Mixture formation and combustion of biofuels in diesel engine

最新一代的柴油发动机通过其共轨喷射系统，在喷射正时方面具有极大的灵活性，并提供了使用多种喷射策略的机会。此外，考虑到燃料的生命周期，生物燃料或可再生燃料提供了减少温室气体排放的可能性。在这项研究计划中，建议研究多种喷射策略组合对不同生物燃料的影响，以评估这些燃料的真实潜力，并确定燃料性质对喷射策略的影响。因此，将在柴油发动机上进行试验。为了了解这些现象，并帮助解释发动机中观察到的行为，我们将在加压容器中进行实验以及大涡模拟(LES)。在加压容器中的实验将允许隔离不同的影响参数，并通过先进的光学诊断来查看它们对混合物形成过程的影响。这些后一种结果将有助于开发先进的发动机设计工具，例如用于预测多次喷射和基于初始燃油喷雾动量的燃油喷雾尖端穿透的关联式。大涡模拟与改进的雾化模型和多组分蒸发模型的实施相结合，可以研究混合气形成过程中的物理现象，从而为发动机中观察到的结果作为燃料性质和喷射策略的函数提供合理的解释。

The latest generation of diesel engines allow with its common-rail injection system a great flexibility in injection timing as well as offering the opportunity of using multiple injection strategies. Furthermore, biofuel or renewable fuels offer the possibility to reduce greenhouse gas emissions when the fuel life-cycle is considered. In this research program, it is proposed to study the impact of multiple injection strategy in combination to different biofuels as to evaluate the true potential of these fuels as well as identifying the impact of fuel properties on injection strategies, for example. Thus experiments will be conducted with a diesel engine. To gain an understanding of the phenomena at play and to help explaining the observed behavior in engine, experiments in a pressurized vessel as well as Large Eddy Simulations (LES) will be pursued. The experiments in the pressurized vessel will allow isolating different influencing parameters and to see their impacts on the mixture formation process through advanced optical diagnostics. These latter results will help develop advanced tools for engine design such as a correlation for predicting fuel spray tip penetration for multiple injection and based on the initial fuel spray momentum. LES in combination to the implementation of improved atomization model and multispecies evaporation model will allow studying the physical phenomena at play during the mixture formation process and will thus offer a rational explanation for the observed results in engine as a function of fuel properties and injection strategy.