300MW机组汽轮机弯曲转子的振动控制

作者简介:　袁立平(1956),男,工程师,就职于河南电力试验研究所。

300MW 机组汽轮机弯曲转子的振动控制袁立平,罗剑斌,李　力,谭士森(河南电力试验研究所,河南郑州　450052)[摘　要]　针对某国产300MW 机组汽轮机高压转子弯曲故障,进行了转子振动响应和不平衡量计算分析。

采用单转子高速动平衡校正与更换可倾瓦轴承等措施,使轴振动幅值降低至合格范围。

[关键词]　300MW 机组;汽轮机;转子;弯轴;动平衡,轴振动[中图分类号]T K26316 [文献标识码]A [文章编号]10023364(2003)03006402 一台型号为N300-16.6/537/537高中压合缸、单轴双排汽的凝汽式汽轮机组,在冷态启动时持续出现高压转子轴振动幅值超过报警值现象,并在前轴承箱听到明显异音。

揭缸检查发现高中压转子大轴有磨擦痕迹,测量转子圆周晃动值最大0.27mm ,确认在转轴中部产生永久弯曲0.13mm ,必须进行技术处理。

1　弯轴特点与不平衡量分析该转子轴为高压与中压合成结构的整体锻件轴。

高压部分有10级动叶片,中压部分有6级动叶片,转子总长度7351mm ,两支承跨度5961mm ,转子总重量21t 。

转轴本体最小直径d 630mm 。

在转子中部,是高压与中压之间的“城墙式”汽封,简称“过桥汽封”。

在此部位,测得圆周晃动最大值为0.27mm ,见图1。

按照设计制造标准,转轴圆周晃动量应小于0.05mm 。

沿转子轴向长度排放8个百分表,按轴径圆周12等分测量结果,该转轴呈“弓型”弯曲,测量值为0.13mm 。

弯曲的凸点部位对应联轴器螺孔(12个)9点位置,而转轴磨擦痕迹线恰在12～7点之间,表明该转子弯曲属永久弯曲,为动静碰摩受热应力影响所致。

由于转轴的变形弯曲,加剧了转子质量重心与回图1　国产300MW 高中压汽轮机转子弯曲示意转中心的偏移程度,产生了附加的不平衡量。

依据转子结构、重量和几何尺寸的计算分析,若单纯弥补“过桥汽封”段弯曲的不平衡量,在相邻的P 1和P 11级叶轮校正平面配重至少在1000g 以上[3]。

2　弯轴的振动响应与现场平衡该机组配有德国菲力浦公司RMS -700型轴系振动监测装置,可对1～6号轴承振动和对应1、2、6号轴承的转子轴振动进行连续监测。

当汽轮机高压转子轴技术交流　θψ　热力发电・2003(3)振动(对应1号轴承附近)出现频繁报警信号时,首先检查测量系统元件的可靠性。

如在203MW负荷工况:1号X测点处V dc=-10.25V,V ac=580mV, A p-p=230μm;1号Y测点处V dc=-9.36V,V ac= 196mV,A p-p=80μm。

文中V dc为测量轴振动的涡流传感器的间隙电压值,正常范围(-8～-12)V之间;V ac为测量轴振动信号波形幅值的交流电压值;A p-p为测量轴振动位移的峰-峰值。

为便于分析诊断振动特性,使用美国B1N公司P208采集系统进行信号分析。

高压转子的设计临界转速是1680r/min。

在连续3次冷态启动过程中,当机组在1200r/min中速暖机后升速时,1号轴振动基本维持在200μm以上,临界转速时最大可达350μm(降速过程),额定转速空载时可达300μm,并网后可降至220μm。

振动频率主要是机器转速频率的同步响应。

依据ISO7919标准关于转子轴振动测量与评价准则和挠性转子的不平衡响应分析,做了如下工程试验。

对弯曲度2.2×10-5的挠性转子进行配重补偿校正,在转子P1级叶轮加重237g,P11级叶轮加重195 g,合计在高中压转子中部同相加重432g,以降低高中压转子的动挠度与轴承动力载荷。

