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Absorption Spectroscopy and Its Implementation
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
Because of the narrow bandwidth and normally wide tenability, external-cavity DLs (ECDLs; see Chapter 5.1) have come to great prominence over recent years. Wavelengths being utilized in experiments range from the deep UV (then including nonlinear conversion techniques as well) to the FIR (e.g., lead-salt DLs); a few examples have been given earlier in this chapter. In particular, for quantitative gas analysis and process control, these laser sources have gained wide acceptance, specifically in the form of TDL absorption spectroscopy (TDLAS); this will be discussed in more detail in Chapter 8.3.
Hybrid Simulated Annealing Particle Swarm Optimization Support Vector Machine Based Temperature-Pressure Error Compensation Approach for TDLAS Gas Detection
Published in Combustion Science and Technology, 2023
Weifeng Wang, Hanfei Liu, Gaoming Wei, Ce Liang, Xiaowei Zhai, Bo Yang, Lifeng Ren, Gaoshuang Li
The original measurement has a serious nonlinear drift of temperature and pressure under the condition of different gas concentrations. The correction of the nonlinear drift problem is essential to pull the actual measured value back (regression) to the real one. Therefore, this paper provides a solution to the measurement output regression problem. TDLAS technique acquires the concentration according to the selective absorption characteristics of analytical light from the to-be-detected gas and eliminates the interference of the non-to-be-detected gas spectrum by making use of the high resolution of the characteristic absorption spectrum. The absorption attenuation degree of infrared spectral intensity by gas molecules is correlated with the optical path length and the concentration of light passing through the target gas. This principle can be described by the Lambert-Beer absorption law (Deng et al. 2022), which is:
Characterization of the Buoyant Jet above a Catalytic Combustor Using Wavelength Modulation Spectroscopy
Published in Combustion Science and Technology, 2019
Torrey R. S. Hayden, Nicholas T. Wimer, Caelan Lapointe, Jason D. Christopher, Siddharth P. Nigam, Aniruddha Upadhye, Mark Strobel, Peter E. Hamlington, Gregory B. Rieker
Laser absorption spectroscopy is an excellent option to achieve these objectives in a heated, buoyant jet because it is quantitative, species-selective, robust and portable, and can provide millisecond time resolution (Lackner, 2011). Other laser-based techniques, such as laser-induced fluorescence (LIF) and Raman or Rayleigh scattering, can provide the desired quantitative spatial and temporal information (Daily, 1997; Mcenally et al., 2000); however, they can require large optical experimental systems that are impractical for industrial applications. Absorption spectroscopy measures the fraction of light absorbed by a gas sample as a function of wavelength. Light will be absorbed if the wavelength is resonant with a quantum transition of a target molecular species. One form of absorption spectroscopy is tunable diode-laser absorption spectroscopy (TDLAS), in which the wavelength of a diode laser is tuned across one or two transitions of the target species. TDLAS provides quantitative, non-intrusive, line-of-sight-averaged measurements of the thermodynamic properties of the gas, and thus has been used extensively in combustion research.
Determination of methane during anaerobic digestion by tunable diode laser absorption spectroscopy (TDLAS)
Published in Instrumentation Science & Technology, 2023
Haibin Cui, Fei Wang, Shengyu Hu, Wenyuan Wang, Jinhui Fan
TDLAS (tunable diode laser absorption spectroscopy) is a promising alternative optical method for gas detection. TDLAS plays an essential role in gas analysis because of the high selectivity, sensitivity, and real-time measurements, which has prompted industrial and environmental applications.[14–17] Because of its line-of-sight character, this technique provides more representative results for the surveillance of large volumes.