Gas explosion flame propagation over various hollow-square obstacles

•Three typical hollow-square obstacles were studied.•The flame structure is dependent on the hollow shape.•Mechanisms for the observed phenomena are discussed.

A semi-confined transparent chamber measuring 150 mm × 150 mm × 500 mm was constructed. The gas explosion flame propagated away from the ignition source and interacted with a single hollow-square obstacle along its path. The effects of the hollow-square obstacle on gas explosion characteristics were experimentally investigated. Three hollow-square obstacles, with different internal shapes (triangular, square, and circular) but covering the same blockage ratio of 30% were studied. The triangular hollow-square obstacle was found to cause the highest flame turbulence intensity, flame propagating velocity, and explosion overpressure, whereas the circular hollow-square obstacle yielded the lowest values. Mechanisms for the observed phenomena were also discussed in detail and numerical simulations were conducted to validate the mechanism.