Annular Combustor Dilution Hole Layout for Lower NOx Emissions
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Solution Overview
Problem
Gas turbine engines emit environmentally harmful toxins such as nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds due to high combustor flame temperatures, necessitating a solution to reduce NOx emissions while maintaining efficiency.
Innovation Solution
The use of a combustor with dilution openings in the dome wall to regulate flame temperatures and mixtures within the combustor, incorporating swirlers and vanes to control airflow and fuel mixture, thereby reducing NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional combustion chambers with direct fuel injection are used, then combustion efficiency can be achieved, but sooting and incomplete combustion occur due to insufficient air mixing
Solution Approach 1:
The combustion chamber is segmented into multiple zones with different air dilution levels. Primary dilution holes provide initial air mixing near the fuel injector, while secondary dilution holes provide additional air mixing in the combustion chamber. This segmentation allows staged combustion that prevents sooting while maintaining combustion efficiency.
Solution Approach 2:
Air acts as an intermediary substance that is introduced through dilution holes to mix with the fuel-air mixture. This intermediary air flow facilitates complete combustion by providing oxygen without directly contacting the fuel source, thereby preventing sooting while maintaining efficient combustion.
2Power
If high power output is required, then fuel injection rate must be increased, but this exacerbates sooting and incomplete combustion
Solution Approach 1:
Air is introduced through primary dilution holes before the main combustion event, pre-mixing the air and fuel. This preliminary air mixing ensures that when high fuel injection rates are used, the combustion process has already prepared the necessary air-fuel mixture, enabling high power output without excessive sooting.
Solution Approach 2:
The system changes the air-to-fuel ratio parameter by introducing variable amounts of air through different dilution holes. By adjusting the air dilution parameter, the system can operate at high power output while maintaining optimal combustion conditions that prevent sooting.
3Reliability
If multiple dilution holes are used to improve air mixing, then combustion quality improves, but device complexity increases
Solution Approach 1:
Multiple dilution holes are merged into a unified structural arrangement where primary and secondary dilution holes are integrated into the combustion chamber walls. This merging approach provides multiple air mixing stages while maintaining a relatively simple overall structure that can be manufactured as a single component.
4Reliability
If air dilution is increased to prevent sooting, then combustion completeness improves, but available combustion space is reduced
Solution Approach 1:
Air dilution is applied locally at specific positions where it is most needed - through primary dilution holes near the fuel injector and secondary dilution holes in the combustion chamber. This localized approach provides necessary air mixing without requiring uniform air dilution throughout the entire combustion space, thereby preserving adequate combustion volume.
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 effectively decreases NOx emissions by controlling flame temperatures and improving combustion efficiency, aligning with environmental regulations and maintaining operational performance.
Implementation Method 1
first and second, concentrically arranged and radially spaced, annular dilution holes formed in the annular dome wall to define an annular space between the first and second annular dilution holes
Implementation Method 2
multiple fuel injectors circumferentially spaced about the annular space between the first and second annular dilution holes
Data Source
Figure 1
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Figure 3
AI summary
A gas turbine engine (10) including a compressor section (12) and a combustion section (14) in serial flow arrangement along an engine centerline (21), the combustion section having an annular dome wall circumscribing the engine centerline; an annular combustor liner extending from the annular dome wall to define an annular combustion chamber in combination with the annular dome wall; first and second, concentrically arranged and radially spaced, annular dilution holes formed in the annular dome wall to define an annular space between the first and second annular dilution holes; and multiple fuel injectors circumferentially spaced about the annular space between the first and second annular dilution holes.