Detonation Initiation by Gradient Mechanism in Propane--Oxygen and Propane--Air Mixtures

An experimental study of detonation initiation by high--voltage nanosecond gas discharge has been performed in smooth detonation tubes. A gradient mechanism was used to initiate detonations in stoichiometric propane--oxygen mixtures with different nitrogen dilution and in propane--air mixtures. Initial pressures from 0.2 to 1bar have been tested. Detonation was formed within 4 transverse tube sizes at initial pressures higher than 0.2 bar for the propane--oxygen mixture and higher than 0.8 bar for the diluted mixture with 40{\%} of nitrogen. The discharge energy inputs were 0.2---0.3 J. The gradient mechanism of detonation formation similar to the one suggested by Zeldovich has been shown to be the governing process. For the mixture with air, a detonation tube with an annular discharge chamber has been designed and tested.