LDV MEASUREMENTS OF TURBULENT-FLOW BEHAVIOR OF DROPLETS IN A 2-PHASE COAXIAL JET

Coaxial nozzles are frequently utilized for the atomization of liquids in sprays. The performance of a nozzle is generally evaluated by its atomizing characteristics, which are actually governed by the turbulen ce interactions of two fluids. With this point of view, this experimen tal study was carried out to investigate the turbulent behavior of the droplets atomized in a two-phase coaxial jet. Air acid water have bee n used as the working fluids, and the measurements have been made by a n on-line data acquisition system connected to a two-channel LDV set(D ISA, 5W, Argon laser, blue:488 nm, green:514.5 nm). In order to genera te a two-phase mixing jet, two types of coaxial nozzles(liquid column type, liquid sheet type) were used. For the investigations of the turb ulent flow structure of this two-phase mixing jet, the spreading rates , mean and fluctuating components, intermittency factors and the iso-c ontours of joint probability densities were measured and analyzed. The results from the both types of nozzles did not show remarkable differ ences in mean and fluctuating velocity distributions, intermittency fa ctors or the iso-joint probability density contours. Since the measure ments were made in the fully developed turbulent mixing regions, the m ean velocity distribution profiles showed good similarities and agreed well with the semi-empirical curves. The RMS values were represented as high order levels and so were the intermittency factors. The typica l development trends of turbulent components of mu' and upsilon' for b oth types were illustrated in the iso-joint probability density contou rs.