Studies of the TNT equivalence of propane, propane/oxygen, and ANFO

The TNT equivalences of equal masses of propane, a stoichiometric mixture of propane and oxygen, and ammonium-nitrate–fuel-oil (ANFO) were calculated based on the peak hydrostatic and dynamic pressures, the hydrostatic and dynamic pressure positive-phase impulses, and the positive-phase integrated work flux. It was assumed that the propane had been dispersed as a vapour/droplet cloud to form a stoichiometric mixture with atmospheric oxygen before detonation. This is the objective for fuel–air weapons and the worst-case scenario for accidental propane explosions such as boiling liquid expanding vapour explosions. The TNT equivalences of propane/oxygen and ANFO, which have energy yields less than TNT, show little variation when calculated using the different blast wave physical properties. In contrast, the equivalences for propane, which has a significantly higher energy yield than TNT, show a broad range of values, with those based on the impulses being significantly larger than those based on the peak values. The equivalence based on the positive-phase integrated work flux is intermediate between the peak and impulse values. The reasons for these differences are illustrated and discussed.