A contribution to the understanding of cavitation effects in Diesel injector nozzles through a combined experimental and computational investigation

In this paper a combined experimental and computational study was carried out in order to assess the ability of a homogeneous equilibrium model in predicting the experimental behaviour observed from the hydraulical characterization of a nozzle. The nozzle used was a six-orifice microsac nozzle, with cylindrical holes, and therefore inclined to cavitate. The experimental results available for the validation purpose comprised measurements of mass flow rate and spray momentum flux, which correctly combined provide also fundamental information such as discharge coefficient, nozzle exit effective velocity and area contraction. The model was proved to be able of reproducing the experimental results with high degree of confidence and, through the exploration of the internal flow, allowed the explanation of widely reported experimental findings related to cavitation phenomena: the mass flow choking induced by cavitation and the increment of effective injection velocity.

► A code for modelling cavitation has been validated against experimental data.
► The validation covers mass flow, momentum flux, velocity and flow coefficients.
► Cavitation shows a cyclic behaviour (formation and growth, collapse and break-off).
► The reason of the mass flow choking is a constant pressure at the throat.
► The rise of the effective velocity is a consequence of the decrease of viscosity.