Entropy balance and exergy analysis of the process of droplet combustion
Entropy balance and exergy analysis of the process of droplet combustion
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DOI：
10.1088/0022-3727/31/13/015
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发表时间：
1998-07-07
影响因子：
3.4
通讯作者：
Som, SK
中科院分区：
文献类型：
--
作者：
Hiwase, SD;Datta, A;Som, SK
对液体燃料液滴在高温静止气体环境中的燃烧过程进行了熵平衡和火用分析，以确定该过程的第二定律效率。相应地，从质量守恒方程、动量守恒方程和热守恒方程的数值解出发，计算了气相的速度场和组分浓度场以及气相和液滴相的温度场。从广义熵输运方程出发，确定了气相输运过程和化学反应产生的熵的速率。建立了液滴燃烧过程(火用)分析的理论模型，以便根据有关的控制参数，即自由流与初始液滴温度之比和初始Damkohler数来预测第二定律效率。在一个典型的扩散控制的液滴燃烧过程中，化学反应的速度远远快于热、质量和动量的扩散速度，相反，化学反应的不可逆率比扩散过程的不可逆率低。对于液滴燃烧过程，从能量节约和有效能量利用的热力学角度来看，对于液滴燃烧过程，应选择较低的初始Damkohler数尽可能接近其启动点火的极限值)和较高的自由流温度。
An entropy balance and subsequent exergy analysis of the process of combustion of a liquid fuel droplet in a quiescent gaseous surrounding at high temperature has been performed in order to determine the second-law efficiency of the process. Velocity and species concentration fields for the gas phase and the temperature field both for the gas and for the droplet phases have been evaluated from the numerical solution of the equations of conservation of mass, momentum and heat, accordingly. The rate of generation of entropy due to transport processes and chemical reaction in the gas phase has been determined from the generalized entropy transport equation. A theoretical model for exergy analysis of the process of droplet combustion has been developed in order to predict the second-law efficiency in terms of the pertinent controlling parameters, namely, the ratio of free stream to initial droplet temperatures and the initial Damkohler number. It has been observed that, in a typical diffusion-controlled droplet combustion process, in which the rate of chemical reaction is much faster than the rates of diffusion of heat, mass and momentum, the irreversibility rate has, in contrast, a lower value due to chemical reaction than that due to diffusion processes taken together. A low value of the initial Damkohler number las close as possible to its limiting value for initiation of ignition) and a high value of free stream temperature should be preferred for the process of droplet combustion from the viewpoint of energy economy in relation to thermodynamic utilization of available energy.