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Assessment on the rings cleavage mechanism of polycyclic aromatic hydrocarbons in supercritical water: A ReaxFF molecular dynamics study

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Journal of Molecular Liquids 2024年 415卷

作者： Zhao, Hao Zhang, Yingjia Zhou, Shumei Chen, Ruiqi Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No. 28 Xianning West Road Shaanxi Xi'an710049 China

The ring opening reaction of polycyclic aromatic hydrocarbons (PAHs) is one of the rate-determining steps of coal gasification within supercritical water, while the involvement of water remains debated between addition and hydrogen abstraction theories. In this study, reactive molecular dynamics (MD) simulations were performed to explore the ring opening reaction of naphthalene, the simplest PAH, at temperatures of 2500–2700 K. Species and elementary reactions were quantitatively extracted from bond order trajectories using an in-house program. Reaction path analysis shows that ring opening paths of naphthalene mainly include thermolysis, H˙ atom abstraction, and O˙H radical addition. Flux analysis indicates O˙H radical largely from the H˙ + [Formula presented] = O˙H + [Formula presented] reaction, while the water dissociation [Formula presented] = O˙H + H˙ reaction is near equilibrium, seldom contributing to the O˙H source. This atomistic kinetics analysis is intended to help the modeling of supercritical water gasification of coal. © 2024 Elsevier B.V.

关键词： Naphthalene

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Simulation and Experiment on Elbow Wear in Pneumatic Conveying System

Simulation and Experiment on Elbow Wear in Pneumatic Conveyi...

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International Conference on power engineering 2021, ICOPE 2021

作者： Xiaole, Chen Qulan, Zhou Du, Wen Qingtian, Liu Na, Li State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

Elbow wear, which is most likely occurring in pneumatic conveying, becomes a key factor in development of pneumatic conveying. This paper used 3D DEM-CFD to simulate the elbow wear in pneumatic conveying system. Simulation results show that: elbow wear is linear with material mass flow rate. Elbow wear increases along with the increasement of material particle velocity. When the velocity changes from 0 to 10m/s, the elbow wear increases 3.13 times. Elbow wear increases while the radius of material particles is growing. When the particles radius increases from 0.1mm to 0.5mm, the elbow wear increases 11.13%. This paper also established a complete pneumatic conveying device for experiment. In pneumatic conveying experiment, the pressure loss was measured in situations: different airflow velocity, different velocity of material particles. The results of experiment show the same regular indicated in simulation. © 2021 The Japan Society of Mechanical Engineers.

关键词： Wear of materials

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ReaxFF-MD simulation investigation of the degradation pathway of phenol for hydrogen production by supercritical water gasification

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Energy Storage and Saving 2023年第4期2卷 578-585页

作者： Deming Zhang Shaoqi Wang Yu Feng Zixuan Wang Hui Jin School of Mechanical Engineering and Automation Harbin Institute of TechnologyShenzhenGuangdong518055China Institute of Intelligent Ocean Engineering Harbin Institute of TechnologyShenzhenGuangdong518055China State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF) Xi’an Jiaotong UniversityXi’an710049China

Wastewater from the thermochemical conversion of coal and biomass contains a significant amount of phenolic structures *** degradation of these phenolic compounds to hydrogen-rich gasses can prevent envi-ronmental pollution and save *** water(SCW)gasification of phenol is experimentally studied and a reactive force field molecular dynamics(ReaxFF-MD)simulation is conducted to investigate the catalytic mechanism of Ni/Al2 O3 in the phenol *** experimental results indicate that Ni/Al2 O3 facilitates the conversion of phenol to 1-ethoxy butane via ring opening,which is a crucial step for complete *** ReaxFF-MD simulation demonstrated that Ni facilitates the formation of H3 O free radicals and Ni-phenol inter-mediates.H3 O free radicals can be decomposed into H2 and OH free *** the generated OH free radical and Ni-phenol intermediate promote the ring-opening reaction of *** promotes the direct decomposition of phenol into C1,C2,and C3 fragments,which is beneficial for further complete gasification.

关键词： Supercritical water gasification Phenol degradation Ring opening process ReaxFF-MD

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Experimental study on the influence of the temperature and thermal Stress of water wall in different arrangements of burners

Experimental study on the influence of the temperature and t...

