Dec 2008, Volume 2 Issue 4
    

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  • Reliability design method for steam turbine blades
    SHI Jinyuan
    2008, 2(4): 363-368. https://doi.org/10.1007/s11708-008-0073-7
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    Based on theories of probability and statistics, and taking static stresses, dynamic stresses, endurance strength, safety ratios, vibration frequencies and exciting force frequencies of blades as random variables, a reliability design method for steam turbine blades is presented. The purport and calculation method for blade reliability are expounded. The distribution parameters of random variables are determined after analysis and numerical calculation of test data. The fatigue strength and the vibration design reliability of turbine blades are determined with the aid of a probabilistic design method and by interference models for stress distribution and strength distribution. Some blade reliability design calculation formulas for a dynamic stress design method, a safety ratio design method for fatigue strength, and a vibration reliability design method for the first and second types of tuned blades and a packet of blades on a disk connected closely, are given together with some practical examples. With these methods, the design reliability of steam turbine blades can be guaranteed in the design stage. This research may provide some scientific basis for reliability design of steam turbine blades.
  • Optimization of Venturi tube design for pipeline pulverized coal flow measurements
    WU Zhansong, XIE Fei
    2008, 2(4): 369-373. https://doi.org/10.1007/s11708-008-0072-8
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    A Venturi flow meter was designed to accurately measure the mass flow rate of pulverized coal in power plant pipelines. Numerical simulations of the dilute turbulent gas-solid two-phase flow in a horizontal Venturi tube were used to study the effects of Venturi tube geometry on the pressure distribution in the mixture. The results show that Venturi tube geometry strongly influences the metering of the dilute gas-particle two-phase flow. The geometry can be optimized to improve the precision of the measurement and ensure stable measurements. Furthermore, the geometries of three types of Venturi tubes were optimized for an experimental study of pulverized coal mass flow rate measurements.
  • Sensitivity analysis and numerical experiments on transient test of compact heat exchanger surfaces
    REN Hesheng, LAI Lingjun, CUI Yongzheng
    2008, 2(4): 374-380. https://doi.org/10.1007/s11708-008-0079-1
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    A single-blow transient testing technique considering the effect of longitudinal heat conduction is suggested for determining the average convection heat transfer coefficient of compact heat exchanger surface. By matching the measured outlet fluid temperature variation with similar theoretical curves, the dimensionless longitudinal conduction parameter ?l, the time constant of the inlet fluid temperature ?+, and the number of heat transfer units Ntu can be determined simultaneously using the Levenberg-Marquardt nonlinear parameter estimation method. Both sensitivity analysis and numerical experiments with simulated measurements containing random errors show that the method in the present investigation provides satisfactory accuracy of the estimated parameter Ntu, which characterizes the heat transfer performance of compact heat exchanger surfaces.
  • Optimal ratio of bend channel in centrifugal compressor
    WEN Suping, HU Xiaowen, LI Tingbin, ZHANG Yong, WANG Jun
    2008, 2(4): 381-385. https://doi.org/10.1007/s11708-008-0084-4
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    A numerical investigation on the flow in a bend channel by coupling the impeller with the vaneless diffuser in a centrifugal compressor with different r/b ratios (bend radius r to bend channel width b) is presented. The jet-wake effect of the impeller outlet is considered and flow pattern in the bend channel and the performance of the centrifugal compressor stage are investigated. The results indicate that there is an optimal r/b ratio for increasing the stage efficiency to the highest for a specific compressor stage. The change in r/b ratio significantly affects the flow angle of the bend channel outlet. The prime reason for the total pressure loss in the bend channel is the wall friction in the bend channel.
  • Computation model for corrosion resistance of nanocrystalline zircaloy-4
    ZHANG Xiyan, ZHU Yutao, LIU Qing, LUAN Baifeng, HUANG Guangjie, LI Cong, ZHANG Xiyan, SHI Minghua, LIU Nianfu, ZHANG Xiyan, LI Cong
    2008, 2(4): 386-389. https://doi.org/10.1007/s11708-008-0102-6
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    A computation model of the corrosion rate versus grain size of nanocrystalline zircaloy-4 was presented. The influence of the second phase on the conductivity of alloy was considered. By this model, the corrosion rate of nanocrystalline zircaloy-4 at different temperature was calculated. The results show that the corrosion rate constant and weight gain of nanocrystalline zircaloy-4 decrease with the decrease of grain size, and that the corrosion weight gain of nanocrystalline zircaloy-4 is less than that of zircaloy-4 of coarse grain. The computational result is coincident with the experimental result.
