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Effect of Different Diesel Fuel Nozzle Holes Geometries on Cavitation

Abstract:

Cavitation is the major cause of the effective flow area reduction in fuel nozzles, together with mechanical damage, which leads to an increase of pressure losses. This paper describes the effect of different geometries along the fuel nozzle holes simulated with OpenFOAM® to control the cavitation and shape of the fuel jet. Previous work has only focused on the development trend towards conical spray holes that tapers towards the outlet with a strong rounded inlet edge, to increase the static pressure and thus reduce the cavitation tendency in nozzles; however, the jet forms a very narrow cone angle. The aim of this study is to evaluate the effect of constricted, expanded and gradually wider nozzles holes. The simulation reveals that the cavitation level can be changed and controlled depending on the geometry of the nozzle holes, the wider the inlet, the less is the cavitation; at the same time, the narrower the outlet, the better is the fuel atomization. Critically, a wider inlet compared to the outlet of the nozzle hole is the key factor that leads to a reduced cavitation and therefore to a reduced to flow resistance. Our study reveals that the volume ratio of vapor is reduced with the straight nozzle holes from 0.92 up to 0.51, with the nozzle tapered towards the middle of the nozzle holes length. As the cavitation also enhances the turbulence it is possible to control its intensity and place in the nozzle hole by modifying its geometry to enhance the atomization of the fuel.