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

Abstract

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.

Combined thermographic phosphor and digital image correlation (TP + DIC) for simultaneous temperature and strain measurements

“…Similar to IR + DIC, there are also numerous examples of TPs being combined with other diagnostics, such as particle image velocimetry (TP + PIV) and laser Doppler velocimetry (TP + LDV) to produce both full‐field velocity distributions and gas phase temperatures. [ 17‐20 ] Additionally, phosphors have been employed for combined temperature and strain measurements through Moiré interferometry [ 21,22 ] and more recently attempted with DIC. [ 23 ]…”

“…Translucent boxes show the two bandpass regions used in this work (λ 633 = 633 nm ± 10 nm and λ 660 =660 nm ± 5 nm), and arrows indicate trends with increasing temperature within those bands gas phase temperatures. [17][18][19][20] Additionally, phosphors have been employed for combined temperature and strain measurements through Moiré interferometry [21,22] and more recently attempted with DIC. [23] This work expands upon the idea to generate simultaneous measurements of strain and surface temperatures through TP + DIC.…”

Triple-layer remote phosphor structure: A potential packaging configuration to enhance both color quality and lumen efficiency of 6,000–8,500 K WLEDs

“…Several studies have previously analyzed the remote phosphor package for WLEDs, in which separation between the phosphor film and the LED chip is used to minimize the heating damages to the phosphor materials and to promote better lumen efficiency [11]. Enhanced light extraction by an internal reflection luminaire structure is introduced in this approach, and it is capable of enhancing the light extraction efficiency of WLEDs by at least 26% [12]. Additionally, another structure with an embedded air gap provides sufficient reflection of downward light to promote better luminescence [13].…”

Application of the laser induced phosphorescence method to the analysis of temperature distribution in heated and evaporating droplets

“…They provide useful information regarding the implementation of LIP thermography and properties of the phosphors, such as phosphorescence lifetimes, thresholds of thermal degradations, absorbed and emission spectra [18]. Some thermographic phosphors, including BAM:Eu (BaMgAl 10 O 17 :Eu 2+ ) [20,21,22,23], ZnO:Ga and ZnO:Zn [24], and La 2 O 2 S:Eu [25], have already been used in liquid flows and in some cases for studying the heating of droplets. The authors of [25] focused on the evaporation of acoustically levitated droplets, using the phosphorescence signal from La 2 O 2 S:Eu.…”