Variable Vane Outer Trunnion Shaft Repair Using Pilot-Aligned Welding
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Solution Overview
Problem
Existing methods for repairing variable vanes in gas turbine engines, particularly the outer trunnion shaft's groove and threaded holes, are difficult and often result in the vane being discarded due to the complexity of alignment and repair.
Innovation Solution
A method involving the preparation of a repair detail with a pilot portion and a nominal outer diameter, which is welded to a shaft stub, and includes forming a new threaded hole and groove, allowing for precise alignment and repair of the outer trunnion shaft, using electron beam welding for secure bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the outer trunnion shaft is repaired using conventional welding methods, then the repair process becomes complex and time-consuming, but the vane can be restored to service
Solution Approach 1:
The method performs preliminary actions by first removing the damaged outer trunnion shaft and preparing the shaft stub with a precisely fitted pilot portion before welding. The repair detail is pre-prepared with the pilot portion that matches the remaining bore portion, ensuring proper alignment is established before the actual welding repair occurs. This preliminary preparation simplifies the subsequent welding process and reduces overall repair time.
2Ease of repair
If the outer trunnion shaft is repaired by welding a repair detail, then the vane can be restored, but alignment precision is difficult to achieve
Solution Approach 1:
The pilot portion serves as an intermediary element between the shaft stub and the repair detail. It is inserted into the remaining bore portion of the shaft stub to establish precise alignment before the repair detail is welded into place. This intermediary component ensures that the repair detail is accurately positioned relative to the shaft stub, achieving the required alignment precision that would be difficult to obtain through welding alone.
3Device complexity
If the variable vane is discarded due to damage, then no repair complexity is involved, but the vane cannot be reused and replacement is required
Solution Approach 1:
Instead of discarding the damaged variable vane, the method recovers it by removing only the damaged outer trunnion shaft and replacing it with a repair detail. The airfoil and inner trunnion shaft are preserved and reused. This approach transforms a complete discard scenario into a selective replacement scenario, maintaining vane availability while managing repair complexity through targeted replacement of only the damaged component.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables effective repair of damaged variable vanes by allowing precise alignment and secure bonding, extending the lifespan of the vane and preventing unnecessary discarding, thus improving the maintenance efficiency of gas turbine engines.
Implementation Method 1
The repair detail is welded to the shaft stub. The welding is electron beam welding.
Data Source
Figure 1
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Figure 3A~3E
AI summary
A variable vane having an airfoil, an inner trunnion shaft and an outer trunnion shaft, with the outer trunnion shaft having a threaded hole and a groove extending around a circumference of the outer trunnion shaft is repaired by removing a portion of the outer trunnion shaft leaving a shaft stub. A repair detail is prepared having an outer peripheral shaft portion with a nominal outer diameter. The repair detail further has a pilot portion extending forwardly and having a smaller outer diameter than an outer diameter of the nominal outer diameter. The shaft stub has a remaining bore portion, which is a portion of the threaded hole. The pilot portion is sized to be received within the remaining bore portion. The pilot is inserted into the remaining bore portion. The repair detail is welded to the shaft stub. A repaired variable vane is also disclosed.