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November 30,2015
Volume 8,Issue 22
Pages -
Subject Area:Energy-saving Technology,Engineering Thermophysics,Electromechanics,Electrical Appliances,Electrical Engineering,Highvoltage Engineering,Electric Power System and Automation,Flowing Mechanical Engineering and Hydrodynamic Engineering

Title: Design on solar fiber lighting system based on single-chip microcomputer

Authors: QI Ji, SHI Tian, LI Nan, WU Zaijun
PP: 2410-2419
Abstract: We designed the system that can transmit the solar rays through the optical fiber directly, which is very suitable for the underground garage, oil depots and tunnel lighting. This system consists of solar tracking, light transmission, coupling, lighting, power supply and other parts. The system achieves the collection and transmission of light source based on the control of single-chip microcomputer with the Fresnel lens, coupling device and multimode fiber optical, and it tracks solar rays using pitching rotation mechanical device and two sets of sunlight testing, which avoids the disadvantages of re-tracking and blind tracking. The results show that a single system can save energy about 88.35 kWh a year directly, 47.39 kWh indirectly. If 1 000 sets of equipments are put into use, the CO2 emissions will be reduced 88 084 kg. The benefits of energy-saving and emission-reducing are significant.
Keywords: energy-saving technology; solar rays; fiber lighting; single-chip microcomputer

Title: Optimal design of wind turbine blade based on genetic algorithm and modal analysis

Authors: CHEN Wenpu, LI Chun, YE Zhou, YANG Yang
PP: 2402-2409
Abstract: This study get the optimal blade design parameters through the global optimization of the blade chord and twist angle distribution of genetic algorithm (GA) with the goal of maximizing annual generating capacity. The two blade models were established and the modal analysis was carried out based on the prestressing of the optimum rotor speed of each blade using ANSYS. The results show that, compared with Wilson’s blade, the chords, twist angles and weights calculated by GA are smaller than Wilson’s in the same rated power and wind speed. Furthermore, the second and fifth order natural frequency of GA’s blade is higher than Wilson’s blade in each optimum rotor speed, and the equivalent stiffness of flap wise and torsional vibration is better as well.
Keywords: wind energy; wind turbine; blade optimization; genetic algorithm; modal analysis

Title: Numerical simulation on catalytic combustion of premixed hydrogen and air in the micro-scale

Authors: LI Qingqing, LI Jun, CHEN Jinxing
PP: 2393-2401
Abstract: Catalytic combustion of premixed hydrogen and oxygen in a planar micro combustor with Pt catalyst was numerical simulated by using the computational fluid dynamics software FLUENT and detailed gas phase and catalytic reaction mechanism. We constructed three kinds of reaction mode, i.e. space gas phase reaction, surface catalytic reaction and space gas phase coupled with surface catalytic reaction. Then, We discussed the combustion characteristic of different reaction models and the influence of inlet flow velocity and equivalent ratio on both homogeneous and heterogeneous reaction of premixed hydrogen and air. The influence of surface catalytic reactions on hydrogen-air premixed flames was investigated by comparing differences of flame structures with surface reactions. The calculation results indicate that the axis temperature and wall temperature of both homogeneous and heterogeneous reactions increase when inlet flow velocity or equivalent ratio increases. The flame location moves downstream as the inlet flow velocity increases, and the influence of the equivalent ratio is on the contrary. The increase of inlet velocity and equivalent ratio leads to larger flame speed. Both homogeneous and heterogeneous reaction gets downstream flame position and smaller flame speed compared with free flame. The calculation results provide a theoretical basis for the application of catalytic combustion in the micro-scale.
Keywords: engineering thermophysics; catalytic combustion; micro-scale; flame location; flame speed

