Successive laser-induced breakdowns in atmospheric pressure air and premixed ethane-air mixtures

Moon Soo Bak, Seong kyun Im, Mark A. Cappelli

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Two successive focused laser pulses are employed to experimentally simulate laser-induced breakdown plasmas at high repetition rates. We find that energy absorption of the second laser pulse by the plasma produced by the first laser pulse is enhanced slightly when the time interval between the pulses is shorter than several tens of nanoseconds but falls to almost zero when the time interval is between a few hundreds of nanoseconds and several tens of microseconds. This behavior is attributed to gas heating by the first breakdown event. In premixed ethane-air mixtures, we identify another strong reduction in the second laser pulse absorption when this pulse coincides with the heat released by combustion, typically milliseconds after the first laser pulse. The fuel-air equivalence ratio (φ) and base flow speed are also varied in this study. The results show that the window of reduced absorption coinciding with heat release due to combustion is narrowed when the base flow speed is increased, and also under fuel lean and fuel rich conditions. These results suggest that the use of pulsed high frequency laser breakdowns for premixed combustion stabilization is optimized when laser pulse repetition rates below a certain frequency (e.g., 500. Hz at the conditions that φ is 1 and the base flow speed is 4.9. m/s) to maximize laser energy coupling and for improved anchoring of the flame base.

Original languageEnglish
Pages (from-to)1744-1751
Number of pages8
JournalCombustion and Flame
Volume161
Issue number7
DOIs
Publication statusPublished - 2014 Jul
Externally publishedYes

Keywords

  • Combustion stabilization
  • Repetitive laser ignition

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Physics and Astronomy(all)

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