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Flexible and multiple injections are an important strategy to fulfill today's exhaust emission regulations. To optimize injection processes with an increasing number of adjustable parameters knowledge about the basic mechanisms of spray breakup, propagation, evaporation and ignition is mandatory. In the present investigation the focus is set on spray formation and ignition. In order to simulate current diesel-engine conditions measurements were carried out in a high-temperature (1000 K) and high-pressure (10 MPa) vessel with optical accesses. A piezo servo-hydraulic injector pressurized up to 200 MPa was used to compare four single injection durations and four multi-injection patterns in the ignition phase. All measurements were performed with CEC RF-03-06, a legislative reference fuel. For the spray measurements, a program of 16 to 18 different operating points was chosen to simulate engine conditions from cold start to full load.

The nozzle geometry of fuel injectors has a strong influence on turbulences and pressure gradients within the nozzle flow. The flow situation at the nozzle outlet determines the spray propagation into the ambient atmosphere. This spray penetration is critical for gasoline direct injection (GDI) systems. When the spray penetration is too high, it can cause wall and cylinder impingement, which increases particle emissions drastically. However, prediction of fuel spray propagation in dependency of nozzle hole geometry is difficult due to the large difference in scale between the nozzle flow and the spray development. Because of this, spray measurements with varying nozzle geometry parameters and statistical evaluation of these datasets are useful for the future development of fuel injectors. In this study, shadowgraphy measurements of real-size single-hole glass nozzles are presented. The nozzles cover a wide range of geometry parameters relevant to a GDI system.

In DISI engines spray distribution and atomization directly influence mixture formation, the quality of combustion and the resulting emissions. Constant Volume Chambers (CVC) are commonly used to characterize sprays of gasoline injectors. The CVCs provide good optical access but the flow condition of the engine cannot be reproduced. Optically accessible engines in contrast deliver realistic flow conditions but have restricted optical access. In former investigations we compared the spray propagation of different injectors in constant volume chambers and in optical accessible engines. These results showed a clear difference of the spray propagation in the CVC and the engine, especially at high charge motion conditions in the engine. To find an appropriate way to investigate the impact of different charge motion a flow channel was built with adjustable crossflow velocities from 5-50 m/s. The spray propagation during the injection process was measured with high-speed shadowgraphy.