Detonation Initiation in Liquid Fuel Sprays by Successive Electric Discharges

Decreasing the predetonation distance in a drop explosive mixture by combined means

“…Ignition was performed with a high-voltage electric discharger placed at a distance of 60 mm from the atomizer nozzle, where the average size of drops in the jet was 5-6 µ m. Beginning with a discharge energy of E ~ 3300 J, a direct initiation of detonation took place in the mixture, which propagated at a velocity of 1700-1800 m/s. At a discharge energy in the range 1100 < E < 3300 J, a decaying shock wave and a decelerated flame were observed [11,12]. At E < 1100 J, there was a certain acceleration of the flame along the tube but pressure waves propagated at velocities of no more than 400-450 m/s.…”

“…Data on experimental observations of deflagration-to-detonation transitions in drop mixtures of hydrocarbon fuels with air are unavailable in the literature. In the context of increasing interest in the practical use of detonation combustion in aircraft engines and power engineering [14], it is topical to study a deflagration-to-detonation transitions in drop mixtures of hydrocarbon fuel with air.The purpose of this work was to use combined means for attaining a deflagration-to-detonation transition and decreasing the predetonation distance in drop hydrocarbon-air mixtures.Previously [11,12], we studied detonation initiation in the flow of a drop n -hexane-air mixture in a ( 1.3 ± 0.1)-fold excess of fuel under normal conditions in a 1.5-m-long tube 51 mm in diameter, which was equipped with a full-flow air-assist atomizer at one end and a detonation arrester at the other. Ignition was performed with a high-voltage electric discharger placed at a distance of 60 mm from the atomizer nozzle, where the average size of drops in the jet was 5-6 µ m. Beginning with a discharge energy of E ~ 3300 J, a direct initiation of detonation took place in the mixture, which propagated at a velocity of 1700-1800 m/s.…”

“…At E < 1100 J, there was a certain acceleration of the flame along the tube but pressure waves propagated at velocities of no more than 400-450 m/s. To decrease the detonation initiation energy, we performed similar experiments with drop n -hexane-air and n -heptane-air mixtures in tubes of smaller diameters (36 and 28 mm) than those studied earlier [11,12]. In addition, to enhance the turbulence in the jet of the drop mixture coming from the atomizer, a 600-mmlong Shchelkin spiral wound from a steel wire 4 mm in diameter at a spiral pitch of 18 mm was placed in the tube.…”

“…Previously [11,12], we studied detonation initiation in the flow of a drop n -hexane-air mixture in a ( 1.3 ± 0.1)-fold excess of fuel under normal conditions in a 1.5-m-long tube 51 mm in diameter, which was equipped with a full-flow air-assist atomizer at one end and a detonation arrester at the other. Ignition was performed with a high-voltage electric discharger placed at a distance of 60 mm from the atomizer nozzle, where the average size of drops in the jet was 5-6 µ m. Beginning with a discharge energy of E ~ 3300 J, a direct initiation of detonation took place in the mixture, which propagated at a velocity of 1700-1800 m/s.…”

“…In available experimental studies [8][9][10], heterogeneous ("drop") detonation was initiated by strong sources: a shock wave [8], gas detonation [9], or an explosive charge [10]. Earlier [11,12], we initiated detonation of sprays of liquid fuel in air by one or two electric discharges. In drop mixtures of liquid fuel with gaseous oxygen, a deflagration-to-detonation transition was observed by Pierce and Nicholls [13], who reported that the predetonation distance was 20-100 tube calibers long.…”