Miguel Ángel Ballesteros Martínez, Prithika Roy, Juan Nicolás Solano Alarcón, Volker Gaukel
{"title":"Atomizing high-viscosity non-Newtonian fluids with the ACLR nozzle: Correlation between internal flow and external spray instabilities","authors":"Miguel Ángel Ballesteros Martínez, Prithika Roy, Juan Nicolás Solano Alarcón, Volker Gaukel","doi":"10.1016/j.jnnfm.2025.105405","DOIUrl":null,"url":null,"abstract":"<div><div>Spray drying is a widely used method for producing food powders in large quantities, but it also has a high energy demand. To address this, one can increase the solid content of liquid feeds, although this, in turn, poses the challenge of atomizing high-viscosity liquids into fine droplets. The Air-Core-Liquid-Ring (ACLR) nozzle offers a potential solution for the atomization by inducing air and creating an annular flow inside the nozzle. Nevertheless, a challenge of this design is that it tends to present internal instabilities. This study investigates how feed viscosities up to 3 Pa·s, and feed dry-matter contents up to 57 % wt., influence the internal flow conditions and the resulting spray performance, i.e., the droplet size distribution and the spray angle. The results show that, while internal instabilities increment with increasing viscosities, the ACLR can seemingly achieve atomization with viscosities as high as 3 Pa·s, even at, compared to pressure swirl nozzles, low pressures (7 bar) and low air-to-liquid mass ratios (0.8). Nonetheless, a fraction of droplets over 500 µm remains, which needs to be addressed through higher ALRs or a geometrical optimization of the nozzle, before the nozzle can be considered for industrial applications. Additionally, we showed that the internal flow and the external spray instabilities can be correlated with each other. This confirms that any future studies attempting to increase the spray stability of the ACLR nozzle can focus on only one of these factors, and reasonably expect that the others will also improve.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"338 ","pages":"Article 105405"},"PeriodicalIF":2.7000,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Non-Newtonian Fluid Mechanics","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0377025725000242","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MECHANICS","Score":null,"Total":0}
引用次数: 0
Abstract
Spray drying is a widely used method for producing food powders in large quantities, but it also has a high energy demand. To address this, one can increase the solid content of liquid feeds, although this, in turn, poses the challenge of atomizing high-viscosity liquids into fine droplets. The Air-Core-Liquid-Ring (ACLR) nozzle offers a potential solution for the atomization by inducing air and creating an annular flow inside the nozzle. Nevertheless, a challenge of this design is that it tends to present internal instabilities. This study investigates how feed viscosities up to 3 Pa·s, and feed dry-matter contents up to 57 % wt., influence the internal flow conditions and the resulting spray performance, i.e., the droplet size distribution and the spray angle. The results show that, while internal instabilities increment with increasing viscosities, the ACLR can seemingly achieve atomization with viscosities as high as 3 Pa·s, even at, compared to pressure swirl nozzles, low pressures (7 bar) and low air-to-liquid mass ratios (0.8). Nonetheless, a fraction of droplets over 500 µm remains, which needs to be addressed through higher ALRs or a geometrical optimization of the nozzle, before the nozzle can be considered for industrial applications. Additionally, we showed that the internal flow and the external spray instabilities can be correlated with each other. This confirms that any future studies attempting to increase the spray stability of the ACLR nozzle can focus on only one of these factors, and reasonably expect that the others will also improve.
期刊介绍:
The Journal of Non-Newtonian Fluid Mechanics publishes research on flowing soft matter systems. Submissions in all areas of flowing complex fluids are welcomed, including polymer melts and solutions, suspensions, colloids, surfactant solutions, biological fluids, gels, liquid crystals and granular materials. Flow problems relevant to microfluidics, lab-on-a-chip, nanofluidics, biological flows, geophysical flows, industrial processes and other applications are of interest.
Subjects considered suitable for the journal include the following (not necessarily in order of importance):
Theoretical, computational and experimental studies of naturally or technologically relevant flow problems where the non-Newtonian nature of the fluid is important in determining the character of the flow. We seek in particular studies that lend mechanistic insight into flow behavior in complex fluids or highlight flow phenomena unique to complex fluids. Examples include
Instabilities, unsteady and turbulent or chaotic flow characteristics in non-Newtonian fluids,
Multiphase flows involving complex fluids,
Problems involving transport phenomena such as heat and mass transfer and mixing, to the extent that the non-Newtonian flow behavior is central to the transport phenomena,
Novel flow situations that suggest the need for further theoretical study,
Practical situations of flow that are in need of systematic theoretical and experimental research. Such issues and developments commonly arise, for example, in the polymer processing, petroleum, pharmaceutical, biomedical and consumer product industries.