Repetitively pulsed nanosecond discharge plasma decay in propane–oxygen gas mixture in the presence of a heating electric field

Journal Article · Tue Aug 03 00:00:00 EDT 2021 · Combustion and Flame

DOI:https://doi.org/10.1016/j.combustflame.2021.111611· OSTI ID:1976988

Popov, M. A. ^[1]; Kochetov, I. V. ^[2]; Starikovskiy, A. Y. ^[3]; Aleksandrov, N. L. ^[1]

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1. Moscow Institute of Physics and Technology, Dolgoprudny (Russia)
2. Troitsk Institute of Innovation and Fusion Research, Moscow (Russia); Lebedev Physical Institute RAS. Moscow (Russia)
3. Princeton University, NJ (United States)

Plasma decay in the afterglow of a repetitively pulsed nanosecond discharge in a stoichiometric propane–oxygen mixture was experimentally investigated when a weak heating DC electric field was applied and in its absence. The discharge was ignited at room gas temperature and a pressure of 1–2 Torr and was characterized by low specific energy inputs (<0.004 eV per molecule in one pulse). Using microwave interferometry, the temporal evolution of the electron density during plasma decay was studied, and the effective recombination coefficients were obtained from data processing. It was shown that the rate of plasma decay behaved in a non-monotonic manner with increasing degree of propane oxidation; at first the decay rate grew, then passed through a maximum, fell and saturated in the limit of a large (~2000) number of pulses. In this limit, the effect of the heating DC electric field on the plasma decay decreased with approaching chemical equilibrium. Numerical simulation of the observed effects was performed for low and high oxidation degrees of propane taking into account changes in the composition of positive ions in the plasma. Good agreement was obtained between measurements and calculations of the electron density during plasma decay in these cases. Here it was shown that the formation of cluster ions in the discharge afterglow plays a fundamental role. The plasma decay was controlled by electron recombination with hydrocarbon cluster ion at low oxidation degree of propane and with water cluster (hydrated) ions at high oxidation degree. A hypothesis was proposed to explain the observed nonmonotonic behavior of the plasma decay rate with an increase in the propane oxidation in the discharge, based on the formation of hydrated hydrocarbon ions C_xH_y⁺(H₂O)_k at moderate oxidation degrees.

• Research Organization: Pennsylvania State Univ., University Park, PA (United States); Princeton Univ., NJ (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE); Russian Foundation for Basic Research
• Grant/Contract Number: FE0026825; 19-32-90012
• OSTI ID: 1976988
• Alternate ID(s): OSTI ID: 1811711
• Journal Information: Combustion and Flame, Vol. 233, Issue C; ISSN 0010-2180
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
hydrocarbons
combustible mixtures
hydrocarbon ions
cluster ions
dissociative electron-ion recombination
non-equilibrium plasma decay
high-voltage nanosecond discharge