Carbon combustion in the forward stagnation flowfield has been examined through experimental comparisons, by conducting\r\naerothermochemical analyses, with the surface C-O2 and C-CO2 reactions and the gas-phase CO-O2 reaction taken into account.\r\nBy virtue of the generalized species-enthalpy coupling functions, close coupling of those reactions has been elucidated. Explicit\r\ncombustion-rate expressions by use of the transfer number in terms of the natural logarithmic term, just like that for droplet\r\ncombustion, have further been obtained for the combustion response in the limiting situations. It has been confirmed that before\r\nthe establishment of CO flame, the combustion rate can fairly be represented by the expression in the frozen mode, that after\r\nits establishment by the expression in the flame-attached or flame-detached modes, and that the critical condition derived by\r\nthe asymptotics can fairly predict the surface temperature for its establishment. The formulation has further been extended\r\nto include the surface C-H2O and gas-phase H2-O2 reactions additionally, so as to evaluate the combustion rate in humid\r\nairflow. Since those expressions are explicit and have fair accuracy, they are anticipated to make various contributions not only\r\nfor qualitative/quantitative studies, but also for various aerospace applications, including propulsion with high-energy-density\r\nfuels.
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