Combustor Fuel Injection Pegs Offset Concentration Fluctuations
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Solution Overview
Problem
Existing gas turbine combustors face challenges with combustion oscillation, which leads to unstable operation and a high risk of flashback due to high fuel-air ratios and heat-generation fluctuations, making it difficult to maintain low NOx emissions and operational tolerance.
Innovation Solution
A combustor configuration with a combustor external cylinder, a tubular combustor basket, and fuel nozzles that inject fuel for premixing combustion, where compressed air is reversed and introduced into the nozzles, with upstream and downstream fuel injection pegs to offset concentration fluctuations, reducing peak heat-generation fluctuations and preventing combustion oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If main premixing nozzles are arranged to offset heat-generation fluctuations by increasing the distance between them, then combustion oscillation is reduced, but the distance becomes at least 100 mm which increases the risk of flashback in high flammability environment
Solution Approach 1:
The single main premixing nozzle is segmented into two separate nozzles positioned at different locations. Each nozzle contributes to offsetting heat-generation fluctuations through their spatial separation, achieving combustion oscillation suppression while maintaining a compact overall configuration that reduces flashback risk.
Solution Approach 2:
Instead of increasing distance along the axial direction (one dimension), the invention positions nozzles at different angular positions around the combustor perimeter (another dimension). This allows effective offsetting of heat-generation fluctuations while maintaining a compact axial length and reducing flashback risk.
2Object-generated harmful factors
If fuel-air ratio is set higher than inflammability limit for premixing combustion, then low NOx emissions are achieved, but the risk of flashback increases significantly
Solution Approach 1:
The fuel-air mixture composition is made non-uniform by introducing compressed air at different locations. The region near the fuel injection point maintains a leaner mixture to prevent flashback, while other regions maintain the richer mixture needed for low NOx emissions. This spatial variation in mixture quality resolves the contradiction between flashback prevention and NOx reduction.
Solution Approach 2:
Compressed air is introduced as an intermediary substance between the fuel injection point and the combustion zone. This intermediate air injection creates a progressive mixing pattern that prevents flashback by maintaining lean conditions near the fuel source while allowing rich conditions further downstream for low NOx combustion.
3Reliability
If compressed air flow rate is maintained at high level for premixing combustion, then combustion stability is improved, but the interval between fuel injection points must be considerably great to prevent combustion oscillation
Solution Approach 1:
The invention positions fuel injection points at different angular positions around the combustor perimeter rather than spacing them far apart axially. This dimensional change allows the use of high compressed air flow rates for combustion stability while maintaining a compact axial length, as the offsetting of heat-generation fluctuations is achieved through circumferential separation rather than axial distance.
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 configuration effectively suppresses combustion oscillation by offsetting heat-generation fluctuations, increasing operational tolerance and reducing the risk of flashback, while maintaining low NOx emissions and stable combustion.
Implementation Method 1
Concentration fluctuation of the upstream side fuel caused by pressure fluctuation in the combustor is configured so as to reduce a peak of concentration fluctuation of the downstream side fuel at a combustion start position of the combustor
Implementation Method 2
a uniform fuel-air ratio is accomplished, and thus the amount of production of NOx can be reduced by low-temperature combustion
Implementation Method 3
a pilot nozzle that is disposed in the center of the combustor basket, and injects the fuel into the combustor basket to form a diffusion flame
Implementation Method 4
ignite the pre-mixture to form a premixed flame by the diffusion flame
Implementation Method 5
Compressed air flowing along the compressed air channel is approximately reversed in the flow direction at an end of the combustor basket, and is introduced into the plurality of fuel nozzles
Implementation Method 6
pressure fluctuation generated in the combustor by combustion and heat-generation fluctuation generated by temporal variation in fuel concentration
Implementation Method 7
The combustion oscillation is a phenomenon in which pressure fluctuation generated in the combustor by combustion and heat-generation fluctuation generated by temporal variation in fuel concentration caused by a nozzle part are synchronized at a combustion position, thereby oscillating
Data Source
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AI summary
This burner comprises a burner outer cylinder, a cylindrical burner inner cylinder provided inside the burner outer cylinder, a compressed air flow channel demarcated between the burner outer cylinder and the burner inner cylinder, and a plurality of fuel nozzles provided inside the burner inner cylinder, the compressed air flowing through the compressed air flow channel being substantially reversed in flow direction in the end of the burner inner cylinder and led into the plurality of fuel nozzles. The compressed air flow channel is provided with a fuel injection peg comprising an upstream fuel injection peg for injecting up-stream fuel and a downstream fuel injection peg for injecting downstream fuel, and is configured so that upstream fuel concentration fluctuations caused by pressure fluctuations in the burner reduce the peak of downstream fuel concentration fluctuations in the burning initiation position of the burner.