ID 87

Predicting cavitation occurrence in simplified fuel injector based on geometrical considerations

Marin Deflorin
Institute of Thermal and Fluid Engineering, University of Applied Sciences ‐ Northwestern Switzerland, CH‐5210 Windisch
Switzerland

Daniel A. Weiss
Institute of Thermal and Fluid Engineering, University of Applied Sciences ‐ Northwestern Switzerland, CH‐5210 Windisch
Switzerland

Abstract:

Flow inside injection nozzles in large two-stroke diesel engines can have an impact on the spray formation. The injectors are usually arranged around the cylinder wall and multiple orifices are fed asymmetrically by one central bore. Experiments have shown that this different geometric configuration of the orifice lead to asymmetric spray formation. This spray can lead to wall wetting and have negative effects on fuel consumption, emissions, component temperatures and the lubrication film on the cylinder wall. To investigate the cavitation development inside nozzle flow under different geometric parameters, a computational study was performed. The simulation model has been developed in ANSYS CFX 17.0 based on a VoF (Volume of Fluid) approach combined with a RANS turbulence model. The model was validated and compared with different literature data which showed comparable effects. Four different geometric parameters were varied and compared with the reference orifice. The cavitation in the orifice disappears with larger flanging radius and conical spray hole. With an offset of the orifice to the central bore of the injector or an angled orifice, the cavitation gets shifted to one side of the orifice but is not decreased in total. The shift of cavitation to one side leads to an asymmetric outlet velocity field. An analytic model was developed which can predict the formation of cavitation in this simplified nozzle for the different parameters.