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April 30,2013
Volume 6,Issue 8
Pages -
Subject Area:Electrical Engineering,Electric Materials,Engineering Thermophysics

Title: Application of object-oriented method in distance measuring system of traveling waves

Authors: ZHANG Ke, QIU Xinhong, WANG Xiao, WANG Hao
PP: 782-786
Abstract: The theory based on fault distance information of transmission lines through transient travelling waves has been widely studied and applied. However, sine the traditional analysis is very complex, it affects the accuracy of measurement. To solve these problems, this paper presented a wavelet-based and object-oriented method to achieve the traveling wave data analysis system. In this system, travel wave data analysis could be obtained from the properties of the lines and its analytical methods, and the ranging information could also be obtained from the traveling wave data. The ranging device based on this analysis system operation showed that the mentioned theory and method was correct and effective.
Keywords: electrical engineering; traveling wave; wavelet transform; object oriented method; fault location

Title: Measurement research on magnetic properties of electrical sheet steel in the DC bias condition

Authors: CHEN Dezhi, BAI Baodong
PP: 776-781
Abstract: In order to reveal the accurate analysis and judgment on the operating characteristics of transformer under the DC bias, this study utilized two Epstein square devices to measure the magnetization curves of some certain transformer which used the 30ZH120 electrical sheet under four different overlaping joints. This paper provided the measure method of the DC bias magnetic density under laboratory conditions and offered the bias magnetization curves and the loss curves. The consequence comparison between the electrical sheet and the transformer model showed that direct-oblique way lap could more realistically reflect the magnetization characteristic of transformer working in the DC bias conditions. Therefore, this research provided a convenient measurement methods for large transformer which was difficult to measure the magnetic properties, and offered the experiment basis to the theory study of the DC bias transformers.
Keywords: electric machines and appliances; electrical steel sheet; DC bias; Epstein square device; experiment

Title: Experimental study of the running-in influence on the PM emission from a diesel engine

Authors: LU Ye, XUE Dongxin, SONG Xigeng
PP: 771-775
Abstract: This paper mainly expounded two methods of testing the particulate matter (PM) emission from the diesel engine: the constant volume sampling system (CVS) and the partial flow sampling system (PFSS). Through comparing these two methods, PFSS method was selected as the basis of the research. Armed with the AVLSPC472 particle sampling device, the PM emission before and after the running-in of a V-type-16-crock diesel engine was measured. Furthermore, the emission load was obtained through calculation. By comparing the test results, the PM emission was found to be reduced after the running-in period.
Keywords: power machinery and engineering; diesel engine; particulate matter emission; partial-flow dilution sampling system; running-in

Title: Interaction investigation of deterministic unsteady flow in a radial turbine with guide vanes

Authors: LIU Yinhong, LAO Dazhong, CHUANG Lu, ZHAO Ben, YANG Ce
PP: 765-770
Abstract: The interaction between the guide vanes and rotor can influence the aerodynamic performance, noise and fatigue life of blades, and the wake from guide vane is a main resource for the interaction. In this paper, a 3-dimension numerical simulation was performed in a radial turbine with guide vanes to focus the interaction between guide vanes and rotor blades. The results showed that a high pressure field could be induced by the leading edge of the rotor due to the blocking. Furthermore, the wake of the guide vane oscillated with a certain amplitude due to that the pressure gradient exited along the circumferential direction, and the oscillation phenomenon was extremely obvious near the hub. Meanwhile, the guide vane’s wake transported downstream with a limited distance and could not be founded at outlet of the rotor.
Keywords: power machinery and engineering; guide vane; radial turbine; interaction; unsteady

Title: Simulation study of diesel spray combustion and emission characteristics in active thermo-atomsphere

Authors: BAO Tangtang, FENG Wei, DENG Jun, WU Zhijun
PP: 759-764
Abstract: The combustion and emission characteristics of diesel spray were studied in a controllable active thermo-atmosphere by numerical simulation method. The auto-ignition delay and auto-ignition site of diesel spray at atmospheric pressure and high pressure were also calculated. Furthermore, the auto-ignition delay of diesel spray, the flame stabilization and the effect of the co-flow temperature were analyzed. Then, the emission characteristics of soot and NO were also studied. The results showed that the auto-ignition delay of diesel spray decreased with the increasing of atmospheric pressure, while the emission of soot and NO increased. The harmful gas could be reduced by reducing the co-flow temperature while keeping the stable flame.
Keywords: internal combustion engine engineering; diesel; spray; active thermo-atmosphere; combustion; emission

Title: Mixed lubrication simulation analysis on main bearings internal combustion engine considering the surface roughness

