Luc Brunet

Assessment of the blast wave generated by a low-energy plasma igniter and spectroscopic measurements

Assessment of the output of plasma devices and comparison with thermodynamic calculations makes it possible to improve the efficiency of these devices. The experiment is based on two capacitor banks (1 and 20 kJ) and on a small plasma torch used in electrothermal-chemical (ETC) basic studies. The behavior of a plasma igniter is studied using spectroscopic measurements to obtain the electronic density from H/sub /spl alpha// line Stark width. The temperature is obtained from Boltzmann plots on copper and iron atomic lines. Under the local thermodynamic equilibrium assumption, the electron density (N/sub e/) depends on the electron temperature (T/sub e/) via Sahas law (N/sub e//spl prop/T/sub e//sup 3/4/). A check on this behavior permits validation of the thermodynamic equilibrium assumption, and the pressure of the emitting area is obtained by using Daltons law. The flight time and the overpressure generated by the plasma igniter can be compared at the Sedov-Taylor blast wave theory. Finally, we give a comparison of the pressure of the emitting area found using Daltons law and also by applying the Sedov-Taylor blast wave model.

Experimental assessment of a 1 kJ electro-pyrotechnic device ignited in the 300-1000 V range for ETC studies

In order to assess a plasma igniter, a low energy and low cost device has been designed. This device makes it possible to produce 10 to 100 mg of high temperature gaseous mixture that can reach several k Kelvin, using only 1 or 2 kT of electrical energy. This paper presents the optimization of the discharge cell size with an experimental design method and the influence of the material on the device. These experimental measurements and methods are discussed and compared to thermodynamic calculations. An analysis has been made of the effects of the device design on output parameters such as the pulse duration, the plasma resistivity and the energy conversion. A first approach using the spectroscopic measurements is presented in order to assess the temperature and the chemical species produced by the device. The spectroscopic investigation is performed using both atomic and molecular emissions with time-resolved data sampling (Princeton Instruments optical multichannel analyzer). The interaction at low pressure (10/sup 5/ Pa) of a C/sub x/H/sub y/O/sub z/N/sub t/ plasma with a single base propellant is studied at the ignition/nonignition threshold in order to determine which physical parameters are predominant for the energy transfer.

Emptying Time of a Tank Filled up with Explosive Paste. Comparison between Experimental Measurements and Predictions Based on Rheological Characterization of the Paste

One industrial process used by Nexter Munitions to manufacture pyrotechnical materials consists in preparing an emulsion of wax in TNT (2,4,6‐trinitrotoluene) and adding Aluminium and ONTA (3‐nitro‐1,2,4‐triazole‐5‐one) particles. When the suspension is homogeneous, it is allowed to flow by gravity through a pipe located at the bottom of the tank and to fill up a shell body. The suspension is characterized by a solid volume fraction of 53.4%, which leads to high viscosities. In some circumstances, the emptying time is prohibitively long and the economic profitability is reduced. This study has been performed to make the emptying time lower with the constraint of unchanged volume fractions and grains mean diameter. So, we investigated the influence of the grain size distribution on the suspension viscosity. Different samples of Aluminium and ONTA have been used, with rather small differences in grain size distributions. The suspensions have been prepared in the industrial tank and the flow cast times measu...