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Multi-Scale simulation of a Novel Integrated Reactor for Hydrogen Production by Ammonia Decomposition

CHEMIE INGENIEUR TECHNIK 2024年第5期96卷 627-641页

作者： Blauth, Sebastian Damay, Julie Osterroth, Sebastian Leithaeuser, Christian Hofmann, Christian Kolb, Gunther Wichert, Martin Steiner, Konrad Bortz, Michael Fraunhofer Inst Ind Math Fraunhofer ITWM Fraunhofer Pl 1 D-67663 Kaiserslautern Germany Fraunhofer Inst Microengn & Microsyst IMM Carl Zeiss Str 18-20 D-55129 Mainz Germany

A novel reactor concept for ammonia decomposition utilizing tail gas from a purification unit as heat supply is presented. The designed micro-structured reactor integrates both endothermic ammonia decomposition and exothermic tail gas combustion. The reactor and corresponding process are simulated using a mathematical multi-scale model, which combines the results of multiple detailed computational fluid dynamics simulations into a fast surrogate model. The latter is coupled with a process simulation software via a so-called container to simulate the entire process. The efficiency of the presented reactor concept is determined and benefits over alternative approaches are highlighted. A new concept for hydrogen production by ammonia decomposition using tail gas from a pressure swing adsorption unit in an integrated micro-structured reactor is presented. A multi-scale process simulation model is provided, which combines process simulation with a surrogate reactor model derived from computational fluid dynamics simulations. image

关键词： Ammonia decomposition computational fluid dynamics simulation Hydrogen production Multi-scale simulation Process simulation

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The impact of the wind attack angle on a typical bridge deck's flutter behavior by the distributed aerodynamic characteristics method

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JOURNAL OF VIBRATION AND CONTROL 2024年第3-4期30卷 727-739页

作者： Li, Ke Yang, Qingshan Wang, Xianmeng Li, Shaopeng Hui, Yi Fang, Genshen Qian, Guowei Chongqing Univ Key Lab New Technol Construct Cities Mt Area Minist Educ Chongqing Peoples R China Chongqing Univ Sch Civil Engn Chongqing Peoples R China Chongqing Key Lab Wind Engn & Wind Energy Utilizat Chongqing Peoples R China Tongji Univ State Key Lab Disaster Reduct Civil Engn Shanghai Peoples R China Univ Tokyo Sch Engn Dept Civil Engn Bunkyo Ku Tokyo Japan Chongqing Univ Sch Civil Engn 83 Shabei St Chongqing 400045 Peoples R China

To investigate the influence of the wind attack on a bridge deck's flutter performance, the concept of "pressure flutter derivatives" was introduced as a part of the "distributed aerodynamic characteristics" method, which can be used to visualize the dominant fluctuations of the pressure field. The distributions of the aerodynamic damping and stiffness under different wind attack angles were visualized, instead of using an overall force perspective. The analysis was carried out through two-dimensional computational fluid dynamics simulations based on a typical box deck section. Necessary data were obtained through the forced vibrations of the deck. The dominant pressure fluctuations were demonstrated, around which the wind attack angles' impact on the Scanlan flutter derivatives was discussed. For the deck section used in this study, the wind attack angle was found to most affect the windward parts of the deck. When wind attack angle ranged from -1.5 degrees to 3 degrees, two regions contributed the most: one located behind the windward faring vertex and the other located behind the first vertex of the upper slab. When the wind attack angle decreased to -3 degrees, a new dominant region appeared behind the first vertex of the lower slab, which caused a sudden reduction of the flutter critical speed.

关键词： Bridge aerodynamics wind attack angle aerodynamic damping distributed aerodynamic characteristics method computational fluid dynamics simulation

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A two-level optimisation approach for underground natural ventilation based on CFD and building energy simulations

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ENERGY AND BUILDINGS 2024年 310卷

作者： Wen, Yueming Wei, Jinxi Lau, Siu-Kit Gu, Zhenhong Leng, Jiawei Zhengzhou Univ Sch Architecture Zhengzhou 450001 Peoples R China Deakin Univ Sch Architecture & Built Environm Geelong Vic 3220 Australia Natl Univ Singapore Dept Architecture Singapore 117566 Singapore Southeast Univ Sch Architecture 2 Sipailou Nanjing 210096 Jiangsu Peoples R China Southeast Univ Nanjing Urban Planning Design Inst Nanjing 210096 Peoples R China

