1
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Zhang J, Feng K, Li Z, Yang B, Yan B, Luo KH. Defect-Driven Efficient Selective CO 2 Hydrogenation with Mo-Based Clusters. JACS Au 2023; 3:2736-2748. [PMID: 37885587 PMCID: PMC10598559 DOI: 10.1021/jacsau.3c00206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 08/25/2023] [Accepted: 08/30/2023] [Indexed: 10/28/2023]
Abstract
Synthetic fuels produced from CO2 show promise in combating climate change. The reverse water gas shift (RWGS) reaction is the key to opening the CO2 molecule, and CO serves as a versatile intermediate for creating various hydrocarbons. Mo-based catalysts are of great interest for RWGS reactions featured for their stability and strong metal-oxygen interactions. Our study identified Mo defects as the intrinsic origin of the high activity of cluster Mo2C for CO2-selective hydrogenation. Specifically, we found that defected Mo2C clusters supported on nitrogen-doped graphene exhibited exceptional catalytic performance, attaining a reaction rate of 6.3 gCO/gcat/h at 400 °C with over 99% CO selectivity and good stability. Such a catalyst outperformed other Mo-based catalysts and noble metal-based catalysts in terms of facile dissociation of CO2, highly selective hydrogenation, and nonbarrier liberation of CO. Our study revealed that as a potential descriptor, the atomic magnetism linearly correlates to the liberation capacity of CO, and Mo defects facilitated product desorption by reducing the magnetization of the adsorption site. On the other hand, the defects were effective in neutralizing the negative charges of surface hydrogen, which is crucial for selective hydrogenation. Finally, we have successfully demonstrated that the combination of a carbon support and the carbonization process synergistically serves as a feasible strategy for creating rich Mo defects, and biochar can be a low-cost alternative option for large-scale applications.
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Affiliation(s)
- Jiajun Zhang
- National
Engineering Research Center of Green Recycling for Strategic Metal
Resources, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
- Center
for Combustion Energy, Key Laboratory for Thermal Science and Power
Engineering of Ministry of Education, International Joint Laboratory
on Low Carbon Clean Energy Innovation, Tsinghua
University, Beijing 100084, China
| | - Kai Feng
- Department
of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Zhengwen Li
- Department
of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Bin Yang
- Center
for Combustion Energy, Key Laboratory for Thermal Science and Power
Engineering of Ministry of Education, International Joint Laboratory
on Low Carbon Clean Energy Innovation, Tsinghua
University, Beijing 100084, China
| | - Binhang Yan
- Department
of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Kai Hong Luo
- Center
for Combustion Energy, Key Laboratory for Thermal Science and Power
Engineering of Ministry of Education, International Joint Laboratory
on Low Carbon Clean Energy Innovation, Tsinghua
University, Beijing 100084, China
- Department
of Mechanical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
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2
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Yang Y, Ronson TK, Hou D, Zheng J, Jahović I, Luo KH, Nitschke JR. Hetero-Diels-Alder Reaction between Singlet Oxygen and Anthracene Drives Integrative Cage Self-Sorting. J Am Chem Soc 2023; 145:19164-19170. [PMID: 37610128 PMCID: PMC10485901 DOI: 10.1021/jacs.3c04228] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Indexed: 08/24/2023]
Abstract
A ZnII8L6 pseudocube containing anthracene-centered ligands, a ZnII4L'4 tetrahedron with a similar side length as the cube, and a trigonal prism ZnII6L3L'2 were formed in equilibrium from a common set of subcomponents. Hetero-Diels-Alder reaction with photogenerated singlet oxygen transformed the anthracene-containing "L" ligands into endoperoxide "LO" ones and ultimately drove the integrative self-sorting to form the trigonal prismatic cage ZnII6LO3L'2 exclusively. This ZnII6LO3L'2 structure lost dioxygen in a retro-Diels-Alder reaction after heating, which resulted in reversion to the initial ZnII8L6 + ZnII4L'4 ⇌ 2 × ZnII6L3L'2 equilibrating system. Whereas the ZnII8L6 pseudocube had a cavity too small for guest encapsulation, the ZnII6L3L'2 and ZnII6LO3L'2 trigonal prisms possessed peanut-shaped internal cavities with two isolated compartments divided by bulky anthracene panels. Guest binding was also observed to drive the equilibrating system toward exclusive formation of the ZnII6L3L'2 structure, even in the absence of reaction with singlet oxygen.
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Affiliation(s)
- Yuchong Yang
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, United
Kingdom
| | - Tanya K. Ronson
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, United
Kingdom
| | - Dingyu Hou
- Department
of Mechanical Engineering, University College
London, London WC1E 7JE, United
Kingdom
| | - Jieyu Zheng
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, United
Kingdom
| | - Ilma Jahović
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, United
Kingdom
| | - Kai Hong Luo
- Department
of Mechanical Engineering, University College
London, London WC1E 7JE, United
Kingdom
| | - Jonathan R. Nitschke
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, United
Kingdom
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3
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Babel S, Bollmers L, Massaro M, Hong Luo K, Stefszky M, Pegoraro F, Held P, Herrmann H, Eigner C, Brecht B, Padberg L, Silberhorn C. Demonstration of Hong-Ou-Mandel interference in an LNOI directional coupler. Opt Express 2023; 31:23140-23148. [PMID: 37475406 DOI: 10.1364/oe.484126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 05/30/2023] [Indexed: 07/22/2023]
Abstract
Interference between single photons is key for many quantum optics experiments and applications in quantum technologies, such as quantum communication or computation. It is advantageous to operate the systems at telecommunication wavelengths and to integrate the setups for these applications in order to improve stability, compactness and scalability. A new promising material platform for integrated quantum optics is lithium niobate on insulator (LNOI). Here, we realise Hong-Ou-Mandel (HOM) interference between telecom photons from an engineered parametric down-conversion source in an LNOI directional coupler. The coupler has been designed and fabricated in house and provides close to perfect balanced beam splitting. We obtain a raw HOM visibility of (93.5 ± 0.7) %, limited mainly by the source performance and in good agreement with off-chip measurements. This lays the foundation for more sophisticated quantum experiments in LNOI.