  • Effect of inlet box on performance of axial flow fans
    LI Jingyin, TIAN Hua, YUAN Xiaofang
    2008, 2(4): 390-394. https://doi.org/10.1007/s11708-008-0087-1
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    Numerical investigations on 3D flow fields in an axial flow fan with and without an inlet box have been extensively conducted, focusing on the variation of fan performance caused by the internal flow fields and the velocity evenness at the exit of the inlet box. It is interesting to find that although the inlet box is well designed in accordance with basic design principles, there is a flow separation region in it. Furthermore, this flow separation and the resulting uneven velocity distribution at the exit lead to some decrease in the efficiency and an increase in the total pressure rise of the fan. This research shows that the inlet box needs further improvement and such a check on the flow fields is of value for the design of inlet boxes.
  • Combustion characteristics of SI engine fueled with methanol-gasoline blends during cold start
    SONG Ruizhi, LIU Shenghua, LIANG Xiaoqiang, Tiegang H U
    2008, 2(4): 395-400. https://doi.org/10.1007/s11708-008-0081-7
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    A 3-cylinder port fuel injection (PFI) engine fueled with methanol-gasoline blends was used to study combustion and emission characteristics. Cylinder pressure analysis indicates that engine combustion is improved when methanol is added to gasoline. With the increase of methanol, the flame developing period and the rapid combustion period are shortened, and the indicated mean effective pressure increases during the first 50 cycles. Meanwhile, a novel quasi-instantaneous sampling system was designed to measure engine emissions during cold start and warm-up. The results at 5°C show that unburned hydrocarbon (UHC) and carbon monoxide (CO) decrease remarkably. Hydrocarbon (HC) reduces by 40% and CO by 70% when fueled with M30 (30% methanol in volume). The exhaust gas temperature is about 140°C higher at 200 s after operation compared with that of gasoline.
  • Performance and emission characteristics of QHCCI dimethyl ether engine
    WANG Ying, LI Wei, ZHOU Longbao, LIU Shenghua, HU Tiegang
    2008, 2(4): 401-405. https://doi.org/10.1007/s11708-008-0075-5
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    Experimental investigation into the effects of different pilot amounts of dimethyl ether (DME) on the performance and emission of a single-cylinder direct-injection DME engine is conducted. The results show that a DME engine can operate at a wider range of speeds and loads at quasi-homogenous charge compression ignition (QHCCI) mode. The brake thermal efficiency increases while the exhaust temperature decreases. NOx emission decreases by about 30%–50% although there is a slight increase in HC and CO emissions. NOx, HC and CO emissions increase with an increase in the amount of DME pilot. QHCCI is a good way to increase thermal efficiency and decrease NOx emission.
  • Analysis of flow and heat transfer characteristics of porous heat-storage wall in greenhouse
    OUYANG Li, LIU Wei
    2008, 2(4): 406-409. https://doi.org/10.1007/s11708-008-0094-2
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    The flow and heat transfer characteristics of porous heat-storage wall in greenhouse are studied by using the one-dimensional steady energy two-equation model for saturated porous medium. The results show that the heat exchange between the air and the solid matrix of the porous heat-storage wall depends upon the inlet air velocity, the porosity and the permeability of porous medium, and the thermal conductivity of the solid matrix. Because the incidence of solar radiation on the porous heat-storage wall is not uniform, the new composite porous solar wall with different porosity is proposed to reduce the disadvantageous effect.
  • Optimization of fuel supply map during starting process of electronic controlled diesel engine
    LIANG Jinguang, YU Xiumin, GAO Yue, WANG Yunkai, YU Hongyang, Gong Baoli
    2008, 2(4): 410-415. https://doi.org/10.1007/s11708-008-0080-8
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    Tests were conducted to study influence of fuel supply map during the starting process of an electronic controlled diesel engine using an electronic controlled diesel engine which was made up of a CA498Z diesel engine, a VP37 electronic controlled distributor injection pump management system and a VS100 calibration system. The calibration process of starting fuel supply map was educed under the principle of low HC emission and rapid starting velocity. The calibration methods of starting fuel supply map were obtained.
