检索结果-南通市图书馆

Influence of Blade Outlet Angle on Performance of Low-specific-speed Centrifugal Pump

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal science 2013年第2期22卷 117-122页

作者： Cui Baoling Wang Canfei Zhu Zuchao Jin Yingzi The Province Key Laboratory of Fluid Transmission Technology Zhejiang Sci-Tech University

In order to analyze the influence of blade outlet angle on inner flow field and performance of low-specific-speed centrifugal pump, the flow field in the pump with different blade outlet angles 32.5°and 39° was numerically calculated. The external performance experiment was also carried out on the pump. Based on SIMPLEC algorithm, time-average N-S equation and the rectified k-ε turbulent model were adopted during the process of computation. The distributions of velocity and pressure in pumps with different blade outlet angles were obtained by calculation. The numerical results show that backflow areas exist in the two impellers, while the inner flow has a little improvement in the impeller with larger blade outlet angle. Blade outlet angle has a certain influence on the static pressure near the long-blade leading edge and tongue, but it has little influence on the distribution of static pressure in the passages of impeller. The experiment results show that the low-specific-speed centrifugal pump with larger blade outlet angle has better hydraulic performance.

关键词： centrifugal pump blade outlet angle numerical simulation external characteristic

Numerical Simulation of Heat Transfer Performance for Ultra-Thin Flat Heat Pipe

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal science 2023年第2期32卷 643-649页

作者： YAN Wentao YANG Xin LIU Tengqing WANG Shuangfeng School of Electric Power South China University of TechnologyGuangzhou 510640China Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education School of Chemistry and Chemical EngineeringSouth China University of TechnologyGuangzhou 510640China

The heat transfer performance of ultra-thin flat heat pipes with#180 copper mesh wick was studied by numerical simulation for different heating *** length,width and height of the ultra-thin flat heat pipe are 80 mm,8.5 mm and 1 mm,*** temperature distribution and flow characteristics of ultra-thin flat heat pipes were simulated by coupling porous media model and user-defined function(UDF)in *** validate the accuracy of the numerical model,the simulation results of the ultra-thin flat heat pipe are compared with the experimental data in predicting the evaporation section *** numerical model has good accuracy for the one-dimensional heat transfer method of ultra-thin flat heat *** velocity,pressure drop of the wick and total temperature difference have the same variation *** the increase of heating power,the temperature difference of ultra-thin flat heat pipes increases,and the pressure drop and the liquid velocity in the wick also increase.

关键词： ultra-thin flat heat pipes evaporation section temperature temperature difference copper mesh simulation

Improving the Weld Formation and Mechanical Properties of the AA-5A06 Friction Pull Plug Welds by Axial Force Control

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2020年第6期33卷 828-838页

作者： Jinyong Gao Lijun Yang Lei Cui Peng Lu Jun Yang Yanjun Gao Tianjin Key Laboratory of Advanced Joining Technology School of Materials Science and EngineeringTianjin UniversityTianjin 300350China Capital Aerospace Machinery Corporation Beijing 100044China

In the present study, the weld formation and mechanical properties of the AA-5A06 friction pull plug welded(FPPW) joints were improved by controlling the axial force history. Several defect-free FPPW joints were made successfully by using the welding parameters of 15–20 k N/s axial loading rate, 20–30 k N axial welding force and 6–7 mm axial feeding displacement. The results indicated that using higher axial loading rate and axial welding force produced more stable heat generation and shorter frictional heating time between the frictional interface. In this case, the plastic flow of the materials around the hole could be further improved since the axial feeding displacement of the plug was increased. The maximum ultimate tensile strength(UTS) and elongation of the FPPW 5A06 joints were 314 MPa and 4.8%, respectively. The thermal mechanically affect zone(TMAZ) had the lowest hardness value throughout the joint and was found as the fracture location to all the tensile samples. The softening of TMAZ was mainly caused by the weakening of the cold work hardening and the coarsening of grains.

关键词： Friction pull plug welding Parameter optimization Microstructures Mechanical properties

Argon diffusion from biotite at high temperature and pressure

在线全文

学校读者我要写书评

暂无评论

science china Chemistry 1995年第2期38卷 221-227页

作者：陈道公贾命命李彬贤陆全明谢鸿森侯渭 University of science and Technology of china Hefei 230026 China Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China

t The experiments of argon diffusion dynamics for biotite were carried out at 700 -1000℃ and 0.5 - 2,0 GPa and the diffusion coefficient and activation energy using different models have been calculated. The results indicate that the pressure does affect the argon diffusion and its effect is opposite to that of temperature. When p increases, the activation energy increases and diffusion coefficient decreases. The relation between pressure, closure temperature and cooling rate has been obtained. It is postulated that in low T and high p conditions, the argon diffusion from the environment to the system could occur and incur the appearance of the external argon in minerals.

关键词： Ar diffusion biotite high T and p closure temperature external argon.

Three-dimensional spiral structure of tropical cyclone under four-force balance

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第6期23卷 644-648页

作者：刘式适付遵涛刘式达 Department of Atmospheric and Oceanic sciences and Laboratory for Climate and Ocean–Atmosphere Studies School of Physics Peking University

The steady axis-symmetrical atmosphere dynamical equations are used for describing spiral structure of tropical cyclones under four-force （pressure gradient force, Coriolis force, centrifugal force, and friction force） balance, and the dynamical systems of three-dimensional （3D） velocity field are introduced. The qualitative analysis of the dynamical system shows that there are down 3D spiral structures in eye of tropical cyclone and tropical cyclone is 3D counterclockwise up spiral structure. These results are consistent with the observed tropical cyclone on the weather map.

