Fuel Nozzle Cooling Circuit for Gas Turbine Coking Prevention
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Solution Overview
Problem
Conventional fuel nozzles in gas turbine engines face issues with coking due to lack of fuel flow and high combustion temperatures, particularly affecting parts close to the flame, leading to reduced efficiency and nozzle degradation.
Innovation Solution
The design incorporates a nozzle body with a fuel circuit and a cooling circuit, featuring radial swirl vanes, helical threads, and coolant channels to enhance cooling, even when fuel is not flowing, using materials like metallic and ceramic components to manage thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fuel flow is stopped in certain nozzles during fuel staging, then fuel distribution is optimized, but coking occurs due to high combustion temperatures
Solution Approach 1:
The nozzle is divided into functional segments: a fuel circuit for fuel delivery and a separate cooling circuit for thermal management. This segmentation allows independent operation of fuel flow and cooling functions, enabling fuel staging while preventing coking through continuous cooling even when fuel flow is stopped.
Solution Approach 2:
The cooling circuit is activated before fuel flow begins and continues after fuel flow stops. This preliminary and extended cooling action prevents coking from occurring in the first place, addressing the reliability issue before it manifests during fuel staging operations.
2Temperature
If conventional cooling methods are used, then some thermal protection is provided, but cooling capability is insufficient during high-temperature combustion
Solution Approach 1:
The cooling circuit is nested within the nozzle structure, with cooling channels formed within the nozzle body walls. This nested configuration allows the cooling circuit to be integrated into the fuel nozzle while providing enhanced cooling capability directly at the high-temperature zones, improving reliability without adding external components.
3Strength
If fuel circuit walls are made thick to withstand thermal stress, then structural strength is improved, but fluid flow passages become restricted
Solution Approach 1:
The nozzle structure employs varying wall thicknesses optimized for local requirements: thicker walls in high-stress regions for thermal stress resistance, and thinner walls where fuel flow passages need to be maximized. This local quality differentiation allows simultaneous achievement of structural strength and fluid flow capacity.
Solution Approach 2:
The cooling circuit is positioned in a dimension separate from the fuel flow path, with cooling channels formed in the nozzle walls perpendicular to or adjacent to the fuel passages. This dimensional separation allows independent optimization of wall thickness for cooling purposes without restricting fuel flow capacity in the fuel circuit.
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
This design provides increased cooling capability and improved durability by maintaining nozzle performance and preventing coking, even when the fuel distributor is not in use, through effective heat management and fluid distribution.
Implementation Method 1
A cooling circuit is defined within at least one of the fuel circuit inner wall or the fuel circuit outer wall. The cooling circuit extends from an axial position proximate the fuel circuit inlet to an axial position proximate the fuel circuit outlet.
Implementation Method 2
The air passage includes an annular inlet having radial swirl vanes circumferentially spaced apart from one another. The radial swirler can include radial swirl vanes circumferentially spaced apart from one another about the annular inlet to induce swirl into air entering the annular inlet of the air passage.
Implementation Method 3
The cooling circuit can include a pair of helical threads. A first one of the helical threads can begin at the distribution channel and extend to an axial position proximate the fuel circuit outlet to provide cooling flow to the nozzle tip.
Implementation Method 4
At least a portion of the fuel circuit outer wall is radially outboard from the fuel circuit inner wall with respect to the longitudinal axis. A cooling circuit is defined within at least one of the fuel circuit inner wall or the fuel circuit outer wall.
Data Source
AI summary
A nozzle includes a nozzle body defining a longitudinal axis. The nozzle body has an air passage, a fuel circuit radially outboard from the air passage with respect to the longitudinal axis, and a cooling circuit. The fuel circuit extends from a fuel circuit inlet to a fuel circuit annular outlet. The fuel circuit is defined between a fuel circuit inner wall and a fuel circuit outer wall. At least a portion of the fuel circuit outer wall is radially outboard from the fuel circuit inner wall with respect to the longitudinal axis. A cooling circuit is defined within at least one of the fuel circuit inner wall or the fuel circuit outer wall. The cooling circuit extends from an axial position proximate the fuel circuit inlet to an axial position proximate the fuel circuit outlet.