Phenomenological aspects in explosive powder/gas two-phase detonations

Abstract

Attempts were made to detonate a special ball-milled TNT powder of about 30-μm particle size thatwas dispersed in air, oxygen, and nitrogen at nominally 1 kg/m3 in a highly instrumented 152-mm-diameter 7.31-m-long horizontal detonation tube. Results were successful in both air and oxygen, but not in nitrogen. New modifications to the detonation tube for this work included implementation of two-color temperature-measuring instrumentation, and the repositioning of some piezoelectric pressure transducers and fiberoptic light-detector probes so that phenomena such as spinning detonation and multiple-front detonations could be better identified and quantified. TIGER Code Chapman-Jouguet (CJ) computations were made for TNT, RDX, and mixtures of TNT and RDX in air, oxygen, and nitrogen at concentrations up to 100 kg/m3. The computed results for TNT in air and oxygen at a concentration of 1 kg/m3 for the detonation velocities, pressures, and temperatures were 2.00 km/s, 4.00 MPa, 3250 K in air and 2.05 km/s, 4.40 MPa, 3740 K in oxygen. Experimental results for TNT powder were 1.82 km/s, 4.06 MPa, 3245 K in air and 1.90 km/s, 4.61 MPa, 4240 K in oxygen; the experimental concentrations, which were monitored with laser optics, were determined to be 1 kg/m3 with an estimated error of ± 10%. Subsequent experiments were conducted with RDX, alone and in mixtures with TNT, in attempts to achieve detonation in nitrogen. These were successful except when the RDX percentage fell below 20% by weight. Results of sucessful detonations of RDX/TNT mixtures indicated multiple-front detonations, suggesting that the TNT was reacting behind the RDX detonation front in such a manner that it supported the overall detonation.