| 1. |
- Berdugo Vilches, Teresa, 1985, et al.
(författare)
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Shedding light on the governing mechanisms for insufficient CO and H2 burnout in the presence of potassium, chlorine and sulfur
- 2020
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 273
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Tidskriftsartikel (refereegranskat)abstract
- Based on the experiences of insufficient burnout in industrial fluidized bed furnaces despite adequate mixing and availability of oxidizer, the influence of potassium on CO and H2 oxidation in combustion environments was investigated. The combustion environments were provided by a laminar flame burner in a range relevant to industrial furnaces, i.e. 845 °C to 1275 °C and excess air ratios ranging from 1.05 to 1.65. Potassium, in the form of KOH, was homogeneously introduced into the hot gas environments to investigate its effect on the radical pool. To quantitatively determine key species that are involved in the oxidation mechanism (CO, H2, KOH, OH radicals, K atoms), a combination of measurement systems was applied: micro-gas chromatography, broadband UV absorption spectroscopy and tunable diode laser absorption spectroscopy. The inhibition effect of potassium on CO and H2 oxidation in excess air was experimentally confirmed and attributed to the chain-terminating reaction between KOH, K atoms and OH radicals, which enhanced the OH radical consumption. The addition of chlorine or sulfur could reduce the concentrations of KOH and K atoms and consequently eliminated the inhibition on CO and H2 oxidation. Existing kinetic mechanisms underestimate the inhibiting effect of potassium and they fail to predict the effect of temperature on CO and H2 concentration when potassium and sulfur co-exist. This work advances the need to revise existing kinetic mechanisms to fully capture the interplay of K and S in the oxidation of CO and H2 in industrial fluidized bed furnaces.
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| 2. |
- Borggren, Jesper, et al.
(författare)
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Diode laser-based thermometry using two-line atomic fluorescence of indium and gallium
- 2017
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Ingår i: Applied Physics B: Lasers and Optics. - : Springer Science and Business Media LLC. - 0946-2171. ; 123:12
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Tidskriftsartikel (refereegranskat)abstract
- A robust and relatively compact calibration-free thermometric technique using diode lasers two-line atomic fluorescence (TLAF) for reactive flows at atmospheric pressures is investigated. TLAF temperature measurements were conducted using indium and, for the first time, gallium atoms as temperature markers. The temperature was measured in a multi-jet burner running methane/air flames providing variable temperatures ranging from 1600 to 2000 K. Indium and gallium were found to provide a similar accuracy of ~ 2.7% and precision of ~ 1% over the measured temperature range. The reliability of the TLAF thermometry was further tested by performing simultaneous rotational CARS measurements in the same experiments.
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| 3. |
- Borggren, Jesper, et al.
(författare)
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Spatially Resolved Temperature Measurements Above a Burning Wood Pellet Using Diode Laser-Based Two-Line Atomic Fluorescence
- 2018
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 72:6, s. 964-970
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Tidskriftsartikel (refereegranskat)abstract
- Diode laser-based two-line atomic fluorescence (TLAF) thermometry applied to flames of combusting wood pellets is demonstrated. The temperature above burning wood pellets placed in the hot product gas of gallium seeded laminar flames is measured. The calibration-free technique provides spatially resolved temperatures in one dimension with sufficient temporal resolution to resolve all combustion stages of a pellet, even in highly sooting flames. The temperature above a burning pellet was found to decrease due to the release of volatile gases and the accuracy and precision of the technique is assessed at flame temperatures.
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| 4. |
- Chen, Shuang, et al.
(författare)
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CH4/Air反扩散射流火焰多组分同步PLIF诊断
- 2018
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Ingår i: Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics. - 1672-9897. ; 32:1, s. 26-32
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Tidskriftsartikel (refereegranskat)abstract
- The simultaneous multi-species Planar Laser Induced Fluorescence technique plays an important role in studying the flame structure and the two-dimensional distribution of intermediate species in combustion. The experimental system of OH/CH2O/Acetone-PLIF was built in order to study the CH4-Air inverse diffusion jet (IDJ) flame. The system consists of two sets of lasers, two intensifier-CCD cameras, a temporal controller and several lenses. The strategy of fluorescence excitation, the method of synchronous timing control and image calibration procedures are discussed. The IDJ flame was studied using the simultaneous multi-species PLIF technique, and the reaction zone, pre-heating zone and fuel zone of IDJ flame were determined. Experimental results suggest that the IDJ flame is different from either the normal diffusion flame or the premixed jet flame. The behavior of this type of flame reveals similarity to the partially premixed flame. Compared to OH chemilumiscence images, simultaneous multi-species PLIF can provide more detail and information about the flame structure and it has huge potential in fundamental combustion studies and industrial burner experiments
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| 5. |
- Fatehi, Hesameddin, et al.
