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International Conference on power engineering, ICOPE 2015

作者： Mu, Qiwei Han, Xiaoqu Wang, Bingqi Yan, Junjie Chen, Weixiong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Consisting of steam cooler, condensation zone and drain cooler, the three-stage feedwater heater is widely used in the thermal power plants. To study the variable condition characteristics of three-stage feedwater heater with water level controlled, a GSE simulation model of that in 300MW thermal system of power plant was established. Validated by the steady states of the heater, different dynamic characteristics were investigated when the load varied. The results revealed that the steam pressure, feedwater flow and feedwater inlet temperature drops would have a significant influence on the extracting steam flow, feedwater temperature increment and terminal temperature difference. The dynamic trends were intensified with the variation of the input condition enhanced. The response time of extracting steam pressure drops is 430s and that of feedwater flow drops would be prolonged to 600s. The dynamic processes with water level controlled were carried out and showed that adjusting flow valve could keep the water level stable and secure the operation of heater smooth and steady. However, frequently controlling the position of flow valve could impair the steady procedures of other parameters and prolonged the response time. © 2015 The Japan Society of Mechanical Engineers.

关键词： Water levels

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Thermal-diffusive instabilities of laminar premixed CH4/H2/air flat flames 10

Thermal-diffusive instabilities of laminar premixed CH4/H2/a...

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10th Asia-Pacific Conference on Combustion, ASPACC 2015

作者： Jin, Wu Wang, Jinhua Yu, Senbin Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

As one of the most promising clean alternative fuels, natural gas has been widely used in automobile engines. However, due to the slow burning velocity of natural gas and its poor lean-burn ability, hydrogen is often added to improve its combustion behavior. Researches on the fundamental laminar premixed flame characteristics of CH4/H2 blends are of great significance to understand the combustion process in practical combustors. The intrinsic instability of laminar flame is one of the classic issues in flame dynamics, which presents the dynamic response of laminar premixed flamelets to weak perturbations. By studying dynamic mechanism of intrinsic instability, we can estimate the burning velocity more accurately and gain a deeper insight into the turbulent combustion process in spark ignition engines. In this study, the cellular instabilities of laminar premixed CH4/H2/air flat flames were studied using McKenna burner with OH-PLIF technique. It was found that the addition of H2 can broaden the lean combustion limit on flat flame burner with which the cellular instabilities were brought. The digital and OH-PLIF images were obtained to calculate the quantitative parameters of cellular length scale, which is associated with the properties of fuel mixtures such as Lewis number, Markstein number et al. Through the theoretic analysis, we make a thorough investigation on the mechanism about how the cellular scales were determined.

关键词： Natural gas

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Dynamics of Internal Jets in the Merging of Two Droplets of Unequal Sizes

Dynamics of Internal Jets in the Merging of Two Droplets of ...

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第八届海峡两岸激波与复杂流动学术会

作者： Chenglong Tang Jiaquan Zhao Peng Zhang Chung K.Law Zuohua Huang Department of Mechanical and Aerospace Engineering Princeton University State Key Laboratory of Multiphase Flow and Power Engineering Xi'an Jiaotong University Department of Mechanical Engineering Hong Kong Polytechnic University Center for Combustion Energy Tsinghua University

*** Collision of two droplets in a gaseous environment plays an essential role in many natural and industrial processes,such as raindrop and cloud formation,insecticide spraying,spray painting,and spray combustion in various liquid-fueled *** the most symmetrical event,namely the head-on collision between two identical droplets,it has been experimentally and theoretically-demonstrated that,

关键词： simulation Dynamics of Internal Jets in the Merging of Two Droplets of Unequal Sizes

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Study on particle and photonic flux distributions in a magnetically stirred photocatalytic reactor

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Journal of Photonics for Energy 2015年第1期5卷

作者： Ren, Yuxun Jing, Dengwei Xi'An Jiaotong University International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering 28 Xianning West Road Xi'an Shaanxi710049 China

When dispersed in water, nanoscale photocatalysts can aggregate into microscale secondary particles due to their high surface energy. The interaction between the incident photons and the aggregated particles is expected to be significantly changed due to their comparable length scales. Hydrodynamics of the particles after aggregation and the resultant photonic flux distributions in slurry photocatalytic reactors are therefore essential. The magnetically stirred photocatalytic reactor is compact and simple for fabrication, and therefore can be readily employed in lab-scale photocatalytic tests. However, studies toward its optimization are rare. In our study, the photocatalyst distribution was simulated using a Eulerian-Lagrangian approach, while the evolution of free liquid surface led by magnetic stirring was modeled by volume of fluid method. Subsequently, based on the photocatalyst distribution, the photonic flux distribution was obtained through a mean free path-based Monte Carlo method. Outcomes suggest that at a stirring speed of 900 rpm, the 10 μm particles can be well suspended, and a moderate free liquid surface will also be present. Moreover, under sufficient stirring, larger catalyst particles are more likely to be densely distributed in the outer region, which contributes to an increase in the overall photonic absorption even higher than the one with evenly distributed photocatalysts. © The Authors.

