Flame arrestor assembly for a gas water heater appliance
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Solution Overview
Problem
Conventional gas water heaters face challenges in meeting NOx emissions standards while avoiding pilot flame instability and combustion noise due to restricted secondary air flow, which can result in audible sounds oscillating at 1300 Hertz.
Innovation Solution
The implementation of a flame arrestor assembly with a restrictor plate and apertures, along with a controlled air inlet and gap, to regulate pilot air flow and pressure drop, enhancing flame stability and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If secondary air flow is restricted to reduce NOx emissions, then emissions standards are met, but pilot flame stability deteriorates and combustion noise increases
Solution Approach 1:
The air flow restriction is segmented into multiple small apertures in the restrictor plate rather than a single large opening. This segmentation allows precise control of secondary air flow to reduce NOx emissions while maintaining pilot flame stability through distributed air injection points.
Solution Approach 2:
A flame arrestor assembly with restrictor plate is introduced as an intermediary component between the secondary air source and the combustion chamber. This intermediary device regulates air flow to achieve emission reductions while preventing flame instability and combustion noise through controlled air injection.
2Object-generated harmful factors
If secondary air flow is restricted to reduce NOx emissions, then emissions standards are met, but combustion noise increases to audible levels
Solution Approach 1:
The air flow restriction is divided into multiple small apertures rather than a single opening, which distributes the pressure drop and prevents audible combustion noise while maintaining effective NOx reduction through controlled secondary air flow.
Solution Approach 2:
The aperture size and configuration parameters in the restrictor plate are optimized to create appropriate pressure drops that reduce NOx emissions without generating audible combustion noise, balancing emission control with acoustic performance.
3Reliability
If a flame arrestor and restrictor plate are added to control air flow, then pilot flame stability and noise are improved, but device complexity increases
Solution Approach 1:
The flame arrestor and restrictor plate functions are merged into a single integrated arrestor assembly that combines flame containment and air flow restriction capabilities, reducing overall device complexity while maintaining pilot flame stability and noise control.
Solution Approach 2:
The restrictor plate serves multiple functions simultaneously: it restricts secondary air flow for NOx reduction, provides flame containment through the arrestor structure, and controls pressure drop to prevent combustion noise, eliminating the need for separate components for each function.
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 improves pilot flame stability and reduces combustion noise, thereby meeting emissions standards and enhancing consumer satisfaction and appliance performance.
Implementation Method 1
an arrestor assembly mounted to the combustion chamber wall above the pilot air inlet and below the gas burner. The arrestor assembly includes a flame arrestor and a restrictor plate positioned adjacent the flame arrestor
Implementation Method 2
the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between the pilot air inlet and the combustion chamber
Data Source
AI summary
A gas water heater appliance includes a tank for storage of water for heating, a combustion chamber wall positioned below the tank and defining a combustion chamber and a pilot air inlet, a gas burner positioned within the combustion chamber to heat the water in the tank, and an arrestor assembly mounted to the combustion chamber wall above the pilot air inlet and below the gas burner. The arrestor assembly includes a flame arrestor and a restrictor plate positioned adjacent the flame arrestor, the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between the pilot air inlet and the combustion chamber.