Explosions of gasoline–air mixture in the tunnels containing branch configuration

•Branch tunnels enhanced the ΔPmax, ⅆp/ⅆtⅆp/ⅆt and KG due to the induced turbulence.•Overpressure rise rate and KG increased as a function of the branch tunnels number.•The maximum flame speed increased as the branch number increasing from 0 to 3.•The maximum flame speed dropped when the branch tunnels number exceeded 3.

In order to investigate the effects of branch tunnels on explosion propagation, experiments were performed in five different configuration tunnels (straight configuration and configurations with 1 branch, 2 branches, 3 branches and 4 branches). Pressure and flame transducers were used to record the history of the pressure development and track the velocity of the flame front. It was shown that the branch tunnels had ability to enhance the maximum overpressure, rate of overpressure rise, and deflagration index (KG) of the gasoline–air mixture explosion due to the turbulence induced by the branch tunnels. The overpressure rise rate and KG of the explosion increased as a function of the number of branch tunnels. Experiments also showed that the maximum flame speed increased as the branch number increasing from 0 to 3 due to the enlargement of turbulence induced by the branch tunnels. However, an increase of branch number did not always lead to an enhancement of flame speed because the heat loss was intensified resulting from the increase of flame surface caused by the branch tunnels. When the number of branch tunnels exceeded 3, the maximum flame speed dropped.