柴油-生物柴油混合喷雾过程的多组分蒸发模拟

Multi-Component Vaporization Modeling of Diesel-Biodiesel Spray Processes

针对多组分混合燃料的喷雾过程研究了相应的液滴蒸发模型,着重于研究混合燃料的组分对其液滴蒸发特性的影响.对柴油-生物柴油混合燃料的液滴蒸发模拟,依据燃料本身的特点,分别采用连续热力学方法和离散组分法描述其中柴油和生物柴油的组成.利用所得模型,对单组分燃料、双组分燃料以及生物柴油的液滴进行了蒸发模拟,通过将液滴蒸发历史曲线与试验结果对比,发现对于这些燃料液滴的蒸发模拟结果与相应试验数据很好地吻合,证实了此混合燃料液滴蒸发模型的正确性.此外,还着重对柴油-生物柴油的混合燃料的液滴进行了蒸发模拟研究,探讨混合燃料成分对其液滴蒸发特性的影响.结果表明:轻质柴油组分在蒸发过程中优先蒸发,而相对重质的柴油组分的蒸发则相对滞后,生物柴油在混合燃料中的质量分数则在液滴蒸发过程中不断增加,随着重质组分在柴油中所占比例达到一定程度之后,生物柴油的质量分数则开始迅速减小.

A numerical model to predict the vaporization characteristics of multi-component fuel mixtures under en- gine operation conditions was developed in this study. The fuels studied include those of single-component, binary- component, biodiesel, and diesel-biodiesel. A hybrid drop vaporization model, which uses continuous thermody- namics to describe diesel fuel and discrete components to represent biodiesel, was developed. The hybrid model was validated using the experimental data of n-heptane/n-decane mixture and was also applied for pure n-heptane drops under various ambient temperatures. Good levels of agreement between the predicted and experimentally measured drop size histories were obtained. During drop vaporization, slighter components of diesel fuel vaporize earlier, and biodiesel components do not vaporize until some later time during the vaporization process. Furthermore, in modeling the diesel-biodiesel drop, results show that the drop lifetime increases with the biodiesel concentration in the blend.