Effects of the ignition modes on explosive characteristics in gasoline-air mixtures

The effects of ignition modes (electric spark ignition and high-explosive ignition) on explosions of gasoline-air mixture was investigated experimentally in a closed pipeline. The overpressure-time curves, flame velocity and shock wave velocity were obtained by the high-speed cameras, pressure sensors, and photoelectric sensors. The results revealed the explosion characteristics of mixture under different ignition modes and the mechanism of gasoline explosion induced by high explosives. Results show that the gasoline vapor–air mixture was ignited by the explosive fireball, and the resulting explosion in turn increased both the peak overpressure and the propagation velocity of the blast wave. The velocity of flame front induced by explosive increased monotonically with distance, ranging from 475 m/s to 646.67 m/s. In contrast, for electric spark-induced ignition, the flame velocity initially increased, then decreased, and subsequently increased with increasing distance, with maximum and minimum values of 32.63 m/s and 2.51 m/s, respectively, which was significantly lower than that observed under explosive ignition. The peak overpressure and shock wave velocity of explosive-induced explosions were higher than those of spark-ignited explosions, whereas the positive pressure duration was shorter, leading to a lower impulse. The reflected shock wave (RSW) induced a secondary explosion, and the subsequent RSW–flame interaction enhanced the chemical reactions, triggering a quasi-detonation with a peak overpressure of 3328.69 kPa. These findings have direct engineering significance for assessing structural vulnerability and designing protective measures against gasoline explosions in oil depots under weapon impact.