Annular Gas Turbine Combustor with RQL Zones
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Solution Overview
Problem
Gas turbine engines face challenges in minimizing NOx emissions due to the formation of oxides of nitrogen during combustion, which are not adequately addressed by existing combustor designs, particularly in maintaining low NOx emissions while ensuring combustion performance and efficiency.
Innovation Solution
The design of an annular combustor with specific volume distributions and liner angles, combined with a rich burn, quick quench, lean burn (RQL) combustion strategy, where the forward section is fuel-rich, the intermediate section transitions, and the aft section is fuel-lean, with strategically placed fuel injectors and combustion air admission holes to manage combustion conditions and reduce NOx formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional combustor designs are used, then combustion performance is maintained, but NOx emissions are not adequately minimized
Solution Approach 1:
The combustor is divided into three distinct zones: a forward fuel-rich combustion zone, an intermediate quench zone with rapid cooling, and an aft fuel-lean combustion zone. This segmentation allows each zone to perform its specific function - the forward zone burns fuel with limited air to avoid high temperatures, the intermediate zone rapidly cools the gases to freeze NOx formation, and the aft zone completes combustion with remaining fuel. This spatial segmentation resolves the contradiction by enabling low-NOx combustion while maintaining overall combustion efficiency.
Solution Approach 2:
Different regions of the combustor are given different local qualities - the forward zone has fuel-rich conditions with limited air supply, the intermediate zone has high cooling air injection for rapid quenching, and the aft zone has fuel-lean conditions. This local differentiation allows each region to optimize for its specific purpose, with the forward and aft zones handling combustion at different stoichiometric ratios and the intermediate zone handling rapid cooling, thereby achieving both low NOx emissions and high combustion efficiency.
2Volume of stationary object
If combustor volume is reduced, then engine size is minimized, but combustion stability may be compromised
Solution Approach 1:
The combustor volume is segmented into three functional zones with specific volume ratios - the forward fuel-rich zone occupies approximately 35% of the volume, the intermediate quench zone occupies about 20%, and the aft fuel-lean zone occupies about 45%. This segmentation allows the combustor to maintain adequate residence time for stable combustion in each zone while keeping the overall volume compact. The forward zone provides stable ignition and initial combustion, the intermediate zone provides rapid cooling, and the aft zone completes combustion, all within a reduced overall volume.
3Object-generated harmful factors
If fuel-rich combustion is used to reduce NOx, then NOx formation is minimized, but combustion completeness may be reduced
Solution Approach 1:
The combustion process is segmented into two stages: a forward fuel-rich combustion zone where fuel burns with limited air to maintain low temperatures and minimize NOx formation, followed by an aft fuel-lean combustion zone where remaining fuel burns with additional air to ensure complete combustion. This two-stage segmented approach resolves the contradiction by achieving both low NOx formation in the first stage and complete combustion in the second stage.
Solution Approach 2:
The combustion process continues continuously from the forward fuel-rich zone through the intermediate quench zone to the aft fuel-lean zone. The unburned and partially burned gases from the forward zone are transported through the intermediate zone and into the aft zone where combustion is completed. This continuous combustion action ensures that all fuel is ultimately burned completely while the initial fuel-rich conditions in the forward zone minimize NOx formation.
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 configuration achieves low NOx emissions by optimizing combustion residence time and mixing, ensuring stable flame and reduced NOx production without compromising engine performance, and allows for a reduction in overall combustor volume while maintaining operability.
Implementation Method 1
The swirlers impart a swirl to inlet air entering the forward end of the combustion chamber at the bulkhead to provide rapid mixing of the fuel and inlet air
Implementation Method 2
Combustion of the hydrocarbon fuel in air inevitably produces oxides of nitrogen (NOx). NOx emissions are the subject of increasingly stringent controls by regulatory authorities. One combustion strategy for minimizing NOx emissions from gas turbine engines is referred to as rich burn, quick quench, lean burn (RQL) combustion.
Data Source
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AI summary
An annular combustor (100) for a gas turbine has a combustion chamber having an interior volume that, in longitudinal section, includes a forward volume (V1), an intermediate volume (V2) and an aft volume (V3). The forward volume (V1) represents from about 30% to about 40% of the combustor interior volume, the intermediate volume (V2) represents from about 10% to about 20% of the combustor interior volume, and the aft volume (V3) represents from about 40% to about 60% of the combustor interior volume.