RDX ignition flame structure

Quantitative CN, OH, and OH rotational temperature, and velocity two-dimensional profiles have been imaged using planar laser-induced fluorescence (PLIF) imaging or particle-imaging velocimetry (PIV) during ignition and deradiative extinguishment of cyclotrimethylene-trimitramine, (RDX) at three different heat flux levels. Relative NO₂ and NO profiles were also imaged with PLIF. Decomposition products, such as NO and NO₂ were formed early in the laser heating process and the gas plume moved, away from the surface. At a later time, ignition occurred in the gas phase, as evidenced by radical buildup such as CN and OH. This often showed as a spherical ignition kernel away from the surface. The flame then transitioned rapidly to a thin flame sheet that moved toward the surface. With longer heating times, laser-supported quasi-steady-state-deflagration develops as the flame sheet again moves somewhat further from the surface. This data can be used as an aide in the development of fully time-dependent RDX combustion models. The ignition and deradiative extinguishment data will help validate these time-accurate models, which can then be used to study combustion instability.