Axial Compressor Rotor Repair Using Segmented Shaft Replacement
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Solution Overview
Problem
The existing methods for repairing a gas turbine's multi-stage axial compressor rotor are burdensome, requiring the complete removal and replacement of the shaft to replace damaged bladed discs, which is time-consuming and costly, and necessitates the use of expensive, high-temperature-resistant materials like stainless steel.
Innovation Solution
A method involving cutting the rotor shaft to separate the damaged disc section, using new discs with solid hubs and a new solid shaft section, and securing them with anchor bolts, allowing for easier replacement and reducing the need for high-temperature materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the last bladed discs are replaced by heating to increase internal diameter and reduce interference, then the discs can be removed from the shaft, but the heat required would irreparably damage both the discs and the shaft
Solution Approach 1:
The shaft is divided into two separate parts: the remaining shaft portion that retains usable discs and a new end shaft portion that will accommodate the replacement discs. This segmentation allows the replacement operation to be localized without affecting the integrity of the main shaft and usable discs.
Solution Approach 2:
The problematic interference fit connection is extracted and replaced by an alternative connection method. Instead of relying on thermal expansion for removal, the discs are secured using anchor bolts that pass through the new end shaft portion and into the remaining shaft, eliminating the need for high-temperature heating that would cause damage.
2Ease of repair
If material is removed from the shaft to allow disc removal, then the discs can be replaced, but the shaft becomes unusable and must be completely rebuilt
Solution Approach 1:
The shaft is segmented into a reusable remaining portion and a replaceable new end portion. This allows the majority of the shaft with intact discs to be preserved and reused, while only the end portion needing disc accommodation is manufactured anew and attached.
Solution Approach 2:
Instead of discarding the entire shaft when disc replacement is needed, the method recovers and reuses the remaining shaft portion that still has functional discs. Only the minimal necessary end portion is discarded and replaced, significantly reducing material waste and repair complexity.
3Reliability
If stainless steel discs are used to resist high temperatures and maintain interference fit, then the discs can withstand operating conditions, but the cost increases and hydrogen embrittlement occurs
Solution Approach 1:
The thermal interference fit mechanism is replaced with a mechanical fastening system using anchor bolts. This substitution eliminates the need for discs to maintain interference through thermal expansion, allowing the use of cheaper micro-alloyed steel that is not subject to hydrogen embrittlement while still providing secure attachment through the bolt mechanism.
Data Source
AI summary
The method comprises the steps of: a) cutting the shaft of the rotor at a section plane perpendicular to the axis of rotation of the shaft so as to separate the end portion of the shaft on which the bladed discs to be replaced are mounted from the remaining portion of the shaft; b) providing, for each bladed disc to be replaced, a corresponding new bladed disc with a respective hub having a solid cross-section; c) providing a new end portion of the shaft with a solid cross-section; and d) clamping the new bladed discs between the remaining portion of the shaft and the new end portion of the shaft, securing them to the remaining portion of the shaft by anchor bolts.