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September 30,2014
Volume 7,Issue 18
Pages -
Subject Area:Flowing Mechanical Engineering and Hydrodynamic Engineering,Highvoltage Engineering,Electrical Engineering,Electric Power System and Automation,Electromechanics

Title: Experiment study on the throttling characteristics of exchanging the first stage of the multistage orifice

Authors: XIE Shujuan, ZHAO Yue, CHEN Ruichi, WANG Haimin
PP: 1887-1893
Abstract: The experiment method is presented to investigate the influence of decreasing the diameter of the first stage orifice plate on the multistage throttle characteristics of the letdown orifice tube. And the test results have shown that the flow is always in the turbulent state within the measuring range and the pressure drop coun be enhanced significantly by decreasing the aperture ratio of the first stage. For each orifice plate, the resistance coefficient will eventually reach a constant with the increasing of flow rate within the section of test flow, and the constant is used as a flow rate coefficient to get the multistage throttle characteristics under the real operation condition. The orifice throttling characteristic parameters are the negative power law function of the aperture ratio of the first stage and are influenced by other factors such as the structure and shape of the orifice plate when regulating the aperture ratio. However, the aperture ratio of the first stage coun not be decreased infinitely to improve the pressure drop.
Keywords: fluid machinery and fluid power engineering; multistage orifice; multistage throttle; first stage orifice plate throttling; aperture ratio; pressure drop

Title: Study on vibration characteristics of a developed centrifugal impeller of an air compressor

Authors: ZHOU Jun’an, YANG Bin, XIAO Ping, CHEN Yanfeng, CHEN Xuejiang, LI Zaoyang, LIU Lijun
PP: 1882-1886
Abstract: Strength verification and vibration characteristics of a developed centrifugal impeller of an air compressor are studied with the finite element method. Firstly, the strength of the first stage impeller is verified. Then, the static frequencies and the dynamic frequencies at different rotation rates are obtained with a rotor dynamic analysis. Finally, the influence of the low frequency and the high frequency exciting forces caused by the impeller rotation on the impeller’s stability is analyzed. The results show that the impeller meets the requirement of strength. Both the largest stress value and the largest deformation due to vibration are located at the outlet of the impeller, where more attention should be payed during the design and operation of the compressor.
Keywords: fluid machinery and fluid power engineering; centrifugal compressor; centrifugal impeller; static frequency; dynamic frequency; vibration characteristics

Title: Static performance and modal analysis of engine crankshaft

Authors: HUANG Shuo
PP: 1874-1881
Abstract: In this paper, ANSYS Workbench software was used to build a three-dimensional model of the crankshaft, and then crank meshing and boundary conditions were imposed for crankshaft to do finite element analysis based on ANSYS. Analysis on deformation and stress state of the crankshaft was carried out, and the strength calculation and strength check of crankshaft were conducted. The results showed that the static strength safety factor of crankshaft was 8.1, the fatigue safety factor was 3.8, which both met the design requirements. This paper also made modal analysis of crankshaft based on the finite element model to calculate the first ten free vibration modes of the crankshaft and analyze the modal shapes and natural frequencies. The results showed that the lowest harmonic order frequency of crankshaft was 144.49 Hz, which was much higher than the base frequency so as to avoid the resonance frequency.
Keywords: power machinery engineering; crankshaft; finite element method; static performance analysis; modal analysis

Title: Simulation and analysis of thermoelectric dehumidification system based on equivalent circuit model

Authors: KAN Chao, SHEN Limei, CHEN Huanxin, WANG Jinshan, LIANG Ting
PP: 1866-1873
Abstract: Thermoelectric dehumidification system is a multivariable coupling system involving with heat, mass and power, and it is a relatively complex modeling. In order to simplify arithmetic, equivalent circuit model of the thermoelectric dehumidification system was established. The operating voltage, hot end thermal resistance, cold end airflow, ambient temperature and ambient relative humidity which affect the working state of the thermoelectric dehumidification system were simulated and analyzed in the PSpice. The results show that the operating voltage and the hot end thermal resistance are the main factors affecting dehumidifying performance, and it is a little influence on the dehumidifying performance after the cold end airflow reach a certain value. When the ambient temperature was 27℃, ambient relative humidity was 80%, we studied the relationship of coefficient of performance (COP) and dehumidification rate of the system with voltage, and got the possible working state of the thermoelectric dehumidification system. It also could provide certain guidance for the design and utilization of the thermoelectric dehumidifier.
Keywords: refrigeration and cryogenic engineering; thermoelectric dehumidification; equivalent electrical circuit; PSpice; operating voltage

