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Bo G Leckner - One of the best experts on this subject based on the ideXlab platform.
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measurement and theoretical prediction of char temperature oscillation during fluidized bed combustion
Combustion and Flame, 2018Co-Authors: Jesus Salinero, Diego Fuentescano, Alberto Gomezbarea, Bo G LecknerAbstract:There is experimental evidence of oscillations of the char particle temperature during combustion in a fluidized bed (FB), resulting from the movement of the char throughout the bed. However, in most theoretical FB combustion studies the char particle is assumed to always stay in the emulsion phase, and existing models do not take into account the movement of the char particle explicitly. Moreover, it is difficult to quantify the magnitude and frequency of these temperature oscillations with the common measurement techniques employed in FB (thermocouple and Pyrometry with optical probe). In this work, the combustion of single char particles (8 mm) from beech wood and sub-bituminous coal is carried out in a 2-dimensional FB made of quartz, using two O2 concentrations (11 and 21%v) in N2. The time-evolution of the temperature and the size of the char in the different phases are estimated by the analysis of images resulting from a new method combining Pyrometry with readings from a digital camera. It is found that the combustion temperature oscillates in hundredths of seconds with an amplitude varying from 10 to 100 °C, resulting from the movement of a particle between the emulsion, bubble and splash phases. The amplitude increases with higher O2 concentration and smaller char-particle size. A combustion model is developed using the experimental characterization of the movement of the char particle through the bed as input. The temperature and burnout time predicted by the model compare well (within 15 %) with measurements obtained from this work and from literature.
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impact of using thermocouples to measure char particle temperature in a fluidized bed combustor
12th International Conference on Fluidized Bed Technology CFB 2017 Krakow, 2017Co-Authors: Jesus Salinero, Diego Fuentescano, James J. Leahy, Alberto Gomezbarea, Bo G LecknerAbstract:Circulating fluidized bed can be applied in several methods of CO2 capture. In oxy-combustion the fuel particle temperature can peak in the regions near the entrance with high oxygen concentration, being a critical factor. To study this aspect, techniques to measure fuel particle temperature have been developed mainly based of thermocouples, where it is usually assumed that the thermocouple does not affect the movement of the fuel particle, although there is no rigorous evidence. In the present paper this aspect is studied by comparing the temperature of char particles with and without an embedded thermocouple (with 0.25 and 0.5 mm sheath diameters). Char particles (10 mm) are burnt in a laboratory fluidized bed made in quartz, allowing visual observation of the particles. The surface temperature is measured by Pyrometry coupled to a digital camera at the same time as the particle’s temperature is recorded by a thermocouple. The temperature of a char particle fluidized with an embedded thermocouple is shown to be higher than that of a freely fluidized char particle, and its burnout time is shorter. This is because the fluidization with a thermocouple makes the char particle sink in the bed, increasing its residence time in the bubble phase compared to the freely fluidized particle. Besides, this work shows how the Pyrometry technique is able to track the size and movement of a particle and its surface temperature gradients during conversion, improving the data collected with this method as compared to other measurement techniques.
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Measurement of char surface temperature in a fluidized bed combustor using Pyrometry with digital camera
Chemical Engineering Journal, 2016Co-Authors: Jesus Salinero, Alberto Gómez-barea, María Tripiana, Bo G LecknerAbstract:A method is presented to measure the char surface temperature during conversion in fluidized bed (FB) using a digital camera. The method applies one-color Pyrometry (P1C) sequentially for the three wavelength bands (red, green, and blue) changing from one band to another automatically as a function of radiation intensity received by the sensor of the video camera. Experiments were made in a twodimensional FB combustor (0.18x0.50x0.018 m) equipped with a window for visual observation. It is shown that the new method improves the accuracy compared to two-color Pyrometry (P2C), allowing the measurement of a wider range of temperature, including temperatures lower than the bed (background). The main limitation of P1C (compared to P2C) is that the char emissivity has to be known. However, a sensitivity analysis, assuming a char emissivity variation from 0.85 to 1, reveled that the relative error in temperature is lower than 1% when the surface temperature of the char is higher than that of the bed. Then an assumed value of emissivity within this range is sufficient. However, a more precise estimate of char emissivity is needed when measuring temperatures lower than the bed temperature. Furthermore, the method enables determination of details such as surface temperature gradients and size of the particle during combustion. Overall, the technique allows determination of precise data of the fuel conversion process in FB.
