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Study on the characteristics of flowing organization in DMFC. Part II: A new scheme with plates staggered installed

Taiyangneng Xuebao/Acta Energiae Solaris Sinica 2008年第10期29卷 1247-1251页

作者： Yin, Benhao He, Yaling Li, Xianglin Miao, Zheng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Based on the investigations on the influences of geometrical parameters and symmetrical plates disposal scheme on DMFC performance, a new scheme that staggered channels arrangement was presented and studied in this work. The characteristics of fluid flow, proton transport and reaction rate distribution were well studied and contrasted to symmetrical scheme used in a cell unit. The effects of thickness of catalyst layer, backing layer and membrane on cell local average current density were investigated. After optimized design, a staggered scheme was put forward, and the higher potential output and greater limiting current density were obtained compared to the conventional symmetrical scheme. A new way to optimizing DMFC design and assembly was put forward.

关键词： Geometry

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PIV measurement of turbulent mixing layer

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2008年第11期29卷 1867-1871页

作者： Guo, Fu-De Chen, Bin Wang, Zhi-Wei Guo, Lie-Jin Zhang, Xi-Min State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In present paper a turbulent mixing layer with the velocity ratio 4:1 which was produced by a special designed splitter plated placed in a vertical rectangular channel was experimentally investigated by PIV. The Reynolds number based on the velocity difference of two steams and hydraulic diameter of the channel ranges from 4400-158400. It is found that the scale of coherent vortex structure increases with increasing the Reynolds number and then decreases with continuously increasing the Reynolds number. The injected bubble will delay or hinder the evolution of the coherent structures. Afterwards the statistical and instantaneous distributions of Reynolds stress, turbulent intensity, vorticity and swirling strength are obtained. The results show that all these turbulent parameters exist only in a very narrow conical region in the downstream of the mixing layer. The Reynolds stress and turbulent intensity first increase and then decrease with increasing the Reynolds number and decrease with the evolution of mixing layer, while vorticity and swirling strength increase with increasing the Reynolds number and decrease with the evolution of mixing layer.

关键词： Reynolds number

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Influence of the initial condition on pool water instantaneous flash evaporation

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2008年第8期29卷 1335-1338页

作者： Guo, Ying-Li Deng, Wei Yan, Jun-Jie Wang, Gui-Fang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

An experimental study has been performed to investigate pool water instantaneous flash evaporation in a rectangle chamber. The water level was at 40 mm, 60 mm, 100 mm, 150 mm. Initial conditions of the liquid varied from 55 to 88C temperature and 3 to 35C superheat. Visualization of the phenomenon using a CCD camera lets us firstly point out the influence of the initial conditions on the flashing phenomenon. The experimental results show that at a constant initial water temperature, the greater the superheat approaches, the more quickly the liquid temperature will decrease. At a constant superheat, the initial water temperature has little influence on the decrease rate of the water temperature. The higher the water level will be, the slower the water temperature will decrease as well as the higher the water temperature will be when the flashing is finished. Experimental study allows us to correlate the water temperature with the initial water temperature and the superheat while flashing is going.

关键词： Water temperature

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Measurement of diffusion coefficient using Michelson interferometry

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Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument 2008年第SUPPL. 2期29卷 488-492页

作者： Guo, Ying He, Maogang Zhang, Ying Zhong, Qiu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In this paper, an experimental system for the measurement of mass diffusion coefficient using Michelson laser holographic Interferometry was designed and constructed. The experimental system include: the subsystem of Michelson interferometer, the diffusion cell for the mass diffusion of liquid-liquid, the subsystem of thermostatic water bath, the subsystem of image collecting and image processing. The mass diffusion coefficients of 0.33 molL-1 KCI solution with water at the temperature of 289.15 K were measured, and the result shows that the average of relative deviations is 1.30% compared with the literature values, and it verified the accuracy and reliability of the system. The mass diffusion coefficients of 0.1 molL-1 saccharose with water at 5 different temperature were measured, and the result shows that the biggest relative deviations is within 5% which verified the reliability of the system further.

关键词： Michelson interferometers

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Experimental investigation on the conversion of nitrogenous gas products during coal pyrolysis

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Journal of Fuel Chemistry and Technology 2008年第2期36卷 134-138页

作者： Hai-feng LIU Yin-he LIU Yan-hua LIU De-fu CHE State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The conversion of nitrogenous gas products during coal pyrolysis is investigated in a drop tube reactor. Four raw coals and two demineralized coals have been used for pyrolysis at 500°C, 700°C, 900°C and 1100°C. The results indicate that the yields of N 2 and NO precursors, such as HCN and NH 3 , increase with increasing temperature. Coal type has significant effect on the yield of nitrogenous gas products. For lower rank coal, the conversion of fuel nitrogen is higher. Majority of fuel nitrogen in high rank coals is built into condensed aromatic structures to form Char-N. The mineral matters in coal can promote the conversion of fuel nitrogen to N 2 , but they can also suppress the conversion of fuel nitrogen to HCN and NH 3 .

