Jet Engine Exhaust Casing Link with Fusible Rods
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Solution Overview
Problem
Existing turbofan engine connections between the outer duct of the fan channel and the exhaust casing are overly massive due to the need to withstand unbalanced forces from blade rupture, which increases the overall weight and structural complexity.
Innovation Solution
A hyperstatic connection system using a combination of fusible and non-fusible connecting rods, where the first connecting rods buckle under specific loads and the second rods take over force transmission, allowing for reduced mass while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the connection elements are dimensioned to withstand forces from blade rupture, then the reliability is improved, but the weight increases
Solution Approach 1:
The connection system is divided into two distinct segments: fusible connecting rods designed to break under extreme loads and non-fusible connecting rods designed to remain intact. This segmentation allows each segment to be optimized for its specific function, reducing the overall mass compared to a unified structure designed for maximum load capacity.
Solution Approach 2:
The mechanical properties of the connecting rods are changed by introducing a fusible element with a predetermined breaking load that is lower than the blade rupture load. This parameter change creates a controlled failure mode that protects the overall structure while reducing the mass requirements of the connection assembly.
2Strength
If the structural ring is sized to withstand loads over its entire circumference, then the strength is improved, but the weight increases
Solution Approach 1:
The structural ring design incorporates local quality by concentrating reinforcement only in the regions where forces are transmitted during blade rupture events, rather than uniformly strengthening the entire circumference. This allows the ring to maintain sufficient strength while reducing unnecessary material in low-stress areas.
3Reliability
If all connecting rods are designed to transmit rupture forces, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The connection system transitions from a static configuration where all rods must withstand maximum loads to a dynamic system where the fusible rods are designed to fail under specific conditions, automatically redistributing forces to the non-fusible rods. This dynamic behavior simplifies the design requirements for individual components.
Data Source
Figure 1~3
Figure 4~7
AI summary
The present invention relates to an assembly including an outer ring (23) of an exhaust casing, a structural ring (21) of an external duct of the fan channel and of a two-flow jet engine (10) that is concentric relative to the outer ring (23) of the exhaust casing, and at least one first and second linking arm or rod (40) forming a hyperstatic link by being attached by one end to the outer ring (23) of the exhaust casing and, by the other end, to said structural ring (21). The assembly is characterised in that the link formed by the first linking arm or rod (40A-D) is arranged such as to break when a predetermined load is exceeded, and the second linking arm or rod (40E-F) is arranged such as to form a force-transmission path between said rings (21, 23) when said link is broken.