Temperature and water measurements in flames using 1064 nm Laser-Induced Grating Spectroscopy (LIGS)

Francesca De Domenico, Thibault Guiberti, Simone Hochgreb, William L. Roberts, Gaetano Magnotti

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Laser-Induced Grating Spectroscopy (LIGS) is applied to premixed CH4/air laminar flat flames under operating pressures of 1 to 6 bar. For the first time, temperature and water concentration have been acquired simultaneously in a reacting flow environment using LIGS. A 1064 nm pulsed laser is used as pump to generate a temporary stationary intensity grating in the probe volume. Water molecules in the flame products absorb the laser energy and generate a thermal grating if sufficiently high energies are delivered by the laser pulses, here more than 100 mJ per pulse. Such energies allow the electric field to polarize the dielectric medium, resulting in a detectable electrostrictive grating as well. This creates LIGS signals containing both the electrostrictive and the thermal contributions. The local speed of sound is derived from the oscillation frequency of LIGS signals, which can be accurately measured from the single shot power spectrum. Data show that the ratio between the electrostrictive and the thermal peak intensities is an indicator of the local water concentration. The measured values of speed of sound, temperature, and water concentration in the flames examined compare favorably with flame simulations with Chemkin, showing an estimated accuracy of 0.5 to 2.5% and a precision of 1.4–2%. These results confirm the potential for 1064 nm LIGS-based thermometry for high-precision temperature measurements of combustion processes.
Original languageEnglish (US)
Pages (from-to)336-344
Number of pages9
JournalCombustion and Flame
StatePublished - May 3 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST). Francesca De Domenico's internship at KAUST University was fully founded by the KAUST Visiting Students Program. Francesca De Domenico is supported by the Honorary Vice-Chancellor's Award and a Qualcomm/ DTA Studentship (University of Cambridge). The authors are grateful to Dr. Benjamin A. O. Williams and Prof. Paul Ewart for valuable advice, developed under a previous EPSRC project EP/K02924X. The help of Anthony Bennet with the pressure vessel was highly appreciated.


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