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Atmospheric Pb levels over Mount Qomolangma region

Particuology 2009年第3期7卷 211-214页

作者： Renjian Zhang Zhenxing Shen Han Zou Key Labaratory of Regional Climate-Environment Research far Temperate East Asia (REC-TEA) Institute of Atmaspheric Physics Chinese Academy of Sciences Beijing 100029 China State Key Laboratory of Multiphase Flaw in Power Engineering Deportment of Environmental Science and Engineering Xi'an Jiaotong University Xi'An 710049 China

The Pb spectral concentration of atmospheric aerosol samples observed over Mount Qomolangma site （28° 11＇33＂N, 86°49＇S9＂E, 4950m ASL） in 2002 was 13.3 ng/m^3, about 4.5 times higher than that in 2000. The Pb spectral distribution showed three peaks, located at 〈0.25 μm, 0.5-1 μm, and 4-8 μm in diameters. The peaks for 〈0.25 μm and 0.25-0.5 μm may be due to long-distant transport, while that for 4-8 μm probably results from local floating dust. The atmospheric Pb concentration over Mount Momolangma was lower than that of South Pole, most of the urban areas, and desert areas in the northern hemisphere. The enrichment factors for fine and coarse particles of atmospheric Pb in 2002 over Mount Qomolangma were 413.2 and 62,6, respectively, in support of the slight atmospheric pollution with Pb over the Qinghai- Tibetan Plateau.

关键词： Pb Mount Qomolangma Enrichment factor

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Modeling and optimization for increasing propylene in FCC gasoline secondary reactions process based on LM/SVM method

Modeling and optimization for increasing propylene in FCC ga...

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The 5th Joint China/Japan Chemical engineering Symposium

作者：周小伟杨伯伦袁俊 Department of Chemical Engineering State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University

To improve the efficiency of parameters selection for support vector machines(SVM),a novel method of Levenberg-Marquardt(LM) algorithm coupling with SVM,called LM/SVM,was developed in this *** new method was applied in modeling and optimization for increasing propylene in secondary reaction of FCC *** LM algorithm was adopted in LM/SVM method to optimize the multiple parameters of the SVM model as to overcome the problem of difficult to selecting the parameters for SVM and to fit relational expression of high *** strategy which divided the training data into working data to train SVM and the testing data to avoid over-fitting was *** of LM/SVM with reported genetic algorithm based support vector regression indicated that LM/SVM had better generalization ability and higher *** performance of LM/SVM employing polynomial kernel was *** agreement between predicted results and experimental data suggested that the LM/SVM method was successfully developed and the SVM model for increasing propylene was well *** quadratic programming(SQP) algorithm was employed to optimize the operation conditions for maximizing the propylene yield of secondary *** proposed model was claimed to accurately predict the yields of propylene and liquefied petrochemical gas(LPG).

关键词： secondary reactions propylene support vector machines Levenberg-Marquardt algorithm

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Kramers' problem and the Knudsen minimum: A theoretical analysis using a linearized 26-moment approach

Kramers' problem and the Knudsen minimum: A theoretical anal...

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作者： Gu, Xiao-Jun Emerson, David R. Tang, Gui-Hua Computational Science and Engineering Department STFC Daresbury Laboratory Warrington WA4 4AD United Kingdom School of Energy and Power Engineering State Key Lab of Multiphase Flow Xi'An Jiaotong University Xi'an 710049 China

A set of linearized 26 moment equations, along with their wall boundary conditions, are derived and used to study low-speed gas flows dominated by Knudsen layers. Analytical solutions are obtained for Kramers' defect velocity and the velocity-slip coefficient. These results are compared to the numerical solution of the BGK kinetic equation. From the analysis, a new effective viscosity model for the Navier-Stokes equations is proposed. In addition, an analytical expression for the velocity field in planar pressure-driven Poiseuille flow is derived. The mass flow rate obtained from integrating the velocity profile shows good agreement with the results from the numerical solution of the linearized Boltzmann equation. These results are good for Knudsen numbers up to 3 and for a wide range of accommodation coefficients. The Knudsen minimum phenomenon is also well captured by the present linearized 26-moment equations. © 2009 Springer-Verlag.

