Method for detecting the presence of flame in a premixed hydrogen burner
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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 flashback, detonation, and inaccurate flame monitoring.
Innovation Solution
A method using a temperature sensor with a ceramic coating to monitor the derivative of temperature over time, comparing it against pre-set thresholds to rapidly detect flame ignition and extinguishment, ensuring rapid response and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional temperature sensors are used to detect flame presence, then the system can monitor temperature, but the response time is excessively long leading to safety risks
Solution Approach 1:
The patent replaces conventional temperature sensors with a ceramic-coated temperature sensor that directly contacts the flame. The ceramic coating (alumina or zirconia) enables the sensor to withstand high temperatures while providing rapid thermal response. This substitution of sensor technology achieves both fast response time and reliable detection, resolving the contradiction between speed and reliability.
Solution Approach 2:
The patent changes the thermal and chemical parameters of the sensing system by using a ceramic coating with specific thermal conductivity and heat capacity properties. The coating thickness and material composition are optimized to achieve rapid heat transfer from the flame to the sensor while protecting it from damage. This parameter optimization enables simultaneous achievement of fast response and reliable operation.
2Speed
If ultraviolet sensors are used to monitor hydrogen combustion, then the time constant is very low, but sensitivity is insufficient at low power or high air/gas ratios
Solution Approach 1:
The patent introduces a ceramic-coated temperature sensor as an intermediary between the flame and the detection system. The ceramic coating acts as a thermal mediator that efficiently transfers heat from the flame to the temperature sensor, enabling reliable detection across all operating conditions including low power and high air/gas ratios, while maintaining rapid response characteristics.
3Reliability
If optical sensors are used for flame monitoring, then flame presence can be detected, but the optical connection glass is prone to fogging during transients causing erroneous readings
Solution Approach 1:
The patent replaces the optical sensing system with a direct-contact temperature sensing system. By eliminating the optical glass window and using a ceramic-coated temperature sensor that physically contacts the flame, the system avoids the fogging problem entirely while maintaining reliable flame detection capability.
4Reliability
If the burner operates with high excess air λ to prevent flashback, then safety is improved, but flame detection becomes more difficult due to diluted combustion
Solution Approach 1:
The ceramic coating serves as an intermediary that enhances heat transfer efficiency from the diluted flame to the temperature sensor. Even when the flame is diluted by high excess air, the ceramic coating's thermal properties ensure sufficient heat transfer to maintain reliable detection, allowing the system to operate safely with high excess air while preserving detection capability.
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, minimizing the risk of detonations and ensuring safe operation by quickly identifying ignition and extinguishment events, thus stabilizing the flame.
Implementation Method 1
a temperature sensor with a ceramic coating to monitor the derivative of temperature over time
Implementation Method 2
A premixed gas burner... equipped with a device for controlling the presence of a flame... temperature sensor with a ceramic coating
Data Source
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.