WATER SPRAY CHARACTERIZATION OF A COAXIAL AIR-ASSISTED SWIRLING ATOMIZER AT SONIC CONDITIONS

The present work was performed to quantitatively investigate the spray characteristics from a swirling coaxial gas-assisted atomizer for moderate industrial flow rates of water, low to medium swirl generation of the assisting air, and high momentum flux ratios at sonic air flow rates at the convergent nozzle exit. In the considered cases, two different liquid to gas mass flow ratios for two different nozzle contraction ratios were studied, with and without the use of swirl. The spray characteristics were obtained by using phase Doppler anemometry and a three-coordinate traversing system, which could accurately position the measurement volume in the spray. For the conditions considered in this paper, it was found that the introduced swirl reduces the axial velocity in the center core of the spray up to 45%. Furthermore, the spreading rate of the resulting spray jet increased when the swirl increased, and the liquid to gas mass flow ratio and the momentum flux ratio were decreased. The largest droplets were found in the center of the spray, and the smallest droplets appeared around the middle radial position of measurement.