Fiber Optic CO2 Purity Sensor With Isothermal Gas Chamber
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Solution Overview
Problem
Existing carbon dioxide (CO2) purity detection methods face challenges such as thermal drifting issues in thermal conductivity detection, limitations in measuring CO2 purity when blended with hydrocarbon gases, and accuracy degradation due to variations in light absorption caused by temperature, pressure, and density changes.
Innovation Solution
A fiber optic CO2 purity sensor package with a periodic refractive index modulated fiber grating structure, a thermally conductive sensing layer, and a thermally insulated gas chamber, which maintains the sensor in an isothermal state and uses a light source, photodetector, and processing circuitry to analyze reflected optical signals for accurate CO2 purity measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If thermal conductivity detection (TCD) is used for CO2 purity detection, then general-purpose gas analysis capability is provided, but thermal drifting issues occur resulting in low measurement precision
Solution Approach 1:
The patent replaces thermal conductivity detection (TCD) with optical detection using a fiber Bragg grating (FBG) sensor system. The FBG sensor detects CO2 purity through optical wavelength shifts caused by thermal expansion and refractive index changes in the grating structure, eliminating the thermal drifting issues inherent in TCD mechanical/thermal systems while maintaining general-purpose gas analysis capability
Solution Approach 2:
The patent changes the detection parameter from thermal conductivity to optical wavelength. The FBG sensor measures CO2 purity by detecting wavelength shifts (Δλ) that occur in response to temperature and strain changes induced by CO2 absorption, providing high measurement precision without the thermal drift problems of TCD
2Measurement precision
If NDIR optical detection is used for CO2 purity measurement, then optical detection capability is provided, but measurement accuracy degrades when CO2 is blended with hydrocarbon gases
Solution Approach 1:
The patent applies local quality by using a fiber Bragg grating structure with specific localized modifications - the grating period and refractive index are modified in specific regions of the fiber to create sensitivity to CO2 while being insensitive to hydrocarbon interference. The sensing zone is locally optimized for CO2 detection through controlled thermal and optical properties
Solution Approach 2:
The patent introduces an intermediary mechanism - the fiber Bragg grating structure acts as a mediator that converts CO2 concentration changes into optical wavelength shifts. This intermediary transformation process eliminates the direct optical absorption measurement limitations of NDIR when dealing with hydrocarbon blends, as the FBG responds to thermal-structural changes rather than direct gas absorption
3Measurement precision
If fluorescence detection with dye embedded polymeric thin film is used, then optical CO2 purity monitoring is provided, but baseline drift and accuracy degradation occur due to variations in light absorption from temperature, pressure, and density changes
Solution Approach 1:
The patent replaces the fluorescence detection system with an FBG optical sensing system. Instead of using dye molecules that emit fluorescence and are susceptible to environmental variations, the FBG sensor uses the physical structure of the fiber grating itself, which provides inherent stability against temperature and pressure changes through its solid-state, distributed sensing mechanism
Solution Approach 2:
The fiber Bragg grating sensor is self-compensating for temperature and pressure effects. The FBG wavelength shift naturally accounts for environmental variations, and the system uses the fiber's own structural properties to maintain baseline stability without requiring external reference measurements or complex compensation algorithms
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 provides high sensitivity and accuracy in measuring CO2 purity across a wide range, effectively addressing baseline drift and temperature variations, enabling reliable detection in various industrial applications.
Implementation Method 1
a periodic refractive index modulated fiber grating structure within the fiber core
Implementation Method 2
a thermally conductive sensing layer positioned about a portion of the fiber cladding surrounding the periodic refractive index modulated fiber grating structure
Implementation Method 3
a thermally insulated cylindrical gas chamber for maintaining the CO2 purity sensor in an isothermal state
Data Source
AI summary
A carbon dioxide (CO2) purity sensor package includes a fiber core, a periodic refractive index modulated fiber grating structure within the fiber core and a fiber cladding. A thermally conductive sensing layer is positioned about a portion of the fiber cladding surrounding the periodic refractive index modulated fiber grating structure. A gas chamber encloses the fiber cladding with the thermally conductive sensing layer.