Experimental investigation of the influence of highly argon dilution on the critical initiation energy for direct initiation of C ₂H ₂-2.5O ₂ mixtures

Direct initiation is achieved via a high voltage capacitor spark discharge, and the critical energy is accurately estimated from the analysis of the current output. A good agreement is found by comparing the critical initiation energy from experimental measurement and Lee's surface energy model. The influences of highly argon dilution on the critical energy of direct initiation are investigated experimentally for C ₂H ₂-2.5O ₂ and 70% argon diluted C ₂H ₂-2.5O ₂ mixtures. The results show that the critical energy is inversely exponential to the initial pressure for C ₂H ₂-2.5O ₂ mixtures with and without highly argon. Both the experimental and theoretical results indicate that dilution of highly argon in C ₂H ₂-2.5O ₂ enhances the critical initiation energy for direct initiation at the same initial condition. Since the critical initiation energy is proportional to the cube of ZND induction zone length, the dilution of highly argon increases the ZND induction zone length of C ₂H ₂-2.5O ₂ mixture under the same initial pressure, and accordingly the critical initiation energy is raised remarkably.