Measurement uncertainty budget of an interferometric flow velocity sensor

Research output: Contribution to book/Conference proceedings/Anthology/ReportConference contributionContributedpeer-review

Contributors

Abstract

Flow rate measurements are a common topic for process monitoring in chemical engineering and food industry. To achieve the requested low uncertainties of 0:1% for flow rate measurements, a precise measurement of the shear layers of such flows is necessary. The Laser Doppler Velocimeter (LDV) is an established method for measuring local flow velocities. For exact estimation of the flow rate, the flow profile in the shear layer is of importance. For standard LDV the axial resolution and therefore the number of measurement points in the shear layer is defined by the length of the measurement volume. A decrease of this length is accompanied by a larger fringe distance variation along the measurement axis which results in a rise of the measurement uncertainty for the flow velocity (uncertainty relation between spatial resolution and velocity uncertainty). As a unique advantage, the laser Doppler profile sensor (LDV-PS) overcomes this problem by using two fan-like fringe systems to obtain the position of the measured particles along the measurement axis and therefore achieve a high spatial resolution while it still offers a low velocity uncertainty. With this technique, the flow rate can be estimated with one order of magnitude lower uncertainty, down to 0:05% statistical uncertainty.1 And flow profiles especially in film flows can be measured more accurately. The problem for this technique is, in contrast to laboratory setups where the system is quite stable, that for industrial applications the sensor needs a reliable and robust traceability to the SI units, meter and second. Small deviations in the calibration can, because of the highly position depending calibration function, cause large systematic errors in the measurement result. Therefore, a simple, stable and accurate tool is needed, that can easily be used in industrial surroundings to check or recalibrate the sensor. In this work, different calibration methods are presented and their influences to the measurement uncertainty budget of the sensor is discussed. Finally, generated measurement results for the film flow of an impinging jet cleaning experiment are presented.

Details

Original languageEnglish
Title of host publicationOptical Measurement Systems for Industrial Inspection X
EditorsPeter Lehmann, Armando Albertazzi Goncalves, Wolfgang Osten
PublisherSPIE - The international society for optics and photonics
ISBN (electronic)9781510611030
Publication statusPublished - 2017
Peer-reviewedYes

Publication series

SeriesProceedings of SPIE - The International Society for Optical Engineering
Volume10329
ISSN0277-786X

Conference

TitleOptical Measurement Systems for Industrial Inspection X 2017
Duration26 - 29 June 2017
CityMunich
CountryGermany

Keywords

Keywords

  • flow velocity measurement, laser Doppler profile sensor, LDA, measurement uncertainty, shear layer, wall shear stress