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CFB cyclones at high temperature:Operational results and design assessment

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Particuology 2008年第3期6卷 149-156页

作者： Raf Dewil Jan Baeyens Bart Caerts Department of Chemical Engineering Associated Faculty of Technology and Bio-sciencesCampus De NayerKatholieke Universiteit LeuvenJan De Nayerlaan 5B-2860 Sint-Katelijne-WaverBelgium Department of Chemical Engineering University of BirminghamEdgbastonBirmingham B15 2TTUnited Kingdom Department of Chemical Engineering Katholieke Universiteit LeuvenWillem De Croylaan 46B-3001 HeverleeBelgium

Pressure drop and cut size measurements are reported for a full scale cyclone operating within a 58 MWth CFB-combustor unit at 775 ℃. The paper reviews the vast number of equations to calculate the pressure drop and separation efficiency of cyclones, generally for operation at ambient temperature and at low Cs [〈0.5]. None of the literature correlations predicts the pressure drop with a fair accuracy within the range of experimental operating conditions. The cut size d50 can be estimated using direct empirical methods or using the Stokes number, Stk50. Both methods were used to compare measured and predicted values of d50. With the exception of Muschelknautz and Krambrock, none of the equations made accurate predictions. Finally, an alternative method to determine the friction factor of the pressure drop equation （Euler number, Eu） and of the cut size is proposed. The Eu number is determined from the geometry of common cyclones, and the derived value of Stk50 defines more accurate cut sizes. The remaining discrepancy of less than 5%, when compared with the measured values, is tentatively explained in terms of a reduced cyclone diameter due to the solids layer formed near its wall. Further measurements, mostly using positron emission particle tracking, elucidate the particle motion in the cyclone and both tracking results and the influence of the particle movement on Eu and Stk50 will be discussed in a follow-up paper.

关键词： Cyclone high loading high temperature Combustor

Graphite-based solid lubricant for high-temperature lubrication

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Friction 2021年第6期9卷 1660-1672页

作者： Wenjuan HUAI Chenhui ZHANG Shizhu WEN State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

high-temperature solid lubricants play a significant role in the hot metal forming process.However,preparing high-temperature solid lubricant is formidably challenging due to the stern working conditions.Here we successfully develop a new type of eco-friendly high-temperature graphite-based solid lubricant by using amorphous silica dioxide,aluminum dihydrogen phosphate,and solid lubricant graphite.The solid lubricating coating exhibits excellent tribological properties with a very low friction coefficient and good wear protection for workpiece at high temperature under the air atmosphere.An array of analytical techniques reveals the existence of solid lubricant graphite in the lubricating coating after the high-temperature friction test.A synergistic effect between the protective surface film and the solid lubricant graphite is proposed to account for such superior lubricating performance.This work highlights the synergistic effect between the protection layer and the lubricant graphite and further provides the insight in designing the high-temperature solid lubricant.

关键词： graphite-based solid lubricant coating high temperature air atmosphere high lubricating performance

Corrosion behaviour of NiCrFeAl-hBN seal coatings in oxidation environments at a high temperature

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Rare Metals 2021年第1期40卷 212-218页

作者： Su-Yuan Yang Dan Guo Xing-Wang Cheng Jian-Ming Liu Yue-Guang Yu School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081.China National Key Laboratory of Science and Technol Beijing General Research

The purpose of this investigation was to evaluate the microstructure,high-temperature oxidation behaviour,and hardness of a seal coating under controlled exposures at 750℃with different exposure times.The results reveal that the main phases in the coating are Ni,FeNi3,and hexagonal BN,withα-Al_(2)O_(3)peaks appearing after 2-h oxidation.As the exposure time increases,the diffraction peak intensity ofα-Al_(2)O_(3)begins to decrease and Cr_(2)O_(3)peaks appear after 200 h.After 1000 h,Cr_(2)O_(3)becomes dominant with only small amounts ofα-Al_(2)O_(3)remaining.The high-temperature oxidation process of the coating includes three stages:the fast stage,transition stage,and slow stage.The oxidation rate is constant in each stage,and in the fast stage and slow stages with values of7.9×10^(-4)and 8.37×10^(-5)mg^(2)·cm^(-4)·s^(-1),respectively.Initially,α-Al_(2)O_(3)forms near the pores in the coating,followed by the formation of Cr_(2)O_(3).As the exposure time increases,oxidation penetrates into the interior of the coating along phase boundaries to form island-shaped inner oxide layers with high concentrations of Cr,Ni,and Fe.Additionally,hardness increases with increasing oxide percentage.