Authors: HE Tao, ZOU Dequan, LU Xiqun, GUO Yibin, LI Wanyou
PP: 752-758
Abstract: The mixed lubrication of main bearings was analyzed using the average Reynolds equation considering the surface roughness. The simulation results indicated that the surface roughness between main bearings and main bearing journals had great effects on the lubrication properties. When surface roughness of bearings was considered, the bearings orbits changed greatly, the least oil film thickness increased obviously, while the end flow-rate and highest film pressure changed little in the most time of a duty cycle. In addition, the increase of surface roughness within a certain range was benefit for the film formation at lubricant surface. However, since the asperity contact pressure was also increased, the ratio of film thickness and roughness decreased, which made the lubrication of main bearings become worse.
Keywords: internal combustion engine engineering; lubricant property; simulation analysis; main bearings; surface roughness

Title: Theoretical research on chemical desorption of CO2 in a horizontal-tube falling film evaporation

Authors: YANG Luopeng, XU Zhexuan, ZHANG Xiaohong, HU Huawei
PP: 747-751
Abstract: In order to effectively reduce negative influence of non-condensable gas (NCG) on horizontal-tube falling film evaporation and improve the thermal conductivity efficiency of falling film evaporation, a model of CO2 chemical desorption was presented. The CO2 desorption rate distributions in different units of individual evaporator and different evaporators were obtained by simulating an actual multi-effect distillation (MED) setup. Compared with practical operation data of a MED desalination plant, the presented models were proved to be reliable. The results indicated that the CO2 desorption rates decreased stage by stage mainly due to the reduction of the mass transfer coefficients and the chemical reaction rate with a decrease in evaporation temperatures in evaporators. The evaporation temperature was the key factor influencing the CO2 chemical reaction rate. The chemical desorption rates were identical to the physical desorption rates. The released NCG had significantly negative effect on the internal condensation.
Keywords: thermal engineering; CO2 chemical desorption; horizontal-tube falling film evaporation; mathematical simulation; chemical reaction

Title: Effect of ultrasonic pretreatment on pore size distribution in sludge

Authors: ZHAO Fang, LI Dong, CHEN Zhenqian
PP: 742-746
Abstract: The sludge pore structures after ultrasonic pretreatment were studied by optical microscopic and the effect of ultrasonic energy density and processing time on sludge internal aperture distribution was analyzed. The results indicated that the ultrasonic pretreatment could effectively change the sludge pore structure and the sludge inner average pore size gradually increased with the increasing of the energy density in the same processing time. Meanwhile, the sludge inner average pore size increased with the increasing of processing time in the same ultrasonic intensity. When the ultrasonic energy density was 0.8 W/mL and the processing time was 7 min, the sludge could obtain the best pretreatment effect.
Keywords: engineering thermophysics; ultrasonic pretreatment; pore distribution; sludge

Title: A predictive model of nucleate pool boiling on the heated surface with changing contact angle

Authors: LI Yuanyang, LIU Zhenhua
PP: 735-741
Abstract: Experimental study and semi-theoretical analysis were conducted on the nucleate pool boiling characteristics of the heating surface with changing contact angle. Since the semi-analytical modeling framework of Benjamin and Balakrishnan did not consider the effect of contact angle, combining with the above model and the effect of contact angle, a revised semi-analytical model was proposed in this paper. Based on the coupling relation of the bubble growth time and the bubble departure diameter, the selected correlation of bubble departure diameter could be used to directly calculate the bubble growth time and the microlayer area under the bubble with changing contact angle. These improvements make the present model be suitable for the heating surface with changing contact angle. Rules and effect of contact angle on the nucleate pool boiling characteristics of heating surface were also obtained from the semi-analytical model. In addition, the predicted results were in good agreement with experimental results on hydrophilic heating surface.
Keywords: engineering thermophysics; boiling; contact angle; heat transfer characteristics

Title: The development and experimental study of polishing instrument in the internal surface of the elbow pipe and irregular bend pipe

Authors: LIU Weina, QU Pingping, ZHANG Yaojuan, YANG Lifeng
PP: 728-734
Abstract: Finishing in the inner hole surface of elbow pipe and irregular bend pipe is a thorny problem, according to this problem, this study developed a new type of polishing instrument, which was suitable for finishing machining in the inner hole of the pipe, placing in the internal cavity of work piece. This instrument was comprised of polishing head, matching process equipment and fixture. It was worth pointing out that the sphere polishing head was dragged by the flexible line carrying on the rotating polishing processing. The experimental study showed that this instrument could successfully realize the micro processing of deburring and polishing in the whole internal surface of the elbow pipe and irregular bend pipe, which had incomparable advantage to other methods. Furthermore, the polishing instrument effectively solved the finishing machining problem in the whole inner surface of the elbow pipe and irregular bend pipe. Moreover, the processing had certain accuracy, stability, flexibility, environmental protection and economy, which made the parts performance improved and life extended. At the same time, the relief complicated manual labor and the labor intensity were greatly reduced.
Keywords: machanical manufacturing automation; polishing machining; elbow pipe; irregular bend pipe; internal surface; polishing head

