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SSRN 2023年

作者： Ren, Jiyun Yang, Kaixuan Li, Yuhang Bai, Yang Jiang, Jiahao Huang, Xiaole Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Shanghai Power Equipment Research Institute Co. Ltd. Shanghai200240 China Xi’an Thermal Power Research Institue Co. Ltd. Xi’an710032 China

To evaluate the effect of alkali and alkaline earth metals species (AAEMs) on the catalytic gasification of large particle size biomass, a vertical fixed-bed reactor is conducted for candlenut wood gasification under the oxygen-stream atmosphere. The gasification chars derived from gasification are characterized by SEM, X-ray CT, BET, and FTIR. Tar and syngas are analyzed via GC-MS and GC respectively. Advanced X-ray CT technology provides beneficial visualization to assist in the interpretation of the catalytic gasification of large particle size biomass loaded with AAEMs. The results indicate a progressive augmentation of AAEMs content along the radial direction and end surface for all loaded samples and gasification chars, which could also be visualized from the 3D reconstruction of X-ray CT. Many large pores (40-60 μm) aligned along the grain direction collapse after gasified and generate numerous micropores in gasification chars. 10-20 μm pores are more prominent in chars loaded with KCl and CaCl2. The char loaded with CaCl2 has more well-developed pores, a larger specific surface area, and -OH compounds, aldehydes, ketones and carboxylic acids. The addition of AAEMs facilitates the high generation of M1 compounds (contains 1 benzene ring) in the tar and suppresses the enhancement of other compounds, M4 compounds, and long-chain alkanes. H2 and CO concentrations augments and declines by loading AAEMs. The highest H2 concentration of 62.1% is detected by the addition of CaCl2. When loaded with KCl, the syngas calorific value reduces by 1.37%, while loaded with NaCl, CaCl2, and MgCl2 show an augmentation of 11.48%, 10.56%, and 2.55%, respectively. A decrement of CnHx concentration in syngas derived from samples loaded with KCl and MgCl2 and an increment one loaded with NaCl and CaCl2 are acquired. © 2023, The Authors. All rights reserved.

关键词： Oxygen

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Adaptive Growing Randomized Neural Networks for Solving Partial Differential Equations

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arXiv 2024年

作者： Dang, Haoning Wang, Fei Jiang, Song School of Mathematics and Statistics Xi’an Jiaotong University Shaanxi Xi’an710049 China School of Mathematics and Statistics State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Institute of Applied Physics and Computational Mathematics Beijing100088 China

Randomized neural network (RNN) methods have been proposed for solving various partial differential equations (PDEs), demonstrating high accuracy and efficiency. However, initializing the fixed parameters remains a challenging issue. Additionally, RNNs often struggle to solve PDEs with sharp or discontinuous solutions. In this paper, we propose a novel approach called Adaptive Growing Randomized Neural Network (AG-RNN) to address these challenges. First, we establish a parameter initialization strategy based on frequency information to construct the initial RNN. After obtaining a numerical solution from this initial network, we use the residual as an error indicator. Based on the error indicator, we introduce growth strategies that expand the neural network, making it wider and deeper to improve the accuracy of the numerical solution. A key feature of AG-RNN is its adaptive strategy for determining the weights and biases of newly added neurons, enabling the network to expand in both width and depth without requiring additional training. Instead, all weights and biases are generated constructively, significantly enhancing the network’s approximation capabilities compared to conventional randomized neural network methods. In addition, a domain splitting strategy is introduced to handle the case of discontinuous solutions. Extensive numerical experiments are conducted to demonstrate the efficiency and accuracy of this innovative approach. Copyright © 2024, The Authors. All rights reserved.

