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Morphology Structure Evolution and Combustion Reactivity of Bituminous Char at Around Ash Melting Temperature

Journal of Thermal Science 2022年第6期31卷 2189-2202页

作者： ZHANG Yandi YANG Huan WANG Bo HMShahzaib KHAN DUAN Xiaoli LIU Yinhe State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi'an Jiaotong UniversityXi'an 710049China

In slag tapping furnaces, char particles undergo a series of complex structural evolution before and after being captured by the liquid slag layer. The evolution results affect the carbon conversion rate and are affected by temperature fluctuations, especially in the ash melting temperature zone. Experimental study on structure evolution of bituminous char prepared at around ash melting temperature was carried out on a fixed bed. The morphology, specific surface area and mineral chemical composition were measured at different temperatures. Experimental results show that the number density and the size of ash droplets exuded on the char surface increased significantly with the increasing temperature. The ash specific surface area from gasification was slightly greater than that from combustion. The residual content of chloride in the char become 1% and the contents of Fe, K, Mg and Na decrease significantly during the pyrolysis process across the ash melting temperature zone. The diffraction intensity of oldhamite increase which indicates the reaction of carbon substrate with minerals during the evolution;the diffraction intensity of quartz dramatically decreases for the reason of anorthite generation. The ignition and burnout temperatures of char were found to increase and the combustion stability decreased with the increasing pyrolysis temperature.

关键词： coal char structure evolution carbothermal reaction combustion

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Fabricating PdCe/OMS-2 catalysts with boosted low-temperature activity for toluene deep degradation

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Journal of Rare Earths 2023年第6期41卷 839-849,I0002页

作者： Lin Yue Zhihua Xu Minghua Hu Mingjiao Tian Mudi Ma Bijie Huang Chi He State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an 710049China State Key Laboratory of Precision Blasting and Hubei Key Laboratory of Industrial Fume and Dust Pollution Control Jianghan UniversityWuhan 430056China National Engineering Laboratory for VOCs Pollution Control Material&Technology University of Chinese Academy of SciencesBeijing 101408China

Porous cryptomelane-type octahedral molecular sieve(OMS-2)with mixed Mn valence and abundant lattice oxygen species has attracted much attention in volatile organic compounds(VOC)catalytic ***,complete conversion of arene over OMS-2 catalysts at relatively low temperature is still a challenge due to its limited crystal structure and inferior ***,a series of PdCe/OMS-2 catalysts with different Pd/Ce molar ratios was fabricated by a facile impregnation method and the physicochemical properties of which were extensively characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HR-TEM),B runauer-Emmett-Teller(BET)method,X-ray fluorescence(XRF),X-ray photoelectron spectroscopy(XPS),temperature programmed reduction of H2(H2-TPR),Raman,In situ diffused reflectance infrared Fourier transform spectra(DRIFTS),and density functional theory(DFT)*** show that the total conversion of toluene can be achieved at 207℃ over PdCe2 with apparent activation energy as low as 62.6 kJ/*** strong synergistic effect between Pd and Ce remarkably boosts the catalytic activity of OMS-2,attributed to the abundant Mn^(3+)-O bands and active surface oxygen *** results reveal that oxygen vacancy can be formed over PdCe2 much easily than that of Pd/OMS-2 and Ce/OMS-2 with the oxygen vacancy formation energy of2.42,2.83 and 2.68 eV,*** increasing the Pd content cannot promote the catalytic activity although PdO is a critical active center in toluene *** vacancy attributed to the integrative effect of Pd,Ce and Mn species plays a promine nt role over prepared catalysts in toluene activation *** findings reported in this work showed new insights into the designing of highly efficient OMS-2catalysts for VOC deep oxidation by tuning oxygen vacancy concentration.