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4
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Zhu L, Shen D, Zhang H, Luo KH, Li C. Fabrication of Z-scheme Bi 7O 9I 3/g-C 3N 4 heterojunction modified by carbon quantum dots for synchronous photocatalytic removal of Cr (Ⅵ) and organic pollutants. J Hazard Mater 2023; 446:130663. [PMID: 36608584 DOI: 10.1016/j.jhazmat.2022.130663] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 12/11/2022] [Accepted: 12/21/2022] [Indexed: 06/17/2023]
Abstract
Chromium(VI) (Cr(VI)), a highly toxic metal ion, generally co-exists with organic pollutants in industrial effluents. The clean and effective technology for water purification is an imperative issue but still a challenging task. A series of Bi7O9I3/g-C3N4 (BOI/CN) composites modified by lignin-derived carbon quantum dots (CQDs) were fabricated by hydrothermal method and applied for synchronous photocatalytic removal of Cr (Ⅵ) and levofloxacin (LEV). With the modification of CQDs in BOI/CN heterojunction, the 0.5-CQD/BOI/CN photocatalyst (0.5% content of CQDs) exhibited stronger light-harvesting capacity, more efficient charge separation, and faster electron transfer. Compared to those of BOI (51.2%), CN (36.8%), and BOI/CN (74.4%), the photoreduction efficiency of Cr(VI) reached up to 100% by 0.5-CQD/BOI/CN under 60 min of light irradiation, together with 94.8% degradation efficiency of LEV. The degradation of LEV was dominantly controlled by active species (•OH and •O2-) identified by electron paramagnetic resonance analysis and free radical trapping experiments. The intermediates of LEV were determined by LC-MS and the possible degradation pathway was speculated in combination with density functional theory calculation, involving defluorination, decarboxylation, quinolone rings opening, and piperazine moieties oxidation reactions. This work provides an advanced strategy for the fabrication of high-efficiency CQDs-based Z-scheme photocatalysts for environmental remediation.
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Affiliation(s)
- Lingli Zhu
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China
| | - Dekui Shen
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China.
| | - Huiyan Zhang
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China.
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, London WC1E7JE, UK
| | - Chong Li
- School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, PR China
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5
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Abstract
Characterizing the key length and energy scales of intermolecular interactions, Lennard-Jones parameters, i.e., collision diameter and well depth, are prerequisites for predicting transport properties and rate constants of chemical species in dilute gases. Due to anisotropy in molecular structures, Lennard-Jones parameters of many polyatomic molecules are only empirically estimated or even undetermined. This study focuses on determining the effective Lennard-Jones parameters between a polyatomic molecule and a bath gas molecule from interatomic interactions. An iterative search algorithm is developed to find orientation-dependent collision diameters and well depths on intermolecular potential energy surfaces. An orientation-averaging rule based on characteristic variables is proposed to derive the effective parameters. Cross-interaction parameters for twelve hydrocarbons with varying molecular shapes, including long-chain and planar ones, interacting with four bath gases He, Ar, N2, and O2 are predicted and reported. Three-dimensional parametric surfaces are constructed to quantitatively depict molecular anisotropy. Algorithmic complexity analysis and numerical experiments demonstrate that the iterative search algorithm is robust and efficient. By using the latest experimental diffusion data, it is found that the proposed orientation-averaging rule improves the prediction of cross-interaction Lennard-Jones parameters for polyatomic molecules, including for long-chain molecules that challenge the consistency of previous methods. By introducing characteristic variables, the present study shows a new route to determining effective Lennard-Jones parameters for polyatomic molecules.
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Affiliation(s)
- Huangrui Mo
- Center for Combustion Energy, Tsinghua University, Beijing 100084, China. .,Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education, Tsinghua University, Beijing 100084, China.,State Key Laboratory of High Temperature Gas Dynamics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoqing You
- Center for Combustion Energy, Tsinghua University, Beijing 100084, China. .,Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education, Tsinghua University, Beijing 100084, China
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK
| | - Struan H Robertson
- Dassault Systèmes, BIOVIA, 334, Cambridge Science Park, Cambridge CB4 0WN, UK
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6
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Wang Y, Feng K, Tian J, Zhang J, Zhao B, Luo KH, Yan B. Atomically Dispersed Zn-Stabilized Ni δ+ Enabling Tunable Selectivity for CO 2 Hydrogenation. ChemSusChem 2022; 15:e202102439. [PMID: 35132790 DOI: 10.1002/cssc.202102439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 02/04/2022] [Indexed: 06/14/2023]
Abstract
For a heterogeneous catalytic process, the performance of catalysts could be improved by modifying the active metal with a second element. Determining the enhanced mechanism of the second element is essential to the rational design of catalysts. In this work, Zn was introduced as a second element into Ni/ZrO2 for CO2 hydrogenation. In contrast to Ni/ZrO2 , the selectivity of NiZn/ZrO2 is observed to shift from CH4 to CO. A series of structural characterization results reveals that Zn is atomically dispersed in the NiO and ZrO2 phases as NiZnOx and ZnZrOx , respectively during CO2 hydrogenation, stabilizing a higher valence state of Ni (Niδ+ ) under a hydrogenation atmosphere over Ni-O-Zn site and thus promoting the generation of CO. These findings shed light on the O-mediated bimetallic effect of NiZn/ZrO2 and bring new insight into the rational design of more efficient heterogeneous catalysts.