关键词： Partial differential equations

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Theoretical and experimental advances on heat transfer and flow characteristics of metal foams

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Science China(Technological Sciences) 2020年第5期63卷 705-718页

作者： WANG Hui GUO LieJin CHEN Kang School of Environmental Science and Engineering Donghua UniversityShanghai 201620China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China Institute of Solar Engineering Technology Northwest Engineering Corporation LimitedPowerChinaXi’an 710065China

Open cell metal foam can be applied to greatly improve thermal performance of heat sink and heat exchanger,so that it has been widely used in the fields of thermal(or heat)control system of aerospace vehicle and energy utilization system and become a very important topic for research in the aerospace thermophysics field,and more and more attentions have been *** optimal design of metal foam heat transfer devices is based on the understanding the flow and heat transfer characteristics in metal *** article reviews some recent progresses of theoretical and experimental researches on heat transfer enhancement and flow characteristics of metal *** found that the pore cell simplification models of metal foams generally fall into four categories,among which the most commonly used cell model is Kelivin *** exploratory works performed by the current authors are also introduced,such as the effect of boundary conditions on the heat transfer enhancement;the theoretical modelling of interfacial convective heat transfer taking into account heat conduction between foam ligaments;and the flow characteristics under relatively high *** analytical results show that the flow characteristics of metal foam at relatively high speed are completely different from those at low speed,a further thorough study of the heat transfer and flow characteristics of metal foam is necessarily *** this paper,two types of partial filling techniques are *** heat transfer performance of partially filled tubes was evaluated by both the performance evaluation criteria and the performance evaluation plot of enhanced heat transfer techniques oriented for *** results show that the filling type of metal foam have a significant impact on its heat transfer enhancement ***,the filling method of metal foam should be further studied,in order to optimize the thermophysical properties of heat transfer devices.

关键词： metal foam effective thermal conductivity interfacial convective heat transfer coefficient heat transfer enhancement thermal radiation

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Optimization of Single-Hole Fender Design for Offshore Wind Turbine Foundation Under Ship Collision

SSRN

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SSRN 2023年

作者： Wang, Yujin Li, Chun Yue, Minnan Liu, Qingsong Sun, Kang Yue, Xinzhi Han, Zhiwei School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai China Shanghai Electric Wind Power Group Co. Ltd. Shanghai200233 China

This paper proposes a new design of protective fender for offshore wind turbine foundations based on nonlinear dynamics theory. The traditional anti-collision design for marine engineering platforms is not well-suited to wind turbine foundations, so the study uses the internal dynamics method and LS-DYNA to simulate the collision between a tripod foundation fender and a ship. The study analyzes impact force, energy absorption, stress, strain, and acceleration of the wind turbine tower top using finite element simulations under 19 relative hole angles. Results indicate that the optimal anti-collision protection is achieved with a hole angle of 20°. The study also examines the dynamic response and acceleration of the fender under different hole outer diameters of 0.5 m, 0.6 m, and 0.7 m and finds that the fender with a 0.7 m outer diameter exhibits the best anti-collision characteristics. The study utilizes a Kriging approximation model and a multi-objective genetic optimization algorithm to optimize the single-hole fender's design for minimum collision force and maximum energy absorption. The optimal parameter configuration has an inner hole diameter size of 0.658 m and a relative angle of 0.22°, achieving the best fender collision resistance ability. © 2023, The Authors. All rights reserved.

关键词： Offshore wind turbines

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Inverse Analysis of Radiative Properties of Internal Medium and Surface for Cylindrical System Using Csm-Cgm Approach

SSRN

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SSRN 2023年

作者： Zhang, Chao Li, Ben-Wen Zhou, Rui-Rui Li, Pan-Xin Huang, Ling-Yun Key Laboratory of Ocean Energy Utilization and Energy Conservation Ministry of Education School of Energy and Power Engineering Dalian University of Technology Dalian116024 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization Faculty of Land Resource Engineering Kunming University of Science and Technology Kunming650093 China

An inverse analysis is conducted to simultaneously estimate the radiative properties in a 2D cylindrical system including the extinction coefficient, scattering albedo, and the wall emissivity from the knowledge of the radiative heat flux over different boundaries. In which the collocation spectral method (CSM) is developed to solve the forward problem, the conjugate gradient method (CGM) is employed to solve the inverse problem, and the complex-variable-differentiation method is used to treat the sensitivity problem, separately. Meanwhile, the effects of measurement errors, initial values, and imaginary values of complex variables on the precision of the inverse analysis are investigated. Results show that the proposed inverse analysis can successfully retrieve the unknown radiative physical properties of 2D cylindrical system. Under the same physical properties, good inversion results can be obtained by using different wall (end walls and side wall) radiative heat fluxes, but the inversion efficiency from sidewall radiative heat flux is higher. Besides, it is found that, the inversion for the scattered participating medium is more efficient than that for the non-scattered participating medium;the true values and iterative convergence values have little effect on the inversion result;the influence of the initial values and the imaginary values of the complex variable on the inversion cannot be ignored. © 2023, The Authors. All rights reserved.