关键词： NiCrFeAl-hBN Seal coating Oxidation Microstructure high temperature

Overview of composition and technique process study on 2:17-type Sm-Co high-temperature permanent magnet

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Rare Metals 2021年第4期40卷 790-798页

作者： Chao Wang Ming-Gang Zhu Division of Functional Materials Central Iron and Steel Research InstituteBeijing 100081China

Sm-Co permanent magnets are widely used in aerospace equipments,tubes,sensors and hybrid electric vehicles due to their excellent magnetic properties at both room and high temperatures.Compared to that of Nd-Fe-B magnets,the capability of reliably operating at temperatures up to 500℃ is the biggest preponderance of Sm-Co permanent magnets.However,the reliable high-temperature magnetic properties are susceptible to composition and technique processes.So,appropriate composition and matched technique processes are prerequisites for good high-temperature magnetic properties.This review mainly emphasizes the influences of Sm,Fe,Cu and Zr contents and technique processes on development of high-temperature performance and discusses the controversial hightemperature coercivity mechanism of 2:17-type high-temperature Sm-Co magnets.

关键词： 2-type Sm-Co magnet high temperature Coercivity temperature coefficient Coercivity mechanism

Bi-prism-based single-lens three dimensional digital image correlation system with a long working distance: Methodology and application in extreme high temperature deformation test

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Science China(Technological Sciences) 2018年第1期61卷 37-50页

作者： WU LiFu YIN YuanJie ZHANG Qi FANG DaiNing ZHANG RuBing ZHU JianGuo XIE HuiMin AML Department of Engineering Mechanics Tsinghua University Institute of Advanced Structure Technology Beijing Institute of Technology Department of Mechanics School of Civil Engineering Beijing Jiaotong University Faculty of Civil Engineering and Mechanics Jiangsu University

As a novel three dimensional digital image correlation(3 D DIC) method, the bi-prism-based single lens(BSL) 3 D DIC method has been proposed and developed in recent years. Making use of a bi-prism, this method is able to perform a 3 D DIC measurement using only a single camera. Thus, the integration level of a BSL 3 D DIC system could be much higher than that of the double-camera3 D DIC system. In this paper, using a small-angle bi-prism and a camera with a longer focal length, a special BSL 3 D DIC system with a long working distance is designed for measurements in extreme environments. The principle of the system is first studied,and practical methods are then proposed for the system set-up and the determination of system parameters. Then, feasibility of the measurement system is verified by out-of-plane rigid-body translation tests. Finally, the BSL 3 D DIC system is proven to be capable of combining with a high-temperature testing instrument to perform deformation tests in a high-temperature environment of up to 1500°C.

关键词： three dimensional digital image correlation(3D DIC) single lens bi-prism high temperature deformation measurement

Analysis of the fluid-bed stability of FCC catalysts at high temperature in terms of bed elasticity

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Particuology 2008年第1期6卷 30-37页

作者： Paola Lettieri Luca Mazzei Department of Chemical Engineering University College London Torrington Place London WC1E 7JE UK

The effect of temperature on the fluid-bed stability of three FCC catalysts has been analyzed through considerations on fluid-bed elasticity. Experimental findings on the effect of temperature on the elasticity modulus at minimum bubbling conditions, （E）mb, were analyzed using the hydrodynamic fluid-bed stability model developed by Foscolo and Gibilaro （1984） and adopting the interparticle-forces-based stability criterion developed by Mutsers and Rietema （1977）. For both models, the parameters which control changes in （E）mb with temperature are discussed, in order to establish the origin of the fluid-bed elasticity and analyze the ability of these models to discriminate between the relative importance of the hydrodynamic and interoarticle forces on the stability of the fluidized catalysts.

