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Isotopic dependence of the yield ratios of light fragments from different projectiles and their unified neutron skin thicknesses

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Nuclear Science and Techniques 2024年第3期35卷 228-236页

作者： Ting-Zhi Yan Shan Li school of energy and power engineering Northeast Electric Power UniversityJilin 132012China

The yield ratios of neutron-proton(R(n/p))and^(3)H-^(3)He(R(^(3)H∕^(3)He))with reduced rapidity from 0 to 0.5 were simulated at 50 MeV/u even-even ^(36−56)Ca+^(40)Ca,even-even ^(48−78)Ni+^(58)Ni,and ^(100−139)Sn(every third isotopes)+112 Sn for full reduced impact parameters using the isospin-dependent quantum molecular dynamics(IQMD)model.The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model,which was used for the phase space initialization of the projectile and target in IQMD.We defined the unified neutron skin thickness asΔRnp=^(1∕2) n−^(1∕2)p,which was negative for neutron-deficient nuclei.The unifiedΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal,except for extreme neutron-rich isotopes,which is a type of scaling behavior.The yield ratios of the three isotopic chain-induced reactions,which depended on the reduced impact parameter and unified neutron skin thickness,were studied.The results showed that both R(n/p)and R(^(3)H∕^(3)He)decreased with a reduced impact parameter for extreme neutron-deficient isotopes;however,they increased with reduced impact parameters for extreme neutron-rich isotopes,and increased with theΔRnp of the projectiles for all reduced impact parameters.In addition,a scaling phenomenon was observed betweenΔR np and the yield ratios in peripheral colli-sions from different isotopic chain projectiles(except for extreme neutron-rich isotopes).Thus,R(n/p)and R(^(3)H∕^(3)He)from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.

关键词： Exotic nuclei Unified neutron skin thickness Yield ratios IQMD

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Performance analysis and multi-objective optimization based on a modified irreversible Stirling cycle

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Science China Technological Sciences 2024年第6期67卷 1668-1684页

作者： XU Lei YU MinJie LIU ZhiChun LIU Wei school of energy and power engineering Huazhong University of Science and Technology

The efficiency of the actual Stirling engine is much lower than the ideal Carnot cycle efficiency. To obtain more precise efficiency for Stirling engines, this paper proposes a modified Stirling cycle with a more accurate heat transfer process in Stirling engines based on a thermodynamic function called available potential. The finite-time thermodynamic method is used to analyze the model performance under constant heat source temperature, finite temperature difference heat transfer, and incomplete regenerative processes. A new polytropic process is introduced to model the heat transfer between the working fluid and external heat sources in which only heat above ambient temperature is converted into technical work. The regenerator is divided into numerous smaller heat reservoirs with individual temperature to analyze the incomplete regenerative processes. The expressions of the output power and thermal efficiency are obtained based on the modified irreversible Stirling cycle, and the effects of irreversible losses are analyzed to evaluate the performance of the proposed model. Results indicate that the efficiency of the modified cycle is much lower than that of the ideal Stirling cycle with an isothermal process. With the increase of the average heat transfer temperature difference, there exists an optimum value for the power of the irreversible cycle. The optimum power of the model was obtained for varying thermodynamic parameters by optimizing the average heat transfer temperature difference between the hot and cold sides. To optimize the irreversible model, the multi-objective optimization analysis is carried out based on NSGA-Ⅱ, which results in an optimized output power of 40.87 kW and an optimized thermal efficiency of 44%.

