Premixed Direct Injection Disk for Gas Turbine Combustion
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Solution Overview
Problem
Conventional gas turbines burning hydrocarbon fuels face challenges with high NOx emissions, flame holding, and flashback issues due to the high reactivity of fuels like hydrogen and syngas, which complicates the design of premixed direct injection combustion systems, especially in terms of maintaining efficient combustion and preventing damage to nozzle components.
Innovation Solution
A premixed direct injection disk design featuring pie-shaped sectors with fuel/air mixing tubes that include fuel injection holes at specific angles and recession distances, optimized for efficient mixing and low NOx emissions, replacing traditional fuel nozzles and cap assemblies in can-style combustors to enhance fuel-air mixing and reduce the risk of flashback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If lean premixing of fuel and air is used to control reaction zone temperature below thermal NOx formation level, then NOx emissions are reduced, but flame holding and flashback risks increase in the premixing section
Solution Approach 1:
The combustor is divided into distinct functional zones: a premixing section with multiple premixing holes for fuel-air mixing, a flame holding section with recirculation zones, and a combustion section. This segmentation allows lean premixing for low NOx while providing dedicated flame holding zones that prevent flashback into the premixing section.
Solution Approach 2:
A flame holding section acts as an intermediary between the premixing section and the combustion section. This intermediate zone with recirculation zones stabilizes the flame and prevents it from propagating back into the premixing holes, enabling safe operation with lean premixed gases.
2Productivity
If high hydrogen fuel is used to achieve clean combustion, then combustion efficiency is improved, but flashback risk into the nozzle increases due to high flame speed and wide flammability range
Solution Approach 1:
The system segments the combustion process into premixing, flame holding, and combustion zones. The flame holding section with recirculation zones serves as a buffer that accommodates high flame speed hydrogen combustion while preventing flashback to the premixing holes.
Solution Approach 2:
The high flame speed and wide flammability range of hydrogen, which cause flashback risks, are converted into benefits through the flame holding section. The recirculation zones in this section stabilize the high-speed hydrogen flame and actually protect the premixing holes from flashback.
3Ease of operation
If conventional fuel nozzles and cap assemblies are used in can-style combustors, then traditional combustion function is achieved, but flash back into the nozzle causes extensive damage to the nozzle in a very short period of time
Solution Approach 1:
The vulnerable nozzle components (fuel nozzles and cap assemblies) are extracted from the premixing section and replaced with a more robust premixing disk design. The premixing holes are directly formed in the disk, eliminating the traditional nozzle-cap assembly that is susceptible to flashback damage.
Solution Approach 2:
The flame holding section with recirculation zones is positioned beforehand between the premixing disk and the combustion zone to cushion and absorb the high-energy hydrogen flame, preventing it from reaching and damaging the premixing holes in the disk.
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 design achieves efficient fuel-air mixing with low NOx emissions and reduced risk of flame flashback, improving gas turbine efficiency and preventing nozzle damage, while maintaining a durable and easy-to-construct configuration.
Implementation Method 1
each mixing tube including an outer tube wall extending axially along a tube axis between an inlet end and an exit end and in fluid communication with the at least one fuel plenum, at least a portion of the plurality of fuel/air mixing tubes further including at least one fuel injection hole having a fuel injection hole diameter extending through said outer tube wall, said at least one fuel injection hole having an injection angle relative to said tube axis
Implementation Method 2
a recession distance extending between said fuel injection hole and said exit end along said tube axis, said recession distance being about 5 to 100 times greater than said fuel injection hole diameter
Implementation Method 3
The present invention is a premixed direct injection disk design that provides good fuel air mixing with low combustion generated NOx
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A fuel/air mixing disk for use in a fuel/air mixing combustor assembly is provided. The disk includes a first face, a second face, and at least one fuel plenum disposed therebetween. A plurality of fuel/air mixing tubes extend through the pre-mixing disk, each mixing tube including an outer tube wall extending axially along a tube axis and in fluid communication with the at least one fuel plenum. At least a portion of the plurality of fuel/air mixing tubes further includes at least one fuel injection hole have a fuel injection hole diameter extending through said outer tube wall, the fuel injection hole having an injection angle relative to the tube axis. The invention provides good fuel air mixing with low combustion generated NOx and low flow pressure loss translating to a high gas turbine efficiency, that is durable, and resistant to flame holding and flash back.