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Affiliation(s)
- Yaning Wang
- Department of Chemical Engineering, Tsinghua University, Beijing, 100084, P. R. China
| | - Kai Feng
- Department of Chemical Engineering, Tsinghua University, Beijing, 100084, P. R. China
| | - Jiaming Tian
- Department of Chemical Engineering, Tsinghua University, Beijing, 100084, P. R. China
| | - Jiajun Zhang
- Department of Energy and Power Engineering, Tsinghua University, Beijing, 100084, P. R. China
| | - Baohuai Zhao
- Institute of Engineering Technology, SINOPEC Catalyst Co., Ltd, Beijing, 101111, P. R. China
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, United Kingdom
| | - Binhang Yan
- Department of Chemical Engineering, Tsinghua University, Beijing, 100084, P. R. China
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7
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Affiliation(s)
- Kai Feng
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Jiaming Tian
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Jiajun Zhang
- Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, and International Joint Laboratory on Low Carbon Clean Energy Innovation, Tsinghua University, Beijing 100084, China
| | - Zhengwen Li
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Yuxin Chen
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, U.K
| | - Bin Yang
- Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, and International Joint Laboratory on Low Carbon Clean Energy Innovation, Tsinghua University, Beijing 100084, China
| | - Binhang Yan
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
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8
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Zhu L, Shen D, Hong Luo K. Triple-emission nitrogen and boron co-doped carbon quantum dots from lignin: Highly fluorescent sensing platform for detection of hexavalent chromium ions. J Colloid Interface Sci 2022; 617:557-567. [PMID: 35303639 DOI: 10.1016/j.jcis.2022.03.039] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 03/08/2022] [Accepted: 03/09/2022] [Indexed: 12/24/2022]
Abstract
Considering that hexavalent chromium ions (Cr6+) with high toxicity poses a huge threat to human health and the ecological environment, constructing a rapid and accurate sensing platform is of great significance in detecting the toxic substance. The novel nitrogen and boron co-doped carbon quantum dots (N, B-CQDs) from lignin are synthesized as fluorescent sensors for the detection of Cr6+. The synthetic processes involve the acid hydrolysis step followed by the hydrothermal treatment step. Lignin is firstly depolymerized by cleaving ether bonds in the acidolysis, and N, B-CQDs are consequently formed by the aromatic re-fusion of lignin nanoparticles in the hydrothermal process. The lignin-derived N, B-CQDs show triple emission of purple, blue and green fluorescence under the excitation of 300, 330, and 490 nm, respectively. The triple-emission N, B-CQDs are applied for the triple-channel detection of Cr6+, which exhibit highly sensitive and selective fluorescence quenching for Cr6+ with good linearity (R2 ≤ 0.996) and very low limit of detection as 0.054, 0.049, and 0.077 μM under the excitation of 300, 330 and 490 nm, respectively. The utilization of renewable lignin as CQDs-based fluorescent sensors opens a new avenue for the rapid and accurate detection of Cr6+ through a multichannel sensing platform.
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Affiliation(s)
- Lingli Zhu
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China
| | - Dekui Shen
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China.
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, London WC1E7JE, UK
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9
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Zhu L, Shen D, Wang Q, Luo KH. Green Synthesis of Tunable Fluorescent Carbon Quantum Dots from Lignin and Their Application in Anti-Counterfeit Printing. ACS Appl Mater Interfaces 2021; 13:56465-56475. [PMID: 34784479 DOI: 10.1021/acsami.1c16679] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Lignin converted to carbon quantum dots (CQDs) attracts tremendous attention for large-scale production of carbon nanomaterials and value-added disposal of biomass wastes (such as the black liquor from pulping industry and the residue from hydrolysis of biomass). The green synthesis of lignin-derived CQDs is reported via a facile two-step method with the adjustment of acid additives containing N or S. The resulting series of CQDs exhibit bright fluorescence in gradient colors from blue to yellowish green, among which the N, S co-doped CQDs with the addition of 2,4-diaminobenzene sulfonic acid show an optimal fluorescence quantum yield (QY) of 30.5%. The red-shift photoluminescence emission behaviors of these CQDs can be attributed to the increased graphitization degree and reduced optical energy band gaps (2.47 → 2.17 eV) with regard to the incorporation of various heteroatoms. The improved fluorescence QYs are consistent with the variation trend of the increased N/C content in the CQDs. The yellowish green-emissive CQDs with bright fluorescence, strong water solubility, and excellent chemical stability perform well in anti-counterfeiting printing. The promising and sustainable approach for the synthesis of tunable fluorescent CQDs exhibits the value-added utilization of lignin for the fluorescence ink production.
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Affiliation(s)
- Lingli Zhu
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, P. R. China
| | - Dekui Shen
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, P. R. China
| | - Qi Wang
- College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310087, Zhejiang, P. R. China
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, London WC1E 7JE, U.K
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10
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Zhang J, Zhang X, Osatiashtiani A, Luo KH, Shen D, Li J, Bridgwater A. The mechanism of hydrogen donation by bio-acids over metal supported on nitrogen-doped carbon nanotubes. Molecular Catalysis 2021. [DOI: 10.1016/j.mcat.2020.111289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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11
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Zhu L, Shen D, Luo KH. A critical review on VOCs adsorption by different porous materials: Species, mechanisms and modification methods. J Hazard Mater 2020; 389:122102. [PMID: 32058893 DOI: 10.1016/j.jhazmat.2020.122102] [Citation(s) in RCA: 232] [Impact Index Per Article: 58.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 01/09/2020] [Accepted: 01/13/2020] [Indexed: 05/23/2023]
Abstract
Volatile organic compounds (VOCs) have attracted world-wide attention regarding their serious hazards on ecological environment and human health. Industrial processes such as fossil fuel combustion, petrochemicals, painting, coatings, pesticides, plastics, contributed to the large proportion of anthropogenic VOCs emission. Destructive methods (catalysis oxidation and biofiltration) and recovery methods (absorption, adsorption, condensation and membrane separation) have been developed for VOCs removal. Adsorption is established as one of the most promising strategies for VOCs abatement thanks to its characteristics of cost-effectiveness, simplicity and low energy consumption. The prominent progress in VOCs adsorption by different kinds of porous materials (such as carbon-based materials, oxygen-contained materials, organic polymers and composites is carefully summarized in this work, concerning the mechanism of adsorbate-adsorbent interactions, modification methods for the mentioned porous materials, and enhancement of VOCs adsorption capacity. This overview is to provide a comprehensive understanding of VOCs adsorption mechanisms and up-to-date progress of modification technologies for different porous materials.
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Affiliation(s)
- Lingli Zhu
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, Southeast University, Nanjing 210096, PR China
| | - Dekui Shen
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, Southeast University, Nanjing 210096, PR China.