  • Integrated virtual-design methods for forecasting radiated noise of single cylinder diesel block
    GUO Lei, HAO Zhiyong, XU Hongmei, LIU Lianyun
    2008, 2(4): 416-421. https://doi.org/10.1007/s11708-008-0097-z
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    The two cycle dynamical results, such as the bearing load, the piston thrust, and the load spatial distribution etc., were obtained by hybrid dynamical simulation of the flexible assembly of the block and crank-train. The finite element model of the block was validated by modal test. The frequency response of the block was calculated using the finite element method (FEM). Finally, the radiated noise such as sound power level and efficiency in the out sound field were obtained using the direct boundary element method (BEM).
  • Lightening structure optimization on turbine wheel of vehicular turbocharger
    ZHAO Junsheng, MA Chaochen, HU Liaoping
    2008, 2(4): 422-426. https://doi.org/10.1007/s11708-008-0098-y
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    Based on basic principle of optimization design, structure optimization of turbine is conducted using optimization module of ANSYS and APDL in order to get the minimum turbine weight. Meanwhile, the original blade profile and flow passage are maintained, and the structural strength of the turbine are guaranteed. Considering assembly technique and cast requirement, the structure of the modified turbine is determined which can save 6.91 percent of the material compared with the original one. The modified turbine not only saved material, but also gained better effect of mass distribution between the turbine and the compressor impeller. The result can provide useful reference to engineering application of turbocharger.
  • Observation of premixed flame fronts by laser tomography
    MU Kejin, WANG Yue, LEI Yu, ZHANG Zhedian, NIE Chaoqun, XIAO Yunhan
    2008, 2(4): 427-432. https://doi.org/10.1007/s11708-008-0069-3
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    The principle of combustion field detection by using laser tomography, as well as exploitation of the laser tomography apparatus and the tool for image processing is described. An experiment detecting flame fronts by laser tomography was made by employing a V-shaped premixed flame. The results show that the instantaneous geometric shape of flame wrinkles within the light sheet can be clearly resolved. The contours of the flame fronts are precisely tracked through active contour models (ACM) from the digital images of laser tomography, laying the basis for the quantitative analysis of flame wrinkling and propagation.
  • Noise reduction for centrifugal fan with non-isometric forward-swept blade impeller
    MA Jianfeng, QI Datong, MAO Yijun
    2008, 2(4): 433-437. https://doi.org/10.1007/s11708-008-0082-6
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    To reduce the noise of the T9-19No.4A centrifugal fan, whose impeller has equidistant forward-swept blades, two new impellers with different blade spacing were designed and an experimental study was conducted. Both the fan’s aerodynamic performance and noise were measured when the two redesigned impellers were compared with the original ones. The test results are discussed in detail and the effect of the noise reduction method for a centrifugal fan using impellers with non-isometric forward-swept blades was analyzed, which can serve as a reference for researches on reduction of fan noise.
  • Numerical simulation of air flow field in high-pressure fan with splitter blades
    LI Jianfeng, LU Junfu, ZHANG Hai, LIU Qing, YUE Guangxi
    2008, 2(4): 438-442. https://doi.org/10.1007/s11708-008-0085-3
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    For a deeper understanding of the flow characteristics in the high-pressure centrifugal blower of a fan of Model 9-26 with splitter blades, a three dimensional (3-D) numerical simulation of air flows in the fan was conducted with FLUENT software. The standard k-? turbulent model and unstructured grids were used. The computational fluid dynamics (CFD) results showed that the performance of a fan could be improved by adding the splitter blades in the channel among the leaf blades. Under operational conditions, with the presence of splitter blades, the air flow rate of the fan increased about 5% and the total pressure at the outlet of the fan increased about 10% on average. It was also found that the length of the splitter blades affected the air flow and pressure drop. There is an optimal value for the length. The simulation results provide helpful information for improving the fan performance.
