Off-Center Cooling Bore Reaming for Gas Turbine Rotors
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Solution Overview
Problem
Gas turbine engines face issues with material creep and cracking due to thermal stresses, which can be exacerbated by reaming cooling bores to increase diameter, leading to reduced efficiency and requiring extensive downtime and transport costs for maintenance.
Innovation Solution
A cooling bore guide system comprising a cutter guide and guide lock allows for off-center reaming of rotor cooling bores without removing the rotor from service, using a semicircular cutter guide and guide lock to create an enlarged portion while maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cooling bores are reamed to increase diameter to address cracking, then rotor reliability is improved, but gas turbine efficiency deteriorates due to excess cooling air passage
Solution Approach 1:
The patent applies local quality by creating an enlarged portion only at specific locations where cracks are detected in the cooling bore, rather than uniformly enlarging the entire bore. This allows targeted crack remediation while preserving the original bore dimensions in other areas, thus maintaining cooling efficiency and avoiding excess cooling air passage.
Solution Approach 2:
The cooling bore is segmented into different zones: the original bore portion and the locally enlarged portion. The enlargement is applied segmentally only where needed (where cracks are present) rather than to the entire bore, allowing selective repair that balances reliability improvement with efficiency preservation.
2Reliability
If standard reaming methods are used to enlarge cooling bores, then cracking issues are addressed, but manufacturing complexity increases due to limited space and requirement for specialized workshops
Solution Approach 1:
The patent transitions from standard axial reaming to off-center reaming by positioning the reaming tool at an offset location. This dimensional change allows the creation of an enlarged portion within the existing bore space without requiring external specialized equipment or rotor removal, simplifying the manufacturing process.
Solution Approach 2:
A guide tool is introduced as an intermediary device that facilitates the off-center reaming operation. The guide tool enables precise positioning of the reaming tool within the constrained space of the cooling bore, making the complex off-center enlargement operation feasible without specialized workshop equipment.
3Reliability
If rotor is removed from service for cooling bore reaming, then crack repair is possible, but loss of time increases due to extensive downtime and transport requirements
Solution Approach 1:
The patent enables self-service repair by providing a complete off-center reaming system that can be applied to the rotor while it remains installed in the gas turbine engine. The guide tool and reaming tool are designed to access and repair cooling bores in-situ, eliminating the need for rotor removal and transport to specialized workshops.
Solution Approach 2:
The guide tool is designed with pre-positioned features that align with existing rotor structures, allowing rapid setup and immediate commencement of the reaming operation. This preliminary preparation enables crack repair to be performed quickly during scheduled maintenance without requiring extensive downtime or complex installation procedures.
Data Source
AI summary
A cooling bore guide for reaming an enlarged portion into a cooling bore of a rotor. The cooling bore guide may include a cutter guide for insertion into the cooling bore and a guide lock for insertion into an adjacent cooling bore.