Particle combustion of solid carbon in the quiescent environment has been overviewed by use of accomplishment in the aerothermochemical analyses, in which not only the surface C-O2 and C-CO2 reactions but also gas-phase CO-O2 reaction is taken into account, until use has been made of an examination related to the critical size of the particle activation and/or extinction. By virtue of the generalized species-enthalpy coupling functions, close coupling of those reactions has been elucidated. It has been identified that the combustion behavior in the three limiting situations, such as the Frozen, Flame-sheet, and Flame-attached modes, can analytically be described. Explicit combustion-rate expressions by use of the transfer number in terms of the natural logarithmic term, just like that for droplet combustion, have further been obtained for the combustion behavior in the limiting situations, albeit approximate. In addition, by examining establishment of the CO-flame over a carbon particle, it has been confirmed that the combustion rate can fairly be represented by the expression in the Frozen mode when the particle diameter is 100 µm or less. Using this confirmation, combustion response in the transient situation has further been examined, from which an existence of the critical size for the particle activation has even been derived, by use of the asymptotics. Furthermore, an attempt has been conducted to obtain the critical size for the particle extinction, presenting the maximum and the minimum as particle temperature rises. It is suggested that those particles larger than the maximum value can only be activated to burn and others are extinguished. In addition, those burned during combustion are extinguished when particle sizes are smaller than the minimum value. A fair degree of agreement in experimental comparisons indicates that the present formulation has captured the essential feature of the particle activation and/or extinction.
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