Effect of Nozzle Geometry on Macroscopic Behavior of Diesel Spray in the Near-Nozzle Field

In this study, the orifice inlet rounding radii of four diesel nozzles with different hydro erosive grinding time were measured based on the x-ray CT scan technology provided by Shanghai Synchrotron Radiation Facility (SSRF), and a wide parametrical study of the spray macroscopic behavior in the first 18 mm from the nozzle tip have been carried out with high speed camera. And then the influence of orifice inlet rounding radius on the spray behavior in the near-nozzle field was thoroughly investigated.

The investigation results show that: the mean values of orifice inlet rounding radii of different nozzles are measured to be on the order of 21.5-56.8 μm. Although the spray tip penetrations of different nozzles tend to increase with the hydro erosive grinding time through statistical analyzing method, the variations of penetration from nozzles are less than 15% according to different hydro erosive grinding timing. For the spray cone angle in the near-nozzle field, the same maximum for nozzles of different hydro erosive grinding time can be achieved at the unsteady state, but hydro erosive grinding can shorten the unsteady duration of spray cone angle. During the steady state of spray, the difference in spray behavior from nozzles is distinctive and should adopt the standard deviation of orifice inlet rounding radii to characterize instead of the mean value. A new correlation is proposed which accounts for the influence of the orifice inlet rounding radius on the spray cone angle at the steady state.