Nozzle design effects of dense spray region characteristics

摘要

Past investigations have revealed that nozzle design and fabrication influence significantly the structure and dynamics of fuel sprays, viz., spatial distribution of droplet size, number density, and velocity, as well as size and velocity distributions. Fuel spray nozzles used in many practical applications are of the pressure-jet or air-assist type. Studies carried out with these nozzles have generally provided spatially resolved information in non-dense regions of the spray, i.e., at axial positions downstream of approximately 20 mm. Measurements closer to the nozzle, where number concentrations exceed 10(sup 6) particles/cc, are more difficult because of problems associated with applying available particle sizing techniques (i.e., single particle counters and laser diffraction devices) to this region. The results presented are from an ongoing investigation to characterize pressure-atomized and air-assisted sprays. Spatial profiles of droplet mean size, number density and velocity have been reported in the past, with recent attention given to the droplet velocity distributions. The study has focused on the dense region of the spray immediately downstream of the nozzle exit. This region is of particular interest since it provides information on the initial structure and dynamics of the spray, without being perturbed by the surrounding aerodynamic pattern. This information can be used used to furnish data for spray modeling efforts.