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Dynamic stability experiments of compliant foil thrust bearing with viscoelastic support

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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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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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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Comparison of modeling options for delayed neutron precursor movement in a molten salt reactor

Comparison of modeling options for delayed neutron precursor...

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2009 ANS Annual Meeting and Embedded Topical Meeting: Nuclear and Emerging Technologies for Space, NETS 2009

作者： Zhang, Dalin Rineiski, Andrei Qiu, Suizheng State Key Laboratory Multiphase Flow in Power Engineering School of Nuclear Science and Technology Xi'an Jiaotong University 28 West Xian ning Road Xi'an 710049 China Institute for Nuclear and Energy Technologies Forschungszentrum Karlsruhe Hermann-von-Helmholtz-Platz 1 Eggenstein-Leopoldshafen D-76344 Germany

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Experimental study on the performance of an aircraft environmental control system

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Applied Thermal engineering 2009年第16期29卷 3284-3288页

作者： Hongli Zhao Yu Hou Yongfeng Zhu Liang Chen Shuangtao Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China The First Aircraft Institute of AVIC1 Xi’an 710089 PR China

In this paper, the experimental study on the off-design performance and dynamic response of an aircraft environmental control system (ECS) was presented. A bootstrap air cycle refrigeration system with high-pressure water separation was employed in the ECS. Both the static test and the dynamic test were conducted on the ECS. The performance of the key components including precooler, recuperator, compressor, and turbine was investigated. The test results show the performance of the tested ECS can meet the requirements of design. However, some parameters including outlet pressure, turbine efficiency, and rotational speed might vary obviously when the operation conditions changed. The outlet humidity ratio and outlet temperature might also fluctuate largely during the start-up process. It is necessary to take into account the off-design performance and the transient performance in the design of ECS.

关键词： Environmental control system Off-design performance Dynamic response Brayton cycle

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Application of opposed water spray cooling in an high-temperature entrained-flow coal gasifier

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第6期30卷 984-986页

作者： Liu, Pei-Yao Chen, Qiu-Yang Zeng, Min Wang, Qiu-Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

A series of chemical reactions happen in the coal gasifier and as a result, high temperature syngas is obtained which contains a lot of solid granules. The high-temperature syngas must be cooled, because it can not be utilized directly. The opposed water spray cooling is not only effective, but also could dedust the syngas. In the present study, the CFD technique is used to investigate the effect of the opposed spray cooling in a gasifier. The Euler-Lagrange method is applied to deal with the syngas and the water droplets respectively. A non-dimensional parameter Temperature Non-uniform Factor (TNF) is defined to confirm the height of the cooling section. The simulated results match the designed data well. If water droplets with small diameters are used, the single-stage water spray cooling is more economic than the two-stage water spray cooling.

关键词： Computational fluid dynamics

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Piv measurement of turbulent mixing layer flow with polymer additives

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第4期30卷 608-610页

作者： Ning, Tao Guo, Fu-De Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Turbulent mixing layer flow with 200 mg/kg polymer additives was measured by PIV and compared with pure water cause. The velocity ratio between high and low speed is 4:1 and the velocity difference ranges from 0.25 m/s to 1.25 m/s. It is showed that large vortex structures exist in flow field with/without polymer addictives, but the coherent structure is much clearer and the large eddy will roll up earlier when polymer is added. Similar with pure water case, the Reynolds stress is decreasing and the vorticity is increasing with increasing the velocity difference. However, the width and range of Reynolds shear stress and vorticity are wider and larger.

关键词： Turbulent flow

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Prediction of transition boiling concerning downward facing horizontal surface in confined space using artificial neural network

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Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 2009年第7期43卷 616-621页

作者： Zhao, Da-Wei Su, Guang-Hui Tian, Wen-Xi Qiu, Sui-Zheng Sugiyama, K. 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 Faculty of Engineering Hokkaido University Kita 13 Jo Nishi 8 Chome Kita-Ku Sapporo 060-8628 Japan

An artificial neural network (ANN) for predicting Nusselt number was trained successfully based on the data of transition boiling experiment, which was conducted in confined space with downward facing surface at atmospheric pressure. The effects of wall superheat, Δtw, the ratio of the gap size to the diameter of heated surface, δ/D, Prandtl number and Rayleigh number on Nusselt number under transition boiling condition were analyzed based on the trained ANN. A correlation used to accurately predict the natural convection heat transfer under the present condition was obtained and it provides a reasonable agreement against the experimental data.

关键词： Facings

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Research on surface damage of solid material subjected to high speed liquid impact

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Binggong Xuebao/Acta Armamentarii 2009年第SUPPL. 2期30卷 139-144页

作者： Xie, Yong-Hui Wang, Yong Chen, Jian-Hui Zhang, Di State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an 710049 China

In order to study the surface damage of solid material subjected to the high speed liquid impact, both numerical and experimental methods were established. The smoothed particle hydrodynamics and finite element analysis were used to calculate the material damage. The conditions of PMMA and steel were analyzed to obtain the dynamic stress and strain distribution during impact. An experiment apparatus was build. The velocity of the impact jet was measured using a high speed camera and the apparatus. A digital microscope was used to measure the three dimensional profile of the sample before and after high speed liquid impact up to 600 m/s. The dimensions of damage area were recorded and analyzed statistically. Based on the statistical results, the performance of the materials resisting liquid corrosion was evaluated.

关键词： High speed cameras

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Optimal heat transfer criterion and inclination angle effects on non-boiling regime spray cooling

Optimal heat transfer criterion and inclination angle effect...

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IEEE Symposium on Semiconductor Thermal Measurement and Management (SEMI-THERM)

作者： Yong-xian Guo Zhi-fu Zhou Jian-yuan Jia Shao-rong Zhou School of Mechano-Electronic Engineering Xidian University Xi'an Shaanxi China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China Intel Asia-Pacific Research and Development Limited Shanghai China

Based on the maximum CHF (critical heat flux) criterion, an optimal heat transfer criterion, which is called H criterion, was proposed. Experimental apparatuses were conducted. Distilled water was used as the working fluid. Three different DANFOSS nozzles with cone angles being 54deg, 50deg and 54deg respectively were used to cool a 30times30 mm 2 square copper surface. Experimental results indicated that the volumetric fluxes were pro-portioned to P 0.5 , where P is the pressure drop across the nozzles. The optimal distance between the nozzles and the heated surface were derived. The results indicated that the optimal heat transfer appeared while the outside of the impellent thin spray film inscribed in the square heated surface. Based on the H criterion aforementioned, two DANFOSS nozzles of the three were used to study the temperature distribution of the heated surface experimentally while there were spray inclination angles. Distilled water was also used impacting on the 30times30 mm 2 square copper surface aforementioned and a circular heated copper surface with diameters being 30 mm respectively. The heat flux of the surface was kept in constant (about 26-35 W/cm 2 ). The inclination angles were 0deg, 10deg, 20deg, 30deg, 40deg and 50deg respectively. Experimental results indicated that the grads of the temperature of the surface increases first and then decreases with the increase of the inclination angle.

关键词： Heat transfer Spraying Temperature Electronics cooling Coolants Heat engines Copper Uncertainty Water heating Space exploration

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