Accession Number : ADA530872

Title :   Deflagration-to-Detonation Transition Control by Nanosecond Gas Discharges

Descriptive Note : Final rept. 1 Apr 2007-1 Apr 2008


Personal Author(s) : Starikovskii, Andrei Y

Full Text :

Report Date : 07 Apr 2008

Pagination or Media Count : 79

Abstract : During the current project, an extensive experimental study of detonation initiation by high{voltage nanosecond gas discharges has been performed in a smooth detonation tube with different discharge chambers and various discharge cell numbers. The chambers were constructed on the basis of our previous studies and introduced analogous cell geometries. The discharge study performed in all the chamber has shown that three modes of discharge development are realized under the experimental conditions: a spark mode with high temperature channel formation, a streamer mode with non{uniform gas excitation, and a transient mode. The mechanisms of deflagration to detonation transition (DDT) under different discharge modes have been proposed and confirmed experimentally. Under spark and transient initiation, simultaneous ignition inside the discharge channel occurs, forming a shock wave and leading to a conventional deflagration to detonation transition (DDT) via an adiabatic explosion. Using a single{cell discharge chamber, the DDT length and time at 1 bar of initial pressure in the square smooth tube with a 20 mm transverse size amounts to 50 mm and 50 microseconds, respectively. The streamer mode of discharge development in the single{cell chamber at an initial pressure of 1 bar results in non{uniform mixture excitation and a successful DDT via a gradient mechanism, which has been confirmed by high-speed time-resolved ICCD imaging. The gradient mechanism implies a longer DDT time of 150 microseconds, though under significantly lower initiation energy of 1 J and a short DDT run-up distance of 50 mm. The gradient mechanism has been studied in more detail in a four{cell discharge chamber. The governing parameters have been established and a significantly higher efficiency in terms of detonation initiation has been achieved due to the enhanced geometry.


Subject Categories : Explosions
      Plasma Physics and Magnetohydrodynamics
      Combustion and Ignition

Distribution Statement : APPROVED FOR PUBLIC RELEASE