ONSET OF CONVECTIVE BURNING IN PICRIC ACID

Based on simultaneous optical registration and measurement of the pres sure at several points along the height of a sample, we have studied t he onset of convective burning in picric acid when it is ignited from a closed end. We have investigated the effect of the particle size and density of the explosive (0.7-1.1 g/cm(3)), the height of the sample, the power of Me igniter, and the parameters of the channel in the she ll. We have obtained the spatial profiles of the pressure distribution . We have determined the dependence on the investigated parameters of the critical height of the bed at which convective burning begins. We have determined two typical cases realized in the initial stage of dev elopment of the process. For one case, a smooth increase in pressure b efore and after the luminosity front is characteristic; for the other case, the presence of a peaked pressure distribution close to the fron t is characteristic. We have established the conditions under which a specific case is realized. We suggest an explanation for the results o btained.