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Discontinuous Precipitation Reaction Front of Cellular Recrystallization for a Single-Crystal Superalloy Studied by Electron Microscopy

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Chinese Physics Letters 2015年第7期32卷 106-109页

作者：卓龙超梁淑华王锋刘玉峰熊继春 School of Materials Science and Engineering Xi'an University of Technology Xi'an 710048 National Center for Electron Microscopy in Beijing School of Materials Science and Engineering State Key Laboratory of New Ceramics and Fine Processing Laboratory of Advanced Materials Tsinghua University Beijing 100084 State Key Lab of Power Systems Department of Thermal Engineering Tsinghua University Beijing 100084 Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials Beijing 100095

Combining analytical transmission electron microscopy systematic tilting, scanning transmission electron microscopy mapping and nano-beam electron diffraction operations, we obtain direct experimental proofs on the boundary type, elemental distribution and structure of the cellular reerystallization reaction front for a single- crystal superalloy. It is demonstrated that the cellular recrystallization reaction front usually corresponds to coincidence site lattice boundaries, and a thin layer of γ-forming elements such as Re, Cr, Mo and Co invariably exists in the direct reaction front. Furthermore, the thin layer with γ-forming elements is proved to be γ phase, with the same orientation as the neighboring original matrix.

关键词： CR OM Discontinuous Precipitation Reaction Front of Cellular Recrystallization for a Single-Crystal Superalloy Studied by Electron Microscopy

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Distribution of Temperature and Characteristics of Soot Volume Fraction in MILD-OCC Flame 9th

Distribution of Temperature and Characteristics of Soot Volu...

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9th International Symposium on Coal Combustion, ISCC 2019

作者： Lu, Jingwen Zhang, Shuwei Tan, Longhui Lu, Jianyi Hebei Key Lab of Power Plant Flue Gas Multi-Pollutants Control Department of Environmental Science and Engineering North China Electric Power University Baoding071003 China MOE Key Laboratory of Resources and Environmental Systems Optimization College of Environmental Science and Engineering North China Electric Power University Beijing102206 China

ISBN: (纸本)9789811616563

Coal and methane were burnt in the MILD-OCC combustion flame under different combustion conditions to study the temperature distribution and characteristics of soot volume fraction. In this experiment, the flame temperature distribution is measured by thermocouple and the volume fraction (fv) of soot at each sampling point is calculated, then combining with the mass concentration of soot by the filter weighing method to obtain the distribution characteristics of soot in the flame. The results of thermocouple particle densitometry (TPD) show that the formation and oxidation of soot at every point in the flame is related closely to its position and temperature in the flame. The fv of soot in the center of the flame is negatively correlated with the temperature of the flame during the MILD-OCC combustion. The lower temperature region of the flame is conducive to the growth of soot, which leads to higher value of fv. The higher temperature in the center of the flame is beneficial to the oxidation of the soot particles, resulting to lower value of fv. The results of the filter membrane weighing method show that the formation of soot mainly occurs in the central region of the flame. When the radial distance increases, the flame temperature rises, and the soot concentration decreases due to oxidation. On the whole, the distribution of soot measured by the filter membrane weighing method is roughly consistent with that calculated by the TPD, which provides a reference for further research on the MILD-OCC combustion. © 2022, Tsinghua University Press.

关键词： Thermocouples

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Effect of extrusion on corrosion behavior and corrosion mechanism of Mg-Y alloy

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Journal of Rare Earths 2016年第3期34卷 315-327页

作者：徐宏张新张奎石阳任霁萍 School of Materials Science and Engineering North University of China Institute of Thermal Power Generation Technology China Datang Coporation Science and Technology Research Institute State Key Lab for Fabrication & Processing of Non-ferrous Metals General Research Institute for Non-ferrous Metals Shenyang Area Military Representative Office of Armored Military Representative Office Chinese PLA General Armament Department