Jesus Salinero - One of the best experts on this subject based on the ideXlab platform.
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measurement and theoretical prediction of char temperature oscillation during fluidized bed combustion
Combustion and Flame, 2018Co-Authors: Jesus Salinero, Diego Fuentescano, Alberto Gomezbarea, Bo G LecknerAbstract:There is experimental evidence of oscillations of the char particle temperature during combustion in a fluidized bed (FB), resulting from the movement of the char throughout the bed. However, in most theoretical FB combustion studies the char particle is assumed to always stay in the emulsion phase, and existing models do not take into account the movement of the char particle explicitly. Moreover, it is difficult to quantify the magnitude and frequency of these temperature oscillations with the common measurement techniques employed in FB (thermocouple and Pyrometry with optical probe). In this work, the combustion of single char particles (8 mm) from beech wood and sub-bituminous coal is carried out in a 2-dimensional FB made of quartz, using two O2 concentrations (11 and 21%v) in N2. The time-evolution of the temperature and the size of the char in the different phases are estimated by the analysis of images resulting from a new method combining Pyrometry with readings from a digital camera. It is found that the combustion temperature oscillates in hundredths of seconds with an amplitude varying from 10 to 100 °C, resulting from the movement of a particle between the emulsion, bubble and splash phases. The amplitude increases with higher O2 concentration and smaller char-particle size. A combustion model is developed using the experimental characterization of the movement of the char particle through the bed as input. The temperature and burnout time predicted by the model compare well (within 15 %) with measurements obtained from this work and from literature.
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impact of using thermocouples to measure char particle temperature in a fluidized bed combustor
12th International Conference on Fluidized Bed Technology CFB 2017 Krakow, 2017Co-Authors: Jesus Salinero, Diego Fuentescano, James J. Leahy, Alberto Gomezbarea, Bo G LecknerAbstract:Circulating fluidized bed can be applied in several methods of CO2 capture. In oxy-combustion the fuel particle temperature can peak in the regions near the entrance with high oxygen concentration, being a critical factor. To study this aspect, techniques to measure fuel particle temperature have been developed mainly based of thermocouples, where it is usually assumed that the thermocouple does not affect the movement of the fuel particle, although there is no rigorous evidence. In the present paper this aspect is studied by comparing the temperature of char particles with and without an embedded thermocouple (with 0.25 and 0.5 mm sheath diameters). Char particles (10 mm) are burnt in a laboratory fluidized bed made in quartz, allowing visual observation of the particles. The surface temperature is measured by Pyrometry coupled to a digital camera at the same time as the particle’s temperature is recorded by a thermocouple. The temperature of a char particle fluidized with an embedded thermocouple is shown to be higher than that of a freely fluidized char particle, and its burnout time is shorter. This is because the fluidization with a thermocouple makes the char particle sink in the bed, increasing its residence time in the bubble phase compared to the freely fluidized particle. Besides, this work shows how the Pyrometry technique is able to track the size and movement of a particle and its surface temperature gradients during conversion, improving the data collected with this method as compared to other measurement techniques.
