• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.25-25
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• 2010

The spectroscopy over a region from 3 to 17 ${\mu}m$ based on the tuneable diode lasers (TDLAS) is the most powerful technique for in situ studies of the diagnostics of small molecules. The increasing interest in small molecules especially containing carbon, oxygen, hydrogen, and fluorine containing ones can be fulfilled by TDLAS at 0.0001 cm-1 resolution, because most of these compounds are infrared active. TDLAS provides a means of determining the absolute concentrations of the ground states of stable and transient molecular species, which can be employed for the time dependent studies in sub micro second scale. Information about gas temperature and population densities can also be derived from TDLAS measurements. Collisional energy transfer between the small molecules can be studied with TDLAS. Also, a variety of free radicals and molecular ions have been detected by TDLAS. Since plasmas with molecular feed gases are used in many applications, there are new applications in industrial field. Recently, the development of quantum cascade lasers (QCLs) offers an attractive new option for TDLAS.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.773-782
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• 2016

The performance of the CT-TDLAS (computed tomography-tunable diode laser absorption spectroscopy) is strongly dependent upon the line broadening functions. The line of the laser beam used in the TDLAS is scattered by the natural broadening, the collisional broadening and the doppler broadening. The influence of the natural broadening to the experimental spectra obtained in the TDLAS is negligible. The influences of the collisional broadening and the doppler broadening to the experimental spectra are relatively large, in high pressure gas flows and in high temperature low pressure gas flows, respectively. In this study, optimal coefficients are proposed for the doppler broadening function by using the experimental data obtained in a flat burner test. The optimal coefficients were ${\gamma}_j=0.16$ and n=0.37. Using these coefficients, the temperature and concentration distributions at the engine exhaust gas pipe have been calculated showing their validities.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.1
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• pp.97-104
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• 2018

3-dimensional temperature distribution of the exhaust gas of a fire flame of LPG have been measured by the constructed CT-TDLAS system. 3-Dimensional temperature distributions are measured by 2 layers of CT-TDLAS. Each layer has $8{\times}8$ laser beams implying the temperatures of 64 meshes are measured. SMART algorithm has been adopted for reconstructing the absorption coefficients on the meshes. The line strengths at 6 representative wave lengths of $H_2O$ have been used for obtaining the absorption spectra of the exhaust gas. The temperature distributions measured by the constructed CT-TDLAS have been compared with those by the thermocouples. The relative errors measured between by thermocouple and CT-TDLAS were 13% in average and 33% at maximum. The similarity of temperature distribution between by thermocouples and by CT-TDLAS has been shown at the lower layer than the upper layer implying an unstability of combustions.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.3
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• pp.318-327
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• 2016

In order to improve the performance of temperature field measurements by CT-TDLAS (Computer Tomography Tunable Diode Laser Absorption Spectroscopy), a new reconstruction algorithm, named two-ratios-of-three-peaks method is proposed in this paper. Further, two methods for selecting appropriate initial values of the iterative calculation of CT-TDLAS are proposed. One is MLOS (multiplicative line of sight) method and the other one is ALOS (additive line of sight) method. Two-ratios-of-three-peaks (2R3P) algorithm combined with MART (multiplicative algebraic reconstruction technique) is finally developed for the enhancements of reconstructive calculations. The results have been compared with those obtained by the conventional one-ratio-of-two-peaks (1R2P) algorithm. In order to evaluate the performance of this algorithm, numerical test has been performed using phantom Gaussian temperature distributions with $11{\times}11$ square mesh. The performance of the constructed algorithm has been demonstrated by comparing the results obtained in actual burner experiments with those obtained by thermocouples. It has been verified that 2R3P algorithm with MART and MLOS showed best performance than that of 1R2P algorithm.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.27-28
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• 2012

Tunable diode laser absorption spectroscopy(TDLAS) measurement techniques for several gases densities and temperatures have been applied in industrial combustion systems. Accurate measurement of temperature profile is very important, especially in power plants and heating furnaces. So profile fitting and temperature binning methods are new issue for accurate measurement of temperature in laser gas sensing. Temperature binning method is applied in this study for the measurement of temperature profile using tube furnace with three temperature zones. In this study the temperature profiles of tube furnace is accurately measured within 5% error, and this technique is proved to be very promising in the field of temperature profile measurement.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.202-203
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• 2003