Natural ventilation is a historical and promising passive design for conserving building energy. However, a noticeable scarcity exists in design strategies and academic studies on underground natural ventilation. This study introduces a two-level optimisation approach for underground natural ventilation, considering form and environmental characteristics. At the initial level, computational fluid dynamics simulations were employed to quantify and visualise the momentary ventilation performances of various passive strategies. These simulations also furnished precise wind pressure coefficients. Subsequently, at the second level, this study predicted the annual energy savings of the proposed prototype by integrating an airflow network model with building energy simulations. To adapt design parameters, sensitivity analysis and multi-objective optimisation techniques were applied. These numerical models underwent validation against measured data from analogous studies. The results reveal that the 'inlet buried pipe + outlet shaft' led to a 6.9 % reduction in energy consumption for heating, ventilation, and air-conditioning in underground hybrid ventilation compared to underground mechanical ventilation. Moreover, it achieved a 28.8 % decrease compared to aboveground mechanical ventilation. Optimising air temperatures following climate, soil conditions, and building characteristics is imperative, aligning with design standards. This study contributes a quantitative and visual approach to support underground natural ventilation and addresses the limitations of empirical designs, providing a foundation for future research and practical applications.

关键词： Underground natural ventilation Performance prediction computational fluid dynamics simulation Building energy simulation Multi -objective optimization

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Surrogate-based aerodynamic shape optimization of high-speed train heads: A review of four key technologies

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART F-JOURNAL OF RAIL AND RAPID TRANSIT 2024年第8期238卷 907-920页

作者： Wang, Hongbo Wang, Shuangbu Zhuang, Dayuan Zhu, Zaiping You, Pengcheng Tang, Zhao Ding, Guofu Southwest Jiaotong Univ Sch Mech Engn Chengdu Peoples R China Southwest Jiaotong Univ Inst Smart City & Intelligent Transportat 999 Xian Rd Chengdu 611756 Peoples R China Southwest Jiaotong Univ State Key Lab Rail Transit Vehicle Syst Chengdu Peoples R China Bournemouth Univ Natl Ctr Comp Animat Poole England

With the increase in running speed, the aerodynamic characteristics of high-speed trains have a significant impact on running stability, energy consumption and passenger comfort. Since the shape of the high-speed train head can directly influence the surrounding airflow, optimizing the head shape is the primary way to improve the aerodynamic performance of the train. This paper reviews current research studies on the surrogate-based aerodynamic shape optimization of high-speed train heads, aiming to provide a comprehensive reference for designers to enhance design efficiency and optimization performance. The entire optimization process is divided into four essential steps, and the key optimization technologies in each step are discussed, including parametric modeling, computational fluid dynamics (CFD) simulation, surrogate model and optimization algorithm. By introducing the practical applications of these technologies, we summarize their advantages and disadvantages and suggest four potential research directions for the future.

关键词： High-speed train shape optimization parametric modeling computational fluid dynamics simulation surrogate model optimization algorithm

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Investigate mechanisms of different printing parameters on the mechanical anisotropy of 3D concrete printing elements by using computed tomography scan and computational fluid dynamics methods

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ADDITIVE MANUFACTURING 2025年 103卷

作者： Liu, Zhenbang Li, Mingyang Wang, Xiangyu Wong, Teck Neng Tan, Ming Jen Nanyang Technol Univ Singapore Ctr 3D Printing 50 Nanyang Ave Singapore 639798 Singapore Nanyang Technol Univ Sch Mech & Aerosp Engn 50 Nanyang Ave Singapore 639798 Singapore

3D concrete printing (3DCP) elements show significant mechanical anisotropy. Printing parameters can affect the mechanical anisotropy of 3DCP elements. However, most studies have focused on the effects of printing parameters on the interlayer bond strength at a macroscale level. The mechanisms of printing parameters on the mechanical anisotropy of 3DCP elements remain unclear. To fill research gaps, computed tomography (CT) scans, computational fluid dynamics (CFD) numerical simulations, and uniaxial compression tests (UCTs) were conducted with the printing parameters of the expansion state of the nozzle flow channel, overflow ratio, standoff distance, and flow rate involved. The results of CT scans, CFD simulations, and UCTs revealed the mechanism that the printing parameters affect porosity distribution and pore anisotropy by influencing the normalized local pressure at interlayer and fluid velocity gradients, respectively, which further results in the modification of the mechanical anisotropy of 3DCP elements.

