STUDY OF THE MECHANISM OF OSCILLATORY SOLID-PHASE COMBUSTION BY A NONLINEAR CHEMICAL KINETIC-MODEL

Oscillatory solid-phase pyrotechnic combustion in the following system NH4ClO4 + Mg (powder) + K2Cr2O7 is studied, where NH4ClO4, Mg and K2C r2O7 are the oxidant, reducing agent and frequency-modulating species, respectively, in order to elucidate a more detailed description of th e oscillatory mechanism. The simplicity of this pyrotechnic system ser ves our purposes very well. It is shown that the combustion of the abo ve system is highly oscillatory in nature. Once ignited, the mixture e xhibits 'pulsed burning', the intensity of the combustion varying peri odically between flash combustion (deflagration) and smokeless smoulde ring. A number of experiments were carried out which confirmed that th e phenomenon is intrinsic and that the controlling process chemical in nature. According to the results of the experiments and the observed combustion phenomena, the following chemical kinetic mechanism for the oscillatory process is suggested [GRAPHICS] It is considered that the competiting reactions between the three phases of Mg with the oxidiza ble gases produced by the decomposition of NH4ClO4 control the oscilla tory burning process. Based on this analysis, the following simplified qualitative chemical kinetical model is proposed [GRAPHICS] and kinet ic equations are deduced. The results of the simulation of the autocat alytic model using non-linear numerical methods are reported and discu ssed. Steady-state solution and oscillatory behaviour is obtained, in good agreement with experimental phenomena.