Perforated Flame Holder Burner for NOx Reduction
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Solution Overview
Problem
Current burners face challenges in achieving stable and efficient combustion with reduced NOx emissions, as existing designs often result in either rich or lean fuel mixtures, leading to unstable flames and higher NOx output.
Innovation Solution
A burner design featuring a perforated flame holder with elongated apertures and a burner tile that allows for selective premixing and ignition of fuel streams, utilizing a diverging fuel stream and oxidizer mixture, which supports a secondary flame in elongated apertures and an intermediate flame support surface to control premixing and combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the flame holder is positioned close to the fuel nozzle, then the fuel mixture is richer and combustion efficiency is improved, but the flame becomes unstable and NOx emissions increase
Solution Approach 1:
The patent applies preliminary action by creating a premixing region between the fuel nozzle and flame holder where fuel and oxidizer mix before combustion. This controlled premixing allows the flame to stabilize in a richer mixture condition while preventing the instability that would occur with direct proximity ignition.
Solution Approach 2:
The perforated flame holder acts as an intermediary structure that mediates between the fuel nozzle and the combustion zone. It provides a controlled interface that allows rich fuel mixture delivery while maintaining flame stability through its perforated structure and spacing.
2Reliability
If the flame holder is positioned far from the fuel nozzle, then the fuel mixture is leaner and flame stability is improved, but combustion efficiency decreases and NOx emissions increase
Solution Approach 1:
The premixing region creates a controlled mixing zone before the flame holder, allowing the fuel stream to pre-mix with oxidizer in a controlled manner. This ensures that when the flame stabilizes in the elongated apertures, it receives a rich mixture for high efficiency combustion while maintaining stability through the controlled mixing process.
Solution Approach 2:
The patent changes the mixture ratio parameter by controlling the amount of oxidizer mixed with the fuel stream in the premixing region. This allows the system to operate with a rich mixture (for efficiency) while maintaining flame stability through the controlled premixing process and proper flame holder positioning.
3Device complexity
If conventional burners are used, then the structure is simple, but NOx emissions are high due to unstable combustion
Solution Approach 1:
The burner is segmented into distinct functional zones: a premixing region for fuel-oxidizer mixing, a flame holder with elongated apertures for flame stabilization, and a combustion zone. This segmentation allows controlled combustion that reduces NOx emissions while maintaining reasonable structural complexity.
Solution Approach 2:
The flame holder utilizes a perforated (porous) structure with elongated apertures that allow controlled fuel flow and flame stabilization. This porous design enables rich mixture delivery for efficient combustion while maintaining flame stability, thereby reducing NOx emissions compared to conventional solid burners.
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 achieves a more stable and hotter flame with reduced NOx emissions by controlling premixing and ignition, allowing for a richer fuel mixture and improved combustion efficiency while minimizing NOx output.
Implementation Method 1
provide at least partial premixing of the diverging fuel stream with a fluid containing an oxidizer, such as air or flue gas in a premixing region between the fuel nozzle and the flame holder
Implementation Method 2
The flame holder is configured to support a flame in the plurality of elongated apertures and in regions immediately above the distal side of the flame holder and/or immediately below the proximal side of the flame holder
Data Source
AI summary
A perforated flame holder and burner including a perforated flame holder provides reduced oxides of nitrogen (NOx) during operation. The perforated flame holder includes a pattern of elongated apertures extending between a proximal and a distal surface of the flame holder relative to a fuel nozzle. The perforated flame holder can provide a significantly reduced flame height while maintaining heat output from the burner.