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Numerical and experimental investigation into the evolution of the shock wave when a muzzle jet impacts a constrained moving body

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Defence technology（防务技术） 2024年第3期33卷 317-326页

作者： Zijie Li Hao Wang Changshun Chen Kun Jiang School of energy and Power Engineering Nanjing University of Science and TechnologyNanjing 210016China

The gun-track launch system is a new special launch device that connects the track outside the *** it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle ***,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of *** this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving *** designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving *** also considered models without a constrained track for the sake of *** results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the *** the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric *** in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been *** results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving *** work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch *** also sheds light on the

关键词： Shock wave/vortex interference Muzzle jet Constrained boundary Dynamic grid

A comprehensive review of recent advancements and developments in heat exchanger network synthesis techniques

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Science China(Technological Sciences) 2024年第2期67卷 335-356页

作者： XU Yue LIU WeiWei ZHANG Lu CUI Guo Min XIAO Yuan ZHANG GuanHua YANG QiGuo School of energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China

The rapid development of computational technology and the increasing energy demand have improved heat exchanger network(HEN)*** HEN synthesis involves several optimizations of matches,distributions of heat loads,and stream splitting of heat ***,obtaining good results at high efficiency has been the main standard for evaluating the techniques in the research area of HEN *** paper first summarizes and analyzes the main contributions of the existing HEN synthesis *** compare related data quantitively,information on ten typical cases is presented in this ***,recently improved solutions for commonly encountered existing literature cases demonstrate the evolution and competition trends in the field of HEN *** comparison data presented in this paper not only provide a useful reference for future research but also present the optimization *** on the findings of this study,it is noted that there is still a large room for improvement,and current approaches are incapable of dealing with all HEN ***,it is still difficult to escape a local optimum and overcome structural constraints when seeking the global *** a follow-up to the current work,the parallel computing mode and adaptively coordinating the ratio of global and local searching abilities are major development trends for future investigation.

关键词： heat integration heat exchanger network synthesis sequential synthesis method simultaneous synthesis method optimization techniques development optimization quality

Magnetic NiFe_(2)O_(4)@FeNi_(3)core-shell nanospheres derived from FeNi-LDH precursor anchoring on rGO nanosheets for enhanced electromagnetic wave absorption

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Journal of Materials Science & technology 2024年第4期171卷 101-114页

作者： Kunyao Cao Yuan Fang Shuai Wang Yue Zhang Jiayue Wen Jun Chen Rui Zhao Weidong Xue School of Materials and energy University of Electronic Science and Technology of ChinaChengdu 610054China

Graphene has been extensively utilized in the domain of electromagnetic wave(EMW)absorption ma-terials because of its excellent electrical ***,the inferior impedance matching per-formance and the single loss mechanism vastly restrict the ***,it’s an effective strat-egy to solve these issues by introducing magnetic ***,layer double hydroxide(LDH)is an appropriate template to obtain magnetic component *** that ferromagnetic met-als such as Fe,Co,Ni,and their corresponding metal oxides are usually treated as magnetic compo-nents which are promising candidates for EMW absorption ***,in this work,a FeNi-layered double hydroxide-reduced graphene oxide(FeNi-LDH-rGO)aerogel was synthesized through a series of processes such as electrostatic self-assembly,hydrothermal,freeze-drying,and *** magnetic NiFe_(2)O_(4)@FeNi_(3)core-shell nanospheres were obtained from FeNi-LDH precursor,anchoring on rGO nanosheets after the annealing ***,the effects of different mass ratios of LDH to GO as well as different annealing temperatures of LDH-rGO aerogel on the EMW absorption prop-erty and impedance matching performance were *** a consequence,the fabricated ultralight 600LDH-rGO 2:1 aerogel shows a broad effective absorption bandwidth(EAB)of 7.04 GHz at a thickness of 2.3 mm with a low filling content of only 6 wt%and a low density of 4.4 mg/cm^(3).In conclusion,the synthetic LDH-rGO aerogels offer an effective strategy for preparing EMW absorption materials that own three-dimensional porous network structure and unique magnetic NiFe_(2)O_(4)@FeNi_(3)core-shell struc-ture nanospheres.

