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Velocity Field Measurements with High Speed Structural Image Velocimetry in the Primary Atomization Region of Future Diesel Fuels
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on September 15, 2020 by SAE International in United States
Fuel spray breakup in combustion engines and hence all following processes are determined by the primary atomization. Due to high optical densities as well as high spray velocities and structures in the µm-range, the measurement of the first millimeters after the nozzle outlet is extremely challenging. Therefore, the processes of the primary breakup are not fully understood yet, although these processes are very important for simulation of spray atomization. One important spray characteristic is the velocity distribution close to the nozzle outlet. For this reason, the Structural Image Velocimetry (SIV) was developed to be able to visualize spray structures in the near nozzle region and track them via cross-correlation algorithms providing two-dimensional velocity fields of the spray. The basic principle of the SIV was introduced in a previous work and is now improved by establishing a high-speed setup to observe the temporal change of spray velocities during the injection. Within this work, velocities of potential future diesel fuels were measured under engine relevant conditions with a variation of fuel pressure, fuel temperature and gas pressure based on the ECN Spray A conditions. Velocity fields of Oxymethlyenether (OME) as an E-Fuel and Hydrogenated Vegetable Oil (HVO) as a Bio-Fuel were measured and compared with Gas-to-Liquid-Diesel (GTL) as a reference fuel. For constant fuel pressures, velocities for OME are about 15 % lower than for GTL and HVO, which is due to its higher density. Also, for OME velocities downwards the spray do not decrease as strongly as for GTL and HVO. It is assumed that OME has a weaker air-fuel-interaction, which is explained by a lower Weber-Number due to a higher viscosity.