Gas heater, method for operating the gas heater and a gas boiler
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Solution Overview
Problem
Conventional gas heaters using hydrogen as a fuel face significant challenges with flashback, where the combustion flame propagates back into the burner and supply channel, potentially causing explosive bangs due to high flame speed, making it difficult to maintain stable combustion.
Innovation Solution
Incorporating a check valve in the supply channel downstream of the mixing area, which remains closed for a delay time after a flashback occurs, preventing the flashback from propagating further and ensuring complete combustion of the mixture downstream before reopening, thus preventing sonic speed and explosive sounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If hydrogen is used as gaseous fuel to replace natural gas, then greenhouse gas emissions are reduced to zero, but the flame speed increases significantly causing flashback to occur more likely
Solution Approach 1:
A check valve is introduced as an intermediary component in the supply channel between the mixing area and the burner. This valve acts as a mediator that allows normal gas flow during operation but automatically closes to block the supply channel when flashback occurs, preventing the flame from propagating further into the fuel supply system.
Solution Approach 2:
The check valve is positioned upstream of the burner in the supply channel to preemptively prevent flashback from reaching critical areas. By placing the valve in advance in the flow path, the system prepares a protective barrier before flashback can cause damage, allowing automatic closure to stop the reverse flame propagation.
2Reliability
If the mixture velocity is increased to prevent flashback, then flashback is reduced, but the risk of blow-off increases and combustion stability deteriorates
Solution Approach 1:
The check valve serves as a protective intermediary that enables the system to maintain lower mixture velocities for stable combustion while providing automatic protection against flashback. The valve allows the optimal mixing ratio to be maintained without the need to increase velocity as a preventive measure.
3Reliability
If a check valve is added to the supply channel to prevent flashback, then flashback propagation is stopped, but device complexity increases
Solution Approach 1:
The check valve is designed as a self-acting component that automatically responds to flashback conditions without requiring external control systems. The valve body moves in response to pressure changes caused by flashback, closing the valve passively based on the flow direction reversal, thereby preventing flashback propagation through a simple, autonomous mechanism.
4Reliability
If the check valve closes immediately upon flashback detection, then flashback is prevented, but complete combustion of remaining mixture downstream may be interrupted
Solution Approach 1:
The check valve incorporates a delayed closure mechanism that allows the valve to remain open for a predetermined period after flashback detection. This dynamic timing allows the flame to propagate through and completely combust the remaining combustible mixture in the supply channel downstream before the valve closes, preventing both flashback and energy loss from incomplete combustion.
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
Effectively stops flashback at the check valve, preventing explosive sounds and ensuring stable combustion without the need for increased blower pressure or risk of blow-off, maintaining efficient operation with hydrogen as a fuel.
Implementation Method 1
The valve body has a first end position in which the check valve is opened and in the direction of which the valve body is urged in a first pressure condition in which a pressure upstream from the valve is higher than a pressure downstream of the valve
Implementation Method 2
The mixture will combust or burn with a certain flame speed
Implementation Method 3
The flame speed is the measured rate of expansion of the flame front in a combustion reaction
Data Source
Figure 1
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Figure 3
AI summary
A gas heater comprising, a premix burner, a supply channel for supplying a mixture of a gaseous fuel and air to the burner, and a check valve placed in the supply channel upstream of the burner. The check valve comprises a moveable valve body having a first end position in which the check valve is opened and a second end position in which the check valve is closed. In a first pressure condition in which a pressure upstream is higher than a pressure downstream, the valve body is urged to the first end position. In a second pressure condition in which the pressure upstream is lower than the pressure downstream the valve body is urged to the second end position. After closure of the check valve the check valve remains closed for a delay time.