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Measurement of char surface temperature in a fluidized bed combustor using Pyrometry with digital camera
Chemical Engineering Journal, 2016Co-Authors: Jesus Salinero, Alberto Gómez-barea, María Tripiana, Bo G LecknerAbstract:A method is presented to measure the char surface temperature during conversion in fluidized bed (FB) using a digital camera. The method applies one-color Pyrometry (P1C) sequentially for the three wavelength bands (red, green, and blue) changing from one band to another automatically as a function of radiation intensity received by the sensor of the video camera. Experiments were made in a twodimensional FB combustor (0.18x0.50x0.018 m) equipped with a window for visual observation. It is shown that the new method improves the accuracy compared to two-color Pyrometry (P2C), allowing the measurement of a wider range of temperature, including temperatures lower than the bed (background). The main limitation of P1C (compared to P2C) is that the char emissivity has to be known. However, a sensitivity analysis, assuming a char emissivity variation from 0.85 to 1, reveled that the relative error in temperature is lower than 1% when the surface temperature of the char is higher than that of the bed. Then an assumed value of emissivity within this range is sufficient. However, a more precise estimate of char emissivity is needed when measuring temperatures lower than the bed temperature. Furthermore, the method enables determination of details such as surface temperature gradients and size of the particle during combustion. Overall, the technique allows determination of precise data of the fuel conversion process in FB.
Marshall B Long - One of the best experts on this subject based on the ideXlab platform.
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characterization on hetero homogeneous ignition of pulverized coal particle streams using ch chemiluminescence and 3 color Pyrometry
Fuel, 2016Co-Authors: Ye Yuan, Qiang Yao, Fengxuan Zhao, Marshall B LongAbstract:Abstract Two in situ optic methods on CH ∗ chemiluminescence and coal particle temperature, are newly applied to investigate the devolatilization/homogeneous and heterogeneous ignition behaviors of dispersed coal particle streams, with ambient temperature from 1200 K to 1800 K and oxygen mole fractions from 10% to 30%. The dispersed coal particles of 65–74 μm are injected into an optical Hencken flat-flame burner by a novel de-agglomeration feeder. First, the consecutive images through multiple filters near CH ∗ emission band, centered at 420 430 and 440 nm, are exquisitely processed to subtract the interferences from continuum blackbody radiation of particles and soots in the CH ∗ band. Then, the signal of CH ∗ chemiluminescence is capable of providing a good indicator of the coal devolatilization process. Secondly, 3 color Pyrometry is adopted to detect particle surface temperature and determine the heterogeneous ignition delay time. The prevalent devolatilization/homogeneous-ignition are observed at high temperatures (1500 and 1800 K) with apparent CH ∗ signals, whereas CH ∗ emission can rarely be detected in the initial stage of 1200 K case that implies a dominated heterogeneous ignition mode. The effect of oxygen concentration on devolatilization is further discussed. The particles temperatures history after injected into Hencken burner are represented by 3 color Pyrometry based on a two stage principle, and thus the role of oxygen in determining particle temperature and heterogeneous ignition is finally examined.
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soot and thin filament Pyrometry using a color digital camera
Proceedings of the Combustion Institute, 2011Co-Authors: Peter B Kuhn, B C Connelly, Mitchell D Smooke, Marshall B LongAbstract:Abstract A simple and compact temperature and soot volume fraction diagnostic technique based on ratio Pyrometry has been studied. Two different consumer digital single lens reflex cameras were evaluated for use as pyrometers. The incandescence from soot and a SiC filament was imaged at the three wavelengths of each camera’s color filter array (CFA). After characterization of the detector’s signal response curves, temperatures were calculated by two-color ratio Pyrometry using a lookup table approach. A SiC filament with known emissivity was shown to provide an absolute light intensity calibration, which further allows the soot volume fraction to be determined. Measurements were carried out on four different flames with varying levels of soot loading. The filament-derived gas temperature and soot temperature measurements have been compared with computational results and overall good agreement has been shown. Soot volume fraction measurements have been compared with previous LII results, with excellent agreement for both cameras tested.
Paul E. Desjardin - One of the best experts on this subject based on the ideXlab platform.
