Elucidation and Modeling of the Atomization Process of a Liquid Film Flow Induced by Co-current Gas Flows*

Air-blast atomizers have been widely used in aircraft engines due to their superior atomization performance. Prediction of fuel spray characteristics is vital for designing and optimizing the atomizer. In previous studies, a number of models on mean droplet diameter have been proposed, which do not based on the atomization process and require tuning parameters using measurement results.

In this work, we elucidate the complicated atomization process of the liquid film with co-current air flows by high-speed imaging, and develop a mechanistic model to quantitatively predict droplet diameter distribution based on the bag formation and rupture phenomenon, which does not require any tuning parameters. As a result, we obtain the following conclusions. The rupture of the bag film is caused not by the airflow turbulence but by the collision of the floating droplets on the expanding bag film. At the edge of the perforation, tiny droplets are formed. After the bag ruptures, the liquid film contracts toward the vertical and transverse rims, and becomes the large ligaments and then large droplets. The validity of the model is verified through the comparison with our experimental results on the diameter distributions of the tiny and large droplets.