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A stability condition for turbulence model:From EMMS model to EMMS-based turbulence model

Particuology 2014年第5期12卷 142-154页

作者： Lin Zhang Xiaoping Qiu Limin Wang Jinghai Li The EMMS Group State Key Laboratory of Multiphase Complex SystemsInstitute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences

The closure problem of turbulence is still a challenging issue in turbulence modeling. In this work, a stability condition is used to close turbulence. Specifically, we regard single-phase flow as a mixture of turbulent and non-turbulent fluids, separating the structure of turbulence. Subsequently, according to the picture of the turbulent eddy cascade, the energy contained in turbulent flow is decomposed into different parts and then quantified. A turbulence stability condition, similar to the principle of the energy-minimization multi-scale （EMMS） model for gas-solid systems, is formulated to close the dynamic constraint equa- tions of turbulence, allowing the inhomogeneous structural parameters of turbulence to be optimized. We name this model as the ＂EMMS-based turbulence model＂, and use it to construct the corresponding turbulent viscosity coefficient. To validate the EMMS-based turbulence model, it is used to simulate two classical benchmark problems, lid-driven cavity flow and turbulent flow with forced convection in an empty room, The numerical results show that the EMMS-hased turbulence model improves the accuracy of turbulence modeling due to it considers the principle of compromise in competition between viscosity and inertia.

关键词： Stability condition Mathematical modeling Turbulence EMMS Hydrodynamics Computational fluid dynamics

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Inside Cover: Nb‐Doped Hematite Nanorods for Efficient Solar Water Splitting: Electronic Structure Evolution versus Morphology Alteration (ChemNanoMat 7/2016)

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ChemNanoMat 2016年第7期2卷

作者： Yanming Fu Chung‐Li Dong Wan‐Yi Lee Jie Chen Penghui Guo Liang Zhao Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 P.R. China Department of Physics Tamkang University Tamsui 25137 Taiwan Department of Electrophysics National Chiao Tung University Hsinchu 30010 Taiwan

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Metal-Semiconductor Schottky Barrier engineering for Ⅲ-Ⅴ Nanowire Based Electronics and Photovoltaics

Metal-Semiconductor Schottky Barrier Engineering for Ⅲ-Ⅴ N...

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2015欧亚经济论坛-2015第五届国际纳米科技大会

作者： Ning Han Zaixing Yang Yunfa Chen Johnny C Ho State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences Department of Physics and Materials Science City University of HongKong

The heterojunctions such as p-n junction and Schottky contact,play an important role in nanoelectronics and optics,and thus are highly desired and challenging for high performance *** this report,Schottky contacts are controllably fabricated on III-V nanowires（NWs） for fabrication of functional InAs NW logic circuits and GaAs NW *** specific,the threshold voltage of InAs NW field effect transistors（FETs） are finely tuned by decorating InAs channel（.1 eV） with metal clusters which possess varied work functions（Au.3 eV,Ni.1 eV,Cr.5 eV,and Al.2 eV） to form Schottky contacts with tuned barrier *** Schottky contact tailors the electron concentration and thus shifts the threshold voltage of InAs FET,and NMOS circuits can be designed and implemented *** the other hand,the Schottky contact of Au and Al electrodes on GaAs NWs will provide the barrier for the separation and collection of the photo generated electron/hole pairs,and thus high efficiency GaAs NW based photovoltaics can be *** these results show the facile fabrication and the versatile functions of Schottky barrier engineering in III-V NW based nanoelectronics and optics,which is also promising in other functional devices such as photodetectors and gas sensor etc.

关键词： Metal-Semiconductor Schottky Barrier engineering for Nanowire Based Electronics and Photovoltaics

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Numerical simulation of ignition of coke-oven gas on an industry boiler

Numerical simulation of ignition of coke-oven gas on an indu...

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International Conference on Frontiers of Energy, Materials and Information engineering, ICFMEI 2014

作者： Shi, Hong Wei Wang, Shuai Wang, Dong Zhang, Xing Kai State key lab of multiphase flow in power engineering Xi'an jiaotong university Xi’an China

ISBN: (纸本)9783038352778

Some coking plants discharge coke-oven gas to the environment,this pollute the *** order to solute the problem,the paper proposed a method:using coke-oven gas instead of light oil to ignite the *** virtue of doing this was to save *** FLUENT software package to simulate ignition in boiler is a effective mean,it can show the distribution of temperature in the *** simulation result shows that using CFD methods can provide ideas for the operation of the boiler. © (2014) Trans Tech Publications, Switzerland.

