苏制215MW机组碰摩振动的分析处理

以漳泽发电分公司5号汽轮机在运行中2号轴承发生间断性振动波动现象为例,经测试分析诊断为汽轮机2号轴承油挡碰摩所致,检修中发现油挡内环融化导致碳化物积聚,经更换油挡处理后机组振动正常。     

汽轮机高中压转子浮动油挡摩擦振动分析

介绍两台机组运行中高中压转子出现轴系振动波动现象,诊断该振动故障的根源是高中压转子与浮动油挡发生摩擦振动引起了转子产生热弯曲。总结了浮动油挡与转子摩擦振动的特点与机理,并从运行和检修两方面提出该故障的控制对策和解决方法。     

汽轮机油挡积碳问题的分析与处理

针对某电厂1号机组汽轮机轴系异常振动现象,对其产生原因进行分析,确定为#2轴瓦油挡积碳引起。通过分析油挡积碳的形成过程,并结合电厂实际条件对积碳问题进行了处理;同时,深入探讨了应对油挡积碳问题的几项具体措施,可为出现类似问题的机组提供分析和解决问题的思路。     

汽轮机油挡渗漏油的原因及防范措施

在火电厂中,为了防止汽轮机轴承室内的润滑油向外渗漏,保持动静部分的严密性,现在一般均采用油挡密封。油挡是由内外两组油封齿和回油槽组成,每组油挡齿有2～4道铜板条或铝板条镶嵌在油挡体上,其作用是阻止轴承室内的润滑油外漏和外界蒸汽进入。该油挡用装配槽或螺丝固定的方式安装在轴承室的轴向两端,这种密封技术被广泛应用于在役机组。 目前,尽管每次大小修都严格按照《汽轮机检修工艺和质量标准》要求把油挡间隙调整到规定范围(左右侧:0.15～0.2 mm;下部:0.05～0.10 mm;上部:0.20～0.25 mm)。但机组运行一段时间后,油挡还会出现渗漏…     

1000 MW核电汽轮机轴承甩油原因分析及优化

某核电厂汽轮机在运行过程中出现轴承甩油至保温棉,并在高温作用下引发火险。通过对润滑油系统和轴承箱内部结构进行阐述,对汽机轴承甩油从装配、润滑油回油、挡油板设计等方面进行了分析,并采取挡油板优化改进方式从根本上解决了甩油问题,提高了机组运行安全性和可靠性。     

某330 MW汽轮机高中压转子间断性振动诊断处理

某330 MW机组汽轮机高中压转子出现间断性振动,轴振最大达130～141μm,超过振动保护值.分析认为,本次振动波动的因为是该机组2号、3号瓦油挡处油泥堆积碳化导致动静碰摩.在小修过程中检查清理油挡并改善高、中压汽缸端部保温后,机组振动恢复正常.     

某660 MW汽轮机振动异常分析及处理

某660 MW超临界一次中间再热反动式汽轮机机组在正常运行中多次发生轴承振动异常升高的现象,该振动与运行参数无明显关联,以间歇性的工频振动为主。为保证机组安全稳定运行,通过分析轴承TDM图及振动频谱图,并结合维修检查情况,确定为高压缸#1、#2号轴承油挡积碳造成。经过改变运行策略,并从抑制杂质的吸入和降低油挡温度两方面对油挡实施技术改造,轴承振动异常升高现象得到解决。电厂应建立振动数据台账,为快速分析处理振动故障提供保障。     

零重力油挡在125MW机组上的应用

以前投产的各类型号机组 ,其轴承箱润滑油的密封油挡均采用固定式有间隙的铜齿油挡 ,这种油挡经过长期运行后 ,间隙越来越大 ,无法起到完全密封的效果 ,由此经常发生沿主轴甩油或漏油现象。金竹山电厂 4台 12 5MW机组和 2台 5 0MW机组也采用这种油挡 ,近年来偶尔发生因油挡沿轴甩油而造成高温区积油冒油烟甚至发生明火现象 ,成为生产的一个潜在的安全隐患。为消除此缺陷 ,大修中在 6号机组 ( 12 5MW机组 )安装了新型的磁力完全密封零重力油挡。从运行情况来看 ,这种新型油挡的密封效果较佳 ,但也存在一些不足之处。1　固定式铜齿油挡与零…     

