Turbulent heat flux measurement in a non-reacting round jet, using BAM:Eu2+ phosphor thermography and particle image velocimetry

Lee, Hyunchang; Böhm, Benjamin; Sadiki, A.; Dreizler, Andreas

doi:10.1007/s00340-016-6484-y

Cited by 26 publications

(29 citation statements)

References 42 publications

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“…These spectral bands were selected by appropriate bandpass filters and are denoted as “blue” (S ph blue ) and “red” (S ph red ) channels. For a thermographic phosphor such as Y 2 O 3 :Eu, the intensity ratio ( r ) of the “blue” and “red” filter band is a function (equation (2)) of the phosphorescence quantum yield in each channel 41 :…”

Section: Methodsmentioning

confidence: 99%

“…Spectral bands must be properly selected to combine as best as possible a high temperature sensitivity with high luminescence intensities 41 . For this purpose, the emission spectra of Y 2 O 3 :Eu hollow microspheres were recorded upon UV excitation in an electrical tube furnace using a Czerny-Turner type spectrometer in combination with a CMOS camera.…”

Section: Methodsmentioning

confidence: 99%

“…Images with too low/too high densities were excluded from further processing. Too high densities of aerosolized microspheres are prohibitive due to multiple scattering that causes systematic errors 41 . For identifying individual microspheres in a first step, an intensity threshold of 50 counts was applied to the images of the “red” and 20 counts to the “blue” channel to remove remaining background noise.…”

Section: Methodsmentioning

confidence: 99%

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Multiscale and luminescent, hollow microspheres for gas phase thermometry

Bischoff

Stephan

Birkel

et al. 2018

Sci Rep

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Recently developed laser-based measurement techniques are used to image the temperatures and velocities in gas flows. They require new phosphor materials with an unprecedented combination of properties. A novel synthesis procedure is described here; it results in hierarchically structured, hollow microspheres of Eu3+-doped Y2O3, with unusual particle sizes and very good characteristics compared to full particles. Solution-based precipitation on polymer microballoons produces very stable and luminescent, ceramic materials of extremely low density. As a result of the – compared to established template-directed syntheses – reduced mass of polymer that is lost upon calcination, micron-sized particles are obtained with mesoporous walls, low defect concentrations, and nanoscale wall thicknesses. They can be produced with larger diameters (~25 µm) compared to known hollow spheres and exhibit an optimized flow behavior. Their temperature sensing properties and excellent fluidic follow-up behavior are shown by determining emission intensity ratios in a specially designed heating chamber. Emission spectroscopy and imaging, electron microscopy and X-ray diffraction results are presented for aerosolizable Y2O3 with an optimized dopant concentration (8%). Challenges in the field of thermofluids can be addressed by combined application of thermometry and particle image velocimetry with such hollow microparticles.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Multiscale and luminescent, hollow microspheres for gas phase thermometry

Bischoff

Stephan

Birkel

et al. 2018

Sci Rep

Self Cite

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“…While flow velocity measurements using these particles are accomplished by the conventional use of the Mie scattered laser light as in the particle image velocimetry (PIV) or in laser Doppler velocimetry (LDV) techniques, phosphor thermometry exploits the temperature dependence of the luminescence properties of the particles, by detecting the emission following laser excitation [1][2][3][4][5][6]. If micrometer-size particles are used, they rapidly respond to changes in fluid temperature and flow velocity (< 100 μs in air at 800 K [3]).…”

Section: Introductionmentioning

confidence: 99%

“…The intensity ratio approach, in which the ratio of two spectral regions of the emission spectrum is temperature dependent, has been used extensively for planar excitation flow temperature measurements e.g. [1][2][3][4][5]. Also we have recently demonstrated a point measurement technique for flow temperature and velocity measurements, which is based on detecting the luminescence and Mie scattering signals of individual phosphor particles crossing continuous wave (CW) laser beams using photomultiplier tubes (PMTs) [6].…”

Section: Introductionmentioning

confidence: 99%

Thermographic laser Doppler velocimetry using the phase-shifted luminescence of BAM:Eu^2+ phosphor particles for thermometry

Ojo¹,

Fond²,

Abram³

et al. 2017

Opt. Express

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Simultaneous point measurements of gas velocity and temperature were recently demonstrated using thermographic phosphors as tracer particles. There, continuous wave (CW) excitation was used and the spectral shift of the luminescence was detected with a two-colour intensity ratio method to determine the gas temperature. The conventional laser Doppler velocimetry (LDV) technique was employed for velocimetry. In this paper, an alternative approach to the gas temperature measurements is presented, which is instead based on the temperature-dependence of the luminescence lifetime. The phase-shift between the luminescence signal and time-modulated excitation light is evaluated for single BaMgAl10O17:Eu 2+ phosphor particles as they cross the probe volume. Luminescence lifetimes evaluated in the time domain and frequency domain indicate that in these experiments interferences from in-phase signals such as stray excitation laser light are negligible. The dependence of the phase-shift on flow temperature is characterised. In the temperature sensitive range above 700 K, precise gas temperature measurements can be obtained (8.6 K at 840 K) with this approach.

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