In this paper the behavior of the internal flow under cavitating conditions and the influence of using different fuels is studied. For this purpose, a transparent nozzle (quartz plate) with a cylindrical orifice and four different fuels are used. The nozzle is installed in a pressurized rig with fuel in order to measure the mass flow and observe the flow inside the orifice using a special visualization technique with all fuels. Since the refractive index of the vapor bubbles of the fuel is different to de refractive index of the fuel in liquid state, the cavitation inside the nozzle can be appreciated. Pressure conditions at which the first bubbles inside the orifice appear are compared with the pressure conditions for mass flow collapse, showing that the beginning of the cavitation occurs before the mass flow collapse and that it depends both on the upstream and downstream pressure conditions and on the fluid viscosity used. Additionally it is observed that the mass flow collapse takes place once the cavitation is fully developed through the whole orifice and the presence of bubbles in the spray before the mass flow collapse indicating that the cavitation appears before the mentioned collapse. HIGHLIGHTS> Visualization of cavitation phenomenon in transparent diesel injection nozzles. > Influence of using different fuels in cavitation phenomenon. > Fuels with less viscosity tend to cavitate sooner. > Incipient cavitation occurs before the mass flow collapse. > The first bubbles in the spray appear before the mass flow collapse occurs.

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