| 1. |
- Baudoin, Eric, et al.
(författare)
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Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames
- 2013
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Ingår i: Flow, Turbulence and Combustion. - : Springer Science and Business Media LLC. - 1573-1987 .- 1386-6184. ; 90:2, s. 269-284
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedThe stabilization characteristics and local extinction structures of partially premixed methane/air flames were studied using simultaneous OH-PLIF/PIV techniques, and large eddy simulations employing a two-scalar flamelet model. Partial premixing was made in a mixing chamber comprised of two concentric tubes, where the degree of partial premixing of fuel and air was controlled by varying the mixing length of the chamber. At the exit of the mixing chamber a cone was mounted to stabilize the flames at high turbulence intensities. The stability regime of flames was determined for different degree of partial premixing and Reynolds numbers. It was found that in general partially premixed flames at low Reynolds numbers become more stable when the level of partial premixing of air to the fuel stream decreases. At high Reynolds numbers, for the presently studied burner configuration there is an optimal partial premixing level of air to the fuel stream at which the flame is most stable. OH-PLIF images revealed that for the stable flames not very close to the blowout regime, significant local extinction holes appear already. By increasing premixing air to fuel stream successively, local extinction holes grow in size leading to eventual flame blowout. Local flame extinction was found to frequently attain to locations where locally high velocity flows impinging to the flame. The local flame extinction poses a future challenge for model simulations and the present flames provide a possible test case for such study.
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| 2. |
- Baudoin, Eric, et al.
(författare)
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Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames
- 2011
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Ingår i: Proceedings of the 17th Mediterranean Combustion symposium, MCS 7. - 9788888104126
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Konferensbidrag (refereegranskat)abstract
- The stabilization characteristics and local extinction structures of partially premixed methane/air flames were studied using simultaneous OH-PLIF/PIV techniques, and large eddy simulations employing a two-scalar flamelet model. Partial premixing was made in a mixing chamber comprised of two concentric tubes, where the degree of partial premixing of fuel and air was controlled by varying the mixing length of the chamber. At the exit of the mixing chamber a cone was mounted to stabilize the flames at high turbulence intensities. The stability regime of flames was determined for different degree of partial premixing and Reynolds numbers. It was found that in general partially premixed flames at low Reynolds numbers become more stable when the level of partial premixing of air to the fuel stream decreases. At high Reynolds numbers, for the presently studied burner configuration there is an optimal partial premixing level of air to the fuel stream at which the flame is most stable. OH-PLIF images revealed that for the stable flames not very close to the blowout regime,significant local extinction holes appear already. By increasing premixing air to fuel stream successively, local extinction holes grow in size leading to eventual flame blowout. Local flame extinction was found to frequently attain to locations where locally high velocity flows impinging to the flame. The local flame extinction poses a future challenge for model simulations and the present flames provide a possible test case for such study.
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| 3. |
- Hu, C., et al.
(författare)
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Different control strategies for MEA based chemical absorption
- 2021
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Ingår i: Energy Proceedings. - : Scanditale AB.
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Konferensbidrag (refereegranskat)abstract
- When capturing CO2 from biomass fired combined heat and power plants, the dynamic changes in the feedstock and the heat and electricity demands can clearly affect the operation of the boiler, which can further affect the performance of chemical absorption CO2 capture. To handle such dynamic changes, control systems are needed. This work aims to compare the performance of two control strategies that can control the reboiler duty in the stripper to achieve a constant capture rate. Control strategy A uses the reboiler temperature as input based on a PID controller; and control strategy B is a modification of control strategy A by introducing a feedforward compensation based on the flowrate of rich solution when regulating the reboiler duty. Based on dynamic simulations, it is found that control strategy B can reduce the settling time and capture more CO2 with a lower average energy penalty within a certain time length.
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| 4. |
- Jin, Xin, et al.
(författare)
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Comparative evaluations of thermofluidic characteristics of sandwich panels with X-lattice and Pyramidal-lattice cores
- 2018
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 127, s. 268-282
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Tidskriftsartikel (refereegranskat)abstract
- This study compares the thermo-fluidic characteristics of sandwich panels with the X-lattice and the Pyramidal lattice at a given porosity and surface area density. The numerical model is validated against available experimental data at first. At a given Reynolds number in the range of 3100–5700, numerical results reveal that the X-lattice sandwich panel provides a 47–60% higher average overall Nusselt number. The special topology of the X-lattice induces counter-rotating spiral primary flow and more complex secondary flows, including one which becomes a longitudinal vortex later. The flow in the Pyramidal lattice sandwich panel is composed of a parallel primary flow and a counter-rotating vortex pair entrenched in the zone behind ligaments of the Pyramidal lattice. Compared with the Pyramidal lattice sandwich panel, endwall heat transfer of the X-lattice sandwich panel is enhanced by 75–97% and the ligaments surface heat transfer is enhanced by 85–97% at a given Reynolds number. It is also found that the friction factor of the X-lattice sandwich panel is about 2 times higher for the spiral primary flow and more complex secondary flows induced by the staggered ligaments. Finally, at a given pumping power, the cooling performance of the X-lattice is much better, too. Taking the identical fabrication method and cost into account, apparently the X-lattice is superior in engineering applications.