Title: Small size robotic joints motor’s position sensor based on linear Hall

Authors: FU Yanchao, HU Jianhui
PP: 2386-2392
Abstract: It presents a permanent magnet motor’s rotor position sensor which integrates linear Hall sensors and a specific permanent magnet ring. The principle is that the sinusoidal magnetic field can be obtained by choosing the right number of pole-pairs and optimizing the shape of magnets reasonably. The sinusoidal magnetic field is detected by two pairs of linear Hall sensors and the output signals of each pair of linear Hall sensors are composited into one signal which is related to the permanent magnet motor’s rotor position in order to compensate the signal errors of one single linear Hall sensor. The signal of rotor position will finally be gained through processing the compensated signal properly by the digital signal processing (DSP). Experimental results show that the new structure sensor can obtain comparative high accuracy of rotor position, the traditional rotor position sensors such as resolvers and photoelectric encoders can be replaced completely in the field of robotic joints, and thus it is easy for the motor of robotic joints to be miniaturization, lightweight and integration.
Keywords: electromechanics; robotic joints; permanent magnet motor; detection of rotor position; linear Hall components

Title: Calculation and analysis of three-dimensional leakage magnetic field for ultrahigh voltage autotransformer

Authors: WANG Zhenqin, YAN Xiuke
PP: 2379-2385
Abstract: The primary and secondary sides of the autotransformers have not only the coupling of magnetic field but also the connection of the circuit. Ultrahigh voltage autotransformers have a complex structure, which makes it have a very prominent problem of the electromagnetic properties in the operation of transformer. Therefore, in this study, based on the field-circuit coupled finite element method, 3D leakage magnetic field simulation of electromagnetic performance was performed under the short-circuited of a single phase three column autotransformer. The research analyzes the distribution of transformer leakage magnetic field distribution, and the loss distribution of clamp and pressing nail plate. The winding leakage magnetic field distribution of the single-phase three-column autotransformer is obtained, and the vortex distribution is optimized, moreover, the drawing board eddy current loss is reduced.
Keywords: electrical appliances; autotransformer; leakage magnetic field; field-circuit coupling; finite element; eddy current loss

Title: Research of neutral voltage balance for Vienna rectifier

Authors: MA Pengpeng, TONG Zhaoping, YANG Wei, YANG Shiyan
PP: 2372-2378
Abstract: Although Vienna rectifier has many advantages such as high power factor, simple circuit structure, low voltage stress of power device etc, while it has the problem of the neutral voltage fluctuation. According to the problem of the neutral voltage fluctuation affecting the working process of the Vienna rectifier, this paper analyzes the three phase duty ratio signals so as to effectively control the neutral voltage fluctuations by changing the zero sequence vector function-time ratio and neutral voltage at the output side. Finally, this paper built the simulation model for validation. Through theoretical analysis and simulation, it can be proved that changing the zero sequence vector function-time ratio can control neutral voltage simply and effectively.
Keywords: electrical engineering; power electrical; Vienna rectifier; space vector pulse width modulation; neutral voltage

Title: Research on the indoor air purification by plasmas with water vapor sol

Authors: LI Ce, LI Xuanjiannan, LIU Dingxin, WANG Xiaohua, RONG Mingzhe
PP: 2366-2371
Abstract: In this paper, we present a novel approach by combining the cold plasmas with water vapor sol to benefit the production of oxygen anion which is good for health, with the removal of floating dust, and the control of by-products. The water vapor sol generated by ultrasonic atomization flows through a line-cylinder reactor, on which a sinusoidal high-voltage is applied for the plasma generation. It is found that: 1) the water vapor sol can greatly improve the production efficiency of oxygen anion; 2) the removal of floating dust is efficient, and the efficiency increases with the applied voltage; 3) the concentrations of O3 and NO2 are much lowered by the water vapor sol, and they are lower than the national standard levels when the applied voltage is not higher than 8 kV.
Keywords: electrical engineering; high voltage technology; plasma; oxygen anion; air purification; ozone

Title: Experimental study on sliding electrical contact of copper-aluminum pairs in an electric-tribo-tester

