Solid materials combustion study by microthermocouples

Applications of thermocouples in the study of the processes associated with the combustion or degradation of solid materials allow to define important parameters characterizing the phenomena. Generally, the choice of the appropiated thermocouples (materials and size) depends on the features of the process under study; nevertheless steady and dynamic calibrations are always necessary in order to apply correctly this diagnostics. In this: work tests have been carried out utilising thermocouples (Pt-Pt 10% Rh type) made by wires having 5-50 mu m diameter in order to analize different combustion aspects' regarding energetic solid materials utilized in aerospace applications. In fact solid rocket propellants, used in boosters, have been widely studied by this diagnostics in order to obtain information about the heating, ignition, oscillatory combustion, steady state combustion, extinction and reigniton phenomena and thus to point their differencies out. As solid propellants are generally loaded in metallic case covered by insulator materials it is important to know the decomposition features of these thermal protections in order to valuate the thickness which guarantees the proper insulation effect. Thus measurements of the temperatures in the solid or on the heated surface have been done while the penetration depth, associated with different heating times at the maximum avaible energy, have been obtained. The study of the ignition and the steady combustion, sustained by radiant energy, of graphite spheres has allowed to measure the ignition and combustion temperature while the burning surface regression rate has been calculated from the diameter decrease. Finally, studies concerning the ignition process associated with the combustion synthesis of powders have been carried out to indicate the operating conditions which guarentee the ignition (by radiant energy) followed by autopropagating combustion.