60th Gaseous Electronics Conference
Volume 52, Number 9
Tuesday–Friday, October 2–5, 2007;
Arlington, Virginia
Session BT1: Plasma Combustion and Chemistry
8:00 AM–9:30 AM,
Tuesday, October 2, 2007
Doubletree Crystal City
Room: Crystal Ballroom A
Chair: Leanne Pitchford, LAPLACE
Abstract ID: BAPS.2007.GEC.BT1.1
Abstract: BT1.00001 : Plasma-Assisted Flame Ignition and Stabilization using Nanosecond Repetitively Pulsed Discharges*
8:00 AM–8:30 AM
Preview Abstract
Abstract
Author:
Christophe Laux
(Ecole Centrale Paris)
Ever more stringent environmental regulations are providing
impetus for reducing pollutant emissions, in particular nitric
oxides and soot, in internal combustion and aircraft engines.
Lean or diluted combustible mixtures are of particular interest
because they burn at lower flame temperatures than stoichiometric
mixtures and thus produce lesser amounts of thermal nitric
oxides. Over the past decade, high voltage nanosecond pulsed
discharges have been demonstrated as energy efficient way to
ignite such mixtures. However, the practical application of these
discharges for ignition purposes is limited by the very high
electric fields required, especially in high pressure combustion
chambers. Moreover, stabilization requires a steady-state
addition of energy that cannot be achieved with single or low
repetition frequency pulses.
In the present work, we investigate the applicability and
effectiveness of high voltage nanosecond discharges with high
pulse repetition frequencies, typically up to 100 kHz. The high
repetition frequencies are chosen to exceed the recombination
rate of chemically active species. In this way, the concentration
of active species can build up between consecutive pulses,
thus yielding significantly higher concentrations than with low
frequency pulses. These discharges are investigated for two
applications, the ignition of diluted air/propane mixtures at
pressures up to several bars in a constant volume chamber, and
the stabilization of atmospheric pressure lean premixed
air/propane flames. Time-resolved electric and spectroscopic
measurements are presented to analyze the discharge regimes, the
energy deposition, the gas temperature evolution, the electron
number density, and the production of excited species. The
results show that nanosecond repetitive pulses produce ultrafast
gas heating and atomic oxygen generation, both on nanosecond time
scales, via excitation of molecular nitrogen followed by
dissociative quenching of molecular oxygen. These effects result
in a significant reduction of the lower flammability limit
and in the subsequent extension of the domain of flame stability,
for a power consumption typically less than 1{\%} of the heat
released by the flame.
*This work has been supported by Safran, CNRS, and DGA under the INCA program (Initiative sur la Combustion Avanc\'ee) directed by Dr. M. Cazalens
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.GEC.BT1.1