여러 가지 원소의 동위원소 성분 분석은 생물학, 화학, 환경학, 연대학, 기후학 연구에 있어서 중요한 정보를 제공하는 유용한 수단이다. 동위원소 성분비를 측정하는 방법으로는 가스 동위원소 질량분석기를 이용한 방법이 사용되어 왔지만, 최근 다이오드 레이저의 발달과 함께 다이오드레이저 흡수분광법(TDLAS)이 개발되어 사용되고 있다. TDLAS 방법의 경우 질량분석기를 이용하는 방법에서는 측정이 불가능한 동일질량 분자의 동위원소 성분비를 측정할 수 있다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.247-248
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• 2003

Tunable diode laser absorption spectroscopy (TDLAS) has been widely used in environmental monitoring of gaseous species in the past decade. TDLAS is a direct measurement technique for pollutants such as NOx without any interference from other species. Because of its superior spectral purity (～0.001 ­$cm^{-1}$), absorption linewidths with resolvable rotational structure can be studied in the mid infrared region where strong fundamental vibrational transitions of molecules appear. (omitted)

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.127-134
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• 2016

Most of reconstruction algorithms for the calculation of temperature distributions in CT (computed tomography)-TDLAS (tunable diode laser absorption spectroscopy) are based upon two-line thermometry method. This method gives unstable calculation convergence due to signal noise, bias error, and signal mis-matches. In this study, a new reconstruction algorithm based on cross-correlation for temperature calculation is proposed. The patterns of the optical signals at all wave lengths were used to reconstruct the temperature distribution. Numerical test has been made using phantom temperature distributions. Using these phantom temperature data, absorption spectra for all wave lengths were constructed, and these spectra were regarded as the signals that would be obtained in an actual experiments. Using these virtually generated experimental signals, temperature distribution was once again reconstructed, and was compared with those of the original phantom data. Calculation errors obtained by the newly proposed algorithm were slightly large at high temperatures with small errors at low temperature.

• Clean Technology
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• v.25 no.4
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• pp.316-323
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• 2019

In order to enhance combustion efficiency and reduce atmosphere pollutants, it is essential to measure carbon monoxide (CO) concentration precisely in combustion exhaust. CO is the important gas species regarding pollutant emission and incomplete combustion because it can trade off with NOx and increase rapidly when incomplete combustion occurs. In the case of a steel annealing system, CO is generated intentionally to maintain the deoxidation atmosphere. However, it is difficult to measure the CO concentration in a combustion environment in real-time, because of unsteady combustion reactions and harsh environment. Tunable Diode Laser Absorption Spectroscopy (TDLAS), which is an optical measurement method, is highly attractive for measuring the concentration of certain gas species, temperature, velocity, and pressure in a combustion environment. TDLAS has several advantages such as sensitive, non-invasive, and fast response, and in-situ measurement capability. In this study, a combustion system is designed to control the equivalence ratio. Also, the combustion exhaust gases are produced in a Liquefied Petroleum Gas (LPG)/air flame. Measurement of CO concentration according to the change of equivalence ratio is confirmed through TDLAS method and compared with the simulation based on Voigt function. In order to measure the CO concentration without interference from other combustion products, a near-infrared laser at 4300.6 cm^-1 was selected.

• Journal of the Korean Institute of Gas
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• v.24 no.5
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• pp.29-38
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• 2020

It is practically difficult to accurately measure the temperature and concentration of a large combustion systems at industrial sites in real time. Temperature measurement using thermocouple, which are mainly used, is a point-measuring method that is less accurate and less reliable to analyze the wide area range of inner combustion system, and has limitations to internal accessibility. In terms of concentration analysis, most measurement methods use sampling method, which are limited by the difficulty of real-time measurement. As a way to overcome these limitations, laser-based measurement methods have been developed continuously. Laser-based measurement are line-average measurement methods with high representation and precision, which are beneficial for the application of large combustion systems. In this study the temperature and concentration were measured in real time by water vapor and oxygen generated during combustion using Tunable Diode Laser Absorption Spectroscopy (TDLAS). The results showed that the average temperature inside the combustion system was 1330℃ and the mean oxygen concentration was 3.3 %, which showed similar tendency with plant monitoring data.