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Understanding the Initial Decomposition Pathways of the n-Alkane/Nitroalkane Binary Mixture

Chinese Journal of Chemistry 2013年第8期31卷 1087-1094页

作者： Yulei Guan Ying Zhang Chunhai Yi Bolun Yang Department of Chemical Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shannxi 710049 China

Addition of nitroalkanes into n-alkanes can lower the activation barriers of free-radical production and acceler- ate the decomposition of n-alkanes at relatively low temperatures. Four initial decomposition mechanisms of the n-butane/nitroethane binary mixture were proposed for the promoting effect and considered theoretically at the B3LYP, BB1K, BMK, MPW1K, and M06-2X levels with MG3S basis set. Energetics above was compared to high-level CBS-QB3 and G4 calculations. Calculated results confirm the feasibility of the four initial decomposition pathways：（I） the C--NO2 bond rupture of nitroethane to produce ethyl and .NO2, （II） HONO elimination from nitroethane followed by decomposition to .OH and .NO, （1II） rearrangement of nitroethane to ethyl nitrite which further dissociates into CH3CH20. and .NO, and （IV） direct hydrogen-abstraction ofnitroethane with n-butane.

关键词： free radical initial decomposition mechanism computational chemistry hydrogen-abstraction bimol-ecular

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Experimental and numerical investigation of two phase ejector performance with the water injected into the induced flow

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International Journal of Advanced Nuclear Reactor Design and Technology 2020年 2卷 15-24页

作者： Chen, WeiXiong Huang, ChenXi Bai, YuPing Chong, DaoTong Yan, JunJie Liu, JiPing State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

When injectors are used in petroleum industries or sea water desalination system, it is a special case that the induced gas is accompanied by water, the ejector is in two-phase operation. In the present study, the ejector performance at two phase flow is investigated experimentally and numerically. The results indicate that: the entrainment ratio would decrease when the water is injected into the induced flow, as well as the pressure ratio. The maximum decrement of entrainment ratio is around 40.5% at sub-critical mode when the motive pressure is 1.0 MPa, the induced pressure is 0.2 MPa, liquid-air ratio is 22%. For the pressure ratio, the maximum decrement is 62.5% when the motive pressure is 1.0 MPa, the induced pressure is 0.5 MPa, liquid-air ratio is 2.87%. However, the lower the induced pressure is, the more obvious the effect of mass flow rate on entrainment rate is, while the effect on pressure ratio is just opposite. Moreover, the performance becomes worse in sub-critical mode than that in critical mode. The effect of NXP on ejector performance also has been analyzed. There exists an optimum NXP whether the two phase flow ejector is in critical mode or sub-critical mode. The optimum NXP for entrainment ratio enlarges from 3.6 mm to 4.4 mm with the increase of water mass flowrate, and is bigger than that of single phase ejector (the optimum NXP is 2.8 mm). This study may provide a beneficial reference for the operation of supersonic ejectors on two phase flow. © 2020 Xi'an Jiaotong University

关键词： Two phase flow

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A numerical model of thermal analysis for woven wire screen matrix heat exchanger

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Cryogenics 2009年第9期49卷 482-489页

作者： Shuangtao, Chen Yu, Hou Hongli, Zhao Lan, Xi State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Woven wire screen matrix heat exchanger (WSMHE) is a kind of compact, light-weight and high-efficiency matrix heat exchanger (MHE) for cryogenic applications. This paper presented a numerical model for the design and thermal analysis of WSMHE. The influence of wall thermal resistance, axial conduction, parasitic heat load and properties variation was taken into account, which is neglected in the traditional effectiveness-NTU method but important for compact cryogenic heat exchangers. The proposed numerical method is verified by effectiveness-NTU method under specific conditions, then it is tested according to experiment data, and a well agreement was obtained. Based on this model, a detailed analysis was performed on WSMHEs. The analysis results show that the axial conduction might result in evident decrease of effectiveness at low flow rate region;the effectiveness of WSMHEs with large flow rate could be remarkably enhanced by increasing its length;the influence of parasitic heat load varied little throughout of the flow rate region. Furthermore, the numerical model presented in this paper can be developed to the design and thermal analysis of small partition wall type heat exchangers. © 2009 Elsevier Ltd. All rights reserved.

