An algorithm for the characterisation of multi-exponential decay curves

Brübach, J.; Janicka, J.; Dreizler, Andreas

doi:10.1016/j.optlaseng.2008.07.015

Cited by 88 publications

(45 citation statements)

References 10 publications

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“…For the YSZ:Dy specimens, the slope of the slower decay curve was used for temperature measurement, as the black dash lines show ( Fig.2 (inset)). Because the values obtained from the exponential fits can be sensitive to the choice of the start and end of fitting window, a precisely defined time window is required which is only related to the decay time and independent of the settings of the acquisition system, as described by the previous work [29][30][31][32]. In this study, the fitting window starts at and ends at 0.5 times and 4.5 times of decay time, respectively, which yielded good results [31].…”

Section: Data Processingmentioning

confidence: 99%

Evaluation of the in-depth temperature sensing performance of Eu- and Dy-doped YSZ in air plasma sprayed thermal barrier coatings

Yang

Peng

Zhao

et al. 2017

Surface and Coatings Technology

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In-depth temperature sensing in air plasma sprayed (APS) thermal barrier coatings (TBCs) has been achieved with europium (Eu) and dysprosium (Dy) doped yttria stabilized zirconia (YSZ) sensor coatings. The luminescence properties of YSZ:Eu and YSZ:Dy, including spectrum, intensity and lifetime, were evaluated and their temperature sensing performances were compared using a lifetime-based measurement system. Both sensor TBCs display excellent temperature sensitivity in high temperature environment (400-800 °C for YSZ:Eu, 500-900 °C for YSZ:Dy) with a topcoat thickness up to 300 m. It was found that the upper limit of temperature sensing was determined by the ratio between luminescence intensity and background thermal radiation (signal-background-ratio). YSZ:Dy showed higher luminescent intensity than YSZ:Eu at elevated temperatures, and therefore displayed better temperature sensing performance with an increased limit. The effect of topcoat thickness on the temperature sensing performance was also evaluated, showing that the attenuation factor of YSZ increased significantly with topcoat thickness. * Corresponding author Tel./fax: +8621 54742561. E-mail address: xiaofengzhao@sjtu.edu.cn (Xiaofeng Zhao). 2Interestingly, it was found that the topcoat attenuation factor gradually decreased as temperature increased, which improved the temperature sensing performance of sensor TBCs at elevated temperature. The findings in the temperature sensing of APS TBCs provide basis for the future development of on-line APS TBCs temperature monitoring technology.

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Section: Data Processingmentioning

confidence: 99%

Evaluation of the in-depth temperature sensing performance of Eu- and Dy-doped YSZ in air plasma sprayed thermal barrier coatings

Yang

Peng

Zhao

et al. 2017

Surface and Coatings Technology

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“…The signal from the PMT was digitalized in an oscilloscope (PicoScope 3205B) and processed later in a computer. A single exponential fitting algorithm [21] was used to fit the experimental data and extract the life time decay, which was then correlated to temperature. The temperature dependence of the lifetime decay has been previously demonstrated in several publications [7][8][9][10][11].…”

Section: Optical Instrumentationmentioning

confidence: 99%

Temperature Sensing inside Thermal Barrier Coatings using Phosphor Thermometry

González

Pilgrim

Sollazzo

et al. 2014

IET &Amp; ISA 60th International Instrumentation Symposium 2014

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By introducing a few percent of rare earth oxides into existing Thermal Barrier Coating (TBC) materials, their functionality can be enhanced. The low fraction of the rare earth means the primary function of the coating as a thermal barrier can be maintained. However, it provides additional sensing capabilities. Embedded in the crystal, the rare earth ions act as optical centres making the material phosphorescent. The properties of the phosphorescence depend on temperature, among other parameters, such that the functional coating can be used to conduct phosphor thermometry. Accordingly, the temperature of the coating can be measured by exciting and detecting the phosphorescence from the coating. This technique has been under investigation for many years, although was only recently demonstrated on an operating gas turbine engine. Implementation of a phosphorescent measurement system was carried out in a Rolls-Royce jet engine using dysprosium doped yttrium stabilised zirconia as a sensor. During this implementation, a thermal gradient across the ceramic coating of some components of the engine existed due to cooling effects. This paper complements the previous work by investigating the effect on the temperature measurements accuracy of this thermal gradient.TBCs are translucent therefore the excitation light is expected to penetrate through the coating causing the phosphorescent response to be an integrated signal. When the thermal gradient through the coating thickness is significant relative to the measurement accuracy of the system then it might introduce ambiguity in the measurement. Therefore, the effect of the gradient must be considered independently. The focus of the current contribution is on the interpretation of temperature measurements from phosphorescent TBCs in a thermal gradient, such as those in the engine test. For the study, a specialised cyclic thermal gradient burner test rig was operated using equivalent instrumentation to that used for the engine test. This unique rig enables the controlled heating of the coatings at different temperature regimes. A longwavelength pyrometer was employed to detect the surface temperature of the coating. A correction was applied to compensate for changes in emissivity using two methods. A thermocouple was continuously used to measure the substrate temperature of the sample. Typical gradients across the coating are less than 1K/μm.The study successfully proved that the temperature indication from the phosphorescent TBC remains between the surface and substrate temperature for all operating conditions. This demonstrates the possibility of measuring inside the coating closer to the bond coat, using a fully doped coating to maintain signal strength.

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“…For the evaluation of the temperature-dependent luminescence lifetime t, an algorithm according to Brübach et al was applied [18]. The temporal waveform I(t) was fitted for each single-shot by a mono-exponential decay…”

Section: Lifetime Evaluationmentioning

confidence: 99%