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The hollow cone spray from a high pressure outward opening nozzle was investigated inside a pressure vessel by means of particle image velocimetry (PIV). The flow velocities of the air outside the spray were measured via PIV in combination with fluorescent seeding particles and optical filters. The high pressure piezo electric injector has an annular nozzle to provide a hollow cone spray with an angle of about 90°. During injection a very strong and stable vortex structure is induced by the fuel spray. Besides the general spray/air interaction, the investigation of double and triple fuel injections was the main focus of this study.

The objective of this research work was to assess the potential of an electrostatic fluid atomization method for application in direct injection systems for combustion engines. The most important finding of this study was that it is possible to detect the influence of electrostatic atomization at injection pressures up to 300 bar using diesel fuel. The electrostatic force affects the liquid core of the fuel spray from typical diesel nozzles in such a way that additional surface waves are produced which in turn cause the spray to breakup earlier, i.e. the spray breakup length is reduced significantly. This early breakup leads to smaller mean droplet diameters, larger spray angles and as a result air entrainment of the fuel spray is enhanced. Theoretical models were derived to explain the effects of electrostatic charge on fluid atomization.