试验表明,在临界转速时高压转子轴振动有所降低。

在定速3000r/min时,随机组负荷增加,轴振动幅值由240μm减小到150μm。

经301天连续运行,转子动平衡减振效果明显。

3　单转子高速动平衡2000年11月在该机组第二次大修期间,确定对汽轮机弯曲转子在高速动平衡机上进行精密平衡校正。

应用德国西门子公司HOESCH MFD23.2M卧式车床校核转子中心,测量汽轮机高中压转子中部过桥汽封轴段晃度值为0.27mm,即转子弯曲值为0.135mm,弯曲凸点仍对应联轴器螺孔9点位置,与原始弯曲一致。

按照制造厂建议,对过桥汽封轴段进行外圆车削,保留残余最大晃动值0.11mm,观测到机床车削进刀痕迹只有圆周的3/5,对应弯曲凹点部位没有触及。

应用德国辛克公司DH8/D50型转子高速动平衡机进行平衡校正,参照现场平衡的振动响应值计算分析,转子中部校正补偿尚需2000g配重。

经过十余次试验校正,在该转子原配重基础上,对4个平面进行了校正配重(表1),即在转子中部P1与P11平面又同相等效加重2303g(采用矢量合成计算),在转子两侧加一力偶250g×2的配重。

转子重新配重后动平衡机试验结果:(1)在3000r/min时,高中低转子轴承振动速度有效值V rms:1号轴承1.28mm/s,2号轴承0.85 mm/s。

(2)在3000r/min时,高中压转子轴振动幅值A p-p:1号轴承小于80μm,2号轴承小于40μm。

(3)实测转子一阶临界转速1680r/min时,1号轴承最大振动0.62mm/s。

表1　高中压转子高速动平衡前后配重分布状态项目P1P10P11P16平行槽半径/mm360360460380原有重量/g2372401951053对应螺孔编号311310～11现有重量①/g987240250695250对应螺孔编号3～41153～411①现有重量=原有重量+现增配重4　轴承改进与运行考核为了有效抑制转子振动与提高轴承运行可靠性,进行了如下技术改进:(1)将高压转子的1号轴承由圆筒瓦更换为五瓦块可倾瓦;(2)把转子联轴器对轮螺栓直径由d48mm增大至d54mm;(3)前轴承箱的主油泵小轴更换为抗震轴;(4)转子的标高与扬度曲线按制造安装标准与检修测量情况进行合理调整;(5)清理汽轮机座滑销系统;(6)加装轴振动传感器和完善状态监测系统。

机组大修后冷态启动,在临界转速1680r/min 时,高中压转子振动A p-p值均小于80μm,轴承振动值小于30μm;在额定转速3000r/min时,1号轴振动最大值99μm,并网后轴振动值随负荷功率增加而减小(表2)。

表2　高中压汽轮机振动值μm 项目3000r/min空载165MW工况240MW300MW1号轴承振动8～1064～541号轴承轴振动80～997264～5021～332号轴承振动6～86532号轴承轴振动56～66423719～47(下转第68页)技术交流热力发电・2003(3)θζ　用2h即可完成。

(2)由于REXA执行器的模块化结构,自带封闭油源,无须外供控制油源,克服了常规电液转换器易受油质污染影响的缺陷。

(3)由于具有大力矩输出,可直接驱动油动机错油门,提高了油动机错油门的跟踪力、抗油质污染能力以及工作的可靠性。

(4)当DEH控制器故障或控制系统失电时, REXA执行器具有自动保位功能,保持阀位和负荷不变。

在异常工况或必要的情况下,还可手动操作REXA执行器机械手轮,直接控制阀门开度。

(5)可实现汽轮机电液调节系统的所有功能,由于采用电液并存联合调节,运行方式灵活,提高了机组运行的可靠性。

3　实际应用2000年9月,北票发电厂3号机组集成型执行器电液调节系统投入运行,一次起动成功,已连续运行15个月。

经过升速、并网、带负荷、甩负荷及超速试验,其性能指标均满足设计要求,能适应机组各种运行工况的需要,安全可靠,达到了预期效果。

2000年10月,进行了凝汽工况甩负荷试验,甩50%额定负荷,瞬时最高转速为3070r/min,稳定转速为3000r/min;甩100%额定负荷,瞬时最高转速为3155r/min,稳定转速为3000r/min;超调量为5.17%。

