Critical condition for the particle combustion of carbon, being sustained in a cold environment
Critical condition for the particle combustion of carbon, being sustained in a cold environment
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碳颗粒燃烧的临界条件，在寒冷环境中持续
DOI：
10.1016/j.combustflame.2016.06.004
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发表时间：
2016
影响因子：
4.4
通讯作者：
A. Makino
中科院分区：
文献类型：
--
作者：
A. Makino
为了研究碳燃烧的可持续性，已经尝试获得热粒子浸没在冷环境中的临界条件，这种情况在吸气式火箭发动机中也会遇到。主要关注的是颗粒燃烧的下限，小于ca。100 μm的直径，虽然不仅下限，而且临界条件的上限已经获得。通过进行渐近分析，重点放在一个平台阶段，其中颗粒温度保持其初始值，已获得的解析表达式的下限的颗粒直径，作为函数的压力比，氧气的质量分数，和/或初始温度。从解析解中还得到了一个近似表达式。结果表明，解析表达式和近似表达式在趋势和近似量级上都能较好地反映数值结果。此外，已使用的综合参数，包括颗粒直径和压力比的Arcadius图，以确定区域的颗粒燃烧要持续。还进行了比较，使用文献中的实验数据，提出了一个公平的程度的协议，就趋势和近似的幅度而言。已经证实，该配方已经捕获了基本特征，即颗粒尺寸的减小不一定有利于颗粒燃烧，并且当颗粒直径减小到临界值时，表面反应停止被激活。
In order to examine sustainability of carbon combustion, an attempt has been made to obtain its critical condition for a hot particle, being immersed in a cold environment, situation of which is also encountered in an air-breathing rocket-engine. Main concern has been put on particle combustion in the lower limit, less than ca. 100 µm in diameter, although not only the lower limit but also the upper limit of the critical conditions has been obtained. By conducting asymptotics, with focusing on a plateau stage in which particle temperature keeps its initial value, an analytical expression has been obtained for the lower limit of the particle diameter, as functions of the pressure ratio, oxygen mass-fraction, and/or initial temperature. An approximate expression is also obtained from the analytical solution. It is found that both the analytical and approximate expressions can fairly represent the numerical results, as far as the trend and approximate magnitude are concerned. In addition, use has been made of the Arrhenius plot of a comprehensive parameter, consisting of the particle diameter and pressure ratio, in order to identify regions for the particle combustion to be sustained. Comparisons have also been conducted by use of experimental data in the literature, with presenting a fair degree of agreement, as far as the trend and approximate magnitude are concerned. It has been confirmed that the formulation has captured the essential feature, that the reduction in particle size does not necessarily favor the particle combustion, and that the surface reaction ceases to be activated when the particle diameter is reduced to the critical value.