Open AccessHigh-precision flow temperature imaging using ZnO thermographic phosphor tracer particles
Author(s) -
Christopher Abram,
Benoît Fond,
Frank Beyrau
Publication year - 2015
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.23.019453
Subject(s) - materials science , phosphor , fluence , optics , laser , temperature measurement , luminescence , particle image velocimetry , repeatability , tracer , atmospheric temperature range , turbulence , optoelectronics , physics , chemistry , chromatography , quantum mechanics , meteorology , nuclear physics , thermodynamics
Zinc oxide (ZnO) particles are characterised as a tracer for temperature measurements in turbulent flows, in the context of the thermographic particle image velocimetry technique. Flow measurements are used to compare the temperature precision of ZnO to that obtained using a well-characterised thermographic phosphor, BAM:Eu(2+), under the same conditions. For this two-colour, ratio-based technique the strongly temperature-dependent redshift of the luminescence emission of ZnO offers improved temperature sensitivity, and so at room temperature a threefold increase in the temperature precision is achieved. A dependence of the intensity ratio on the laser fluence is identified, and additional measurements with different laser pulse durations are used to independently show that there is also a dependence on the laser excitation irradiance, irrespective of fluence. A simple method to correct for these effects is demonstrated and sources of error are analysed in detail. Temperature images in a Re = 2000 jet of air heated to 363 K with a precision of 4 K (1.1%) are presented. The sensitivity of ZnO increases across the tested temperature range 300-500 K, so that at 500 K, using a seeding density of 2 x 10(11) particles/m(3), a precision of 3 K (0.6%) is feasible. This new phosphor extends the capabilities of this versatile technique toward the study of flows with small temperature variations.