关键词： Thermoanalysis

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Flame instability analysis of diethyl ether-air premixed mixtures at elevated pressures

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Chinese Science Bulletin 2010年第3期55卷 314-320页

作者： ZHANG Ni DI YaGe HUANG ZuoHua ZHANG ZhiYuan State Key Laboratory of Multiphase Flow in Power Engineering Xi 'an Jiaotong University Xi 'an 710049 China

Combustion characteristics of premixed diethyl ether-air mixtures were studied at different equivalence ratios and elevated initial pressures using schlieren photography and spherically propagating flame. Laminar burning velocities, Markstein number and critical radii at onset of cellular structure were obtained. The results show that an increase in initial pressure leads to a decrease in the unstretched laminar burning velocities. Laminar burning velocities give their peak values at the equivalence ratio of 1.1. Markstein number decrease with the increase of initial pressure and equivalence ratio, indicating that the instability of flame front is increased with the increase of initial pressure and equivalence ratio. The critical radii at onset of cellular flame structure are decreased with the increase of initial pressure.

关键词：不稳定性分析空气混合物火焰结构压力升高乙醚层流燃烧速度初始压力预混

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Simulation and experimental study of phase isolation induced by a static cyclone device in a vertical upward pipe

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International Journal of Energy for a Clean Environment 2015年第1-4期16卷 139-156页

作者： Wang, Shuai Wang, Dong Niu, Pengman Zhang, Xingkai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The study puts forward a forced way to realize phase isolation by using a static cyclone device and provides a basis for a systematic study of the phase-isolation phenomenon for an oil-water two-phase flow in a vertical upward pipe. An optimized style of the static cyclone device was chosen to simulate the phase-isolation characteristics that are influenced by various flow parameters (density, viscosity, velocity, oil diameter, etc.). It is observed that the phase-isolation characteristics are well approaching the ideal condition with the oil superficial velocity below 0.20 m/s and water superficial velocity between 0.25 and 0.8 m/s. The experimental results, which agree well with the simulation, also show that the static cyclone device can successfully be used to realize phase isolation. The phase-isolation method may provide an innovative approach to the measurement of phase holdup, the process of water reinjection, and the heat and mass transfer rates of a multiphase flow. © 2015 by Begell House, Inc.

关键词： Two phase flow

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Syngas production by photoreforming of formic acid with 2D V_(x)W_(1-x)N_(1.5) solid solution as an efficient cocatalyst

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Frontiers in Energy 2024年第5期18卷 640-649页

作者： Xiaoyuan Ye Yuchen Dong Ziying Zhang Wengao Zeng Bin Zhu Tuo Zhang Ze Gao Anna Dai Xiangjiu Guan International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'an 710049China

Formic acid(FA)is a potential biomass resource of syngas with contents of carbon monoxide(CO,60 wt.%)and hydrogen(H_(2),4.4 wt.%).Among the technologies for FA conversion,the photoreforming of FA has received widespread attention due to its use of green solar energy conversion technology and mild reaction ***,a V-W bimetallic solid solution,V_(x)W_(1-x)N_(1.5) with efficient co-catalytic properties was first and facilely *** CdS was used as a photocatalyst,the activity performance of the V_(0.1)W_(0.9)N_(1.5) system was over 60%higher than that of the W_(2)N_(3) *** computational simulations and experiments showed the V_(0.1)W_(0.9)N_(1.5) had great metallic features and large work functions,contributing a faster photo-generated carrier transfer and less recombination,finally facilitating a great performance in cocatalyst for syngas production in photoreforming *** work provides an approach to synthesizing novel transition metal nitrides for photocatalysis.

关键词： photocatalysis syngas formic acid cocatalyst solid solution

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Experimental study on dynamic mechanism of vortex evolution in a turbulent boundary layer of low Reynolds number

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Journal of Hydrodynamics 2020年第5期32卷 807-819页

作者： Yan-ang Guo Xiang-rui Dong Xiao-shu Cai Wu Zhou School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering Shanghai 200093China

The dynamic mechanism of the vortex generation and evolution process in a fully developed turbulent boundary layer with Reθ=97-194 is experimentally *** this study,a moving single-frame and long-exposure(MSFLE)imaging method and a moving particle image velocimetry/particle tracing velocimetry(M-PIV/PTV)are designed and implemented for measuring the temporal and spatial evolution of vortex cores in both qualitative and quantitative ways,*** the other hand,the Liutex vector,which is a new mathematical definition and identification of the vortex core proposed by Liu’s group,is first applied in the experiment for the structural visualization and quantitative analysis of the local fluid *** results show that an intuitional process of vortex evolution can be clearly observed by tracking the vortex using MSFLE and verify that the roll-up of the shear layer induced by shear instability is the origin of vortex formation in ***,a quantitative investigation in terms of the critical vortex core boundary(size)and its accurate rotation strength is carried out based on the Liutex vector field analysis by M-PIV/*** to statistics of the relation between vortex core size and the rotation strength during the whole process,the physical mechanism of vortex generation and evolution in a turbulent boundary layer of low Reynolds number can be summarized as a four-dominant-state course consisting of the“synchronous linear segment(SL)-absolute enhancement segment(AE)-absolute diffusion segment(AD)-skewing dissipation segment(SD)”.

