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Two dimensional temperature measurement characteristics in pulverized coal combustion field by computed tomography-tunable diode laser absorption spectroscopy
摘要： Two dimensional temperature and concentration distributions are important parameters for pulverized coal combustion used for power plant to understand the combustion field and develop the high efficient combustion technologies. However, it is difficult to measure two dimensional temperature and concentration in pulverized coal combustion field using conventional measurement technologies because pulverized coal combustion produces lots of dust and strong emission from its flame. This paper focused on the application of two dimensional temperature measurement method based on the combination of computed tomography and tunable diode laser absorption spectroscopy using absorption spectra of water vapor at 1388nm and 1343nm for each laser scanning using direct absorption spectroscopy, which show the better characteristics of spatial-temporal resolution, fast response, high sensitivity, self-calibration and optical accessibility. Accuracy of temperature measurement using tunable diode laser absorption spectroscopy was improved by applying the corrected spectroscopic database. Computed tomography reconstruction accuracy of 16 laser-paths configuration was evaluated using sum of squared difference (0.001) and zero-mean normalized cross-correlation (over 0.991), which presented the consistent temperature between assumed and reconstructed distributions. This developed computed tomography-tunable diode laser absorption spectroscopy was successfully applied to pulverized coal flame for two dimensional temperature measurement with 1 ms temporal resolution for time-series two dimensional temperature measurement in the range of 300K-2500K. The rationality was demonstrated by comparison of pulverized coal flame and Methane-Air flame temperature distributions due to the main heat release produced by methane fuel. Its applicability to pulverized coal combustion field will be benefit for optimal operation control and combustion efficiency improvement by combustion organization or new design of combustion system.
关键词： Power plant,Pulverized coal combustion,Computed tomography (CT),Tunable diode laser absorption spectroscopy (TDLAS),Two dimensional temperature measurement
更新于2025-09-23 15:21:01
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EXPRESS: Influence of Line Pair Selection on Flame Tomography Using Infrared Absorption Spectroscopy
摘要： We report the influence of absorption line selection on the tomographic results for high-temperature flames by numerical and experimental methods. Different combinations of infrared H2O absorption transitions are utilized with the Tikhonov-regularized Abel inversion to reconstruct the radial distribution of temperature and H2O concentration in a flat flame. It is shown that besides using the mathematical algorithm such as regularization, selecting a line pair with a large ΔE″ (> 1390 cm–1) also reduces the reconstruction uncertainty at 300–2000 K. In this study, a proper selection of absorption line pairs reduces the reconstruction uncertainty by 25% at the same level of noise. The line pair of H2O transitions at 4029.524 cm–1 and 4030.729 cm–1 is recommended for the tomography of high-temperature flames at 1000–3000 K, whereas the line pair of 7185.597 cm–1 and 7444.352 cm–1 can be used at 300–1000 K.
关键词： tunable diode laser absorption spectroscopy,TDLAS,Tomography,high-temperature flame,line selection
更新于2025-09-23 15:21:01
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Gas distribution mapping for indoor environments based on laser absorption spectroscopy: Development of an improved tomographic algorithm
摘要： Gas distribution mapping (GDM) is an important technology for the study of indoor environment, which can be used to evaluate the efficiency of environmental control system and identify pollutant sources. Most recent studies have implemented GDM through contact sensors or a sensor network, which is difficult to calibrate all the sensors and cover the whole space. In this study, we introduced the non-contact tunable diode laser absorption spectroscopy (TDLAS) technology for GDM in the indoor environment. An improved tomographic algorithm, namely Least Square with Tikhonov Regularization (LSTR), was proposed and compared with two available tomographic algorithms using four validated computational fluid dynamics (CFD) simulations. We also analyzed the effects of the laser emitter placements and optical path densities on the concentration field reconstruction quantitatively. The results showed that the LSTR method could reduce the average relative root mean square error (RRMSE) of tomography by 52%, and the laser emitter at the long edge middle (LEM) can achieve better tomographic performance. The degree of the concentration dispersion from the source would mainly impact the tomographic results: when the sector dispersion (SD) value of concentration distribution was about 2.3 times larger, the average RRMSE value would be decreased by about 40%. The intersection matrix with a higher path density achieved a more accurately reconstructed map due to its lower condition number. In addition, the optical path density was suggested to twice the number of grid cells considering the trade-off between scanning time and accuracy.