关键词： Computational fluid dynamics

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Preliminary safety analysis of the PWR with accident-tolerant fuels during severe accident conditions

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Annals of Nuclear Energy 2015年 80卷 1-13页

作者： Xiaoli Wu Wei Li Yang Wang Yapei Zhang Wenxi Tian Guanghui Su Suizheng Qiu Tong Liu Yongjun Deng Heng Huang State Key Laboratory of Multiphase Flow in Power Engineering School of Nuclear Science and Technology Xi’an Jiaotong University No. 28 Xianning West Road Xi’an Shanxi 710049 China China Nuclear Power Technology Research Institute A-1101 Fengde Plaza No. 6 Hangkong Road Chengdu Sichuan 610000 China

Experience gained in decades of nuclear safety research and previous nuclear accidents direct to the investigation of passive safety system design and accident-tolerant fuel (ATF) system which is now becoming a hot research point in the nuclear energy field. The ATF system is aimed at upgrading safety characteristics of the nuclear fuel and cladding in a reactor core where active cooling has been lost, and is preferable or comparable to the current UO 2 –Zr system when the reactor is in normal operation. By virtue of advanced materials with improved properties, the ATF system will obviously slow down the progression of accidents, allowing wider margin of time for the mitigation measures to work. Specifically, the simulation and analysis of a large break loss of coolant accident (LBLOCA) without ECCS and extended station blackout (SBO) severe accident are performed for a pressurized water reactor (PWR) loaded with ATF candidates, to reflect the accident-tolerance of ATF.

关键词： Safety analysis Accident-tolerant Severe accident

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A research on ignition of a boiler by using coke-oven gas instead of light oil and alternation of the boiler

A research on ignition of a boiler by using coke-oven gas in...

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International Conference on Frontiers of Energy, Materials and Information engineering, ICFMEI 2014

作者： Shi, Hong Wei Zhang, Xing Kai Wang, Dong Wang, Shuai State key lab of multiphase flow in power engineering Xi’an jiaotong university Xi’an China

ISBN: (纸本)9783038352778

In order to solute the question of boiler ignition in thermal electrical factory of an Aluminun plant, Coke-oven gas was used to substitute for ligtht oil. At the same output of boiler, the cost of start up can be reduced;at low boiler output coke-oven gas can be used to ignite coal, and the ignition was steady. Once upon a time, the coke-oven gas was ignited directly in the air, it wasted energy and caused envirnmental pollution. The coke-oven gas guns were placed in the under secondary air and the middle secondary air, the output of single gas gun was 800Nm3/h;the virtue of the arrangement was to prevent coke-oven gas consuming so much air for the coal. © (2014) Trans Tech Publications, Switzerland.

关键词： Coke

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CO_2 Leakage Identification in Geosequestration Based on Real Time Correlation Analysis Between Atmospheric O_2 and CO_2

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Chinese Journal of Chemical engineering 2014年第6期22卷 634-642页

作者：马登龙邓建强张早校 State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University School of Chemical Engineering and Technology Xi’an Jiaotong University

The paper describes a method for monitoring CO2 leakage in geological carbon dioxide sequestration. A real time monitoring parameter, apparent leakage flux(ALF), is presented to monitor abnormal CO2 leakage, which can be calculated by atmospheric CO2 and O2 data. The computation shows that all ALF values are close to zero-line without the leakage. With a step change or linear perturbation of concentration to the initial CO2 concentration data with no leakage, ALF will deviate from background line. Perturbation tests prove that ALF method is sensitive to linear perturbation but insensitive to step change of concentration. An improved method is proposed based on real time analysis of surplus CO2 concentration in least square regression process, called apparent leakage flux from surplus analysis(ALFs), which is sensitive to both step perturbation and linear perturbations of concentration. ALF is capable of detecting concentration increase when the leakage occurs while ALFs is useful in all periods of leakage. Both ALF and ALFs are potential approaches to monitor CO2 leakage in geosequestration project.

关键词： CO2 monitor carbon storage gas leakage O2/CO2 exchange correlation analyysis

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Single GaAs nanowire Schottky solar cell with a record high efficiency of ～17%

Single GaAs nanowire Schottky solar cell with a record high ...