关键词： Computational fluid dynamics

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2279. Influence of tilting rotor on characteristics of fluid-induced vibration for labyrinth seals

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Journal of Vibroengineering 2016年第8期18卷 5416-5431页

作者： Zhang, Wanfu Zhang, Yao Yang, Jiangang Li, Chun School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China National Engineering Research Center of Turbo-Generator Vibration Southeast University NanjingJiangsu Province210096 China

Labyrinth seal is a key component for the safe and reliable operation of a turbine unit. This paper sets up a three-dimensional numerical model of a labyrinth seal with a tilting rotor based on a compressor eye seal which was studied by Computational Fluid Dynamics method and a test labyrinth seal. The influence of the tilting rotor on the static and dynamic characteristics of labyrinth seals was investigated. Numerical results demonstrated a good agreement with the published article. Both the radial and tangential fluid-induced forces show an obvious increase when the rotor is in tilting conditions. From an efficiency viewpoint, a bigger tilt angle of the rotor is desirable. And eccentricity existence is not beneficial to the seal performance. The results based on the test seal show the whirl frequency ratio increases with the increasing eccentricity ratio. In case of tilting conditions (δ = 0.05 mm, θ = 0.8 deg), the whirl frequency ratio decreases with the increasing rotational speed. The higher rotational speed will be beneficial to the stability improvement when the rotor is in tilting conditions. The whirl frequency ratio also shows a decrease with the increasing inlet pressure. The higher inlet pressure tends to improve the stability when the rotor is in tilting conditions. All the stiffness coefficients and damping coefficients increase as the tilt angle increases. The whirl frequency ratio also shows an increase with the increasing tilt angle. The tilting rotor tends to reduce the stability when the rotor is in eccentric conditions. © JVE INTERNATIONAL LTD.

关键词： Computational fluid dynamics

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Energy Storage: In Situ Fabrication of Hierarchically Branched TiO2Nanostructures: Enhanced Performance in Photocatalytic H2Evolution and Li–Ion Batteries (Small 47/2017)

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Small 2017年第47期13卷

作者： Guorui Yang Ling Wang Shengjie Peng Jianan Wang Dongxiao Ji Wei Yan Seeram Ramakrishna Department of Environmental Science & Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Mechanical Engineering National University of Singapore Singapore 117574 Singapore Jiangsu Key Laboratory of Materials and Technology for Energy Conversion College of Materials Science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

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Heat transfer and pressure drop characteristics of condensation for R410A in a 3.78mm circular tube under normal and micro gravity

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ASME 2016 Heat Transfer Summer Conference, HT 2016, collocated with the ASME 2016 Fluids engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels

作者： Zhang, Jingzhi Shih, Tom I.-P. Shi, Yanping Li, Wei Zhang, Yonghai Niu, Yuzhen Department of Energy Engineering Zhejiang University Hangzhou Zhejiang China Department of Energy Engineering Collaborative Innovation Center of Advanced Aero-Engine Zhejiang University Hangzhou Zhejiang China School of Aeronautics and Astronautics Purdue University West LafayetteIN47907 United States Shanxi FTEC Engineering Co. Ltd. Taiyuan Shanxi China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shanxi China Hangzhou Fortune Group Co. Ltd. Hangzhou Zhejiang China

ISBN: (纸本)9780791850336

Heat transfer and pressure drop characteristics of condensation for R410A inside horizontal tubes (dh=3.78 mm) under normal and micro gravity are investigated numerically. The Volume of Fluid method is used to acquire liquid-vapor interface, while the low-Reynolds form of the Shear Stress Transport k∼ω (SST k∼ω) model is adopted to taking turbulent effect into account. The results indicate that the heat transfer coefficients decrease with increasing gravity accelerations, while the frictional pressure gradients increase with increases in gravity accelerations. The liquid film accumulates at the bottom of the tube, leading to a very thin liquid film attached to the upper part of inner tube wall. This accumulation effect decreases with decreases in gravitational accelerations. A more symmetrical liquid-vapor interface is obtained at lower gravity. The average liquid film thickness is nearly the same for different gravity accelerations at the same vapor quality (8ave=56 μm at x=0.9 and 8ave=230 μm at x=0.5). The local heat transfer coefficients increase with increasing gravity at the top of the tube and decrease with increases in gravity at the bottom, while the bottom part of the tube has a limited contribution to the global heat transfer coefficient for stratified flow regime. The numerical data obtained under normal gravity agree well with well-known empirical correlations. Copyright © 2016 by ASME.