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| 5. |
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| 6. |
- Lin, Feng, et al.
(författare)
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Functional studies of HLA and its role in SARS-CoV-2: Stimulating T cell response and vaccine development
- 2023
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Ingår i: Life Sciences. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0024-3205 .- 1879-0631. ; 315
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Forskningsöversikt (refereegranskat)abstract
- In the biological immune process, the major histocompatibility complex (MHC) plays an indispensable role in the expression of HLA molecules in the human body when viral infection activates the T-cell response to remove the virus. Since the first case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in 2019, how to address and prevent SARS-CoV-2 has become a common problem facing all mankind. The T-cell immune response activated by MHC peptides is a way to construct a defense line and reduce the transmission and harm of the virus. Presentation of SARS-CoV-2 antigen is associated with different types of HLA phenotypes, and different HLA phenotypes induce different immune responses. The prediction of SARS-CoV-2 mutation information and the design of vaccines based on HLAs can effectively activate autoimmunity and cope with virus mutations, which can provide some references for the prevention and treatment of SARS-CoV-2.
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| 7. |
- Liu, Changye, et al.
(författare)
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Structures and burning velocity of biomass derived gas flames
- 2010
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 1879-3487 .- 0360-3199. ; 35:2, s. 542-555
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Tidskriftsartikel (refereegranskat)abstract
- Biomass derived gases produced via gasification, pyrolysis, and fermentation are carbon neutral alternative fuels that can be used in gas turbines, furnaces, and piston engines. To make use of these environmentally friendly but energy density low fuels the combustion characteristics of these fuels have to be fully understood. In this study the structure and laminar burning velocity of biomass derived gas flames are investigated using detailed chemical kinetic simulations. The studied gaseous fuels are the air-blown gasification gas, co-firing of gasification gas with methane, pyrolysis gases, landfill gases, and syngas, a mixture of carbon monoxide and hydrogen. The simulated burning velocities of reference fuel mixtures using two widely used chemical kinetic mechanisms, GRI Mech 3.0 and the San Diego mechanism, are compared with the experimental data to explore the uncertainties and scattering of the simulation data. The different chemical kinetic mechanisms are shown to give a reasonable agreement with each other and with experimental data, with a discrepancy within 7% over most of the conditions. The results show that the structures of typical landfill gas flames and co-firing of methane/gasification gas flames share essential similarity with methane flames. The reaction zones of these flames consist of a thin inner layer and a relatively thick CO/H-2 oxidation layer. In the inner layer hydrocarbon fuel (methane) is converted through chain reactions to intermediates such as CH3, CH2O, CO, H-2, etc. The structures of gasification gas flames, pyrolysis gas flames, syngas flames share similarity with the oxidization layer of the methane/air flames. Overall, the chemical reactions of all biomass derived gas flames occur in thin zones of the order of less than 1 mm. The thickness of all BDG gas flames is inversely proportional to their respective laminar burning velocity. The laminar burning velocities of landfill gases are found to increase linearly with the mole fraction of methane in the mixtures, whereas for gasification gas, syngas and pyrolysis gas where hydrogen is present, the laminar burning velocities scale linearly with the mole fraction of hydrogen. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
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| 8. |
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| 9. |
- Qi, Tian, et al.
(författare)
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Biomass steam gasification in bubbling fluidized bed for higher-H 2 syngas : CFD simulation with coarse grain model
- 2019
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 44:13, s. 6448-6460
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive coarse grain model (CGM) is applied to simulation of biomass steam gasification in bubbling fluidized bed reactor. The CGM was evaluated by comparing the hydrodynamic behavior and heat transfer prediction with the results predicted using the discrete element method (DEM) and experimental data in a lab-scale fluidized bed furnace. CGM shows good performance and the computational time is significantly shorter than the DEM approach. The CGM is used to study the effects of different operating temperature and steam/biomass (S/B) ratio on the gasification process and product gas composition. The results show that higher temperature enhances the production of CO, and higher S/B ratio improves the production of H 2 , while it suppresses the production of CO. For the main product H 2 , the minimum relative error of CGM in comparison with experiment is 1%, the maximum relative error is less than 4%. For the total gas yield and H 2 gas yield, the maximum relative errors are less than 7%. The predicted concentration of different product gases is in good agreement with experimental data. CGM is shown to provide reliable prediction of the gasification process in fluidized bed furnace with considerably reduced computational time.
