Biodiesel fuels and the influence of multiple injection

拟议的研究计划将调查生物柴油混合燃料对多重喷射策略要求的影响，以优化发动机的污染物排放和性能。为此，建议以柴油共轨发动机为研究对象，通过实验研究喷射策略对常规和非常规污染物排放的影响。将对每种生物柴油混合物的喷射时机、喷射间隔时间和每次喷射时的质量百分比的影响进行评估。因此，将评估作为混合的函数的最佳注射策略。为了更好地了解多次喷射对混合气形成过程的影响，建议在密闭容器的控制环境下，利用高速摄像和激光荧光技术研究喷射过程，以确定喷嘴的穿透深度、液滴尺寸和区分液相和汽相。为了更好地了解混合燃料性质对喷雾形成过程的影响，还将进行数值模拟。首先，模拟将再现封闭的容器实验，从而验证数值模型。模拟将包括考虑到燃料的真实性质的多组分燃料模型。在最后一步中，将进行发动机3D模拟，以再现发动机试验，并量化燃料性质对三喷策略发动机混合气形成过程的影响。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。为了实现这一点，复制了共轨系统的1D模型，并将其耦合到3D气缸模拟。最后，模拟将允许混合气形成过程和缸内流动的耦合，并帮助识别必须具有能够最大限度地减少污染物排放并有利于混合气形成过程和燃烧的燃料特性。

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.