关键词： Electrostatic self-assembly Electromagnetic wave absorption LDH-rGO aerogel Layered double hydroxide Reduced graphene oxide NiFe_(2)O_(4)@FeNi_(3)core-shell structure

Effects of Additives on the Microstructure and Tribology Performance of Ta-12W Alloy Micro-Arc Oxidation Coating

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Journal of Wuhan University of technology(Materials Science) 2024年第1期39卷 142-149页

作者：刘玲 HU Changgang CHENG Wendong 刘兴泉 School of Materials and energy University of Electronic Science and Technology of ChinaChengdu 610054China

Oxide ceramic coatings were fabricated on tantalum alloys by micro-arc oxidation (MAO) to improve their hardness and tribological properties. The MAO coatings were manufactured in a mixed silicatephosphate electrolyte containing NaF and/or EDTA (ethylene diamine tetraacetic acid). The surface morphology,cross-sectional view, chemical composition, hardness, and wear performance of the coatings were analysed. As revealed by the scanning electron microscopy, silica-rich nodules appear on the MAO coating obtained in the silicate-phosphate electrolyte, but the formation of nodules is inhibited with NaF and/or EDTA in the ***, they reduce the roughness and improve the compactness of the coatings, which are composed of Ta_(2)O_(5),(Ta, O), and TaO. A thick and hard coating is obtained in the NaF-containing electrolyte, and the tribology performance is effectively improved. With additives, the nodule structure is detached from the coating surface and dissolved in the electrolyte. By using NaF as an electrolyte additive, the abrasion performance of the MAO coating is enhanced by decreasing the nodule structure, increasing the size of micropores, and improving the coating hardness.

关键词： micro-arc oxidation tantalum alloy additives tribology performance

A novel distributed solar refrigeration system based on evacuated U-tube solar collector and elastocaloric refrigerator

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Science China(Technological Sciences) 2024年第9期67卷 2797-2810页

作者： LI Hao ZHANG HouCheng College of New energy Ningbo University of TechnologyNingbo 315211China

Refrigeration challenges in regions with electricity shortages significantly decrease the quality of life for residents. In response to the prevalent refrigeration challenges in power-deficient areas, a novel distributed solar refrigeration system, comprising an evacuated U-tube solar collector and elastocaloric refrigerator, is theoretically introduced. Theoretical formulations for the energy efficiency and cooling power of the solar refrigeration system are presented to facilitate predictive assessments of the performance properties. Under typical conditions, the energy efficiency and cooling power of the solar refrigeration system are,respectively, 4.84% and 200.15 W. Subsequently, an extensive parameter study is conducted to comprehensively uncover key performance influencers and identify avenues for improvement. In addition, local sensitivity analyses identify that the length ratio is the top influential parameter, while the heat transfer fluid flow rate is the least sensitivity. A pragmatic case study,conducted with the weather data of Ningbo City, China, serves to empirically predict the performance of the hybrid system within the constraints of practical circumstances.

关键词： evacuated U-tube solar collector elastocaloric refrigerator solar refrigeration solar energy thermal utilization system integration

A novel approach towards the selection of regenerators for optimal Stirling engine performance based on energy and exergy analyses

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Science China(Technological Sciences) 2024年第1期67卷 295-310页

作者： YU MinJie ZHANG MingHui XU Lei CUI HaiChuan LIU ZhiChun LIU Wei School of energy and Power Engineering Huazhong University of Science and TechnologyWuhan 430074China

Regenerators play a vital role in enhancing the overall performance of Stirling ***,this paper performed an energy and exergy analysis to elucidate the significance of regenerator characteristics concerning system performance,contributing to the optimal regenerator’s design and *** relationship between regenerator structure,regenerator exergy destruction,and output power,thermal efficiency,and exergy efficiency for Stirling engines was established by integrating the thermal model of Stirling engines with a mathematical model of *** contrast to cross-flow and parallel-flow regenerators,a novel concept of inclined-flow regenerators,featuring a matrix surface inclined in the direction of gas flow,was developed to achieve higher and more balanced engine output power and energy utilization efficiency.A comprehensive investigation was conducted into the effects of matrix structure types and regenerator geometries on the performance of both regenerators and *** results reveal that,following structural optimization,Stirling engines equipped with the inclined-flow regenerator demonstrate a substantial 16.6%,38.3%,and 37.2%increase in power output,thermal efficiency,and exergy efficiency,respectively,compared to those equipped with cross-flow *** contrast,when compared to engines fitted with parallel-flow regenerators,they experience a 13.5%reduction in power output but achieve remarkable enhancements of 45.4%and 36.7%in thermal and exergy efficiency,*** study introduces new insights into selecting regenerator structures for enhancing the output performance of Stirling engines.

