Effects of the vent burst pressure on the duct-vented explosion of hydrogen-methane-air mixtures

The effects of the vent burst pressure (Pv) on the vented explosion of hydrogen-methane-air mixtures are investigated in a cylindrical vessel connected with a duct. The results demonstrate that Pv significantly affects the flame behaviors and overpressure inside and outside the venting configuration. The flame front velocity at the vent increases with Pv. Two pressure peaks, Pac, caused by the acoustically enhanced combustion, and Pse, caused by the secondary explosion, dominate within the vessel at Pv < 132 kPa and Pv >= 132 kPa, respectively. The maximum overpressure (Pmax) inside the duct increases with Pv. The maximum pressure rise (dp/dt) of the duct is always higher than that of the vessel. As Pv increases, increased turbulence of unburned gases within the duct results in higher dp/dt. Exit flame speed increases with Pv. When Pv >= 153 kPa, "Mach disk" appears outside the relief duct. Three pressure peaks, Pa, Pb, and Pext, due to vent failure, the secondary explosion, and the external explosion, respectively, occur in the external pressure curve. Pb dominates outside the configuration except for Pv = 153 kPa.