Turbomachine Exhaust Case Threaded Assembly Mass Reduction
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Solution Overview
Problem
The existing turbomachine assemblies with bolted connections between the exhaust casing and downstream components like exhaust cones or mixers are heavy due to the use of bolts and scalloped flanges, which increases mass and manufacturing costs.
Innovation Solution
The solution involves replacing the bolted connections with threaded connections on the radially external and internal surfaces of the exhaust casing, allowing the exhaust cone, mixer, or nozzle to be screwed onto the casing, eliminating the need for bolts and extra thickness, thereby reducing mass and simplifying manufacturing and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bolted connections with scalloped flanges are used to assemble the exhaust casing and downstream parts, then the mechanical strength and reliability of the connection are improved, but the mass of the assembly increases significantly due to bolts and extra thickness
Solution Approach 1:
The patent removes the bolts and scalloped flanges from the assembly, extracting the unnecessary components that contribute to mass while maintaining connection functionality through alternative means
Solution Approach 2:
Instead of adding bolts and extra thickness to achieve connection, the patent inverts the approach by using a precise interference fit with a small clearance, eliminating the need for additional fastening components
2Strength
If bolts and scalloped flanges are used for assembly, then the mechanical strength of the connection is ensured, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent eliminates bolts and scalloped flanges from the design, removing complex components and simplifying the overall assembly structure while maintaining connection integrity
Solution Approach 2:
The patent merges the connection function into the basic geometric fit between mating surfaces, combining the alignment and connection functions into a single simplified interface without separate fastening components
3Strength
If extra thickness is added to embed bolt heads, then the mechanical strength of the connection is improved, but the mass of the parts increases
Solution Approach 1:
The patent removes the need for extra thickness by eliminating bolts entirely, extracting the unnecessary material that would be required to embed bolt heads while maintaining connection strength through precise geometric fitting
Solution Approach 2:
The patent changes the connection parameter from mechanical fastening with embedded heads to a precise interference fit with controlled clearance, optimizing the dimensional parameters to achieve strength without excess mass
Data Source
Figure 1~2b
Figure 3a~3b
Figure 4a~4b
AI summary
The invention relates to an assembly comprising: - a turbomachine exhaust case (110) that includes an external sleeve and an internal sleeve inside the former, both sleeves extending concentrically about a turbomachine axis, and also includes a plurality of arms extending radially between the sleeves; and - an annular part (130) that is centered about the axis, is mounted on one sleeve of the exhaust case, and is located downstream of the exhaust case in the direction in which the air flows inside the turbomachine; the assembly is characterized in that the annular part and the sleeve of the exhaust case on which the annular part is mounted each have a circumferential thread (131, 115), said threads cooperating with each other in order to allow the annular part to be screwed onto the sleeve of the exhaust case.