Non-Monotonic Overpressure vs. H2 Concentration Behavoiur During Vented Deflagration. Experimental Results

In industrial buildings explosion relief panels or doors are often used to reduce damages caused by gas explosion. Decades of research produced a significant contribution to the understanding of the phenomena aiming at establish an effective method by which the explosive overpressure could be reliably predicted. All the methods predict a monotonic increase of the overpressure with the concentration of the gas in the range from the lower explosion limit to the stoichiometric one. Nevertheless in few cases a non-monotonic behaviour of the maximum developed pressure as a function of hydrogen concentration was reported in the literature. The non-monotonic behaviour was also observed during experimental tests performed at the Scalbatraio laboratory at the University of Pisa, in a 25m 3 vented combustion test facility, with a vent area of 1,12m 2 . This paper is aimed to present the results obtained during the tests and to investigate the possible explanation of the phenomenon. Key words: Hydrogen, Vent, Deflagration