| 1. |
- Abou Nada, Fahd Jouda, et al.
(author)
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A first application of thermographic phosphors in a marine two-stroke diesel engine for surface temperature measurement
- 2014
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In: Proceedings of the ASME 2014 Internal Combustion Engine Division Fall Technical Conference (ICEF2014). ; , s. 001-001
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Conference paper (peer-reviewed)abstract
- Phosphor thermometry is applied for the first time in a large-bore two-stroke diesel engine. The work proves the practicality of phosphor thermometry in large-bore engines. The experiments were conducted on the MAN 4T50ME-X marine research engine equipped with an optical cylinder head. By employing a thin surface coating of CdWO4 phosphor, cycle resolved temperature measurements of the cylinder wall were obtained. Motored and fired engine operations were tested at engine loads covering the low and medium engine load range. Phosphor thermometry proved to be successful in retrieving the temperature with standard deviations ranging around 1-8 K. Experimental considerations like detector linearity, coating thickness and an automated phosphor calibration routine will be addressed.
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| 2. |
- Abou Nada, Fahd Jouda, et al.
(author)
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Development of an automatic routine for calibration of thermographic phosphors
- 2014
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In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2
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Journal article (peer-reviewed)abstract
- An automated routine for the continuous calibration of thermographic phosphors was developed as a replacement for the conventional calibration scheme that relied on fixed temperature points. The automated calibration routine was validated using Mg 3 F 2 GeO 4 :Mn as a calibration phosphor. Hardware and software aspects of the calibration process were addressed in this development. The hardware aspect included a new substrate design using a high performance alloy, the Hastelloy-C alloy, whereas the software aspect included an automated acquisition system which was capable of acquiring simultaneous thermocouple temperatures and phosphor decay waveform in real time. The design of the calibration process eliminates the need for a system in thermal equilibrium during a phosphor calibration measurement. Temperature ramping rates of up to 4 K min −1 were employed in the oven without a delay in the temperature response being measured between the phosphor and the thermocouples involved. In addition, the automated calibration setup allowed for detailed investigations on the effect of heat being delivered to the phosphor coating by the laser. These findings were confirmed by a simple heat transfer model, based on lumped system analysis. In comparison to the data acquisition performed at several fixed points with the conventional calibration scheme, the experiment duration was shortened by a factor of 4 with the overall accuracy improved by 1–2 K.
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| 3. |
- Abou Nada, Fahd Jouda, et al.
(author)
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Improved measurement precision in decay time‑based phosphor thermometry
- 2016
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In: Applied Physics B. - : Springer Science and Business Media LLC. - 1432-0649 .- 0946-2171. ; 122
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Journal article (peer-reviewed)abstract
- This study comprises a continuation of the previous efforts of the authors to characterize different sources of errors in phosphor thermometry based on the determination of luminescence decays from thermographic phosphors. Whereas earlier investigations focused on point detectors utilizing different sensor technology, this work presents a comparison of four PMTs that are identical in terms of their product type. These detectors are supposedly identical, but the investigations revealed that their response is strictly individual. This study also shows a linear excitation energy dependence for the decay time of cadmium tungstate (CdWO4), the phosphor being used in this work. In addition, the potential influence of the intense and short fluorescence peak preceding the weaker and longer exponential decay in some phosphor materials, was investigated using the electrical signal gating capability of the PMT. Finally, the evaluated decay time also appeared to be affected by the oscilloscope settings used when recording the phosphorescence signals. The presented results indicate that all operating parameters from the calibration measurement need to be rigorously reproduced in order to avoid systematic temperature errors in phosphor thermometry experiments that are based on reproducible measurements of the decay time. These results should be of more general interest also outside the phosphor community as the findings, presented herein, in principal concern all kinds of measurements that are dependent on reproducible measurements of signal shapes or time-transients.
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| 4. |
- Abou Nada, Fahd Jouda, et al.
(author)
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Investigation of the effect of engine lubricant oil on remote temperature sensing using thermographic phosphors
- 2016
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In: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 179, s. 568-573
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Journal article (peer-reviewed)abstract
- Phosphor thermometry, a remote temperature sensing technique, is widely implemented to measure the temperature of different combustion engines components. The presence of engine lubricant can influence the behavior of the applied sensor materials, known as thermographic phosphors, and thus leading to erroneous temperature measurements. The effect of two engine lubricants on decay times originating from six different thermographic phosphors was investigated. The decay time of each thermographic phosphor was investigated as a function of lubricant/phosphor mass ratio. Tests were conducted at temperatures around 293 K and 376 K for both lubricants. The investigations revealed that ZnO:Zn and ZnS:Ag are the only ones that exhibit a change of the decay time as function of the lubricant/phosphor mass ratio. While the remaining thermographic phosphors, namely BaMg2Al16O27:Eu (BAM), Al2O3-coated BaMg2Al16O27:Eu, La2O2S:Eu, Mg3F2GeO4:Mn, displayed no sensitivity of their characteristic decay time on to the presence of lubricant on the porous coating. Biases in the calculated temperature are to be expected if the utilized thermographic phosphor displays decay time sensitivity to the existence of the engine lubricant within the sensor. Such distortions are concealed and can occur undetected leading to false temperature readings for the probed engine component.
