SUMMARY

A new diagnostic for the quantification of Sauter Mean Diameter (SMD) in high-pressure fuel sprays has been recently developed using combined optical and x-ray measurements at the Georgia Institute of Technology and Argonne National Laboratory, respectively. This diagnostic utilizes liquid scattering extinction measurements from diffuse back-illumination (DBI) imaging, conducted at Georgia Tech, and liquid absorption measurements from x-ray radiography, conducted at Argonne. The new diagnostic, entitled the Scattering Absorption Measurement Ratio (SAMR), quantifies two-dimensional distributions of path-integrated SMD, enabling construction of the spatial history of drop size development within practical fuel sprays. This technique offers unique benefits over conventional drop-sizing methods in that it can be more robust in optically dense regions of the spray, while also providing high spatial resolution of the corresponding droplet field. The spatially-resolved SMD measurements from this diagnostic will be valuable to the engine modeling community for the quantitative validation of spray submodels.
The methodology for quantification of SMD distributions using the SAMR technique has been previously introduced. This thesis extends the initial development of the SAMR technique by presenting in detail: experimental methodologies used in the SAMR technique, including the development of an ideal DBI setup for this technique; data processing methodologies; 2-D SMD measurements within diesel sprays for various experimental conditions; a summary of the sources of measurement uncertainty; and an assessment for how the sources of uncertainty affect the quantified SMD. The SMD results show that for low ambient density conditions droplets decrease in size as radial and axial position increases. For high ambient density conditions, however, the droplets show a stable size near the spray center line and steadily increase in size as distance from the center line increases.