石嘴山发电厂^#8机振动故障诊断及处理

石嘴山发电厂^#8机大修后启动试运，并网带负荷后，^#3瓦振动逐渐增大最高升至82μm。经多次试验分析及本着先易后难的原则，对影响发电机转子振动的不平衡因素逐一加以消除。解决了振动超标问题。尤其对解决国内大小机组上广泛采用浮动油挡和接触式油挡所引发的振动问题提供了较好的解决方法。     

330MW机组轴振周期性波动分析处理

某电厂1号机组5号瓦轴振呈周期性波动并有逐渐发散的趋势,该异常情况严重影响机组的安全运行.通过对汽轮机振动在线监测系统记录的振动倍频及DCS系统中的振动历史曲线图进行分析,判断其主要是由汽轮机转子局部发生轻微摩擦导致.在机组停运后对相应位置进行了翻瓦检查,确认密封瓦、挡油环与大轴碰磨导致5号瓦轴振偏大.通过采取对应的检修措施,使设备恢复正常.     

1025t/h锅炉烟处理灰水系统防结垢处理

针对田家庵电厂 5号机输送灰渣管道严重结垢 ,回水系统管道结垢的问题 ,投用炉烟处理灰水系统的同时 ,在漂珠池溢流管口加入阻垢剂。对炉烟处理灰水系统进行测试 ,对结垢原因、运行参数分别进行了评价 ,并提出了建议。     

Numerical simulation of small silicon partially insulated MOSFETs

The scaling of conventional MOS bulk transistors with gate lengths below 100 nm seems to be difficult due to short channel effects. Especially the adjustment of the threshold voltage V _th is difficult because of the rapid drop down at shorter gate lengths. For low power consumption and high speed applications SOI technologies have been developed, but floating body effects, increasing leakage currents, kink phenomena and decreased heat dissipation occur in SOI-FETs. To combine the benefits of conventional and SOI-MOSFETs and to avoid the disadvantages, partially insulated FETs (Pi-FETs) with oxide regions under source and drain are candidates for scaling down the gate length into the deep submicron area [1–3, 5, 6]. We present the results of several numerical simulations to compare conventional bulk transistors, SOI-FETs and Pi-FETs in their static and dynamic behaviour.     

Effect of Charge Injection Due to ESD on the Operation of MEMS

The relative effect of charge injection due to human-body model electrostatic discharge (ESD) on the operation of capacitive microelectromechanical systems (MEMS) structures is studied. The influence on the operating characteristics as a function of feature size is analyzed; for small gaps (< 5 mum), the modified Paschen's law applies. A force factor is introduced to compare forces due to the control voltage and trapped charge due to ESD or triboelectrification and assess possible failure due to stiction. The results show that the relative effect of injected charge due to ESD increases inversely as the square of the gap separation for floating targets and inversely as the square of the plate area for grounded targets. For comparison purposes, the relative effect of charge injection due to triboelectrification is shown to be independent of device scaling. An electric-field model for the air gap and dielectric layer is introduced to assess the reliability of MEMS due to trapped charge in the dielectric.     

传统示波器在浮地测量中的应用限制及解决方案

车载、机载、箭载等电子装备最多采用的是浮地接法,虽然浮地接法有很多优点.但在设备的生产测试中示波器的使用存在一些问题,传统示波器的地与工频电源共地,用该示波器测试浮地设备时,有可能对电子设备造成损伤.分别采用传统示波器与浮地示波器测试某箭载浮地接法的模数转换电路的锯齿波.实验证明:传统接地示波器有可能造成CMOS电路的...     

应用于CVT在线校验的LVQB型电流互感器的悬浮电位暂态特性分析

将LVQB型电流互感器改造成标准电容器对CVT校验是一种新在线校验方法。该校验方法通过隔离开关的转换投切实现。在转换投切过程中,有可能出现隔离开关互锁,进而产生过高的悬浮电位,从而破坏了隔离开关绝缘,最终导致校验失败。为此,文章重点研究了悬浮电位产生机理及其暂态特性。在考虑改造方法和电流互感器工作方式的基础上,建立了两种不同的产生悬浮电位的等效电路。在分析等效电路的动态响应后,采用拉氏变换分析悬浮电位的暂态过程。根据拉氏变换分析结果,采用Matlab对其暂态过程进行了仿真计算,分析了影响悬浮电位因素。仿真结果表明:尽管悬浮电位的暂态过程十分短暂(不到0.03 ms),但其产生的高幅值过电压(604.9 kV)仍有可能将隔离开关击穿,可通过控制投切角将悬浮电位控制在安全范围内,因此校验时一定要注重对隔离开关投切角的控制。     