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International Conference on power engineering 2021, ICOPE 2021

作者： Wei, Lin Zhou, Qulan Liu, Zhuhan Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

To study the water walls' safety problems of the opposed firing boiler, thermal experiments for four typical arrangements of burners conditions are run in a laboratory-scale boiler. The four working conditions include 25% rated load (four burners are arranged side by side on the front wall), 50% rated load (eight burners are all arranged on the front wall;eight burners are arranged opposed to each other on the front and rear walls) and 100% load (front and rear walls are filled with sixteen burners). The principal strain, principal stress and temperature distribution of the water wall under four operating conditions are drawn for comparison and analysis. In addition, the results of the thermal stress, principal main stress direction and water wall temperature of the four working conditions are counted respectively to summarize the laws of them. This study highlights the influence of the temperature and thermal stress on water walls in different arrangements of burners to guide the safe operation of water walls in the real opposed firing boiler. © 2021 The Japan Society of Mechanical Engineers.

关键词： Thermal stress

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Prediction of von Mises stress on the membrane wall in a lab-scale arch-fired boiler based on artificial neural work

Prediction of von Mises stress on the membrane wall in a lab...

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International Conference on power engineering 2021, ICOPE 2021

作者： Wen, Du Zhou, Qulan Pan, Yuqing Chen, Xiaole Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

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Numerical Analysis of Thermal-Hydraulic Characteristics of the Whole Lfr Core Under Blockage Conditions

SSRN

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SSRN 2024年

作者： Yu, Jiacheng Liu, Kai Qiu, Hanrui Wang, Mingjun Tian, Wenxi Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi’an Jiaotong University Xi’an China

Blockage accidents are critical scenarios in the design and safety analysis of lead-bismuth cooled fast reactor (LFR) core. Traditional analysis of blockage accidents in LFR focuses on localized, fine-scale computational fluid dynamics (CFD) simulations of single or three assemblies, but the analysis of the whole core scale impact caused by blockage accidents is insufficient. Therefore, this paper uses CorTAF-LBE, a three-dimensional thermal-hydraulic analysis code developed by XJTU-NuTHeL, to analyze the impact of blockage accidents on the whole core of the LFR. The reliability of the code in calculating thermal-hydraulic parameters under blockage accidents was validated based on the KALLA-THEADES and KALLA-IWF experiments. Taking the MYRRHA-FASTEF core as the object, simulations and analyses are conducted for various blockage scenarios with different lengths and positions. The results indicate that blockage accidents lead to an enlarged coolant temperature gradient at the core outlet. Lengthening the blockage results in an elevation of the peak temperature in the cladding. Under 2.06% blockage at the center of the assembly, blockage in the middle of the heating segment poses the greatest threat to cladding integrity, with the maximum temperature reaching 1336.9K, an increase of 635.4K compared to normal operating conditions. Under 4.59% blockage at the edge of the assembly, the maximum cladding temperature reaches 1381.8K, and the heat transfer rate of the inter-wrapper flow (IWF) adjacent to the blockage area is 24.2% higher than under normal operation. Additionally, severe degradation in heat transfer downstream was not observed in several simulated blockage scenarios. © 2024, The Authors. All rights reserved.

关键词： Fast reactors

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MULTIPLE SOLVERS FOR IMPLICIT TEMPERATURE CALCULATION OF HEAT CONDUCTION WITH THE MPS METHOD 15

MULTIPLE SOLVERS FOR IMPLICIT TEMPERATURE CALCULATION OF HEA...

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15th World Congress on Computational Mechanics and 8th Asian Pacific Congress on Computational Mechanics: Pursuing the Infinite Potential of Computational Mechanics, WCCM-APCOM 2022

作者： Li, Sijun Zhong, Yubao Cai, Qinghang Xiao, Xinkun Guo, Kailun Chen, Ronghua Tian, Wenxi Qiu, Suizheng Su, Guanghui School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In this study, an implicit algorithm and different solvers are applied to the Moving Particle Semi-Implicit (MPS) method for temperature calculation. The original MPS method uses an explicit method for temperature calculation and is limited by time increment due to diffusion number. In this paper, the heat conduction of plates with Dirichlet boundary condition and Neumann boundary condition is studied. The accuracy of explicit and implicit calculation of plate heat transfer cases are compared. In addition, different solvers are compared. Consequently, it is shown that the error of the implicit algorithm is not much different from the original one. And CG is still the better solver, CGS is also a superior solver. The implicit algorithm increases the size of a single time step by a maximum of 50 times (original diffusion number is 0.2), while the calculation time of a single time step does not increase Substantially, so it has a significant effect on the acceleration of calculation. © 2022 WCCM-APCOM 2022 - 15th World Congress on Computational Mechanics and 8th Asian Pacific Congress on Computational Mechanics: Pursuing the Infinite Potential of Computational Mechanics. All rights reserved.

