超臨界液滴燃焼過程の数値計算

概要

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Numerical calculation of the combustion process of a single fuel droplet immersed in an otherwise quiescent oxidizing gas whose pressure, P, exceeds the critical pressure of the fuel, P_<cF>, was performed. The burning time, t_b(P), takes a minimum value at P = P_<CF>. The underlying physics are that (i) at P< P_<CF>, for which the droplet has a liquid-gas interface throughout its lifetime, the gasification rate is controlled by the phase equilibrium condition, yielding decreasing t_b with increasing P; (ii) at P > P_<CF>, the droplet loses its surface immediately after ignition and the subsequent burning rate is controlled by the diffusion rates of the fuel and oxidizer, which yields increasing t_b because of the reduced diffusion coefficient with increasing P. To switch (i) to (ii) smoothly and continuously, the diffusion rate should be suppressed at around P= P_<CF>, which is accomplished under the condition of a vanishing diffusion coefficient at the critical state of the mixture. The behavior of gasification time is similar to that of the burning time, whereas it becomes minimum at a P significantly different from P_<CF> in the corresponding pure vaporization problem.
社団法人日本機械学会の論文
1993-11-25