Quantifying acetylene mole fraction in rich flat laminar premixed C2H4/air flames using mid-infrared polarization spectroscopy

Wanxia Zhao, Zeyad T. Alwahabi, Bassam Dally

Research output: Contribution to journalArticlepeer-review


Mid-infrared laser polarization spectroscopy (IRPS) has been applied to measure the mole fraction of acetylene in rich premixed laminar C2H4/Air flat flames at equivalence ratios (Φ) of 1.7, 2.1, and 2.3, and under atmospheric pressure. The detection was conducted by probing the ro-vibrational P(19) transition at ~ 3.1 μm. The total collisional broadening coefficient of C2H2 was approximately 0.074 cm−1 atm−1 and varied within a range of 0.5% under different flame conditions, which made the effect of linewidth not obvious in the CH4/air flame. The calculated mole fraction of C2H2, using the Chemkin model, at Φ = 1.3 and 1.5 was used to calibrate the recorded IRPS signal intensities at different Height Above Burner (HAB). A single scaling factor was then used to quantify the measured C2H2 at highly sooting conditions, Φ = 1.7, 2.1, and 2.3, with a Limit of Detection (LoD) of 35 ± 5 ppm. The first observed C2H2 mole fraction appeared at HAB of 3 mm and measured as 2003 ppm, 2217 ppm, and 2495 ppm, for Φ = 1.7, 2.1, and 2.3, respectively. The mole fraction increased as the HAB increased to reach the maximum value of 2296 ppm, 2807 ppm, and 3478 ppm, for Φ = 1.7, 2.1, and 2.3, respectively, up to HAB of 5 mm. It was observed that the C2H2 mole fraction reaches a plateau region at HAB of ~ 8 mm. The production of C2H2 has been observed to be subject to a critical gas temperature of 1400 ± 30 K. The critical soot inception temperature, where the first incepted soot particles are observed, is the same as the gas temperature where χmaxC2H2 was detected, namely at 1500 ± 30 K. These measurements and calibration procedure demonstrate a plausible technique to probe other flames and to better understand soot inception and its correlation with C2H2.
Original languageEnglish (US)
JournalApplied Physics B
Issue number8
StatePublished - Jul 4 2023

Bibliographical note

KAUST Repository Item: Exported on 2023-07-14
Acknowledged KAUST grant number(s): CLTAMP900-1001-PJ-BAS
Acknowledgements: Open Access funding enabled and organized by CAUL and its Member Institutions. The research is funded by King Abdullah University of Science and Technology under grant number CLTAMP900-1001-PJ-BAS. The authors acknowledge the financial support from King Abdullah University of Science and Technology. The authors would like to thank Dr. Et-touhami Es-sebbar and Dr. Earnesto Thachil from the Clean Combustion Research Center, King Abdullah University of Science and Technology, for their technical support.

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physics and Astronomy (miscellaneous)


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