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| 5. |
- Abou Nada, Fahd Jouda, et al.
(author)
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On the automation of thermographic phosphor calibration
- 2014
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In: Proceedings of the 60th International Instrumentation Symposium.
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Conference paper (peer-reviewed)abstract
- Thermographic phosphors can be robust temperature remote sensors. The accuracy of the temperature measured by the phosphor is highly dependent on the quality of the phosphor calibration used. Conventionally, thermographic phosphors are calibrated by measuring a series of decay curves at known stable oven temperatures. The process is then repeated covering the thermal sensitivity range of the phosphor chosen. Heating and cooling rates of high temperature ovens are usually low. Also, thermal equilibrium of the system is required at each calibration temperature before acquiring luminescence decay curves. Thus, the process is usually time consuming and the number of calibration points achieved is limited to a couple of dozen points. This study presents and validates the development of an automatic routine for the calibration of thermographic phosphors. It was designed to continuously and simultaneously acquire phosphor decay curves along with their corresponding thermocouple temperatures. The developed routine required software and hardware improvements. An updated design of the calibration substrate was implemented to improve the thermal conditions during calibration. Thermal gradients were further studied using a heat transfer model. The routine implemented a specially designed sparsing algorithm that reduced the sampling rate of the decaying luminescence curve without influencing the calculated decay time. The upper heating rate is set at 4 K.min-1 due to limitation imposed by the ceramic calibration oven. The phosphors CdWO4 and Mg3F2GeO4:Mn were chosen to validate the finalized routine. After the completion of the calibration process, a library-based calibration is created as the final product. The automated calibration routine delivered an overall accuracy improvement of 1-2 K, reduced calibration duration by factor of four and provided the possibility of deriving signal recognition algorithms. The condensed calibration dataset produced by the proposed calibration routine was further employed to develop a novel signal shape recognition algorithm for temperature evaluation.
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| 6. |
- Abou Nada, Fahd Jouda, et al.
(author)
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Remote temperature sensing on and beneath atmospheric plasma sprayed thermal barrier coatings using thermographic phosphors
- 2016
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In: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 302, s. 359-367
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Journal article (peer-reviewed)abstract
- Investigations on remote temperature sensing of yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) at the surface and at the bond-coat/top-coat interface were carried out. Using Y2O3:Eu thermographic phosphor as an embedded temperature sensing layer, sub-surface temperature probing through 300 μm of atmospheric plasma sprayed YSZ is demonstrated. The Y2O3:Eu thermographic phosphor displays a temperature sensitivity ranging between 400 °C up to a maximum of 900 °C when utilizing the luminescence originating from the 611 nm emission band. Dysprosium stabilized zirconia (10 wt.% DySZ), a TBC material, is also investigated and established as a temperature sensor from 400 °C up to a temperature of 1000 °C using both the intensity decay time and emission intensity ratio methods. In addition, the luminescence of presumed optically inactive YSZ materials was spectroscopically investigated in terms of optical interferences caused by impurities. A validation temperature probing measurement through 300 μm of YSZ top-coat was successfully performed in a SGT-800 Siemens burner running at six different operating conditions in an atmospheric combustion rig.
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| 7. |
- Knappe, Christoph, et al.
(author)
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Comparison of photo detectors and operating conditions for decay time determination in phosphor thermometry
- 2012
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In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 83:9
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Journal article (peer-reviewed)abstract
- This work compares the extent of linear response regions from standard time-resolving optical detectors for phosphor thermometry. Different types of photomultipliers (ordinary and time-gated) as well as an avalanche photodiode were tested and compared using the phosphorescence decay time of cadmium tungstate (CdWO4). Effects originating from incipient detector saturation are revealed as a change in evaluated phosphorescence decay time, which was found to be a more sensitive measure for saturation than the conventional signal strength comparison between in- and output. Since the decay time of thermographic phosphors is used for temperature determination systematic temperature errors in the order of several tens of Kelvins may be introduced. Saturation from the initial intensity is isolated from temporally developed saturation by varying the CdWO4 decay time over the microsecond to nanosecond range, resultant of varying the temperature from 290 to 580 K. A detector mapping procedure is developed in order to identify linear response regions where the decay-to-temperature evaluations are unbiased. In addition, this mapping procedure generates a library of the degree of distortion for operating points outside of linear response regions. Signals collected in the partly saturated regime can thus be corrected to their unbiased value using this library, extending the usable detector operating range significantly. © 2012 American Institute of Physics.
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| 8. |
- Knappe, Christoph, et al.
(author)
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Investigation and compensation of the nonlinear response in photomultiplier tubes for quantitative single-shot measurements.
