Modeling temperature distribution inside an emulsion fuel droplet under convective heating: A key to predicting microexplosion and puffing
Modeling temperature distribution inside an emulsion fuel droplet under convective heating: A key to predicting microexplosion and puffing
复制标题
DOI：
10.1615/atomizspr.2015013302
复制
发表时间：
2016
影响因子：
1.2
通讯作者：
J. Shinjo;J. Xia;A. Megaritis;L. Ganippa;R. Cracknell
中科院分区：
文献类型：
--
作者：
J. Shinjo;J. Xia;A. Megaritis;L. Ganippa;R. Cracknell
摘要微爆/膨化是指油包水型乳化液液滴在过热水的作用下发生爆炸沸腾而迅速解体的过程。为了预测微爆/膨化，模拟对流加热下的乳液液滴内部的温度分布是一个先决条件，因为温度场决定了成核的位置（从过热水中产生蒸汽泡）。在本研究的第一部分中，典型的燃烧室条件下的油包水乳化液滴的对流加热进行了研究，使用高保真模拟，以准确地模拟内部液滴的温度分布。由于环境空气流产生的剪切力引起液滴内部的内循环。已经发现，对于本研究中所研究的液滴，液体Peclet数PeL处于100<PeL<500的过渡区域。因此，温度场在一定程度上被速度场扭曲，但这种扭曲不足以形成温度场的希尔涡流。在本研究的第二部分中，提出了一种新的方法来模拟温度场的失真，通过引入的热导率和偏心率的温度场的角度依赖性。该模型能够再现乳化液滴内部温度场的主要特征，并可用于预测微爆/膨化的关键初始条件--成核位置。
Abstract Microexplosion/puffing is rapid disintegration of a water-in-oil emulsion droplet caused by explosive boiling of embedded superheated water sub-droplets. To predict microexplosion/puffing, modeling the temperature distribution inside an emulsion droplet under convective heating is a prerequisite, since the temperature field determines the location of nucleation (vapor bubble initiation from superheated water). In the first part of the present study, convective heating of water-in-oil emulsion droplets under typical combustor conditions is investigated using high-fidelity simulation in order to accurately model inner-droplet temperature distribution. The shear force due to the ambient air flow induces internal circulation inside a droplet. It has been found that for droplets under investigation in the present study, the liquid Peclet number PeL is in a transitional regime of 100<PeL<500. The temperature field is therefore somewhat distorted by the velocity field, but the distortion is not strong enough to form Hill’s vortex for the temperature field. In the second part of the present study, a novel approach is proposed to model the temperature field distortion by introducing angular dependency of the thermal conductivity and eccentricity of the temperature field. The model can reproduce main features of the temperature field inside an emulsion droplet, and can be used to predict the nucleation location, which is a key initial condition of microexplosion/puffing.