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Chaotic Characteristics Analysis on Recognition of Steam Plume flow Pattern of Direct Contact Condensation in a Rectangular Channel

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Energy Procedia 2017年 142卷 3827-3832页

作者： Binbin Qiu Jia Liu Jiping Liu Junjie Yan Xiaoping Yang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Chaotic characteristics of direct contact condensation(DCC) for steam jet in subcooled water in a rectangular channel were analyzed at subcooled water temperature of 30 ℃. The steam mass flux and Reynolds number of subcooled water were in the range of 250-600kg/(m 2 s) and 78,000-172,000 respectively. Three different flow patterns, bubble flow, oscillation jet and stable jet, were observed. Correlation dimension( D 2 ) changes with flow patterns. For bubble flow, oscillation jet and stable jet, the corresponding correlation dimension values increase and are in the ranges of 9.68~10.30, 10.03~11.17 and 11.10~12.62, respectively. Different flow patterns have different Hurst exponent( H ). From the range of correlation dimensions and Hurst exponents, the flow pattern of steam jet can be recognized without looking the picture of steam plume. This result is very important for flow pattern recognition without the observation windows.

关键词： flow pattern recognition chaotic characteristics correlation dimension Hurst exponent

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Numerical simulation on the performance of axial vane type gas-liquid separator with different guide vane structure

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International Journal of Fluid Machinery and Systems 2017年第1期10卷 86-98页

作者： Yang, Fan Liu, Ailan Guo, Xueyan School of Energy and Power Engineering University of Shanghai for Science and Technology No. 516 Jungong Road Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of S hanghai for Science and Technology No. 516 Jungong Road Shanghai200093 China

In order to obtain high efficiency and low resistance droplet separation apparatus, axial vane type gas-liquid separators with different guide vanes were designed, and the RNG k-Ε model as well as discrete phase model (DPM) were used to investigate the flow pattern inside the separators. It was shown that the tangential velocity distribution under different guide vanes have Rankine vortex characteristics, pressure distribution exhibits a high similarity which value becomes big as the increase of the blade outlet angle and the decrease of the guide vane numbers. The increase of the guide vane numbers and the decrease of the blade outlet angle could make separation improve significantly. The separation efficiency is almost 100% when the droplet diameter is bigger than 40μm. © 2017, Turbomachinery Society of Japan. All rights reserved.

关键词： Numerical models

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Optimal design of guide vane inthe cyclone vortex finder based on orthogonal analysis 12

Optimal design of guide vane inthe cyclone vortex finder bas...

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12th International Conference on Fluidized Bed Technology, CFB 2017

作者： Huang, Zhong Liu, Ming Liu, Guanjie Wang, Fengyang Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering Xi 'an Jiaotong University Xi 'an710049 China State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing100084 China China Huaneng Clean Energy Research Institute Beiijing102209 China

A new structure of installing guide vane inside eccentric vortex finder of cyclone was proposed. Five parameters including eccentric ratio e, blade number Z, hub inlet installing angle p, middle coefficient of hub installing angle k, shroud inlet installing angle increment Ap were selected to design an orthogonal table of five elements and four levels. Based on RNG k-e model, separation efficiencies of the conventional cyclone and 16 cyclones installing guide vanes inside vortex finder were calculated. By means of orthogonal analysis, the influence of each element has been ranked, and the optimal level of each element has been combined as the optimal structure. The simulation result indicated that the separation efficiency of the optimal structure has increased up to 7.04% while the pressure drop decreased no more than 12.5%. The flow field analysis showed the velocity in the inner vortex of cyclone was lower, while it was higher in the outer vortex, which is of great help for particle separation.

关键词： Vortex flow

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Experimental Study on Cohesiveness Characteristics of Raw Cement Ash at Moderate Temperature

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Energy Procedia 2017年 105卷 4674-4679页

作者： Tao Han Chang’an Wang Qi Cao Wufeng Chen Defu Che State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Raw cement ash deposition in SP boilers gives rise to serious operation problems. In the present, mechanism of raw cement ash deposition is still unclear because the ash components, gas atmosphere and gas temperature are quite different from existing studies. The characteristics of cohesiveness of raw cement ash in moderate temperature were investigated in a lab-scale electric furnace. Three typical raw cement ashes were selected as samples, three base plates, including rough steel plate, smooth steel plate, organic glass plate were studied. Ball-impacting method was adopted to evaluate the cohesiveness of ash. Experimental results show that, the ash cohesiveness is mainly dependent on the components of ash, and the material property of base plate, while it exhibits little relationship with the roughness of the plate surface. Low-melting substances appear during ash deposition on steel plate. The results reveal that ferrum possibly has catalytic to some low-melting substances forming.

