Optical investigation on the interaction between a fuel-spray and an oil wetted wall with the focus on secondary droplets

Abstract

Since the technology of direct injected engines has become more and more prevalent, combustion anomalies such as pre-ignition events have been occurring with increasing frequency. The interaction between the fuel-spray and the oil wetted cylinder liner is considered to be a partial cause for these phenomena. The incoming fuel jet can lead to a detachment of secondary droplets, which may affect pre-ignition events due to their changed flammability properties. To characterize these secondary droplets, spatially and temporally highly resolved optical investigations on the fuel-oil-film-interaction are carried out in this work. Using laser induced fluorescence and two high-speed cameras both fluids are optically separated. Thereby the secondary droplets can be detected and characterized in size, velocity vector, and composition.