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Particle Measurement Volume and Light Intensity in a Shadowgraph Imaging System
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.ORCID iD: 0000-0002-5324-002X
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
2018 (English)In: IST 2018 - IEEE International Conference on Imaging Systems and Techniques, Proceedings, IEEE, 2018, article id 8577170Conference paper, Published paper (Refereed)
Abstract [en]

A method is sought to find the measurement volume of an optical instrument for particle measurement is sought. The study shows that the measurement volume depends on a combination of the optical homogeneity of the illumination light and the camera system. The result from a mix of illumination cases and positions shows that, if the true size and the background brightness are known, the measurement volume can be determined with an average precision of four percent using adual term exponential fit. Using a lens with lower magnification increases the measurement volume since both the field of viewand the depth of field increase. However, a larger field of view increases the required amount of light as well as the sensitivity to other optical errors.

Place, publisher, year, edition, pages
IEEE, 2018. article id 8577170
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-34825DOI: 10.1109/IST.2018.8577170ISI: 000455657200028Scopus ID: 2-s2.0-85060703908ISBN: 978-1-5386-6628-9 (electronic)OAI: oai:DiVA.org:miun-34825DiVA, id: diva2:1258785
Conference
2018 IEEE International Conference on Imaging Systems and Techniques, IST 2018; Krakow; Poland; 16 October 2018 through 18 October 2018
Projects
SMART (Smarta system och tjänster för ett effektivt och innovativt samhälle)Available from: 2018-10-25 Created: 2018-10-25 Last updated: 2019-11-07Bibliographically approved
In thesis
1. Development and Test of an Imaging Instrument for Measurement of Water Droplets in Icing Conditions
Open this publication in new window or tab >>Development and Test of an Imaging Instrument for Measurement of Water Droplets in Icing Conditions
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Structural icing is a persistent challenge for the production of renewable energy from wind. It is mainly caused by supercooled atmospheric droplets of water, which are very common in cold climates. In the most exposed wind parks in Sweden, more than 10 per cent of annual energy production can be lost. Some properties of liquid water are included in current \gls{nwp} models and are used as input parameters for the estimation of icing, but they are rarely measured in-situ for verification or validation.

To address this problem, a new instrument was developed. This compilation thesis is a collection of five articles describing the development, testing and verification of this instrument. Finally, icing and ice loads are measured and compared with a standard model and a model using \gls{ai} and empirical data.

The new instrument, called \gls{dii}, is based on shadowgraph imaging using \gls{led} light as background illumination and digital image processing. The components were selected with the possibility of low-cost volume production in mind. The applications of a commercial instrument based on this technique include, for example, real-time in-situ icing condition measurements and assimilation and verification of data in \gls{nwp} models. The instrument, alongside a reference instrument, was tested in two locations with different icing conditions. Shadowgraph imaging and its limitations as a measurement method for droplet size and concentration were investigated.

The work presented shows that measurements of the size and concentration of water droplets using shadowgraph images can be used for the comparison and validation of \gls{nwp} models and other instruments. The \gls{cv} for a given value of the concentration is lower than \SI{1.6}{\percent} for droplets \SI{25}{\micro\meter} in diameter, based on uncertainty in the size measurement only. The accuracy of the sampling volume can be improved by measuring the background light intensity in the position of the measured droplet.

A fog chamber was used for initial tests. However, to evaluate models of ice accumulation, in-situ measurements are necessary. These measurements should use a temporal resolution of at least one sample per minute, preferably higher. With a limited amount of data, multivariate data analysis can be used to estimate the level of ice accretion. Together with a heuristic model of erosion/ablation, the resulting figures can be used to simulate the ice load.

All of the instruments, as well as many other components used during the described field measurements, did at some point break due to the difficult weather conditions. An instrument for measurement of icing conditions needs to be designed with high environmental protection and endurance. The results in the attached papers may help and motivate further technical development of instruments that can measure atmospheric liquid water in icing conditions.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2019. p. 68
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 306
Keywords
Icing measurements, field study, shadowgraph imaging, edge detection, LWC, MVD.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-37639 (URN)978-91-88947-22-2 (ISBN)
Public defence
2019-12-05, C326, Holmgatan 10, Sundsvall, 10:00 (English)
Opponent
Supervisors
Note

Vid tidpunkten för disputationen var följande delarbete opublicerat: delarbete 5 (accepterat).

At the time of the doctoral defence the following paper was unpublished: paper 5 (accepted). 

Available from: 2019-11-07 Created: 2019-11-07 Last updated: 2019-11-07Bibliographically approved

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Rydblom, StaffanThörnberg, Benny

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