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| 10. |
- Shen, Beibei, et al.
(författare)
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Forced convection and heat transfer of water-cooled microchannel heat sinks with various structured metal foams
- 2017
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 113, s. 1043-1053
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Tidskriftsartikel (refereegranskat)abstract
- The excellent performance of metal foams is well-recognized in the thermal and energy fields. This paper presents an investigation on the convective heat transfer and thermal performance of microchannel heat sinks with different structures of metal foams, such as Y-shaped, metal foam attached to fins, combined metal foams. The inlet Reynolds number is ranging from 170 to 554 and the porosity of the metal foam is ranging from 0.7 to 0.9. The detailed thermal performance and flow characteristics are presented and analyzed by using computational fluid dynamics with a verified computational model. The influences of flow velocity and porosity of the metal foam on the flow and heat transfer characteristics in a microchannel are also observed. It is found that different configurations and locations of metal foam in microchannel result in different heat transfer characteristics. The microchannel heat sinks with combined metal foams have better overall thermal performance than the other two models because it possesses the advantages of mixing fluid flow caused by Y-shaped metal foam and contacting the fins closely. Therefore, properly designed configurations of metal foams can further enhance the microchannel heat sink cooling capacity. Besides, the porosities have a small effect on the thermal performance but have a larger effect on the pressure drop.
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| 11. |
- Xiong, Yan, et al.
(författare)
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Small molecule Z363 co-regulates TAF10 and MYC via the E3 ligase TRIP12 to suppress tumour growth
- 2023
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Ingår i: CLINICAL AND TRANSLATIONAL MEDICINE. - : JOHN WILEY & SONS LTD. - 2001-1326. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundThe MYC oncoprotein, also known as the master regulator of genes, is a transcription factor that regulates numerous physiological processes, including cell cycle control, apoptosis, protein synthesis and cell adhesion, among others. MYC is overexpressed in approximately 70% of human cancers. Given its pervasive role in cancer biology, MYC down-regulation has become an attractive cancer treatment strategy. MethodsThe CRISPR/Cas9 method was used to produce KO cell models. Western blot was used to analyzed the expressions of MYC and TATA-binding proteinassociated factors 10 (TAF10) in cancer cells (MCF7, A549, HepG2 cells) Cell culture studies were performed to determine the mechanisms by which small molecules (Z363119456, Z363) affects MYC and TAF10 expressions and functions. Mouse studies were carried out to investigate the impact of Z363 regulation on tumor growth. ResultsZ363 activate Thyroid hormone Receptor-interacting Protein 12 (TRIP12), which phosphorylates MYC at Thr58, resulting in MYC ubiquitination and degradation and thereby regulating MYC target genes. Importantly, TRIP12 also induces TAF10 degradation, which reduces MYC protein levels. TRIP12, an E3 ligase, controls MYC levels both directly and indirectly by inhibiting MYC or TAF10 activity. ConclusionsIn summary,these results demonstrate the anti-cancer properties of Z363, a small molecule that is co-regulated by TAF10 and MYC.
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| 12. |
- Yan, Beibei, et al.
(författare)
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Experimental and modeling study of laminar burning velocity of biomass derived gases/air mixtures
- 2011
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 1879-3487 .- 0360-3199. ; 36:5, s. 3769-3777
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Tidskriftsartikel (refereegranskat)abstract
- Laminar burning velocities of four biomass derived gases have been measured at atmospheric pressure over a range of equivalence ratios and hydrogen contents, using the heat flux method on a perforated flat flame burner. The studied gas mixtures include an air-blown gasification gas from an industrial gasification plant, a model gasification gas studied in the literature, and an upgraded landfill gas (bio-methane). In addition, co-firing of the industrial gasification gas (80% on volume basis) with methane (20% on volume basis) is studied. Model simulations using GRI mechanisms and detailed transport properties are carried out to compare with the measured laminar burning velocities. The results of the bio-methane flame are generally in good agreement with data in the literature and the prediction using GRI-Mech 3.0. The measured laminar burning velocity of the industrial gasification gas is generally higher than the predictions from GRI-Mech 3.0 mechanism but agree rather well with the predictions from GRI-Mech 2.11 for lean and moderate rich mixtures. For rich mixtures, the GRI mechanisms under-predict the laminar burning velocities. For the model gasification gas, the measured laminar burning velocity is higher than the data reported in the literature. The peak burning velocities of the gasification gases/air and the co-firing gases/air mixtures are in richer mixtures than the bio-methane/air mixtures due to the presence of hydrogen and CO in the gasification gases. The GRI mechanisms could well predict the rich shift of the peak burning velocity for the gasification gases but yield large discrepancy for the very rich gasification gas mixtures. The laminar burning velocities for the bio-methane/air mixtures at elevated initial temperatures are measured and compared with the literature data. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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| 13. |
- Yan, Beibei, et al.
