An experimental study on the flame behaviors of H2/CO/Air mixtures in closed tube with varying number of obstacles

In order to investigate the flame behavior of syngas/air mixtures after leakage in industrial scenarios. A series of fence-type obstacles with a blockage ratio of 0.3 were installed in a closed tube to simulate common blockage scenarios. The stoichiometric mixtures of H2/CO/Air with hydrogen fractions ranging from 10 % to 50 % were used to simulate typical syngas compositions. Results indicate that the increase in hydrogen fractions and the number of obstacles can enhance flame acceleration and oscillation downstream of obstacles. The flame inverts into the tulip shape after it passes the obstacle area, and then the distorted “tulip” flame appears. The obstacles number has no influence on the instant of the planar flame formation, because the flow competition initiates when the flame passes the first obstacle channel. However, the initial instant of the first “tulip” distortion decrease with the increasing obstacle number. The “tulip” flame is a hydrodynamic phenomenon, while the distortion of the “tulip” flame is related to pressure waves. At higher hydrogen fractions, the obstacle number increases the maximum overpressure more significantly. In practical scenarios, it is advisable to limit the number of obstacles as much as possible and prevent syngas leaks with higher hydrogen fractions. •The effect of obstacle on explosion behaviors was experimentally studied.•Both number of obstacles and hydrogen fraction increase the explosion intensity.•Number of obstacles has diverse effects on planar and distorted “tulip” flames.•Flame inversion is a hydrodynamic phenomenon related to flow competition.•The distortion of “tulip” flame is associated with pressure waves.