Oxy-fuel Pilot Burner Combustion Stability and NOx Reduction
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Solution Overview
Problem
Existing gas turbine combustors face challenges with combustion stability and NOx emissions due to the cost-effectiveness and increased NOx production from bulk oxygen enrichment of combustion air, and they typically operate at fuel-lean conditions with excess oxygen in the oxidizer stream.
Innovation Solution
The implementation of an oxy-fuel pilot burner with a central fuel nozzle and an annular oxygen nozzle, where the oxygen concentration is controlled to be less than or equal to 0.5%, and the fuel is introduced at a rate less than 10% of the total fuel, to enhance combustion stability and reduce NOx emissions by leveraging the strong combustion stability of oxy-fuel flames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulk oxygen enrichment of combustion air is used to improve combustion stability, then combustion stability is improved, but cost increases and NOx emissions increase
Solution Approach 1:
The invention divides the combustion system into two separate burners: a pilot burner that operates with oxygen-enriched air (up to 30% oxygen concentration) to provide stable ignition and flame holding, and a main burner that operates with normal air to perform the bulk combustion. This segmentation allows the small pilot zone to provide stability while the large main zone maintains low NOx emissions by using ambient air.
Solution Approach 2:
The invention applies oxygen enrichment locally only in the pilot burner region where it is most needed for flame stability, rather than enriching the entire combustion air stream. The pilot burner receives concentrated oxygen (up to 30%) while the main burner receives normal air, creating a localized high-stability zone that doesn't compromise overall emission performance.
2Reliability
If bulk oxygen enrichment of combustion air is used to improve combustion stability, then combustion stability is improved, but operating cost increases
Solution Approach 1:
The combustion system is segmented into a small pilot burner and a large main burner, with oxygen enrichment applied only to the pilot portion. This allows the system to achieve combustion stability with minimal oxygen consumption (only for the pilot flame) rather than enriching the entire combustion air supply.
Solution Approach 2:
The invention uses partial oxygen enrichment (up to 30% in the pilot burner) rather than full enrichment of the entire combustion system. This partial action in the critical pilot zone provides sufficient stability while dramatically reducing oxygen consumption and associated costs compared to bulk enrichment.
3Object-generated harmful factors
If fuel-lean conditions are used to reduce emissions, then NOx emissions are reduced, but combustion stability deteriorates
Solution Approach 1:
The burner system is segmented into a pilot burner operating with oxygen-enriched air that can maintain stable combustion at fuel-lean conditions, and a main burner operating with normal air. The oxygen-enriched pilot flame provides the stability needed to sustain fuel-lean operation in the main burner, thereby enabling low NOx emissions without sacrificing stability.
Solution Approach 2:
The invention changes the oxygen concentration parameter in the pilot burner (up to 30% oxygen) to enable stable combustion at fuel-lean equivalence ratios. This parameter change in the pilot zone allows the main burner to operate at lower equivalence ratios for reduced NOx emissions while the enriched pilot maintains overall stability.
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 approach expands the operating envelope, reduces NOx emissions, and increases thermodynamic efficiency by achieving stable combustion with a lower oxygen enrichment level, allowing for a broader range of stable combustion conditions and lower risk of flame instability, while also enabling lower turbine inlet temperatures and reduced NOx emissions.
Implementation Method 1
combusting the first fuel using the first oxygen source to produce combustion products within the combustor
Data Source
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AI summary
A combustor for a gas turbine engine having a compressor upstream of the combustor and a turbine downstream of the combustor. The combustor also includes a combustor chamber, an oxy-fuel pilot burner (104) centrally positioned at an end of the combustor chamber, and an air-fuel premix burner configured to at least partially premix air and fuel. The air-fuel premix burner surrounds the oxy-fuel pilot burner (104) in an annular configuration.