Estimation of the temperature of starch particles-air flames
Résumé
If the ability of reactive solid particles to give rise to combustible mixtures when they are finely dispersed in an oxidizing gas is well known since a long time, the actual mechanisms governing the propagation of combustion in this kind of reactive mixtures is far from being well understood. The reason for this is an insufficient knowledge of the fundamental properties of characteristic parameters of dust flames. To progress in the prediction of dust explosion hazards and of their effects, substantial fundamental results concerning the structure and properties of dust flames are needed. Many works have been devoted to the measurement of the explosion pressure of dust air mixtures inside closed vessels and to try to derive the combustion rate from pressure evolution as function of time. In spite of the interest of this method of investigation, due to the simplicity of carrying out experiments, it does not permit to have a direct access to the measurement of the characteristic parameters of the reaction zone and to investigate its structure. As a result, several researchers have undertaken the study of flame propagation in tubes. In previous papers, we have described an experimental method to study the propagation of a flame at constant pressure, displayed original results in the case of laminar starch particles-air flames , and discussed the possibility to derive the laminar burning velocity from the registration of the parameters of a freely propagating laminar flame. However, despite the interest of these new results concerning the flame shape or fundamental parameters, such as the laminar burning velocity, the quenching distance,...the information to our disposal is yet insufficient to permit a correct description of a dust flame. Indeed, progression in this domain is dependent on the knowledge of another fundamental parameter of the flame which is the temperature. But, until now, we have only rough and contradictory results about the temperature of dust-air flames, as a result of the great difficulties to perform experiments of direct measurements of the temperature in this kind of reactive systems. We expose, hereafter, the first effort made to acquire new and original experimental results on this problem.
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