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It is proposed that the mechanical state of turbogenerators be regularly monitored by photoelectric chronometric recording of low-frequency torsional vibrations of their shafts. The vibrations are caused by small sudden changes which are continuously occurring in the operating parameters of the turbine unit. 相似文献
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Random harmonic vibrations of the steam turbine working stage have been studied with allowance for mistuning. An approach
to the determination of the mathematical expectation and spectral density of the displacements of the system under study is
proposed, which is based on the model of a single sector.
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Translated from Problemy Prochnosti, No. 5, pp. 105–113, September–October, 2008. 相似文献
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不同负荷状态下的柴油机振动、温度、转速等信号显著不同,而机组故障信号特征往往淹没在随负荷变化而剧烈变化的信号中,因此变负荷状态下的柴油机故障监测诊断难度较大,一直困扰着柴油机的实际故障诊断工作。本文提出了一种基于流形学习和KNN算法的柴油机工况识别方法,为柴油机变负荷工况下故障监测预警打下基础。方法融合机组的多源信号特征构建特征向量,通过流形学习t-分布邻域嵌入算法(t-SNE)实现特征向量的维数约简和敏感特征提取,采用K最近邻分类算法(KNN)完成柴油机运行负荷状态的自动分类。正常及故障状态下的柴油机信号验证了方法的有效性和实用性。 相似文献
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舰船推进轴系的抗冲击性能是舰船生命力的主要影响因素之一。为了分析推进轴系在转动状态下的抗冲击性能,将其视为一个低速的转子系统,采用有限元法建立推进轴系受横向冲击载荷的计算模型,并用Newmark法对模型进行数值求解。通过实例仿真计算,研究推进轴系冲击响应特征及转速的影响。计算结果表明,转轴的回转效应使其在垂直和水平方向的弯曲振动相互耦合,其影响等效为阻尼效应,与静态轴系冲击响应相比,当系统阻尼较小时,转速对大转动惯量部件附近位置的响应影响较大,不可忽略;但当系统阻尼较大时,转速的影响较小。轴系的最大冲击位移出现在距离较远的相邻两轴承间的轴中部;轴的弯曲变形能有效地吸收冲击能量,故螺旋桨的冲击加速度响应不大。 相似文献
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Turbine blades are the most critical components in any power plant. Failure in even one rogue blade out of hundreds of blades fixed on the rotor leads to colossal damage to the machine. Statistics have shown that low-pressure turbine blades in steam power plants are generally more susceptible to failure compared to high- or intermediate-pressure blades. The mechanism of failures is different in each case and is generally very complex. As a result, a large number of blade failures are not fully understood. Two primary forces acting on the blades are the steady centrifugal force due to rotation and the fluctuating steam bending force. In view of no direct access to monitor the health of the blades through vibration or other means, indirect method using non-contacting probes have been attempted and some are in use in special cases. Largely these methods are expensive and intrusive in nature. They involve placing of sensors in the narrow space inside the turbine casing, routing special signal cables with sealing arrangement and involves difficulties in analyzing shot duration signals from each rotating blades. Unless a diagnostic technique is made simple to implement and whose reliability is proven, power plants will not find it attractive to invest on upgrade for safe operation of the machine. This article is about an innovative method of detecting the presence of blade vibration in operating turbine through vibration signal analysis and prevention through process control. The method is based on vibration analysis of the turbine casing. The casing vibration includes signals associated with the blades of different stages called as blade passing frequency (BPF). When the rotating blades vibrate, the analysis of changes in the BPF is a novel way of diagnosing blade vibrations. Signals captured from operating plants have been analyzed and blade vibrations have been detected and verified with Campbell diagram. Laboratory experiments were carried out on a rotating fan to demonstrate robustness of the diagnostics tool for turbine blades. 相似文献
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对于高速电机机组而言,在设计阶段准确预测转子动态特性,尽量减小发生故障的可能性是至关重要的。该文用有限元分析及实验方法计算由柔性联轴器耦合的多跨转子轴系临界转速及振动模态,用有限元软件的弹簧单元模拟弹性联轴器的轴向、径向及扭转刚度,分析联轴器刚度、结构参数对轴系临界转速的影响。研究表明:轴系临界转速及振动模态不同于单转子,可以通过改变膜片的刚度、结构参数等来调整系统某些阶次的临界转速,使转子具有良好的动态特性。 相似文献
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纵、扭振动固有频率简并是提高纵-扭复合型超声马达输出力矩的关键问题。然而同一弹性体内的纵振固有频率远高于扭振固有频率.目前对两种振动固有频率的简并缺乏深入的理论研究。纵一扭复合型超声马达振动分析模型都基于一维理论。在此提出了一种纵、扭振动固有频率简并的新方法。通过将纵一扭复合型超声马达设计成双定子对称结构.在定子上附加一个调整环改变定子的力学边界条件。实现纵、扭振动同频共振。应用Hamilton原理建立了考虑泊松效应的定子纵、扭振动理论模型,分析了定子的纵振与扭振第一阶固有频率随调整环质量和位置的变化规律,通过优化马达的几何结构参数获得了纵振与扭振的同频谐振点。 相似文献
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Masahiko Yagi Akira Kitamura Nobutaka Shimizu Yoshinori Yasuta Minoru Kubota 《Journal of Low Temperature Physics》2011,162(5-6):754-761
We describe a highly stable, rotating cryostat designed for torsional oscillator experiments under DC rotation, where vortex lines penetration has been studied for 3D superfluids made of monolayer He films as well as for the supersolid state in hcp solid 4He. Especially, torsional oscillator experiments on hcp solid 4He are known to be quite sensitive to small vibrations or linear velocities on the order of 10 ??m/s or less. Thus, vibrations of the apparatus may destroy the measurements if they are not smaller than or equal to those of the building or the ground itself. The torsional oscillator performance described here often gives better data under steady rotation at moderate speeds than under stationary conditions. The article describes briefly a design idea shared by the two rotating cryostats at ISSP, the University of