Title: Several problems of MOA leakage current measurement

Authors: QIN Songlin
PP: 1860-1865
Abstract: Under the sine voltage, the resistive current of metal oxide arrester (MOA) leakage current is a non-sine steady-state, so MOA leakage current is a non-sine steady-state. When the sine steady-state analysis tool, i.e. phasor method is used in the study of MOA leakage current measurement, it is necessary to pay attention to the applicability problem. Through analysis of the basic principle of measuring resistive current of LCD-4 MOA leakage current measuring instrument, this paper gives the basic principle for the typical compensation method of measuring resistive current. That is, based on the power frequency sinusoidal component of MOA leakage current ahead of MOA voltage 90 Through the analysis of three-phase power frequency electric field, the paper finally gives the power frequency sine component of MOA leakage current is not just ahead of MOA voltage 90 under the three-phase operating voltage in the most substations.
Keywords: high voltage engineering; metal oxide arrester leakage current; non-sine steady-state; resistive current measurement; compensation method

Title: Modeling of OER region of PEMFC system for locomotive

Authors: LI Qi, OUYANG Yubo, YANG Hanqing
PP: 1851-1859
Abstract: In order to solve the problems of “oxygen starvation” and “oxygen saturation” for a proton exchange membrane fuel cell (PEMFC) power system of high-power locomotive under different working conditions, a lumped parameter model of PEMFC system for locomotive was established based on the operational mechanism of PEMFC system in this paper. According to various load condition, an effective division of oxygen excess ratio (OER) working region and the feasibility of OER detection in locomotive application was also achieved based on this model, and then the static performance and the stability of PEMFC system would be improved. At last, some simulations, experiments and contrastive analysis were carried out in terms of steady state response and dynamic response.
Keywords: electrical engineering; proton exchange membrane fuel cell system for locomotive; oxygen excess ratio region; system modeling

Title: One-terminal fault location for VSC-HVDC transmission lines on the basis of the distributed parameter model

Authors: SONG Guobing, WAN Qing, LIU Tian, SUONAN Jiale
PP: 1844-1850
Abstract: A novel one-terminal fault location method which is different from those based on the travelling wave theory is proposed for voltage source converter high voltage direct current (VSC-HVDC) transmission lines. Due to the high-capacity capacitors connected to both terminals of the VSC-HVDC transmission lines, the capacitor voltage will not change immediately when fault happens to the transmission lines. Therefore, the voltage of the opposite terminal to the local terminal is considered as the voltage of normal state during the fault location. Based on the distributed parameter model, the voltage and current distributions can be calculated using the voltage and current measured in the local terminal. According to the calculated distribution of voltage and current over the line, transition resistor can be computed and the fault can be located according to the principle that the variance of the calculated transition resistor is minimum at the fault point. By simulations in power system computer aided design (PSCAD) and analysis in Matlab, the fault which happens to 10%-90% of the VSC-HVDC transmission lines can be located quickly and accurately. The algorithm, which is performed in time domain, needs a very short data window and can achieve satisfactory accuracy with little need of high sample frequency.
Keywords: electric power system and automation; voltage source converter high voltage direct current transmission line; fault location; distributed parameter; one-terminal electrical quantity; time domain

Title: Calculation and analysis of permanent magnet eddy current loss with magnet segmentation

Authors: LI Ming, WANG Wei
PP: 1838-1843
Abstract: For reducing the eddy current loss of permanent magnet, lowering the temperature rise of the motor and avoiding loss of excitation caused by overheat of permanent magnet, the impact of magnet segmentation on permanent magnet eddy current loss was calculated and analyzed. An interior permanent magnet synchronous motor (PMSM) with inverter supplied was taken as an example, rated power of motor was 2.2 kW. Firstly, three-dimensional finite element model was established based on finite element software. Secondly, the model mesh and boundary conditions were dealt specially, permanent magnet eddy current loss was calculated and explained with magnet segmentation from space harmonic and time harmonic respectively. Finally, calculation results were compared and explained and a useful conclusion for high-speed PMSM design had been received, that was with the increase of magnetic pole numbers, permanent magnet eddy current loss was not always reduced, it was related to higher harmonic components of the motor input current.
Keywords: electromechanics; magnet segmentation; permanent magnet synchronous motor; harmonic; eddy current loss

Title: Analysis for the worm gear and worm driving force considering the friction force and transmission efficiency

Authors: LIU Hanzhong, MEI Ying, ZHAO Liqin, LI Yang
PP: 1833-1837
Abstract: For plenty of beginners, there are a lot of myths when they analyze the driving force of the cylindrical worm and worm gear. We attempt to find the root causing the myths by analyzing the driving force carefully. Based on the traditional method, and considering the influence of friction force and transmission efficiency on the driving force, we put forward a new method of avoiding the myth and explaining the reason why the second method is wrong. Then, with the help of Matlab software, we compare the relative errors between the new method and the traditional one. Finally, it is concluded that the two kinds of methods are equivalent.
Keywords: mechanical component and transmission; worm and gear; force analysis; parameter design; analysis of the myth