- 2012
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In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 83:3
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Journal article (peer-reviewed)abstract
- A concept for time-sensitive optical detectors is described that shows how to confirm whether the detection device is operating in the linear response regime. By evaluating the recorded time decay of a thermographic phosphor, even weak saturation effects far from obvious situations can be identified and further related to either optical or electrical saturation. The concept has been validated by running a PMT detector close to saturation and exposing it to the optical signal decay of two different thermographic phosphors, La(2)O(2)S:Eu and CdWO(4). It was confirmed that short but intense light exposures at the beginning of an individual time decay influence the detector response for the rest of the decaying signal including temporal areas, where the anode current has dropped well below the manufacturer specified current limit. Such situations are common when applying, e.g., phosphor thermometry where it is necessary to retrieve the full decay curve from a single-shot event, i.e., standard techniques based on single-photon counting are omitted. Finally, means of compensation are introduced in order to facilitate the retrieval of useful information from the measurement data when operation in the non-linear response regime is inevitable.
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| 9. |
- Knappe, Christoph, et al.
(author)
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Response Regime Studies on Standard Detectors for Decay Time Determination in Phosphor Thermometry
- 2013
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In: Temperature: Its Measurement and Control in Science and Industry, Vol 8. - : AIP. - 1551-7616 .- 0094-243X. ; 1552, s. 879-884
-
Conference paper (peer-reviewed)abstract
- This work compares the extent of linear response regimes from standard time-resolving optical detectors for phosphor thermometry. Different types of Photomultipliers (ordinary and time-gated) as well as an Avalanche Photodiode are tested and compared using the phosphorescent time decay of CdWO4 that ranges from 10 mu s down to a few ns within a temperature span of 290 to 580 K. Effects originating from incipient detector saturation, far from obvious to the operator's eye, are revealed as a change in evaluated phosphorescence decay time. Since the decay time of thermographic phosphors itself is used for temperature determination - systematic temperature errors up to several tens of Kelvins may be introduced by such detector saturation. A detector mapping procedure is suggested in order to identify linear response regions where the decay-to-temperature evaluation can be performed unbiased. Generation of such a library is highly recommended prior to any quantitative measurement attempt. Using this detector library, even signals collected in the partly saturated regime can be corrected to their unbiased value extending the usable detector operating range significantly. Further, the use of an external current-to-voltage amplifier proved useful for most applications in time-based phosphor thermometry helping to limit saturation effects whilst maintaining a reasonable bandwidth and signal outputs.
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| 10. |
- Mishra, Yogeshwar, et al.
(author)
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Sprays thermometry using two color LIF and SLIPI
- 2015
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In: E1-2-111. ; , s. 1-8
-
Conference paper (peer-reviewed)abstract
- Knowing the droplets temperature is of great importance in spray-assisted combustion devices as it directly affects the droplet evaporation rate. This information helps optimizing the fuel/air mixture formation for the improvement of combustion devices. To measure the temperature of spray droplets, optical techniques such as Rainbow-Refractrometry (for point-wise) and the two-color LIF ratio thermometry (for 2D) have been preferred to thermocouples due to their non-intrusive nature. However, in optically dense sprays, these techniques are affected by unwanted impedes such as multiple scattering of light, intensity reduction along the light propagation (laser extinction) and attenuation of the signal travelling from the incident plane to the detector. The multiple light scattering contains false signals emerging from the non-illuminated portions of the sprays and leads to erroneous measurement results as well as image blur. Thanks to SLIPI (Structured Laser Illumination Planar Imaging) these issues can be efficiently addressed. In addition, by using two-color LIF (Laser Induced Fluorescence), effects of laser extinction and signal attenuation can be canceled out from the image ratio. In this study, SLIPI is combined with the two-color/band LIF ratio approach using a temperature sensitive dye. Here Fluorescein is excited at 447 nm and emits a LIF signal peaking at 520 nm. This signal becomes redshifted as the temperature increases. We demonstrate, for the first time, the application of this novel approach for measuring the local temperature of a hollow cone (HC) spray in 2D. The water temperature in the presented measurements ranges from 20°C to 90°C while the liquid injection pressure is set to 20 bars. The measurement is calibrated in-situ with a thermocouple and the results from both the conventional and SLIPI two-color LIF detection schemes are compared. It is found that the SLIPI ratio shows a significant improvement in signal sensitivity and accuracy when compared to the results of the conventional planar imaging.
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| 11. |
- Mishra, Yogeshwar, et al.
(author)
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Thermometry in aqueous solutions and sprays using two-color LIF and structured illumination
- 2016
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In: Optics Express. - 1094-4087. ; 24:5, s. 4949-4963
-
Journal article (peer-reviewed)abstract
- In imaging, the detection of light originating from multiple scattering, indirect reflections and surrounding backgrounds are known to produce errors especially in intensity-ratio based measurements. SLIPI (Structured Laser Illumination Planar Imaging) is an imaging technique that significantly reduces the impact of such issues. In this study, SLIPI is combined with the two-color LIF (Laser Induced Fluorescence) ratio thermometry approach for measuring water temperature in both a cuvette and a hollow-cone spray. By removing the unwanted background interferences using SLIPI, we observe both significant improvements in terms of temperature sensitivity as well as more pronounced temperature gradients within the spray.
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