A review of the literature on the atomization of high viscosity fluids is provided. The review starts with a brief presentation of various atomization models, which are used to predict the spray droplet sizes. Next, atomization results using different types of atomizers are reviewed. These include plain orifice, splash plate, swirl, and twin-fluid atomizers.
Generally, most studies show that the Sauter Mean Diameter of a spray (SMD) increases with viscosity. This increase can be compensated by increasing the energy input to the atomizer (such as increasing the atomizing gas pressure or velocity). However, even in the cases that SMD does not change significantly, the size distribution changes with viscosity. In sprays of high viscosity liquids, larger droplets take up a larger proportion of the spray size distribution, resulting in the deterioration of the spray quality. The primary atomization of high viscosity liquids generates longer liquid ligaments and filaments, which have to be atomized during a secondary atomization process. This later process is intimately related to the coflowing gases. The secondary atomization of the long ligaments can be expedited by having high velocity coflowing atomizing gas. The review ends with a case study for the prediction of the droplet size distribution using a detailed numerical modeling that considers the exact design of the atomizer.