LASER-RECOIL COMBUSTION RESPONSE OF RDX

Combustion of RDX was studied under self-deflagrating and CO, laser-as sisted conditions at atmospheric pressure in air. Steady measurements included near-surface temperature (embedded microthermocouple), melt l ayer thickness, and sensitivity of burning rate to initial temperature and radiant flux. Unsteady measurements of oscillatory burning rate w ere also obtained using the laser-recoil technique. Thermocouple data showed a relatively thick (several hundred mu m) melt layer, which inc reased in thickness with increasing laser flux but remained at a relat ively constant temperature of about 650 K. The temporally fluctuating, spatially isothermal (time-averaged) nature of the melt layer suggest that a bubbling/mixing mechanism plays an important transport role in this zone. The temperature- and radiant flux-burning rate sensitivity data show that the equivalence principle is reasonably accurate for R DX under these conditions. The response function data agree qualitativ ely with those of Finlinson, et nl. The classical, quasisteady ZN mode l does not fit RDX combustion, at least at 1 arm, presumably due to co nditions in the melt layer (e.g., bubble-induced mixing) which violate model assumptions. Nevertheless these unsteady combustion data should be useful for validating more comprehensive RDX combustion models.