Effect of asymmetrical orifice inlet geometry on spray kinematics and development

Artikel i vetenskaplig tidskrift, 2023

In diesel engines, fuel injection has a commanding effect on combustion. Thus studying diesel spray characteristics is beneficial for controlling and improving diesel combustion. However, information on diesel spray characteristics, especially those governed by injector needle lift, is lacking. This study investigates the near-nozzle spray kinematics for particular nozzle geometries over a range of injection pressures. The nozzles used in this research include a single-hole off-axis nozzle and a two-hole nozzle with deviated orifices. This study aims to observe the effect of asymmetrical orifice inlet on the spray kinematics and describe how sensitive they are to the injection pressure. First, we applied double-pulses time-gated ballistic imaging to obtain well-defined spray/gas interfaces. Then, by tracking these interface structures, we obtained spray kinematics. The results show that the two-hole nozzle generates slower sprays than the single-hole nozzle at the beginning of injection. However, the velocity differences between these sprays become less significant as the sprays develop to a quasi-steady state. In addition, the velocity diagrams show that the instabilities cause the flow to experience significant velocity alterations at the beginning of the injection. Moreover, we observed that the nominal spray axis shifts towards the sharper orifice inlet edge, which will affect the spray targeting. Finally, the injection pressure seems to have minimal effect on the spray profile, but it certainly changes spray evolution timing and shortens the transient phase.