The influences of the hot extrusion process on the microstructure, corrosion behavior and corrosion mechanism for Mg-Y magnesium alloy were studied by means of the microstructure observation, weight loss test, electrochemical test and corrosion morphology test. The results showed that with increasing of the extrusion ratio, the shear flow line on the vertical section of the extruded alloy increased, the shear bands parallel lines became more clearly visible, and a large number of fine equiaxed grains distributed in parallel with the flow lines. The open circuit potential had a certain degree of improvement after extrusion, the open circuit potential increased with increment of extrusion ratio, and the corrosion potential of the vertical section was higher than that of the same alloy in the same compression ratio. The shift rate of the corrosion potential relatively became larger with increasing of the extrusion ratio, and the cathode corrosion current corresponding to the branch migration shifted to the positive direction. The high frequency capacitive arc increased with increment of the extrusion ratio, and the radius of capacitive arc of the vertical section was slightly larger than that of the transverse section. The corrosion morphologies of Mg-0.25 Y alloy were uniform corrosion, and the corrosion morphologies of Mg-（2.5, 5, 8 and 15） were the pitting corrosion and the small range, deep depth localized corrosion.

关键词： extrusion Mg-Y alloy corrosion behavior corrosion mechanism rare earths

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Theoretical study on transient hot-strip method by numerical analysis

Theoretical study on transient hot-strip method by numerical...

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2009 ASME Summer Heat Transfer Conference, HT2009

作者： Wei, Gaosheng Du, Xiaoze Zhang, Xinxin Yu, Fan School of Energy and Power Engineering Key Lab. of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education North China Electric Power University Beijing 102206 China Department of Thermal Engineering University of Science and Technology Beijing Beijing 100083 China

ISBN: (纸本)9780791843567

This paper presented the effects of finite dimensions of the sample and non-zero heat capacity of the strip on thermal conductivity determination with the transient hot-strip (THS) method. Through numerical analysis of temperature field within the system composed of the samples and the strip, the temperature transients at the strip surface were obtained to calculate the thermal conductivities of materials, which were compared to the exact values. The effect of heat losses out of the external surfaces of the sample and the heat capacity of the strip on thermal conductivity determination were then analyzed comprehensively. It is shown that the sample finite dimensions have great effect on thermal conductivity determination, especially on the materials with relatively higher thermal diffusivities, and the measured thermal conductivity always lower than the exact value due to the lower convective heat transfer coefficient out of the external surfaces of the sample. The measurement error is estimated less than 2.2 percent for the material with thermal diffusivity less than 4.0 × 10-6 m2/s with the sample dimensions of 120 mm x 60 mm (width x thickness) and the fitting time interval of 20 - 450s. The non-zero heat capacity of the strip has great effect on thermal conductivity determinations of the materials with relatively lower thermal diffusivities. The measurement error is estimated less than 5 percent for the material with thermal diffusivity larger than 0.8 × 10-7 m2/s with Cr20Ni80 alloy as the strip. Copyright © 2009 by ASME.

关键词： Specific heat

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Scheduling of electric-thermal integrated energy system considering environmental cost 4

Scheduling of electric-thermal integrated energy system cons...

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2020 4th International Workshop on Advances in Energy science and Environment engineering, AESEE 2020

作者： Xingchen, Yao Fei, Xu Lei, Chen Ling, Hao Tuo, Jiang Te, Cheng Yong, Min Qun, Chen State Key Lab of Power Systems Department of Electrical Engineering Tsinghua University Beijing100084 China School of Mechanical Engineering Beijing Institute of Technology Beijing100081 China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering Mechanics Tsinghua University Beijing100084 China

Coordinated scheduling of electric heating comprehensive energy system is an effective measure to promote wind power consumption and solve environmental problems fundamentally. In the existing coordinated scheduling of electric heating, the optimization goal usually only considers the minimum of abandoned wind or the minimum of overall coal consumption of the system, and does not directly take pollutant emission as the optimization index. In the actual operation, the target of minimum total coal consumption or light rejection rate of abandoned air is likely to be inconsistent with the target of minimum pollutant emission. Therefore, this paper proposes a coordinated scheduling model of electric heating comprehensive energy system considering environmental cost, selects the appropriate expression form of environmental cost, unifies the economic cost and environmental cost, and takes its weighted sum value as the optimization goal, so as to achieve the lowest comprehensive economic cost and environmental cost on the basis of maximizing the consumption of wind power. Finally, the comparison between the traditional optimization model and the model proposed in this paper is carried out by the way of example simulation. The results show that the new optimization model is helpful to reduce the environmental expenditure, and the cost of considering the environmental cost is 5.2% lower than not considering the environmental cost. © Published under licence by IOP Publishing Ltd.

