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Quantifying ageing effects in thermochromic liquid crystal thermography as applied to transient convective heat transfer experiments

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journal contribution
posted on 20.08.2018, 13:31 authored by Carlos Les, Mark BrendMark Brend, Clare BonhamClare Bonham, Jon CarrotteJon Carrotte
Thermochromic liquid crystal (TLC) thermography is used in transient heat transfer experiments to determine distributions of convective heat transfer coefficient (HTC) inside models of internally cooled gas turbine engine components. As these components become more geometrically complex, the application of TLC thermography becomes increasingly challenging and additional sources of experimental uncertainty grow to be significant. The present work quantifies the uncertainties introduced by TLC ageing using a state-of-the-art imaging system and a new postprocessing methodology that are optimised for the intensity-based method of analysing TLC data. A coating comprising multiple TLCs with different active temperature ranges is considered and subject to 33 repeated thermal cycles. These repeated cycles are shown to increase the random and systematic uncertainties in the TLC measurements, resulting in consequent increases in the uncertainties associated with calculated HTCs. Increases in systematic uncertainty are caused by reflectance in the measured wavelength band moving to different temperatures, while increases in random uncertainty are related to changes in individual crystals or crystal clusters with ageing. Approaches to calibrating out increases in systematic uncertainty are proposed and recommended, but increases in random uncertainty will always persist unless the TLC coating is removed and reapplied.

Funding

This work was jointly funded by the EPSRC and Rolls-Royce plc. as part of the Centre for Doctoral Training in Gas Turbine Aerodynamics.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Aeronautical and Automotive Engineering

Published in

Measurement Science and Technology

Volume

29

Citation

LES, C. ...et al., 2018. Quantifying ageing effects in thermochromic liquid crystal thermography as applied to transient convective heat transfer experiments. Measurement Science and Technology, 29 (11), 115201.

Publisher

© IOP Publishing

Version

AM (Accepted Manuscript)

Publisher statement

This is an author-created, un-copyedited version of an article published in Measurement Science and Technology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6501/aadb24.

Acceptance date

16/08/2018

Publication date

2018-09-20

ISSN

0957-0233

Language

en