Flame propagation enhancement by plasma excitation of oxygen. Part II: Effects of O{sub 2}(a{sup 1}{delta}{sub g})

Journal Article · Fri Oct 15 00:00:00 EDT 2010 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2010.02.004· OSTI ID:21350369

Ombrello, Timothy; Won, Sang Hee; Ju, Yiguang ^[1]; Williams, Skip ^[2]

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1. Department of Mechanical and Aerospace Engineering, Engineering Quadrangle, Olden Street, Princeton, NJ 08544 (United States)
2. Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson AFB, OH 45433 (United States)

The isolated effect of O{sub 2}(a{sup 1}{delta}{sub g}) on the propagation of C{sub 2}H{sub 4} lifted flames was studied at reduced pressures (3.61 kPa and 6.73 kPa). The O{sub 2}(a{sup 1}{delta}{sub g}) was produced in a microwave discharge plasma and was isolated from O and O{sub 3} by NO addition to the plasma afterglow in a flow residence time on the order of 1 s. The concentrations of O{sub 2}(a{sup 1}{delta}{sub g}) and O{sub 3} 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 O{sub 2}(a{sup 1}{delta}{sub g}) enhanced the propagation speed of C{sub 2}H{sub 4} lifted flames. Comparison with the results of enhancement by O{sub 3} found in part I of this investigation provided an estimation of 2-3% of flame speed enhancement for 5500 ppm of O{sub 2}(a{sup 1}{delta}{sub g}) addition from the plasma. Numerical simulation results using the current kinetic model of O{sub 2}(a{sup 1}{delta}{sub g}) over-predicts the flame propagation enhancement found in the experiments. However, the inclusion of collisional quenching rate estimations of O{sub 2}(a{sup 1}{delta}{sub g}) by C{sub 2}H{sub 4} mitigated the over-prediction. The present isolated experimental results of the enhancement of a hydrocarbon fueled flame by O{sub 2}(a{sup 1}{delta}{sub g}), along with kinetic modeling results suggest that further studies of C{sub n}H{sub m} + O{sub 2}(a{sup 1}{delta}{sub g}) collisional and reactive quenching are required in order to correctly predict combustion enhancement by O{sub 2}(a{sup 1}{delta}{sub g}). The present experimental results will have a direct impact on the development of elementary reaction rates with O{sub 2}(a{sup 1}{delta}{sub g}) at flame conditions to establish detailed plasma-flame kinetic mechanisms. (author)

• OSTI ID: 21350369
• Journal Information: Combustion and Flame, Vol. 157, Issue 10; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ETHYLENE
OXYGEN
FLAMES
PLASMA
COMBUSTION
COMPUTERIZED SIMULATION
FLAME PROPAGATION
NITRIC OXIDE
EXCITATION
OZONE
VELOCITY
COMPARATIVE EVALUATIONS
HIGH-FREQUENCY DISCHARGES
COMBUSTION KINETICS
AFTERGLOW
PRESSURE RANGE KILO PA
Plasma-assisted combustion
Lifted flames
Tribrachial flames