Effects of a T-shaped branch pipe on overpressureof gasoline-air mixture explosion

To investigate the effects of a T-shaped branch structure on the overpressures during the explosions of the gasoline-air mixture in a pipe, we conducted multiple parameter contrast experiments under the conditions of different initial gasoline vaper volume fractions and different initial ignition energy, and carried out visualized investigation on the flame propagation of the mixture. Our research reveal the following results: the T-shaped branch pipe can enhance the explosive overpressure of the gasoline-air mixture in a pipe, and the degree of this enhancement is closely related with the increase of the initial gasoline vaper volume fraction approximately in a parabolic trend, and with the maximum value obtained around the stoichiometric initial concentration. The maximum explosive overpressures before and after the T-shaped branch pipe increases linearly with the growth of the initial ignition energy. The effects of the T-shaped branch pipe on raising the degree of the explosion mainly originate from four factors: the wave diffraction and reflection, the turbulence enhancement, the sudden expansion of the pipe cross-section area and the reinforcement of the disturbance by the obstacles. It can be seen from the visual analysis that, when the flame propagates through the T-shaped branch pipe, the flame front is distorted seriously into creases, the flame surface area is enlarged, and the returning flames are observed, which exerts a destructive effect on the wall of the T-shaped branch pipe.