共查询到20条相似文献，搜索用时 31 毫秒
1.
We used computational fluid dynamics （CFD） and mode superposition method instead of the energy balance method to compute transmission line aeolian vibrations induced by the Karman vortex. Firstly, we obtained the wind power inputs using CFD theory. The result is effective for aeolian vibration analyses compared with the power which were measured in wind tunnel tests. Then a new aeolian excitation was derived using the wind power equivalent principle, and the aeolian vibration distribution along transmission lines and the wind power input obtained by CFD can be account. Secondly, we formulated the motion equation of a conductor-damper system and derived a semi-analytial solution using the mode superposition method. The Stockbridge-type dampers attached were simplified to the forces transmitted by the clamps. Finally, the semi-analytical solution can be solved by iterative methods. Taking a 1 000 kV Ultra High Voltage transmission line as an example, we analyzed the line with and without dampers by the semi-analytical solution. Compared with the results which were computed by the energy balance method, the semi-analytical solution is precise enogh for aeolian vibration analyses. Besides, we also analyzed the influence of damper position and quantity. 相似文献
2.
The overvoltage phenomena of ultra high voltage (UHV) transmission lines are analyzed and verified by EMTDC/PSCAD simulation. Referring to the theoretical analyses and operating experiences of extra high voltage (EHV) transmission lines in China and UHV transmission lines in Russia and Japan, the methods to suppress the internal overvoltage in UHV transmission lines by protection and control strategies are discussed. Through the cooperation among the recloser, shunt reactor, tripping and closing resistance, and metal oxide varistor (MOV), the overvoltage can be restrained within an acceptable level. 相似文献
3.
Installation of rail vibration dampers (rail dampers for short) onto rails between sleepers is one of the measures to control rail noise generation and roughness growth. Amid the rapid expansion of high-speed and underground railway networks in China, many suppliers are actively marketing and promoting their products, often giving confusing information. In this paper, a parametric study is used to investigate the effect of rail dampers on the dynamical behavior of a Chinese high-speed railway track. The Fourier transform-based method developed for analyzing dynamics of a railway track as an infinitely long periodic structure, with or without rail dampers, is applied in the investigation. It is hoped that results in this paper can help develop the understanding of the working mechanism of rail dampers, and provide useful information for product design and application. 相似文献
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This paper presents a type of vibration energy harvester combining a piezoelectric cantilever and a single degree of freedom (SDOF) elastic system. The main function of the additional SDOF elastic system is to magnify vibration displacement of the piezoelectric cantilever to improve the power output. A mathematical model of the energy harvester is developed based on Hamilton??s principle and Rayleigh-Ritz method. Furthermore, the effects of the structural parameters of the SDOF elastic system on the electromechanical outputs of the energy harvester are analyzed numerically. The accuracy of the output performance in the numerical solution is identified from the finite element method (FEM). A good agreement is found between the numerical results and FEM results. The results show that the power output can be increased and the frequency bandwidth can be improved when the SDOF elastic system has a larger lumped mass and a smaller damping ratio. The numerical results also indicate that a matching load resistance under the short circuit resonance condition can obtain a higher current output, and so is more suitable for application to the piezoelectric energy harvester. 相似文献
6.
功率因素的高低关系到输配电线路、设备的供电能力,也影响到其功率损耗。分析影响功率因数的主要原因,论述无功补偿的合理配置原则及低压电网无功补偿的方法,说明采用无功补偿技术能提高低压电网和用电设备的功率因数,可达到节能降损的目的。 相似文献
7.
沈华嘉 《广东教育学院学报》2003,23(2):38-40
通过对进入电阻和电容器内的能流的计算，分析了电源能量的传输问题．结果表明，电源的能量是通过电磁场传输出去的，通电电线的作用是提供所需的电磁场． 相似文献
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9.
涂杰 《宁波职业技术学院学报》2010,14(5):92-93,100
为了减少机械伺服系统中机械传动的能耗,提出并分析了通过优化传动系统中齿轮减速传动比来减少能耗的方法,并与传统的惯量匹配法进行比较。结果表明,应用优化齿轮减速比方法可以比惯量匹配法大大减少了能耗。 相似文献
10.
