The overpressure and temperature characteristics of hydrogen-air mixtures during a vented explosion in a large L/D ratio duct: Effect of burst pressure

Abstract

Explosion venting is an effective way to reduce the hazards of gases and dust fuel explosion in a confined space. Since there is little attention paid to the thermal radiant damage produced by the vented flame, the surface temperature distribution for hydrogen-air mixtures with different burst pressures (Pv) is investigated in a large L/D ratio duct. The high-speed shadowgraph imaging system, pressure testing system and infrared thermal imager are used to record the explosion venting process. The Pv and the thickness (δ) of the polyester vent cover are in the direct ratio, while the vent failure time shows a nonlinear relationship with the δ. Five internal overpressure peaks (P1, P2, P3, PRef, Pneg) are distinguished. With the addition of Pv, P1 increases gradually, while P2 disappears in some higher Pv. The external flow field is obtained and discussed in detail. The cases of lower Pv with the unburned gas escaping from the vessel can sustain a high flame speed, whereas other cases only involve a flame jetting process with a relatively low speed. The high-temperature (>500 ℃) duration shows an ‘M’ shape with the Pv. Besides, the safety distances to prevent humans from suffering thermal radiant damage have been determined.