关键词： deposition cohesiveness roughness low-melting sunbstances

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Ash Deposition and Alkali Metal Migration during Zhundong High-alkali Coal Gasification

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Energy Procedia 2017年 105卷 1350-1355页

作者： Guangyu Li Chang’an Wang Pengqian Wang Yongbo Du Xuan Liu Wufeng Chen Defu Che State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Ash deposition is particularly serious during Zhundong coal combustion/gasification due to its high alkali metal content, which causes great troubles and limits its utilization. This paper focuses on the ash deposition characteristics and migration disciplinarian of akali metal during Zhundong coal gasification varing with different conditions, such as ash deposition temperature, gasification temperature, O 2 /coal, steam/coal, and deposition time. Experimental result indicates that gasification conditions play a significant role on ash deposition. The root cause of severe fouling is the high content of Na in Zhundong coal, most of which is water-soluble. Besides, the contents of Na, Fe, S, Cl in ash are obviously changed with flue gas temperature increasing, indicating these elements have great influence on ash deposition, and the migration of Na, Fe and Cl presents similar variation during deposition. In addition, Na deposits mainly above 873 K, and Fe gains enrichment in ash at various temperatures. With the increase of gasification temperature, the content of Na in the ash is increased, which could exacerbate ash deposition. Both O 2 /coal and steam/coal have a certain influence on migration of elements, and the increases of O 2 /coal and steam/coal can relieve the ash fouling phenomena. Deposited ash on heating surface will react with Na in flue gas at high temperature, leading to the increase of content of Na in the ash with deposition time increasing.

关键词： Coal gasification Zhundong coal alkali metal ash Deposition

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Effect of prompt dissociation of formyl radicals on 1,3,5-trioxane laminar flame speeds at high pressure 55

Effect of prompt dissociation of formyl radicals on 1,3,5-tr...

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55th AIAA Aerospace Sciences Meeting

作者： Zhao, Hao Fu, Jiapeng Ju, Yiguang Department of Mechanical and Aerospace Engineering Princeton University Engineering Quad Olden Street PrincetonNJ08544 United States Department of Power Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

ISBN: (纸本)9781624104473

Flame speeds of all hydrocarbon fuels are very sensitive to the reactions of formaldehyde (CH2O) and formyl radical (HCO). In this paper, we studied the prompt dissociation effect of HCO on the flame speeds of trioxane and formaldehyde up to 9 atm. The effects of prompt HCO dissociation were examined at high pressure. Different kinetic models were compared against the experimental results. The results showed there was a significant effect of the HCO prompt reaction on the flame speed in a broad range of pressure and equivalence ratio. At higher pressure, it was observed that the prompt effect was reduced due to the third-body collision effect. However, with the increase of O2mole fraction, the prompt effect was enhanced. Comparison showed that HP Mech with the inclusion of the prompt reactions had a better prediction at lean and ultra-lean conditions than other mechanisms. The improved prediction of the flame speed indicated that the prompt effect needed to be considered in the model development of hydrocarbon and oxygenated fuel combustion. © 2017 by Hao Zhao, Jiapeng Fu, and Yiguang Ju.

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Insights into Charge Transfer at an Atomically Precise Nanocluster/Semiconductor Interface

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Angewandte Chemie 2020年第20期132卷

作者： Yu Wang Xiao‐He Liu Qiankun Wang Martin Quick Sergey A. Kovalenko Qing‐Yun Chen Norbert Koch Nicola Pinna Institut für Chemie and IRIS Adlershof Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany International Research Center for Renewable Energy (IRCRE) and State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China Institut für Physik and IRIS Adlershof Humboldt-Universität zu Berlin Brook-Taylor-Strasse 6 12489 Berlin Germany

The deposition of an atomically precise nanocluster, for example, Ag 44 (SR) 30 , onto a large‐band‐gap semiconductor such as TiO 2 allows a clear interface to be obtained to study charge transfer at the interface. Changing the light source from visible light to simulated sunlight led to a three orders of magnitude enhancement in the photocatalytic H 2 generation, with the H 2 production rate reaching 7.4 mmol h −1 g catalyst −1 . This is five times higher than that of TiO 2 modified with Ag nanoparticles and even comparable to that of TiO 2 modified with Pt nanoparticles under similar conditions. Energy band alignment and transient absorption spectroscopy reveal that the role of the metal clusters is different from that of both organometallic complexes and plasmonic nanoparticles: A type II heterojunction charge‐transfer route is achieved under UV/Vis irradiation, with the cluster serving as a small‐band‐gap semiconductor. This results in the clusters acting as co‐catalysts rather than merely photosensitizers.

