Analysis of Diesel Spray Structure Using Magnified Photography and PIV

The effects of fuel injection velocity and ambient gas pressure on the spray formation and atomization process for a non-evaporating diesel spray were observed and analyzed with greatly magnified photographs illuminated by a pulsed ruby laser light sheet. Individual fuel droplets were distinguishable at the peripheral regions of the spray in these photographs. The spray width became narrower with an increase in injection velocity, and the spray spread out further with increase in ambient gas pressure. The branch-like structure in the spray originated from local high and low fuel particle number density regions and the difference in number density between these two regions increased with higher injection velocity. The ruby laser was double-pulsed to enable fuel particle velocity vectors to be characterized at the peripheral regions of the fuel spray. The vorticity scale was smaller and vorticity magnitude grew higher with increase of injection velocity.