doubler attachment system further includes at least two bolts fixedly attached to the doubler plate at the first radial surface. The at least two bolts extend radially away from the first radial surface and toward the engine casing.