  • Numerical analysis of aerodynamic noise radiated from cross flow fan
    CHEN Anbang, LI Song, HUANG Dongtao
    2008, 2(4): 443-447. https://doi.org/10.1007/s11708-008-0063-9
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    The flow field in a cross flow fan was simulated by solving the 2-D unsteady Reynolds-averaged Navier-Stokes equations. The calculated pressure fluctuations of the blades, the vortex wall, and the rear wall were then used as noise sources to calculate the sound field. The Ffowcs Williams-Hawkings (FW-H) equation was employed to predict the noise field caused by these sources. The predictions show that the rear wall and the vortex wall sources contribute significantly to the total noise and that both the predicted aerodynamic performance and noise agree well with the experimental results.
  • Measurement and analysis of tip clearance unsteady flow spectrum in axial-flow fan rotor
    LIU Bo, HOU Weimin, MA Changyou, WANG Yangang, ZHOU Qiang
    2008, 2(4): 448-452. https://doi.org/10.1007/s11708-008-0088-0
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    The dynamic pressure measurement device and test technology are described in this study. The tip clearance unsteady flow development from the inlet to the outlet of an axial-flow rotor was revealed by analyzing pressure frequency spectrum acquired from measuring the unsteady pressure field of the tip endwall. The experiment provides test basis for thoroughly understanding the tip clearance unsteady flow and building interaction models of tip clearance flow and main flow.
  • Centrifugal compressor blade optimization based on uniform design and genetic algorithms
    SHU Xinwei, GU Chuangang, XIAO Jun, GAO Chuang
    2008, 2(4): 453-456. https://doi.org/10.1007/s11708-008-0083-5
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    An optimization approach to centrifugal compressor blade design, incorporating uniform design method (UDM), computational fluid dynamics (CFD) analysis technique, regression analysis method and genetic algorithms (GA), is presented. UDM is employed to generate the geometric information of trial samples whose performance is evaluated by CFD technique. Then, function approximation of sample information is performed by regression analysis method. Finally, global optimization of the approximative function is obtained by genetic algorithms. Taking maximum isentropic efficiency as objective function, this optimization approach has been applied to the optimum design of a certain centrifugal compressor blades. The results, compared with those of the original one, show that isentropic efficiency of the optimized impeller has been improved which indicates the effectiveness of the proposed optimization approach.
  • Numerical analysis of rotating stall characteristics in vaneless diffuser with large width-radius ratio
    GAO Chuang, GU Chuangang, WANG Tong, DAI Zhengyuan
    2008, 2(4): 457-460. https://doi.org/10.1007/s11708-008-0071-9
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    A two-dimensional model, where the influence of wall boundary layers is neglected and inlet jet-wake velocity patterns are prescribed, was applied to simulate one vaneless diffuser with a large width-radius ratio. The impact of diffuser length, impeller blade number, etc. on the rotating stall was analyzed. Computational results show that a different mechanism does exist for diffusers with large width-radius ratios. Comparison with related conclusions and references is supportive of the model.
  • NO control in large-scale power plant boilers through superfine pulverized coal technology
    YIN Jie, WEI Dunsong, YIN Jie, REN Jianxing
    2008, 2(4): 461-465. https://doi.org/10.1007/s11708-008-0057-7
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    Superfine pulverized coal technology can effectively reduce NOx emission in coal-fired power plant boilers. It can also economize the cost of the power plant and improve the use of the ash in the flue gas. Superfine pulverized coal technology, which will be widely used in China, includes common superfine pulverized coal technology and superfine pulverized coal reburning technology. The use of superfine pulverized coal instead of common coal in large-scale power plants will not only reduce more than 30% of NOx emission but also improve the thermal efficiency of the boiler.
  • Flow characteristics of single-phase flow in narrow annular channels
    ZENG Heyi, SU Guanghui, JIA Dounan
    2008, 2(4): 466-470. https://doi.org/10.1007/s11708-008-0101-7
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    The characteristics of single-phase flow in narrow annular channels were analyzed and theoretical model was proposed. Based on the present model, the theoretical calculation was performed to predict the flow characteristics for the developed flow in narrow annuli with the gap sizes of 1.0, 1.5 and 2.0 mm, respectively. The results were in good agreement with the experimental data. In addition, the gap size of narrow annuli has great impact upon the flow characteristics. The decrease of gap size reduces friction factor. The higher the Reynolds number, the more remarkable the effect of gap size upon friction coefficient during single-phase flowing through narrow annular channels. The effect of gap size upon friction coefficient is dependent on the Reynolds number, and will decrease with the decrease of the Reynolds number.
