Non-premixed flame propagation inside and outside the different three-way tubes after the self-ignition of pressurized hydrogen

Accidental leakage of pressurized hydrogen into the pipeline is often accompanied by the non-premixed self-ignition flame, whilst the complex structure of pipeline affects the flame propagation. In this study, the propagation of self-ignition hydrogen flame in different three-way tubes is studied and the flame evolution near the two exits is compared. Effects of the tube length and the location of bifurcation points are investigated. Results show that the bifurcation structure has the attenuation effect on the intensity of flame and shock wave, and they attenuate more sharply in the branch pipeline. But the flame intensity can increase again downstream the bifurcation point in the trunk pipeline, and this increase is not continuous and decrease again as the tube length increases. In addition, the flame evolution can be different near two exits of the tube. As the bifurcation point moves downstream, the number of Mach disk and the time required to form the stable flame will increase near the exit of branch pipeline. Despite different flame evolution, the flame morphology and propagation are all controlled by the shock wave structures before the formation of the vortex, but the flame changes dramatically and grows rapidly to form the stable lift-off flame after the formation of the vortex.