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, London WC1E7JE, UK
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12
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Deng K, Zhong Y, Wang M, Zhong Y, Luo KH. Effects of Acoustic Excitation on the Combustion Instability of Hydrogen-Methane Lean Premixed Swirling Flames. ACS Omega 2020; 5:8744-8753. [PMID: 32337436 PMCID: PMC7178801 DOI: 10.1021/acsomega.0c00287] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 03/27/2020] [Indexed: 06/01/2023]
Abstract
Lean premixed flames are useful for low nitrogen oxide (NO x ) emissions but more prone to induce combustion instability in gas turbines. Combustion instability of a lean premixed swirling flame (LPSF) with hydrogen-methane was investigated experimentally. The effects of hydrogen addition on combustion instability with equivalence ratios 0.75-1 were investigated with acoustic frequencies (90-240 Hz) and acoustic amplitudes (the ratio of velocity fluctuation to an average velocity of 0-0.5), respectively, which are characterized by the gain and phase of the flame describing function (FDF). The evolution of vortex and the flame morphologies were observed by the particle image velocimetry (PIV), intensified charge-coupled device (ICCD), photomultiplier tube (PMT), and Cassegrain optical systems. The global and local heat release fluctuations of the LPSF were shown by CH*/OH* chemiluminescence and temperature measurements. Results show that the FDF features maximum and minimum gain values in the acoustic frequency range of 90-240 Hz and reaches local maximum peaks at 110 and 180 Hz and local minimum peaks at 160 Hz. It can also be observed that varying velocity amplitudes (0-0.5) have greater effects on the gain and phase of FDF than changing equivalence ratios (0.75-1) for lean swirling flames. Higher velocity amplitudes more effectively intensified the compression of the flame length, which enhanced the mixing of the high-burning gas and the unburned gas, and then heat release fluctuations increased. However, it is more interesting that the effects of hydrogen addition on the combustion instability of the LPSF show a completely opposite phenomenon due to acoustic frequency under all experimental conditions. The FDFs were compared at typical frequencies of 140 and 180 Hz, and it was found that combustion instability enhanced with increasing hydrogen content at 140 Hz while weakened at 180 Hz. The flow field of PIV images shows that it is related to the location and development of vortices in the flame with varying acoustic frequencies. The intensity of OH*/CH* chemiluminescence, local temperature, and heat release rate show the same changing trend with the flame morphology for two acoustic parameters with the increasing hydrogen content in the LPSF. This directly affects the compression and curvature of the LPSF and thereby changes the mixture and temperature of the combustible gas, which influence the heat release fluctuation of the LPSF.
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Affiliation(s)
- Kai Deng
- Institute
of Energy and Power Engineering, Zhejiang
University of Technology, Hangzhou 310014, China
- Department
of Mechanical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
| | - Yi Zhong
- Institute
of Energy and Power Engineering, Zhejiang
University of Technology, Hangzhou 310014, China
| | - Mingxiao Wang
- Zhejiang
Important Laboratory of Energy Storage and Building Energy Saving
Technology, Huadian Electric Power Research
Institute Co., Ltd., Hangzhou 310000, China
| | - Yingjie Zhong
- Institute
of Energy and Power Engineering, Zhejiang
University of Technology, Hangzhou 310014, China
| | - Kai Hong Luo
- Department
of Mechanical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
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13
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Xie Z, Luo KH, Chang KC, Panoiu NC, Herrmann H, Silberhorn C, Wong CW. Efficient C-band single-photon upconversion with chip-scale Ti-indiffused pp-LiNbO 3 waveguides. Appl Opt 2019; 58:5910-5915. [PMID: 31503905 DOI: 10.1364/ao.58.005910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 06/27/2019] [Indexed: 06/10/2023]
Abstract
Frequency upconversion for single photons at telecom wavelengths is important to simultaneously meet the different wavelength requirements for long-distance communications and quantum memories in a quantum nodal network. It also enables the detection for the telecom "flying qubit" photons with silicon-based efficient single-photon detectors with low dark count (DC) rates. Here, we demonstrate the frequency upconversion of attenuated single photons, using a low-loss titanium-indiffused periodically poled lithium niobate waveguide, pumped with a readily available erbium-doped fiber amplifier in the L-band. Internal and conversion efficiencies up to 84.4% and 49.9% have been achieved, respectively. The DC rates are suppressed down to 44 kHz at 13.9% end-to-end quantum efficiency (including full conversion and detection), enabled by our long-wavelength pump configuration and narrow 3.5-GHz bandpass filtering.
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14
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Wang H, Wen K, You X, Mao Q, Luo KH, Pilling MJ, Robertson SH. Energy transfer in intermolecular collisions of polycyclic aromatic hydrocarbons with bath gases He and Ar. J Chem Phys 2019; 151:044301. [PMID: 31370521 DOI: 10.1063/1.5094104] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Classical trajectory simulations of intermolecular collisions were performed for a series of polycyclic aromatic hydrocarbons interacting with the bath gases helium and argon for bath gas temperature from 300 to 2500 K. The phase-space average energy transferred per deactivating collision, ⟨∆Edown⟩, was obtained. The Buckingham pairwise intermolecular potentials were validated against high-level quantum chemistry calculations and used in the simulations. The reactive force-field was used to describe intramolecular potentials. The dependence of ⟨∆Edown⟩ on initial vibrational energy is discussed. A canonical sampling method was compared with a microcanonical sampling method for selecting initial vibrational energy at high bath gas temperatures. Uncertainties introduced by the initial angular momentum distribution were identified. The dependence of the collisional energy transfer parameters on the type of bath gas and the molecular structure of polycyclic aromatic hydrocarbons was examined.
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Affiliation(s)
- Hongmiao Wang
- Center for Combustion Energy, Tsinghua University, Beijing 100084, China
| | - Kaicheng Wen
- Center for Combustion Energy, Tsinghua University, Beijing 100084, China
| | - Xiaoqing You
- Center for Combustion Energy, Tsinghua University, Beijing 100084, China
| | - Qian Mao
- Center for Combustion Energy, Tsinghua University, Beijing 100084, China
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Michael J Pilling
- School of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Struan H Robertson
- Dassault Systèmes, BIOVIA, 334, Cambridge Science Park, Cambridge CB4 0WN, United Kingdom
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15
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Zhu Y, Gao L, Luo KH, Pan J, Pan Z, Zhang P. Flame evolution in shock-accelerated flow under different reactive gas mixture gradients. Phys Rev E 2019; 100:013111. [PMID: 31499804 DOI: 10.1103/physreve.100.013111] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Indexed: 11/07/2022]
Abstract
The interaction between a planar shock wave and a spherical flame is studied numerically for an ethylene-oxygen-nitrogen gas mixture. Influences of different initial reactive gas mixture gradients on the shock-flame interaction are investigated by using high-resolution computational simulations. The results show that the different reactive gas mixture gradients can greatly affect the flame evolution in shock accelerated flow. A detonation only emerges in the homogenous reactive gas mixture case, but a distinct shock bifurcation can be found in the inhomogeneous cases where the leftward reflected shock wave propagates in a reverse flow with a high transverse velocity gradient in the inhomogeneous cases. Also, the flame volume and heat release rate increase when the distribution of the reactive gas mixture is uniform or with a positive gradient in this paper, but decrease when the distribution of the reactive gas mixture is with a negative gradient, however, the ratio of unburned to burned regions in the flame zone shows just the opposite trends. Furthermore, the factors affecting the vorticity generation are also analyzed. It is found that the compression term has a relatively stronger influence on the vorticity generation in all the three cases except the period before the reflected shock wave impinges on the distorted flame in the homogeneous case, wherein the baroclinic effect dominates the vorticity generation in the flame zone.
