Flat Premix Burner Layout for Low-NOX HVAC Furnaces
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Solution Overview
Problem
Gas-fired HVAC furnaces emit high levels of nitrogen oxides (NOX) due to suboptimal air-fuel mixtures and combustion temperatures, necessitating a solution to reduce NOX emissions efficiently and economically while maintaining space efficiency.
Innovation Solution
The implementation of a flat burner system with a premix configuration, where air and fuel are mixed upstream and passed through a permeable flat burner positioned between a mixing box and a post-combustion chamber, allowing for even distribution and combustion, thereby reducing NOX production by lowering the burn temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional gas-fired burners are used, then heating function is provided, but NOX emissions are high due to suboptimal air-fuel mixtures and combustion temperatures
Solution Approach 1:
The patent applies preliminary action by pre-mixing air and fuel in specific proportions before combustion occurs in the burners. This pre-mixing chamber allows the air-fuel mixture to be optimized prior to combustion, ensuring that combustion happens at controlled temperatures that minimize NOX formation while maintaining heating efficiency. The pre-mixing step precedes the combustion process to establish optimal conditions.
Solution Approach 2:
The patent changes key parameters including air-fuel ratio, combustion temperature, and burner geometry. By adjusting the air-fuel mixture ratio to be more precise and controlling combustion temperature through the pre-mixing design, the system reduces peak combustion temperatures that cause NOX formation. The burner design parameters are specifically modified to achieve lower combustion temperatures while maintaining adequate heating output.
2Object-affected harmful factors
If combustion temperature is reduced to lower NOX production, then NOX emissions decrease, but combustion efficiency may be compromised
Solution Approach 1:
The patent applies local quality by creating different zones within the combustion system with different characteristics. The pre-mixing chamber provides a controlled environment with specific air-fuel ratios, while the burner zones are designed with varying geometry to maintain adequate combustion efficiency. Different parts of the combustion system have optimized local conditions - the pre-mixing zone controls temperature to reduce NOX, while the burner zones ensure complete combustion for efficiency.
Solution Approach 2:
The patent optimizes multiple parameters simultaneously: air-fuel ratio is adjusted to prevent both excessive temperature (which causes NOX) and incomplete combustion (which reduces efficiency). The combustion temperature is controlled within a specific range that balances NOX reduction with maintained combustion efficiency. Burner geometry parameters are also optimized to ensure proper flame characteristics and heat release rates.
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 approach effectively lowers NOX emissions below 14 ng/J of energy used, achieving a balance between efficiency and space efficiency by promoting homogeneous mixing and controlled combustion, reducing surface temperatures and NOX production.
Implementation Method 1
allowing for even distribution and combustion, thereby reducing NOX production by lowering the burn temperature
Implementation Method 2
an upstream heat exchanger comprising a plurality of parallel heat exchanger flow paths configured to receive fluid from the cavity
Data Source
AI summary
A heating, ventilation, and/or air conditioning (HVAC) furnace has a flat burner comprising an upstream side and a downstream side, the flat burner being configured to receive an air-fuel mixture therethrough, a first flow path located adjacent the flat burner and downstream relative to the flat burner, the first flow path configured to receive fluid exiting the flat burner, and a plurality of second flow paths located downstream relative to the first flow path, the plurality of second flow paths being configured to receive fluid from the first flow path.