关键词： 3D concrete printing Anisotropic performance Computed tomography scan computational fluid dynamics simulation Printing parameter

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Towards maximum hydrogen output from methylcyclohexane dehydrogenation coupled with catalytic hydrogen combustion: An experimental and simulation study

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2025年 98卷 807-819页

作者： Wang, Shiyao Si, Hao Li, Ping Cao, Chenxi East China Univ Sci & Technol Sch Chem Engn State Key Lab Green Chem Engn & Ind Catalysis Shanghai 200237 Peoples R China East China Univ Sci & Technol Key Lab Smart Mfg Energy Chem Proc Minist Educ Shanghai 200237 Peoples R China

We performed dehydrogenation of methylcyclohexane with recuperative heat supply from catalytic hydrogen combustion in a fixed-bed reactor for obtaining chemically stored hydrogen. A hydrogen distributor was adopted to modulate the temperature field by hydrogen combustion to synchronize the kinetics of combustion and dehydrogenation reactions. An average hydrogen production rate of 1075 mLN/min and a conversion of 86.0% for dehydrogenation were achieved over a 45-h continuous operating at a liquid hourly space velocity of 1.09 g/ gcat/h on 100 g Pt/Al2O3 catalyst. A three-dimensional computational fluid dynamics model was built to investigate the spatial distribution of temperature and species composition. It indicated that the hydrogen distributor design, featuring orifices along both the axial and radial directions, improved the temperature distribution and thus the conversion. The hydrogen flowrate emerged as the primary factor affecting the temperature distribution within the reactor. The technical potential of the proposed integrated hydrogen production system was evaluated, showcasing superior performance compared to reported systems using coupled fuel combustion, with a reaction efficiency of 43.7%, an energy efficiency of 61.1%, and a net hydrogen production efficiency of 34.9%. Our study offers theoretical guidelines for the engineering of large-scale stationary hydrogen storage utilizing liquid organic hydrogen carriers.

关键词： Methylcyclohexane dehydrogenation Catalytic hydrogen combustion Coupled reactor Hydrogen distributor Energy utilization efficiency computational fluid dynamics simulation

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Numerical analysis of dry heat transfer in textiles and clothing microclimate

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TEXTILE RESEARCH JOURNAL 2025年

作者： Gao, Zenghui Zheng, Dongming Guo, Kai Zou, Haochen Ding, Wensheng Du, Zhaoqun Xue, Jingli Jin, Guang Mou, Huangbo Donghua Univ Coll Text Key Lab Text Sci & Technol Minist Educ Shanghai Peoples R China Jiangxi Gen Inst Testing & Certificat Inst Text Testing & Certificat Nanchang Peoples R China Consinee Grp Co Ltd Ningbo Zhejiang Peoples R China

The computational fluid dynamics approach has been widely applied to explore the comfort level of human clothing. In many studies, the human limbs and trunk are treated as a uniform cylinder, yet there is a failure to consider the uniformity of airflow velocity and temperature on the surface of clothing. This poses challenges for the testing of cylindrical fabric thermal and moisture resistance to assess clothing comfort. In this study, a 2D heat transfer model for porous textiles under different airflow and temperature conditions was established. Then, a comparative analysis was conducted of three air supply methods. The results show that the wind speed difference rates generated on the surface of the clothing by these three air supply methods were 83.3%, 65.1%, and 1.9%, respectively. To ensure that the wind speed on the surface of the clothing is as uniform as possible, method 3 was adopted to establish the wind field. In this study, the combined influences of thermal conduction, natural convection, and forced convection were incorporated to investigate the distribution of temperature and wind fields within the model, as well as the changes in clothing performance under various environmental conditions. Additionally, the microclimate between the skin and clothing directly affects human comfort. Therefore, in this study, heat transfer phenomena within the microclimate were also explored under different environmental conditions. The model in this paper is intended to provide an effective and accurate method for cylindrical fabric thermal and moisture resistance testing, to study the comfort of clothing.

关键词： Heat transfer computational fluid dynamics simulation clothing microclimate heat flux

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Family of Skeletal Reaction Mechanisms for Methane-Oxygen Combustion in Rocket Propulsion

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JOURNAL OF PROPULSION AND POWER 2024年第2期40卷 303-319页

作者： Liberatori, Jacopo Malpica Galassi, Riccardo Bianchi, Daniele Nasuti, Francesco Valorani, Mauro Paolo Ciottoli, Pietro Univ Rome Sapienza Dept Mech & Aerosp Engn Via Eudossiana 18 I-00184 Rome Italy

Analyzing methane-oxygen rocket propellant combinations requires suitable modeling of the major chemical reaction processes. Although several detailed kinetic mechanisms for methane oxidation in air exist, most do not reproduce the reaction pathways of high-pressure methane-oxygen combustion, typical of liquid rocket engines. Moreover, when large-scale computational fluid dynamics simulations are pursued, detailed reaction schemes are not computationally viable. In the present study, we identify a reliable detailed kinetic scheme for liquid rocket applications, and then we perform a wide reduction campaign leveraging computational singular perturbation theory. Enforcing various reduction targets, we obtain a family of seven skeletal schemes, including 11-39 species. Each mechanism targets different combustion modes, namely, homogeneous ignition, complex flows and flame extinction, premixed burning, reaction processes under intense turbulent mixing, and largely off-stoichiometric mixtures, typical of rocket engine preburners. We test the skeletal mechanisms against meaningful validation targets, attaining appreciable predictive accuracy compared with the detailed parent scheme. We expect the proposed family of skeletal schemes to offer a wide and flexible range of solutions-in terms of size, accuracy, and dominant combustion mode-for performing large-scale yet cost-affordable computational fluid dynamics of methane-oxygen flames under rocket-engine-relevant conditions.

