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The Combustion and Transition to Detonation of High Pressure Flammable Gas in Closed Spaces Linked with a Narrow Path

When flammable gases confined or compressed in closed space such as metal cases or shells accidentally combusted, the deflagration could be generated and building up to detonation might cause intensive explosion. High energy density has been pursued in some industrial products or in some manufacturing processes, while the risk of troubles is increasing. Generally the combustion transitions to detonation in highly turbulent flows and takes some buildup time or propagation length. But in the complicated and closed space geometry such as the structure of compressors there are many interactions among compressive wave and rigid surface, and then the transition to detonation frequently has been observed. The product design considering the transition phenomena and reducing the risk of explosions is required in high energy fields. In this study detonations of flammable gas in the high pressure vessel that has spaces linked with narrow curved path were observed and simulated numerically. A high speed camera was used to observe the flame, and the history data were acquired from pressure gauges. In the simulation, XiFoam mounted in Open FOAM was used as the base code. From the visual comparison between the results of the experiment and the simulation, it was shown that turbulent burning velocity suddenly increases and the pressure exceeds a certain value when combustion transition to detonation. These criteria is useful for the design of interior structure of high pressure facilities.