IMAGING OF IMPINGING JET BREAKUP AND ATOMIZATION PROCESSES USING COPPER-VAPOR-LASER-SHEET-ILLUMINATED PHOTOGRAPHY

Abstract

Observation of a like-on-like injector element in the near-injector region has been accomplished with laser-sheet- illuminated photography to investigate spray characteristics as a function of jet velocity and injector geometry. Short duration exposures from single laser pulses produced instantaneous pictures of the injection and subsequent breakup processes, while multiple-exposure photographs revealed a time-averaged representation of the spray. In addition to the four previously documented spray regimes, the data suggested inclusion of a higher Reynolds number regime in which the pre-impingement jets are fully turbulent and undergoing surface breakup. The equation of a conic section was used to map multiple-exposure photographs revealing the overall spray shape. Further examination of the higher Reynolds number regime using transparent injector pieces revealed the presence of a cavitating region within the orifice. Discharge coefficients were calculated and found to be relatively constant for each injector tested, regardless of the presence of cavitation. The orientation of the injector orifice created a stable cavitating region in which the phenomenon of hydraulic flip was not observed, but the enhanced turbulence level led to an onset of jet atomization prior to impingement.