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Modern concepts of downsized DI gasoline engines set up high requirements on the injection system to meet the emission targets. The fundamental knowledge and understanding of spray propagation physics are essential for the development of nozzles and injection strategies, due to reduced displacements in combination with the continuing trend of elevated fuel pressures. A detailed analysis of micro- and macroscopic spray parameters was carried out using a multihole solenoid driven DI injector. The measurements were performed in a continuously scavenged pressure chamber with full optical access. Fuel pressure up to 38MPa and backpressures in a range from 0.03 - 0.2 MPa were varied. Optical investigations were done by Shadowgraphy imaging and Phase Doppler Anemometry. The combination of micro- and macroscopic spray results are used to discuss the propagation behaviour of gasoline spray.

Understanding the causal loop from injection to combustion in modern direct injection engines is essential to improve combustion and reduce emissions. In this work, the section from injection to fuel-evaporation in this causal loop was investigated using different optical measurement techniques, with a focus on drop size measurements using Phase Doppler Anemometry (PDA). One spray jet of a modern DISI multi-hole injector was investigated using gasoline RON 95 fuel and two single component alkane fuels (n-hexane / n-decane). In a first step the macroscopic spray formation and propagation of this spray jet were studied using a 2D-Mie-scattering technique in an optical injection chamber at homogenous charge DISI conditions. Furthermore, the droplet size distribution and mean diameter were determined spatially and temporally resolved for an ambient pressure of 0.3MPa and different ambient temperature (323K / 423K / 523K) conditions in the optical chamber using Phase Doppler Anemometry.

The fuel spray behavior in the near nozzle region of a gasoline injector is challenging to predict due to existing pressure gradients and turbulences of the internal flow and in-nozzle cavitation. Therefore, statistical parameters for spray characterization through experiments must be considered. The characterization of spray velocity fields in the near-nozzle region is of particular importance as the velocity information is crucial in understanding the hydrodynamic processes which take place further downstream during fuel atomization and mixture formation. This knowledge is needed in order to optimize injector nozzles for future requirements. In this study, the results of three experimental approaches for determination of spray velocity in the near-nozzle region are presented. Two different injector nozzle types were measured through high-speed shadowgraph imaging, Laser Doppler Anemometry (LDA) and X-ray imaging.