关键词： Electric heating

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THE COMPREHENSIVE PERFORMANCE COMPARISON RESEARCH BETWEEN TWO TYPES OF RADIATORS APPLIED IN ELECTRONIC EQUIPMENT 29

THE COMPREHENSIVE PERFORMANCE COMPARISON RESEARCH BETWEEN TW...

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2022 29th International Conference on Nuclear engineering, ICONE 2022

作者： Huang, Chonghai Zhang, Yelei Yang, Xiaohu Ke, Hanbing Xiao, Qi Science and Technology on Thermal Energy and Power Laboratory Wuhan 2nd Ship Design and Research Institute Hubei Province Wuhan China Key Laboratory of Thermo-Fluid Science and Engineering MOE Xi'an Jiaotong University Shaanxi Province Xi'an China

ISBN: (纸本)9780791886410

The development direction of miniaturization and low noise of electronic equipment in nuclear power plant puts forward higher requirements for radiators. Two experimental systems were constructed to test the volume, noise and heat transfer performance of air-cooled radiator and micro-pump-driven water-cooled micro-channel radiator that can be applied to electronic equipment of nuclear power plant. The experimental results show that the comprehensive performance of micro-pump-driven water-cooled micro-channel radiator is better than that of the air-cooled radiator. Compared with the air-cooled radiator, the micro-pump-driven water-cooled micro-channel radiator can reduce the temperature rise of heat source by more than 20°C, and the volume is only 38% of the air-cooled radiator. For the micro-channel using in the present study, the flow rate of cooling water is the main factor which affects the heat transfer performance of radiator when the flow rate of cooling water is lower than 2.5L/min. However, when the flow rate of cooling water is more than 2.5L/min, the increase of cooling water flow rate has little impact on heat transfer performance, and the self-structure of the radiator and thermal resistance have become the main factors restricting the improvement of heat transfer performance. Copyright © 2022 by ASME.

关键词： Flow of water

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超重力湍流对流中的温度和速度脉动统计特性研究

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Acta Mechanica Sinica 2023年第4期39卷 147-156页

作者：王东璞刘婧周全孙超 Center for Combustion Energy Key Laboratory for Thermal Science and Power Engineering of MoEand Department of Energy and Power EngineeringTsinghua UniversityBeijing100084China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai200072China Department of Engineering Mechanics School of Aerospace EngineeringTsinghua UniversityBeijing100084China

本文通过实验研究了超重力湍流对流系统中的温度脉动和速度脉动.负尖峰信号在温度脉动时间序列中周期性地出现,这可能是由旋转坐标系下的所谓的纬向流推动冷羽流的周向运动造成的.周期τ0随着瑞利数(Ra)的增加而略微减小,并且τ0比大尺... 详细信息

本文通过实验研究了超重力湍流对流系统中的温度脉动和速度脉动.负尖峰信号在温度脉动时间序列中周期性地出现,这可能是由旋转坐标系下的所谓的纬向流推动冷羽流的周向运动造成的.周期τ0随着瑞利数(Ra)的增加而略微减小,并且τ0比大尺度环流的时间尺度大超过一个数量级.此外,对于不同Ra数,温度脉动能谱在2≾f≾10范围内遵循P(f)∼f^(−5),这意味着超重力湍流对流中可能存在湍流与纬向流相平衡的反向能量级串,本研究还计算了反向级串的截止频率莱茵(Rhines)频率f_(β),f_(β)比–5次方斜率能谱范围的最低频率还低半个数量级左右.本研究还发现时间平均径向速度的周向分布没有明显的峰谷,这为纬向流的存在性提供了进一步的证据.此外,我们发现该系统中的温度和速度脉动的概率密度分布可以通过Wang等人提出的经典瑞利-伯纳德(Rayleigh-Bénard)对流的理论模型(Wang等,2019,2022)较好地拟合和分析.

