Experimental analysis on propellant laser ignition and combustion process

Abstract. Solid propellants are commonly used for propulsion applications or gas generation, for example in car inflators. In these pyrotechnical devices, the ignition and combustion processes of energetics materials need robustness, dependability and efficiency. To aim this goal, this study seeks to better understand the initiator-propellant interaction, the thermal processes occurring during the early stages of the combustion and modeling the whole process with physical considerations. To reach this objective, an experimental device has been developed. It consists of a cell fitted with quartz windows and pressurized with an inert gas up to 10 MPa. A continuous infrared laser beam heats the upper surface of a cylindrical bulk of propellant (mainly GUNI/BCN based), leading to ignition. The use of various experimental diagnostics like highspeed imaging, pressure, thermal measurements and their analysis lead to the ignition and combustion performances of the sample. Results exhibits a trend between ignition delay and the absorbed heat flux. After characterizing the laser beam and considering some laser-matter interaction, we present an analytical thermal model of ignition process. Furthermore, burning rate is presented as a function of the pressure inside the chamber. This trend combined with pressure signal during the combustion process, and compared to data obtained at higher pressure with closed vessel measurements, lead to a combustion model at low-pressure, from 1 MPa to 10 MPa.