Experimental study of sprays from annular liquid jet breakup

An experimental investigation has been conducted to study the characteristi cs of sprays produced from the breakup of annular water jets exposed to inn er airstreams, simulating twin-fluid atomization, by using phase Doppler an emometry, The spray characteristic parameters, such as droplet Sauter mean diameter (SMD), mean velocity, velocity fluctuation, and droplet number den sity have been measured for various radial and axial locations and under va rious liquid and airflow velocities at the nozzle exit. The results indicat e that the spray characteristic parameters are almost symmetric about the s pray arris. At each axial spray cross section, the droplet mean axial veloc ity reaches the maximum value in the spray center and decreases from the sp ray center to the edge. Further, the droplet axial velocity has a jet-like selfsimilar spatial distribution along the radial and axial directions when normalized by appropriate reference parameters. Similar universal correlat ion is observed for the droplet fluctuation velocity and turbulent intensit y as well. The SMD has a minimum value at the spray center and increases to ward the spray periphery. The SMD at the spray centerline has a more comple x variation in the downstream direction because of secondary atomization at high air velocity near the nozzle exit and droplet entrainment and migrati on farther downstream. The droplet number density has a radial distribution similar to that of the SMD, whereas its value at the spray center increase s with the distance from the nozzle exit, and is reduced by the high air an d liquid flow velocity.