Measurement of Temperature Profiles across Turbulent Combustion Layers in HE Fireballs

We studied optical emissions from fireballs created by the detonation of 25-g hemispherical charges. The charge was mounted on a 4-inch diameter steel rod to absorb the high detonation pressures and initiated by a RP-80 ignitor. The rod was flush mounted on a PMMA plate. As the hemispherical fireball expanded, it could be photographed both from the side and from underneath. Fireball gases turbulently mix with air, forming a turbulent combustion layer near the outer edge of the fireball. This was visualized using framing-camera photography; the thermal distribution across the emission front was measured using imaging spectroscopy and 3-color pyrometry. Both conventional and additively manufactured explosive charges were studied. Hydrocode simulations were also performed with our high-order Godunov code; the Thermodynamics of the gases was specified by a tabulated version of the Cheetah code. Computed temperatures agreed with the experimental temperature profiles. LLNL-ABS-832882