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Affiliation(s)
- Yuejin Zhu
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China.,Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Longkun Gao
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Jianfeng Pan
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Zhenhua Pan
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Penggang Zhang
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
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16
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Shabnam S, Mao Q, van Duin ACT, Luo KH. Evaluation of the effect of nickel clusters on the formation of incipient soot particles from polycyclic aromatic hydrocarbons via ReaxFF molecular dynamics simulations. Phys Chem Chem Phys 2019; 21:9865-9875. [PMID: 31033994 DOI: 10.1039/c9cp00354a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the present study, the ReaxFF reactive molecular dynamics simulation method was applied to investigate the effect of a small nickel cluster (Ni13) on the formation of nascent soot from polycyclic aromatic hydrocarbon (PAH) precursors. A series of NVT simulations was performed for systems of a Ni13 cluster and various PAH monomers, namely, naphthalene, anthracene, pyrene, coronene, ovalene, and circumcoronene, at temperatures from 400 to 2500 K. At low temperatures, the PAHs form soot particles via binding and stacking around nickel clusters. Larger soot particles are formed due to the early initiation of clustering provided by nickel compared to those observed in homogenous PAH systems. At 1200-1600 K, the PAH monomers show a chemisorption tendency onto the nickel surface, which results in incipient soot particles. Chemical nucleation was observed at 2000 K where nickel-assisted dehydrogenation and chemisorption of PAH led to the growth of stable soot particles, which did not occur in the absence of Ni-clusters. At a high temperature (2500 K), nickel significantly accelerates the ring-opening and graphitization of PAH molecules and increases the size of the fullerene-type soot as compared to that of homogenous systems.
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Affiliation(s)
- Sharmin Shabnam
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
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17
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Jiang XZ, Gong H, Luo KH, Ventikos Y. Large-scale molecular dynamics simulation of coupled dynamics of flow and glycocalyx: towards understanding atomic events on an endothelial cell surface. J R Soc Interface 2018; 14:rsif.2017.0780. [PMID: 29212760 PMCID: PMC5746579 DOI: 10.1098/rsif.2017.0780] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 11/10/2017] [Indexed: 12/11/2022] Open
Abstract
The glycocalyx has a prominent role in orchestrating multiple biological processes occurring at the plasma membrane. In this paper, an all-atom flow/glycocalyx system is constructed with the bulk flow velocity in the physiologically relevant ranges for the first time. The system is simulated by molecular dynamics using 5.8 million atoms. Flow dynamics and statistics in the presence of the glycocalyx are presented and discussed. Complex dynamic behaviours of the glycocalyx, particularly the sugar chains, are observed in response to blood flow. In turn, the motion of the glycocalyx, including swing and swirling, disturbs the flow by altering the velocity profiles and modifying the vorticity distributions. As a result, the initially one-dimensional forcing is spread to all directions in the region near the endothelial cell surface. Furthermore, the coupled dynamics exist not only between the flow and the glycocalyx but also within the glycocalyx molecular constituents. Shear stress distributions between one-dimer and three-dimer cases are also conducted. Finally, potential force transmission pathways are discussed based on the dynamics of the glycocalyx constituents, which provides new insight into the mechanism of mechanotransduction of the glycocalyx. These findings have relevance in the pathologies of glycocalyx-related diseases, for example in renal or cardiovascular conditions.
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Affiliation(s)
- Xi Zhuo Jiang
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK
| | - Haipeng Gong
- MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, People's Republic of China
| | - Kai Hong Luo
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK
| | - Yiannis Ventikos
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK
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18
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Abstract
Catalytic hydrogenolysis of lignin is overviewed, concerning the cleavage of typical inter-unit linkages and the production of aromatic chemicals.
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Affiliation(s)
- Chongbo Cheng
- Key lab of Thermal Energy Conversion and Control of MoE
- Southeast University
- Nanjing 210096
- China
| | - Dekui Shen
- Key lab of Thermal Energy Conversion and Control of MoE
- Southeast University
- Nanjing 210096
- China
| | - Sai Gu
- Department of Chemical and Process Engineering
- Faculty of Engineering and Physical Sciences
- University of Surrey
- UK
| | - Kai Hong Luo
- Department of Mechanical Engineering
- University College London
- London WC1E 7JE
- UK
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19
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Mao Q, Ren Y, Luo KH, van Duin ACT. Dynamics and kinetics of reversible homo-molecular dimerization of polycyclic aromatic hydrocarbons. J Chem Phys 2017; 147:244305. [PMID: 29289134 DOI: 10.1063/1.5000534] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Physical dimerization of polycyclic aromatic hydrocarbons (PAHs) has been investigated via molecular dynamics (MD) simulation with the ReaxFF reactive force field that is developed to bridge the gap between the quantum mechanism and classical MD. Dynamics and kinetics of homo-molecular PAH collision under different temperatures, impact parameters, and orientations are studied at an atomic level, which is of great value to understand and model the PAH dimerization. In the collision process, the enhancement factors of homo-molecular dimerizations are quantified and found to be larger at lower temperatures or with smaller PAH instead of size independent. Within the capture radius, the lifetime of the formed PAH dimer decreases as the impact parameter increases. Temperature and PAH characteristic dependent forward and reverse rate constants of homo-molecular PAH dimerization are derived from MD simulations, on the basis of which a reversible model is developed. This model can predict the tendency of PAH dimerization as validated by pyrene dimerization experiments [H. Sabbah et al., J. Phys. Chem. Lett. 1(19), 2962 (2010)]. Results from this study indicate that the physical dimerization cannot be an important source under the typical flame temperatures and PAH concentrations, which implies a more significant role played by the chemical route.