关键词： Heat conduction

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Analytical solution for temperature distribution in functionally graded cylindrical shells under convective cooling

Analytical solution for temperature distribution in function...

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作者： Emamian, Amin Amiri Delouei, Amin Karimnejad, Sajjad Jing, Dengwei International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China Department of Mechanical Engineering University of Bojnord Bojnord Iran Mechanical Engineering Department Shahrood University of Technology Shahrood Iran

In the current study, an analytical solution for the temperature distribution in a cylindrical shell that is made of functionally graded material is obtained. The general boundary condition is considered for achieving the solution, and particularly convective cooling plays the dominant role in this problem. The obtained solution is first verified against the numerical data, and then, the credibility of the solution for studying practical problems is tested employing two illustrative test cases with various boundary conditions. Parametric studies are done to evaluate some significant parameters, including material constant, boundary conditions, and convection on temperature distribution. It is seen that boundary condition plays a dominant role in the cooling rate. Material constant does not have a significant effect on the temperature distribution. The current study can be hired to better the design and production process of cylindrical shells made of functionally graded material. © 2021 John Wiley & Sons, Ltd.

关键词： Functionally graded materials

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Experimental Study on Preparation of Amorphous SiO2 by Fluidized Bed Combstion of Rice Husk

Experimental Study on Preparation of Amorphous SiO2 by Fluid...

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International Conference on power engineering 2021, ICOPE 2021

作者： Tan, Jingkao Zhou, Qulan Yao, Yashu Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

Rice husk ash contains SiO2 with a mass fraction of 87%-97%. Through controlled combustion under suitable conditions, SiO2 in rice husk ash will be amorphous, with high activity and rich porosity, which can be applied to construction, silicon preparation and adsorption *** it is necessary to study the effects of combustion parameters on the quality of RHA. Compared to conventional boiler furnace, the fluidized bed combustor has a lower combustion temperature and a longer residence time, which is suitable for the production of high quality amorphous rice husk ash. In this thesis, the effects of fluidized bed combustion parameters on the quality of RHA will be studied to provide guidance for amorphous SiO2 preparation by combustion control in boiler. On the existing 15kw bench-scale fluidized bed system, experiments were made to study the effects of fluidized bed combustion parameters on the quality of RHA. The rice husk combustion curve was comprehensively depicted, and the rice husk ash was analyzed by BET analysis, XRD scanning and thermogravimetric analysis. Therefore, the casual relationship between rice husk combustion process and RHA quality was evaluated comprehensively. © 2021 The Japan Society of Mechanical Engineers.

关键词： Quality control

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Experimental study on the CO-SCR performance of honeycomb-based Fe-Cu/RHA catalyst

Experimental study on the CO-SCR performance of honeycomb-ba...

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International Conference on power engineering 2021, ICOPE 2021

作者： Pan, Yuqing Li, Na Wen, Du Ran, Shiyuan Wu, Chenyang Zhou, Qulan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

The combustion process of carbon-based fuels will produce CO. If CO can be used as a reducing agent to remove NO, the goal of removing NO and unburned carbon (UBC) simultaneously can be achieved. When rice husk ash (RHA) rich in amorphous SiO2 is used to support Fe-Cu metal oxides, its huge specific surface area and non-lattice microstructure can reduce the reaction temperature, so that Fe-Cu/RHA catalyst has a high performance of selective catalytic reduction of NO by CO (CO-SCR). The paper used honeycomb ceramic to support Fe-Cu/RHA catalyst, and studied the effects of preparation method, active ingredient loading and reaction conditions on the CO-SCR performance of integral catalyst. The experimental results showed that the integral catalyst obtained by the heating and stirring method was better than the room temperature method. The conversion rates of CO and NO of the integral catalyst increased with the increase of the active ingredient loading. Besides, the oxygen concentration had little effect on the conversion rates of NO and CO. The conversion rate of CO to CO2 increased with the increase of temperature, and it could reach up to 98%. The conversion rate of NO to N2 fluctuated slightly as the temperature increased. © 2021 The Japan Society of Mechanical Engineers.

关键词： Selective catalytic reduction

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