An experimental study of droplet dynamics in a turbulent droplet-laden round jet

Abstract

In this investigation, particle dispersion and axial velocity of single droplets (60 and 85 urn diameter) were measured in a turbulent droplet laden round jet of Reynolds number 12,000 and mass loadings varying from 0 to 30 percent. The measured droplets were tagged with Rhodamine 590 and injected along the centerline of the spray. Using multiple laser sheets of 514 nm wavelength, optical filters and a position sensitive photomultiplier tube, the droplet dispersion and axial velocity of the fluorescent droplets were measured at downstream axial locations. A special nozzle was built with micro air-blast atomizers embedded in the wall in order to deposit the spray into the air flow and not have them collide with the walls. From these measurements it could be seen that an increase in mass loading has a significant effect on the dispersion of droplets, especially for mass loadings above 15 percent and for axial distances greater than 20 x/d. In order to characterize the spray, the centerline Sauter mean diameter and distribution were measured via high magnification digital imaging. In addition, Mie scattering images of the spray were taken and planar laser induced fluorescence measurements of acetone doped air were made with and without the spray in order to see if the development of the gas phase was altered significantly with the addition of the droplets. The Mie images showed that the jet structure was retained and from the PLIF measurements, no gross changes in gas phase structure were observed.