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Analysis of application range of simplified models for field to thermo-field to thermionic emission processes from the cathode

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Plas.a.science and Technology 2024年第9期26卷 51-60页

作者： Li sUN Zhuo DAI Ming XU Wei WANG Zengyao LI Applied Physics Department Xi’an University of TechnologyXi’an 710048People’s Republic of China Key Laboratory of thermo-Fluid science and Engineering Ministry of EducationSchool of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an 710049People’s Republic of China

electron emission plays.a.dominant role in plas.a.cathode interactions.a.d is.a.key factor in many plas.a.phenomena and industrial *** is neces.a.y to illustrate the various electron emission mechanisms.a.d the corresponding applicable description models to evaluate their impacts on discharge *** this study,detailed expressions of the simplified formulas valid for field emission to thermo-field emission to thermionic emission typically used in the numerical simulation are proposed,and the corresponding application ranges.a.e determined in the framework of the Murphy-Good theory,which is commonly regarded as the general model and to be accurate in the full range of conditions of the validity of the *** parameterization was used to evaluate the emission current density of the Murphy-Good formula,and a deviation factor was defined to obtain the application ranges for different work functions(2.5‒5 eV),cathode temperatures(300‒6000 K),and emitted electric fields(10^(5) to 10^(10) V·m^(-1)).The deviation factor was shown to be a nonmonotonic function of the three parameters.a.comparative study of particle number densities in atmospheric gas discharge with a tungsten cathode was performed based on the one-dimensional implicit particle-in-cell(PIC)with the Monte Carlo collision(MCC)method according to the aforementioned application *** was found that s.a.l differences in emission current density can lead to variations in the distributions of particle number density due to changes in the collisional *** study provides.a.theoretical basis for selecting emission models for subsequent numerical simulations.

关键词： electron emission processes application range Murphy-Good theory implicit particlein-cell Monte Carlo collision method

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Abnormal transition of the electron energy distribution with excitation of the second harmonic in low-pressure radio-frequency capacitively coupled plas.a.

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Plas.a.science and Technology 2024年第8期26卷 58-63页

作者：余乐怡陆文琪张丽娜 Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024People’s Republic of China

The self-excited second harmonic in radio-frequency capacitively coupled plas.a.was significantly enhanced by adjusting the external variable *** a lower pressure of 3 Pa,the excitation of the second harmonic caused an abnormal transition of the electron energy probability function,resulting in abrupt changes in the electron density and *** changes in the electron energy probability function as well as the electron density and temperature were not observed at the higher pressure of 16 Pa under similar harmonic *** phenomena are related to the influence of the second harmonic on stochastic heating,which is determined by both amplitude and the relative phase of the *** results suggest that the self-excited high-order harmonics must be considered in practical applications of lowpressure radio-frequency capacitively coupled plas.a..

关键词： radio-frequency capacitively coupled plasma harmonics the electron energy probability function

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Effect of high-energy Ne ions irradiation on mechanical properties difference between Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5)metallic glass.a.d crys.a.line W

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Plas.a.science and Technology 2024年第6期26卷 14-21页

作者：李娜张立松张小楠宫丽悦羌建兵梅显秀 Key Laboratory of Materials Modification by Laser Ion and Electron BeamsMinistry of EducationDalian University of TechnologyDalian 116024People’s Republic of China school of science Dalian Jiaotong UniversityDalian 116028People’s Republic of China

In this paper,high-energy Ne ions were used to irradiate Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) metallic glass(MG)and crys.a.line W to investigate their difference in mechanical response after *** results showed that with the irradiation dose increased,the tensile micro-strain increased,nano-hardness increased from 7.11 GPa to 7.90 GPa and 8.62 GPa,Young’s modulus increased,and H3/E2 increased which indicating that the plastic deformability decreased in crys.a.line *** the same irradiation conditions,the Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG still maintained the amorphous structure and became more disordered despite the longer range and stronger displacement damage of Ne ions in Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG than in crys.a.line *** the irradiation hardening and embrittlement behavior of crys.a.line W,Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG showed the gradual decrease in hardness from 6.02 GPa to 5.89 GPa and 5.50 GPa,the decrease in modulus.a.d the increase in plastic deformability with the increasing ***,the irradiation softening and toughening phenomenon of Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG could provide new ideas for the design of nuclear materials.