关键词： Condensation

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Investigation on flow boiling heat transfer characteristics of water in vertically-upward spirally-ribbed tubes under subcritical pressures

Investigation on flow boiling heat transfer characteristics ...

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International Conference on power engineering, ICOPE 2015

作者： Zhang, Weiqiang Li, Huixiong Zhang, Qing Zhang, Qian Kong, Xiangfei Wu, Jinkai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xianning West Road 28 Xi'an710049 China

Series of experiments have been performed at different pressures from 12 to 19 MPa, mass velocities from 400 to 1000 kg·m-2· s-1, inner wall heat fluxes from 300 to 500 kW· m-2 and bulk fluid enthalpy from 800 to 3100 kJ·kg1, to study flow boiling heat transfer characteristics of water in seven vertically-upward spirally-ribbed tubes with different rib structures. Based on the experimental results, effects of pressure, mass velocity and heat flux on flow boiling heat transfer coefficient (HTC) were discussed. It was found that, saturated flow boiling HTC was nearly invariable with an increase in mass velocity, but it increased distinctly with the increase in heat flux. As the pressure increased, the flow boiling HTC increased. Some existing correlations for predicting flow boiling HTC of water in the spirally-ribbed tubes were evaluated with the test data collected from open literatures and obtained in this experiment. On the basis of experimental results of flow boiling heat transfer from open literature and internal report, a new universal correlation for the flow boiling HTC of subcritical pressure water was developed for spirally-ribbed tubes with different rib structures, by introducing suitable dimensionless quantities of the spirally-ribbed tube structures to the existing empirical correlations. It was shown that the values calculated by the new correction are in good agreement with the experimental data for the two new-type spirally-ribbed tubes, indicating that the newly proposed universal correlation could provide good support for the application of the vertically-upward spirally-ribbed tubes. © 2015 The Japan Society of Mechanical Engineers.

关键词： Heat flux

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Development of cladding oxidation analysis code [COAC] and application for early stage severe accident simulation of AP1000

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Progress in Nuclear Energy 2015年 85卷 352-365页

作者： Mao, keyou Wang, Jun Li, Longze Zhang, Yapei Tian, Wenxi Su, Guanghui Qiu, Suizheng Corradini, Michael L. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China College of Engineering University of Wisconsin-Madison Madison 53706 United States

Abstract Clad oxidation is an important phenomenon which can affect core degradation under severe accident conditions. The oxidation process always coincides with cladding material embrittlement. The energy released from the oxidation of cladding material can accelerate the accident process, and the hydrogen released from oxidation may threaten the integrity of vessel. As a consequence, the high temperature clad solid-phase oxidation model research and its code development play an important role in reactor safety analysis. To push the research on this region, a clad solid-phase oxidation analysis code (COAC) is developed by Xi'an Jiaotong University. To verify the quality of COAC, CORA-13 is used as a benchmark. The results show that COAC does produce expected values. COAC is then applied to AP1000 severe accident calculations. In this case, the station blackout accident (SBO) is modeled. The response of fuel rods under varying natural circulation conditions while coolant pump idle time is calculated. The calculations show that the oxidation of cladding can delay fracturing, and protect its integrity. Meanwhile, the performances of other oxidation models are explored in this paper. © 2015 Elsevier Ltd.

关键词： AP1000 Clad solid-phase oxidation models COAC Hydrogen generation rate

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Dicyanovinyl-unit-induced absorption enhancement of iridium(III) complexes in long-wavelength range and potential application in dye-sensitized solar cells

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Science China Chemistry 2015年第4期58卷 658-665页

作者： Dongdong Wang Hua Dong Xiaoyu Zhang Yong Wu Shaohua Shen Bo Jiao Zhaoxin Wu Min Gao Geng Wang Department of Applied Chemistry School of Science Xi’an Jiaotong University Key Laboratory for Physical Electronics and Devices of the Ministry of Education School of Electronic and information Engineering Xi’An Jiaotong University Key Laboratory for Advanced Materials Institute of Fine Chemicals and Department of Chemistry East China University of Science and Technology International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

Iridium complexes with dicyanovinyl-grafted phenylpyridine/l-phenylisoquinoline as ligands are synthesized and their photo- physical, electrochemical, and sensitization properties in DSSCs are investigated. The iridium complexes present significantly enhanced absorption from 400 to 525 nm. The 1-phenylisoquinoline-based iridium complex show bathochromic-shift emission in DMSO solution compared with their phenylpyridine-based counterpart, while their absorption response and photoluminescence peak in solid show little difference despite extension of the conjugated system. Using DSSCs, the conversion efficiency of 0.62% and open-circuit current of 1.4 mA/cm2 is achieved. The poor performance is attributed to the excited-state properties of iridium complexes according to the TD-DFT calculation.

关键词： dicyanovinyl group iridium complexes absorption response dye-sensitized solar cell

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