In this work, an experimental description has been given of some physical processes occurring and induced in atmospheric pressure nitrogen by very fast spark discharges. The time range investigated spans from the very first tens of nanoseconds (spark phase) up to the submillisecond scale. Experiments were based upon the application of both the laser-schlieren technique, yielding 2-D qualitative visualization, and the 1-D quantitative Rayleigh laser-light scattering, from which the gas mass density radial distributions were derived, for delays from the spark greater than 1 ¼s. Following the energy deposition stage, three main time domains have been identified, corresponding respectively to i) the fast expansion of the excited gas kernel and of the resulting shock wave, (0.210 ¼s) ii) the subsequent, ordered gas flow-field, involving recirculation of fresh gases into the spark gap (1040 ¼s) and, finally, iii) the transition of the coherent fluid dynamic structures toward chaotic, turbulent mixing of excited and cold gases (40200 ¼s). Next, from the depolarized light scattering data in the range 515 ¼s, some indications were drawn, about the recombination process of the atomic nitrogen, which has been shown to have lifetimes of the order of tens of microseconds, thus exhibiting interesting properties as an efficient energy reservoir.
Development of hot nitrogen kernel, produced by a very fast spark discharge
Borghese A;
1988
Abstract
In this work, an experimental description has been given of some physical processes occurring and induced in atmospheric pressure nitrogen by very fast spark discharges. The time range investigated spans from the very first tens of nanoseconds (spark phase) up to the submillisecond scale. Experiments were based upon the application of both the laser-schlieren technique, yielding 2-D qualitative visualization, and the 1-D quantitative Rayleigh laser-light scattering, from which the gas mass density radial distributions were derived, for delays from the spark greater than 1 ¼s. Following the energy deposition stage, three main time domains have been identified, corresponding respectively to i) the fast expansion of the excited gas kernel and of the resulting shock wave, (0.210 ¼s) ii) the subsequent, ordered gas flow-field, involving recirculation of fresh gases into the spark gap (1040 ¼s) and, finally, iii) the transition of the coherent fluid dynamic structures toward chaotic, turbulent mixing of excited and cold gases (40200 ¼s). Next, from the depolarized light scattering data in the range 515 ¼s, some indications were drawn, about the recombination process of the atomic nitrogen, which has been shown to have lifetimes of the order of tens of microseconds, thus exhibiting interesting properties as an efficient energy reservoir.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
