醇类柴油混合燃料直喷压燃超临界转捩及混合气形成机理研究

醇类柴油混合燃料用于发动机以能部分替代石化燃料且有极大提升其燃烧排放性能的潜力而备受关注，面对当前压燃发动机高喷射压力、高增压的发展趋势，醇类柴油混合燃料极易发生超临界蒸发及转捩现象，但醇类与柴油的分子极性差异问题的复杂性使得其超临界转捩及混合气形成机制不清，研发极富挑战。对此，本项目提出将分子动力学自由能微扰法与相变时系统亥姆霍兹自由能最小理论相结合的新方法，准确反映界面传热传质动态特性对转捩的影响，发展醇类多元系统超临界转捩判据，建立不同精度状态方程的映射，探索非平衡分子动力学、吉布斯和等温等压闪蒸理论的结合，揭示分子极性对含醇多元系统超临界转捩及非平衡效应的影响机制，构建高精度醇类混合燃料蒸发模型，结合高温高压环境中超临界喷雾试验，揭示醇类柴油混合燃料超临界混合气形成机理，为醇类柴油在压燃发动机上的高效清洁应用提供理论支撑，研究也将对多组分燃料蒸发理论的发展具有重要的学术价值。

Alcohol-diesel blends are used in engines to partially replace fossil fuels and have the potential to greatly improve their combustion and emission performances. Facing with the current development trend of high injection and boosting pressures of compression ignition engines, supercritical evaporation and transition are prone to occur for alcohol-diesel blends, however, the complexity of the molecular polarity difference between alcohols and diesel makes the supercritical transition and mixture formation mechanism unclear, making the researches extremely challenging. To this end, the present project proposes a new method that combines the molecular dynamics based free energy perturbation (FEP) and the minimum Helmholtz free energy theory when phase transition happening, which could accurately reflect the effects of the dynamics interfacial heat and mass transfer on transition characteristics, develop the supercritical transition criterion for alcohol-containing multi-systems, establish the mapping of different precision state equations, explore the combination of non-equilibrium molecular dynamics, Gibbs and isothermal-isobaric (TP) flashing theory, reveal the influential mechanism of molecular polarity on the supercritical transition and non-equilibrium effect of alcohol-containing multi-systems, build a high-fidelity blended fuel evaporation model, combine with supercritical spray tests in a high temperature and pressure environment, reveal the mixture formation mechanisms of alcohol-diesel blends under supercritical conditions, provide theoretical support for the efficient and clean applications of the alcohol-diesel blends on compression ignition engines, and will also have important academic value for the development of multi-component fuel evaporation theory.