Direct initiation of detonations in unconfined gasoline sprays

Large scale experiments on detonation initiation in gasoline-air by two different sources were carried out at stoichiometric conditions. Unconfined clouds of 1100 m(3) volume generated by a special facility had a shape of semicylinder of 15-17 m in length End 6-8 m in radius. Both the charge of condensed HE and the charge of stoichiometric propane-air were used to initiate detonation in the mixture. In case of initiation by a propane-air charge the critical initiation energy was up to 7 times as large as that for HE initiation. The detonation cell size for gasoline-air was determined as 0.04-0.05 m. It was shown, that the well-known correlation between the critical energy of point blast initiation and the cell size failed for this system. The cell size obtained is close to one of propane-air, but no direct transfer of detonation from one mixture to another was observed.