Atomization of shear-thinning liquids using pressure swirl atomizers

článek ve sborníku mimo WoS a Scopus

en

Atomization of non-Newtonian liquids is a rarely studied topic though these are used in a number of spray applications. The main factors of the spray influencing various applications are mean droplet size and size range. Based on several works, non-Newtonian liquids, characterized by shear-thinning properties, are expected to affect the drop size distribution and preferably to narrow it compared to Newtonian liquids. Such feature can be applied in different areas for example to reduce amount of too small or large droplets. Several non-Newtonian dispersions were prepared by mixing Xanthan Gum and Sodium carboxymethyl cellulose with deionized water. Their performance was compared with Newtonian liquids (water and water-glycerol solution) of the same shear viscosity at defined share rate. A common pressure swirl atomizer was applied for this study in a range of operational pressures which, together with varying viscosity of individual liquids allowed to observe the spraying process at a wide range of Reynolds and Weber numbers. Simultaneous measurement of velocity and droplet sizes in the developed spray was performed with a 1D phase Doppler anemometer. The spray morphology and breakup process was tracked using high-speed visualization. These results were complemented with calculations of the flow parameters inside the atomizer. The results show that the varying viscosity and the shear-thinning behaviour modify the flow since liquid entry into the atomizer until the developed spray. The discharge character depends namely on the flow conditions near the exit orifice. The shear thinning behavouur of the liquid slightly affect the atomization process with production of more frequent and longer lasting ligaments. Sauter mean diameter of non-Newtonian liquids reduces faster with pressure while the effect on Relative span factor is unsystematic.

Atomization of non-Newtonian liquids is a rarely studied topic though these are used in a number of spray applications. The main factors of the spray influencing various applications are mean droplet size and size range. Based on several works, non-Newtonian liquids, characterized by shear-thinning properties, are expected to affect the drop size distribution and preferably to narrow it compared to Newtonian liquids. Such feature can be applied in different areas for example to reduce amount of too small or large droplets. Several non-Newtonian dispersions were prepared by mixing Xanthan Gum and Sodium carboxymethyl cellulose with deionized water. Their performance was compared with Newtonian liquids (water and water-glycerol solution) of the same shear viscosity at defined share rate. A common pressure swirl atomizer was applied for this study in a range of operational pressures which, together with varying viscosity of individual liquids allowed to observe the spraying process at a wide range of Reynolds and Weber numbers. Simultaneous measurement of velocity and droplet sizes in the developed spray was performed with a 1D phase Doppler anemometer. The spray morphology and breakup process was tracked using high-speed visualization. These results were complemented with calculations of the flow parameters inside the atomizer. The results show that the varying viscosity and the shear-thinning behaviour modify the flow since liquid entry into the atomizer until the developed spray. The discharge character depends namely on the flow conditions near the exit orifice. The shear thinning behavouur of the liquid slightly affect the atomization process with production of more frequent and longer lasting ligaments. Sauter mean diameter of non-Newtonian liquids reduces faster with pressure while the effect on Relative span factor is unsystematic.

shear-thinning liquids, Non-Newtonian liquids, Relative Span Factor, Shear viscosity, extensional viscosity, pressure swirl atomizer

23.06.2024

ICLASS 2024

Shanghai

1–12

12