关键词： PdCe/OMS-2 Toluene Catalytic oxidation Oxygen vacancy Rare earths

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Numerical Stability and Accuracy of Contact Angle Schemes in Pseudopotential Lattice Boltzmann Model for Simulating Static Wetting and Dynamic Wetting

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Computer Modeling in engineering & Sciences 2023年第10期137卷 299-318页

作者： Dongmin Wang Gaoshuai Lin Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering School of Energy and Power EngineeringUniversity of Shanghai for Science and TechnologyShanghai200093China Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application Suzhou University of Science and TechnologySuzhou215009China

There are five most widely used contact angle schemes in the pseudopotential lattice Boltzmann(LB)model for simulating the wetting phenomenon:The pseudopotential-based scheme(PB scheme),the improved virtualdensity scheme(IVD scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the fluid layer density above the wall(MPB-C scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the weighted average density of surrounding fluid nodes(MPB-W scheme)and the geometric formulation scheme(GF scheme).But the numerical stability and accuracy of the schemes for wetting simulation remain unclear in the *** this paper,the numerical stability and accuracy of these schemes are clarified for the first time,by applying the five widely used contact angle schemes to simulate a two-dimensional(2D)sessile droplet on wall and capillary imbibition in a 2D channel as the examples of static wetting and dynamic wetting simulations respectively.(i)It is shown that the simulated contact angles by the GF scheme are consistent at different density ratios for the same prescribed contact angle,but the simulated contact angles by the PB scheme,IVD scheme,MPB-C scheme and MPB-W scheme change with density ratios for the same fluid-solid interaction *** PB scheme is found to be the most unstable scheme for simulating static wetting at increased density ratios.(ii)Although the spurious velocity increases with the increased liquid/vapor density ratio for all the contact angle schemes,the magnitude of the spurious velocity in the PB scheme,IVD scheme and GF scheme are smaller than that in the MPB-C scheme and MPB-W scheme.(iii)The fluid density variation near the wall in the PB scheme is the most significant,and the variation can be diminished in the IVD scheme,MPB-C scheme *** variation totally disappeared in the GF scheme.(iv)For the simulation of capillary imbibition,the MPB-C scheme,MPB-Wschem

关键词： Pseudopotential lattice Boltzmann model contact angle scheme static wetting dynamic wetting capillary imbibition

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On the Intelligent Optimization of the Crevice Structure in a Rapid Compression Machine

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Journal of Thermal Science 2024年第3期33卷 1200-1215页

作者： GUO Qiang LIU Jie WU Yingtao WANG Hewu TANG Chenglong YU Ruiguang Department of Power Mechanical Engineering Beijing Jiaotong UniversityBeijing100044China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijing100084China Beijing Key Laboratory of New Energy Vehicle Powertrain Technology Beijing100044China National International Science and Technology Cooperation Base Beijing Jiaotong UniversityBeijing100044China

In this study,the multi-objective intelligent optimization of the crevice structure in a rapid compression machine(RCM)is carried out based on the RCM simulation model modified with the KIVA-3V program.A multi-objective optimization simulation model of the crevice structure based on the large eddy simulation model coupled with the genetic algorithm NSGA-Ⅲis *** optimization parameters and seven optimization objectives are selected in the optimization *** results show that the genetic algorithm can quickly find the values of the optimized *** crevice volume ratio shows a trade-off relationship with the dimensionless temperature ratio T_(max)/T_(aver)and the tumble ratio.A larger crevice volume can reduce the flow of boundary layer cryogenic gas into the combustion chamber,thus improving the temperature *** addition,the crevice entrance width and the connecting channel length should be smaller,while the volume of the crevice main chamber should be larger,so as to sufficiently introduce the low-temperature gas of the boundary layer into the crevice and reduce their influence on the temperature field of the combustion *** the crevice volume accounts for10%of the total volume,the temperature uniformity of the combustor is significantly enhanced,and when the crevice volume accounts for 30.4%,there is almost no low-temperature vortex in the combustion chamber.

