Suppressions of gasoline-air mixture explosion by non-premixed nitrogen in a closed tunnel

• Gasoline-air explosions were suppressed by non-premixed N2 in a closed tunnel.
• Flame intensity (brightness) was used to evaluate suppression effects.
• Influence of initial gasoline vapor concentration on suppression effect was studied.
• The critical length of the ignition section was discussed.
• The critical O2 concentration in the suppression section was obtained in the paper.

Suppressions of the gasoline-air mixture explosion by non-premixed nitrogen were studied experimentally in a closed tunnel. During the process of experiments, the test tunnel was divided into three parts by two plastic films: igniting section, N2 suppression section and gasoline-air mixture section. Meanwhile, two flame intensity sensors were respectively deployed in front of and behind the N2 suppression section. Based on the analysis of the flame intensities, overpressures and concentrations of the gas components after ignition, the gasoline vapor concentration range in which the explosions can be effectively suppressed, critical length of the ignition section and critical O2 concentration in the suppression section were discussed in detail. It was indicated that values of maximum overpressure and overpressure rise rate of the explosions with non-premixed suppression were lower than that without such suppression. When the initial gasoline vapor concentration is constant, the critical length of the ignition section increases with the growth of the length of the N2 suppression section. The relationship between the critical length of the ignition section and the initial gasoline vapor concentration can be described as a negative exponential expression of y = ae−bx. There are three modes for the explosion suppression experiments: complete suppression mode, partial suppression mode and suppression failure mode. The critical O2 concentration in the N2 suppression section decreases with increase of the λ (a dimensionless parameter of ignition section length/N2 suppression section length) when the initial gasoline vapor concentration is 2.0%.