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Improved axisymmetric lattice Boltzmann scheme

Physical Review E 2010年第5期81卷 056707-056707页

作者： Q. Li Y. L. He G. H. Tang W. Q. Tao National Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 China

This paper proposes an improved lattice Boltzmann scheme for incompressible axisymmetric flows. The scheme has the following features. First, it is still within the framework of the standard lattice Boltzmann method using the single-particle density distribution function and consistent with the philosophy of the lattice Boltzmann method. Second, the source term of the scheme is simple and contains no velocity gradient terms. Owing to this feature, the scheme is easy to implement. In addition, the singularity problem at the axis can be appropriately handled without affecting an important advantage of the lattice Boltzmann method: the easy treatment of boundary conditions. The scheme is tested by simulating Hagen-Poiseuille flow, three-dimensional Womersley flow, Wheeler benchmark problem in crystal growth, and lid-driven rotational flow in cylindrical cavities. It is found that the numerical results agree well with the analytical solutions and/or the results reported in previous studies.

关键词： Distribution functions

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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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Numerical simulation of subcooled boiling water at low pressure incorporating homogeneous MUSIG model

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AIP Conference Proceedings 2010年第1期1207卷 986-991页

作者： E. F. Chen Y. Z. Li X. H. Cheng Lei Wang aSchool of Energy and Power Engineering Xi’an Jiaotong University China bState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China cSchool of Energy and Power Engineering Xi’an Jiaotong University China dSchool of Energy and Power Engineering Xi’an Jiaotong University China

Applying a three‐dimensional two‐fluid model coupled with homogeneous MUSIG approach, numerical simulations of subcooled water at low pressure were performed on the computational fluid dynamics code CFX‐10 with user defined FORTRAN program. A modified bubble departure diameter correlation based on the Unal semi‐mechanism model was developed. The water boiling flow experiments at low pressure in vertical concentric annulus from reference were used to validate the models. Good quantitative agreement with the experimental data is obtained, including the local distribution of bubble diameter, void fraction, axial liquid and vapor velocity. The results indicate that local bubble diameter first increases and then decreases due to the effect of bubble breakup and coalescence, and has the maximum bubble diameter along the radial direction. Moreover, the peak void fraction phenomenon in the vicinity of the heated wall is predicted at low pressure, which is developed due to the surface tension between vapor bubbles and heated wall.

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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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Experimental Research on the Performance of Exhaust Steam Reclaim Device With a Swirling flow Vane

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AIP Conference Proceedings 2010年第1期1207卷 374-379页

作者： X. L. Li J. J. Yan P. F. Zhang J. J. Yang J. P. Liu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University P.R. China

This paper experimentally studied the performance of exhaust steam reclaim device with a swirling flow vane at different inlet water pressures, temperatures, different inlet steam pressures and different distances between the throat and spout. The results indicated that the injection coefficient decreased as the inlet water pressure and temperature increased, respectively. There is a best distance between the throat and spout which makes the injection coefficient reached to its maximal value at the same experimental pressure and temperature, and the value equals to 130 mm in our experimental system. The resistance coefficient has a minimum value which makes the device have the highest outlet water pressure. Compared with the device without a swirling flow vane, it improves the heating performance for higher injection coefficient and exergy efficiency.

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Experimental Study on the Treatment of low C/N ratio disposal of sewage with BAF

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AIP Conference Proceedings 2010年第1期1207卷 157-161页

作者： W. J. Wang T. Ma W. Cheng aKey Laboratory of Northwest Water Resources and Environmental Ecology of Education Ministry Xi’an University of Technology Xi’an 710048 China bState Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiao tong University China

The Biological Aerated Filter (BAF) is a simple, high‐efficient, low‐consumptive for new biological membrane method correspond to the situation of china, will be one of the main technical measures to solve the progressive deterioration of water environment problem faced china especially medium and small towns. This paper focuses on the experimental study and mechanism analysis in which the up flow, cocurrent gas‐water, single‐stage BAF was adopted on treatment domestic wastewater, the results showed that BAF has good performance in treating domestic sewage, and it had steady treatment effect with different pollution loads.

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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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THE VELOCITY FIELD OF multiphase flow AND EFFICIENCY OF BIOLOGICAL AERATION FILTER

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Journal of Hydrodynamics 2010年第2期22卷 260-264页

作者： CHENG Wen HU Bao-wei YANG Chun-di CHENG Wen-juan Environment Research Institute Xian University of Technology Xi＇an 710048 China State Key Laboratory of Multiphase Flow in Power Engineering Xi＇ an Jiaotong University Xi＇an 710049 China Key Laboratory of Northwest Water Resources and Environmental Ecology of Education Ministry Xi＇anUniversity of Technology Xi＇an 710048 China Yuanpei College Shaoxing University Shaoxing 312000 China Environment Research Institute Xi＇an University of Technology Xi＇an 710048 China

Aeration is an important factor affecting the biological aeration *** a set of experiment device specially designed for the purpose,and the particle image velocimetry technique,the velocity field of the gas-liquid two-phase flow is studied under different *** various simulated aeration states were actually applied to the experimental device of sewage treatment,and the results of the numerical simulation were *** final experimental results indicate that the most efficient state occurs when the ratio of water in aeration tank h / w =1,the diameter of capillary tubes d=0.6mm and the velocity of bubbles v=0.3m/s.

关键词： ratio of water diameter of capillary tube bubbles velocity sewage disposal efficiency

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