2001年4月,对系统功能和性能指标进行了综合测试,转速控制精度为±1r/min,负荷控制精度小于±0.1MW。

实际应用表明,集成型执行器电液调节系统可消除机组滑负荷、加减负荷困难、调节系统迟缓大等缺陷,改善了调节系统控制品质及甩负荷性能,提高了机组的安全性、稳定性、自动化水平及调峰能力,提高了运行管理水平,减轻了运行人员的劳动强度,并能严格控制上网电量,具有明显的经济效益。

4　结　论(1)以REXA电液执行器作为汽轮机电液调节系统的电液转换装置,克服了目前电液转换器、电液伺服阀等普遍存在的抗油质污染能力差、泄漏和卡涩等问题,并以其独特的功能提高了系统运行的可靠性、灵活性,能满足汽轮机调节系统控制精度的要求。

(2)集成型执行器作为转换装置,可实现电液并存和纯电液调节能实现汽轮机电液调节系统所应具有的各种功能。

而电液并存联合调节方式,运行灵活、可靠性高、改造工作量小,应用前景广泛,是中小型机组调节系统改造的新途径。

(3)将REXA执行器置于油动机错油门上部,直接驱动错油门的控制方式,是无控制油源调节系统应用研究的尝试,其应用的成功,对汽轮机调节系统的发展起到了积极作用。

(上接第65页)显而易见,由于进行了单转子高速动平衡与相关技术改进,汽轮机弯曲转子轴振动状态达到机组投运历史的最佳水平,使振动值处于合格范围。

5　结　论汽轮机受转子结构与运行条件影响,极易产生动静碰摩导致大轴的变形弯曲。

在难以采用直轴校正的情况下,应用动平衡工艺可以减小或降低转子的振动幅值,其基本要求如下:(1)转轴弯曲值不大于0.15m m,并需测准弯曲变形的部位与凸点;(2)采用对应合理的转子动平衡校正平面与配重型式;(3)对汽轮机额定转速及升降速过程均应进行状态监测;(4)对轴承振动和转子轴振动幅值均要进行分析考核。