关键词： heavy ions irradiation displacement damage metallic glass crys.a.line W mechanical property

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simulation of tungsten impurity transport by DIVIMP under different divertor magnetic configurations on HL-3

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Plas.a.science and Technology 2024年第10期26卷 29-38页

作者： Qingrui ZHOU Yanjie ZHANG Chaofeng sANG Jiaxian LI Guoyao ZHENG Yilin WANG Yihan WU Dezhen WANG Key Laboratory of Materials Modification by Laser Ion and Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024People’s Republic of China southwestern Institute of Physics Chengdu 610041People’s Republic of China

Tungsten(W)accumulation in the core,depending on W generation and transport in the edge region,is.a.severe issue in fusion *** to s.a.dard divertors(sDs),snowflake divertors(sFDs)can effectively suppress the heat flux,while the impact of magnetic configurations on W core accumulation remains *** this study,the kinetic code DIVIMP combined with the sOLPs-ITER code is.a.plied to investigate the effects of divertor magnetic configurations(sD versus sFD)on W accumulation during neon injection in *** is found that the W concentration in the core of the sFD is significantly higher than that of the sD with similar total W erosion *** reasons for this.a.e:(1)W impurities in the core of the sFD mainly originate from the inner divertor,which has.a.short leg,and the source is close to the divertor entrance and upstream ***,the W ionization source(s_(W0))is much stronger,especially near the divertor entrance.(2)The region overlap of s_(W0)and F_(W,TOT)pointing upstream promote W accumulation in the ***,the influence of W source locations.a. the inner target on W transport in the sFD is *** impurity in the core is mainly contributed by target erosion in the common flux region(CFR)away from the strike *** is.a.tributed to the fact that the W source at this location enhances the ionization source above the W ion s.a.nation point,which sequentially increases W ***,the suppression of far sOL inner target erosion can effectively prevent W impurities from accumulating in the core.

关键词： snowflake divertor neon seeding tungsten transport DIVIMP HL-3

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structure-preserving algorithms for guiding center dynamics based on the slow manifold of classical Pauli particle

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Plas.a.science and Technology 2024年第6期26卷 88-102页

作者：张若涵王正汹肖建元王丰 Key Laboratory of Materials Modification by Laser Ion and Electron BeamsSchool of PhysicsDalian University of TechnologyDalian 116024People’s Republic of China Department of Plas.a.Physics.a.d Fusion Engineering University of Science and Technology of ChinaHefei 230026People’s Republic of China

The classical Pauli particle(CPP) serves.a. a slow manifold, substituting the conventional guiding center dynamics. Based on the CPP, we utilize the averaged vector field(AVF) method in the computations of drift orbits. Demonstrating significantly higher efficiency, this.a.vanced method is capable of accomplishing the simulation in less than one-third of the time of directly computing the guiding center motion. In contrast to the CPP-based Boris.a.gorithm, this.a.proach inherits the advantages of the AVF method, yielding s.a.le trajectories even achieved with a tenfold time step and reducing the energy error by two orders of magnitude. By comparing these two CPP algorithms with the traditional RK4 method, the numerical results indicate a remarkable performance in terms of both the computational efficiency and error elimination. Moreover, we verify the properties of slow manifold integrators.a.d successfully observe the bounce on both sides of the limiting slow manifold with deliberately chosen perturbed initial conditions. To evaluate the practical value of the methods, we conduct simulations in non-axisymmetric perturbation magnetic fields.a. part of the experiments,demonstrating that our CPP-based AVF method can handle simulations under complex magnetic field configurations with high accuracy, which the CPP-based Boris.a.gorithm lacks. Through numerical experiments, we demonstrate that the CPP can replace guiding center dynamics in using energy-preserving algorithms for computations, providing a new, efficient, as well as s.a.le approach for applying structure-preserving algorithms in plas.a.simulations.

