Concentration limits to unconfined detonation of ethane-air

Abstract

Solid explosive (Tetryl) charges were used to initiate spherically propagating detonation waves in pure ethane well mixed with air at one atmosphere initial pressure. Whereas the most easily detonated mixture, 6.6% ethane (1.18 × stoicheiometric fuel concentration), required about 0.018 kg of Tetryl, fuel-lean (4.5%v) and fuel-rich (9.1%v) mixtures were detonated only by 0.52 kg of explosive. Quite good accord was shown between the data and a simple phenomenological model of detonation. The concentration limits in this experimental study were defined only by the maximum explosive charge size permitted. Neither “curve fits” to the experimental data nor the theoretical model established the existence of any “infinite initiator energy” concentration limit to spherical detonation. Attention is drawn to the need to prefix any quotation of limits for spherical detonation by the initiator type and strength and, conversely, any determination of minimum detonation energy by the concentration limits over which such an initiator will succeed.