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Numerical simulation of predicting and reducing solid particle erosion of solid-liquid two-phase flow in a choke

Petroleum Science 2009年第1期6卷 91-97页

作者： Li Guomei Wang Yueshe He Renyang Cao Xuewen Lin Changzhi Meng Tao State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇an Shaanxi 710049 China China Special Equipment Inspection and Research Institute Beijing 100013 China School of Transport ＆ Storage and Civil Engineering China University of Petroleum Qingdao Shandong 266555 China Petroleum Exploration and Production Research Institute Sinopec Beijing 100083 China

Chokes are one of the most important components of downhole flow-control equipment. The particle erosion mathematical model, which considers particle-particle interaction, was established and used to simulate solid particle movement as well as particle erosion characteristics of the solid-liquid two-phase flow in a choke. The corresponding erosion reduction approach by setting ribs on the inner wall of the choke was advanced. This mathematical model includes three parts： the flow field simulation of the continuous carrier fluid by an Eulerian approach, the particle interaction simulation using the discrete particle hard sphere model by a Lagrangian approach and calculation of erosion rate using semiempirical correlations. The results show that particles accumulated in a narrow region from inlet to outlet of the choke and the dominating factor affecting particle motion is the fluid drag force. As a result, the optimization of rib geometrical parameters indicates that good anti-erosion performance can be achieved by four ribs, each of them with a height （H） of 3 mm and a width （B） of 5 mm equaling the interval between ribs （L）.

关键词： Solid-liquid two-phase flow discrete particle hard sphere model choke erosion rate antierosion numerical simulation

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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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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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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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Dynamic stability experiments of compliant foil thrust bearing with viscoelastic support

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Tribology International 2009年第5期42卷 662-665页

作者： Quan Zhou Yu Hou Chunzheng Chen School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China

In order to reduce the complexity of machine construction and improve the mechanical efficiency, high speed rotation machineries usually implement self-acting gas bearings to substitute the traditional oil-lubricated bearings. This paper presents test results of a gas thrust bearing with viscoelastic support which is designed for high speed turbo-machinery. The gas bearing, which belongs to compliant foil bearings, consists of a top thin metal foil and a bottom thin rubber foil. Static and stability experiments are conducted on a high speed gas turbine test rig. The static results indicate that the structural stiffness of test bearing generally increases with the increase in axial load and the decrease in thickness of bottom foil. In the rotation tests, rotor runs stably with small vibration amplitude, which is dominant in waterfall plot during whole speed up procedure. It shows that test bearing has preferable stability characteristics for high speed gas turbines.

关键词： Foil thrust bearing Structural stiffness Bearing stability

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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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Characteristics of heat transfer for narrow gap on horizontal heated surface with porous media

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Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 2009年第5期43卷 431-434页

作者： Hu, Ben-Xue Xu, Yan-Feng Su, Guang-Hui Qiu, Sui-Zheng Zhao, Da-Wei Wu, Ying-Wei State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an 710049 China Nuclear Power Institute of China Chengdu 610041 China

Experiments were carried out to study the characteristics of heat transfer on a downward-facing heated surface with porous media in narrow horizontal gap at atmosphere pressure using water as working fluid. The boiling curves were obtained under different conditions. The heat transfer increases significantly with porous media in the gap especially under boiling condition. The heat transfer in narrow horizontal gap can be enhanced by increasing the gap size and by using porous media with high thermal conductivity and appropriate porosity. Based on the mechanism of heat transfer in porous media, the correlations for natural convection and nucleate boiling were proposed to predict the heat transfer under the present condition.

关键词： Facings

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Investigation on surface wettability and surface structure of PTFE after remote oxygen plasma treatment

Investigation on surface wettability and surface structure o...

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IEEE International Conference on Plasma Science (ICOPS)

作者： H. X. Liu H. J. Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China Department of Environmental Engineering Xi'an Jiaotong University Xi'an China

Summary form only given. In this paper, the surface wettability and surface structure of poly(tetrafluoroethylene) (PTFE) treated with remote oxygen plasma are studied. The contact angles of the samples are measured and the critical surface tensions (gamma c ) are determined on the basis of the Zisman's plots. Then the variation of contact angle to water (thetas H2O ) and the gamma c are as the functions of the sample positions, which are at the different distance from the center of oxygen plasma active discharge zone. Since the better surface wettability can be obtained at 0 cm and 40 cm from the center of oxygen plasma active discharge zone, respectively, the variation of thetas H2O and are farther as the functions of the plasma treatment time. Furthermore, the values of dispersion force gamma s d , dipole force gamma s p and hydrogen bonding force gamma s h to the surface free energy gamma s of treated PTFE are evaluated by the extended Fowkes equation. The analysis is carried out between the distribution of reactive species in remote oxygen plasma and the surface free energy as well as surface wettability. All the results show that the surface wettability of PTFE treated with oxygen plasma is only determined by the value of polar force (gamma s p + gamma s h ), especially the gamma s h . A mixed atmosphere constituted by all reactive species or super pure and high free radicals concentration in remote oxygen plasma are both propitious to the increasing of polar force (gamma s p + gamma s h ), but the surface free energy is influenced mainly by the concentration of charged particles. X-ray photoelectron spectroscopy (XPS) indicates that the C-F bonds on the PTFE surface are broken by the oxygen plasma treatment, and then the polar functional groups of C-O and C=0 are introduced effectively, the surface wettability increases.

关键词： Surface treatment Surface structures Plasma measurements Water Plasma x-ray sources Surface tension Surface discharges Hydrogen Bonding forces Equations

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