关键词： tropical cyclones spiral structure dynamical systems four-force balance

Numerical Simulation of Flow in Centrifugal Pump with Complex Impeller

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal science 2011年第1期20卷 47-52页

作者： Bao-ling Cui Yong-gang Lin Ying-zi Jin The Laboratory of Fluid Transmission and Application Zhejiang Sci-Tech University Hangzhou 310018China State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model,three dimensional turbulent flow fields in centrifugal pump with long-mid-short blade complex impeller are calculated and analyzed *** relative velocity and pressure distributions in the flowpart are *** is found that the flow in the passage of the complex impeller is unsymmetrical due to the joint action between volute and *** back-flow region is at inlet of long-blade suction side,near middle part of long-blade pressure side and outlet of short-blade suction *** flow near volute throat is affected greatly by *** relative velocity is large and it is easy to bring back flow at outlet of the complex impeller near volute *** static and total pressure rise uniformly from inlet to outlet in the *** impeller outlet,the pressure periodically decreases from pressure side to suction side,and then the static pressure sharply rise near the *** experimental results show that the back flow in the impeller has an important influence on the performance of pump.

关键词： Complex impeller Centrifugal pump Numerical simulation Experiment

Global Rank Axioms for Poset Matroids

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2004年第3期20卷 507-514页

作者： ShuChaoLI YanQinFENG DepartmentofMathematics CentralChinaNormalUniversityWuhan430079P.R.China DepartmentofMathematics NanjingUniversityNanjing210093P.R.China

An excellent introduction to the topic of poset matroids is due to Barnabei, Nicoletti and Pezzoli. In this paper, we investigate the rank axioms for poset matroids; thereby we can characterize poset matroids in a “global” version and a “pseudo-global” version. Some corresponding properties of combinatorial schemes are also obtained.

关键词： Poset matroids Rank function Combinatorial scheme Distributive lattice

Activation of Nitromethane to Cyanide by a Mononuclear Cu(Ⅱ) Complex

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Structural Chemistry 2014年第11期33卷 1643-1648页

作者：吴楠楠陈昌能黄德光 State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences University of Chinese Academy of sciences

The tridentate ligand DPA-Me（2） was readily prepared from DPA（DPA = 2,2-dipicolylamine） in high yield. The mixture of 2 and Cu（ClO4）26H2O in methanol gave a five-coordinated mononuclear complex [（DPA-Me）Cu（Me CN）（ClO4）]（ClO4）（3）. Recrystallization of 3 in CH3NO2 led to an activation of CH3NO2 to CN- by the formation of product as a dinuclear cyanide bridged complex {[Cu（DPA-Me）]2（CN）（ClO4）3CH3NO2}n（4）. Both 3 and 4 were characterized by X-ray crystallography, IR spectroscopy and elemental analysis. The crystal of 4 was grown in space group P21/c with a = 17.74582（15）, b = 13.89877（11）, c = 14.92546（13） A, β = 91.4246（8）°, V = 3680.15（5） 3, Z = 4, Dc = 1.695 g/cm^3, F（000） = 1912, C28H33Cl3Cu2N8O14, Mr = 939.05, μ = 1.602 cm^-1, Cu Kα radiation（λ = 1.54184 ）, R = 0.0485 and w R = 0.1246 for 6414 observed reflections with I 〉 2σ（I）.

关键词： tridentate ligand copper activation nitromethane cyanide

Comparison of the effects of aluminum and iron(Ⅲ)salts on ultrafiltration membrane biofouling in drinking water treatment

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2018年第1期30卷 96-104页

作者： Xing Wang Baiwen Ma Yaohui Bai Huachun Lan Huijuan Liu Jiuhui Qu Key Laboratory of Drinking Water science and Techno|ogy Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of sciences Beijing 100049China

Coagulation plays an important role in alleviating membrane fouling, and a noticeable problem is the development of microorganisms after long-time operation, which gradually secrete extracellular polymeric substances（EPS）. To date, few studies have paid attention to the behavior of microorganisms in drinking water treatment with ultrafiltration（UF）membranes. Herein, the membrane biofouling was investigated with different aluminum and iron salts. We found that Al_2（SO_4）_3·18 H_2O performed better in reducing membrane fouling due to the slower growth rate of microorganisms. In comparison to Al_2（SO_4）_3·18H_2O,more EPS were induced with Fe_2（SO_4）_3·x18H_2O, both in the membrane tank and the sludge on the cake layer. We also found that bacteria were the major microorganisms, of which the concentration was much higher than those of fungi and archaea. Further analyses showed that Proteobacteria was dominant in bacterial communities, which caused severe membrane fouling by forming a biofilm, especially for Fe_2（SO_4）_3·x18H_2O. Additionally, the abundances of Bacteroidetes and Verrucomicrobia were relatively higher in the presence of Al_2（SO_4）_3·18 H_2O,resulting in less severe biofouling by effectively degrading the protein and polysaccharide in EPS. As a result, in terms of microorganism behaviors, Al-based salts should be given preference as coagulants during actual operations.

关键词： Ultrafiltration membrane Al-based and Fe-based salts Coagulation Behavior of microorganisms Fouling mechanism