Comparative Study of Air-Propane and Air-Heptane Mixtures Ignition by Nanosecond Pulsed Discharges
P. Tardiveau, S. Bentaleb, P. Jeanney, F. Jorand, and S. Pasquiers
Laboratory of Plasma and Gases Physics, CNRS (UMR8578), The University of Paris-Sud, France
Abstract— Ignition of quiescent air-propane and air-heptane mixtures by a single nanosecond pulsed discharge in a point-to-plane configuration is investigated. The objectives are to understand how a very short and non-thermal release of energy is able to develop into these mixtures one or several flame kernels and to achieve their complete combustion. Different concentrations of hydrocarbon, amounts of energy and gap distances are tested. Their effects on the filamentary structure of the discharge are analyzed. Ignition threshold energies and combustion delays are compared for both hydrocarbons. Experimental results for stoechiometric mixtures show that three different modes of ignition are possible, i.e. a single point, a double point or a cylindrical mode, according to the energy density. Combustion delays are strongly reduced and complete combustion of very lean mixtures can be achieved if the amount of energy is slightly increased.
Keywords— Nanosecond discharge, filamentation, ignition, propane, n-heptane, flame kernel, combustion delay