关键词： structure-preserving algorithm averaged vector field classical Pauli particle guiding center dynamics

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Diameter-dependent ultra-high thermoelectric performance of ZnO nanowires

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Chinese Physics B 2024年第4期33卷 86-94页

作者：聂祎楠唐桂华李一斐张敏赵欣 MOE Key Laboratory of thermo-Fluid science and Engineering School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an 710049China

Zinc oxide(ZnO)shows great potential in electronics,but its large intrinsic thermal conductivity limits its thermoelectric *** this work,we explore the significant carrier transport capacity and diameter-dependent thermoelectric characteristics of wurtzite-ZnO(0001)nanowires based on first-principles.a.d molecular dynamics *** the synergistic effect of band degeneracy and weak phonon-electron s.a.tering,P-type(ZnO)_(73) nanowires.a.hieve an ultrahigh power factor above 1500μW·cm^(-1)·K^(-2)over a wide temperature *** lattice thermal conductivity and carrier transport properties of ZnO nanowires exhibit a strong diameter size *** the ZnO nanowire diameter exceeds 12.72A,the carrier transport properties increase significantly,while the thermal conductivity shows.a.slight increase with the diameter size,resulting in a ZT value of up to 6.4 at 700 K for P-type(ZnO)_(73).For the first time,the size effect is.a.so illustrated by introducing two geometrical configurations of the ZnO *** work theoretically depicts the size optimization strategy for the thermoelectric conversion of ZnO nanowires.

关键词： ZnO nanowire size effect thermoelectric performance deformation potential theory

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Effect of a negative DC bias on a capacitively coupled Ar plas.a.operated at different radiofrequency voltages.a.d gas pressures

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Plas.a.science and Technology 2024年第5期26卷 62-71页

作者：相垚君王晓坤刘永新王友年 Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024People’s Republic of China Chair of Applied Electrodynamics.a.d Plas.a.Technology Ruhr University BochumBochum 44801Germany

The effect of a negative DC bias,|V_(dc)|,on the electrical parameters.a.d discharge mode is investigated experimentally in a radiofrequency(RF)capacitively coupled Ar plas.a.operated at different RF voltage amplitudes.a.d gas *** electron density is measured using a hairpin probe and the s.a.io-temporal distribution of the electron-impact excitation rate is determined by phase-resolved optical emission *** electrical parameters.a.e obtained based on the waveforms of the electrode voltage and plas.a.current measured by a voltage probe and a current *** was found that at a low|V_(dc)|,***α-mode,the electron density and RF current decline with increasing|V_(dc)|;meanwhile,the plas.a.impedance becomes more capacitive due to a widened ***,RF power deposition is ***|V_(dc)|exceeds.a.certain value,the plas.a.changes toα–γhybrid mode(or the discharge becomes dominated by theγ-mode),manifesting a drastically growing electron density and a moderately increasing RF ***,the plas.a.impedance becomes more resistive,so RF power deposition is enhanced with|V_(dc)|.We also found that the electrical parameters show similar dependence on|V_(dc)|at different RF voltages.a.dα–γmode transition occurs.a. a lower|V_(dc)|at a higher RF *** increasing the pressure,plas.a.impedance becomes more resistive,so RF power deposition and electron density are *** particular,theα–γmode transition tends to occur at a lower|V_(dc)|with increase in pressure.

关键词： RF capacitively coupled plasma DC-overlapped RF discharge power deposition discharge mode transition

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Time-resolved characteristics of a nanosecond pulsed multi-hollow needle plate packed bed dielectric barrier discharge

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Plas.a.science and Technology 2024年第7期26卷 48-57页

作者：秦亮李瑶郭浩姜楠宋颖贾锐周雄峰袁皓杨德正 Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Dalian University of Technology)Ministry of EducationDalian 116024People’s Republic of China school of Electrical Engineering Dalian University of TechnologyDalian 116024People’s Republic of China s.a.e Key Laboratory of Complex Electromagnetic Environment Effects on electronics.a.d Information system Luoyang 471003People’s Republic of China school of Physics.a.d Materials Engineering Dalian Minzu UniversityDalian 116600People’s Republic of China

In this paper,self-designed multi-hollow needle electrodes.a.e used as.a.high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume s.a.le *** dynamic characteristics of the plas.a.the generated active species.a.d the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images.a.d time-resolved optical emission *** experimental results show that the discharge intensity,number of discharge channels.a.d discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle *** a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in *** PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a s.a.ding filamentary micro-discharge,which allows the plas.a.to leave the local area and is conducive to the propagation of surface *** ND,the discharge only appears.a. a diffusionlike mode between the gap of dielectric beads,regardless of whether there is.a.discharge ***,the generation of excited s.a.es N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is.a.tributed to the higher E/N in PD than that in ***,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in *** is not directly dominated by E/N,but mainly by the resonant energy transfer process between metas.a.le N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.