Authors: XU Kai, CHEN Lixue, XIA Shengguo, HE Junjia
PP: 2357-2365
Abstract: In this paper, we research sliding electrical contact friction and wear between a rotating copper disk and stationary aluminum (Al-6063 and Al-7075) pins with flat tips based on electric-tribo-tester. Electrical current is supplied by a programmable 200 A power supply. Operating conditions of the experiments are designed to yield the contact pressures of 0.2-6.4 MPa, electrical current densities of 0-4 MA/m2 and sliding speeds of 5-50 m/s. Friction coefficient is measured automatically in the electric-tribo-tester. The wear of the pins is quantified by their mass and length changes. The surface morphology of the contact surface is observed by using scanning electron microscopy (SEM). Furthermore, in some typical area, the microanalysis is performed also by SEM, in order to figure out if there is any change in the surface chemical compounds which was consequence to the electric sliding contact process. The results of experiments show that friction coefficient is about 0.10-0.35. The measurements of the wear on the pins show that armature’s wear has no significant relationship with the change of current density, contact pressure or speed. With the increasing of current, surface morphology and chemical compounds of pins become more complex and more multiplex.
Keywords: highvoltage engineering; sliding electrical contact; copper-aluminum pairs; electric-tribo-tester; friction coefficient; wear

Title: Several problems of MOA leakage current measurement (continued)

Authors: QIN Songlin
PP: 2348-2356
Abstract: This article continues the discussion about several problems of metal oxide surge arrester (MOA) leakage current measurement, including the most reliable method of measuring MOA resistive current that is capacitance bridge method; the MOA leakage current standard wave and standard wave generator which are in accordance with MOA leakage current measurement characteristics; MOA resistive current Tester test questions of measuring performance as well as on-line MOA leakage current monitor calibration and inspection issues. Finally，the problems of new intelligent on-line MOA leakage current monitor are also discussed.
Keywords: highvoltage engineering; MOA leakage current; resistive current; capacitance bridge; standard wave generator; calibration

Title: Breeze vibration response analysis of carbon fiber composite aluminum wire

Authors: LI Yongping, ZHANG Jibin, YAN Dongxue
PP: 2342-2347
Abstract: We combined with dynamic method and the method of energy balance, considering the static linear, the conductor structure under the common effect horizontal tension and wire bending stiffness, using mathematical analysis method, researches the actual conductor structure form of the breeze vibration equation. In combination with carbon fiber composite conductor and strain clamp, hanging clamp connection characteristics, the carbon fiber composite conductor boundary conditions were determined. Then the actual carbon fiber composite conductor breeze vibration equations of concrete form were obtained by the boundary conditions substitutting into breeze vibration equation. Research results provide the reliable theory for mechanism of wind vibration analysis and provide analysis basis for the measures research of breeze vibration suppression of aluminum composite carbon fiber core.
Keywords: power transmission and distribution engineering; carbon fiber composite aluminum wire; static linear; breeze vibration; mathematical analysis

Title: Application analysis interpolation of improved algorithm based on window FFT in the harmonic detection

Authors: QIU Wei, LI Yamei, WANG Zhiguo
PP: 2336-2341
Abstract: In this paper, the window fast Fourier transform (FFT) was studied, and FFT was improved using interpolation method, and this paper proposed an effective interpolation method based on harmonic elimination method. By comparison between theoretical knowledge and the simulation experiments, it was proved that the improved method can effectively alleviate formation of leakage and barrier effect. This method can be used to accurately read every harmonic amplitude and phase, which is of great help for every harmonic analysis in the future, and provides convenience for harmonic governance and management.
Keywords: power electronics; windows and interpolation fast Fourier transform; electric power system analysis; amplitude of harmonic elimination; harmonic detection

Title: Precise measurement and validation of nonlinear inductance of switched reluctance motor

