| 1. |
- Binder, Christian, 1988-, et al.
(författare)
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Phosphor Thermometry for In-Cylinder Surface Temperature Measurements in Diesel Engines
- 2019
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Ingår i: Measurement science and technology. - 0957-0233 .- 1361-6501.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Surface temperature measurements in technically relevant applications can be very hallenging and yet of great importance. Phosphor thermometry is a temperature measurement technique that has previously been employed in technically relevant applications to obtain surface temperature. The technique is based on temperature-dependent changes in a phosphor’s luminescence. To improve the accuracy and precision of temperature measurements with this technique, the present study considers, by way of example, the impact of conditions inside the cylinder of a diesel engine on decay time based phosphor thermometry. After an initial, general assessment of the effect of prevailing measurement conditions, this research investigates errors caused by soot luminosity, extinction, signal trapping and changes of phosphors’ luminescence properties due to exposure to the harsh environment. Furthermore, preferable properties of phosphors which are suitable for in-cylinder temperature measurements are discussed. 16 phosphors are evaluated, including four which – to the authors’ knowledge –have previously not been used in thermometry. Results indicate that errors due to photocathode bleaching, extinction, signal trapping and changes of luminescence properties may cause an erroneous temperature evaluation with temperature errors in the order of serval tens of Kelvin.
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| 2. |
- Binder, Christian, et al.
(författare)
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Phosphor thermometry for in-cylinder surface temperature measurements in diesel engines
- 2020
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 226
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Tidskriftsartikel (refereegranskat)abstract
- Phosphor thermometry is a temperature measurement technique that has previously been employed in technically relevant applications to obtain surface temperature. The technique is based on temperature-dependent changes in a phosphor's luminescence. To improve the accuracy and precision of temperature measurements with this technique, the present study considers, by way of example, the impact of conditions inside the cylinder of a diesel engine on decay time based single-shot phosphor thermometry measurements. After an initial, general assessment of the effect of prevailing measurement conditions, this research investigates errors caused by soot luminosity, extinction, signal trapping and changes of phosphors' luminescence properties due to exposure to the harsh environment. Furthermore, preferable properties of phosphors which are suitable for in-cylinder temperature measurements are discussed. 16 phosphors are evaluated, including LaAlGe2O7:Tm, YVO4:(Dy,Ce), ZnS:(Tm,Ag), and ZnS:(Tm,Li) which – to the authors' knowledge – have previously not been used in thermometry. Results indicate that errors due to photocathode bleaching, extinction, signal trapping and changes of luminescence properties may cause an erroneous temperature evaluation with temperature errors in the order of several tens of Kelvin.
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| 3. |
- Feuk, Henrik, et al.
(författare)
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Automated Phosphor Thermometry Lifetime Calibration of Multiple Phosphors and Emission Lines to above 1900 K
- 2022
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Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:12
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Tidskriftsartikel (refereegranskat)abstract
- A method is specified which enables lifetime calibration of multiple phosphors and emission lines at the same time to temperatures above 1900 K. The experimental setup and algorithm used for data collection and experimental equipment control are described. The phosphors were coated on an alumina oxide disc and the reference temperature was measured using three type B thermocouples. The algorithm automates the data collection process such that no input from an operator is required during operation. The potential systematic error in calibration temperature was evaluated and was less than 1% around 1400 K.
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| 4. |
- Feuk, Henrik, et al.
(författare)
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Impact of Methane and Hydrogen-Enriched Methane Pilot Injection on the Surface Temperature of a Scaled-Down Burner Nozzle Measured Using Phosphor Thermometry
- 2022
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - : MDPI AG. - 2504-186X. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- The surface temperature of a burner nozzle using three different pilot hardware configurations was measured using lifetime phosphor thermometry with the ZnS:Ag phosphor in a gas turbine model combustor designed to mimic the Siemens DLE (Dry Low Emission) burner. The three pilot hardware configurations included a non-premixed pilot injection setup and two partially premixed pilot injections where one had a relatively higher degree of premixing. For each pilot hardware configuration, the combustor was operated with either methane or hydrogen-enriched methane (H2/CH4: 50/50 in volume %). The local heating from pilot flames was much more significant for hydrogen-enriched methane compared with pure methane due to the pilot flames being in general more closely attached to the pilot nozzles with hydrogen-enriched methane. For the methane fuel, the average surface temperature of the burner nozzle was approximately 40 K higher for the partially premixed pilot injection configuration with a lower degree of mixing as compared to the non-premixed pilot injection configuration. In contrast, with the hydrogen-enriched methane fuel, the differences in surface temperature between the different pilot injection hardware configurations were much smaller due to the close-to-nozzle frame structure.
