Atomization of PEO aqueous solutions in effervescent atomizers

The paper contains the results of experimental investigation of air–water and air–polymer solutions atomization process in effervescent nozzles with internal mixing obtained by the use of the digital microphotography method. In experiments the different aqueous solutions of polyethylene oxide (PEO) of different molecular weight have been used. The observations were carried out at liquid flow rates changed from 0.0014 to 0.011 kg/s and gas flow rates from 0.0003 to 0.0013 kg/s. It corresponded to gas to liquid mass ratios values from 0.028 to 0.92. The analysis of photos shows that the droplets which have been formed during the liquid atomization have very different sizes. The smallest droplets have diameters of the order of dozens of micrometers. The differences between characteristics of effervescent atomization for the different types of PEO used have been observed. The structures for the polymer solutions were analyzed. The development of the spray passes through several stages such as dribble, distorted pencil and fully developed spray. Additionally, the following stages were distinguished: the filaments with built-in droplets, the filaments with built-in bubbles, satellite bubbles and bubbles connected by filaments. The present study confirmed the previous reports which suggested that the changes in character of a flow are connected with the rheological properties of liquid, two-phase flow character, flow rates of liquid and gas phases. The high molecular weight of polymer effected on spray form. Often, the observations of atomization of these solutions show that they do not form a spray. The effects observed lead to significant changes in the quality of the spray produced by nozzle. The experiments have shown that the construction of aerator had a little effect on Sauter diameter values. The correlation equation for Sauter diameter has been proposed.