CFD – Gas-Assisted Atomization

Posted on April 14, 2022

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Modeling gas-assisted atomization as phase inversion

Effervescent atomization is a type of a gas-assisted atomization where gas is dispersed into liquid at high pressure. Once pressure decreases, gas bubbles grow and coalesce creating liquid droplets. Thus, the continuous phase changes from liquid to gas in a phenomenon called phase inversion. The effervescent atomization is a fast and efficient way to create droplets.

This can be implemented into a computational fluid dynamics (CFD) model to simulate atomization with an assumption that the phase inversion takes place instantaneously across the surface of a certain gas volume fraction. To determine the diameter of the newly formed droplets, the number of particles is assumed to be constant.

The figure illustrates atomization modeling by presenting bubble/droplet size variation (in mm) in a steam-assisted bitumen atomization. As pressurized mixture of steam and bitumen goes through the convergent-divergent nozzle, the bubble diameter changes due to break up and coalescence. After the phase inversion at 80% steam fraction, the droplet diameter falls and then continues to decrease due to secondary break-up by turbulence.

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