关键词： Method of moments

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Numerical studies on natural circulation precooling loop of cryogenic liquid rocket engine

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Hangkong Dongli Xuebao/Journal of Aerospace Power 2009年第3期24卷 698-704页

作者： Chen, Er-Feng Li, Yan-Zhong Cheng, Xiang-Hua School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

One set of one-dimensional unsteady homogenous mathematic models for flow and heat process of natural circulation precooling loop of cryogenic liquid rocket engine was established, whilst both inverted annular model and dispersed model were introduced for the prediction of filming boiling region. The results indicate the unstable characteristics of circulation flow rate in precooling process is caused by the unstable characteristics of natural circulation driving force, that is, the heat flux transferred to the cryogenic liquid from the natural circulation precooling loop. Moreover, about 80% of wall temperature drop takes place in filming boiling region, and the inverted temperature distribution law of the return pipe is well interpreted by introducing the two filming boiling models mentioned above.

关键词： Rockets

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New Technology of Thermodynamic Cycle for Waste Heat Recovery of Vehicle Gasoline Engine

New Technology of Thermodynamic Cycle for Waste Heat Recover...

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IEEE PES Asia-Pacific Power and Energy engineering Conference (APPEEC)

作者： Xin Xin Zhang Ke Zeng Mao Gang He State Key Laboratory of Multiphase Flow in Power Engineering Xi''an Jiaotong University Xi'an Shaanxi China

In this paper, the exothermic distribution of fuel was studied detailedly through conducting thermal equilibrium experiment when the vehicle gasoline engine was at different working conditions. Considering the characteristic of the exhaust temperature of the vehicle gasoline engine, the Organic Rankine Cycle (ORC) was adopted for the exhaust recovery. The thermodynamic parameter and thermodynamic performance of the main state points in the ORC were theoretically calculated via computer program. The optimal parameter was determined. On this basis, the organic working fluids were selected. In the last part, a new thermodynamic cycle configuration which can be used to recover the heat from exhaust gas, cooling water and lubricant of vehicle gasoline engine was put forward and introduced.

关键词： Thermodynamics Heat engines Heat recovery Waste heat Vehicles Petroleum Fuels Thermal conductivity Employee welfare Temperature

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Lattice Boltzmann model for axisymmetric thermal flows

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Physical Review E 2009年第3期80卷 037702-037702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

A thermal lattice Boltzmann (LB) model is presented for axisymmetric thermal flows in the incompressible limit. The model is based on the double-distribution-function LB method, which has attracted much attention since its emergence for its excellent numerical stability over the multispeed LB method. Compared with the existing axisymmetric thermal LB models, the present model is simpler and retains the inherent features of the standard LB method. Numerical simulations are carried out for the thermally developing laminar flows in circular ducts and the natural convection in an annulus between two coaxial vertical cylinders. The Nusselt number obtained from the simulations agrees well with the analytical solutions and/or the results reported in previous studies.

关键词： Numerical methods

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Comparative analysis of single droplet evaporation models in Cryogen Spray Cooling

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第4期30卷 653-656页

作者： Xin, Hui Zhou, Zhi-Fu Chen, Bin Wang, Guo-Xiang Wang, Yue-She State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Mechanical Engineering University of Akron Akron OH 44325 United States

Cryogen Spray Cooling is used for cooling human skin during selected laser treatment of Port Wine Stain. Transient state cryogen spray involves intricate droplets evaporation, intense heat convection and mass transfer. In present paper, mass transfer equation of single droplet evaporation model for cryogen spray equilibrium evaporation stage was improved and the effect of seven gas phase models on single droplet evaporation characteristic in R-134a cryogen spray is compared. It is pointed out that the gas phase model which takes the effect of superheat into account was most coincidence with experiment data. A parametric study of the influences of initial diameter and velocity on the droplet evaporation is then carried out by this gas phase model.

