Flame propagation enhancement by plasma excitation of oxygen. Part II: Effects of O2(a1Δg)

T. Ombrello, Sang Hee Won, Yiguang Ju, S. Williams

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185 Scopus citations

Abstract

The isolated effect of O2(a1Δg) on the propagation of C2H4 lifted flames was studied at reduced pressures (3.61kPa and 6.73kPa). The O2(a1Δg) was produced in a microwave discharge plasma and was isolated from O and O3 by NO addition to the plasma afterglow in a flow residence time on the order of 1s. The concentrations of O2(a1Δg) and O3 were measured quantitatively through absorption by sensitive off-axis integrated-cavity-output spectroscopy and one-pass line-of-sight absorption, respectively. Under these conditions, it was found that O2(a1Δg) enhanced the propagation speed of C2H4 lifted flames. Comparison with the results of enhancement by O3 found in part I of this investigation provided an estimation of 2-3% of flame speed enhancement for 5500ppm of O2(a1Δg) addition from the plasma. Numerical simulation results using the current kinetic model of O2(a1Δg) over-predicts the flame propagation enhancement found in the experiments. However, the inclusion of collisional quenching rate estimations of O2(a1Δg) by C2H4 mitigated the over-prediction. The present isolated experimental results of the enhancement of a hydrocarbon fueled flame by O2(a1Δg), along with kinetic modeling results suggest that further studies of CnHm+O2(a1Δg) collisional and reactive quenching are required in order to correctly predict combustion enhancement by O2(a1Δg). The present experimental results will have a direct impact on the development of elementary reaction rates with O2(a1Δg) at flame conditions to establish detailed plasma-flame kinetic mechanisms.

Original languageEnglish (US)
Pages (from-to)1916-1928
Number of pages13
JournalCombustion and Flame
Volume157
Issue number10
DOIs
StatePublished - Oct 2010

All Science Journal Classification (ASJC) codes

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

Keywords

  • Flame propagation enhancement
  • Flame speed enhancement
  • Lifted flame
  • Plasma-assisted combustion
  • Singlet delta oxygen
  • Tribrachial flame

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