Evolution of charged species in propane/air flames: mass-spectrometric analysis and modelling**This paper was presented at the Second International Symposium on Nonequilibrium Processes, Combustion, and Atmospheric Phenomena (Dagomys, Sochi, Russia, 3–7 October 2006).

Abstract

Experimental and modelling studies of ion formation during combustion of propane/air mixtures are presented. The positive and negative ions mass/charge spectra in propane/air stoichiometric flame at atmospheric pressure are recorded in the range from 0 to 512 atomic mass units. The C2H3O+ and ions are found to be the most abundant ionic species in the flame front region. By increasing the distance from the flame front the ion composition changes significantly. In the burnt gas region the H3O+, NO+, , ions are found to be the major charged species. To explain the experimental results the extended kinetic model describing the ion formation in flame and in the extraction system of the mass-spectrometer as well as ion–soot interaction is developed. It is shown that the ionic clusters, which are observed experimentally, form during the adiabatic expansion in the extraction system, and the presence of soot particles may change the total positive and negative ion concentrations in the gas phase.