Change search
ReferencesLink to record
Permanent link

Direct link
Acoustic separation and electrostatic sampling of submicron particles suspended in air
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.ORCID iD: 0000-0002-4171-5091
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We investigate experimentally the effects of acoustic forces on submicron aerosol in a channel flow. This technique can potentially overcome some of the limitations of conventional separation systems and provide advanced manipulation capabilities such as sorting according to size or density. The theoretical framework for acoustophoresis at such small length scales where molecular effects are expected to be significant is still incomplete and in need of experimental validation. The main objectives of this thesis are to identify the physical limitations and capabilities of acoustophoretic manipulation for submicron aerosol particles.

Two sets of experiments were carried out: first, qualitative results revealed that acoustic manipulation is possible for submicron particles in air and that the acoustic force follows the trend expected by theoretical models developed for particles in inviscid fluids. The acoustic force on submicron particles was estimated in a second set of measurements performed with quantitative diagnostic tools. Comparison of these results with available theoretical models for the acoustic radiation forces demonstrates that for such small particles additional forces have to be considered. At submicron length scales, the magnitude of the forces observed is orders of magnitude higher than the predictions from the inviscid theory.

One potential application for acoustophoresis is specifically investigated in this thesis: assist electrostatic precipitation (ESP) samplers to target very small aerosols, such as those carrying airborne viruses. To identify the shortcomings of ESP samplers that acoustophoresis should overcome, two ESP designs have been investigated to quantify capture efficiency as a function of the particle size and of the air velocity in a wind tunnel. The results reveal that both designs have limitations when it comes to sampling submicron aerosol particles. When exposed to polydispersed suspensions they behave as low-pass filters.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 77 p.
Series
TRITA-MEK, ISSN 0348-467X
Keyword [en]
Acoustic, separation, acoustophoresis
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-196857ISBN: 978-91-7729-221-0OAI: oai:DiVA.org:kth-196857DiVA: diva2:1049359
Public defence
2016-12-16, D3, Lindstedsvägen 5, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20161125

Available from: 2016-11-25 Created: 2016-11-24 Last updated: 2016-11-25Bibliographically approved
List of papers
1. Turbulence and geometric effects on the efficiency of continuous acoustic particle separation in a gas
Open this publication in new window or tab >>Turbulence and geometric effects on the efficiency of continuous acoustic particle separation in a gas
2013 (English)In: Proceeding of International Conference on MultiphaseFlows, ICMF2013, 2013Conference paper (Refereed)
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-196907 (URN)
Conference
International Conference on Multiphase Flows, ICMF2013, May 2013, Jeju, Korea
Note

QCR 20161125

Available from: 2016-11-25 Created: 2016-11-25 Last updated: 2016-11-25Bibliographically approved
2. Acoustic separation of sub-micron particles in gases
Open this publication in new window or tab >>Acoustic separation of sub-micron particles in gases
2013 (English)In: Proceedings of Meetings on Acoustics: Volume 19, Issue 1, June 2013, Acoustical Society of America (ASA), 2013, 045020- p.Conference paper (Refereed)
Abstract [en]

In several areas of science and technology there is a strong need for concentrating, separating and sorting small particles suspended in gaseous flows. Acoustic fields can be used to accomplish this task, an approach extensively used in liquid phase microfluidics that has great potential for aerosol treatment. This paper presents an experimental investigation of acoustophoresis for very small particles in gases, with sizes ranging from tens to hundreds of nanometers. The phenomenon is studied in a rectangular channel with variable height in which a standing acoustic field is created by a broadband electrostatic transducer operated in the 50-100 kHz range. Downstream of the separation channel, the flow is separated into enriched and depleted streams with adjustable slits for analysis. The particle number density and size distribution is measured with a Scanning Mobility Particle Sizer (SMPS) as a function of position in the standing wave pattern. From these measurements, the separation efficiency is determined as a function of the particle size and the amplitude of the acoustic field. For the very small particles used here, this yields novel information on the magnitude of acoustophoretic forces in the transition and molecular flow regimes.