  • Oxidation performance of graphite material in reactors
    LUO Xiaowei, YU Xinli, YU Suyuan
    2008, 2(4): 471-474. https://doi.org/10.1007/s11708-008-0074-6
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    Graphite is used as a structural material and moderator for high temperature gas-cooled reactors (HTGR). When a reactor is in operation, graphite oxidation influences the safety and operation of the reactor because of the impurities in the coolant and/or the accident conditions, such as water ingress and air ingress. In this paper, the graphite oxidation process is introduced, factors influencing graphite oxidation are analyzed and discussed, and some new directions for further study are pointed out.
  • Steady-state thermal-hydraulic analysis of SCWR assembly
    LIU Xiaojing, CHENG Xu
    2008, 2(4): 475-478. https://doi.org/10.1007/s11708-008-0093-3
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    Among the six gen-IV reactor concepts recommended by the gen-IV international forum (GIF), supercritical water-cooled reactor (SCWR), the only reactor with water as coolant, achieves a high thermal efficiency and, subsequently, has economic advantages over the existing reactors due to its high outlet temperature. A thermal-hydraulic analysis of the SCWR assembly is performed in this paper using the modified COBRA-IV code. Two approaches to reduce the hot channel factor are investigated: decreasing the moderator mass flow and increasing the thermal resistance between moderator channel and its adjacent sub-channels. It is shown that heat transfer deterioration cannot be avoided in SCWR fuel assembly. It is, therefore, highly required to calculate the cladding temperature accurately and to preserve the fuel rod cladding integrity under heat transfer deterioration conditions.
  • New experimental technique to determine coal self-ignition duration
    ZHANG Xinhai, XI Guang, ZHANG Xinhai
    2008, 2(4): 479-483. https://doi.org/10.1007/s11708-008-0058-6
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    An artificial neural network (ANN) model was adopted to simulate the relationship between self-ignition duration and sulfur content, ash content, oxygen consumption rate, carbon monoxide as well as carbon dioxide generation rate of coal at different temperatures of self heating process. The data from spontaneous combustion experiments were used for ANN training to obtain the connection strength between nerve cells. An oil-bath programmed temperature experiment device was designed and the experimental condition and the size of the test tube were determined for testing the oxygen consumption and the gases generation rate of coal during self-heating process. The sulfur content, the ash content and the data from the oil-bath experiment were taken as ANN inputs to calculate the experiment self-ignition duration of coal. Compared with spontaneous combustion experiment, less than 1% of coal sample and 10% of time are required with an error of less than 3 days to test self-ignition duration of coal.
  • Refrigeration cycle for cryogenic separation of hydrogen from coke oven gas
    CHANG Kun, LI Qiang
    2008, 2(4): 484-488. https://doi.org/10.1007/s11708-008-0096-0
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    Ten billion cubic meters of hydrogen are dissipated to the environment along with the emission of coke-oven gas every year in China. A novel cryogenic separation of hydrogen from coke oven gas is proposed to separate the hydrogen and liquefy it simultaneously, and the cooling capacity is supplied by two refrigeration cycles. The performance of the ideal vapor refrigeration cycle is analyzed with methane and nitrogen as refrigerant respectively. The results show that the coefficient of performance (COP) of methane refrigeration cycle is 2.7 times that of nitrogen refrigeration cycle, and the figure of merit (FOM) of methane refrigeration cycle is 1.6 times that of nitrogen refrigeration cycle. The performance of ideal gas refrigeration cycle is also analyzed with neon, hydrogen and helium as refrigerant respectively. The results show that both the coefficient of performance and figure of merit of neon refrigeration cycle is the highest. It is thermodynamically possible to arrange the refrigeration cycle with methane and neon as refrigerant, respectively.
  • Boiling heat transfer correlations for refrigerant mixtures flowing inside micro-fin tubes
    ZHANG Xiaoyan, ZHANG Xingqun, CHEN Yunguang, YUAN Xiuling
    2008, 2(4): 489-493. https://doi.org/10.1007/s11708-008-0110-6
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    Based on experimental results of ternary non-azeotropic refrigerant mixture R417A flowing and boiling in one smooth and two internally grooved horizontal tubes with different geometrical parameters, a boiling heat transfer correlations was developed for refrigerant mixtures flowing inside micro-fin tubes by applying the enhancement factor in the present modified-Kattan model which was modified by the experimental data of R417A in a smooth tube. The comparison between the calculation and the experimental results indicates that the prediction by the present correlations is in good agreement with the experiment of refrigerant mixtures inside different micro-fin tubes with a standard deviation of ± 30% for vapor qualities below 80%.