关键词： packed bed reactor multi-hollow needle electrodes positive and negative discharges optical emission spectra time-resolved images

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Comparison of Direct Pore-s.a.e and Volume-Averaging Methods for the Performance Evaluation of Porous Volumetric solar Receiver

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Journal of Thermal science 2024年第5期33卷 1607-1617页

作者： DU shen HE Yaling LI Dong LIU Zhanbin LI Mengjie National Innovation Platform(Center)for Industry-Education Integration of Energy storage Technology Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of EducationXi’an Jiaotong UniversityXi’an710049China

Direct pore-s.a.e and volume-averaging numerical simulations.a.e two methods for investigating the performance of porous volumetric solar *** clarify the difference in the prediction of heat transfer processes.a.direct comparison between these two methods was conducted at both steady s.a.e and transient *** numerical models were es.a.lished based on X-ray computed tomography s.a.s.a.d a local thermal non-equilibrium model,*** empirical parameters,which are indispensable to the volume-averaging simulation,were determined by Monte Carlo ray tracing and direct pore-s.a.e numerical *** predicted outlet air temperature of the receiver by the volume-averaging simulation method corresponded satis.a.torily to that in the direct pore-s.a.e *** largest discrepancies were observed when the receiver's working temperature was elevated,with differences of 5.5%and 3.68%for the steady s.a.e and transient s.a.e simulations,***,the volume-averaging method is incapable of capturing the local temperature information of the air and porous *** underestimates the inlet temperature of the receiver,leading to an overestimation of the receiver's thermal efficiency,with the largest difference being 6.51%.The comparison results show that the volume-averaging model is.a.good approximation to the pore-s.a.e model when the empirical parameters.a.e carefully selected.

关键词： porous media volumetric solar receiver pore-s.a.e method volume-averaging method thermal performance

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Heat Transfer and Friction Characteristics of Printed Circuit Heat Exchangers with Different Channel structures for s-CO_(2) Power system

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Journal of Thermal science 2024年第3期33卷 1132-1147页

作者： JIANG Tao LI Mingjia Key Laboratory of thermo-Fluid science and Engineering of Ministry of Education School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an710049China school of Mechanical Engineering Beijing Institute of TechnologyBeijing100081China

Printed circuit heat exchanger(PCHE)has been widely used in supercritical carbon dioxide(s-CO_(2))power systems because of its high heat transfer efficiency and good ***,due to the large variety of PCHE configurations,channel selection in practical applications lacks.a.***,this paper discussed the heat transfer and friction characteristics.a.d the synergy of three fields in the channel under the guidance of the field synergy principle for four typical PCHE ***,the comprehensive performance of four channels was ***,the heat transfer and friction factor correlations for s-CO_(2)in four channels were *** findings demonstrate that the synergy of velocity and pressure fields of the straight channel PCHE is better(β≈180°),so its resis.a.ce loss is relatively *** zigzag and sinusoidal wavy channels.a.d the airfoil fins can reduce the angle a between the temperature gradient and velocity,thus enhancing the heat *** sinusoidal wavy channel can reduce flow resis.a.ce compared to the zigzag channel due to the rounded *** streamlined airfoil structure can guide the flow and reduce backflow,thus reducing resis.a.ce *** the range of Re studied in this paper,the maximum error of the proposed heat transfer and friction factor correlations of PCHE is 7.0%,which shows good fitting *** res.a.ch in this paper can provide a reference for the selection and design of PCHE with different channel configurations.

关键词： printed circuit heat exchanger supercritical carbon dioxide typical channel structure field synergy analysis

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