Axially Staged Fuel Nozzle for Gas Turbine Combustion
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Solution Overview
Problem
Current gas turbine combustor designs face challenges in achieving a homogeneous fuel-air mixture with efficient premixing and pre-vaporization, leading to high NOx emissions and inadequate control over fuel-air ratio profiles.
Innovation Solution
A fuel nozzle assembly with radially extending vanes and an annular ring, featuring apertures staggered at different axial planes, directs fuel flow primarily axially to achieve a broad spectrum of gas residence time and controlled fuel-air ratio, utilizing a core with a coaxial annular passageway and perforations to optimize mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fuel is injected radially outward through vanes in conventional designs, then fuel distribution is simplified, but premixing efficiency and pre-vaporization are insufficient leading to high NOx emissions
Solution Approach 1:
The fuel injection system is segmented into multiple axial injection zones along the vanes, with fuel injected at different axial positions to create staged injection. This segmentation allows different regions to perform different functions (premixing in upstream regions, combustion in downstream regions), improving premixing efficiency and reducing NOx emissions while maintaining structural simplicity
Solution Approach 2:
The invention transitions from radial fuel injection to axial fuel injection through the vanes. This dimensional change in injection direction enables fuel to be injected along the axial flow path, creating extended residence time and improved mixing with the airflow, thereby enhancing premixing and reducing NOx emissions
2Speed
If fuel injection duration is shortened to improve response time, then dynamic response is improved, but premixing and pre-vaporization time is insufficient
Solution Approach 1:
Fuel is injected upstream through the vanes before reaching the combustion zone, allowing premixing and pre-vaporization to occur in advance during the axial flow path. This preliminary action ensures that by the time fuel reaches the combustion zone, adequate mixing has occurred, maintaining both fast response and sufficient premixing time
Solution Approach 2:
The axial injection through multiple vane positions creates continuous fuel introduction along the flow path, ensuring uninterrupted premixing action. This continuous injection maintains steady premixing efficiency while allowing rapid response to load changes, as the distributed injection points ensure continuous fuel supply throughout the combustion zone
3Power
If fuel-air ratio is increased to improve combustion efficiency, then energy output is improved, but control precision over fuel-air ratio profile deteriorates
Solution Approach 1:
Different regions of the vane structure have different aperture characteristics and injection patterns, creating local variations in fuel-air ratio. Upstream regions provide leaner mixtures for premixing, while downstream regions provide richer mixtures for combustion, allowing precise local control of fuel-air ratio profile to optimize both combustion efficiency and control precision
Solution Approach 2:
The system controls fuel-air ratio by changing injection parameters including aperture size, injection pressure, and axial injection positions. By varying these parameters across different vane locations, the system achieves precise control over the fuel-air ratio profile, enabling optimized combustion efficiency with maintained control precision
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 enhances premixing and pre-vaporization, reducing NOx emissions and providing precise control over the fuel-air ratio, thereby improving combustion efficiency and stability.
Implementation Method 1
Fuel is injected from the fuel nozzle assembly to flow primarily in an axial direction relative to oncoming air flow through the vanes
Implementation Method 2
obtain a broad spectrum of gas residence time between the point of fuel injection and the flame front
Implementation Method 3
Premixing fuel and air together before combustion allows for the fuel and air to form a more homogeneous mixture prior to ignition
Implementation Method 4
The residence time of fuel concentration wave in the premixer should be suitably long for providing premixing and pre-vaporization for obtaining low NOx combustion
Data Source
AI summary
The present invention discloses a fuel nozzle assembly and method for axially staging fuel injection. The fuel nozzle assembly comprises a plurality of vanes connected to a core, with an annular ring connectedly surrounding the plurality of vanes. Fuel is directed through the core and then through the vanes and is injected at different axial planes generally perpendicular to an oncoming air stream to obtain a broad spectrum of gas residence time between the point of fuel injection and the flame.