(författare)
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Structures and stabilization of low calorific value gas turbulent partially premixed flames in a conical burner
- 2010
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Ingår i: Experimental Thermal and Fluid Science. - : Elsevier BV. - 1879-2286 .- 0894-1777. ; 34:3, s. 412-419
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Konferensbidrag (refereegranskat)abstract
- Experiments are carried out on partially premixed turbulent flames stabilized in a conical burner. The investigated gaseous fuels are methane, methane diluted with nitrogen, and Mixtures of CH4, CO, CO2, H-2 and N-2, Simulating typical products from gasification of biomass, and co-firing of gasification gas with methane. The fuel and air are partially premixed in concentric tubes. Flame stabilization behavior is investigated and significantly different stabilization characteristics are observed in flames with and without the cone. Planar laser induced fluorescence (LIF) imaging of a fuel-tracer species, acetone, and OH radicals is carried out to characterize the flame structures. Large eddy simulations of the conical flames are carried out to gain further understanding of the flame/flow interaction in the cone. The data show that the flames with the cone are more stable than those without the cone. Without the cone (i.e. jet burner) the critical jet velocities for blowoff and liftoff of biomass derived gases are higher than that for methane/nitrogen mixture with the same heating values, indicating the enhanced flame stabilization by hydrogen in the mixture. With the cone the stability of flames is not sensitive to the compositions of the fuels, owing to the different flame stabilization mechanism in the conical flames than that in the jet flames. From the PLIF images it is shown that in the conical burner, the flame is stabilized by the cone at nearly the same position for different fuels. From large eddy simulations, the flames are shown to be controlled by the recirculation flows inside cone, which depends on the cone angle, but less sensitive to the fuel compositions and flow speed. The flames tend to be hold in the recirculation zones even at very high flow speed. Flame blowoff occurs when significant local extinction in the main body of the flame appears at high turbulence intensities. (C) 2009 Elsevier Inc. All rights reserved.
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| 14. |
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| 15. |
- Zhou, Shengquan, et al.
(författare)
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MILD combustion of low calorific value gases
- 2024
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Ingår i: Progress in Energy and Combustion Science. - 0360-1285. ; 104
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Forskningsöversikt (refereegranskat)abstract
- The utilization of low calorific value gases (LCVG) in combustion devices presents particular challenges in terms of ignition and sustained combustion stability due to the presence of non-combustible components. Moderate or intense low-oxygen dilution (MILD) combustion has emerged as a promising technology for LCVG combustion, offering numerous advantages such as high combustion efficiency, reduced pollutant emissions, and increased fuel flexibility. However, the current body of research in this area is fragmented, making it challenging to draw meaningful comparisons between studies and hindering its practical application. This paper provides a comprehensive review of conventional and MILD combustion of LCVG. To understand the impact of composition on combustion, the fuels are classified based on their composition of hydrogen, carbon monoxide, methane, carbon dioxide, nitrogen, and water. We also delve into the chemical and physical effects of composition, including reaction kinetics and turbulence mixing, and provide an overview of the burners and methods used in establishing MILD combustion. Furthermore, computational fluid dynamics (CFD) models and chemical kinetics in MILD combustion are also thoroughly discussed. The presence of a large amount of dilution gas in LCVG increases the self-ignition temperature and ignition delay time of the mixture, making preheating the reactants a critical consideration. In MILD combustion, it is crucial to have an inlet reactant temperature higher than the self-ignition temperature (Tin>Tsi) to mitigate the difficulties associated with ignition and unstable combustion. The heat release in MILD combustion should be moderate to ensure that the combustion temperature does not become too high. The non-combustible components of LCVG are beneficial in this regard, as they allow for a temperature increase of less than the self-ignition temperature (ΔT
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