Angled Fuel Injector Burner Head for NOx Reduction
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Solution Overview
Problem
Current combustion systems fail to meet stringent nitrogen oxide emission limits, particularly at high combustion chamber loads, and require further reduction of pollutants like NOx emissions.
Innovation Solution
A combustion head design with a burner tube and guide devices that direct fuel nozzles to deliver fuel at an angle, creating a flame front spaced away from the combustion head, allowing for recirculation of exhaust gases to mix with fuel downstream, reducing NOx production and stabilizing the flame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional combustion heads are used, then combustion efficiency is maintained, but nitrogen oxide emissions increase at high loads
Solution Approach 1:
The combustion process is segmented into distinct zones: a first combustion zone with stoichiometric or slightly excess air near the burner head, and a second combustion zone further downstream with additional fuel injection and recirculated exhaust gas. This segmentation allows primary combustion to occur at controlled temperatures while secondary combustion completes the process at lower temperatures, reducing NOx formation throughout the load range.
Solution Approach 2:
Exhaust gas recirculation is implemented as a preliminary action before the main combustion process. The recirculated exhaust gas is mixed with the fuel-air mixture before ignition, pre-cooling the combustion charge and reducing peak flame temperatures. This preliminary cooling action prevents NOx formation from the outset while maintaining combustion efficiency at high loads.
2Object-generated harmful factors
If exhaust gas recirculation is increased to reduce NOx, then nitrogen oxide emissions decrease, but combustion stability deteriorates
Solution Approach 1:
Different air-fuel ratios are applied to different spatial locations and combustion stages. The first combustion zone operates with stoichiometric or slightly excess air (lambda ≥ 1) for stable ignition and initial combustion. The second combustion zone downstream receives recirculated exhaust gas and additional fuel with substoichiometric mixture (lambda < 1), completing combustion while maintaining stability through the staged approach rather than uniform mixing throughout.
Solution Approach 2:
The combustion chamber is divided into multiple combustion zones with distinct air-fuel ratios and combustion characteristics. This spatial segmentation allows the system to maintain combustion stability in the first zone while using exhaust gas recirculation in the second zone to reduce NOx, thereby decoupling the stability and emissions concerns that would conflict in a single-zone system.
3Object-generated harmful factors
If flame temperature is reduced to lower NOx formation, then nitrogen oxide emissions decrease, but combustion efficiency decreases
Solution Approach 1:
The combustion process is divided into two stages: first combustion at controlled temperatures with stoichiometric or excess air maintains good combustion efficiency and stability, while second combustion downstream with recirculated exhaust gas and additional fuel completes the combustion of remaining combustibles at lower temperatures. This segmentation ensures that energy efficiency is optimized in the first stage while NOx reduction is achieved in the second stage, preventing the trade-off that would occur with uniform temperature reduction throughout.
Solution Approach 2:
The air-fuel ratio parameter is changed between combustion zones: the first zone operates with lambda ≥ 1 for efficient and complete combustion, while the second zone operates with lambda < 1 (substoichiometric) mixed with recirculated exhaust gas. This parameter change allows the system to achieve both high combustion efficiency in the first zone and low NOx formation in the second zone, as the substoichiometric second zone burns at lower temperatures where NOx formation is suppressed.
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 reduces NOx emissions and achieves stable combustion with lower oxygen requirements, maintaining low emissions even at high loads, and enhances fuel preparation by mixing recirculated gases with fuel before ignition, reducing flame temperature and NOx formation.
Implementation Method 1
at least one guide device arranged at the downstream end, which extends radially inwards at a first angle, i.e. at an angle between 0° and 90° in the direction of the burner tube axis, and one or more fuel nozzles arranged in the burner tube are designed to deliver fuel at a second angle radially outwards in the direction downstream
Implementation Method 2
recirculated exhaust gases lower the flame temperature, reducing the amount of nitrogen oxides produced at high combustion temperatures
Implementation Method 3
recirculated exhaust gases lower the flame temperature
Implementation Method 4
The combustion of fossil fuels in combustion systems generally produces pollutant emissions
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
The burner head comprises a burner pipe (18) with guide plates (34) which point inwards mounted at the downstream end. A fuel injector (26) is mounted between these and has a second set of plates (24) which point outwards mounted around it. An independent claim is included for a method for burning fuel using the burner head.