ENHANCED ATOMIZATION OF VISCOUS LIQUIDS USING A COUNTERFLOW NOZZLE

This study examines the atomization of viscous liquids using a recently developed internal mixing nozzle design, the "counterflow" nozzle. The geometry seeks to establish a countercurrent two-phase mixing layer inside the nozzle, with the low density high-speed gas next to the wall. Three liquids with widely varying viscosity (water, propylene glycol, and an 85% aqueous solution of glycerol) are tested for a range of air-liquid mass flow ratios, and for a fixed liquid flow rate of 60 ml/min. A flow-blurring nozzle is used as a reference for comparison High speed imaging suggests that the liquid emerges from the counterflow nozzle orifice directly as a collection of droplets, with little evidence of ligament formation. Droplet diameter distributions are measured using a shadowgraphy technique, and are found to have a very weak dependence on the liquid viscosity. Pressure drop measurements are combined with Sauter mean diameter values to evaluate spray efficiency, and it is found that the counterflow nozzle displays enhanced efficiency, especially at the lower end of the range of air mass flow rates studied.