The differences in quenching characteristics of H2/Air deflagration and detonation propagation in the T-shape pipeline

Bifurcated pipeline is a typical structure in industrial and transportation; paying attention to the propagation of explosions in it and taking measures to prevent explosions are extra important. The deflagration and detonation propagation characteristics of stoichiometric H2/Air mixture were investigated under initial pressure ranging from 25 kPa to 45 kPa based on the T-shape pipeline experimental system; the effects of flame arrester locations and structure were further experimentally explored under different initial pressures. Differences in the velocity characteristics of deflagration and detonation in the T-shape pipeline and the quenching characteristics after passing through differently positioned flame arresters were found. The results show that enhanced turbulence caused by the change in cross-section at the T-junction promotes the deflagration propagation, and the diffraction generated by the corners at the T-junction suppresses the detonation. Moreover, the velocity changing magnitude (A) indicated that deflagration accelerates faster and detonation attenuation reduces as initial pres-sure rises in the branch. The experimental results of the flame arrester installed in the pipeline suggested that deflagration and detonation slow down, and installing locations influence quenching pressures and decelerating reduction magnitude (S). According to the pressure signals, there are four flame stages: none, weak, rises sharply to peak, and fluctuations decline. The quenching pressure of detonation is higher than deflagration when the flame arrester is in the same position. Deflagration has higher quenching pressure of 60 kPa and S of 84.5% when the flame arrester is installed in the branch; Detonation has higher quenching pressure of 80 kPa when the flame arrester is installed in the straight while a higher S of 83.3% in the upstream. The cavity experiments of the flame arrester confirmed that deflagration deceleration comes from the combined effects of turbulent acceleration due to cross-section changes and deceleration due to heat exchange in the flame arrester; Detonation deceleration is due to the obstruction of the expansion wave caused by the gradual-expansion entrance of the flame arrester.