根据 Ed和 Ie动力系统的分形与混沌内在属性——短期演化行为的可预测性和长期演化行为的概率特征 ,分别探讨其长短期行为演化规律 .根据短期行为的预测结果 ,探讨了实际工程结构中的主被动抗震参数控制、在役维护的确定以及系统输入能量优化等问题 ;根据长期行为的概率预测结果 ,对实际工程结构中的抗震设计概率、在役维护概率、地震危险性与地震危害性进行了分析 ,为抗震理论和分析方法以及控震减震规律的实际应用提供了一定的参考价值 相似文献
11.
The paper studies photon-associated transmission through a quantum wire with a side-coupled stub tuner,to which an external microwave field applies,in terms of the approach developed by Cai.The inelastic scattering of an incoming electron and thd photon field lead to photon-electronic transmission though quantum wier.It is found that single photon absorbing (emitting) of the incoming electron in the stub can bring about antiresonant transmission in the quantum wire.The influence of the feedback mechanism from inelastic scattering process on elastic channel transmission is also examined.Total transmission coefficient as a function of photon energy exhibits non-periodic oscillation peaks.With the increasing of photon-electron coupling constant,the amplitude of these oscillation peaks enhances. 相似文献
12.
Dynamic characteristics analysis of a misaligned rotor-bearing system with squeeze film dampers 总被引：1，自引：0，他引：1
In this paper, a dynamic model is established for a two-stage rotor system connected by a gear coupling and supported on ball bearings with squeeze film dampers (SFDs). The nonlinear dynamic behavior of the rotor system is studied under misalignment fault condition. The meshing force of the gear coupling is calculated considering the deformation of the tooth caused by torque transmission and dynamic vibration. The contact force between the ball and race is computed based on the Hertzian elastic contact deformation theory and the elastohydrodynamic lubrication theory. The supported force of SFD is simulated by integrating the pressure distribution derived from Reynolds’s equation. The equations of motion are rewritten in non-dimensional differential form, and the fourth-order Runge-Kutta method is employed to solve the nonlinear dynamic equilibrium equations iteratively. To verify the validity of the dynamic model and the correctness of the numerical solution method, the experimental power spectra of the rotor system under various misalignment degrees are compared with the analytical results. The effects of several important parameters, such as the lubrication of the ball bearing, the centralizing spring stiffness, the radial clearance of SFD, and the misalignment of gear coupling, on the dynamic characteristics of the rotor system are investigated and discussed mainly focusing on the system stability. The response spectra, bifurcation diagrams, and Pointcaré maps are analyzed accordingly. These parametric analyses are very helpful in the development of a high-speed rotor system and provide a theoretical reference for the vibration control and optimal design of rotating machinery. 相似文献
13.
桁架式结构因可提供较大的抗弯刚度,常常是大跨度结构的首选。基坑工程的围护桩是一种需要提供较大抗弯刚度用于承受横向力的受弯构件,桁架结构则是一种最合理的选择。液压高频振动锤可以提供较高的振动频率和激振力可确保在软土、砂砾和卵石层中将装配好的长方形空间桁架振动沉入地基中,使钢桁架桩在软土基坑中得以实施。与现今流行的支护结构相比,钢桁架桩可回收满足节能环保要求,结构受力明确,构件可在工厂进行标准化制作现场拼装,其质量可控,施工工期短,同时还可重复使用基坑监测测试原件。因此具有较高的经济与社会效益。 相似文献
14.
