Modeling of turbulent spray combustion with application to diesel like experiment
Modeling of turbulent spray combustion with application to diesel like experiment
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DOI：
10.1016/s0010-2180(02)00340-1
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发表时间：
2002-05-01
影响因子：
4.4
通讯作者：
Borghi, R
中科院分区：
文献类型：
--
作者：
Demoulin, FX;Borghi, R
本文研究了喷雾内的湍流燃烧。实验和理论预测，燃料液滴的存在导致温度和当量比的波动增加。并且必须考虑这些波动以正确地估计平均反应速率。描述介质波动的一种简便方法是计算气相和液相所有波动变量的概率密度函数。将纯气体介质中概率密度函数（PDF）方程的推导方法推广到两相流中，采用分布函数形式的局部方程。液相的PDF包含表示分散和雾化的复杂的未封闭项。而不是建模这些条款，我们使用了随机拉格朗日模拟的液滴，采用经典的雾化模型，并假设球形液滴。该方法用于封闭出现在气体PDF方程中的蒸发项。气相的PDF方程可以通过使用蒙特-卡罗方法来求解，但是在这里，我们使用了基于混合物分数的假定PDF形状的更易处理的模型。利用MIL模型考虑了有限速率化学反应的影响，最后利用完整的模型对柴油机模型进行了自燃和火焰建立的模拟。对自燃延迟期和火焰形状进行了较好的模拟。考虑到液滴的波动的影响的重要性证明了通过测试模型与相应的条款。(C)2002年，燃烧研究所。
Turbulent combustion within sprays has been studied. Experiment and theory predict that the presence of fuel droplets leads to an increase in the fluctuations of temperature and equivalence ratio. and that these fluctuations must he considered to correctly estimate the mean reaction rate. A convenient way to describe the fluctuations of the medium is to compute the probability density function of all the fluctuating variables for the gas and liquid phases. The method used to derive the probability density function (PDF) equation,, in a pure gaseous medium was extended to two-phase flows by using the local equations written in terms of distribution functions. The PDF for the liquid phase contained complex unclosed terms representing dispersion and atomization. Instead of modeling these terms, we have used a stochastic Lagrangian simulation of the liquid droplets which employs classical atomization models and assumes spherical droplets. This method is used to close the vaporization terms which appear in the PDF equation for the gas. The PDF equation for the gas-phase could be solved by using a Monte-Carlo method but here we have used a more tractable model based on a presumed PDF shape for the mixture fraction. The effects of finite rate chemistry were taken into account by using the MIL model, Finally, the complete model was used to simulate auto-ignition and the establishment of a flame in a diesel type experiment. The auto-ignition delay and the shape of the flame were well simulated. The importance of taking into account the influence of the droplets on the fluctuations is demonstrated by testing the model with and without the corresponding terms. (C) 2002 by The Combustion Institute.