Fuel Injector Joint With Rotatable Adaptor for Thermal Expansion
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Solution Overview
Problem
Gas turbine fuel injectors face challenges due to significant temperature variations, leading to thermal expansion and stress on components, which can cause fatigue and damage, particularly due to the temperature difference between cold fuel tubes and hot housings, making existing weld joints difficult to inspect, replace, and heat treat without damaging internal seals.
Innovation Solution
A fuel injector assembly with a rotatable adaptor that provides concentric alignment with the fuel tube's thermal expansion axis, using dynamic and metal-to-metal seals to manage thermal expansion and prevent leakage, allowing for field inspection and repair, and incorporating a weight-type distributor for balanced fuel flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a weld joint is used to join housing pieces, then structural integrity and fluid tightness are improved, but ease of repair and inspection deteriorate
Solution Approach 1:
The housing is divided into multiple separable pieces joined by mechanical fasteners (screws, clips, or bayonet connectors) rather than permanent welds. This segmentation allows the housing to be disassembled for inspection and repair of internal components while maintaining structural integrity during operation.
Solution Approach 2:
A removable end cap or access plate is introduced as an intermediary component that seals the housing during operation but can be easily removed for maintenance. This mediator provides fluid tightness when installed while enabling easy access to internal components when removed.
2Stability of the object's composition
If the connector is angled to align with expansion axis, then accommodation of thermal expansion is improved, but rotational freedom deteriorates
Solution Approach 1:
The connector incorporates dynamic sealing elements (such as spring-loaded seals or elastomeric seals) that maintain sealing effectiveness while accommodating thermal expansion movements. The sealing mechanism adapts its position or pressure in response to expansion forces, maintaining both alignment and rotational capability.
Solution Approach 2:
The connector design allows for controlled movement along its expansion axis through features such as sliding joints or compliant sections. These parameter changes in position are permitted while the angled orientation relative to the housing axis is maintained, preserving both thermal expansion accommodation and rotational freedom for assembly.
3Stability of the object's composition
If dynamic seals are used to allow relative movement, then accommodation of thermal expansion is improved, but risk of fuel leakage increases
Solution Approach 1:
The dynamic seal design incorporates pre-compression or pre-positioning features that ensure the sealing elements are properly engaged before thermal expansion occurs. This beforehand cushioning ensures that even during relative movement from thermal expansion, the seals remain in contact and prevent fuel leakage throughout the operational temperature range.
Solution Approach 2:
The dynamic sealing system uses composite sealing elements combining different materials (such as elastomers with reinforcement, or multi-layer composite seals) that provide both flexibility for movement and sufficient sealing pressure to prevent leakage. The composite structure allows the seal to deform with thermal expansion while maintaining leak-tight performance.
4Strength
If weld joint is made permanent, then structural strength is improved, but complexity of inspection and replacement deteriorates
Solution Approach 1:
The housing connection is segmented into discrete, replaceable components joined by mechanical fasteners rather than permanent welds. This allows individual components to be inspected, removed, and replaced independently, reducing the overall complexity of maintenance while maintaining joint strength through proper fastening mechanisms.
Solution Approach 2:
The design allows for relatively simple, low-cost fastening components (screws, clips, or connectors) that can be easily replaced if worn or damaged, rather than requiring complex welding repairs. This approach treats the fastening elements as replaceable components, simplifying inspection and replacement procedures.
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
The solution reduces stress buildup, enables field repair and inspection, and provides a secure, leak-resistant joint with reduced vibration, allowing for easier assembly and disassembly, and accommodating manufacturing tolerances through integral components.
Implementation Method 1
Thermal expansion of the tubes and the injector housing create stresses within the components that can cause fatigue and damage to the tube or housing
Implementation Method 2
second sealing means are provided between the outside of the adaptor and the housing
Implementation Method 3
incorporating a weight-type distributor for balanced fuel flow
Data Source
Figure 1
Figure 2
AI summary
A joint for a gas turbine fuel injector, the joint comprises a housing for supporting a fuel injector, a first tube terminating within the housing and a second tube. The housing at least partially encloses an adaptor having a bore, with one end of the first tube and one end of the second tube being located within opposing ends of the bore. First sealing means are provided between the outside of the first tube and the adaptor bore, second sealing means are provided between the outside of the second tube and the adaptor bore and third sealing means are provided between the outside of the adaptor and the housing. The joint is particularly suitable for conduits carrying a relatively cold fluid mounted in a relatively hot housing.