Gas Turbine Synchronizing Assembly Composite Bumper Bushing
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Solution Overview
Problem
Composite bumpers in gas turbine engine synchronizing assemblies fatigue and crack under clamping force, requiring frequent service due to the precise machining requirements of discrete locating pins and the inherent weaknesses of composite materials.
Innovation Solution
A bushing extending through a counterbored hole in the bumper applies a clamping load through a fastener, minimizing stress on the composite material, and a deformable shim with a visible tab ensures proper assembly and maintains vane angle accuracy, while a snap bearing and polymeric bearing enhance retention and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a composite bumper is secured to the synchronizing ring using fasteners with clamping force, then the bumper is firmly attached, but the composite material fatigues and cracks over time
Solution Approach 1:
A bushing is introduced as an intermediary component between the fastener and the composite bumper. The bushing bears the clamping load from the fastener, preventing direct stress application to the composite material. This mediator protects the composite bumper from fatigue cracking while maintaining secure attachment to the synchronizing ring.
2Manufacturing precision
If a discrete locating pin is used to prevent rotation of the box during installation, then positioning is achieved, but the pin requires very precise machining
Solution Approach 1:
The discrete locating pin is extracted from the assembly and replaced by a bushing with an integrated locating feature. The bushing's outer surface includes a cylindrical locating feature that engages with a corresponding feature on the synchronizing ring, eliminating the need for separate precision-machined locating pins while maintaining positioning accuracy.
3Ease of operation
If the composite material is loaded under clamping force to secure the bumper, then the bumper is firmly attached, but the material fatigues and cracks requiring service
Solution Approach 1:
The bushing serves as a protective intermediary that decouples the clamping force from the composite bumper material. By absorbing and distributing the clamping load, the bushing prevents stress concentration in the composite material, eliminating fatigue cracking while maintaining secure attachment throughout the service life.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A synchronizing assembly (31) for a gas turbine engine (10) includes a synchronizing ring (34). A composite bumper (38) is secured to the synchronizing ring (34) by a fastener (50). A structure is arranged between the bumper (38) and the synchronizing ring (34). The fastener (50) applies a first load through the structure to the synchronizing ring (34) and a second load through the bumper (38). The second load is substantially less than the first load. In one example, the structure includes a bushing (48) that extends through a hole (44) in the bumper (38). The bushing (48) is proud of the hole (44) on the other side of the bumper (38) and protrudes into the counterbore (66). The fastener (50) is arranged in the bushing (48) and applies a clamping load through the bushing (48) to secure the bumper (38) to the synchronizing ring (34).