Combustor End Cap Purge Ports for Flashback Prevention
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Solution Overview
Problem
In combustor designs, fuel can leak and become trapped in the end cap, leading to conditions conducive to flashback and flame holding events due to insufficient working fluid velocity for purging, which poses a risk to the fuel nozzles and overall combustor operation.
Innovation Solution
The combustor design includes an end cap with radially extending plates and tubes that have purge ports axially aligned with the plates, allowing a working fluid to flow through diluent plenums and purge ports to effectively remove trapped fuel from low velocity areas, reducing the risk of flashback and flame holding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If working fluid velocity is increased to purge trapped fuel from the end cap, then flashback risk is reduced, but pressure loss and energy consumption increase
Solution Approach 1:
The end cap is segmented into multiple functional zones: a diluent plenum chamber for fuel trapping, axial purge ports for active purging, and radial gaps for passive flow. This segmentation allows different regions to perform specialized functions, enabling effective fuel removal without requiring high velocity throughout the entire end cap, thus reducing energy consumption while maintaining flashback prevention.
Solution Approach 2:
The diluent plenum chamber is positioned upstream to trap and accumulate leaked fuel before it can migrate toward the fuel nozzles. By performing the purging action in advance at a location where fuel accumulation occurs, the system prevents flashback conditions from developing, reducing the need for high-velocity working fluid later.
2Productivity
If tube diameter is increased to improve fuel mixing, then combustion efficiency improves, but the ability to purge trapped fuel deteriorates
Solution Approach 1:
The invention introduces axial purge ports that extend through the tubes in addition to the radial mixing function. This adds a new dimension (axial flow path) to the tube functionality, allowing the same tube structure to perform both enhanced radial mixing and effective axial purging of trapped fuel, thereby maintaining both combustion efficiency and purging capability.
Solution Approach 2:
The tube structure is segmented into multiple functional elements: radial walls for fuel mixing, axial purge ports for fuel removal, and radial gaps for flow communication. This segmentation allows each element to optimize its specific function without compromising the others, enabling both efficient mixing and effective purging.
3Manufacturing precision
If radial gaps between tubes and plate are reduced to improve manufacturing precision, then assembly tolerance improves, but working fluid velocity and purging effectiveness deteriorate
Solution Approach 1:
The radial gaps are intentionally designed as dedicated flow channels that communicate with the diluent plenum chamber. By establishing these gaps as predefined flow paths during manufacturing, the system ensures adequate working fluid velocity for purging without requiring post-assembly adjustments, thus maintaining both manufacturing precision and purging effectiveness.
Solution Approach 2:
The radial gaps act as intermediary flow channels between the main working fluid path and the diluent plenum chamber. These gaps provide a controlled pathway for working fluid to enter the plenum and purge trapped fuel, mediating between the conflicting requirements of tight tolerances and sufficient flow velocity.
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 design effectively purges trapped fuel from the end cap, minimizing the risk of flashback and flame holding events, thereby protecting the fuel nozzles and enhancing the operational safety and efficiency of the combustor.
Implementation Method 1
flowing a working fluid through a plurality of tubes that extend axially through an end cap, flowing a fuel into the plurality of tubes, and flowing at least a portion of the working fluid through a diluent plenum located inside the end cap and into one or more of the plurality of tubes
Data Source
Figure 1
Figure 2
AI summary
A combustor (10) includes an end cap (28). The end cap (28) includes a first surface (30) and a second surface (32) downstream from the first surface (30), a shroud (24) that circumferentially surrounds at least a portion of the first and second surfaces (30,32), a plate (34) that extends radially within the shroud (24), a plurality of tubes (36) that extend through the plate (34) and the first and second surfaces (30,32), and a first purge port that extends through one or more of the plurality of tubes, (36) wherein the purge port is axially aligned with the plate (34).