Search Results

An experimental study of real multi-hole diesel nozzles with different geometry in terms of conicity factor has been performed under current DI Diesel engines operating conditions. A complete characterization of the internal nozzle flow and the sprays injected under non-evaporative conditions has been performed. The results of that study are applied in order to assist the analysis of spray in evaporative conditions. In this case, results of liquid-phase fuel penetration were obtained from a wide optical access engine operating under non-reacting conditions. From these measurements, a comparison of the results with a theoretical Diesel spray model in evaporative conditions has been carried out. This comparison has allowed the determination of the dependence of stabilized liquid length on injection pressure, ambient conditions and nozzle geometry.

The onset and development of the inner cavitating flow in Diesel injectors is analyzed in relation with the needle movement, using Computational Fluid Dynamics studies realized with moving mesh. Two real six-hole injector geometries have been considered, one with cylindrical nozzles, the other with conical nozzles. A full analysis of the flow results is presented, including a dynamic picture of the developing pattern. Results show that depending on the needle lift, the cavitation pattern varies strongly throughout the nozzle, and affects the characteristics of the flow at the nozzle exit. A kind of hysteresis in the development of the flow has also been observed between needle opening and closing.

In order to study differences between Diesel nozzle holes, four methodologies have been tested. The techniques compared in this paper are: the internal geometry determination, hole to hole mass flow measurement, spray momentum flux and macroscopic spray visualization. The first one is capable of obtaining the internal geometry of each of the orifice of the nozzle; the second one is capable of measuring the mass flow of each nozzle hole in both, continuous and real injections. The third one gives the momentum flux of each orifice, and finally, with the macroscopic spray visualization, the spray penetration and spray cone angle of each hole, are obtained. Generally, all these techniques can be used in order to determine the hole to hole dispersion due to different angle inclination of the holes, different internal geometry of orifices, deposits, nozzle needle off-center, needle deflection, etc.