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Affiliation(s)
- Qian Mao
- Center for Combustion Energy, Tsinghua University, Beijing 100084, China
| | - Yihua Ren
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - K H Luo
- Center for Combustion Energy, Tsinghua University, Beijing 100084, China
| | - Adri C T van Duin
- Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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20
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Lin C, Xu A, Zhang G, Luo KH, Li Y. Discrete Boltzmann modeling of Rayleigh-Taylor instability in two-component compressible flows. Phys Rev E 2017; 96:053305. [PMID: 29347713 DOI: 10.1103/physreve.96.053305] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Indexed: 11/06/2022]
Abstract
A discrete Boltzmann model (DBM) is proposed to probe the Rayleigh-Taylor instability (RTI) in two-component compressible flows. Each species has a flexible specific-heat ratio and is described by one discrete Boltzmann equation (DBE). Independent discrete velocities are adopted for the two DBEs. The collision and force terms in the DBE account for the molecular collision and external force, respectively. Two types of force terms are exploited. In addition to recovering the modified Navier-Stokes equations in the hydrodynamic limit, the DBM has the capability of capturing detailed nonequilibrium effects. Furthermore, we use the DBM to investigate the dynamic process of the RTI. The invariants of tensors for nonequilibrium effects are presented and studied. For low Reynolds numbers, both global nonequilibrium manifestations and the growth rate of the entropy of mixing show three stages (i.e., the reducing, increasing, and then decreasing trends) in the evolution of the RTI. On the other hand, the early reducing tendency is suppressed and even eliminated for high Reynolds numbers. Relevant physical mechanisms are analyzed and discussed.
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Affiliation(s)
- Chuandong Lin
- Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China.,State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083, China.,College of Mathematics and Informatics & FJKLMAA, Fujian Normal University, Fuzhou 350007, China
| | - Aiguo Xu
- Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, P. O. Box 8009-26, Beijing 100088, China.,Center for Applied Physics and Technology, MOE Key Center for High Energy Density Physics Simulations, College of Engineering, Peking University, Beijing 100871, China
| | - Guangcai Zhang
- Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, P. O. Box 8009-26, Beijing 100088, China
| | - Kai Hong Luo
- Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China.,Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Yingjun Li
- State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083, China
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21
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Abstract
We propose a multi-component discrete Boltzmann model (DBM) for premixed, nonpremixed, or partially premixed nonequilibrium reactive flows. This model is suitable for both subsonic and supersonic flows with or without chemical reaction and/or external force. A two-dimensional sixteen-velocity model is constructed for the DBM. In the hydrodynamic limit, the DBM recovers the modified Navier-Stokes equations for reacting species in a force field. Compared to standard lattice Boltzmann models, the DBM presents not only more accurate hydrodynamic quantities, but also detailed nonequilibrium effects that are essential yet long-neglected by traditional fluid dynamics. Apart from nonequilibrium terms (viscous stress and heat flux) in conventional models, specific hydrodynamic and thermodynamic nonequilibrium quantities (high order kinetic moments and their departure from equilibrium) are dynamically obtained from the DBM in a straightforward way. Due to its generality, the developed methodology is applicable to a wide range of phenomena across many energy technologies, emissions reduction, environmental protection, mining accident prevention, chemical and process industry.
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Affiliation(s)
- Chuandong Lin
- Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing, 100084, China.
| | - Kai Hong Luo
- Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing, 100084, China. .,Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK.
| | - Linlin Fei
- Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing, 100084, China
| | - Sauro Succi
- Istituto Applicazioni Calcolo, CNR, Via dei Taurini 19, 00185, Rome, Italy
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22
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Abstract
In this paper, we give an alternative derivation for the cascaded lattice Boltzmann method (CLBM) within a general multiple-relaxation-time (MRT) framework by introducing a shift matrix. When the shift matrix is a unit matrix, the CLBM degrades into an MRT LBM. Based on this, a consistent forcing scheme is developed for the CLBM. The consistency of the nonslip rule, the second-order convergence rate in space, and the property of isotropy for the consistent forcing scheme is demonstrated through numerical simulations of several canonical problems. Several existing forcing schemes previously used in the CLBM are also examined. The study clarifies the relation between MRT LBM and CLBM under a general framework.
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Affiliation(s)
- Linlin Fei
- Center for Combustion Energy, Key laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China
| | - Kai Hong Luo
- Center for Combustion Energy, Key laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK
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23
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Li Q, Luo KH, Kang QJ, Chen Q. Contact angles in the pseudopotential lattice Boltzmann modeling of wetting. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 90:053301. [PMID: 25493898 DOI: 10.1103/physreve.90.053301] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Indexed: 06/04/2023]
Abstract
In this paper we investigate the implementation of contact angles in the pseudopotential lattice Boltzmann modeling of wetting at a large density ratio ρ_{L}/ρ_{V}=500. The pseudopotential lattice Boltzmann model [X. Shan and H. Chen, Phys. Rev. E 49, 2941 (1994)10.1103/PhysRevE.49.2941] is a popular mesoscopic model for simulating multiphase flows and interfacial dynamics. In this model the contact angle is usually realized by a fluid-solid interaction. Two widely used fluid-solid interactions, the density-based interaction and the pseudopotential-based interaction, as well as a modified pseudopotential-based interaction formulated in the present paper are numerically investigated and compared in terms of the achievable contact angles, the maximum and the minimum densities, and the spurious currents. It is found that the pseudopotential-based interaction works well for simulating small static (liquid) contact angles θ<90^{∘}, however, it is unable to reproduce static contact angles close to 180^{∘}. Meanwhile, it is found that the proposed modified pseudopotential-based interaction performs better in light of the maximum and the minimum densities and is overall more suitable for simulating large contact angles θ>90^{∘} as compared with the two other types of fluid-solid interactions. Furthermore, the spurious currents are found to be enlarged when the fluid-solid interaction force is introduced. Increasing the kinematic viscosity ratio between the vapor and liquid phases is shown to be capable of reducing the spurious currents caused by the fluid-solid interactions.