关键词： Non-contact sensing,Tunable diode laser absorption spectroscopy (TDLAS),Concentration measurement,Indoor air,Air pollution
更新于2025-09-23 15:19:57
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Evaluation of Dry-Wet Transition in PEFC Under Load Changes Based on Laser Spectroscopy Using Fiber-Optic Probe
摘要： To avoid the membrane dryout and performance degradation of polymer electrolyte fuel cells (PEFCs) under low-humidity conditions, it is necessary to understand the dynamic water transport within working cells. In this study, we have developed a real-time gas sensing system with a single-ended fiber-optic probe based on tunable diode laser absorption spectroscopy (TDLAS), to measure the water vapor distribution in narrow channels of fuel cells with high accuracy and high temporal resolution. This sensor was used to evaluate the dry-wet transient phenomena in the anode flow channel of a PEFC during low-humidity and load change operations. The technique showed the water vapor concentration in the anode channel has a large temporary drop when the current density increases and the voltage undershoot occurs. We concluded that the TDLAS-based gas sensing technique enables the detection of instantaneous fluctuations of water concentration in the flow channel observed after step changes of current density.
关键词： load changes,fiber-optic probe,dry-wet transition,PEFC,TDLAS
更新于2025-09-23 15:19:57
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Pulverized coal combustion application of laser-based temperature sensing system using computed tomography a?? Tunable diode laser absorption spectroscopy (CT-TDLAS)
摘要： The investigation of combustion phenomena in pulverized coal flames is significant for combustion optimization related to energy conservation and emission reduction. Real-time two dimensional (2D) temperature and concentration distributions play an important role for combustion analysis. The non-contact and fast response 2D temperature and concentration distribution measurement method was developed in this study. The method is based on a combination of computed tomography (CT) and tunable diode laser absorption spectroscopy (TDLAS). The accuracy evaluation of developed 32-path CT-TDLAS demonstrated its feasibility of 2D temperature measurement. 32-path CT-TDLAS was applied to CH4 and 5 kg/h coal combustion fields for 2D temperature measurement. The time-series 2D temperature distribution in coal combustion furnace was measured using 32-path CT-TDLAS measurement cell with kHz time resolution. The transient temperature field of combustion flame directly reflects the combustion mode and combustion stability. The measurement results demonstrate its applicability of CT-TDLAS to various types of combustor, especially the combustion fields with coal and ash particles. CT-TDLAS method with kHz response time enables the real-time 2D temperature measurement to be applicable for combustion analysis.
关键词： 2D temperature measurement,Computed tomography (CT),Tunable diode laser absorption spectroscopy (TDLAS),Time-series distribution,Coal combustion
更新于2025-09-23 15:19:57
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Application of the least square method for processing the signal obtained by the tuneable diode laser absorption spectroscopy method in the range 4860a??4880a??cm <sup>a??1</sup> for the problem of measuring <sup>13</sup> CO <sub/>2</sub> content in exhaled air
摘要： The 1st, 2nd and 3rd order least square method (LSM-1, LSM-2 and LSM-3) is applied to smooth the experimental absorption signal of 13CO2 and 12CO2 obtained by the tuneable diode laser absorption spectroscopy method in the 4860–4880 cm?1 frequency range of a tuneable diode laser. It has been shown clearly that using LSM-2 with a filter window N ~ 100 allows the 13CO2 content in exhaled air to be measured at an error level of 0.28%, which meets breathing tests requirements.
关键词： gas analysis,biomedical analysis,carbon dioxide,tuneable diode laser absorption spectroscopy (TDLAS)
更新于2025-09-19 17:13:59
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Near-infrared tunable diode laser absorption spectroscopy-based determination of carbon dioxide in human exhaled breath
摘要： A spectroscopic detection system for the accurate monitoring of carbon dioxide (CO2) in exhaled breath was realized by tunable diode laser absorption spectroscopy (TDLAS) in conjunction with a vertical-cavity surface-emitting laser (VCSEL) and a multipass cell with an effective optical path-length of 20 m. The VCSEL diode emitting light with an output power of 0.8 mW, covered the strong absorption line of CO2 at 6330.82 cm?1 by drive-current tuning. The minimum detectable concentration of 0.769% for CO2 detection was obtained, and a measurement precision of approximately 100 ppm was achieved with an integration time of 168 s. Real-time online measurements were carried out for the detection of CO2 expirograms from healthy subjects, different concentrations were obtained in dead space and alveolar gas. The exhaled CO2 increased significantly with the increasing physical activity, reaches its maximal value at the beginning of respiratory compensation and then decreased slightly until maximal exercise. The developed measurement system has a great potential to be applied in practice for the detection of pulmonary diseases associated with CO2 retention.