Title: Study of the abrasive flow polishing fixtures

Authors: LIU Weina, DU Qian, YANG Lifeng, ZHANG Shuren
PP: 1829-1832
Abstract: Combining the pressure, flow rate, temperature and other parameters in machine work, the working stroke and the overall structure of abrasive flow machine were determined. By calculating and studying the various parameters of the machine, the overall shape and size range of the fixture were determined. Types of surface required to be processed by different workpieces were not the same, the ways of forming abrasive flow passage by which and fixture were different. Depending on the types of fixture, the corresponding fixtures were designed. Finally, static analysis and stress-strain analysis were performed on key components of fixture in abrasive flow device by using ANSYS workbench.
Keywords: mechanical manufacturing and automation; abrasive flow; fixture; rationality

Title: Research on detection and location of steel plate crack based on the vibration response

Authors: ZHANG Xingwen, JIA Minping
PP: 1823-1828
Abstract: Considering the irregular of the crack, the crack was simulated firstly. Modal and forced vibration response characteristics of steel plate were analyzed by simulating the mode of vibration when spreading within the steel plate with/without cracks through the finite element method. A method to determine the crack was put forward in this paper based on a large damping on the mode of vibration when spreading through the crack. An experimental system was constructed to measure the displacement response of system. Finally, the feasibility of this crack detection and location method was validated by experiment and the limitations of natural frequency method were illustrated.
Keywords: mechanical manufacturing and automation; crack detection; vibration response; finite element

Title: Study on fault diagnosis of concrete pump pumping hydraulic system based on fuzzy fault tree and maintenance strategy

Authors: ZHANG Chao, CHAO Pengjun, ZHANG Jiexin
PP: 1817-1822
Abstract: In order to study the reason of the concrete pump pumping hydraulic system failure, taking the concrete pump pumping hydraulic system as the research object, the fault diagnosis method based on fuzzy fault tree theory is put forward through the analysis of working principle and failure forms of the system. The fuzzy fault tree of the system is set up and event fuzzy analysis as well as fuzzy algorithm are conducted, and the conclusion points out that the breadth-first algorithm which carries on the fuzzy fault tree analysis can be used for fault diagnosis. Furthermore, the system fault prevention and maintenance measures are put forward.
Keywords: mechanical manufacturing and automation; fuzzy fault tree analysis; fault diagnosis; concrete pump pumping hydraulic system; maintenance measures

Title: Study of intelligent fault diagnosis system for rotating machinery

Authors: YANG Mei, CHEN Sihan, YU Jianbo
PP: 1802-1816
Abstract: This paper aims to develop a monitoring and intelligent prognosis maintenance system for rotating machinery. Multilayer software hierarchical architecture-based designing scheme is adopted in this system. The key technique is the diagnosis toolbox including a large amount of time domain, frequency domain and time & frequency domain analysis algorithm which is used to realize condition-based monitoring, performance degradation assessment, performance degradation prediction and maintenance plan management. This research provides important equipment healthy information for further maintenance plan.
Keywords: mechanical manufacturing and automation; rotating machinery; fault diagnosis toolbox; performance assessment; performance degradation prediction

Title: Study on power transmission system of single-engine road sweeper

Authors: ZHOU Ji, XU Jiaolong, LEI Weiwei, QU Xiaohe, SONG Yonggang
PP: 1796-1801
Abstract: Aiming at the low of power utilization and the need of low-carbon environmental protection, based on the theoretical analysis, combined with domestic and international status of road sweeping vehicle power transmission system, this paper made a preliminary analysis and comparison on road sweeper as using double-engine or single-engine as a power source, and drew the conclusion of using a single engine as the power source for road sweeper has its advantages on the performance of economic and operational. It made an analysis and improvement on the basis of existing single-engine road sweeper power system, and made a preliminary selection of the main parts. The paper also has analyzed its economic and social benefits, so as to make some contribution for the study of power transmission system of single-engine road sweeper.
Keywords: mechanical design; single-engine; road sweeper; power transmission system

Title: Dynamic design of the quick clamping system of the press brake

Authors: WANG Yong, HU Zhongzhong, ZHANG Guofang, WANG Guangguan
PP: 1789-1795
Abstract: Efficiency of changing the upper molds largely influences the efficiency of bending works. In this paper, a hydraulic upper mold clamping system of press brake is designed. Based on the introduction of the operational principle and structural design of the clamping system, a multibody dynamics method is utilized to dynamic simulation of the key components. Finite element analysis is applied on clamping device to analyze the mechanical properties of the clamping system. The results which come from dynamic simulation and finite element analysis confirm the practicability of the upper mold clamping device presented in this paper.
Keywords: mechanical design; press brake; upper mold clamping device; quick clamping; finite element analysis; simulation

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