Premixed Hydrogen Burner Flame Detection by Temperature Derivative
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Solution Overview
Problem
Existing flame detection methods for hydrogen-fed premixed burners, particularly at low thermal power or high air/fuel ratios, are unreliable due to slow response times and sensitivity issues with conventional sensors, leading to risks of detonations and inaccurate flame monitoring.
Innovation Solution
A method using a temperature sensor with a ceramic coating to detect flame presence by calculating the derivative of temperature over time, comparing it to pre-set thresholds, and employing a post-ventilation step to prevent accumulation and ensure rapid detection of ignition and extinguishment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional temperature sensors are used to detect flame presence, then the system can monitor combustion, but the response time is excessively long leading to risk of detonations
Solution Approach 1:
The patent changes the monitoring parameter from absolute temperature to the derivative of temperature over time (dT/dt). This parameter transformation enables much faster detection of flame events because the temperature rate of change occurs much more rapidly than the temperature itself during ignition and extinguishment events, reducing response time from seconds to milliseconds while maintaining detection reliability
Solution Approach 2:
The system pre-calculates and stores reference values for the temperature derivative under known flame and no-flame conditions. By having these reference values prepared in advance, the system can immediately compare real-time measurements against them without computation delays, enabling rapid flame detection and preventing detonations
2Speed
If ultraviolet sensors are used to monitor hydrogen combustion, then response time is fast, but sensitivity is insufficient at low power or high air/gas ratios
Solution Approach 1:
The patent transforms the detection approach by monitoring the rate of temperature change rather than relying on optical emissions. This parameter change enables reliable detection across the full operating range including low power and high air/gas ratio conditions where ultraviolet sensor sensitivity fails, while maintaining fast response characteristics
Solution Approach 2:
The patent introduces a ceramic-coated temperature sensor as an intermediary that can withstand the harsh combustion environment while providing accurate thermal measurements. The ceramic coating protects the sensor and enables reliable temperature derivative measurement, serving as a mediator between the extreme combustion conditions and the detection system
3Measurement precision
If optical sensors are used for flame monitoring, then detection capability is enhanced, but the system is prone to fogging during transient regimes causing erroneous readings
Solution Approach 1:
The patent uses a ceramic coating on the temperature sensor as a protective intermediary that is resistant to fogging and condensation. This ceramic barrier allows the sensor to maintain accurate temperature measurements during transient operating regimes without the fogging problems that plague optical sensors, ensuring reliable reading accuracy
Solution Approach 2:
The patent replaces the optical detection system with a thermal detection system based on temperature derivative measurement. This substitution eliminates the optical path vulnerabilities to fogging and condensation, using thermal conduction through the ceramic-coated sensor instead, thereby maintaining detection accuracy while improving reliability during transients
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 method provides rapid and reliable flame detection, reducing the risk of detonations and ensuring safe operation by quickly identifying ignition and extinguishment, thus managing transients effectively.
Implementation Method 1
a temperature sensor (6), adapted to detect the presence of the flame
Implementation Method 2
generating an electric discharge with an ignition device (5) for a first time interval Δt1
Implementation Method 3
a fan (2)... providing a flow of air into said burner body (4)
Data Source
Figure 1
Figure 2.A~5.B
Figure 3~4
AI summary
The object of the present invention is a control method for verifying the presence of the flame in the combustion chamber (41) of a premixed gas burner (1), fed by an air and gas mixture mainly and/or essentially comprising hydrogen H2. The method is based on the use of at least one temperature sensor (6), the values whereof are sent to a control device (8) which uses them to calculate the derivative T' over time of the temperature T to compare it to suitable feedback thresholds (Tau1, Tau2; Tau3, Tau4) to establish the ignition occurred, the ignition failure or flame extinguishment.