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Experimental and numerical study on flow separation control in rectangle diffuser

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical engineering 2010年第5期30卷 92-99页

作者： Xie, Yong-Hui Fan, Tao Zhang, Di Ye, Dong-Ting Wang, Shun-Sen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 Shaanxi Province China

To investigate the mechanism of active control for flow separation in rectangle diffuser by vortex generator jets (VGJs) method, numerical analysis with large-eddy simulation and experimental measurement by particle image velocimetry (PIV) were carried out for the flow field. The numerical results show good agreement with experimental data. The two dimensional vortical structure was discussed in detail via the analysis of their velocity and vorticity distribution. Based on the three dimensional identification of vortex, several vortical structure, with emphasis on the dynamic process of its generation and development, was also discussed. The results show that the jet shear-layer vortices evolved from vortex loops to vortex rings as time go on. Horseshoe vortices wrap around the jet nozzle have the strong stability. The counter-rotating vortex pair has mean-flow definition although they may also have unsteady components. Moreover, to investigate the effect of VGJs on separation control, the surface pressure coefficient, the length of separation zone, the flow characteristics in diffuser and pressure power spectra were compared with and without VGJs. It revealed the longitudinal vortices generate at the downstream of jet increase cross-stream mixing of streamwise momentum and then suppress or delay the separation in diffuser. © 2010 *** ***.

关键词： Large eddy simulation

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The concentration measurement of Biomass/Pulverized Coal/Air threephase flow based on electrostatic and capacitive method 6

The concentration measurement of Biomass/Pulverized Coal/Air...

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6th World Congress in Industrial Process Tomography

作者： Zhang, Juan Hu, Hongli Dong, Jun Zhang, Xiao Xu, Tongmo State Key Laboratory of Power Equipment and Electrical Insulation Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Power Engineering and Multiphase Flow Xi’an Jiaotong University Xi’an710049 China

ISBN: (纸本)9780853163220

A system for the phase concentration measurement of biomass/pulverized coal/air threephase flow based on electrostatic sensor and capacitive sensor data fusion in pneumatic conveying fuel system at power stations is developed. Because electrostatic sensor is more sensitive to dilute pulverized coal, while capacitive sensor to biomass, they are used in the measurement of biomass concentration and pulverized coal concentration in biomass/pulverized coal/air threephase flow. flow regimes are identified by HHT of the electrostatic sensor output signal. Under the certain flow regime identified, the dual regression analysis method is applied to work out the biomass concentration and the pulverized coal concentration. The experiment result indicates that the system has high linearity up to 5%. © 2010, International Society for Industrial Process Tomography. All rights reserved.

关键词： Biomass

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A model for calculating heat transfer coefficient concerning ethanol‐water mixtures condensation

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AIP Conference Proceedings 2010年第1期1207卷 367-373页

作者： J. S. Wang J. J. Yan S. H. Hu Y. S. Yang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

The attempt of the author in this research is made to calculate a heat transfer coefficient (HTC) by combining the filmwise theory with the dropwise notion for ethanol‐water mixtures condensation. A new model, including ethanol concentration, vapor pressure and velocity, is developed by introducing a characteristic coefficient to combine the two mentioned‐above theories. Under different concentration, pressure and velocity, the calculation is in comparison with experiment. It turns out that the calculation value is in good agreement with the experimental result; the maximal error is within ±30.1%. In addition, the model is applied to calculate related experiment in other literature and the values obtained agree well with results in reference.

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Research on the Preparation of (CuAg)xIn2xZn2(1−2x)S2 Solid Solution Photocatalysts

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AIP Conference Proceedings 2010年第1期1207卷 1066-1069页

作者： K. Zhang D. W. Jing C. J. Xing L. J. Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China

ZnS‐CuInS2‐AgInS2 solid solution photocatalysts were successfully prepared by co‐precipitation method with heat treatment under different atmosphere ( N2 and H2S). XRD, XRF, UV‐vis, and SEM were used to characterize the prepared photocatalysts, indicated that the composition of result photocatalysts were different from each other and also the rate of charge, though they possessed a wurtzite‐type phase structure. The photocatalysts all showed photocatalytic activities for H2 evolution from aqueous solutions containing SO32− and S2− as sacrificial reagents under visible light irradiation with Ru loading, but sample treated under H2S atmosphere performed better, the possible reason was proposed.