(författare)
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Numerical simulation of ignition mode and ignition delay time of pulverized biomass particles
- 2019
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 206, s. 400-410
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, numerical simulations were carried out to identify the mode of ignition and ignition delay time of pulverized biomass particles in hot flue gas produced by a methane/air flame. In the experiments, it was observed that for most biomass residues the dominant combustion mode was the staged gas-phase ignition in the surrounding gas followed by surface ignition at the char surface. There were some exceptions to this general trend, e.g. wheat straw particles, which ignited at the surface of the particle under some temperature conditions. Moreover, temporally and spectrally resolved images of the single burning particles were obtained in the experiments and CH* chemiluminescence at different stages of biomass conversion was recorded. In this study, by means of a detailed numerical model for conversion of biomass particles and employing detailed gas chemistry mechanism, the ignition mode and ignition delay time of the particles are studied. The model is able to distinguish between different ignition modes of the particles in agreement with the experimental data. The underlying physics behind shifting ignition mode from homogeneous ignition to heterogeneous ignition for wheat straw are discussed. The ignition delay times for different biomass sources at different conditions are calculated and the results are in good agreement with the experimental data. Apart from the detailed model, CFD simulations are performed to assess the flow and combustion process (temperature, O2 concentration and velocity difference between the ambient gas and the particle) around the particle. The CFD results show similar trends compared with the CH* chemiluminescence from the particle at different times during the devolatilization stage.
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| 6. |
- Fatehi, Hesameddin, et al.
(författare)
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Recent Development in Numerical Simulations and Experimental Studies of Biomass Thermochemical Conversion
- 2021
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Ingår i: Energy and Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 35:9, s. 6940-6963
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Forskningsöversikt (refereegranskat)abstract
- Biomass, as a renewable energy source, is available worldwide, is carbon neutral, and can be converted to various types of products depending on the market and on the specific applications. Among different technologies of biomass utilization, thermochemical conversion of biomass is the most efficient method with the shortest time scale of the process. Thermochemical conversion can be used to produce gas or liquid fuels, and it can be used for direct production of heat and electricity. Biomass thermochemical conversion is an active and fast growing field of research. New experimental methods with high spatial and temporal resolution such as laser diagnostics are being introduced, and numerical modeling of the physical and chemical details in biomass conversion is being conducted. In this review, we aim to provide an overview of the recent activities in the field of thermochemical conversion of biomass. Important parameters in the large scale conversion systems, such as temperature distribution, overall conversion rate of fuel, and distribution of different species, are strongly connected to the processes that occur on the scale of a single particle. Understanding the link between transport phenomena, chemical kinetics, and physical transformation on single particle scale can help to unravel issues such as emission and efficiency on the large scale. Hence, the focus of this review is on the single biomass particle, relevant to combustion and gasification systems. Special attention is paid to high fidelity numerical models and state-of-the-art experimental techniques that have been developed or employed over recent years to understand different aspects of biomass thermochemical conversion.
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| 7. |
- Gao, Qiang, et al.
(författare)
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Gas Temperature Measurement Using Differential Optical Absorption Spectroscopy (DOAS)
- 2018
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 72:7, s. 1014-1020
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Tidskriftsartikel (refereegranskat)abstract
- A nonintrusive method for flow gas temperature measurement using differential optical absorption spectroscopy (DOAS) was demonstrated. A temperature-dependent spectra (TDS) originated from the DOAS spectra of sulfur dioxide (SO2) in the wavelength range of 276–310 nm was introduced, and the relationship between the TDS and the temperature was built through experimental calibration process. This relationship is found to be independent of SO2 concentration and can be used for temperature measurements. The experimental results indicated that the precision of the TDS method is < ± 0.3% for SO2 concentrations higher than 150 ppm with the optical path length of 170 mm. For lower concentrations, the precision is estimated to be ± 0.4% at 1 ppm. The relative deviation between the temperature measured by the TDS method and that measured by a thermocouple is within 3% in the temperature range of 298–750 K, and the TDS method has a quicker response to the fast-changing temperature than the thermocouple.
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| 8. |
- Hot, Dina, et al.