关键词： coal pyrolysis HCN NH 3 N 2

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Research and application of flow visualization technique in large-scale hydraulic models

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Journal of Physics: Conference Series 2009年第1期147卷

作者： Wen Cheng Bao-wei Hu Tian Wan Zhang-bin Wang Fujio Yamamoto State Key Laboratory of Multiphase Flow in Power Engineering Key Laboratory of Northwest Water Resources and Environmental Ecology of Education Ministry ShaoXing University Shao Xing 312000 China Fiber Amenity Engineering Course Graduate School of Engineering University of Fukui Bunkyo 3-9-1 Fukui 910-8507 Japan Xian Jiao tong University Xian 710049 China Xian University of Technology Xian 710048 China

With the rapid development of computer and optical technique, as a powerful measuring method in hydrodynamics, flow visualization technique is able to get much flow field information in practical engineering. It also has an important meaning to projects and environmental areas. The image processing is the key to flow visualization for gaining flow field information. In terms of the PIV principles, the algorithm of PIV based on Fast Fourier Transformation (FFT) is studied, and the image mosaic program based on genetic algorithm has been compiled. The flow field of seabuckthorn flexible dam has been calculated and analyzed by using those methods as above-mentioned, and in the meanwhile, the application of flow visualization technique to measure the outdoor flow field has been studied exploringly, which proves that it is feasible to apply this technique to measure the large-scale outdoor flow field.

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An Efficient Segregated Algorithm for Incompressible Fluid flow and Heat Transfer Problems - IDEAL (Inner Doubly Iterative Efficient Algorithm for Linked Equations) Part II: Application Examples

引用

Numerical Heat Transfer: Part B -- Fundamentals 2008年第1期53卷 18-38页

作者： Sun, D. L. Qu, Z. G. He, Y. L. Tao, W. Q. wqtao@*** State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi''an Jiaotong University Xi''an Shaanxi People''s Republic of China

In this article, comprehensive comparisons are made between the SIMPLER and IDEAL algorithms for four application examples. It is found that the IDEAL algorithm is efficient and stable not only for the simple, low-Re/Ra or coarse-mesh flow cases, but also for the complex, high-Re/Ra or fine-mesh flow cases. For the low-Re/Ra, coarse-mesh flow cases, the ratio of CPU time of IDEAL to that of SIMPLER ranges from 0.029 to 0.7. For the high-Re/Ra, fine-mesh flow cases, the IDEAL algorithm can obtain convergent results but the SIMPLER algorithm cannot, even though the underrelaxation factors are adjusted. [ABSTRACT FROM AUTHOR]

关键词： ALGORITHMS HEAT transfer FLUID mechanics FLUID dynamics HYDRODYNAMICS

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Theoretical model for interfacial structure in bubble slug

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Shanghai Jiaotong Daxue Xuebao/Journal of Shanghai Jiaotong University 2008年第6期42卷 1009-1012+1016页

作者： Gu, Han-Yang Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China School of Nuclear Science and Engineering Shanghai Jiaotong University Shanghai 200240 China

Slug flow is a highly intermittent flow regime in which large bubble slugs flow alternately with liquid slugs at randomly fluctuating frequency. A one-dimensional model for the interfacial structure in bubble slug was developed based on mass and momentum conservation for bubble nose, body and tail as well as for a hydraulic jump at the rear of the bubble. The model can reproduce experimental results accurately. The results indicate that the interfacial structure is strongly dependent on the Froude number defined by gas/liquid mixture velocity, pipe inclination, and bubble length.

关键词： Gas-liquid flow Interfacial structure One-dimensional model

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A parametric study to design an effective spray cooling deployment in an entrained-flow coal gasifier

A parametric study to design an effective spray cooling depl...

引用

25th Annual International Pittsburgh Coal Conference, PCC

作者： Wang, Qiu Liu, Peiyao Xu, Shisen Wang, Baomin Wang, Ting State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China Thermal Power Research Institute Xi'an Shaanxi China Energy Conversion and Conservation Center University of New Orleans New Orleans LA 70148 United States

ISBN: (纸本)189097725X

Gasification is a clean technique that converts coal into syngas, which can be cleaned much more easily than the coal itself. The raw sysgas exiting the gasifier is usually at a very high temperature. To protect the rearward equipment, the raw syngas needs to be cooled to allow appropriate cleaning of particulates, ashes, and sulfur before it exits the gasifier. Cooling of the syngas can be performed by employing heat exchangers or direct spray cooling. This paper focuses on conducting a 3-D CFD parametric study to aid in the design of an effective water spray cooling deployment. The studied parameters include water droplet sizes (100400m) and water injection angles. The goal is to cool the syngas from 1550C to 800C using the shortest spray section. The gasifier is designed to produce methanol at a full load condition, so the amount of sprayed water is fixed to ensure the syngas composition meets the specifications for methanol production. The gasifier is steam-oxygen blown with dry coal feed using approximately 960 tons per day. The results reveal that smaller droplets are effective in reducing the cooling section length. Moreover, using three water injection angles show that inclining the spraying angle upward 45 degrees could shorten the effective cooling length. This study provides a guide for cutting the cost of manufacturing a gasifier cooling section.

关键词： Coal

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Analysis of impedance with different discharge current in proton exchange membrane fuel cell

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Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2008年第5期42卷 622-625页

作者： Shang, Dehua Ma, Bin Zhang, Guangsheng Guo, Liejin Liu, Hongtan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Mechanical Engineering University of Miami Coral Gables FL 33124 United States

Considering the fact that proton exchange membrane (PEM) fuel cell has different impedance performances under different discharge currents, a PEM fuel cell with single serpentine flow field was investigated with electrochemical impedance spectroscopy, and the R (QR) equivalent circuit was used to calculate the circuit element parameters. The experimental results show that water in the fuel cell increases from insufficient to sufficient and then excessive with the increasing discharge current. Accordingly, the electrochemical reaction rate on the electrodes increases first and then decreases, thus the charge transfer resistance decreases and then increases. The impedance of PEM fuel cell increases obviously for high discharge currents due to the accessional impedance produced by double-layer effect, while the impedance reaches minimum at medium discharge current (5 A).

关键词： Proton exchange membrane fuel cells (PEMFC)

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