Burner Mixing Device for Low NOx Emissions
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Solution Overview
Problem
Existing burners struggle to achieve low nitrogen oxide (NOx) emissions, especially at high power levels, despite having mixing devices with primary and secondary flame zones and baffle plates for combustion stabilization.
Innovation Solution
A mixing device with a centrally arranged first mixing unit, a second mixing unit with multiple nozzles for a secondary flame zone, a sealing air producing unit, and a third mixing unit for premixing and swirling a fuel-air mixture, which is delivered between the sealing air and secondary flame zones, along with a baffle plate design that enhances air resistance and swirl generation, and a fuel supply system that adjusts fuel ratios based on load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional mixing device with primary and secondary flame zones is used, then combustion stability is maintained, but nitrogen oxide emissions increase at high power levels
Solution Approach 1:
The mixing device is divided into three distinct mixing units (first, second, and third mixing units) that operate in sequence. Each unit performs a specific function: the first mixing unit creates a primary fuel-air mixture, the second mixing unit adds secondary air, and the third mixing unit introduces tertiary air. This segmentation allows progressive mixing and temperature control, reducing nitrogen oxide formation while maintaining combustion stability at high power levels.
Solution Approach 2:
The invention transitions from a conventional two-zone flame structure to a three-dimensional multi-layer mixing approach. By arranging mixing units at different spatial positions and introducing air from multiple directions (primary, secondary, and tertiary air streams), the system creates a more distributed combustion process that reduces peak temperatures and nitrogen oxide emissions while preserving burner power.
2Object-generated harmful factors
If flame temperature is reduced to lower NOx emissions, then nitrogen oxide production decreases, but combustion stability deteriorates
Solution Approach 1:
The first mixing unit performs preliminary mixing of fuel and primary air to create a stable core flame. This pre-established combustion zone serves as a stable foundation before secondary and tertiary air are introduced. The preliminary action ensures that combustion stability is maintained even as additional air streams are added to reduce peak temperatures and nitrogen oxide emissions.
Solution Approach 2:
Different regions of the combustion process are given different air-fuel ratios and mixing characteristics. The first mixing unit creates a fuel-rich core zone for stability, while the second and third mixing units introduce progressively more air to reduce temperature. This local differentiation allows the system to maintain stability in the core while reducing NOx emissions in the outer regions.
3Stability of the object's composition
If a baffle plate is used to stabilize the primary flame, then flame stability improves, but air resistance increases and mixing efficiency decreases
Solution Approach 1:
Instead of using a single large baffle plate, the invention segments the air mixing function into three separate mixing units distributed along the combustion path. Each mixing unit handles a specific portion of the air-fuel mixing process, reducing the need for large baffle plates and minimizing air resistance while maintaining flame stability through progressive mixing.
Solution Approach 2:
The invention extracts the flame stabilization function from the baffle plate and assigns it to the first mixing unit, which creates a stable primary fuel-air mixture. This allows the baffle plate to be minimized or eliminated, reducing air resistance while the first mixing unit maintains combustion stability through controlled fuel-air premixing.
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 configuration reduces NOx production by optimizing flame stability and mixing ratios, allowing for lower flame temperatures and increased exhaust gas recirculation, even at high power levels, thereby achieving lower NOx emissions.
Implementation Method 1
a third mixing unit for premixing and swirling a third fuel-air mixture and for delivering the premixed and swirled third fuel-air mixture into a swirled flame zone
Implementation Method 2
the first mixing unit has at least one first fuel nozzle and a baffle plate
Implementation Method 3
combustion-chamber-internal exhaust gas recirculation is enabled via the secondary flame
Data Source
AI summary
To further reduce the NOx emission, the invention provides a mixing device (10) for a burner (16) having reduced NOx production, comprising a centrally arranged first mixing unit (18) for producing a first fuel-air mixture for a primary flame zone (120), wherein the first mixing unit (18) has at least one first fuel nozzle (38) and a baffle plate (40), a second mixing unit (20) for producing a second fuel-air mixture for a secondary flame zone (122), which encloses the primary flame zone (120), wherein the second mixing unit (20) has multiple second fuel nozzles (70), characterized by a sealing air producing unit (24) for producing a sealing air flow in a sealing air zone, which encloses the primary flame zone (120) of the first mixing unit (18) arranged downstream of the baffle plate (40), wherein the second mixing unit (20) is designed to deliver the second fuel-air mixture into the secondary flame zone (122), which encloses the sealing air zone (126), and wherein the second mixing unit (20) is arranged around the sealing air producing unit (24), and by a third mixing unit (22) which is arranged radially between the sealing air producing unit (24) and the second mixing unit (20) and has a swirl generator (76) and at least one third fuel nozzle (74), which is arranged upstream of the swirl generator (76) in a premixing zone (78), through which a swirled air flow flows to the swirl generator (76), to premix fuel from the third fuel nozzle (74) with the swirled air flow before the swirl generation.