Characteristics of closed and vented explosions of gasoline-air mixture in a square tube

In order to investigate the closed explosion and venting characteristics of gasoline-air mixture, two kinds of explosion modes were studied by using a visualized square tube, and numerical simulation was carried out based on the wall-adapting local eddy-viscosity (WALE) model and Zimont premixed flame model. The results show the followings. (1) The number of the peaks on the overpressure time series curve for the vented explosion is greater than that for the closed explosion, and there is a violent oscillation similar to a simple harmonic vibration on the overpressure time series curve of the vented explosion, while the characteristic parameters of explosion overpressure in the closed explosion are significantly higher than those in the vented explosion. (2) The maximum flame propagation speed in the closed explosion is significantly lower than that in the vented explosion, but the former reaches the maximum at the beginning of flame propagation, while the latter reaches the maximum at the end of flame propagation. (3) Tulip-shaped flame appears in the closed explosion condition, while mushroom-shaped flame appears in the venting condition. The formation of the tulip-shaped flame is related to the coupling effects of flame front, flow field and dynamic pressure of flow field in the pipe, while the mushroom-shaped flame is caused by the combined action of turbulence and baroclinic effect in the external flow field.