关键词： stirling cycle regenerative processes isopotential processes multi-objective optimization finite time thermodynamics

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An uncertainty investigation for liner impedance eduction methods

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Chinese Journal of Aeronautics 2024年第3期37卷 49-59页

作者： Weihao SHI Xiaodong JING school of energy and power engineering Beihang UniversityBeijing 100191China

Impedance eduction methods have been developed for decades to meet the increasing need for high-quality impedance data in the design and optimization of acoustic liners.To this end,it is important to fully investigate the uncertainty problem,to which only limited attention has been devoted so far.This paper considers the possibility of acoustically-induced structural vibration as a nonnegligible uncertainty or error source in impedance eduction experiments.As the frequency moves away from the resonant frequency,with the increase in the value of cavity reactance,the acoustic particle velocity inside liner orifices possibly decreases to the extent comparable to the vibration velocity of liner facing sheet.Thus,the acoustically-induced vibration,although generally being weak except at the inherent structural frequencies,may considerably affect the impedance eduction results near the anti-resonant frequency where the liner has poor absorption.To demonstrate the effect of structural vibration,the vibration velocity of liner facing sheet is estimated from the experimentally educed admittance of the liner samples whose orifices are sealed with tape.Further,a three-dimensional numerical model is set up,in which normal particle velocity is introduced over the solid portion of liner facing sheet to imitate structural vibration,rather than directly solving the acoustic-structural coupling problem.As shown by the results,the vibration of liner facing sheet,whose velocity is as small as estimated by the experiment,can result in anomalous deviation of the educed impedance from the impedance model near the anti-resonant frequency.The trend that the anomalous deviation varies with frequency is numerically captured.

关键词： Impedance eduction Uncertainty analysis Acoustically-induced structural vibration Anti-resonant frequency Perforated liner

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Thermodynamic and Economic Analysis of a Conceptual System Combining Sludge Gasification,SOFC,Supercritical CO2 Cycle,and Organic Rankine Cycle

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Journal of Thermal Science 2024年第4期33卷 1491-1508页

作者： LV Jiayang WANG Chizhong CHEN Heng PAN Peiyuan XU Gang ZHANG Guoqiang school of energy Power and Mechanical EngineeringNorth China Electric Power University

In order to reduce the environmental impact of conventional sludge treatment methods and to utilize the energy in sludge more effectively,a coupled system based on sewage sludge gasifier（SSG）,solid oxide fuel cells（SOFC）,supercritical CO2cycle（S-CO2）,and organic Rankine cycle（ORC） is proposed.The clean syngas obtained from sludge gasification is mixed with CH4 and then first utilized by the fuel cell.The exhaust gas from the fuel cell is fully combusted in the afterburning chamber and then enters the bottom cycle system consisting of S-CO2& ORC to generate electricity.To understand the performance of the system,thermodynamic and economic analyses were conducted to examine the project's performance.The thermodynamics as well as the economics of the coupled system were analyzed to arrive at the following conclusions,the power production of the system is 37.34 MW;the exergy efficiency is 55.62%,and the net electrical efficiency is 61.48%.The main exergy destruction is the gasifier and SOFC,accounting for 62.45% of the total exergy destruction.It takes only6.13 years to repay the construction investment in the novel system,and the project obtains a NPV of 17 723 820USD during 20 years lifetime.The above findings indicate that the new coupled system has a better performance in terms of energy utilization and economy.

关键词： sewage sludge gasifier SOFC supercritical CO 2 cycle organic Rankine cycle multi-system coupling

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Peak Shaving Strategy of Concentrating Solar power Generation Based on Multi-Time-Scale and Considering Demand Response

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energy engineering 2024年第3期121卷 661-679页

作者： Lei Fang Haiying Dong Xiaofei Zhen Shuaibing Li school of new energy and power engineering Lanzhou Jiaotong UniversityLanzhou730070China

According to the multi-time-scale characteristics of power generation and demand-side response(DR)resources,as well as the improvement of prediction accuracy along with the approaching operating point,a rolling peak shaving optimization model consisting of three different time scales has been proposed.The proposed peak shaving optimization model considers not only the generation resources of two different response speeds but also the two different DR resources and determines each unit combination,generation power,and demand response strategy on different time scales so as to participate in the peaking of the power system by taking full advantage of the fast response characteristics of the concentrating solar power(CSP).At the same time,in order to improve the accuracy of the scheduling results,the combination of the day-ahead peak shaving phase with scenario-based stochastic programming can further reduce the influence of wind power prediction errors on scheduling results.The testing results have shown that by optimizing the allocation of scheduling resources in each phase,it can effectively reduce the number of starts and stops of thermal power units and improve the economic efficiency of system operation.The spinning reserve capacity is reduced,and the effectiveness of the peak shaving strategy is verified.

