Cavity-enhanced absorption sensor for carbon monoxide in a rapid compression machine

Ehson Fawad Nasir, Aamir Farooq

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


A sensor based on cavity-enhanced absorption spectroscopy (CEAS) was implemented for the first time in a rapid compression machine (RCM) for carbon monoxide concentration measurements. The sensor consisted of a pulsed quantum cascade laser (QCL) coupled to a low-finesse cavity in the RCM using an off-axis alignment. The QCL was tuned near 4.89μm to probe the P(23) ro-vibrational line of CO. The pulsed mode operation resulted in rapid frequency down-chirp (6.52 cm-1/μs) within the pulse as well as a high time resolution (10 μs). The combination of rapid frequency down-chirp and off-axis cavity alignment enabled a near complete suppression of the cavity coupling noise. A CEAS gain factor of 133 was demonstrated in experiments, resulting in a much lower noise-equivalent detection limit than a single-pass arrangement. The sensor thus presents many opportunities for measuring CO formation at low temperatures and for studying kinetics using dilute reactive environments; one such application is demonstrated in this work using dilute n-heptane/air mixtures in the RCM. The formation of CO during first-stage ignition of n-heptane was measured over 802-899K at a nominal pressure of 10bar. These conditions correspond to the NTC region of n-heptane and such results provide useful metrics to test and compare the predictions of low-temperature heat release by different kinetic models.
Original languageEnglish (US)
Pages (from-to)1297-1304
Number of pages8
JournalProceedings of the Combustion Institute
Issue number2
StatePublished - Dec 14 2018

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): BAS/1/1300-01-01
Acknowledgements: Research reported in this publication was supported by funding from the Office of Sponsored Research at King Abdullah University of Science and Technology (KAUST) (BAS/1/1300-01-01).


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