关键词：概率密度分布温度脉动能量级串速度脉动超重力湍流对流时间序列截止频率

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Lattice Boltzmann simulation of the gas-solid adsorption process in reconstructed random porous media

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Physical Review E 2016年第4期93卷 043101-043101页

作者： L. Zhou Z. G. Qu T. Ding J. Y. Miao MOE Key Laboratory of Thermal-Fluid Science and Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China Beijing Key Laboratory of Space Thermal Control Technology Beijing Institute of Spacecraft System Engineering Beijing 100094 China

The gas-solid adsorption process in reconstructed random porous media is numerically studied with the lattice Boltzmann (LB) method at the pore scale with consideration of interparticle, interfacial, and intraparticle mass transfer performances. Adsorbent structures are reconstructed in two dimensions by employing the quartet structure generation set approach. To implement boundary conditions accurately, all the porous interfacial nodes are recognized and classified into 14 types using a proposed universal program called the boundary recognition and classification program. The multiple-relaxation-time LB model and single-relaxation-time LB model are adopted to simulate flow and mass transport, respectively. The interparticle, interfacial, and intraparticle mass transfer capacities are evaluated with the permeability factor and interparticle transfer coefficient, Langmuir adsorption kinetics, and the solid diffusion model, respectively. Adsorption processes are performed in two groups of adsorbent media with different porosities and particle sizes. External and internal mass transfer resistances govern the adsorption system. A large porosity leads to an early time for adsorption equilibrium because of the controlling factor of external resistance. External and internal resistances are dominant at small and large particle sizes, respectively. Particle size, under which the total resistance is minimum, ranges from 3 to 7 μm with the preset parameters. Pore-scale simulation clearly explains the effect of both external and internal mass transfer resistances. The present paper provides both theoretical and practical guidance for the design and optimization of adsorption systems.

关键词： Flows in porous media Lattice-Boltzmann methods

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Study on the effect of gas channel arrangement on the performance of air-cooled fuel cells

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Huagong Xuebao/CIESC Journal 2022年第10期73卷 4625-4637页

作者： Peng, Ming Xia, Qiangfeng Jiang, Lixiang Zhang, Ruiyuan Guo, Lingyi Chen, Li Tao, Wenquan Key Laboratory of Thermal Fluid Science and Engineering of MOE School of Energy and Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Jiaxing Power Supply Company of State Grid Zhejiang Jiaxing314000 China

Air-cooled fuel cells have great advantages in unmanned aerial vehicle application, but they still face problems such as low performance and complex water and heat management. In this study, effects of co-flow, counter-flow and cross-flow gas channel arrangements on the performance of air-cooled fuel cell are studied. The coupling mechanism between various physical quantities is also discussed. It is found that gas channel arrangements have a significant influence on the distribution of key physical quantities of air-cooled fuel cells. Affected by the uneven distribution of dissolved water content, the current density distribution in the cathode catalytic layer of cross-flow arrangement presents an isolated point distribution. Due to good thermal management of cross-flow gas channel arrangement, it can significantly improve the water content of membrane electrode, and then improve the cell performance. Under the operating voltage of 0.6 V, the current density of cross-flow gas channel arrangement is 20% higher than that of co-flow gas channel arrangement. In addition, it is also found that the reduction of ambient humidity will significantly reduce the performance of air-cooled fuel cells. © 2022 Chemical Industry Press. All rights reserved.

关键词： Fuel cells

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Control of Nonlinear Constrained Ultra-Supercritical Boiler–Turbine Units Using Offset-Free Output-Feedback Stable MPC

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IFAC-PapersOnLine 2018年第28期51卷 155-160页

作者： Chen, Chen Pan, Lei Shen, Jiong Lee, Kwang Y. Zhang, Fan Sun, Li Wu, Xiao Zhang, Junli Xue, Wenchao Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education Southeast University Nanjing210096 China Department of Electrical and Computer Engineering Baylor University One Bear Place #97356 WacoTX76798-7356 United States State Key Lab of Power System Department of Energy and Power Engineering Tsinghua University Beijing100084 China Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing China

It is extremely challenging to control ultra-supercritical boiler–turbine unit on account of its nonlinearity, coupling among multi-variables, hard input constraints, and unknown disturbances. An offset-free output-feedback stable model predictive control (MPC) (OFOF-SMPC) for nonlinear constrained ultra-supercritical boiler-turbine units is investigated. It is shown that the OFOF-SMPC is composed of a disturbance and state observer, a steady-state target calculator as well as a stable MPC, which can remove unknown disturbances from output channels and ensure the stability of the closed-loop system with input constraints. Simulation results demonstrate the effectiveness of the proposed algorithm. © 2018

关键词： Feedback

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