COMPARISON OF TNT-EQUIVALENCE APPROACH, TNO MULTI-ENERGY APPROACH AND A CFD APPROACH IN INVESTIGATING HEMISPHERIC HYDROGEN-AIR VAPOR CLOUD EXPLOSIONS.

In this work, we investigate the pressure wave generated by a so-called vapor cloud explosion (VCE), in the particular case in which the hydrogen-air mixture is homogeneous, presents a hemispheric geometry and the ignition occurs at the center of the hemisphere. Then we compare the results obtained on this particular geometry using three different approaches, namely TNT-equivalence approach, TNO multi-energy approach and ``1D point-symmetric deflagration'' approach, which solves the Fluid Dynamics equations (Computational Fluid Dynamics or CFD approach) in the case of 1D point-symmetric flows. These three approaches have been compared on a large-scale experiment performed at Fraunhofer Institute of Chemical Technology. As we will show, the TNT-equivalence method have shown not to be a good candidate to investigate VCE. The CFD approach gives a pressure field which fits the experimental one, providing that the flame speed is correctly evaluated. Concerning the multi-energy approach, it is possible to establish a relation between its strength index and the fundamental flame speed, a part from a region close to the one containing the burnt gas.