关键词： Ladungstransfer Cokatalysatoren Photosensibilisator Silber-Nanocluster

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Release and Transformation of Potassium during Combustion of Biomass

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Energy Procedia 2017年 142卷 401-406页

作者： Lei Deng Jiaming Ye Xi Jin Tao Zhu Defu Che State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

To investigate the release and transformation of fuel K during combustion of biomass, wheat straw and corn stalk are burnt in a fixed-bed reactor system during 400−1000 °C, and weight measurement, elemental composition analysis, and chemical fractionation analysis are performed. The influences of fuel type, combustion temperature, and water washing pretreatment are discussed. The results show that wheat straw has a higher K release ratio than corn stalk, especially when combustion temperature is above 500 °C. For both biomass fuels, the released K is far less than the water-soluble K. For wheat straw, some of the other occurrence modes of K turn into the insoluble K gradually. For corn stalk, the water-soluble and ion-exchangeable K turn into HCl-soluble and insoluble K. Water washing removes all the water-soluble K of corn stalk and reduces the K release from 3.26 to 0.27 mg g -1 at 1000 °C.

关键词： Potassium release Transformation Biomass combustion Water washing

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A comprehensive model for uniform heat flux inside cavity receiver with air-carbon mixture

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Energy Procedia 2017年 142卷 177-183页

作者： Yabin Jin Jiabin Fang Jinjia Wei Xinhe Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 China

Cavity receiver is one of the main components of efficient concentrating solar collector systems. It has the ability to operate at relatively higher temperature and efficiency. The safety and thermal efficiency of solar cavity receiver can affect the efficiency of the whole power system. However, the non-uniform distribution of heat flux and temperature inside the cavity tends to cause the operation instability and bring damage to the tube as well. In the present work, a comprehensive numerical model was developed by coupling Monte Carlo Ray Tracing (MCRT) and Finite Volume Method (FVM) to simulate the thermal performance of a 2D square solar cavity filled with air-carbon particle mixture. Firstly, the complicated photon transmission in the air-carbon particle mixture absorber is simplified as the transmission process in the statistically homogenous and isotropic turbid media. The solar heat flux distribution from the aperture to the wall is simulated by MCRT, and the photo-thermal convection process in the cavity receiver is modeled by FVM. Then the two parts are coupled in the cavity receiver by transferring the absorbed energy computed by MCRT to FVM, and this energy is applied as a source term of the energy equation in the FVM part. Based on this model, the temperature and heat flux characteristics of the cavity receiver were studied at various carbon densities. The result indicated that the air-carbon particle mixture can actively take part in the radiation and it appears that it has a remarkable effect on the temperature homogenization. It decreases the temperature of wall 3 dramatically and increases the temperature of wall 2 and wall 4. The relationships between the temperature unevenness and the number particle density were also analyzed. The temperature unevenness on the wall 3 drops most with the increase of number density of carbon particle, from 25.0K to 2.4K. The unevenness of temperature on the top and bottom walls also decreases slightly by 3K. In ad

关键词： solar cavity receiver non-uniform air-carbon particle mixture homogenization Monte Carlo ray tracing Finite volume method

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Flame brush thickness of premixed turbulent flames: Hydrodynamic theory versus experiments 9

Flame brush thickness of premixed turbulent flames: Hydrodyn...

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9th International Conference on Modeling and Diagnostics for Advanved Engine Systems, COMODIA 2017

作者： Zhang, M. Patyal, A. Fogla, N. Wang, J.H. Huang, Z.H. Matalon, M. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States

The effect of varying turbulence intensities on the flame brush thickness is investigated numerically using a hybrid Navier-Stokes/front-tracking methodology in the context of the hydrodynamic theory. Two configurations, namely planar and Bunsen, are chosen with the latter used for direct comparison with experimental OH-PLIF Bunsen flame images. The Darrieus-Landau influences are controlled through the mixture Markstein length and the flame brush is analyzed under two regimes, sub- and supercritical based on the absence/presence of the hydrodynamic instability. In the planar configuration at low intensities, the sub-critical flame brush retains its near flat shape, while the super-critical flame brush forms a highly corrugated structure reminiscent of the cusped-like flames that result in the laminar setting. With increasing turbulence levels, these effects start to gradually diminish as the flame becomes dominated by velocity fluctuations arising from the turbulent field, finally leading to nearly identical behavior in both regimes for very high intensities. Unlike the planar flame, the sub-critical Bunsen flame surface is dominated by large wrinkles with a more rounded shape while the super-critical flame highlights the formation of cusp-like structures on its surface. Numerical verification of the Bunsen flame brush thickness shows a good qualitative match with experimental tests for turbulent CH4/air flames. The good agreement indicates the qualitative prediction capabilities of the hydrodynamic model. Copyright © 2017 by the Japan Society of Mechanical Engineers.

关键词： Navier Stokes equations

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