Lean Direct Fuel Injector for Gas Turbine NOx Reduction
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Solution Overview
Problem
Existing fuel injectors for gas turbine engines face challenges in reducing NOx emissions, particularly when handling multiple fuels, as they can lead to flashback and autoignition due to inadequate fuel-air mixing, and may suffer from efficiency losses from steam injection and limited fuel type compatibility.
Innovation Solution
A dual fuel injector design that includes a central cavity for directing a liquid fuel stream with a surrounding air shell and a separate passage for gaseous fuel, ensuring thorough mixing and minimizing flashback and autoignition risks through controlled air and fuel flow paths, while preventing cross-contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fuel is directly injected into the combustor without thorough mixing, then injection speed is improved, but regions with higher fuel content burn hotter and generate more NOx
Solution Approach 1:
The fuel injection system is segmented into multiple separate outlets: a central outlet for liquid fuel and circumferential outlets for gaseous fuel. This segmentation allows each fuel type to be injected through dedicated pathways, enabling independent optimization of injection parameters for each fuel while maintaining direct injection speed, thereby preventing localized rich combustion zones that generate NOx.
Solution Approach 2:
Different regions of the injector are designed with different fuel delivery characteristics. The central region delivers liquid fuel while the circumferential regions deliver gaseous fuel, creating locally optimized fuel-air mixing zones. This local quality differentiation ensures uniform fuel distribution throughout the combustor, preventing hot spots and reducing NOx formation.
2Object-generated harmful factors
If steam is injected to decrease flame temperature, then NOx production is reduced, but engine efficiency deteriorates
Solution Approach 1:
The harmful effect of high flame temperature is addressed by extracting the temperature control function from thermal management (steam injection) and relocating it to the fuel delivery system. By controlling fuel injection patterns and mixing characteristics, the flame temperature is naturally regulated without adding steam, thus reducing NOx production while maintaining engine efficiency.
3Device complexity
If a single fuel injector design is used, then device complexity is reduced, but fuel type compatibility is limited
Solution Approach 1:
The injector is designed with multi-functionality to handle both liquid and gaseous fuels simultaneously. The structure includes a central outlet for liquid fuel and circumferential outlets for gaseous fuel, all integrated into a single injector body. This universal design allows the same injector to operate with different fuel types and combinations, enhancing versatility without proportionally increasing complexity.
Solution Approach 2:
Multiple fuel delivery functions are merged into a single injector assembly. The liquid fuel outlet and gaseous fuel outlets are combined in one device, with integrated control mechanisms. This merging allows the system to switch between different fuel types and operate in various fuel modes (liquid only, gaseous only, or dual fuel) without requiring separate injectors for each fuel type.
4Temperature
If fuel and air are premixed in the injector, then flame temperature is reduced, but flashback and autoignition risks increase
Solution Approach 1:
The fuel injection system employs dynamic control of fuel delivery timing and distribution. By dynamically adjusting when and where different fuel types are injected, the system optimizes mixing characteristics in real-time. This dynamic approach allows sufficient mixing to reduce flame temperature while controlling the mixing extent and timing to prevent flashback and autoignition, thereby maintaining reliability.
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 dual fuel injector effectively reduces NOx emissions by promoting thorough mixing of fuels with air, minimizing flashback and autoignition, and maintaining engine efficiency by preventing cross-contamination and optimizing fuel delivery.
Implementation Method 1
a first air discharge opening circumferentially disposed about the first fuel discharge outlet and configured to direct a first quantity of air into the central cavity
Implementation Method 2
a second air discharge opening circumferentially disposed about the central cavity and configured to discharge a second quantity of air into the central cavity downstream of the first air discharge outlet
Implementation Method 3
One technique used to reduce the emission of NOx from GTEs is to premix the fuel and air in the fuel injector to provide a lean fuel-air mixture to the combustor
Implementation Method 4
Energy is released when a mixture of compressed air and fuel is burned in the combustor
Data Source
AI summary
A dual fuel injector for a gas turbine engine includes a central cavity extending along a longitudinal axis from a first end to a second end, and a first fuel discharge outlet configured to direct a first fuel into the central cavity at the first end. The fuel injector may also include a first air discharge opening circumferentially disposed about the first fuel discharge outlet and configured to direct a first quantity of air into the central cavity, and a second air discharge opening circumferentially disposed about the central cavity and configured to discharge a second quantity of air into the central cavity downstream of the first air discharge outlet. The fuel injector may further include a second fuel discharge outlet circumferentially disposed about the central cavity and configured to discharge a second fuel therethrough. The second fuel may be different from the first fuel.