  • New refrigeration system using CO vapor-solid as refrigerant
    HUANG Dongping, DING Guoliang, QUACK Hans
    2008, 2(4): 494-498. https://doi.org/10.1007/s11708-008-0070-x
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    A refrigerant must be in the vapor-liquid phase in a vapor-compression refrigeration system, therefore, CO2 cannot be used as a refrigerant for temperatures lower than -56°C because solid CO2 will form under the triple point temperature of -56°C. A refrigeration system with CO2 vapor-solid particles as refrigerant is put forward, by which a temperature lower than the triple point is achieved. An adjustable nozzle, a sublimator, a high-pressure regulating valve and a low-pressure regulating valve are used to replace the conventional evaporator. Theoretical cycle analysis of the refrigeration system shows that its COP can be 50% higher than that of the conventional one.
  • Gas dynamic characteristic of displacer in Stirling cryocoolers
    LIU Xinguang, LIU Dongyu, WANG Yong, WU Yinong
    2008, 2(4): 499-503. https://doi.org/10.1007/s11708-008-0090-6
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    Based on the vector analysis of the dynamic characteristic of the displacer in split-type Stirling cryocoolers, experimental study was performed on a 2 W@80 K cooler to uncover the relationship among pressure fluctuation, damped impedance, inherent frequency, cold-tip temperature and the cooling performance. The result shows that the pressure amplitude and phase shift between pressure and displacer motion decrease when the cooling temperature decreases; the dynamic damp of the displacer increases at lower cooling temperature, which results in the increase of pressure drop of the regenerator, the decrease of average pressure of the cold cubage, the decrease of gas dynamic pressure, the decrease of phase shift between pressure and displacer motion, and the displacement of the regenerator and the PV power; at lower cooling temperature, the inherent frequency of the displacer increases because of the augmentation of gas spring constant. And as the inherent frequency is getting closer to the operating frequency, the drive current of the motor decreases; the piston of the compressor affects the displacer by the pressure fluctuation engendered by its motion, and the displacer reacts by changing the mass and momentum distribution to adjust the gas spring constant and the damp coefficient.
  • Applications of traditional pump design theory to artificial heart and CFD simulation
    WANG Yingpeng, SONG Xinwei, YING Chuntong
    2008, 2(4): 504-507. https://doi.org/10.1007/s11708-008-0059-5
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    A novel heart pump model was obtained by improving the traditional axial pump design theory with the consideration of working and hydraulic situations for artificial hearts. The pump head range and the velocity triangle were introduced and an iterative approach was utilized for the initial model. Moreover, computational fluid dynamics (CFD) simulations were performed to determine relevant model parameters. The results show that this procedure can be used for designing a series of high-efficiency artificial heart pumps.
  • Characteristics of force acting on adjustable axial flow pump blade
    WEI Peiru, CHEN Hongxun, LU Wei
    2008, 2(4): 508-513. https://doi.org/10.1007/s11708-008-0054-x
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    The internal three-dimensional turbulent flow of adjustable axial-flow pump arrangement was simulated, and the force acting on the blade surface was calculated under different operating conditions. Based on the calculated results, finite element method (FEM) was adopted to analyze stress and strain distributions of the adjustment blade in different operations. Hydraulic moment, centrifugal moment and friction moment which must be conquered by adjusting the blades were also calculated.
  • Chaotic behavior of LNG after stratification in main stream region of storage tank
    WANG Jingjing, MA Xiaoqian
    2008, 2(4): 514-518. https://doi.org/10.1007/s11708-008-0076-4
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    A study of the chaotic behavior of liquefied natural gas (LNG) after stratification in the main stream region of a storage tank was conducted. Based on non-linear dynamics, a 2-dimensional Rayleigh-Benard convection model was developed to simulate the convection, Lorenz equations of LNG convection were deduced from conservation equations, and the Runge-Kutta method was used to solve the equations. The results showed that when Pr = 1.33, 106 < r < 1470, chaos was obtained, which meant that the velocity field and the temperature field were highly unsteady. In addition, the influence of temperature and scale factor on the solutions and the corresponding range of parameters were studied. The results revealed that the chaos in LNG convection resulted from the interaction of buoyancy and viscid forces. A small quantity of heat impacting the storage tank would lead to a strong and unstable convection of LNG in the main stream region.
