Ignition of a combustible gas mixture by a laser spark excited in the reactor volume

Fast combustion waves and chemi-ionization processes in a flame initiated by a powerful local plasma source in a closed reactor

“…These frames clearly demonstrate the existence of three characteristic phases observed in all experiments upon the initiation of combustion in closed tubes by high-power electric discharges [1,2,6,8]. These are as follows: the first (initial) phase of a relatively short ( t 1 ≤ 10 µs) radiation from a spark excited in the laser beam focus (figure 6(1)); the second phase called, following combustion physics terminology, the 'induction' time, which is a relatively long ( t 2 ≤ 1.0 ms) period preceding the volume combustion of the gas mixture in the reactor (figure 6(2), (3)); and finally, the third phase of the fast ('explosive') volume combustion of the combustible mixture, which is characterized by a bright burst of duration t 3 ≈ 5-10 ms (figure 6(5)- (8)).…”

“…However, the mixture behind the wavefront does not attain the combustion condition. For this reason, the wave observed in the second phase was referred to in [1,2,6,8] as the 'incomplete combustion' wave. The temperature in this wave is estimated to be T ≤ 2000 K < T tr [6].…”

“…These include laser sparks, which are excited on the surface of solid target [1], direct laser heating in the focal spot [2], microwave discharges [3,4] and highcurrent slipping surface discharges [5][6][7]. In [8], the first results on a laser spark freely localized in a reactor chamber and working as a combustion igniter were presented.…”

“…In [1,3,6,8], this initial stage was called 'incomplete combustion '. In experiments with laser sparks and microwave discharges [1][2][3]8], we observed the formation of a wave of weak, relatively uniform 'blue' radiation preceding the volume combustion that appears as a bright burst throughout the reactor volume when the chemical energy in the branching chain reactions is converted almost entirely into heat and the equilibrium temperature is attained in the combusted gas mixture.…”

“…The intent of this work was to find information (in addition to that presented in [1][2][3][4][5][6][7][8]) about the structure and dynamics of the formation of flames initiated by powerful discharges excited in a local small area of a reactor chamber as well as to acquire results on the role of chemi-ionization processes in the ignition of combustion and in the parameters of a developed flame.…”