Preformed Fiber Optic Cable for Fuel Nozzle Combustion Monitoring
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Solution Overview
Problem
Conventional fiber optic cables for gas turbine engines are bulky, expensive, and have a large minimum bend radius, making them difficult to thread through traditional fuel nozzles for effective combustor inspection due to light loss issues with sharp turns.
Innovation Solution
A fiber optic cable with a preformed metal sheath enclosing multiple wave guides and filled with compacted alumina powder, allowing for a reduced bend radius that maintains light transmission and is compatible with fuel nozzle configurations, including a method of forming the cable with a predetermined bend radius to prevent signal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fiber optic cables are used with large minimum bend radius, then light transmission is maintained, but the cable becomes bulky and cannot thread through fuel nozzles effectively
Solution Approach 1:
The patent changes the physical parameters of the fiber optic cable by reducing the minimum bend radius from conventional large values to a compact 0.5 inches. This is achieved through modified cable construction with a flexible metal sheath and optimized wave guide arrangement, allowing the cable to thread through fuel nozzles while maintaining light transmission reliability.
Solution Approach 2:
The patent employs a composite cable structure combining a metal sheath with wave guides and alumina powder filling. This composite design provides both flexibility for tight bends and structural support to maintain light transmission, resolving the contradiction between threadability and optical performance.
2Measurement precision
If conventional fiber optic cables with multiple fibers are used, then imaging capability is achieved, but the cable becomes bulky and expensive
Solution Approach 1:
The patent segments the fiber optic cable into discrete wave guide elements (7 wave guides total) arranged in a specific pattern within the metal sheath. This segmentation allows each wave guide to be optimized independently while maintaining overall cable flexibility and imaging capability, reducing complexity compared to conventional bundled fibers.
Solution Approach 2:
The patent introduces alumina powder as an intermediary filling material between the wave guides. This intermediary substance provides structural support and spacing while allowing the cable to maintain its compact form factor and flexibility, simplifying the overall cable structure while preserving measurement precision.
3Ease of operation
If the fiber optic cable is made flexible to thread through fuel nozzles, then threadability is improved, but light transmission through sharp turns deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-forming the metal sheath with a predetermined bend radius of 0.5 inches during manufacturing. This pre-formed curvature is then heat-set to maintain its shape, allowing the cable to navigate sharp turns in fuel nozzles while preserving light transmission paths through the wave guides.
Solution Approach 2:
The patent uses a flexible metal sheath as a protective and structural shell that can accommodate tight bends. The sheath's flexibility allows the cable to thread through fuel nozzles while the internal wave guide structure maintains optical integrity, resolving the contradiction between flexibility and light transmission.
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 provides a compact, reliable, and cost-effective fiber optic cable with minimal signal strength reduction, enabling effective combustion monitoring without light loss through sharp turns, enhancing the inspection capabilities of gas turbine engines.
Implementation Method 1
A metal sheath may be used to enclose the wave guides
Implementation Method 2
Each wave guide can be spaced apart from the other wave guides such that interstitial sites between each wave guide can be filled with compacted alumina powder
Implementation Method 3
Fiber optic cables also require a large minimum bend radius which is tied to the refraction index and external reflective coating on each glass fiber to prevent loss of light from the wave guide
Implementation Method 4
The fiber optic cable fitted within the feed arm and nozzle assembly has a permanent bend radius preformed in the fiber optic cable. The bend radius can be equal to or greater than the minimum bend radii for the fiber optic cable to serve as a wave guide
Data Source
AI summary
A fuel nozzle for a gas turbine engine includes a feed arm including a fuel passage for issuing a spray of fuel. A nozzle assembly is fixed at an upstream end of the feed arm having a fuel inlet in fluid communication with the fuel passage. A fiber optic cable is configured to collect burner radiation for a pyrometer input and has a first end centered within an optical connector of the nozzle assembly and a second end exposed from the spray outlet. The fiber optic cable fitted within the feed arm and nozzle assembly has a permanent bend radius preformed in the fiber optic cable. The bend radius can be equal to or greater than the minimum bend radii for the fiber optic cable to serve as a wave guide in wavelengths for monitoring combustion.