Biodiesel fuels and the influence of multiple injection

拟议的研究计划将调查生物柴油混合物对优化发动机污染物排放和性能的多重喷射策略要求的影响。为此，提出在柴油共轨发动机上实验研究喷射策略对调节和不调节污染物排放的影响。将对每种生物柴油混合物进行注射时间、注射间隔时间和每次注射时注射的质量百分比的影响评估。因此，最佳注射策略作为混合的函数将被评估。为了更好地了解多次注射对混合物形成过程的影响，提出在密闭容器的控制环境下，利用高速相机成像和激光荧光技术研究注射过程，以确定喷雾尖端的穿透度、液滴的大小，并区分液相和气相。为了更好地了解混合燃料特性对喷雾形成过程的影响，还将进行数值模拟。首先，模拟将重现密闭容器实验，从而验证数值模型。模拟将包括考虑到燃料真实性质的多组分燃料模型。在最后一步中，我们将进行发动机3D模拟，以重现发动机实验，并量化燃料特性如何影响三次喷射策略下发动机的混合气形成过程。此外，模拟还将包括共轨系统对喷射过程的流体动力学影响。为了实现这一目标，共轨系统的一维模型被复制并耦合到三维圆柱体模拟。最后，模拟将允许混合形成过程和缸内流动的耦合，并帮助确定必须具有的燃料特性，可以最大限度地减少污染物排放，有利于混合形成过程和燃烧。

The proposed research program will investigate the influence of biodiesel blends on the multiple injection strategy requirement that optimise engine pollutant emission and performance. To do so, it is proposed to study experimentally with a diesel common-rail engine how the injection strategy influence regulated and unregulated pollutant emissions. Assessment of the influence of injection timing, time between injection and percentage of mass injected at each injection will be pursued for each biodiesel blends. Therefore optimum injection strategy as a function of blend will be assessed. To gain a better insight at how the multiple injection affects the mixture formation process, it is proposed studying under the control environment of a closed vessel the injection process with high speed camera imaging and laser fluorescence as to determine spray tip penetration, droplet size and to distinguish the liquid and vapour phases. To gain a better insight at the influence of the blended fuel properties on the spray formation process, numerical simulations will also be achieved. First, the simulation will reproduce the closed vessel experiments allowing a validation of the numerical model. The simulations will include a multicomponent fuel model taking into account the true nature of the fuel. In the last step, engine 3D simulations will be pursued to reproduce the engine experiment and to quantify how the fuel properties influence the mixture formation process in engine with a triple injection strategy. Furthermore, the simulations will include the fluid dynamic effect of the common-rail system on the injection process. To achieve this, a 1D model of a common-rail system is reproduced and coupled to the 3D cylinder simulations. Finally, the simulation will allow the coupling of the mixture formation process and in-cylinder flow and help identify must have fuel properties that can minimize pollutant emissions and favor the mixture formation process and combustion.