应用高速动平衡机进行精确校正,结合轴系安装条件的改进,可降低弯曲转轴的不平衡扰动响应,取得良好减振成效。

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T est shows that the anti-interference ability of the said measuring technique is strong,the accuracy of measurement can meet the requirements in engineering measurement.H ence,it is suitable for measuring the velocity of non-spherical and non-transparent particles.PRESENT SITUATION OF BE D-TEMPERATURE CONTR OLL ING FOR CFB B OI LERS AN D IMPR OVING MEASURES THERE OF ………………………………………………………………………………………………………………………WU Shu-zhi et al(51) An investigation and study on the present situ ation of bed-temperature controlling for CFB boilers have been performed.It is pointed out that the existing controlling mode has too sm all adjustable amplitude,can’t effectively regulating the bed-temperature of CFB boilers.Throu gh study and analysis,a recommend ation of establishing a tw o-input and tw o-output multi-variable controlling system has been put forw ard,then,while the deviation of bed-temperature is comparatively sm all,only the m atch ratio of prim ary and second ary air is adjusted;while the said deviation is com paratively large,the coal-feeding amount and air qu antity can simultaneously be adjusted.…………APPL ICATION OF FOUR CORNER OPPOSE D TANGENTIA L FIRING ON UTI L IT Y B OI LERS HE Zhi-qiang et al(53) Four corner opposed f iring,as a new arrangement pattern for tangential f iring,has been successfully used on boilers with various capacity level and different coal sorts.Pratice shows,the said f iring pattern has obvious effectiveness for solving problems often occurred in boilers,such as deviation of flue gas temperature,slagging in the furnace,high temperature corrosion,as w ell as in as pect of reducing N Ox emission.…………………………OPTIMIZTION OF RETR OFITTNG SCHEME FOR THE COMBUSTIN SYSTEM XIU Xing-jing et al(57) A system atic analysis and evalu ation of slagging problems occurred on boilers in Yunfu Pow er Plant,G u an gdong Province,has been carried out.B ased on the principle of em2 phatically solving the slagging problems and simultaneously taking account of stabilizing combustion,an optim al retrof itting scheme is suggested,including the blunt body of burners to be set upright,the middle-and low er-level second ary air to be concentratically conf igured,the burning cavity with blunt body to be used for the low er-level prim a2 ry air,as w ell as m aking the left and right side of pulverized coal and air mixture flow to be rich and lean res pectively etc.,It is expected that the desired results of retrof itting can be achieved.’APPL ICATION OF FUE L G AS EX CITING WAVE OPERATE D SH OOT B LOWERS ON AIR PREHEATER OF A670t/h B OI LER …………………………………………………………………………………………………………………Li Wen-yu an et al(60) Analysis of ash clogging phenomenon on air preheater of Datong Pow er Plant N o.2under the State Pow er Corp has been carried out.It is considered that the eff icienc y of origi2 nally designed steam operated shoot blow ers w as influenced u pon by several factors,such as non-suitable position of installing,increasing humidity of steam at the f inal end,as w ell as non-reasonabe design of nozzle and stroke concerning the steam operated shoot blow ers etc.For these reasons,it is tried to install fuelgas impulse exciting w ave operated shoot blow ers for replacing some steam operated shoot blow ers.After putting the new type shoot blow ers into operation,the resistance on both air and gas sides of the air pre2 heater has been obviously low ered,the effectiveness of shoot blowing being excellent.CAUSE ANA LYSIS OF OVER-TEMPERATURE OCCURRE D ON STEAM TURBINE’S BEARING SH OE AN D IT’S TREATMENT ……………………………………………………………………………………………………………………L I Shou-lun et al(62) Several typical phenomina of bearing shoe’s over-temperature trouble have been analyzed.Through appropriate treatment,allowing the temperature of said bearing shoe to re2 turn to norm al.………………BEN DING R OT OR’S VIBRATION CONTR OL OF STEAM TURBINE FOR A300MW UNIT YUAN Li-ping et al(64) I n view of the high-pressure rotor’s bending fault occurred on steam turbine of a home-m ade300MW unit,the rotor’s vibration response and the unb alanced com ponent have been calculated and analyzed.Some measures,such as single rotor high-speed dynamic equilibrum,correction and inclinable bearing shoe’s application,have been taken,en2 abling the vibration amplitude to reduce to a region up to stand ard.APPL ICATION OF E LECTR O-H YDRAU L IC G OVERNING SYSTEM WITH INTEGRATE D ACTUAT OR ON UNIT N O.3AT BEIP2………………………………………………………………………………………………IAO POWER PLANT MA R en-ku et al(66) A study on application of integrated actu ator in electro-hydraulic governing system which is a governing system without control-oil source of steam turbines has been presented. The successful application of the said control mode,in which the stagger oil valve is directly driven by the said actu ator,at B eipiao Therm al Pow er Plant resolved com pletely the problem of infuencing the electro-hydraulic device due to fluid medium pollution,and enhanced successfully the reliability of unit’s operation,at the same time,provided new w ay and means for retrof itting electro-hydraulic governing system of medium and sm all units,having positive effect to developing steam turbine governing system without control -oil source and without fluid w orking medium.DEVE LOPMENT OF A DATA ACQUISITION AN D WARNING SYSTEM G OVERNING META LL IC WA LL TEMPERATURE IN …………………………………………………………………………………………………………B OI LERS ZHU Zhi-gang et al(69) T aking the d ata acqisition and w arning system governing metallic w all temperature in boilers at H u aneng N antong Pow er Plant as example,the realization of d ata acquisition,su2 pervision,off-limit w arning,and statistic m anagement system governing metallic w all temperature in boilers by using intelligently advanced technology and netw ork communica2 tion technology has been presented.The said system has good universality,having bright future for popularization.UPDATING AN D RETR OFITTING THE EX CITATION REGU LATING DEVICE OF A60MW GENERAT OR L I Jian(72)………………The status of retrof itting excitation system for a60MW generator in Magang Therm al Pow er Plant has been presented.It features the ori ginal m ain circuit of excitation hasn’t been changed,i.e.the fund amental perform ance and property of original system are still reserved,only the regulating device is upd ated and retrof itted,and better economic as2 pect obtained.The regulating device used for retrof itting is a32-bit numeric signal processor,the regulation speed,capability for counter-interference,and reliability of the excitation system having been enhanced b y using DSP technology.∫Originated from:1972∫Authorized by:China State Pow er Corp∫Sponsored by:Thermal Pow er R esearch Institute under China State Pow er CorpChinese Society for Electrical E ngineering∫Edited and Published by:Magazine Agency of Thermal Pow er G eneration∫Distributed by:Distribution Bureau of N e ws2papers And Periodicals under Shaanxi Provincial Off ice of Postal Service。