关键词： Conjugate gradient method

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Numerical Simulation for Non-Uniform Ptco Catalyst Degradation Under Constant Voltage Condition and its Impact on Pemfc Performance

SSRN

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SSRN 2023年

作者： Yang, Yunjie Bai, Minli Zhou, Zhifu Wu, Wei-Tao Hu, Chengzhi Gao, Linsong Li, Yang Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116023 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China

PtCo alloys are commonly utilized as catalysts in proton exchange membrane fuel cell (PEMFC) to reduce Pt loading and to achieve higher oxygen reduction reaction (ORR) activity. However, long-time operation can result in a reduction in electrochemical surface area (ECSA) in PEMFC. Meanwhile, the dissolved Co2+ may also contribute to additional local oxygen transport resistance. In this study, catalyst aging model and Co2+ transport and its effect on oxygen transport model have been integrated with the 3D single phase PEMFC performance model to develop a long-term performance model for investigating the impact of non-uniform catalyst degradation and Co2+ contamination on PEMFC performance during constant voltage operation. The results show that Co2+ contamination causes additional mass transfer losses and reduces the peak power of PEMFC. And it is found that the non-uniform degradation of catalyst and Co2+ contamination eventually affects the current density distribution in aged PEMFCs. In addition, the model is also applied to study a 50 cm2 PEMFC under long time constant voltage operation. The predicted ECSA loss is 73.1% and 62.0%, and output power reduction is 55.9% and 43.0% after 80,000 hours at a constant voltage of 0.75 V and 0.65 V, respectively. © 2023, The Authors. All rights reserved.

关键词： Numerical models

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A review on thermal application of metal foam

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Science China(Technological Sciences) 2020年第12期63卷 2469-2490页

作者： CHEN Kang GUO LieJin WANG Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China Institute of Solar Engineering Technology Northwest Engineering Corporation LimitedPowerChinaXi’an 710065China School of Environmental Science and Engineering Donghua UniversityShanghai 201620China

Heat exchangers embedded with metal foam are drawing increasing attention in the thermal application field,due to the performance of low density,large ratio of surface area to volume as well as high thermal conductivity. In these applications,compact heat exchanger,solar thermal facilities and thermal energy storage are the three core components. This paper focuses on the lasted advances in thermal applications,presenting a review of theoretical and experimental progress over metal foam in thermal application. The empirical and theoretical models for pressure drop,heat transfer coefficient and performance evaluation criteria of compact heat exchangers with metal foam are reviewed and discussed,especially different optimized *** is a trade-off between heat transfer enhancement and increase of pressure drop. Some exploratory work performed by present authors are also introduced. The manufacturing,heat transfer and flow characteristics of tube bundle wrapped with metal foam are taken into account for optimization of heat exchanger. It is confirmed that the conversion mechanism of heat transfer is carried out that heat conduction is the dominative term at high dimension permeability. The correlations of heat transfer rate and pressure drop for staggered and single row tube bundle wrapped with metal foam are concluded,respectively. The effects of different bonding methods are revealed for point-contact in metal foam and base tube. The powder-sintering method can provide a stable and minimum-thickness bonding layer. Various types of solar thermal facilities utilized metal foam to improve the energy conversion efficiency from solar radiant energy to thermal energy are also reviewed and discussed,including solar collector for intermediate-low temperature utilization and solar receiver for high temperature utilization. The Last but not least,existing and future metal foam thermal application stations are overviewed.