关键词： CO2,human health monitoring,Tunable diode laser absorption spectroscopy,carbon dioxide,VCSEL,exhaled breath,TDLAS,vertical-cavity surface-emitting laser
更新于2025-09-16 10:30:52
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EXPRESS: Two-Dimensional Temperature Measurement in a High Temperature and Pressure Combustor Using Computed Tomography Tunable Diode Laser Absorption Spectroscopy (CT-TDLAS) with a Wide-Scanning Laser at 1335–1375 nm
摘要： Tunable diode laser absorption spectroscopy (TDLAS) technology is a developing method for temperature and species concentration measurements with the features of non-contact, high precision, high sensitivity, etc. The difficulty of two-dimensional (2D) temperature measurement in actual combustors has not yet been solved because of pressure broadening of absorption spectra, optical accessibility, etc. In this study, the combination of computed tomography (CT) and TDLAS with a wide scanning laser at 1335–1375 nm has been applied to a combustor for 2D temperature measurement in high temperature of 300–2000 K and high pressure of 0.1–2.5 MPa condition. An external cavity type laser diode with wide wavelength range scanning at 1335–1375 nm was used to evaluate the broadened H2O absorption spectra due to the high temperature and high pressure effect. The spectroscopic database in high temperature of 300–2000 K and high pressure of 0.1–5.0 MPa condition has been revised to improve the accuracy for temperature quantitative analysis. CT reconstruction accuracy was also evaluated in different cases, which presented the consistent temperature distribution between CT reconstruction and assumed distributions. The spatial and temporal distributions of temperature in the high temperature and high pressure combustor were measured successfully by CT-TDLAS using the revised spectroscopic database.
关键词： high temperature and high pressure field,TDLAS,computed tomography,2D,Two-dimensional temperature measurement,combustion,CT,tunable diode laser absorption spectroscopy
更新于2025-09-12 10:27:22
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Hydrogen Sensor Based on Tunable Diode Laser Absorption Spectroscopy
摘要： A laser-based hydrogen (H2) sensor using wavelength modulation spectroscopy (WMS) was developed for the contactless measurement of molecular hydrogen. The sensor uses a distributed feedback (DFB) laser to target the H2 quadrupole absorption line at 2121.8 nm. The H2 absorption line exhibited weak collisional broadening and strong collisional narrowing effects. Both effects were investigated by comparing measurements of the absorption linewidth with detailed models using different line profiles including collisional narrowing effects. The collisional broadening and narrowing parameters were determined for pure hydrogen as well as for hydrogen in nitrogen and air. The performance of the sensor was evaluated and the sensor applicability for H2 measurement in a range of 0–10 %v of H2 was demonstrated. A precision of 0.02 %v was achieved with 1 m of absorption pathlength (0.02 %v·m) and 1 s of integration time. For the optimum averaging time of 20 s, precision of 0.005 %v·m was achieved. A good linear relationship between H2 concentration and sensor response was observed. A simple and robust transmitter–receiver configuration of the sensor allows in situ installation in harsh industrial environments.
关键词： laser spectroscopy,WMS,diode laser,TDLAS,absorption spectroscopy,hydrogen sensor,hydrogen,gas sensor
更新于2025-09-11 14:15:04
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Towards Customized Spatial Resolution in TDLAS Tomography and Hugh McCann
摘要： Tunable diode laser absorption spectroscopy (TDLAS) tomography has been widely employed to spatially and temporally resolve gas parameters in combustion processes. The requirements placed on the spatial resolution of a tomographic image vary in industrial applications, depending on the size of the target field and the necessity to detect small features. Based on an optimized beam arrangement, this work proposes a scheme to customize the spatial resolution in the design of TDLAS tomography systems. To the best of our knowledge, the proposed scheme, for the first time, quantifies the impact on the spatial resolution of varying the number of samples of the imaging space, in both angular and linear dimensions. More importantly, the proposed scheme can be used to determine the most effective optical layout that would achieve a desired spatial resolution. The reduction in the system complexity will enable the sensor to be installed in practical combustors while maintaining reliability. Finally, we apply the proposed scheme in a case study based on experimental data previously acquired from an automotive engine.
关键词： tunable diode laser absorption spectroscopy (TDLAS),spatial resolution,combustion diagnosis,tomography,beam arrangement
更新于2025-09-11 14:15:04