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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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The Chicago Water Isotope Spectrometer (ChiWIS-lab): A tunable diode laser spectrometer for chamber-based measurements of water vapor isotopic evolution during cirrus formation
摘要： We describe a new tunable diode laser (TDL) absorption instrument, the Chicago Water Isotope Spectrometer, designed for measurements of vapor-phase water isotopologues in conditions characteristic of the upper troposphere [190–235 K temperature and 2–500 parts per million volume (ppmv) water vapor]. The instrument is primarily targeted for measuring the evolving ratio of HDO/H2O during experiments in the “Aerosol Interaction and Dynamics in the Atmosphere” (AIDA) cloud chamber. The spectrometer scans absorption lines of both H2O and HDO near the 2.64 μm wavelength in a single current sweep, increasing the accuracy of isotopic ratio measurements. At AIDA, the instrument is configured with a 256-m path length White cell for in situ measurements, and effective sensitivity can be augmented by enhancing the HDO content of chamber water vapor by an order of magnitude. The instrument has participated to date in the 2012–2013 IsoCloud campaigns studying isotopic partitioning during the formation of cirrus clouds and in the AquaVIT-II instrument intercomparison campaign. Realized precisions for 1-s measurements during these campaigns were 22 ppbv for H2O and 16 ppbv for HDO, equivalent to relative precisions of less than 0.5% for each species at 8 ppmv water vapor. The 1-s precision of the [HDO]/[H2O] ratio measurement ranged from 1.6‰ to 5.6‰ over the range of experimental conditions. H2O measurements showed agreement with calculated saturation vapor pressure to within 1% in conditions of sublimating ice and agreement with other AIDA instruments (the AIDA SP-APicT reference TDL instrument and an MBW 373LX chilled mirror hygrometer) to within 2.5% and 3.8%, respectively, over conditions suitable for all instruments (temperatures from 204 K to 234 K and H2O content equivalent to 15–700 ppmv at 200 hPa).
关键词： upper troposphere,isotopic ratio measurements,water isotopologues,AIDA cloud chamber,tunable diode laser
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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Experimental observation of the vibration-rotation radiation curves of <sup>12</sup> C <sup>16</sup> O <sub/>2</sub> and <sup>13</sup> C <sup>16</sup> O <sub/>2</sub> absorption constants ranging from 4860 to 4880 sm <sup>a??1</sup> by the tunable diode laser absorption spectroscopy method
摘要： We report the experimental observation of the absorption constant values of 12C16O2 and 13C16O2 using the tunable diode laser absorption spectroscopy method ranging from 4860 to 4880 sm?1 within the pressure limits of 8–240 mbar for the absorption curves (lines) R(18), R(20), R(22), R(24), R(26), R(28), R(30), R(32), R(34) and R(36) of the 20013–00001 molecule 12C16O2 vibration band, and within the pressure limits of 0.06–1.7 mbar for the absorption curves P(10), P(12), P(14), P(16), P(18), P(20) and P(22) of the 20012–00001 molecule 13C16O2 vibration band. In the work, as a mixture under analysis, a mixture of the isotopes 13C16O2 and 12C16O2 at the ratio of 1:140 was used. The results have been compared with the data of the HITRAN spectroscopic database.
关键词： tunable diode laser absorption spectroscopy,carbon dioxide,absorption coefficients
更新于2025-09-23 15:19:57
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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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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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Spectral Line Shape Analysis Using Hartmann-Tran Profile for Tunable Diode Laser Absorption Spectroscopy of Water Vapor at 1.39a????m
摘要： In this study, spectral line shape analysis was conducted for water vapor absorption at 1.39 μm with a Hartmann-Tran pro?le (HTP), which is capable of being ef?ciently and accurately reduced to (speed dependent) Voigt and (speed dependent) Rautian pro?les. The near-IR absorption lines of water vapor were measured using tunable diode laser absorption spectroscopy (TDLAS). The spectrum ?tting code was home-written based on the Trust region re?ective algorithm and the HTP. Voigt pro?le (VP), Rautian pro?le (RP), speed-dependent VP (SDVP), and speed-dependent Rautian pro?le (SDRP), which were reduced from the HTP, were used as model functions to test the validity of the near-IR absorption lines of water vapor in terms of line shape pro?le. With the SDVP, the standard deviation of the ?tting residuals was at a 10?3 level relative to the most intense peak height in a range of 1.39 μm at 2.5 Torr and room temperature, while the global standard deviation was less than 0.5 × 10?3, thus showing the best result among them. This suggests the need to consider the speed-dependent collision width in the self-broadening of water vapor.
关键词： Tunable diode laser absorption spectroscopy,Hartmann-Tran pro?le,Spectral lineshape analysis,Water vapor
更新于2025-09-23 15:19:57
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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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Development of a near-infrared tunable diode laser absorption spectrometer for trace moisture measurements in helium gas
摘要： There is a demand for water vapor or moisture measurement in gas mixture at trace level from industries like combustion studies, semi-conductor industry, environmental studies, cryogenic services, etc. There are few principles, direct or indirect, to measure moisture—each having individual limitations. Among all, the chilled mirror hygrometer is very accurate but response time is poor; therefore, it is suitable for calibration purposes not for online measurement. An instrument based on near-infrared absorption spectroscopy has been developed and discussed in this article. In this instrument, the laser is modulated with both sinusoidal and slower linear scan, split into two beams: an intense one is passed only through air and the other one through air and the absorption cell of 50 cm length. The balanced detection technique is adopted between the two beams called the reference and the measurement channels, respectively, and the difference signal between the two undergoes the 2-f lock-in detection. This method is good for elimination of moisture present in air and any common-mode noise present in both the channels and as well determines the splitting ratio keeping the absorption cell in vacuum. This method also eliminates the 1-f component present in the signal, which causes asymmetry in the two wings of the 2-f absorption spectra. For computation of absorption spectra, it is found that the Hitran database is sufficient to predict for air as the base gas but Exomol should be used in the cases where helium is the base gas. Simulation and experiment both were performed at different concentration and pressures and the results are found in good agreement for the central spectrum with little difference in wings’ peak. The sensitivity of this instrument achieved at 100 mb pressure in the absorption cell for helium as the base gas with refresh rate of 625 Hz is ～17 ppmv and ～4 ppmv for direct and 2-f measurement, respectively. The applicability of the instrument for air as the base gas is also shown in the paper.
关键词： trace moisture measurements,near-infrared,tunable diode laser absorption spectrometer,helium gas
更新于2025-09-12 10:27:22