关键词： Fluidization FCC catalysts high temperature Stability Bed elasticity

A damage-coupled multi-axial time-dependent low cycle fatigue failure model for SS304 stainless steel at high temperature

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Acta Metallurgica Sinica(English Letters) 2011年第2期24卷 169-174页

作者： Yujie LIU Qing GAO Guozheng KANG School of Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 China

Based on the time-dependent strain cyclic characteristics and fatigue behaviors of SS304 stainless steel under multi-axial cyclic loading at 700 ？ C, and in the frame of unified visoco-plastic cyclic constitutive model and continuum damage mechanics theory, the damage-coupled multi-axial time-dependent constitutive model and fatigue failure model were proposed. In the model, the evolution equation of damage was introduced in and the time-dependent effects, e.g. holding time, loading rate, were taken into account. The model was applied to the simulation of whole-life cyclic deformation behaviors and prediction of LCF life for SS304 stainless steel in multiaxial time-dependent low cycle fatigue tests. It is shown that the simulated results agree well with experimental ones.

关键词： SS304 stainless steel Constitutive model Low cycle fatigue Failure model Damage-coupled high temperature

Preparation of Eu(TTA)_2phen(MA)/SiR Fluorescent Materials under high Mechanical Blending temperature

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Journal of Rare Earths 2006年第6期24卷 712-718页

作者：温世鹏刘力冯予星张婉金日光张立群 Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials Beijing University of Chemical Technology Beijing 100029China Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials Beijing University of Chemical Technology Beijing 100029ChinaKey Laboratory for Nanomaterials Educational Department Beijing University of Chemical Technology Beijing 100029China Key Laboratory of Science and Technology of Controllable Chemical Reactions Ministry of Education Beijing University of Chemical Technology Beijing 100029 China

Eu（TTA）2（phen）（MA） complexes were synthesized, in which MA was introduced as the acidic ligand to increase the fluorescent intensity of the complexes. The complexes were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and fluorescent spectra, respectively. Different amounts of rare earth complexes were blended with silicon rubber over the melting point of Eu （TTA） 2 （phen）（MA）. Next, a definite amount of 2,5-dimethyl-2, 5-di （tert-butylperoxy） hexane was added as a cross linker to the composite, to get the uncured composites. Subsequently, the composites were vulcanized at 160℃, and silicon rubber-based composites with different contents of the complexes were prepared and their fluorescent properties were observed. The contents of rare earth complexes were 0.96 %, 2.83 %, 4.63 % and 6.36 % （mass fraction）, respectively. Moreover, the composites of Eu （TTA） 2 （phen）（ MA ）/SiR were measured by SEM, XRD, and fluorescent spectra. The measurement result shows that the fluorescent intensity of uncured rubber is similar to one of the pure rare earth complexes. However, there is no marked change of fluorescent intensity in the uncured rubber when the content of rare earth complexes continues to increase.

关键词： rare earth complex high temperature blend fluorescent property

Microstructure and mechanical behavior of Inconel 625 alloy processed by selective laser melting at high temperature up to 1000℃

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Rare Metals 2020年第10期39卷 1181-1189页

作者： Xiao-An Hu Gao-Le Zhao Fen-Cheng Liu Wei-Xiong Liu School of Aircraft Engineering Nanchang Hangkong UniversityNanchang 330063China Airbreathing Hypersonic Technology Research Center China Aerodynamic Research and Development CenterMianyang 621000China

Mechanical behavior of Inconel 625 alloy manufactured by selective laser melting(SLM)was experimentally studied.Tensile tests were performed at various temperatures(20,540,760,815,870,950 and 1000℃).The microstructures and fracture mechanism were investigated using optical microscopy(OM),scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The SLM Inconel 625 exhibits excellent plastic deformation at low temperature.However,significant embrittlement for the SLM Inconel 625 was found at elevated temperatures compared to low temperature and traditional forging process.Through microstructure studies,the non-homogenous microstructure is a key factor causing the intergranular cracking mode at elevated temperature.Moreover,carbides were found to form at the grain boundary at elevated temperatures.These carbides could weaken the strength of the grain boundary at elevated temperatures,which decreased the tensile strength and ductility of the alloy processed by SLM.

关键词： Nickel-based superalloy Selective laser melting Embrittlement high temperature Microstructure