Explosion of gasoline/air mixture in confined space with weakly constrained structure at the top

An experimental system of a confined space with a weakly constrained structure at the top was established. A series of gasoline/air mixture explosion experiments were conducted, and overpressure characteristics as well as flame behaviors were obtained. The results show that the internal overpressure exhibited a phenomenon of multi-peaks and pressure oscillations, induced by such factors as venting, external explosion, flame extension, etc. The value of the external overpressure decreased obviously with the increase of the distance from the weakly constrained structure, and the value along the vertical direction was larger than that along the horizontal direction. The impact of the weakly constrained structure was mainly reflected in the enhancement effect on the overpressure value and the lagging effect on the development rate of the explosion. The overpressure value showed the tendency to increase at first and then to decrease with the increase of the volume fraction of the gasoline/air vapor volume corresponding to the maximum overpressure, which is 1.79%. The flame propagation process involves three stages, i.e. stages of primary combustion, transitional combustion and secondary combustion. Affected by the Rayleigh instability, the Helmholtz instability and the baroclinic effect, the flame front was twisted and wrinkled, and the maximum height and maximum diameter were 0.80 and 0.55 m, respectively.