Modelling of gasoline fuel droplets heating and evaporation
Modelling of gasoline fuel droplets heating and evaporation
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DOI：
10.1016/j.fuel.2015.06.028
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发表时间：
2015-11
期刊：
影响因子：
7.4
通讯作者：
Mansour Al Qubeissi;S. Sazhin;J. Turner;S. Begg;C. Crua;M. Heikal
中科院分区：
文献类型：
--
作者：
Mansour Al Qubeissi;S. Sazhin;J. Turner;S. Begg;C. Crua;M. Heikal
本文提出了一种新的方法来模拟汽油燃料液滴的加热和蒸发，并具体应用于内燃机的代表性条件。汽油中一些化学配方相同、热力学和输运性质相近的成分被特殊成分取代，从而使汽油燃料的原始成分（83种成分）减少到只有20种成分。此外，在多维准离散（MDQD）模型中，对含有这些成分的汽油组成的近似被更少数量的假设准成分/成分所取代。该模型考虑了液相中准组分和单组分的瞬态扩散以及液滴与周围空气相对速度引起的温度梯度和液滴内部的再循环。在原来的MDQD模型中，正构烷烃和异构烷烃被认为是一类烷烃。在这个新的方法中，这两个群体的贡献是分开考虑的。初始模型参数的值是从燃烧前在研究发动机上测量的实验数据中选择的。结果与单组分模型的预测结果进行了比较，在单组分模型中，组分的输运和热力学性质是平均的，忽略了物质的扩散，假设液体导热系数无穷大，或近似于异辛烷的导热系数。结果表明，考虑到20个组分的贡献，与使用离散组分模型相比，后一种模型的应用导致液滴蒸发时间的预测分别低约67%（平均）和47%（异辛烷）。结果表明，在相同发动机条件下，使用MDQD模型以6个准组分/组分近似汽油燃料的实际组成，导致液滴表面温度和蒸发时间的估计分别低于约0.9%和6.6%。与考虑汽油燃料的所有20种成分的模型相比，后一种模型的应用导致CPU处理器时间减少了大约70%。
The paper presents a new approach to modelling of the heating and evaporation of gasoline fuel droplets with a specific application to conditions representative of internal combustion engines. A number of the components of gasoline with identical chemical formulae and close thermodynamic and transport properties are replaced with characteristic components leading to reducing the original composition of gasoline fuel (83 components) to 20 components only. Furthermore, the approximation to the composition of gasoline with these components is replaced with a smaller number of hypothetical quasi-components/components as previously suggested in the multi-dimensional quasi-discrete (MDQD) model. The transient diffusion of quasi-components and single components in the liquid phase as well as the temperature gradient and recirculation inside the droplets, due to the relative velocities between the droplets and the ambient air, are accounted for in the model. In the original MDQD model, n-alkanes and iso-alkanes are considered as one group of alkanes. In this new approach, the contributions of these two groups are taken into account separately. The values for the initial model parameters were selected from experimental data measured in a research engine prior to combustion. The results are compared with the predictions of the single-component model in which the transport and thermodynamic properties of components are averaged, diffusion of species is ignored and liquid thermal conductivity is assumed to be infinitely large, or approximated by those of iso-octane. It is shown that the application of the latter models leads to an under-prediction of the droplet evaporation time by approximately 67% (averaged) and 47% (iso-octane), respectively, compared to those obtained using the discrete component model, taking into account the contributions of 20 components. It is shown that the approximation of the actual composition of gasoline fuel by 6 quasi-components/components, using the MDQD model, leads to an under-prediction of the estimated droplet surface temperatures and evaporation times by approximately 0.9% and 6.6% respectively, for the same engine conditions. The application of the latter model has resulted in an approximately 70% reduction in CPU processor time compared to the model taking into account all 20 components of gasoline fuel.