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Self-ignition and flame development of high-pressure hydrogen flow in a rectangular tube by simultaneous shadowgraph and direct photograph

The flame observed during the sudden release of high-pressure hydrogen into a tube filled with air, in the absence of an igniter, has not yet been investigated. In this study, the self-ignition and flame development behavior of high-pressure hydrogen flow in a tube is investigated to obtain fundamental knowledge for safety engineering. Two high-speed cameras are used simultaneously to obtain density gradient data from the shadowgraph image and flame dynamics from the direct image. Self-ignition occurs at the point near the sidewall in the region where cold hydrogen and preheated air are mixed by the precursor shock wave. After ignition, the flame propagates along the wall surface and spreads throughout the mixing region.