Saturation Dependence of Flame Thermometry Using Mid-IR Degenerate Four Wave Mixing

Pedersen, Rasmus L.; Sahlberg, Anna Lena; Hot, Dina; Li, Zhongshan

doi:10.1177/0003702820955186

Cited by 3 publications

(4 citation statements)

References 29 publications

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“…Applications in turbulent flame situations are not possible at this time, because the time resolution is limited by the scanning speed of the DFWM laser system, where scanning over the lines takes a few minutes. It is possible to improve this time resolution by recording the peak intensity of each line instead of scanning the laser, 6 , 31 but it is still necessary to average the intensity of each line over 30 s to reduce the shot-to-shot intensity fluctuations, 6 and for laminar flames the scanning over each line gives a higher precision. 20 It might be possible to achieve better time-resolution in the future by having a laser system where the laser wavelength can be switched between the H 2 O lines from shot-to-shot with higher repetition rate, but at this point the time resolution is limited to ∼1 min per measurement and is therefore applicable only in laminar, quasi-stable flame conditions.…”

Section: Discussionmentioning

confidence: 99%

“…The line strength of each H 2 O line can be measured either by scanning the laser over the two absorption lines or placing the laser on the peak of each absorption line for a short time. The scanning method has been chosen over the on-line approach since the former leads to more reliable measurement results 31 and the scanning method is suitable for the stable laminar flames that were studied here. Equation 4shows that the DFWM signal intensity depends on the degree of excitation saturation.…”

Section: Thermometry Using Degenerate Four-wave Mixingmentioning

confidence: 99%

“…Due to the high sensitivity of the chosen water lines, the DFWM thermometry can potentially achieve very high precision. However, since DFWM thermometry is highly sensitive to the degree of saturation in the flames, 31 this method requires a calibration of the DFWM signal intensity ratios versus quantitative temperatures in known conditions to determine the function between the signal intensity ratio and temperature.…”

Section: Introductionmentioning

confidence: 99%

“…DFWM is more suitable for rich flame thermometry or thermometry in unknown flame conditions since this method does not depend on the flame composition within the measured volume. In previous works, 30 , 31 laser Rayleigh scattering was used to provide temperatures during DFWM calibration with an uncertainty of 7%. To further improve the performance of DFWM thermometry, a method that provides more accurate and precise temperatures is needed during the calibration process.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Temperature and Thermal Diffusivity Diagnostics in Laminar Methane Flames Using Infrared Four-Wave Mixing Techniques

Song,

Chao,

Sahlberg

2024

Appl Spectrosc

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Four-wave mixing techniques, such as coherent anti-Stokes Raman spectroscopy (CARS), laser-induced grating spectroscopy (LIGS), and degenerate four-wave mixing (DFWM), have been widely used in combustion diagnostics due to their advantages of high signal-to-noise ratio (S/N), coherent signal, and spatial resolution. In this work, a nano-second pulsed laser is utilized to generate mid-infrared (near 3 µm) pump beams, exciting the rovibrational transitions of nascent water in flames. Combined LIGS and DFWM measurements are demonstrated in premixed laminar CH4/O2/N2 flames with equivalence ratios from 0.6 to 1.5, to achieve precise thermometry in a wide range of flame conditions. The flame temperatures were also measured by thermocouple as a reference, and the results from LIGS and DFWM align well with the trends shown in the thermocouple measurements. In fuel-lean flames, where the mass-to-specific-heat ratio variation is minimal, LIGS provides temperature data with a precision better than 16 K (0.8%). In fuel-rich flames, where the increased H2 concentration in the flame introduces uncertainty in gas constants thus affecting the accuracy of LIGS thermometry, DFWM is instead employed for temperature measurement since it is less sensitive to the gas composition within the measured volume. The high-precision LIGS temperatures in lean flames serve as temperature reference during the DFWM calibration of the degree of saturation, and a precision better than 90 K (4.5%) is achieved for DFWM thermometry. In addition to temperature, a theoretical model is employed to fit LIGS signal time waveforms, extracting the local speed of sound and thermal diffusivity with precisions better than 0.5% and 1.3%, respectively. These high-precision measurements contribute additional data for flame research and simulation calculations. This way, the combined use of DFWM and LIGS proves the potential for accurate thermometry and diagnostics of other thermodynamic parameters across a wide range of flame conditions.

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Section: Discussionmentioning

confidence: 99%

Section: Thermometry Using Degenerate Four-wave Mixingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Temperature and Thermal Diffusivity Diagnostics in Laminar Methane Flames Using Infrared Four-Wave Mixing Techniques

Song,

Chao,

Sahlberg

2024

Appl Spectrosc

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Third-order nonlinear optical properties of choline chloride based deep eutectic solvents: Theoretical and experimental studies

Ferreira

Ramos‐Ortíz

Vázquez

et al. 2023

Journal of Molecular Liquids

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Characterization of femtosecond laser-induced grating scattering of a continuous-wave laser light in air

Ding

Zheng

et al. 2022

Opt. Express

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Nanosecond laser-induced grating scattering/spectroscopy (LIGS) technique has been widely applied for measuring thermodynamic parameters such as temperature and pressure in gaseous and liquid media. Recently, femtosecond (fs) laser was demonstrated to induce the grating and develop the fs-LIGS technique for gas thermometry. In this work, we systematically investigated the fs-LIGS signal generation using 35 fs, 800 nm laser pulses at 1 kHz repetition rate in ambient air by varying the pump laser energies, the probe laser powers and the temporal delays between two pump laser pulses. The stability of single-shot fs-LIGS signal was studied, from which we observed that the signal intensity exhibits a significant fluctuation while the oscillation frequency shows a much better stability. A 4.5% precision of the oscillation frequency was achieved over 100 single-shot signals. By using a previously-developed empirical model, the fs-LIGS signals were fitted using nonlinear least-squares fitting method, by which crucial time constants characterizing the signal decay process were extracted and their dependences on the pump laser energy were studied. From the measured results and theoretical analysis, we found that the appropriate range of the overall pump laser energy for reliable fs-LIGS measurements is approximately located within 80 ∼ 300 μJ. The limitations on the accuracy and precision of the fs-LIGS measurements, the origin of destructive influence of plasma generation on the signal generation as well as the electrostriction contribution were also discussed. Our investigations could contribute to a better understanding of the fs-LIGS process and further applications of the technique in single-shot gas thermometry and pressure measurements in various harsh conditions.

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Saturation Dependence of Flame Thermometry Using Mid-IR Degenerate Four Wave Mixing

Cited by 3 publications

References 29 publications

Temperature and Thermal Diffusivity Diagnostics in Laminar Methane Flames Using Infrared Four-Wave Mixing Techniques

Temperature and Thermal Diffusivity Diagnostics in Laminar Methane Flames Using Infrared Four-Wave Mixing Techniques

Third-order nonlinear optical properties of choline chloride based deep eutectic solvents: Theoretical and experimental studies

Characterization of femtosecond laser-induced grating scattering of a continuous-wave laser light in air

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