The effectiveness of imploding waves at detonation initiation of stoichiometric ethylene- and propane–oxygen–udnitrogen mixtures in a tube was investigated. Implosions were driven by twice-shocked gas located at the end of audshock tube, and wave strength was varied to determine the critical conditions necessary for initiation as a function ofuddiluent concentration for each fuel. Hydrocarbon–air mixtures were not detonated due to facility limitations,udhowever, detonations were achieved with nitrogen dilutions as large as 60 and 40% in ethylene and propaneudmixtures, respectively. The critical-energy input required for detonation of each dilution was then estimated usingudthe unsteady energy equation. Blast-wave initiation theory was reviewed and the effect of tube wall proximity to theudblast-wave source was considered. Estimated critical energies were found to scale better with the planar initiationudenergy than the spherical initiation energy, suggesting that detonation initiation was influenced by wave reflectionudfrom the tube walls.
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