Mean structure and droplet behavior in a coaxial airblast atomized spray: Selfsimilarity and velocity decay functions

The far-field turbulent structure of an airblast coaxial spray without swir l has been studied using a two-velocity-component phase Doppler anemometer. Size, velocity, and droplet number density have been measured at nine diff erent locations from the injection plane. The measurements have been checke d against an extinction sensor. Deceleration has been studied and compared with other experiments in coaxial sprays, gaseous, and particle-laden jets. An expression, valid to describe the deceleration in coaxial sprays with a similar breakup mechanism, is proposed. Furthermore, five representative d roplet families discriminated by their Stokes number have been selected to study differences in their dynamic evolution in the spray. Self-similar vel ocity profiles in the mean and turbulent components have been obtained. In the axial component ah droplets are seen to behave similarly, while signifi cant differences are observed in the transverse velocity. Mean particle num ber density profiles are top-hat-shaped while the highest number density of droplets with Stokes number near unity is placed at off-axis locations. Th e distribution of the volume flux has also been calculated.