Multiwall Tube Fitting for Gas Turbine Bearing Lubrication
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining separation of fluids in double wall tubes, leading to issues like oil coking and blockages due to excessive heating, which affects lubricant delivery to bearing systems.
Innovation Solution
A fitting system for multiwall tubing assemblies is introduced, featuring concentric tubes with a frustoconical mating surface and a polygonal flange for secure installation, ensuring fluid separation and effective lubricant delivery to bearing systems while minimizing heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If double wall tubes are used for fluid transport, then fluid delivery capability is improved, but fluid separation maintenance becomes difficult
Solution Approach 1:
The fitting is divided into an inner portion and an outer portion that can be separately assembled. The inner portion fits within the inner tube while the outer portion engages with the outer tube, creating segmented connection points that maintain fluid separation throughout the assembly.
Solution Approach 2:
The inner portion of the fitting is nested within the inner tube, while the outer portion engages with the outer tube. This nested configuration allows the fitting to connect both tubes simultaneously while maintaining their separate fluid pathways without interference.
2Ease of manufacture
If conventional tube fittings are used, then installation is simple, but oil coking and blockages occur due to excessive heating
Solution Approach 1:
The fitting acts as an intermediary thermal barrier between the hot outer tube environment and the lubricant in the inner tube. By engaging both tubes and maintaining their separation, the fitting prevents direct heat transfer that would cause oil coking.
Solution Approach 2:
The fitting is designed with thermal protection features that prevent excessive heating before it can cause oil coking. The structure provides inherent thermal insulation and heat dissipation pathways that protect the lubricant from reaching coking temperatures.
3Reliability
If multiwall tube fittings are designed with fluid separation features, then fluid separation is maintained, but device complexity increases
Solution Approach 1:
The fitting merges the functions of connecting the inner tube and outer tube into a single integrated component. The inner and outer portions are designed to be assembled together as one unit, simplifying the overall connection process while maintaining fluid separation.
Solution Approach 2:
The fitting is designed as a universal connector that simultaneously performs multiple functions: connecting the inner tube, connecting the outer tube, maintaining fluid separation, and providing thermal protection. This multi-functionality reduces the need for multiple separate components.
Data Source
AI summary
A mid-turbine frame for a gas turbine engine may comprise a bearing system including a bearing housing. A first tube may define a first fluid passage configured to carry a first fluid to the bearing system. An outer sleeve may be disposed around the first tube and may define a chamber between the first tube and the outer sleeve. A first fitting may be coupled to the first tube and to the outer sleeve. The first fitting may comprise an inner portion having an inner surface further defining the first fluid passage. An outer portion may be disposed around the inner portion and may further define the chamber therebetween. The chamber may be configured to contain a fluid. An outer surface may have a first mating surface comprising a frustoconical shape. A flange may extend radially outward from the outer surface.