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Experimental Study on Total Pressure Distribution for Sonic Submerged Steam Jet

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AIP Conference Proceedings 2010年第1期1207卷 386-390页

作者： D. D. Pan J. J. Yan G. Y. Liu aState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China

Experiments on the condensation of steam jet submerged in the subcooled water were carried out. The water temperature and the inlet steam pressure were in the range of 293 K–343 K and 0.2–0.6 MPa, respectively. Four essential shapes of steam plume were enumerated. According to the comparisons of the pictures of steam plume with the graphs in the same size, the pressure came to maximum value in the contraction spots, except for the double expansion‐emanative shape. Moreover, pressure distributions of the flow field were characterized by means of drawing isobar. Comparison and discussions on the relationship between steam plume and pressure distributions were given. With the increase of temperature, pressure distributions within steam plume became more complex. Radial pressure distributions were classified according to different regions. Comparisons of the pressure distributions at different water temperature and inlet steam pressure were obtained.

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Experimental investigation on some key variables during pool water flash evaporation

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AIP Conference Proceedings 2010年第1期1207卷 380-385页

作者： Y. L. Guo J. J. Yan D. T. Chong J. P. Liu aState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China bDepartment of Power Engineering Xi’an Electric Power College China

An experimental study has been performed to investigate pool water flash evaporation in a rectangle chamber. The water level was at 40 mm, 60 mm, 100 mm, and 150 mm. Initial conditions of the liquid varied from 36 to 88° C temperature and 2.1 to 48° C superheat. The experimental results showed that the initial water temperature, the superheat and the water level are significant to the water temperature transients in flashing process and the value of NEF when flash evaporation calm down. Experimental study allows us to correlate the evolution of water temperature.

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Numerical Simulation of the Behavior of Falling Films on Horizontal Plain Tubes

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AIP Conference Proceedings 2010年第1期1207卷 998-1003页

作者： X. L. Lei H. X. Li aState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

In this paper, a numerical simulation is performed in order to reveal the evaporation heating transfer mechanism of the falling‐film of water on the outer wall of horizontal tubes, and the influence of gas‐water‐solid contact angles on the film distribution on the tube is mainly addressed. The simulation is performed by solving the motion equation of the fluid on fixed three‐dimensional (3D) grid systems, and the so‐called volume of fluid (VOF) method is employed to handle the movement of interface between the liquid and the vapor phase. The numerical results are compared with that of a simplified model and also with the experimental recordings obtained in visualization experiments conducted with tubes made of different materials, and it is shown that the numerical results are in very good agreement with the experimental observation of the falling films, indicating that the numerical methods applied in the present study is correct and accurate. Based on the numerical results, effects of the contact angle, the flow rate, the tube diameter and the liquid feeder height on the falling film behavior are discussed. Generally, the film width increases along with the increase of flow rate or the liquid feeder height, while variation of the film thickness exhibits different features at different conditions, and the contact angle is one of the major factors governing the behavior of the falling films.

