Biodiesel fuels and the influence of multiple injection

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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.