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The 6th International Conference on Nanoscience & Technology, China 2015

作者： Ning Han Yunfa Chen Johnny C.Ho State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences Department of Physics and Materials Science City University of Hong Kong

Solar energy utilizations in the form of photovoltaics are vastly investigated in order to provide enough clean energy after the fossil energy era. However, it is still a great challenge to fabricate solar cells with the high efficiency and low cost aimed at the third generation photovoltaics, though the material consumption will be greatly reduced in the nanometer scale. In this study, highly crystalline, long and dense Ga As nanowires(NWs) are synthesized on amorphous Si O2/Si substrates in the solid source chemical vapor deposition(CVD) system, avoiding the use of expensive single crystalline epitaxial substrates(e.g. Ga As(111)B) in metal-organic(MO) CVD or molecular beam epitaxy(MBE) methods [1]. Then, the single NWs are fabricated into Schottky contact solar cells [2] by a simple ultraviolet photolithography process getting rid of the complicated p-i-n structures complementation. Besides these low-cost advantages of the NW synthesis and device fabrication, the horizontal NW solar cell show a record high efficiency of 7% under air mass 1.5 global(AM 1.5G) illumination. This produces another record in addition to the vertically aligned p-i-n Ga As NW solar cells previously reported, in which the superior photovoltaic performance is attributed to the light concentrating effect of NWs with diameter in the order of light wavelength [3]. All these results show the promising prospect of the high quality Ga As NWs synthesis in low cost solid source CVD system, and the highly efficient photovoltaic applications in the simple Schottky contact configuration.

关键词： GaAs nanowires Schottky contact Solar cells Horizontal structure High efficiency

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Development and application of a UTSG thermal-hydraulic analysis code

Development and application of a UTSG thermal-hydraulic anal...

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International Congress on Advances in Nuclear Power Plants, ICAPP 2014

作者： Cong, Tenglong Tian, Wenxi Su, Guanghui Qiu, Suizheng School of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

ISBN: (纸本)9781632668264

Structural integrity of steam generator should be maintained during operation, since it performs as the pressure boundary of primary side coolant. Localized thermal-hydraulic parameters of secondary side are essential for the analysis of tube wastage, fatigue and failure. In this paper, a three-dimensional thermohydraulics analysis code, named STAF, is developed based on FLUENT. With STAF code, three-dimensional thermohydraulics of secondary side of AP1000 steam generator are generated. This code is developed based on the porous media theory. In this code, the drift flux two-phase model coupled with a simplified flow boiling model is utilized to present two-phase flow among the U-tube bundle. Downcomer, tube bundle, support plates and primary separators in steam generator are considered in STAF code. The calculated results are compared with a general steam generator thermohydraulic analysis code ATHOS, which is developed by the Westinghouse. The comparison indicates that STAF code performs well in evaluating thermal-hydraulic parameters in steam generator. The results show that the flow field varies significantly at different position in AP1000 steam generator. flow vapor quality at the inlet of primary separators varies significantly, which is a severe challenge to the capacity design of separators.

关键词： Steam generators

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Activating ZnO nanorod photoanodes in visible light by Cu ion implantation

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Nano Research 2014年第3期7卷 353-364页

作者： Meng Wang Feng Ren Guangxu Cai Yichao Liu Shaohua Shen Liejin Guo International Research Centre for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi 710049 China School of Physics and Technology Center for Ion Beam Application Wuhan University Wuhan 430072 China

Utilization of visible light is of crucial importance for exploiting efficient semiconductor catalysts for solar water splitting. In this study, an advanced ion implantation method was utilized to dope Cu ions into ZnO nanorod arrays for photoelectrochemical water splitting in visible light. X-ray diffraction （XRD） and X-ray photo-electron spectroscopy （XPS） results revealed that Cu^＋ together with a small amount of Cu^2＋ were highly dispersed within the ZnO nanorod arrays. The Cu ion doped ZnO nanorod arrays displayed extended optical absorption and enhanced photoelectrochemical performance under visible light illumination （A 〉 420 nm）. A considerable photocurrent density of 18 μA/cm^2 at 0.8 V （vs. a saturated calomel electrode） was achieved, which was about 11 times higher than that of undoped ZnO nanorod arrays. This study proposes that ion implantation could be an effective approach for developing novel visible-light-driven photocatalytic materials for water splitting.

关键词： ion implantation Cu ion doping ZnO nanorods photoanode water splitting

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