Sensitivity, stability, and precision of quantitative Ns-LIBS-based fuel-air-ratio measurements for methane-air flames at 1-11 bar

Paul S. Hsu*, Mark Gragston, Yue Wu, Zhili Zhang, Anil K. Patnaik, Johannes Kiefer, Sukesh Roy, James R. Gord

*Corresponding author for this work

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Nanosecond laser-induced breakdown spectroscopy (ns-LIBS) is employed for quantitative local fuel-air (F/A) ratio (i.e., ratio of actual fuel-to-oxidizer mass over ratio of fuel-to-oxidizer mass at stoichiometry, measurements in well-characterized methane-air flames at pressures of 1-11 bar). We selected nitrogen and hydrogen atomic-emission lines at 568 nm and 656 nm, respectively, to establish a correlation between the line intensities and the F/A ratio. We have investigated the effects of laser-pulse energy, camera gate delay, and pressure on the sensitivity, stability, and precision of the quantitative ns-LIBS F/A ratio measurements. We determined the optimal laser energy and camera gate delay for each pressure condition and found that measurement stability and precision are degraded with an increase in pressure. We have identified primary limitations of the F/A ratio measurement employing ns-LIBS at elevated pressures as instabilities caused by the higher density laser-induced plasma and the presence of the higher level of soot. Potential improvements are suggested. (C) 2016 Optical Society of America

Original languageEnglish
Pages (from-to)8042-8048
Number of pages7
JournalApplied Optics
Volume55
Issue number28
Early online date29 Sep 2016
DOIs
Publication statusPublished - 1 Oct 2016

Keywords

  • INDUCED BREAKDOWN SPECTROSCOPY
  • LASER-INDUCED PLASMA
  • INDUCED SPARK
  • GAS
  • EMISSION
  • IGNITION
  • MIXTURE
  • ENGINE

Cite this

Hsu, P. S., Gragston, M., Wu, Y., Zhang, Z., Patnaik, A. K., Kiefer, J., Roy, S., & Gord, J. R. (2016). Sensitivity, stability, and precision of quantitative Ns-LIBS-based fuel-air-ratio measurements for methane-air flames at 1-11 bar. Applied Optics, 55(28), 8042-8048. https://doi.org/10.1364/AO.55.008042