关键词： rapid compression machine adiabatic core area ignition delay period crevice structure

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The Molecular Dynamics Simulation of Thermal Properties of R290 for Auto-cascade Refrigeration System

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Recent Patents on Mechanical engineering 2023年第5期16卷 345-358页

作者： Feng, Haocheng Liu, Zhenzhen Wang, Zilong Zhang, Hua School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

Background: Hydrocarbons are increasingly being considered as potential fourth-generation refrigerants due to their environmentally-friendly properties. However, accurate prediction and calculation of their thermal properties are essential for their industrial application. Objective: In this study, molecular dynamics simulations were performed to calculate the density, self-diffusion coefficient, viscosity and thermal conductivity of R290 at various operating temperatures of 200-240 K and pressures of 0.15 and 0.20 MPa, and 270-390 K and pressures of 1.5 and 2.0 MPa to veri-fy the feasibility of the methods. Methods: The equilibrium molecular dynamics simulation (EMD) approach was utilised. The soundness of the model and force field were verified by calculating the density of the system during the relaxation phase. In the output stage, the self-diffusion coefficient was calculated using the Einstein relation, while the viscosity and thermal conductivity were calculated using the Green-Kubo method. The simulation results were compared with the NIST data values, and the errors were analysed. Results: The density simulation results for R290 in the relaxation phase yielded an overall average absolute relative deviation (AARD) value of 3.97%. In the output stage, the simulation results for the transport coefficients of R290 showed AARD values of 7.68%, 6.60% and 11.04% for the self-diffusion coeffi-cient, viscosity, and thermal conductivity, respectively, compared to the NIST data values. Conclusion: These results indicate the feasibility of using molecular dynamics simulations to study the transport properties of hydrocarbon refrigerants. The findings also provide a foundation for future research on hydrocarbon refrigerant mixtures. Patent: The research presented in this work could serve as a valuable reference for future patent applications and technological innovations related to hydrocarbon refrigerants, particularly R290. This includes, but is not limited to, delive

关键词： Viscosity

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Experimental and Theoretical Study on CHF of a Ultra-Supercritical Circulating Fluidized Bed Boiler Water-Wall Tube at near-Critical Pressures

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Journal of Thermal Science 2023年第1期32卷 166-182页

作者： WANG Wenyu MA Zhan QING Hao NIE Chao YANG Haoyu BI Lingfeng YANG Dong PAN Wenxiao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China Department of Mechanical Engineering University of Wisconsin-Madison1513 University AveMadisonWI 53706USA

The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been *** particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°*** material of the tube is *** experimental investigation,the near critical pressure CHF test data of water are *** find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is *** the experimental data,a correlation function for the CHF is established via regression and machine *** established via machine learning greatly improved the regression *** study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type *** the development of the CHF model,the friction resistance coefficient is determined according to our test *** comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type *** calculation results of the model can provide reference for the optimal design of the USCFB boiler.

关键词： circulating fluidized bed critical heat flux near-critical pressure bubble crowding machine learning

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Numerical prediction of spatio-temporal frosting patterns of curved surface considering varying working parameters

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Energy Storage and Saving 2023年第1期2卷 348-358页

作者： Xue Liu Xiaojun Dong Shaohang Yan Yu Hou Tianwei Lai State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China

Accurate numerical prediction of frosting patterns is essential for the efficient layout and timing defrosting of heat exchangers under frosting *** this study,a numerical model is developed to predict the spatio-temporal frosting habits on curved surfaces in combination with the correlations of frost density and thermal *** the model,frost melting is *** verification,the frosting and heat transfer characteristics along the flow path are investigated under various structural and operating *** thickness along the path is mainly affected by the cooling surface temperature,while the heat and mass transfer rates are strongly correlated with the humidity *** proportions of latent heat and sensible heat are distributed more unevenly in parallel flow case than in counter flow *** deposition is facilitated by a smaller radius of curvature of the cooling *** uniform frosting characteristics along the path and smaller heat transfer obstruction are presented with a smaller length-to-height ratio of the flow path.