Tokyo, and discusses the torsional oscillator (TO) experiments under DC rotation. This is truly a high speed rotating cryostat with maximum rotational speed of at least 6 revolutions per second for TO experiments. It gives also much higher stability at reasonably low rotational speed because of the well-planned structure of the double frame construction with a lot of mass for the upper drive frame for rotation and the almost mechanically isolated, except for the drive mode motion, rotating cryostat with much higher stability of the inner frame for the cryostat mount. Phenomena of quantized vortex lines penetration through a macroscopic superfluid give unique information about the superfluidity itself. A method for detection of vortex lines penetration events using TO technology is also briefly reviewed. 相似文献
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国内的低速柴油机制造厂 ,船舶设计部门、造船厂和船东好象已经有一种共识 :艉机舱推进轴系使用低速五缸柴油机作主机时 ,都要用扭振减振器。但是 ,只要在设计时合理选用柴油机转速 ,并采用高强度低合金钢来制造中间轴 ,这类轴系大部分是不需要扭振减振器的。 相似文献
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The system of differential equations of a turbogenerator describing the electromechanical processes in a synchronous generator
and in four stages of a turbine is considered. Equations are obtained which describe the small torsional vibrations of the
different stages of the turbogenerator when a sinusoidal test voltage is applied to the field winding of the generator. The
values of the chronometric response for the stages of the turbogenerator are calculated.
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Translated from Izmeritel'naya Tekhnika, No. 10, pp. 48–50, October, 2005. 相似文献
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High vibrations in admission piping of a steam turbine were analyzed. Vibration failure was detected after piping modification as part of upgrading a 300 MW power turbine plant searching for 10% power increment. However, after 1 year operation a vibration malfunction was detected in control valve and fittings of income piping with risk of cracking for maximum output. A study of computational fluid dynamics (CFD) revealed large steam flow instabilities produced by recirculation and high velocity exceeding a critical point. Measurements of natural frequency piping system with the turbine stall and subsequent measurements of frequency and vibration analysis during turbine operation indicated that recirculating flow plays a main role in the vibration problem by resonance. The paper discusses CFD results obtained with a proposed pipe configuration that reduces turbulence effects. Combined pressure slide and diameter increment in piping lead to reduced vibration turbine operation. 相似文献
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Kang MK Huang R Knowles T 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(2):349-359
This paper presents a theoretical study of torsional vibrations in isotropic elastic plates. The exact solutions for torsional vibrations in circular and annular plates are first reviewed. Then, an approximate method is developed to analyze torsional vibrations of circular plates with thickness steps. The method is based on an approximate plate theory for torsional vibrations derived from the variational principle following Mindlin's series expansion method. Approximate solutions for the zeroth- and first-order torsional modes in the circular plate with one thickness step are presented. It is found that, within a narrow frequency range, the first-order torsional modes can be trapped in the inner region where the thickness exceeds that of the outer region. The mode shapes clearly show that both the displacement and the stress amplitudes decay exponentially away from the thickness step. The existence and the number of the trapped first-order torsional modes in a circular mesa on an infinite plate are determined as functions of the normalized geometric parameters, which may serve as a guide for designing distributed torsional-mode resonators for sensing applications. Comparisons between the theoretical predictions and experimental measurements show close agreements in the resonance frequencies of trapped torsional modes. 相似文献
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近年来虽然使用了某些电子式测振仪,但由于盖格尔测振仪非常适合于低频范围的振动位移测量,因而仍应用于测试和记录中低速发动机轴系的扭转振动。众所周知,盖格尔扭振仪划笔在纸带上的划迹对于分析来说显得小些,因此试验结果必须进行放大,和用手工或其他设备分解成简谐分量。这一工作是困难而费力的。为了把记录笔的运动转换成易于处理的电信号,在盖格尔扭振仪的传动杆端部粘接一个薄金属园板,并在其旁边安置一个电涡流传感器。电信号可以经过导线传送到振动测量设备示波器和微处理机,后者将发动机轴系的振动信号进行采样和以 FFT 算法将信号分解成简谐分量。文中介绍了使用一个既能产生电信号又能同时在纸带上画出波形的盖格尔扭振仪对一个柴油机推进装置进行扭转振动测量的试验结果。 相似文献
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V. R. Pesochin 《High Temperature》2001,39(3):470-473
A theoretical investigation is performed of the acoustic instability under conditions of volume condensation in a steam–gas mixture. The steam–gas mixture is assumed to be stationary and consist of a gas and moist steam. It is assumed that gas and steam are ideal gases and that the condensation process is nonequilibrium. Condensate droplets are assumed to be spherical and monodisperse, and their volume concentration is assumed to be minor compared to unity. It is demonstrated that acoustic vibrations are excited during volume condensation of steam. Formulas are derived for the calculation of the increment and frequency of vibrations. 相似文献