(författare)
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Spatially and temporally resolved IR-DFWM measurement of HCN released from gasification of biomass pellets
- 2019
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 37:2, s. 1337-1344
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, to the best of the authors' knowledge, nonintrusive quantitative measurement of hydrogen cyanide (HCN) released during the devolatilization phase of straw pellets gasification is demonstrated with high spatial and temporal resolution. Mid-infrared degenerate four-wave mixing (IR-DFWM) measurements of HCN were performed by probing the interference-free P(20) line in the v 1 vibrational band at around 3 μm and the IR-DFWM signal was detected with an upconversion-based detector, providing discrimination of thermal noise and increased sensitivity. A novel single-pellet setup consisting of a multi-jet burner was used to provide hot flue gas environments with an even and well-defined temperature distribution, for single straw pellet gasification at atmospheric pressure. The environments had temperatures of 1380 K, 1540 K and 1630 K with a constant oxygen concentration of 0.5 vol%. In order to quantify the amount of HCN released during the devolatilization of straw pellets, calibration measurements were performed in well-defined HCN gas flows. Selected hot water lines were probed with IR-DFWM in the interrogated volume to obtain the instantaneous temperature, which were used to correct the temperature effect. HCN concentrations up to 1500 ppm were detected during the devolatilization stage, and the results indicate a strong temperature dependence of the HCN release.
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| 9. |
- Hwang, Ouk, et al.
(författare)
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Development of novel ultrasonic temperature measurement technology for combustion gas as a potential indicator of combustion instability diagnostics
- 2019
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 159
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a high-speed, fast responsive, non-intrusive ultrasonic thermometry system was proposed as a potential candidate for overcoming the disadvantages of thermocouples. The principle of this system is based on the thermal dependence of the speed of sound, and the temperature is measured by detecting the flight time of ultrasonic wave (USW) between the transmitter and the receiver. For a fast and exact measurement, the algorithm was developed as simple as possible, and the exact values of the physical properties, such as specific heat ratio and molecular weight of combustion gas, were taken from the computational calculation of CHEMKIN-Pro with GRI 3.0 mechanism. The performance of the system was verified by two experiments. First, the system was applied to measure the temperature of heated air. Results showed high precision with a 0.3% error when incorporating a modification equation and fast responsive dynamic performance, which directly reflect the rapid temperature change. Second, the combustion gas temperature above a multi-jet burner, which provides a horizontally uniform temperature distribution similar to a flat flame burner, was measured. Five different flame temperatures were measured using a thermocouple and an optic-based measurement method based on two-line atomic fluorescence (TLAF) as well as ultrasonic thermometry to compare their performances. Ultrasonic thermometry showed a slightly lower accuracy than those of TLAF and the thermocouple. This condition could be overcome by correcting the results using linear fitting, as the temperature measured by USW showed the best linearity among them. The USW technique showed excellent performance in terms of the measurement speed of 1000 samples/s and uncertainty under 0.73%. This USW thermometry of combustion gas can be applied to many combustion systems, including boilers and gas turbines. Specifically, fast temperature measurement at a speed of around 1 kHz enables the diagnosis of the combustion instability phenomenon, which is a difficult task when using conventional methods of temperature measurement. Furthermore, both dynamic pressure and temperature can be simultaneously measured at a high rate, thus synergistically increasing the accuracy of combustion instability diagnosis with sufficient information, such as the Rayleigh index or the flame transfer function.
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| 10. |
- Larsson, Kajsa, et al.
(författare)
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Quantitative Imaging of Ozone Vapor Using Photofragmentation Laser-Induced Fluorescence (LIF)
- 2017
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 71:7, s. 1578-1585
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, the spectral properties of gaseous ozone (O3) have been investigated aiming to perform quantitative concentration imaging of ozone by using a single laser pulse at 248 nm from a KrF excimer laser. The O3 molecule is first photodissociated by the laser pulse into two fragments, O and O2. Then the same laser pulse electronically excites the O2 fragment, which is vibrationally hot, whereupon fluorescence is emitted. The fluorescence intensity is found to be proportional to the concentration of ozone. Both emission and absorption characteristics have been investigated, as well as how the laser fluence affects the fluorescence signal. Quantitative ozone imaging data have been achieved based on calibration measurements in known mixtures of O3. In addition, a simultaneous study of the emission intensity captured by an intensified charge-coupled device (ICCD) camera and a spectrograph has been performed. The results show that any signal contribution not stemming from ozone is negligible compared to the strong fluorescence induced by the O2 fragment, thus proving interference-free ozone imaging. The single-shot detection limit has been estimated to ∼400 ppm. The authors believe that the presented technique offers a valuable tool applicable in various research fields, such as plasma sterilization, water and soil remediation, and plasma-assisted combustion.
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