关键词： Frosting Numerical prediction Heat transfer Curved surface Varying parameter

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Alloy nanocrystals:Synthesis paradigms and implications

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Chinese Journal of Structural Chemistry 2023年第11期42卷 1-5页

作者： Zhaojun Liu Zerui Mu Chuanbo Gao State Key Laboratory of Multiphase Flow in Power Engineering Frontier Institute of Science and TechnologyXi'an Jiaotong UniversityXi'an710054China

*** Noble metal nanocrystals serve as exceptional catalysts across a wide spectrum of industrial processes[1].Moreover,there exists a substantial demand for noble metal catalysts in emerging clean-energy applications,such as water-splitting hydrogen production and fuel *** non-noble transition metals or main-group metals into noble metal nanocrystals can reduce the weight of noble metals in the catalysts,thus remarkably lowering the ***,alloy nanocrystals offer intriguing catalytic properties that surpass those of their monometallic counterparts,thanks to the charge transfer between the constituent components and the expansion or shrinkage of the lattice size[2].

关键词： alloy metals noble

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MIXED DISCONTINUOUS GALERKIN METHOD FOR QUASI-NEWTONIAN STOKES flowS

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Journal of Computational Mathematics 2024年第3期42卷 885-910页

作者： Yanxia Qian Fei Wang Wenjing Yan School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China School of Mathematics and Statistics&State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

In this paper,we introduce and analyze an augmented mixed discontinuous Galerkin(MDG)method for a class of quasi-Newtonian Stokes *** the mixed formulation,the unknowns are strain rate,stress and velocity,which are approximated by a discontinuous piecewise polynomial triplet ■for k≥***,the discontinuous piecewise polynomial function spaces for the field of strain rate and the stress field are designed to be *** addition,the pressure is easily recovered through simple *** the benefit of the analysis,we enrich the MDG scheme with the constitutive equation relating the stress and the strain rate,so that the well-posedness of the augmented formulation is obtained by a nonlinear functional *** k≥0,we get the optimal convergence order for the stress in broken ■(div)-norm and velocity in L^(2)-***,the error estimates of the strain rate and the stress in-norm,and the pressure in L^(2)-norm are optimal under certain ***,several numerical examples are given to show the performance of the augmented MDG method and verify the theoretical *** evidence is provided to show that the orders of convergence are sharp.

关键词： Quasi-Newtonian fows Mixed discontinuous Galerkin method Symmetric strain rate Symmetric stress Optimal convergence orders

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Experimental study on the thermochemical reduction of supercritical CO2by guaiacol 8

Experimental study on the thermochemical reduction of superc...

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8th International Conference on Smart and Sustainable Technologies, SpliTech 2023

作者： Wei, Yimeng Kuanibieke, Jiadela Jin, Hui Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering China

ISBN: (纸本)9789532901283

The continuous growth of CO2 emissions is one of the global problems facing humanity, and how to convert and exploit the stock of CO2 has become an urgent issue. Biomass as an activity of CO2 thermal reduction medium has become the focus of human attention in general. Supercritical CO2 (SCCO2) has the advantages of near-liquid density and high solubility, which can further strengthen the reduction process (T≥31.26, P≥72.9 atm). This paper described a SCCO2 reduction method of guaiacol on an intermittent Kettle Reactor to investigate the effects of reaction temperature (400-700), residence time (5-20 min) and reactant concentration (4 wt%-16wt%) on the three-phase products. The experimental results indicated that the carbon gasification efficiency (CE) and hydrogen gasification efficiency (HE) were 43.7% and 56.7%, respectively, when the carbon dioxide consumption reached 16.15 mol/kg. As the temperature increased, the consumption of carbon dioxide increased and the concentration of reactants increased with opposite results. © 2023 University of Split, FESB.

关键词： Carbon dioxide

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