Title: Microstructure transform behavior of large heat input weld metals with rare earth Ce

Authors: YU Shengfu, DENG Yu, HUANG Anguo, XU Huizi, YAN Ning, PU Juan
PP: 721-727
Abstract: In this paper, the microstructure transform behavior of the large heat input weld metals with rare earth Ce was studied and the weld thermal cycle curves of double-wire submerged welding were measured. The results showed that the weld metal by double-wire submerged welding had one time thermal cycle coarse-grained heat affect zone (CGHAZ) and two time thermal cycle intercritically reheated coarse-grained heat affect zone (IRCGHAZ). The microstructures of the large heat input weld metals were comprised of acicular ferrite (AF) and proeutectoid ferrite induced by Ce oxide sulphide particles. The microstructures of CGHAZ and IRCGHAZ were comprised of AF, sympathetic acicular ferrite（SAF）, proeutectoid ferrite and grain bainite. The first AF with high density dislocation could induce SAF nucleation. The place of the AF inducing SAF nucleation had transfixion curve. The grain bainite nucleated in the austenitic zone with high carbon content was closed to AF and SAF. The microstructures of the large heat input weld metals with rare earth Ce had ability to grain self-refinement, which made it high notch toughness values at low temperature.
Keywords: welding technology and equipment; microstructure transform; large heat input; weld metal; acicular ferrite; rare earth Ce

Title: Dynamic analysis of misalignment fault in a compressor unit

Authors: MA Hui, SONG Rongze, NIU Heqiang, NAI Haiqiang
PP: 716-720
Abstract: In this paper, taking compressor unit as the research object, using ANSYS finite element software, the expression of the excitation force was deduced based on coupler deformation geometric relations and stress analysis. Furthermore, the dynamic model with angle misalignment fault was established based on equivalent shaft section method, and the radial vibration responses of the low pressure rotor were simulated under varying degrees of angle misalignment fault. The research showed that with an increasing amount of the misalignment, the rotor vibration increased and the misalignment fault became more evident. Meanwhile, the ratio of the double frequencies increased and the shaft center orbit presented a “banana” shape or “8” shape. This research provides theoretical basis for the study of misalignment fault of the coupler.
Keywords: mechanical dynamics and vibration; compressor unit; coupler; misalignment; vibration

Title: New insights on degree of “freedom” and “mobility” of mechanisms

Authors: DING Xilun, XU Kun
PP: 712-715
Abstract: In this paper, the degree of mobility was introduced since the degree of freedom in “Mechanical principles” and “Robotics” had two meanings. degree of freedom and degree of mobility of mechanisms were redefined and given the definitions of independent degree of mobility, partial degree of mobility, passive degree of mobility and limited degree of mobility. The degree of mobility indicated the whole structure of the mechanism, while the independent degree of mobility and partial degree of mobility reflected the inputting characteristics of the mechanism and degree of freedom reflected the outputting characteristics of the mechanism. The differences between degree of freedom and degree of mobility clearly showed the input-output characteristics of mechanisms.
Keywords: mechanism principles and mechanism; degree of freedom; degree of mobility; input-output characteristics

Title: Study on the problem of frosting at the cold surface

Authors: LI Weiwei, JIN Jingfu, CHEN Tingkun, CONG Qian, QI Yingchun
PP: 706-711
Abstract: Frost exists generally in various engineering application, it seriously affects the normal operation of those equipments. Frosting process is complicated and difficult to control. The deep research on the frosting and its rules is very important. The domestic and overseas scholars had done a lot of researches on frost phenomena, frost rule and frost mechanism, and achieved very good results. At the same time, some problems were also found. In this paper, based on the summarizing the frosting research process, the current situation about the frost dynamic influence factors, frost layer property and frost layer growth law were described in details. Furthermore, the problems existing in the research process of the frosting were also briefly analyzed.
Keywords: other subjects of mechanical engineering; frosting; review; influence factors; physical property; growth law

Title: Research progress of aircraft integral panel forming method and numerical simulation

Authors: YAN Yu, WAN Min
PP: 697-705
Abstract: With the high efficiency, light weight and good rigidity, integral panels have been widely used in aeronautic and astronautic aircrafts. However, the forming of the integral panels is difficult and many problems still remain. The research of the accurate and high-efficiency integral panel forming methods have become an important research aspect of aeronautic manufacturing engineering. In this paper, the classifications, advantages, characteristics and applications of the aircraft integral panels were introduced. Then the principles, advantages and disadvantages of some main forming methods were analyzed, and the applications of those forming methods on many types of aircrafts were also presented. Finally, with a mainly revision of the numerical simulation method used in the sheet metal forming, the research progress of numerical simulation in the integral panel forming was depicted.
Keywords: plastic forming processing and equipment; sheet metal forming; review; integral panel; forming method; numerical simulation

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