Broad Spectrum Flame Detector with Guard Sensor
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Solution Overview
Problem
Conventional flame detectors are limited by their narrowband focus on the 4.3 micron CO2 peak, failing to detect fuels without carbon, being susceptible to false alarms, and requiring expensive sapphire windows and frequent cleaning due to sensitivity to contaminants, which increases costs and reduces detection accuracy.
Innovation Solution
A BroadSpectrum flame detector that uses a multisensory approach with a sensory gap between the fire band and guard band, employing PbS or InGaAs sensors with different optical filters to detect radiation across a wider spectrum, rejecting regular modulation, and reacting to irregular modulation between 1Hz to 30Hz, allowing for universal fuel detection and reduced false alarms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrowband detector is used to detect the 4.3 micron CO2 peak, then detection sensitivity for carbon-based fuels is improved, but detection capability for fuels without carbon (like hydrogen) is lost
Solution Approach 1:
The broad spectrum is segmented into multiple wavelength regions, each monitored by dedicated sensors. The system divides the spectrum into UV region (200-400nm), visible region (400-700nm), and IR regions (700nm-14um), with specific sensors assigned to detect different combustion signatures in each region, enabling comprehensive fuel detection
Solution Approach 2:
The detector system performs multiple detection functions simultaneously using a single integrated platform. It detects UV radiation from excited radicals, visible light from soot incandescence, and IR radiation from hot gases, making the system universally applicable to all fuel types including hydrogen, hydrocarbons, and alcohol-based fuels
2Measurement precision
If a narrowband detector focused on 4.3 micron is used, then detection accuracy for CO2 flames is improved, but false alarms from non-fire CO2 sources (like engines) increase
Solution Approach 1:
The detection system segments the spectral analysis into multiple regions and uses a sensory gap between 1.0-1.6 microns where neither fire nor engine CO2 radiate significantly. This segmentation allows the system to distinguish fire CO2 (detected at 4.3 micron) from engine CO2 (detected at 2.7 micron) by analyzing the spectral distribution pattern across multiple bands
Solution Approach 2:
The system uses feedback from multiple sensors across different wavelength regions to continuously analyze the spectral signature. By comparing the relative intensities and patterns of radiation across UV, visible, and IR regions, the system provides feedback to distinguish genuine fire signatures from false alarm sources, improving reliability
3Measurement precision
If a detector is designed to detect the 4.3 micron peak, then detection performance for clean flames is improved, but detection capability in dirty flame conditions (with smoke and soot) deteriorates
Solution Approach 1:
The system segments detection into multiple spectral regions, with specific sensors targeting UV radiation from excited radicals and visible radiation from soot incandescence. This segmentation allows detection of flames even when the 4.3 micron CO2 signal is blocked by smoke, as the UV and visible region sensors can detect combustion products that penetrate through particulates
Solution Approach 2:
The system changes the detection parameter from solely relying on 4.3 micron IR transmission to detecting radiation emission across multiple wavelength regions. By monitoring UV radiation from excited radicals and visible light from hot soot particles, the system adapts to dirty flame conditions where transmission-based detection fails
4Reliability
If sapphire windows are used to allow 4.3 micron light transmission, then detection capability is improved, but system cost and complexity increase
Solution Approach 1:
The optical path is segmented into multiple wavelength regions, each handled by appropriate sensor materials. The system uses standard glass windows for UV and visible region sensors, while IR sensors use their own optimized window materials, eliminating the need for expensive sapphire windows across the entire system
Solution Approach 2:
The system uses standard glass windows that are readily available and cost-effective, copying the optical properties needed for broad spectrum detection rather than requiring specialized sapphire windows. The standard glass transmits UV and visible light effectively, and the IR sensors are positioned to detect through appropriate optical paths
5Measurement precision
If the detector is designed for 4.3 micron detection, then initial detection capability is improved, but maintenance cost and operational complexity increase due to heating and cleaning requirements
Solution Approach 1:
The detection system segments the spectral monitoring into multiple independent sensor channels, with each sensor optimized for its specific wavelength region. This segmentation allows each sensor to operate at ambient temperature without requiring heating, and the modular design simplifies maintenance by allowing individual sensor replacement without affecting the entire system
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 enables early and accurate detection of fires from various fuels, reduces false alarms, and operates effectively behind standard glass without heating, maintaining performance over time and temperature variations, while being cost-effective.
Implementation Method 1
detecting an intensity of radiation F from a flame in a first region of the spectrum
Implementation Method 2
detecting an intensity of radiation G from a part of the spectrum associated with artificial light or sunlight
Implementation Method 3
a second region, identified with II, represents the near-infrared and short-/mid-infrared, which includes a characteristic black body-type heat signature emitted by a flaming material
Data Source
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AI summary
A flame detector (1) comprising: a fire sensor (2a), capable of detecting a characteristic blackbody-type radiated heat signature emitted by a flaming material; and a guard sensor (2b), for detecting an at least further part of the spectrum emitted by said material and which serves to assist in rejecting false alarms, wherein, in use during detection of a flame, the guard sensor (2b) detects an amount of radiation G and the fire sensor (2a) detects an amount of radiation F, and positive detection of a flaming material depends upon the following criteria: F > 0; G > 0; and F > G.