Second law analysis of convective droplet burning
Second law analysis of convective droplet burning
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对流液滴燃烧第二定律分析
DOI：
10.1016/0017-9310(92)90099-e
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发表时间：
1992
影响因子：
5.2
通讯作者：
I. Puri
中科院分区：
文献类型：
--
作者：
I. Puri
考虑了气体流中粒子燃烧产生的熵，并对其贡献进行了比较。第二定律分析是为了最小化熵的产生，从而减少可用功的损失。从这一有利的热力学角度确定了低雷诺数下燃烧液滴的最佳流动条件，并获得了最佳传递数。这样得到的传递数直接取决于相对速度的平方，而与燃烧产生的净焓升和环境温度与火焰温度之比成反比。在实际流动中，传递数和净热量释放是固定的，这些量与相对速度和环境与火焰的温度比有关，以便在最佳条件下运行。在这种流动中，相对速度的平方只占净热释放的一小部分，因此，为了在最佳热力学条件下运行，可以确定液滴雷诺数必须很大，这表明液滴尺寸大，气体粘度低。还考虑了与工程实践有关的情况，并得出结论，在约束条件下，实践与第二定律分析的含义是一致的。
The entropy generation due to burning particles in a gaseous stream is considered and the contributions to it compared. A second law analysis is undertaken in order to minimize the entropy generation and, therefore, the lost available work. The optimum flow conditions from this thermodynamically advantageous perspective are determined for a burning droplet at low Reynolds number and an optimum transfer number obtained. The transfer number so obtained depends directly on the square of the relative velocity, and inversely on the net enthalpy rise due to burning and the ratio of ambient to flame temperature. In realistic flows, where the transfer number and net heat release are fixed, these quantities are related to the relative velocity and ambient to flame temperature ratio in order to operate at optimum conditions. The square of the relative velocity in such flows is a small fraction of the net heat release so that, to operate at optimum thermodynamic conditions, it is determined that the droplet Reynolds number must be large suggesting a large droplet size and low gas viscosity. Circumstances pertaining to engineering practice are also considered and it is concluded that within constraints practice is consistent with the implications of the second law analysis.