金皖东 《山东商业职业技术学院学报》2021,(2):104-106
针对目前道路发电技术存在的技术复杂、造价昂贵、维护困难等问题,提出一种道路压力发电系统设计方法,主要进行了压力发电系统的结构设计。设计了承重机构、传动机构、加速及发电储电机构;设计与分析了压力发电系统的工作原理;阐述了压力发电系统的创新点。通过这一系列的设计与研究,为新型绿色能源的收集探索新的路径,为新型绿色能源的研究提供新的思路。 相似文献
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在500kV鲲东甲乙线改造工程中,采用旧导线置换导引绳的方法,减少了人工展放导引绳的工作量,且有效克服了地形条件恶劣、工期紧、青赔难度大的特点,取得了良好的经济效益和社会效益。本文对上述施工中的旧导线置换导引绳技术,阐述其作业步骤及其关键技术要点,希望对于以后类似的改造工程有积极的指导作用。 相似文献
16.
利用载波或微波通道实现的方向保护最适用于远距离超高压输电线路,在电力系统中得到广泛应用,这种保护的关键元件是用于判别故障方向的方向继电器．为了克服传统方向元件的缺点,提出基于人工神经网络的方向高频保护,通过电磁暂态仿真程序（ＥＭＴＰ）的广泛测试,证明基于人工神经网络的方向高频保护在任何运行状态和故障条件下都能正确识别被保护输电线路的各种故障模式（如故障方向和相别）,完全满足超高压输电线路对保护的要求． 相似文献
17.
The conventional fault analysis method based on symmetrical components supposes that the three-phase parameters of un-transposed transmission line are symmetrical in case of fault. The errors caused by the method with the symmetrical distributed parameter circuit model as the equivalent circuit of the un-transposed ultra high voltage (UHV) transmission line were studied under both normal operation and fault, and the corresponding problems arising were pointed out. By contrast with electromagnetic transient and power electronics (EMTPE) simulation results with the asymmetrical distributed parameter circuit model of un-transposed line, it is shown that the conventional method cannot show the existence of negative and zero sequences before fault happening and there are many errors on voltage and current after fault happening which are different with fault types. The error ranges of voltage and current are 2.13%-81.13% and -7.82%-86.15%, respectively. 相似文献
18.
Hao WANG Tian-you TAO Huai-yu CHENG Ai-qun LI 《浙江大学学报(A卷英文版)》2014,(10):798-812
研究目的：为超大跨度斜拉桥抗风设计与抖振控制提供参考。研究方法：基于ANSYS建立了苏通大桥三维有限元模型,并在MATLAB平台模拟了苏通大桥三维脉动风场。考虑主梁断面气动自激力,进行了苏通大桥抖振时域分析。根据苏通大桥动力特性和抖振时域分析结果,重点分析了多重调谐质量阻尼器（MTMD）用于抖振控制的参数敏感性。考虑MTMD的控制效果、建造费用、施工难度及鲁棒性等因素建立了关于MTMD设计参数的目标函数,并基于一阶优化算法进行目标函数最优解的非线性搜索,据此获得了MTMD在约束条件下的最优设计参数。重要结论：1.苏通大桥侧向抖振位移主要由第一阶侧弯振型控制,竖向抖振位移主要由第一阶竖弯振型控制;2.MTMD的控制效果对设计参数的变化十分敏感,其中质量比和频带宽敏感性更强;3.MTMD的最优设计参数可以通过一阶优化算法获得,并可通过零阶优化算法对优化结果进行验证;4.采用优化后的MTMD设计参数,苏通大桥的抖振响应可以得到明显抑制,且侧向抖振控制效果更加明显。 相似文献
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对于电力工程建设费用的非线性问题，基于灰色系统理论，提出了一种成本费甩顸测与时间成本优化决策的新方法。 相似文献
20.
弹性地基上四边自由矩形大挠度薄板的自由振动 总被引：1，自引：0，他引：1
考虑具有粘滞阻尼的Winkler地基上四边自由受简谐激励的矩形板的偏微分方程组,找到了满足所有边界条件的近似挠度函数,利用Galerkin方法把偏微分方程表示的非线性动力学方程转化为用常微分方程表示的非线性动力学方程。在KBM法的基础上,引入谐波平衡的观点研究了弹性地基上四边自由无阻尼矩形板自由振动,应用Hamiltonion函数研究了系统能量与周期的关系。 相似文献