Reversible Fastening Device for Gas Turbine Combustion Chamber Tiles
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Solution Overview
Problem
The frequent breaking of screws in gas turbine combustion chambers due to thermal cycles complicates maintenance and repair operations, leading to prolonged downtimes and increased costs, as the broken parts are difficult to remove without invasive and laborious procedures.
Innovation Solution
A reversible fastening device featuring a bayonet-connected bushing and supporting body with a locking seat and external extraction tool interface, allowing for easy replacement of the bushing without drilling or new threading, and designed to withstand thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional threaded fastening devices are used in combustion chambers, then the tiles can be securely fastened to the casing, but the screws become fragile and break frequently due to repeated thermal cycles
Solution Approach 1:
The fastening device is divided into separate components: a supporting body fixed to the casing, a removable bushing with threading, and a screw. This segmentation allows the bushing to remain fixed and protected from thermal damage while only the screw is removed during maintenance, preventing the entire fastening system from being compromised by thermal cycling.
Solution Approach 2:
The bushing acts as an intermediary element between the supporting body and the screw. It provides the threaded interface while being protected within the supporting body structure, shielding the threading from direct thermal exposure and mechanical stress that would otherwise cause the screw to break.
2Temperature
If screws are made of special heat-resistant alloys, then they can withstand high temperatures, but they still become fragile and break over time due to repeated thermal cycles
Solution Approach 1:
The screw is extracted as a separate, removable component that can be easily replaced when broken. The critical threaded interface is moved to the bushing, which remains fixed and protected. This allows the screw to be made of heat-resistant material for temperature tolerance while the overall system reliability is improved through easy replacement capability.
3Object-affected harmful factors
If broken screw parts remain in the casing, then no further damage occurs to the casing, but removal becomes difficult and requires invasive drilling operations
Solution Approach 1:
The bushing is designed with a specific structure that allows preliminary preparation for easy removal. The locking tabs and locking seat geometry are designed so that when the bushing needs to be removed, it can be extracted by applying force to the locking tabs, which rotate the bushing out of the locking seat without requiring drilling or invasive operations on the casing.
4Ease of operation
If maintenance operations are performed in confined spaces, then single operator operation is possible, but the operations become particularly lengthy and laborious when screw breaking occurs
Solution Approach 1:
The fastening device is designed to be self-service friendly for maintenance operations. The bushing can be quickly removed and replaced by a single operator using simple tools, without requiring complex extraction procedures. The modular design allows the operator to simply replace the bushing itself rather than performing invasive repair operations on the casing or threaded holes.
5Ease of repair
If invasive repair operations are performed to remove broken screws, then the broken parts can be extracted, but further damage may occur to the casing even when performed by qualified personnel
Solution Approach 1:
The bushing is designed as a replaceable component that can be easily removed and replaced. Rather than risking damage to the expensive casing during extraction operations, the bushing itself becomes the replaceable element. If the bushing breaks or needs replacement, it can be simply removed from the locking seat and a new one installed without any invasive operations on the casing.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A gas turbine combustion chamber includes a casing (2), a plurality of thermally insulating tiles (7) and at least one reversible fastening device (10), which fixes one of the respective tiles (7) to an inner face (3a, 4a) of the casing (2). The reversible fastening device includes: a supporting body (13), fixed to an outer face (3b, 4b) of the casing (2) and having a locking seat (18) and an opening (21) for access to the locking seat (18) from the inside of the casing (2) through a wall (3, 4) of the casing (2); a threaded bushing (12) insertable inside the locking seat (18) so as to receive a screw (30) through the wall (3, 4) from the inside of the casing (2); and at least one locking member (14), configured to releasably lock the bushing (12; 112; 212) inside the locking seat (18; 118; 218).