Explosion dynamics of hydrogen-air mixtures in a flat vessel filled with annular obstacles

Experiments were carried out in a flat vessel (205 mm inner-diameter and 70 mm height) filled with annular obstacles to study the explosion dynamics of hydrogen-air mixtures over a wide equivalence range (0.6 <=phi <= 2.4) at 0.1 MPa and 298 K. Two annular obstacles with the diameters of 100 mm (C1) and 150 mm (C2) were employed. Four obstacle configurations were used, i.e., no obstacle, a single obstacle (C1 or C2) and two obstacles (C1 and C2). Along the radius, three pressure transducers were mounted on the top wall to determine the explosion parameters at different locations. The distance between the transducers and the lid center were 0 mm (P1), 50 mm (P2) and 100 mm (P3). The maximum explosion pressure (pmax) and the maximum pressure rise rate ((dp/dt)max) in the flat vessel was found to be dependent of the measuring point. For a given equivalence ratio, the maximum explosion pressure obtained by P2 was the highest. The maximum pressure rise rate determined by P2 was the highest without an obstacle. For the cases with obstacles, (dp/dt)maxdetermined by P3 was the highest. The explosion time, combustion duration and fast explosion duration were independent of the measuring location. For a fixed measuring point, pmax was decreased by introducing an obstacle due to the extra heat loss to the obstacle. However, depending on the obstacle location, the obstacle could play a dual role in affecting the maximum pressure rise rate and time-parameters, i.e., heat sink or turbulence-generator.