关键词： Peak shaving strategy concentrating solar power multi-time-scale demand-side response rolling optimization

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Numerical Analysis of Heat Transfer Characteristics to Supercritical CO_(2) in a Vertical Mini-Channel:Transition and Pseudo-Boiling

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Journal of Thermal Science 2024年第1期33卷 101-113页

作者： YUAN Baoqiang WANG Wei XIN Gongming DU Wenjing school of energy and power engineering Shandong UniversityJi'nan 250061China

Large eddy simulations have been conducted to study upward transitional flows and heat transfer characteristics of supercritical CO_(2) in a vertical mini-channel.The numerical simulation was carried out on a modified buoyantPimpleFOAM solver in OpenFOAM 7,and was verified using experiment data.Numerical results indicate that increasing the Grashof numbers can reduce the flow stability and make the flow transition earlier.There are four stages of heat transfer in the transition process,i.e.,weakened,improved,recovered and normal heat transfer.These heat transfer phenomena in the transition process were explained from three perspectives:thermal boundary layer theory,turbulent transport and pseudo-boiling theory.Heat transfer enhancement during transition is related to the transport of supercritical molecular clusters,and these molecular clusters are regarded as pseudo-bubbles in pseudo-boiling theory.The flow pattern of the pseudo-phases in the dia-Widom process contains single-phase flow,steady pseudo-film flow,unsteady pseudo-film flow,partial pseudo-bubbles flow and flocculent pseudo-film flow.Pseudo-bubbles have similar behaviors to subcritical bubbles,i.e.,break-up,deformation,condensation and coalescence.Relevant researches in this work are favorable for understanding the heat transfer mechanism of supercritical fluids during flow transition.

关键词： supercritical heat transfer large eddy simulation transition pseudo-boiling

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Ionization engineering of Hydrogels Enables Highly Efficient Salt‑Impeded Solar Evaporation and Night‑Time Electricity Harvesting

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Nano-Micro Letters 2024年第1期16卷 131-146页

作者： Nan He Haonan Wang Haotian Zhang Bo Jiang Dawei Tang Lin Li school of energy and power engineering Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of EducationDalian University of TechnologyDalian 116024People’s Republic of China

Interfacial solar evaporation holds immense potential for brine desalination with low carbon footprints and high energy utilization.Hydrogels,as a tunable material platform from the molecular level to the macroscopic scale,have been considered the most promising candidate for solar evaporation.However,the simultaneous achievement of high evaporation efficiency and satisfactory tolerance to salt ions in brine remains a challenging scientific bottleneck,restricting the widespread application.Herein,we report ionization engineering,which endows polymer chains of hydrogels with electronegativity for impeding salt ions and activating water molecules,fundamentally overcoming the hydrogel salt-impeded challenge and dramatically expediting water evaporating in brine.The sodium dodecyl benzene sulfonate-modified carbon black is chosen as the solar absorbers.The hydrogel reaches a ground-breaking evaporation rate of 2.9 kg m−2 h−1 in 20 wt%brine with 95.6%efficiency under one sun irradiation,surpassing most of the reported literature.More notably,such a hydrogel-based evaporator enables extracting clean water from oversaturated salt solutions and maintains durability under different high-strength deformation or a 15-day continuous operation.Meantime,on the basis of the cation selectivity induced by the electronegativity,we first propose an all-day system that evaporates during the day and generates salinity-gradient electricity using waste-evaporated brine at night,anticipating pioneer a new opportunity for all-day resource-generating systems in fields of freshwater and electricity.