关键词： Rocket Propulsion System computational fluid dynamics simulation Turbulent Mixing Turbulent Combustion Liquid Rocket Chemical Kinetics Green Propulsion Methane Rocket Engine

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Investigation of Surface-Catalycity Effects on Hypersonic Glide Vehicle Trajectory Optimization

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JOURNAL OF SPACECRAFT AND ROCKETS 2024年第4期61卷 1019-1031页

作者： Rataczak, Jens A. Chaudhry, Ross S. McMahon, Jay W. Boyd, Iain D. Univ Colorado Boulder Ann & HJ Smead Dept Aerosp Engn Sci Boulder CO 80303 USA

The optimization of a hypersonic glide vehicle's reachable domain is studied using different models to constrain the stagnation-point heat transfer. The vehicle is modeled as a high-lift common aero vehicle that uses bank-angle modulation for crossrange maneuvering with a leading-edge thermal protection system made of an ultra-high-temperature ceramic. A constrained nonlinear optimization problem is formulated to determine the range of feasible trajectories that satisfy aerodynamic heating and loading constraints. The optimal control profile is determined using a modified particle swarm optimization routine that employs a penalty function approach to handle path and terminal constraints. Baseline trajectories are determined using an existing convective heat-flux correlation, and the effect of surface catalycity on the optimized trajectories is investigated by applying a correction factor, derived from high-fidelity computational fluid dynamics simulations, to the heat-flux correlation. Results demonstrate a high sensitivity of the optimized trajectories to the underlying aerothermodynamics model such that accounting for surface catalycity expands the reachability by an order of magnitude.

关键词： Hypersonic Aerothermodynamics Heat Flux Stagnation Region Aerodynamic Characteristics Thermal Control and Protection computational fluid dynamics simulation Heat Transfer Coefficients Trajectory Optimization Hypersonics Particle Swarm Optimization

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Airfoil Design and Flow Analysis of a Multi-Blade Centrifugal Fan: An Experimental and simulation Study

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APPLIED SCIENCES-BASEL 2024年第23期14卷

作者： Yin, Haonan Zhao, Hanqing Li, Yiping Zhao, Jie Zhang, Kai China Jiliang Univ Coll Metrol & Measurement Engn Hangzhou 310018 Peoples R China

To overcome the technical challenges of the multi-blade centrifugal fan, such as low efficiency and insufficient total pressure, the blades of the fan were optimally designed in this study. The flow field of the multi-blade centrifugal fan with a single-arc blade and an airfoil blade was simulated and compared using computational fluid dynamics (CFDs). Under steady-state conditions, the total pressure, velocity field distribution, and aerodynamic performance of a multi-blade centrifugal fan were analyzed. The numerical results showed that there were vortices, secondary flows, and boundary layer separation phenomena in the flow passage of the single-arc multi-blade centrifugal fan. Based on the lift-to-drag ratio theory of airfoil in aerodynamics, four different airfoil blades were designed for the multi-blade centrifugal fan. The study found that the lift-to-drag ratio of the airfoil blades was positively correlated with the fan efficiency;among them, the A-type airfoil exhibited the highest lift-to-drag ratio within the 0-10 degree angle of attack range. The three-dimensional simulation results indicated that, except for the initial operating point B, the A-type airfoil showed higher fan efficiency under other operating conditions, and its total pressure curve was the most stable. In addition, the use of airfoil blades effectively suppressed the aforementioned adverse flow phenomena and improved the flow within the blade passage. Experimental verification further confirmed the effect of airfoil blades on improving fan performance: compared to single-arc blades, the efficiency of the multi-blade centrifugal fan increased by 3-7% after using airfoil blades, and the upper limit of high-efficiency flow increased from 450 m3/h to 650 m3/h. Meanwhile, the total pressure and power of the airfoil fan were also significantly improved. The results of this work are significant for guiding the optimal design of the fan.

关键词： multi-blade centrifugal fan airfoil flow field lift-to-drag ratio computational fluid dynamics simulation k-epsilon turbulence model SST k-omega turbulence model

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