关键词： Turbulent boundary layer high-and low-speed fluid vortex generation moving single-frame and long-exposure moving particle image velocimetry/particle tracing velocimetry Liutex vector

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Hierarchical growth of a novel Mn-Bi coupled BiVO4 arrays for enhanced photoelectrochemical water splitting

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Nano Research 2019年第3期12卷 575-580页

作者： Lu Wang Jinzhan Su Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering School cf Energy & Power Engineering Xian Jiaotong University Xian 710049 China

Oxygen evolving catalyst (OEC) is a critical determinant for the efficiency of photoelectrochemical (PEC) water splitting. Here we report an approach to depositing a novel manganese borate (Mn-Bi) OER catalyst on BiVO4 nanocone photoanode by photodeposition in sodium borate buffer solution containing Mn(Ⅱ) ions. Due to the spontaneous photo-electric-field-enhancement effect at the vertically oriented BiVO4 nanocone structure, spherical Mn-Bi nanoparticle was selectively photodeposited at the apex of BiVO4 nanocone. Significant improvement of photocurrent was observed for the obtained hierarchical Mn-Bi/BiVO4 photoanode which could be ascribed to enhanced hole injection efficiency, especially in low bias region. It was observed that the injection efficiency of Mn-Bi/BiVO4 is 98% which gave a photocurrent of 0.94 mA/cm^2 at 1.5 V vs. RHE.

关键词： bismuth vanadate photoelectrochemistry solar water splitting oxygen evolution

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Steady state investigation on neutronics of a molten salt reactor considering the flow effect of fuel salt

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Chinese Physics C 2008年第8期32卷 624-628页

作者：张大林秋穗正刘长亮苏光辉 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University School of Nuclear Science and Technology Xi'an Jiaotong University

The Molten Salt Reactor （MSR）, one of the ‘Generation Ⅳ＇ concepts, is a liquid-fuel reactor, which is different from the conventional reactors using solid fissile materials due to the flow effect of fuel salt. The study on its neutronics considering the fuel salt flow, which is the base of the thermal-hydraulic calculation and safety analysis, must be done. In this paper, the theoretical model on neutronics under steady condition for a single-liquid-fueled MSR is conducted and calculated by numerical method. The neutronics model consists of two group neutron diffusion equations for fast and thermal neutron fluxes, and balance equations for six-group delayed neutron precursors considering the flow effect of fuel salt. The spatial discretization of the above models is based on the finite volume method, and the discretization equations are computed by the source iteration method. The distributions of neutron fluxes and the distributions of the delayed neutron precursors in the core are obtained. The numerical calculated results show that, the fuel salt flow has little effect on the distribution of fast and thermal neutron fluxes and the effective multiplication factor; however, it affects the distribution of the delayed neutron precursors significantly, especially the long-lived one. In addition, it could be found that the delayed neutron precursors influence the neutronics slightly under the steady condition.

关键词： MSR steady state neutronics flow effect delayed neutron precursors

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Room-temperature photodeposition of conformal transition metal based cocatalysts on BiVO4 for enhanced photoelectrochemical water splitting

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Nano Research 2020年第1期13卷 231-237页

作者： Lu Wang Tao Zhang Jinzhan Su Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringSchool of Energy&Power EngineeringXi’an Jiaotong UniversityXi’an710049China

Photoelectrochemical(PEC)water splitting using semiconductors offers a promising way to convert renewable solar energy to clean hydrogen ***,due to the sluggish reaction kinetics of water oxidation,significant charge recombination occurred at the photoanode/electrolyte interface and cause decrease of its PEC *** reduce the surface recombination,we deposit different transition metal complexes on BiVO4 nanocone arrays by a versatile light driven in-situ two electrode photodeposition approach without applied *** cobalt phosphate“Co-Pi”,nickel borate“Ni-Bi”and manganese phosphate“Mn-Pi”complexes were deposited on BiVO4 nanocone arrays to form core-shell structure photoanode,all of which lead to enhanced photoelectrochemical *** photocurrent of the Co-Pi/BiVO4 photoanode under front-side illumination for 5 min is increased by 4 folds comparing to that of bare BiVO4 photoanode at 0.6 V ***,reaching a hole transfer efficiency as high as 94.5%at 1.23 V *** proposed photodeposition strategy is simple and efficient,and can be extended to deposite cocatalyst on other semiconductors with a valence band edge located at a potential more positive than the oxidation potential of transition metal ion in the cocatalyst.

关键词： bismuth vanadate photoelectrochemcial water splitting conformal photodeposition cocatalyst

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