关键词： Solar evaporation Hydrogel evaporators Salt impeding Ionization engineering Cyclic vapor-electricity generation

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Insight into the selective separation of CO_(2)from biomass pyrolysis gas over metal-incorporated nitrogen-doped carbon materials:a first-principles study

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Frontiers of Chemical Science and engineering 2024年第3期18卷 1-12页

作者： Li Zhao Xinru Liu Zihao Ye Bin Hu Haoyu Wang Ji Liu Bing Zhang Qiang Lu National engineering Research Center of new energy power Generation North China Electric Power UniversityBeijing102206China

The composition of biomass pyrolysis gas is complex,and the selective separation of its components is crucial for its further utilization.Metal-incorporated nitrogen-doped materials exhibit enormous potential,whereas the relevant adsorption mechanism is still unclear.Herein,16 metal-incorporated nitrogen-doped carbon materials were designed based on the density functional theory calculation,and the adsorption mechanism of pyrolysis gas components H2,CO,CO_(2),CH_(4),and C2H6 was explored.The results indicate that metal-incorporated nitrogen-doped carbon materials generally have better adsorption effects on CO and CO_(2)than on H_(2),CH_(4),and C_(2)H_(6).Transition metal Mo-and alkaline earth metal Mg-and Ca-incorporated nitrogen-doped carbon materials show the potential to separate CO and CO_(2).The mixed adsorption results of CO_(2)and CO further indicate that when the CO_(2)ratio is significantly higher than that of CO,the saturated adsorption of CO_(2)will precede that of CO.Overall,the three metal-incorporated nitrogen-doped carbon materials can selectively separate CO_(2),and the alkaline earth metal Mg-incorporated nitrogen-doped carbon material has the best performance.This study provides theoretical guidance for the design of carbon capture materials and lays the foundation for the efficient utilization of biomass pyrolysis gas.

关键词： CO_(2)capture biomass pyrolysis gas selective adsorption carbon materials first-principles

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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 muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle jet.Specifically,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 vortices.In 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 body.We 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 body.We also considered models without a constrained track for the sake of comparison.The results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the muzzle.Because 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 characteristics.This in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been identical.The 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 body.The work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch system.It also sheds light on the technical bottlenecks that need to be considered

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

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Improved Proximal Policy Optimization Algorithm for Sequential Security-constrained Optimal power Flow Based on Expert Knowledge and Safety Layer

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Journal of Modern power Systems and Clean energy 2024年第3期12卷 742-753页

作者： Yanbo Chen Qintao Du Honghai Liu Liangcheng Cheng Muhammad Shahzad Younis State Key Laboratory of Alternate Electrical power System with Renewable energy Sources and school of Electrical & Electronic engineering North China Electric Power University school of engineering Xining University Key Laboratory of Smart Operation of new energy power System Ministry of Education Qinghai University China Electric power Research Institute National University of Sciences and Technology

In recent years, reinforcement learning(RL) has emerged as a solution for model-free dynamic programming problem that cannot be effectively solved by traditional optimization methods. It has gradually been applied in the fields such as economic dispatch of power systems due to its strong selflearning and self-optimizing capabilities. However, existing economic scheduling methods based on RL ignore security risks that the agent may bring during exploration, which poses a risk of issuing instructions that threaten the safe operation of power system. Therefore, we propose an improved proximal policy optimization algorithm for sequential security-constrained optimal power flow(SCOPF) based on expert knowledge and safety layer to determine active power dispatch strategy, voltage optimization scheme of the units, and charging/discharging dispatch of energy storage systems. The expert experience is introduced to improve the ability to enforce constraints such as power balance in training process while guiding agent to effectively improve the utilization rate of renewable energy. Additionally, to avoid line overload, we add a safety layer at the end of the policy network by introducing transmission constraints to avoid dangerous actions and tackle sequential SCOPF problem. Simulation results on an improved IEEE 118-bus system verify the effectiveness of the proposed algorithm.

关键词： Renewable energy sources Safety power systems Optimization power grids energy storage Training

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