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| 5. |
- Feuk, Henrik, et al.
(författare)
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Investigating photomultiplier tube nonlinearities in high-speed phosphor thermometry using light emitting diode simulated decay curves
- 2021
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 92:12
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Tidskriftsartikel (refereegranskat)abstract
- Photomultiplier tube (PMT) nonlinearities relevant for single shot high-speed lifetime phosphor thermometry were investigated by simulating decay curves with a light emitting diode (LED) at repetition rates between 1 Hz and 10 kHz. The PMT gain, LED decay time, and background radiant flux were also varied to investigate their impact on the measured decay time error. Errors in the measured decay time due to nonlinear PMT performance lead to temperature measurement errors; therefore, having the measured decay time sensitive to only phosphor temperature is highly valuable for more reliable temperature measurements. Photocathode bleaching had a significant impact on the signal level linearity for PMTs with excitation frequency in the kHz regime but had a smaller impact on the decay time error. Space charge effects were most noticeable at high radiant flux levels and high repetition rates. Strong background radiant flux may lead to decay time errors, and a gateable photocathode could be an effective method to reduce decay time errors. The best decay time measurement configuration to maximize precision without sacrificing accuracy is to use PMT gain in the recommended range and the highest radiant flux where the PMT response is still linear. The degree of nonlinearity in the PMT response is partly detector dependent; therefore, the results in this work may differ among detectors; however, the analysis presented in this work provides guidelines for improving the temperature accuracy of kHz lifetime phosphor thermometry measurements.
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| 6. |
- Feuk, Henrik, et al.
(författare)
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Laser excitation effects in lifetime-based high-speed phosphor thermometry
- 2022
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- With high-speed phosphor thermometry becoming more established follows the need for an improved understanding of laser excitation induced measurement errors. With this aim in mind, the impact of kHz laser excitation on the lifetime method was investigated for the phosphors Mg3FGeO6:Mn (MFG) and YVO4:Tm. The results showed that significant measurement errors can occur for both phosphors. The Maximum Entropy Method (MEM) was utilized to observe changes in the distribution of decay time with changes in laser excitation fluence and repetition rate. In the light of this analysis, it was concluded that the changes in measured decay time and therefore measured temperature cannot be primarily attributed to laser heating for either phosphor. The dominant source of changes in the measured decay time is ascribed to changes in the distributions of decay time with laser fluence for YVO4:Tm and laser irradiance for MFG.
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| 7. |
- Feuk, Henrik
(författare)
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Lifetime Surface Phosphor Thermometry - Technique Developments, Sources of Error, and Applications
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Temperature is not only a fundamental aspect of everyday life, but it is also an essential metric for thermal conversion systems concerning efficiency, emissions, and component lifetime estimation. Therefore, a vast range of different methods to measure temperature has been developed. The technique of focus in this thesis is lifetime-based surface phosphor thermometry.In phosphor thermometry, one leverages the changes in luminescence of materials called phosphors to measure temperature. The spectral changes can result from shifts in the relative intensity of emission lines in the spectra or shifts in emission line wavelength with temperature. In addition, changes in the lifetime of the phosphorescence signal with temperature can be utilized for thermometry. Inorganic phosphors are ceramic substances that can operate with a range of luminescence activators. Most often, the luminescence originates from trivalent lanthanide ions or transition metal ions doped in a host crystal.Surface phosphor thermometry has the benefit of being a remote sensing technique, where one coats a phosphor on a surface of interest. This phosphor coating is then excited with a remote source, for example, pulsed laser light, and the phosphor luminescence is detected remotely. In this thesis, technology developments, error sources analysis, and applications of phosphor thermometry are presented. The technology developments present a high-temperature calibration system and a method for analyzing the lifetime components in the luminescence decay of phosphors in detail. An analysis of upconversion phosphors for temperature measurements beneath thermal barrier coatings and an investigation of high-temperature phosphors to 1900 K and their sensitivities to the oxygen content of the gas environment are also included in this work.The investigations into potential error sources include how PMT nonlinearity effects can influence the measured lifetime with excitation frequency from 10 Hz up to 10 kHz. In addition, the phosphor luminescence decay time impact of high repetition excitation was also investigated and analyzed to see potential error sources for temperature measurements.Phosphor thermometry was also used in two applications, including measuring the surface temperature of burning wood pellets and the surface temperature of a combustion nozzle in a down-scaled gas turbine combustor using hydrogen-enriched methane as fuel.
