Air Boundary Conditions Research Articles

Experimental study on the influence of liquid and air boundary conditions on a planar air-blasted liquid sheet, Part II: prefilming zone length

In this work, experiments were performed on a prefilming atomizer. For this purpose, an injector used for liquid sheet pulverization was adapted to highlight the influence of the prefilming zone. Breakup length, oscillation frequency and drop size were studied for various prefilming zone lengths and airflow configurations (convergent or divergent and different air thicknesses). Various influences were observed depending on the air configuration, with an improvement of the atomization process for convergent configuration when an optimum prefilming zone length is chosen. At the same time, visualizations of liquid dynamics and liquid thickness measurements on the prefilming zone have enabled the classification of liquid evolution in three regimes: “smooth”, “waves” and “accumulation”. The use of primary atomization parameters enables a cartography gathering all of the experimental conditions studied during this work to be proposed. Finally, a comparison of these results with previous correlations highlights the necessity to take into account the geometrical aspect of injection systems to predict the atomization characteristics.

Experimental study on the influence of liquid and air boundary conditions on a planar air-blasted liquid sheet, Part I: Liquid and air thicknesses

This experimental study is devoted to the influence of the air and liquid thicknesses on an air-blasted atomizer. The flow configuration corresponds to a planar liquid sheet sheared on both sides by two high velocity airflows. Using planar laser induced fluorescence, back lighting visualizations and light diffraction, flapping frequency, breakup length of the liquid sheet and droplet sizes resulting from the atomization process are measured. The results show that the influence of each fluid thickness depends on the investigated flow characteristic. Thus, breakup length is strongly correlated to liquid flow rate, whereas flapping frequency depends mainly on airflow conditions, characterized by the vorticity thickness. Concerning final droplet sizes, both previous parameters must be taken into account, leading to a correlation based on breakup length and oscillation frequency.