Burning and Extinction of a Laser‐Ignited Carbon Particle in Quiescent Mixtures of Oxygen and Nitrogen

Abstract

Experimental data on the burning mode and lifetime, on the surface temperature, and on the spontaneous extinction of a laser‐ignited particle of electrode carbon (50–200μ) in quiescent mixtures of oxygen and nitrogen at room temperature are presented. The test variables were the oxygen mass fraction (0.5–1) and the pressure (0.5–3 atm) of the mixture. High speed cinemicrography of the burning particle showed that the visible combustion zone was restricted to the surface. Two theoretical models, one neglecting the dissociation of oxygen and the other including it approximately, are developed in order to explain the extinction phenomenon. Comparison of the extinction results computed from these models with the data indicates that the model neglecting dissociation is the preferred one. Based on this model it is shown that the kinetics of oxidation of electrode carbon in the temperature range 2000°–3500°K can be represented by an effective Arrhenius surface oxidation reaction producing and having an activation energy of 18 kcal/mole and an order in the range 0.5–1.