Place, publisher, year, edition, pages
Acoustical Society of America (ASA), 2013
Series
, Proceedings of Meetings on Acoustics, ISSN 1939-800X ; 19
Keyword
Electrostatic transducers, Experimental investigations, Particle number density, Scanning mobility particle sizer, Science and Technology, Separation efficiency, Standing wave patterns, Sub-micron particles
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-134176 (URN)10.1121/1.4800812 (DOI)2-s2.0-84878982914 (ScopusID)
Conference
21st International Congress on Acoustics, ICA 2013 - 165th Meeting of the Acoustical Society of America; Montreal, QC; Canada; 2 June 2013 through 7 June 2013
Note

QC 20131119

Available from: 2013-11-19 Created: 2013-11-18 Last updated: 2016-11-25Bibliographically approved
3. Acoustic Separation of Submicron Solid Particles in air
Open this publication in new window or tab >>Acoustic Separation of Submicron Solid Particles in air
2015 (English)In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 63Article in journal (Refereed) Published
Abstract [en]

The use of ultrasound to continuously separate submicron particles suspended in air is investigated in a rectangular channel with adjustable height. An electrostatic transducer is used to generate a standing wave in the 50-80 kHz frequency range and the particles experience forces within the acoustic field causing them to concentrate at the pressure nodes. To assess the effect of several key design parameters on the separation efficiency, a simple method based on light scattering is implemented to provide information on the particle concentrations as a function of position in the channel. The images acquired are processed to yield a separation efficiency metric that is used to evaluate the effect of acoustic, flow and geometrical parameters. The results show that, in qualitative agreement with theoretical models, the maximum separation efficiency increases with the pressure amplitude of the sound wave. The separation efficiency is also linearly proportional to the standing wave frequency, when it is varied between 50-80 kHz. On the other hand, the effect of the average fluid velocity is less pronounced than expected, suggesting that in our channel separation is not limited by the interaction length between the acoustic field and the suspended particles. The effect of the parallelism of the reflector relative to the transducer is also investigated.

National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:kth:diva-167638 (URN)10.1016/j.ultras.2015.06.021 (DOI)000359603000017 ()2-s2.0-84945200466 (ScopusID)
Note

Updated from manuscript to article.

QC 20150909

Available from: 2015-05-22 Created: 2015-05-22 Last updated: 2016-11-24Bibliographically approved
4. Quantitative Measurement of Acoustic Forces on Submicron Aerosol Particles in a Standing Wave Field
Open this publication in new window or tab >>Quantitative Measurement of Acoustic Forces on Submicron Aerosol Particles in a Standing Wave Field
(English)Manuscript (preprint) (Other academic)
Keyword
aerosol, separation, acoustic, SMPS
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-196854 (URN)
Note

QC 20161124

The research presented here has received funding from he KTH Linn ́e FLOW Center, the Swedish Research Council (VR) and the European Unions Seventh Framework Programme (FP7) under Grant Agreement No. 604244 (Norosensor). 

Available from: 2016-11-24 Created: 2016-11-24 Last updated: 2016-11-25Bibliographically approved
5. The Influence of Air Flow Velocity and Particle Size on the Collection Efficiency of Electrostatic Aerosol Samplers
Open this publication in new window or tab >>The Influence of Air Flow Velocity and Particle Size on the Collection Efficiency of Electrostatic Aerosol Samplers
Show others...
(English)Manuscript (preprint) (Other academic)
Keyword
ESP, aerosol
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-196855 (URN)
Funder
Swedish Research CouncilEU, FP7, Seventh Framework Programme, 604244
Note

QC 20161124

The research presented here has received funding from he KTH Linné FLOW Center, the Swedish Research Council (VR) and the European Unions Seventh Framework Programme (FP7) under Grant Agreement No. 604244 (Norosensor). 

Available from: 2016-11-24 Created: 2016-11-24 Last updated: 2016-11-24Bibliographically approved

Open Access in DiVA

Ramin Imani Jajarmi(9345 kB)25 downloads
File information
File name FULLTEXT01.pdfFile size 9345 kBChecksum SHA-512
f6fc249d53c5970813b0f49fd9cbfd3758c439a6f9bc4dfedc71495eb9f107a13e68112b2fdf63f9a16c052e1d00c00266902cb87800bf75ac39e80048ac249d
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Imani Jajarmi, Ramin
By organisation
Fluid Physics
Fluid Mechanics and Acoustics

Search outside of DiVA

GoogleGoogle Scholar
Total: 25 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 57 hits
ReferencesLink to record
Permanent link

Direct link