Venturi Fuel-Air Mixing and Diffuser Plate for Quiet Low-NOx Heating
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Solution Overview
Problem
Conventional fuel-fired heating appliances suffer from uneven heating of heat exchanger tubes, high noise levels during fuel/air mixture creation, low fuel/air mixing efficiency, and excessive NOx emissions due to configurational issues.
Innovation Solution
A specially designed combustion system featuring a venturi-based primary fuel/air mixing structure with a sound-attenuating chamber and a secondary mixing structure, combined with a perforated diffuser plate to enhance mixing and reduce noise, and a diffuser plate with a non-uniform perforation pattern to manage combustion gas flow and NOx levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional fuel/air mixing structures are used, then the heating appliance can operate, but uneven heating of heat exchanger tubes occurs resulting in non-uniform temperature distribution
Solution Approach 1:
The diffuser plate incorporates non-uniformly distributed openings with varying sizes and patterns to create localized variations in fuel/air mixture distribution. This local quality variation ensures that heat exchanger tubes receive more or less combustion gas depending on their position, achieving uniform overall temperature distribution across all tubes.
2Productivity
If conventional fuel/air mixing structures are used, then the appliance can fire, but high noise levels are generated during fuel/air mixture creation
Solution Approach 1:
A sound attenuating chamber is introduced as an intermediary component between the fuel/air mixing process and the external environment. This chamber absorbs and dampens noise generated during fuel/air mixture creation and combustion, significantly reducing the noise level while maintaining the firing capability of the appliance.
3Productivity
If conventional mixing structures are used, then the appliance can operate, but low fuel/air mixing efficiency results in poor combustion
Solution Approach 1:
The fuel/air mixing process is divided into multiple stages: primary mixing in the venturi injector, secondary mixing in the mixing chamber, and tertiary distribution through the diffuser plate openings. This segmentation allows progressive and thorough mixing of fuel and air, significantly improving mixing efficiency and combustion performance.
Solution Approach 2:
The venturi injector utilizes pneumatic principles where high-velocity air flow creates a pressure drop that draws fuel into the stream. The flowing air dynamically mixes with fuel through turbulence and shear forces, achieving efficient fuel/air mixing without mechanical moving parts.
4Temperature
If conventional combustion structures are used, then the appliance can heat, but excessive NOx emissions are generated during combustion
Solution Approach 1:
Fuel and air are thoroughly mixed before combustion occurs in the diffuser plate and combustion chamber. This preliminary mixing ensures complete and efficient combustion at lower temperatures, reducing the formation of thermal NOx. The non-uniform opening pattern also creates localized combustion zones that prevent excessive temperature peaks.
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
The solution achieves improved fuel/air mixing, reduced noise, and uniform temperature distribution across heat exchanger tubes, while lowering NOx emissions and operational noise levels, thereby enhancing the efficiency and performance of fuel-fired heating appliances.
Implementation Method 1
a venturi structure having a longitudinal axis extending centrally therethrough
Implementation Method 2
a sound-attenuating chamber in said primary fuel/air mixing structure
Implementation Method 3
a circumferentially spaced array of swirl-inducing vanes radially extending across said annular end wall opening
Implementation Method 4
a diffuser plate with a non-uniform perforation pattern to manage combustion gas flow
Implementation Method 5
a fuel/air mixture combustion structure to combust said fuel/air mixture and thereby create hot combustion gases
Data Source
AI summary
A fuel-fired furnace incorporates specially designed fuel/air mixing and combustion structures. The fuel/air mixing structure is of a mixing sound-attenuating design and comprises a venturi having a perforated sidewall portion and being surrounded by a noise-damping housing chamber communicating with the interior of the venturi via its sidewall perforations. During use of the mixing structure, air is flowed through the venturi in a swirling pattern while fuel is transversely injected internally against the swirling air. The combustion structure comprises a burner box housing into which the fuel/air mixture is flowed, combusted, and then discharged as hot combustion gas into and through the heat exchanger tubes. The fuel/air mixture entering the burner box housing initially passes through a non-uniformly perforated diffuser plate functioning to substantially alter in a predetermined manner the relative combustion gas flow rates through the heat exchanger tubes.