On the explosion length invariance in direct initiation of detonation

✍ Scribed by Matei I. Radulescu; Andrew J. Higgins; John H.S. Lee; Stephen B. Murray

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 462 KB
• Volume: 28
• Category: Article
• ISSN: 1540-7489
• DOI: 10.1016/s0082-0784(00)80264-7

✦ Synopsis

In this paper, the critical energies required to initiate a cylindrical or spherical detonation are measured experimentally in ethylene-air mixtures at ambient conditions. These results are used to validate the critical explosion length invariance, linking the critical energies in the different geometries. For the entire range of mixtures investigated, the critical explosion length was found to be invariant with geometry. The R* O critical explosion length was found to correlate well with the cell size of the mixture, yielding R* ഡ O . Measurements of the shock wave velocity in the critical regime indicated that for both spherical and 32 k cylindrical detonations, the final formation of a self-sustained detonation occurred at a radius on the order of the critical explosion length , suggesting that an important length scale in the direct initiation of R* O detonation is the explosion length. A transitional geometry between spherical and cylindrical was also investigated by using finite lengths of detonating cords for initiation. It was found that when the critical length of cord is smaller than approximately , it is the total energy of the source that governs whether R* O detonation is initiated, as in spherical initiation. However, when the length of cord is longer than , R* O detonation is governed by the energy per unit length, as in the case of cylindrical initiation. The present results are in accord with the results found by Matsui and Lee in their investigation of direct initiation of acetylene-oxygen mixtures by linear sparks, suggesting that these scaling laws are universal for both fueloxygen and fuel-air mixtures.