关键词： metal foam heat transfer enhancement solar thermal facilities thermal energy storage

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Effect of 2,5-dimethylfuran addition on ignition delay times of n-heptane at high temperatures

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Frontiers in Energy 2019年第3期13卷 464-473页

作者： Zhenhua GAO Erjiang HU Zhaohua XU Geyuan YIN Zuohua HUANG State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

The shock tube autoignition of 2,5-dimethylfuran (DMF)/n-heptane blends (DMF)/n-100%, by mole fraction) with equivalence ratios of 0.5, 1.0, and 2.0 over the temperature range of 1200-1800 K and pressures of 2.0 atm and 10.0 atm were investigated. A detailed blend chemical kinetic model resulting from the merging of validated kinetic models for the components of the fuel blends was developed. The experimental observations indicate that the ignition delay times nonlinearly increase with an increase in the DMF addition level. Chemical kinetic analysis including radical pool analysis and flux analysis were conducted to explain the DMF addition effects. The kinetic analysis shows that at lower DMF blending levels, the two fuels have negligible impacts on the consumption pathways of each *** the DMF addition increases to relatively higher levels, the consumption path of n-heptane is significantly changed due to the competition of small radicals, which primarily leads to the nonlinear increase in the ignition delay times of DMF/n-heptane blends.

关键词： ignition delay time shock tube kinetic model 2,5-dimethylfuran (DMF) n-heptane

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Thermal-Hydraulic Characteristics of Helical Cruciform Single Rod Based on Cfd Investigation

SSRN

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SSRN 2024年

作者： Chen, Yiwen Zhang, Dalin Jiang, Dianqiang Deng, Jian Zhang, Xisi Wang, Xinan Tian, Wenxi Qiu, Suizheng Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China Nuclear Power Institute of China 328 Changshun Avenue Chengdu610213 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China China Institute of Atomic Energy Beijing611731 China

To increase power density in nuclear reactors, the helical cruciform fuel (HCF) is designed as a fundamental element. HCF takes advantages of strong mixing effects, self-supporting features, and strengthened heat transfer, potential to increase the fuel performance in nuclear reactors. In this paper, friction factor and heat transfer coefficient empirical correlations of HCF single rod cooled by water were proposed using a geometric dimensionless number based on numerical simulation. The velocity field, and temperature distribution were obtained to discuss influences of geometric sizes on the fuel performance. Finally, correlations with a geometric dimensionless number were validated with various cases, whose application conditions were also proposed and discussed. This paper provides a guide for study of heat transfer and fluid flow in helical structures, and a reference for establishment of reactor system model using helical cruciform fuels. © 2024, The Authors. All rights reserved.

关键词： Heat transfer coefficients

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Synthesis of Co3o4@C/Ti3c2tx Mxene-Type Composites for Enhanced Electromagnetic Wave Absorption

SSRN

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SSRN 2024年

作者： Hou, Yunxi Jia, Zhen Zheng, Hanli Hu, Zewei Shen, Lu Liu, Dongyu Li, Lu Liu, Shiwei Liu, Yue Yu, Shitao Key Laboratory of Multiphase Flow Reaction and Separation Engineering of Shandong Province State Key Laboratory Base of Eco-chemical Engineering College of Chemical Engineering Qingdao University of Science and Technology Qingdao266042 China A VIC Research Institute for Special Structures of Aeronautical Composites 19 Jiqi Road Jinan250000 China

Highly efficient microwave absorbing materials have attracted widespread attention due to the harmful effects of electromagnetic pollution on the human body and electronic equipment. In this paper, Co3O4@C composites with core-shell structure were prepared by hydrothermal method using a simple strategy, and then Ti3C2Tx was assembled with core-shell Co3O4@C by electrostatic self-assembly method, which resulted in the successful attachment of Co3O4@C to the lamellar structure of Ti3C2Tx and the formation of MXene-based composite wave-absorbing Co3O4@C/Ti3C2Tx material. The composites exhibit strong electromagnetic wave absorption when the mass ratio of Co3O4@C to Ti3C2Tx was 1:2, with a minimum reflection loss of -35.2 dB at a matched thickness of only 4.5 mm. Excellent electromagnetic wave absorption performance Co3O4@C/Ti3C2Tx composite material was mainly attributed to the synergistic effect of the multiple reflection absorption of the core-shell structure and the high conductivity and large specific surface area of MXene material. These results indicate that Co3O4@C/Ti3C2Tx composites were promising candidates for electromagnetic absorption and provide new ideas for the design of MXene-based magnetic absorption materials. © 2024, The Authors. All rights reserved.

关键词： Composite materials

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