Flame Arrestor in Gas Heater Mixed Gas Line

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Solution Overview

Problem

Gas burners in condensing boilers are prone to flashbacks due to high flame speeds and elevated temperatures, leading to mechanical and thermal overloads, particularly affecting components like fan impellers.

Innovation Solution

Incorporating a flame arrestor between the air supply and burner, which spans the mixture gas line cross-section, made of high-temperature resistant materials like metal or ceramic, to extinguish the flame in case of flashback and prevent pressure surges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a flame arrestor is installed in the mixed gas line, then mechanical and thermal stresses from flame flashbacks are reduced, but device complexity increases

Engineering Contradiction:
Improveprotection against flame flashbackVSAvoidnumber of components
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

A flame arrestor is introduced as an intermediary component in the mixed gas line between the burner and the fan. This flame arrestor contains a flame-propagating mixture and prevents flame flashbacks from reaching the fan, thereby protecting the system while maintaining a relatively simple overall structure.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The flame arrestor utilizes porous materials or a honeycomb structure with fine channels. These structures allow the gas mixture to pass through while the narrow channels quench flames through heat loss to the walls, preventing flame propagation upstream without requiring complex active control systems.

Inventive Principle:
Principle #31Porous materials

2Reliability

If the flame arrestor is positioned close to the burner, then protection effectiveness is improved, but the risk of thermal damage to the flame arrestor increases

Engineering Contradiction:
Improveflame flashback preventionVSAvoidthermal stress on flame arrestor
Core Design Contradiction:
ReliabilityVSTemperature

Solution Approach 1:

The flame arrestor is designed with localized high-temperature resistance properties at the region exposed to potential flame flashback. The housing material is selected to withstand high temperatures, while the internal porous or honeycomb structure provides flame quenching. This localized approach allows effective flame arrestment without requiring the entire device to withstand extreme thermal conditions.

Inventive Principle:
Principle #3Local quality

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 flame arrestor effectively reduces or avoids mechanical and thermal loads by extinguishing the flame before it reaches critical components, minimizing damage from pressure surges and thermal overloads.

Implementation Method 1

The flame arrestor utilizes porous materials or a honeycomb structure with fine channels. These structures allow the gas mixture to pass through while the narrow channels quench flames through heat loss to the walls, preventing flame propagation upstream.

Methodology Applied
Scientific EffectHeat loss to walls: Conduction (thermal)

Implementation Method 2

the narrow channels quench flames through heat loss to the walls

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP3974719A1Gas heater
Publication Date: 2022.03.30 VAILLANT GMBH(DE)
  • EP3974719A1 patent drawingFigure 1
  • EP3974719A1 patent drawingFigure 2~3
  • EP3974719A1 patent drawing

AI summary

The invention relates to a gas heating appliance (1) comprising at least one fuel gas supply (2), one air supply (3), one mixed gas line (4), and a burner (5) with at least one perforated plate (15) forming a mixed gas cavity. It is proposed that at least one flame arrestor (6) with a length of at least 20 mm in the direction of flow (13) of the mixed gas be provided between the air supply (3) and the burner (5), extending over a cross-sectional area of ​​the mixed gas line (4), the air supply (3), or the fuel gas supply (2).