Experimental and numerical study of flame acceleration and transition to detonation in narrow channels

摘要

From a scientific point of view, Deflagration to Detonation Transition (DDT) continues to draw significant interest in the research community as an outstanding, physics-rich fundamental problem in combustion science. From a practical perspective, it is important to study and understand DDT in order to develop engineering correlations and simulation tools that can be applied to the prevention and mitigation of explosions. In the current study, flame acceleration and transition to detonation of stoichiometric H_2/O_2 mixtures in narrow channels was investigated using a combined experimental and numerical approach. The experimental setup included direct-, schlieren- and shadowgraph visualization of a 6 mm × 6 mm square channel of 1 m in length. The channel was closed in the region where the mixture was ignited, and open at the other end. Experimental x-t diagrams using shadowgraph, revealed that transition to detonation regularly occurred around the first two-thirds of the channel (～ 25 - 55 cm); close-ups to the ignition location using schlieren and shadowgraph visualization showed important - details of the ignition kernel. Three-dimensional numerical simulations using quarter symmetry with a simplified chemical-diffusive model are in reasonable agreement with the experimental results, and shed light into the DDT mechanism in this type of configuration.