ANALYSIS OF PRIMARY BREAKUP IMAGES FROM AN ENGINE-RELATED SHEET ATOMIZER

In this study sheet atomization from an engine-related outwardly opening hollow-cone injector with known geometry is examined by means of high -resolution shadowgraphy of the near-nozzle region. The investigated Reynolds and Ohnesorge numbers range from 300 to 21,000 and from 0.01 to 0.26, respectively, whereas the ambience was kept constant at atmospheric conditions. First the experimental setup and the measurement procedure are introduced, followed by a discussion of the applicability of ballistic imaging. The images indicate that classical shadowgraphy is the favorable technique for the present sprays and the pursued optical resolution. The acquired images are analyzed qualitatively and sheet breakup is classified in a Reynolds-Ohnesorge diagram marking the transition region from an intact to a fully atomized sheet. Finally the Fourier transforms of the images are investigated in order to derive quantified data for fully atomized sheets. Especially the frequency bandwiths contained in the images correlate well with the driving flow properties Reynolds and Ohnesorge number.