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| 8. |
- Feuk, Henrik, et al.
(författare)
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Sources of error for single-shot PMT-based phosphor thermometry in harsh conditions
- 2021
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Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 32:8
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates photomultiplier tube (PMT) nonlinearities, relevant for lifetime phosphor thermometry, at various decay times to assess and minimize the impact on temperature measurement accuracy. The focus is single-shot measurements performed in harsh environments where phosphor signal attenuation often is a concern. The sensitivity of decay time measurements to changing phosphorescence intensity is therefore investigated. The experimental results show that for the studied phosphors and detectors, shorter decay times between 20 ns and 6 µs, saturation effects in the PMTs decreased the measured decay time with increasing signal attenuation. For longer phosphorescence decay times, in the millisecond regime, nonlinearity effects led to an increase in the measured decay time with increasing signal attenuation. The specific detector nonlinearity response will vary among detectors, but the introduced methodology for detector analysis is a useful resource for assessing and improving accuracy in lifetime phosphor thermometry measurements.
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| 9. |
- Feuk, Henrik, et al.
(författare)
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Temperature resolved decay time components of Mg4FGeO6:Mn using the maximum entropy method
- 2023
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 94
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Tidskriftsartikel (refereegranskat)abstract
- A thermographic phosphor’s decay time distribution over its temperature-sensitive range was retrieved with the Maximum Entropy Method (MEM). A decay time distribution consists of a range of decay times, each with an associated weighting for the decay time component’s prevalence in the analyzed decay curve. With the MEM, significant decay time contributions of a decay curve have high weighting and are therefore found as peaks in the decay time distribution, where the width and peak value are correlated with the relative weight of the decay time components. These peaks in the decay time distribution give increased insight into a phosphor’s lifetime behavior, which often cannot accurately be represented by a single or even two decay time components. The changes in the location of peaks in the decay time distribution with temperature can be used for thermometry, and this method has the benefit of being less sensitive to the multi-exponentiality of phosphor decay than mono-exponential decay time fitting. The method also resolves the underlying decay components with no assumptions of the number of significant decay time components. Initially, when the decay time distribution of Mg4FGeO6:Mn was captured, the collected decay included decaying luminescence from the alumina oxide tube in the tube furnace. Therefore, a second calibration was performed where the luminescence from the alumina oxide tube was minimized. These two calibration datasets were used to demonstrate that the MEM could characterize decays from two separate sources simultaneously.
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| 10. |
- Feuk, Henrik, et al.
(författare)
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Upconversion phosphor thermometry for use in thermal barrier coatings
- 2023
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Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 34:6
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Tidskriftsartikel (refereegranskat)abstract
- Measuring the temperature below the surface of a thermal barrier coating (TBC) using a thin phosphor layer is challenging primarily due to the absorption and scattering of laser excitation light and phosphor luminescence as they propagate through the coating. One way to increase phosphor luminescence could be to use upconversion phosphor thermometry, which is investigated in the current study. It is attractive because using longer excitation wavelengths reduces the absorption and scattering in TBCs as 8% wt. yttria-stabilize zirconia (8YSZ) generally has lower scattering and absorption coefficients around 1000 nm than at 532 and 355 nm. Therefore, the viability of upconversion to measure the temperature at the bottom of a TBC was evaluated for the first time and was compared with the more conventional downconversion phosphor thermometry. The current work involved an experimental study of several phosphors with lanthanides doped in the 8YSZ host, which were excited through downconversion by pulsed 355 nm and 532 nm laser light and through upconversion with 965 nm laser light. The YSZ:Er,Yb and YSZ:Ho,Yb phosphors show promise for upconversion phosphor thermometry. The experimentally acquired optical phosphor characteristics were used to simulate laser light and phosphor luminescence propagation in TBCs using Kubelka–Munk theory. This was to evaluate the signal strength with upconversion excitation compared to downconversion excitation. Upconversion excitation resulted greater signal strength from an embedded phosphor layer than 532 nm excitation and much higher than 355 nm excitation. Upconversion lifetime phosphor thermometry also resulted in improved phosphor lifetime temperature sensitivity. Coupled with reduced interference from background luminescence from impurities in TBCs with upconversion, it is a promising method for temperature measurements with the thermographic phosphor embedded in or underneath a TBC.
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