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Emission Characteristics and Axial Flame Temperature Distribution of a Circumferential Reverse flow Combustor

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Journal of Energy and power engineering 2010年第7期4卷 9-14页

作者： C. Dong Q.L. Zhou X.G. Zhang P. Sun T.M. Xu S.E. Hui Q.X. Zhao State Key Laboratory of Multiphase Flow in Power Engineering Xi ＇an Jiaotong University Xi ＇an 710049 China

In partially premixed combustion of gas turbine, the combustion temperature should be lowed in order to reduce NOx. One solution is lean premixed combustion. However, the problem is that large excess air ratio may make the combustion unstable. A novel combustor with circumferential reverse flow of fuel gas is proposed for settling this problem. A 10 kw furnace is established to test performance of this combustor. Three factors such as primary air ratio, position of secondary air, total excess air ratio are studied. The emission characteristics and axial flame temperature distribution are studied. Basing on experimental results, the axial flame temperature and NOr emission increase with primary air ratio and axial length of second stream, and decrease with total excess air ratio. When the total excess air ratio is larger than 1.05, the combustor presents a lower temperature field and much lower NOx emission （less than 10 ppm）.

关键词： Partially premixed combustor secondary air distributor NOx emission axial flame temperature experimentalinvestigation.

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Experimental Study of Falling Film on the Outside of Horizontal Tube

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AIP Conference Proceedings 2010年第1期1207卷 238-243页

作者： L. B. Yan H. X. Li B. Guo Y. Q. Zhang Z. Zhang Y. F. Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Evaporating falling film on horizontal tubes has been widely used in desalinization, refrigeration, chemical process industries, and so on. In this paper, the flow characteristics of falling film outside horizontal tubes in horizontal air flows was studied theoretically and experimentally. Two low patterns of the falling film, i.e., droplet flow pattern and columnar flow pattern, were considered. Effects of the velocity of airflow, the flux of falling film flow, the external diameter of tube and the surface property of tube on the falling film flowing characters were investigated. Experimental study indicated that, in a definite flow scale, as the flow increased, the diameters of falling droplets and falling columns of the liquid enlarged, and the liquid film became thick and the area covered by the liquid film increased. As the air velocity increased, the offset of the droplet and the column to the top of the tube enlarged, and the rate of increase come down until it complete depart from the the top of the horizontal tube. Besides, a theoretical model was established about the offset of the droplet and liquid column from the top of the tube under the force of the horizontal air flows, and the model was validated by a comparison between the numerical predictions and experimental data.A further analysis about the excursion law of falling film flow outside horizontal tube was also made at the last paprt of the paper.

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Slagging characteristics on the superheaters of a 12 MW biomass-fired boiler

Slagging characteristics on the superheaters of a 12 MW biom...

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作者： Niu, Yanqing Tan, Hongzhang Ma, Lin Pourkashanian, Mohamed Liu, Zhengning Liu, Yang Wang, Xuebin Liu, Haiyu Xu, Tongmo State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xian Jiaotong University Xian 710049 China School of Process Environmental and Materials Engineering University of Leeds Leeds LS2 9JT United Kingdom

In an attempt to understand the problem of severe slagging in biomass-fired boilers, slags formed on the fourth-, second-, and first-stage superheaters in a 12 MW biomass-fired grate furnace have been collected, sampled, and analyzed using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques. The slag collected on each superheater has a unique morphology and structure. The slag on the fourth-stage superheater is loose and porous, while on the secondary and the primary superheaters, the slag shows a clear layered structure of different colors and levels of hardness. Aluminosilicate is the major component in the slag on the fourth-stage superheater, which is formed by Si, Al, and alkali species. On both the secondary and primary superheaters, the sticky sylvine, potassium calcium sulfate, and aphthitalite in the bottom layer trap coarse, large particles, resulting in further slagging. In the alternating layers, the particles containing high concentrations of K, Na, and Cl form the initial deposit layer, the yellow layer in the secondary superheater. Then, it traps the coarse, large particles containing high Si, Al, Ca, Mg, and Fe to form the brown layer. Similarly, the particles in the pale-yellow layer of the primary superheater containing high concentrations of K, Na, and Cl form the initial deposit layer, and then, it traps the coarse, large particles containing high Si, Al, Ca, Mg, and Fe to form the black layer. Accompanied by the periodic blowing, the alternating layer is formed and the slag gradually becomes thicker. © 2010 American Chemical Society.

关键词： Iron

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