Quantitative measurement of planar droplet Sauter Mean Diameter in sprays using Planar Droplet Sizing

The purpose of this investigation is to assess and improve the accuracy of Sauter Mean Diameter measurements in dense sprays using a Planar Droplet Sizing (PDS) technique, based on the intensity ratio of scattered and fluorescence light. A novel data processing method of the PDS technique is suggested, which was derived from a theoretical light scattering investigation, and reduced possible sizing errors larger than 30% to below 10%. The novel approach for droplet sizing was applied to measure in a spray generated by a pressure swirl atomiser in a liquid-fuelled burner operated with water at isothermal conditions, in order to avoid the effect of liquid evaporation on the accuracy of PDS technique. The Sauter Mean diameter results from the PDS technique were compared to Phase Doppler Anemometer (PDA) sizing measurements. Good agreement was obtained between the two techniques in dense regions of the spray. Discrepancies remained in dilute spray regions due to systematic statistical uncertainties of the PDS technique and the dynamic range of the intensity of the CCD cameras, which did not allow detection of large single droplets in the dilute spray region.