  • Application of rapid thermal processing on SiN thin film to solar cells
    LI Youjie, LUO Peiqing, ZHOU Zhibin, CUI Rongqiang, HUANG Jianhua, WANG Jingxiao
    2008, 2(4): 519-523. https://doi.org/10.1007/s11708-008-0095-1
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    Rapid thermal processing (RTP) of SiNx thin films from PECVD with low temperature was investigated. A special processing condition of this technique which could greatly increase the minority lifetime was found in the experiments. The processing mechanism and the application of the technique to silicon solar cells fabrication were discussed. A main achievement is an increase of the minority lifetime in silicon wafer with SiNx thin film by about 200% after the RTP was reached. PC-1D simulation results exhibit an enhancement of the efficiency of the solar cell by 0.42% coming from the minority lifetime improvement. The same experiment was also conducted with P-diffusion silicon wafers, but the increment of minority lifetime is just about 55%. It could be expected to improve the solar cell efficiency if it would be used in silicon solar cells fabrication with the combination of laser firing contact technique.
  • Large eddy simulation of turbulent buffet forces in flow induced vibration
    XI Zhide, CHENG Bingde, LI Pengzhou
    2008, 2(4): 524-527. https://doi.org/10.1007/s11708-008-0099-x
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    The pressure pulse filter and Smagorinsky sub-grid stress model of the Large Eddy Simulation (LES) are introduced. The fluid field in the annular plenum between the pressure vessel and the core barrel of the1:5 model in the second phase of Qinshan Nuclear Power Plant is simulated, and the distribution of the total pressure in the space and time domains is obtained. The results show that the Power Spectrum Density (PSD) of LES from the calculation and the test are in the same quantity order. Thus, the pressure of LES can be a load to stimulate the barrel vibration.
  • Supersonic flows over cavities
    FANG Tianwen, DING Meng, ZHOU Jin
    2008, 2(4): 528-533. https://doi.org/10.1007/s11708-008-0055-9
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    The characteristics of supersonic cold flows over cavities were investigated experimentally and numerically, and the effects of cavities of different sizes on supersonic flow field were analyzed. The results indicate that the ratio
  • Application of high-turning bowed compressor stator to redesign of highly loaded fan stage
    LI Shaobin, SU Jiexian, WANG Zhongqi
    2008, 2(4): 534-540. https://doi.org/10.1007/s11708-008-0066-6
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    A redesign of a highly loaded fan stage by using high-turning bowed compressor stator was conducted. The original tandem stator was replaced by the highly loaded bowed stator which was applicable to highly subsonic flow conditions. 3D contouring technique and local modification of blade were applied to the design of the bowed blade in order to improve the aerodynamic performance and the matching of the rotor and stator blade rows. Performance curves at different rotating speeds and performances at different operating points for both the original fan stage and redesigned fan stage were obtained by numerical simulations. The results show that the highly loaded bowed stator can be used not only to improve the structure and the aerodynamic performances at various operating points of the compressor stage but also to provide high performances at off-design conditions. It is believed that the highly loaded bowed stator can advance the design of high-performance compressor.
  • New response surface model and its applications in aerodynamic optimization of axial compressor blade profile
    LIU Xiaojia, NING Fangfei
    2008, 2(4): 541-549. https://doi.org/10.1007/s11708-008-0077-3
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    A parametric method for the axial compressor 2D blade profiles is proposed in which the blade geometries are defined with the parameters commonly used for blade definition, which ensures that the geometric significance is clear and an unreasonable blade profile is not generated. Several illustrations are presented to show the fitting precision of the method. A novel response surface model is proposed which regards the objective distribution function in the vicinity of a sample as normal school, and then generates the response surface function in the whole design space by a linear combination of distribution functions of all the samples. Based on this model, a numerical aerodynamic optimization platform for the axial compressor 2D blade profiles is developed, by which aerodynamic optimization of two compressor blade profiles are presented.