Discharge effect on the negative temperature coefficient behaviour and multistage ignition in C₃H₈-air mixture

It has been first shown by modelling that the discharge does not suppress but stimulates the development and increases the intensity of cool flame. It sharply reduces the delay time of cool flame ignition (isothermal stage) by more than 2 orders of magnitude and diminishes the total induction time by more than 1 order of magnitude due to radicals resulting from dissociation of fuel and oxygen molecules by electron impact. Under the discharge impact, the negative temperature coefficient (NTC) of the overall oxidation rate of the combustible mixture disappears or its maximum is largely decreased at the temperature range 640–760 K. A diminution of NTC maximum depends on the specific deposited energy and is provided by a replacement of the chemical kinetic mechanism at the isothermal stage in the NTC region. The relation between the specific input energy, concentrations of primary radicals resulting from a discharge and key component C₃H₇O₂ which determines the NTC behaviour has been obtained. (paper)