Relationship between empirical laws of turbulent combustion of dust/air mixtures

Abstract

Introduction. An array of known experimental data, mainly obtained in a standard 1 m3 chamber, is considered in the article. It allowed to identify the nature of three dependences of the turbulent combustion of dust, including the dependences of limited oxygen concentration (LOC) and explosive index Kst on the energy of ignition source Eig (on a logarithmic scale) and the dependence of Kst on the initial oxygen content in the air Cox.Empirical dependencies. The analysis showed that all considered dependences, having a relative accuracy of about 20 % can be represented as linear functions of an argument varying within the following limits: Eig varies from minimum ignition energy Emin to 10 kJ; Cox ranges from LOC to 21 % vol. According to the nature of dependence of Kst on Eig, all dusts are divided into two types. For the first type of dust, Kst does not depend on Eig. For the dust of the second type, Kst ∝ (Eig – Emin).Relationship of empirical dependencies. It is shown that the considered empirical dependences should be interrelated for the dust of the second kind. Namely, slopes Cn (n = 1, 2 or 3 as the number of the dependence) of linear functions, approximating the empirical dependences for a particular dust sample, satisfy the relationship: С2(21 vol. %) = –С1∙С3(10 kJ). Due to the absence of a dust sample, for which data on all three dependences are available, the obtained relationship was confirmed for the average values of parameters: <С2(21 vol. %)> = =–<С1>∙<С3(10 kJ)>.Discussion of the result. The satisfactory accuracy of the relationship between C1, C2 и C3 gives rise to the confidence in the objectivity and relationship of the considered empirical dependences of the turbulent combustion of dust.Conclusions. It is shown that the considered empirical dependences of the turbulent combustion of dust in a 1 m3 chamber are interrelated and the form of this relationship is identified.