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Affiliation(s)
- Qing Li
- School of Energy Science and Engineering, Central South University, Changsha 410083, China and Computational Earth Science Group, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - K H Luo
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Q J Kang
- Computational Earth Science Group, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Q Chen
- School of Energy and Power Engineering, Nanjing University of Science and Technology, Jiangsu 210094, China
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24
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Li Q, Luo KH. Effect of the forcing term in the pseudopotential lattice Boltzmann modeling of thermal flows. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 89:053022. [PMID: 25353895 DOI: 10.1103/physreve.89.053022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Indexed: 06/04/2023]
Abstract
The pseudopotential lattice Boltzmann (LB) model is a popular model in the LB community for simulating multiphase flows. Recently, several thermal LB models, which are based on the pseudopotential LB model and constructed within the framework of the double-distribution-function LB method, were proposed to simulate thermal multiphase flows [G. Házi and A. Márkus, Phys. Rev. E 77, 026305 (2008); L. Biferale, P. Perlekar, M. Sbragaglia, and F. Toschi, Phys. Rev. Lett. 108, 104502 (2012); S. Gong and P. Cheng, Int. J. Heat Mass Transfer 55, 4923 (2012); M. R. Kamali et al., Phys. Rev. E 88, 033302 (2013)]. The objective of the present paper is to show that the effect of the forcing term on the temperature equation must be eliminated in the pseudopotential LB modeling of thermal flows. First, the effect of the forcing term on the temperature equation is shown via the Chapman-Enskog analysis. For comparison, alternative treatments that are free from the forcing-term effect are provided. Subsequently, numerical investigations are performed for two benchmark tests. The numerical results clearly show that the existence of the forcing-term effect will lead to significant numerical errors in the pseudopotential LB modeling of thermal flows.
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Affiliation(s)
- Qing Li
- Energy Technology Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, United Kingdom
| | - K H Luo
- Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
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25
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Li Q, Luo KH. Achieving tunable surface tension in the pseudopotential lattice Boltzmann modeling of multiphase flows. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 88:053307. [PMID: 24329379 DOI: 10.1103/physreve.88.053307] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Indexed: 06/03/2023]
Abstract
In this paper, we aim to address an important issue about the pseudopotential lattice Boltzmann (LB) model, which has attracted much attention as a mesoscopic model for simulating interfacial dynamics of complex fluids, but suffers from the problem that the surface tension cannot be tuned independently of the density ratio. In the literature, a multirange potential was devised to adjust the surface tension [Sbragaglia et al., Phys. Rev. E 75, 026702 (2007)]. However, it was recently found that the density ratio of the system will be changed when the multirange potential is employed to adjust the surface tension. An alternative approach is therefore proposed in the present work. The basic strategy is to add a source term to the LB equation so as to tune the surface tension of the pseudopotential LB model. The proposed approach can guarantee that the adjustment of the surface tension does not affect the mechanical stability condition of the pseudopotential LB model, and thus provides a separate control of the surface tension and the density ratio. Meanwhile, it still retains the mesoscopic feature and the computational simplicity of the pseudopotential LB model. Numerical simulations are carried out for stationary droplets, capillary waves, and droplet splashing on a thin liquid film. The numerical results demonstrate that the proposed approach is capable of achieving a tunable surface tension over a very wide range and can keep the density ratio unchanged when adjusting the surface tension.
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Affiliation(s)
- Qing Li
- Energy Technology Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, United Kingdom
| | - K H Luo
- Energy Technology Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, United Kingdom and Department of Mechanical Engineering, University College London, University of London, Torrington Place, London WC1E 7JE, United Kingdom
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26
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Li Q, Luo KH, Li XJ. Lattice Boltzmann modeling of multiphase flows at large density ratio with an improved pseudopotential model. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 87:053301. [PMID: 23767651 DOI: 10.1103/physreve.87.053301] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 01/07/2013] [Indexed: 06/02/2023]
Abstract
Owing to its conceptual simplicity and computational efficiency, the pseudopotential multiphase lattice Boltzmann (LB) model has attracted significant attention since its emergence. In this work, we aim to extend the pseudopotential LB model to simulate multiphase flows at large density ratio and relatively high Reynolds number. First, based on our recent work [Q. Li, K. H. Luo, and X. J. Li, Phys. Rev. E 86, 016709 (2012)], an improved forcing scheme is proposed for the multiple-relaxation-time pseudopotential LB model in order to achieve thermodynamic consistency and large density ratio in the model. Next, through investigating the effects of the parameter a in the Carnahan-Starling equation of state, we find that the interface thickness is approximately proportional to 1/√a. Using a smaller a will lead to a wider interface thickness, which can reduce the spurious currents and enhance the numerical stability of the pseudopotential model at large density ratio. Furthermore, it is found that a lower liquid viscosity can be gained in the pseudopotential model by increasing the kinematic viscosity ratio between the vapor and liquid phases. The improved pseudopotential LB model is numerically validated via the simulations of stationary droplet and droplet oscillation. Using the improved model as well as the above treatments, numerical simulations of droplet splashing on a thin liquid film are conducted at a density ratio in excess of 500 with Reynolds numbers ranging from 40 to 1000. The dynamics of droplet splashing is correctly reproduced and the predicted spread radius is found to obey the power law reported in the literature.
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Affiliation(s)
- Q Li
- Energy Technology Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, United Kingdom
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27
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Li Q, Luo KH, Li XJ. Forcing scheme in pseudopotential lattice Boltzmann model for multiphase flows. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 86:016709. [PMID: 23005565 DOI: 10.1103/physreve.86.016709] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Revised: 06/26/2012] [Indexed: 06/01/2023]
Abstract
The pseudopotential lattice Boltzmann (LB) model is a widely used multiphase model in the LB community. In this model, an interaction force, which is usually implemented via a forcing scheme, is employed to mimic the molecular interactions that cause phase segregation. The forcing scheme is therefore expected to play an important role in the pseudoepotential LB model. In this paper, we aim to address some key issues about forcing schemes in the pseudopotential LB model. First, theoretical and numerical analyses will be made for Shan-Chen's forcing scheme [Shan and Chen, Phys. Rev. E 47, 1815 (1993)] and the exact-difference-method forcing scheme [Kupershtokh et al., Comput. Math. Appl. 58, 965 (2009)]. The nature of these two schemes and their recovered macroscopic equations will be shown. Second, through a theoretical analysis, we will reveal the physics behind the phenomenon that different forcing schemes exhibit different performances in the pseudopotential LB model. Moreover, based on the analysis, we will present an improved forcing scheme and numerically demonstrate that the improved scheme can be treated as an alternative approach to achieving thermodynamic consistency in the pseudopotential LB model.