Design of low power approximate floating‐point adders

Due to the increasing demands for more power in data intensive computing, low power design methodologies play a very important role in these systems. For noncritical data, the approximate computing that significantly reduces the power can be used. In this paper, an approximate floating‐point adder is proposed by designing an inexact mantissa adder and exponent subtractor. The results indicate that the power consumption and delay of the proposed approximate floating‐point adder have been decreased by 37% and 62% compared with the IEEE‐754 single‐precision floating‐point (FP) adder. Furthermore, compared with a state‐of‐the‐art inexact floating‐point adder, the proposed method provides an improvement of 7% and 21% in terms of the power consumption and delay. In addition, the proposed floating‐point adder has been investigated in terms of error, and the mean error of the proposed floating‐point adder at worst is about 55% less than that of another approximate floating‐point adder considered in this work. High dynamic range (HDR) images are processed using the proposed approximate floating‐point adders to show the performance of the proposed adder. The results show that, on average, peak signal‐to‐noise ratio increased by 9.6 and 18.64 dB, which may be achieved by utilizing the proposed floating‐point adder.     

漂浮特性对风力发电机塔基载荷性能的影响

为研究漂浮特性对风力发电机塔基载荷性能的影响,使用仿真技术进行分析.将漂浮平台和波浪载荷考虑到已建好的风力发电机组模型中,形成漂浮式风力发电机组分析模型.以NREL 5 MW数据为基础,利用FAST软件对漂浮式和基础固定式风电机组涉及的各典型工况进行载荷性能仿真,并将2种风电机组的仿真结果进行对比.研究结果表明：漂浮特性对风电机组塔基载荷的波动及极限载荷的影响显著,通过对比2种风电机组各典型工况下的仿真结果,得出漂浮式风电机组塔基极限载荷相比基础固定式机组结果呈现规律分布,并对规律分布的原因作出了分析.     

海上风电机组格构式浮式基础结构优化及响应分析

面对日益严峻的环境问题,优化浮式基础结构形式成为海上风电降本增效的一大途径.对一种具有双重抗摇摆机制的新型格构式浮式基础进行结构优化,通过格构式塔架不同布置形式的参数化分析,寻找最适合格构式浮式基础的系杆布置形式,同时对优化后格构式浮式基础进行水动力响应分析,验证优化方案可行性.结果表明:在格构式系杆布置方面,斜向系杆...     

On the systematic synthesis of CCII‐based floating simulators

This paper is adopting a new approach in the systematic synthesis of CCII‐based floating simulators. The synthesis procedure is based on the generalized systematic synthesis framework for active circuits using admittance matrix expansion. The resulting derived floating simulators include circuits that have been reported earlier in the literature in addition to novel floating simulators using various types of CCII. The synthesized floating simulators can be used to realize floating coils, FDNRs, and resistance and capacitance multipliers; according to the types of passive elements employed in the design. The potentials and drawbacks of every one of the synthesized circuits vary according to the design tradeoffs including complexity, number of active devices, number and values of grounded and floating passive elements, matching requirements, and tunability. SPICE simulations are presented to verify the performance of the new circuits obtained by systematic synthesis and hence demonstrate the potentials of the generalized synthesis framework in producing novel circuits with high performance. Copyright © 2009 John Wiley & Sons, Ltd.     

Resistorless floating immittance function simulators employing current controlled conveyors and a grounded capacitor

In this paper, new floating immittance function simulators employing second-generation current controlled conveyors are proposed. The first four of the presented circuits employ only a single grounded capacitor as passive component and can realize either a negative or a positive floating inductor or capacitor. The last two of the proposed circuits do not employ passive components and can realize either negative or positive floating resistances. All of the proposed circuits do not require passive element matching. As an application, a third-order butterworth filter is realized using the proposed positive floating inductance simulator. SPICE simulation results and large signal behavior of the filter are included.