关键词： Heat convection

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Evaporation characteristics of single R404a droplet in laser treatment of PWS in conjunction with cryogen spray cooling

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Zhongguo Jiguang/Chinese Journal of Lasers 2009年第10期36卷 2691-2695页

作者： Xin, Hui Zhou, Zhifu Wang, Guoxiang Chen, Bin Wang, Yueshe State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Department of Mechanical Engineering University of Akron Akron OH 44325 United States

Cryogen spray is an effective cooling technique for the laser treatment of port wine stain (PWS), which can protect the epidermis from the thermal injuries safely. However, cryogen R134a cannot supply enough cooling capacity for the laser surgery in patients with darker skin because of the absorption of laser energy by melanin. Cryogen R404a are expected to protect the darker skin well because of its lower boiling point. A theoretical model is proposed to describe the evaporation process of single droplet and its validation is confirmed by the agreement between numerical simulation with experimental result. With this model, the cooling effect of R404a droplet is compared with R134a droplet and it is found that R404a droplet can reach lower temperature. Then the influences of initial diameter and ambient mass faction of cryogen on the evaporation characteristics of R404a droplet are analyzed and the result is useful to guide the cryogen spray cooling for laser therapy of PWS patients with darker skin.

关键词： Drops

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Process analysis of lignite circulating fluidized bed boiler coupled with pyrolysis topping

Process analysis of lignite circulating fluidized bed boiler...

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20th International Conference on Fluidized Bed Combustion

作者： Wang, Baoqun Dong, Li Wang, Yin Matsuzawa, Y. Xu, Guangwen State Key Laboratory of Multiphase Complex System Institute of Process Engineering Chinese Academy of Sciences Beijing China Research Laboratory IHI Corporation Ltd. Yokohama Japan

We developed a comprehensive process model in ASPEN Plus to simulate the energy and mass balances of a lignite-fueled atmospheric circulating fluidized bed (CFB) boiler integrated with coal predrying and pyrolysis topping. In this model, it is assumed that the heat from exhausted flue gas was employed for coal predrying, and the sensible heat derived from circulated bed material was used for the pyrolysis topping (endothermic process). The simulation was conducted with respect to the Yunnan Kaiyuan CFB boiler, and two representative lignite coals from Xiao Long Tan (XLT) and Xin Shao (XS) were considered. The result shows that the predrying of coal with the sensible heat of above 363 K from flue gas, the amount of coal consumed in the boiler can be reduced by 3.5% and 5.3% for XLT lignite and XS lignite, respectively. It was also found that integration of pyrolysis topping with the boiler increased the coal consumption of the boiler, and the extent of consumption-increase varies with the yields of tar and gas in the pyrolysis topping process. For a gas yield of 5.2% and a tar yield of 5-6%, the consumption of XS lignite increased by about 20% comparing to that in the case without topping.

关键词： Pyrolysis

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PIV measurement of turbulent bubbly mixing layer flow with polymer additives

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

作者： Ning, T. Guo, F. Chen, B. Zhang, X. State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Based on experimental investigation of single-phase turbulent mixing layer flow with polymer additives, bubbly mixing layer was experimentally investigated by PIV. The velocity ratio between high and low speed is 4:1 and the Reynolds number based on the velocity difference of two steams and hydraulic diameter of the channel ranges is 73333. Gas bubbles with about 0.5% gas fraction were injected into pure water mixing layer with/without polymer additives from three different parts at the end of the splitter plate. The comparison between single phase and bubbly mixing layer shows clearly that the dynamic development of mixing layer is great influenced by the bubble injection. Similar with single phase, the Reynolds stress and vorticity still concentrate in a coniform area of central mixing flow field part and the width will increase with increasing the Reynolds number. Mean Reynolds stress will decrease with bubble injection in high Reynolds numbers and the decreasing of Reynolds stress with polymer additives is much more than pure water case. © 2009 IOP Publishing Ltd.

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