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two color Pyrometry based flame to fuel surface radiative heat flux diagnostic using flamelets
Combustion and Flame, 2021Co-Authors: Siddhant S. Aphale, Paul E. DesjardinAbstract:Abstract In this study, a non-intrusive two-color Pyrometry based radiative heat flux diagnostic is presented that accounts for the self-absorption effects. This diagnostic relies on looking up the flame temperature and soot volume fraction using the ratio of color intensities obtained from digital cameras and numerical solutions of 1D steady-state diffusion flames. Virtual two color Pyrometry of computed flame show a unique one-to-one mapping of strained flames with intensity ratio; thereby allowing flames to be indexed and creation of a two-color flamelet manifold (TCFM). The TCFM is a function of two variables; the ratio of red to green intensities (flame index) and physical distance to the stoichiometric surface defined using a level-set function. The developed diagnostic is used in upward flame spread experiments where an approximate flame hull reconstruction method is applied to provide the 3D level-set function and intensity ratio for use of TCFM to provide radiative absorption properties for 3D ray tracing. Accounting for self-absorption effects provide improved soot volume fraction estimates. The radiative heat flux estimates are found to be in very good agreement with literature and improved results are obtained near the flame base.
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Development of a non-intrusive radiative heat flux measurement for upward flame spread using DSLR camera based two-color Pyrometry
Combustion and Flame, 2019Co-Authors: Siddhant S. Aphale, Paul E. DesjardinAbstract:Abstract A non-intrusive flame to fuel surface radiative heat flux measurement technique is developed using two-color Pyrometry of front and side images of upward flame spread along poly(methyl methacrylate) (PMMA). Commercially available Nikon DSLR cameras are radiometrically calibrated to measure soot temperature from the red and green channels of the color images using two-color Pyrometry. A 3D ray tracing algorithm is developed to compute radiative heat flux from a sooting flame to the solid fuel surface. Computed heat fluxes are compared to convection corrected Schmidt–Boelter heat flux measurements located at the center of the sample and are shown to be within ± 6.5%. To the authors’ knowledge, this study is the first attempt to develop a non-intrusive radiative heat flux measurement using DSLR cameras and two-color Pyrometry. Flame height estimates using the computed heat flux values are in good agreement with visual observations and prior measurements reported in the literature.
Will P Asse - One of the best experts on this subject based on the ideXlab platform.
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hot spot generation and growth in shocked plastic bonded explosives studied by optical Pyrometry
Journal of Applied Physics, 2019Co-Authors: Will P Asse, Elinda P Johnso, Lawrence Salvatiiii, Dana D DloAbstract:The aggregate behavior of hot spots in shocked plastic-bonded explosives (PBX) was studied by nanosecond optical Pyrometry. The averaged thermal emission spectra from at least 25 tiny (50 μg) explo...
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dynamic absorption in optical Pyrometry of hot spots in plastic bonded triaminotrinitrobenzene
Applied Physics Letters, 2019Co-Authors: Will P Asse, Elinda P Johnso, Dana D DloAbstract:Herein, we demonstrate a methodology for performing optical Pyrometry in environments which are disadvantageous for typical Pyrometry applications by introducing additional fit parameters to account for absorption or emission which convolutes the thermal spectrum. Emission spectra from a plastic-bonded formulation of triaminotrinitrobenzene (TATB) shocked by 2–4 km s−1 impacts with Al flyer plates show significant deviations from graybody behavior. To extract reliable temperatures via optical Pyrometry, we fit the spectra to a combination of a graybody and either a Gaussian absorption or emission spectrum. We found that the absorption needed to fit the data corresponds well to the known pressure-dependent absorption of TATB and that the absorption model gives temperatures and emissivities in line with other explosives. By contrast, assuming molecular emission gives temperatures too low and emissivities that decrease as more materials react. We conclude that the nonthermal part of the spectrum is dominated by the absorption of unreacted TATB and accurate Pyrometry of TATB must either use our graybody plus absorption model or limit the spectral range of observation to above 650 nm.
