Effects of ignition, obstacle, and side vent locations on vented hydrogen-air explosions in an obstructed duct

Experiments were conducted in a 6-m-long duct with a cross section of 300 mm x 300 mm to investigate the effects of the ignition, obstacle, and side vent locations on the vented deflagration of 18 vol% hydrogen-air mixtures. Significant effects of all three parameters were found. For ignitions near the open end, explosion venting was accompanied by continuous pressure oscillations. When the ignition location was near the closed end, dominant pressure peaks appeared at the exit of the duct, which were due to the shock-wave resulting from flame acceleration induced by the obstacle. The overall maximum internal and external overpressures increased when the ignition location was moved from near the open end to the closed end of the duct but did not vary monotonically with the location of the obstacle or side vent. In the tests with different obstacle locations, the maximum internal pressure occurred near the open end when the obstacle was located at the center of the duct. Compared to the cases without a side vent, the maximum internal overpressure was effectively reduced when a side vent was introduced near the ignition point but increased when the side vent was located near the open end of the duct. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.