Visualization of spontaneous ignition and flame behavior in tubes with and without obstacles during the high-pressure hydrogen release

Abstract

This paper studies the effects of triangle obstacles inside the tube on the ignition mechanism and subsequent flame development in a semi-confined space when high-pressure hydrogen sudden release. Smooth tube and obstructed tube with optical glasses are constructed where controlled high-pressure hydrogen are released. High-speed direct photography is used to image the flame evolution while pressure transducers are used to obtain pressure-time traces both inside the tube and exhaust chamber. These cases that hydrogen with various burst pressure jets into the smooth and obstructed tubes are tested. It is found that spontaneous ignition occurs in the boundary layer of the tube in the smooth tube, a complete fire spanning the cross-section is reached as the flame propagates within the mixing region. The appearance of obstacles is found to have a significant effect on the ignition mechanism and flame structure. A two-way dissemination reflected shock wave forms and three possible ignition region emerges surrounding the obstacles. The flame propagation restricted between the leading shock wave and hydrogen jet. The flame experiences a split that the front flame in the vicinity of the obstacle gradually dies out and the rear flame continues propagating within the mixing region. The flame evolution and pressure variation in the exhaust chamber show that obstacles inside the tube do not aggravate the disaster in the semi-confined chamber.