| Two shadow sizing codes have been compared using (A) an ideal test target with step-shaped boundary gradients, (B) recorded images of this test target, (C) images taken from a prefilming airblast atomizer and (D) a dense spray dispersed in a carrier gas. The two codes under consideration are an in-house code from the Institut für Thermische Strömungsmaschinen (ITS) and DaVis-SizingMaster Shadow from LaVision. The results of both codes are compared with respect to the number of detected particles, the count mean diameter D(1,0) and the Sauter mean diameter D(3,2). From the target tests it was found that the lower resolution limit of the Institut für Thermische Strömungsmaschinen code enables the detection of particles represented down to one pixel, whereas for the DaVis-code – in line with the technical specification fromLaVision – the lower resolution limit corresponds to particles having a diameter of 3 pixels. The results obtained for the case of the airblast atomizer demonstrate a similar detectability, i.e. the number of detected particles in one picture is the same for both codes for low, medium and dense sprays cases. Furthermore, the calculated droplet size distributions are in good agreement with each other, indicating size independent detectability. For the measurements of droplet size distributions in the spray, the count based as well as the cumulative volume size distributions based on the Institut für Thermische Strömungsmaschinen and the DaVis code agreed very well. |