Authors: WANG Fengchao, GONG Liang, LI Bingchu, LING Xiao, LIU Chengliang
PP: 2329-2335
Abstract: The inductance characteristics of the switched reluctance motor (SRM) possesses strongly nonlinearity due to doubly salient structure and its intentional operation in deep magnetic saturation for higher power density, which poses challenges for accurate measurement of the inductance with respect to the exciting current and rotor position. An inductance measurement method is proposed on the basis of an SRM electromagnetic model, which clarifies the discrimination between the incrimental inducatance and the phase inductance. The proposed measuring approach exerts pulse voltage on a given stator winding, and measures the current profile to obtain the inductance under the varying current. The proposed method utilizes the equipped power circuitry without the need of specifically designed instrumentation and completely replicates the SRM operational scenario, thus it realizes the full-range data-acquiring and minimizes the modeling errors. These merits help to obtain an accurate full-range incremental or phase inductance under different rotor position and phase current, which renders a parameterized 3D mesh for the SRM stator inductance. Furthermore, a novel cross-validation experimentation according to the magnetizing and demagnetizing status measurement verifies the feasibilities and accuracy of the proposed inductance measuring method.
Keywords: power electronics; measurement; switched reluctance motor; inductance; nonlinearity; cross validation

Title: Transient security risk assessment of power system with large scale wind farm based on k-means clustering

Authors: LIANG Lilong, BAI Xuefeng
PP: 2320-2328
Abstract: In this paper, the risk indicator is defined by the severity and wind speed probability model based on the theory of risk. The stability margin, as a physical indicator to characterize the intrinsic properties of the system, is used to indicate the severity of contingency. And the clustering analysis theory is applied to the risk analysis, the k-means clustering method is used to comprehensively evaluate transient security of power system. The risks are classified and divided effectively by selecting the number of clusters with the actual situation. Finally, the effectiveness of the proposed method is verified through the simulation example. The result verifies the accuracy and practicality of this method, which has certain practical significance.
Keywords: electric power system and automation; transient stability; wind power; stability margin; risk assessment; k-means clustering

Title: Effect of gap between square cylinder and splitter plate on flow characteristics

Authors: LI Jinsheng, ZHANG Li, DING Lin, YANG Zhongqing
PP: 2310-2319
Abstract: To reveal the flow and wake vortex-shedding characteristics over a square cylinder with a detached splitter plate, a numerical study of square cylinder with splitter plate was conducted at low Reynolds number (Re=150) in flow channel. The force acted on the square cylinder and plate, the wake characteristics, flow channel wall and regimes of the flow were discussed. The results show that, for the flow channel with blockage ratio of 1/6, when the gap G which is the distance between cylinder and plate is varied from 0-7D with a constant plate length of D, the behavior of the flow can be grouped into two regimes, and the critical gap distance is observed to occur at G=2.60D. When 0 Keywords: flowing mechanical engineering and hydrodynamic engineering; square cylinder; splitter plate; blockage ratio; flow characteristics; vortex shedding

Title: Study on shock wave characteristics in variable nozzle turbine

Authors: XU Jianhui, QI Mingxu, SHI Xin
PP: 2303-2309
Abstract: With the purpose of investigating the shock wave characteristics, this research is carried out on JK90S variable turbine, and the nozzle shock wave sweeping behavior is investigated under the conditions of two kinds of openings and three kinds of expansion ratios. The results indicate that under the same expansion ratio condition, the shock wave generated in the nozzle is stronger in 20 opening than that in 15 opening with the shock wave position shifted downstream-wise. With the increase of the turbine expansion ratio, the strength of the shock wave in nozzle increases and the position is shifted upstream-wise. During the process of the rotor blades from toward the nozzle to far away the nozzle, the nozzle shock wave always exists, with its strength and position decided by the relative position between nozzle and impeller.
Keywords: power machinery engineering; radial flow turbine; variable nozzle; shock wave

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