关键词： Stirling engine inclined-flow regenerator adiabatic model exergy analysis

Super P and MoO2/MoS2 co-doped gradient nanofiber membrane as multi-functional separator for lithium–sulfur batteries

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Rare Metals 2024年第9期43卷 4263-4273页

作者： Xin Liang Dong-Qing Zhao Qian-Qian Huang Sheng Liang Li-Li Wang Lei Hu Ling-Li Liu Kun-Hong Hu Chong-Hai Deng Sheng Cheng Er-Tao Zhu Hua-Xia Deng School of energy Materials and Chemical Engineering LIB Technology Center of Anhui ProvinceHefei University Instrumental Analysis Centre Hefei University of Technology Hefei Youngy energy Materials Co. Ltd. Department of Modern Mechanics University of Science and Technology of China

Lithium-sulfur battery is one of the most promising battery systems for industrialization due to its high theoretical specific capacity and high energy ***,the??shuttle effect??has restrained the advancement of lithium-sulfur *** this work,a gradient-structured nanofiber membrane with pure gelatin on one side and Super P-MoO2/MoS2-gelatin on the other side was created using a multi-step electrostatic spinning technique,which was applied for multi-functional separator for lithium-sulfur *** pure gelatin layer facing the anode side primarily homogenizes the lithium flux,whereas the Super P-MoO2/MoS2-gelatin layer facing the cathode side primarily adsorbs polysulfides by physical and chemical adsorption and enhancing polysulfide conversion *** findings demonstrate that even after 150 cycles at 0.2C,the lithium-sulfur battery can still sustain a discharge-specific capacity of 572.3 mAh·*** used with Li||Li symmetric batteries,it has a cycle life of more than 1200 *** commercialization of lithium-sulfur batteries is given a fresh idea by this straightforward preparation technique.

关键词： Li–S battery Membrane MoO2/MoS2 Nanofiber

New approach for particle size and shape analysis of iron-based oxygen carriers at multiple oxidation states

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Particuology 2024年第7期90卷 493-503页

作者： Victor Purnomo Marcelo Dal Belo Takehara Robin Faust Lidiya Abdisa Ejjeta Henrik Leion Division of energy and Materials Department of Chemistry and Chemical EngineeringChalmers University of TechnologyGöteborg 41258Sweden Division of energy Science Department of Engineering Sciences and MathematicsLuleåUniversity of TechnologyLuleå97187Sweden

One of the crucial issues in the chemical looping technology lies in its bed material:the oxygen *** size analysis of an oxygen carrier is important since in a fluidized bed the material can only work well within a specific size *** the favorable size ranges for oxygen carrier materials have already been reported,none of the published studies has analyzed the particle size and shape of oxygen carriers in ***,the effect of oxygen carriers'oxidation degree on such properties has not been considered *** study aimed to report the particle size and shape analysis of five iron-based oxygen carriers,one natural ore,one synthetic material,and three residue products,at different oxidation degrees using dynamic image analysis(DIA).The oxygen carriers were prepared at different mass conversion degrees in a fluidized bed batch *** size distribution,sphericity,and aspect ratio of the oxygen carrier particles were examined experimentally using a Camsizer *** results show that the DIA method was successfully able to analyze the particle size and shape of our oxygen carriers with satisfying accuracy for *** oxidation state of the investigated materials seems to only affect the particle size and shape of oxygen carriers to a minor ***,exposures to redox cycles in a fluidized bed reactor may alter the particle size and shape of most oxygen carriers.

关键词： Oxygen carrier Size and shape analysis Dynamic image analysis Oxidation state Fluidized bed Chemical looping

Visualisation and Heat Transfer Performance of Mini-Channel Flat Heat Pipe with a Binary Mixture

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Journal of Thermal Science 2024年第5期33卷 1712-1725页

作者： FAN Gaoting TANG Aikun CAI Tao SHAN Chunxian PAN Jun JIN Yi School of energy and Power Engineering Jiangsu UniversityZhenjiang 212013China Jiangsu Jinhe energy technology Co.Ltd Zhenjiang 212400China

To unravel the intricacies of two-phase gas-liquid flow characteristics and heat transfer behavior,an array mini-channel gravity plate heat pipe(AMGPHP)is proposed in this work,which allows for observing the internal changes in the state of the working *** flow patterns such as pool flow,columnar flow,and slug flow,are experimentally explored and analyzed in *** is found that the optimal volume fill ratio is 20%by utilizing start-up time and thermal resistance as performance evaluation *** this fill ratio,a medium optimization strategy by blending ethanol within R141b is proposed and *** comparison to pure working fluids,the heat transfer performance of AMGFHP in the binary fluid has been significantly augmented due to temperature and concentration shifts resulting from disparate boiling *** the 10%volume fraction ethanol blending condition,the equivalent thermal conductivity of the heat pipe is dramatically elevated,with a value of 3110 W/(m·℃),along with the reduction of the minimum start-up power to 4 *** general,applying such a medium to heat pipes has considerable potential in practical applications.

关键词： flat heat pipe mini-channel visualisation two-phase flow binary mixtures thermal performance