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Affiliation(s)
- Q Li
- Energy Technology Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, United Kingdom
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28
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Li Q, Luo KH, Gao YJ, He YL. Additional interfacial force in lattice Boltzmann models for incompressible multiphase flows. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 85:026704. [PMID: 22463354 DOI: 10.1103/physreve.85.026704] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 01/15/2012] [Indexed: 05/31/2023]
Abstract
The existing lattice Boltzmann models for incompressible multiphase flows are mostly constructed with two distribution functions: one is the order parameter distribution function, which is used to track the interface between different phases, and the other is the pressure distribution function for solving the velocity field. In this paper, it is shown that in these models the recovered momentum equation is inconsistent with the target one: an additional force is included in the recovered momentum equation. The additional force has the following features. First, it is proportional to the macroscopic velocity. Second, it is zero in every single-phase region but is nonzero in the interface. Therefore it can be interpreted as an interfacial force. To investigate the effects of the additional interfacial force, numerical simulations are carried out for the problem of Rayleigh-Taylor instability, droplet splashing on a thin liquid film, and the evolution of a falling droplet under gravity. Numerical results demonstrate that, with the increase of the velocity or the Reynolds number, the additional interfacial force will gradually have an important influence on the interface and affect the numerical accuracy.
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Affiliation(s)
- Q Li
- Energy Technology Research Group, School of Engineering Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
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29
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Li Q, Luo KH, He YL, Gao YJ, Tao WQ. Coupling lattice Boltzmann model for simulation of thermal flows on standard lattices. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 85:016710. [PMID: 22400704 DOI: 10.1103/physreve.85.016710] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2011] [Revised: 11/14/2011] [Indexed: 05/31/2023]
Abstract
In this paper, a coupling lattice Boltzmann (LB) model for simulating thermal flows on the standard two-dimensional nine-velocity (D2Q9) lattice is developed in the framework of the double-distribution-function (DDF) approach in which the viscous heat dissipation and compression work are considered. In the model, a density distribution function is used to simulate the flow field, while a total energy distribution function is employed to simulate the temperature field. The discrete equilibrium density and total energy distribution functions are obtained from the Hermite expansions of the corresponding continuous equilibrium distribution functions. The pressure given by the equation of state of perfect gases is recovered in the macroscopic momentum and energy equations. The coupling between the momentum and energy transports makes the model applicable for general thermal flows such as non-Boussinesq flows, while the existing DDF LB models on standard lattices are usually limited to Boussinesq flows in which the temperature variation is small. Meanwhile, the simple structure and general features of the DDF LB approach are retained. The model is tested by numerical simulations of thermal Couette flow, attenuation-driven acoustic streaming, and natural convection in a square cavity with small and large temperature differences. The numerical results are found to be in good agreement with the analytical solutions and/or other numerical results reported in the literature.
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Affiliation(s)
- Q Li
- Key Laboratory of Thermal Fluid Science and Engineering of MOE, National Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
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30
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Shen DK, Gu S, Luo KH, Wang SR, Fang MX. The pyrolytic degradation of wood-derived lignin from pulping process. Bioresour Technol 2010; 101:6136-46. [PMID: 20307972 DOI: 10.1016/j.biortech.2010.02.078] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2009] [Revised: 02/17/2010] [Accepted: 02/21/2010] [Indexed: 05/08/2023]
Abstract
Lignin is a key component in the biomass with a complex polymeric structure of the phenyl-C(3) alkyl units. The kraft lignin from the wood pulping process is tested in TG-FTIR and Py-GC-MS. The samples are pyrolyzed in TGA coupled with FTIR from 30 to 900 degrees C at the heating rate of 20 and 40K/min. The evolution of phenolic compounds in the initial pyrolysis stage of lignin is determined by FTIR, while the second stage is mainly attributed to the production of the low molecular weight species. A bench-scale fast pyrolysis unit is employed to investigate the effect of temperature on the product yield and composition. It is found that the guaiacol-type and syringol-type compounds as the primary products of lignin pyrolysis are predominant in bio-oil, acting as the significant precursors for the formation of the derivatives such as the phenol-, cresol- and catechol-types. A series of free-radical chain-reactions, concerning the cracking of different side-chain structures and the methoxy groups on aromatic ring, are proposed to demonstrate the formation pathways for the typical compounds in bio-oil by closely relating lignin structure to the pyrolytic mechanisms. The methoxy group (-OCH(3)) is suggested to work as an important source for the formation of the small volatile species (CO, CO(2) and CH(4)) through the relevant free radical coupling reactions.
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Affiliation(s)
- D K Shen
- Energy Technology Research Group, School of Engineering Science, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
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Wang SY, He FZ, Luo KH. [Study of the effect of the Rapid-Effect Air Disinfectant tablet in the sterilization of hospital air]. Zhonghua Hu Li Za Zhi 1997; 32:37-8. [PMID: 9304962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Luo KH, Shi YK, Sun Y, Wang QL, Wu GQ, Feng FY, Cui W, Liu HB. A practical procedure for the cryopreservation of marrow cells intended for autotransplantation. Leuk Lymphoma 1995; 17:495-9. [PMID: 7549843 DOI: 10.3109/10428199509056863] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A simple and practical method of unfractionated bone marrow processing and cryopreservation was studied. The date shows that RBCs can be rapidly sedimented by methylcellulose or sodium carboxymethyl starch within 15-45 min. The cells can be cryopreserved in a mixture consisting of 5% DMSO, 6% HES and 4% Albumin prepared in a Lactated Ringer solution which is widely used, and can be simply immersed into a -80 degrees C freezer and stored in liquid nitrogen until infusion. Recovery percentages of nucleated cell, cell viability and CFU-G were similar to those cryopreserved with the conventional method. Clinical toxicity was mild in 12 infused patients. Of them 8 patients had received high dose chemotherapy +/- TBI and their peripheral WBC recovery was rapid. The recovery of WBC or Platelet (PLT) in the study group was similar to that of the control group whose marrow cells were cryopreserved in 10% DMSO. Therefore, cells cryopreserved with this method can also accelerate the hematopoietic recovery in myeloablatively treated patients.
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Affiliation(s)
- K H Luo
- Department of Medical Oncology, Cancer Hospital, Chinese Academy of Medical Sciences, Beijing
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Luo KH, Sun Y, Wu GQ. [High-dose chemotherapy with autologous bone marrow transplantation in the treatment of small cell carcinoma of the lung]. Zhonghua Jie He He Hu Xi Za Zhi 1992; 15:306-8. [PMID: 1339111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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