《过程控制技术》课件-调节阀的工作流量特性

Workingflowcharacteristicsofcontrolvalves调节阀的工作流量特性落版在此调节阀的工作流量特性Workingflowcharacteristicsofcontrolvalves谢聪XieCong主讲教师Teacher快开Quickopening直线Linear对数Logarithmic调节阀的流量特性Flowcharacteristicsofcontrolvalves调节阀的工作流量特性Workingflowcharacteristicsofcontrolvalves谢聪XieCong主讲教师Teacher不同阀芯形状所对应的流量与开度之间的关系Relationshipbetweenflowandopeningfordifferentvalveplugshapes快开Quickopening直线Linear对数Logarithmic相对行程(l/L)(%)Relativestroke(l/L)(%)相对流量(Q/Qmax)(%)Relativeflow(Q/Qmax)(%)调节阀的工作流量特性Workingflowcharacteristicsofcontrolvalves管道阻力Piperesistance前后压差Upstreamanddownstreampressuredifference工作流量特性Workingflowcharacteristics调节阀的工作流量特性Workingflowcharacteristicsofcontrolvalves某化工厂的反应釜温度控制系统，选用了具有线性流量特性的调节阀。Acontrolvalvewithlinearflowcharacteristicsisselectedinthereactorkettletemperaturecontrolsystemofachemicalplant.调节阀的工作流量特性Workingflowcharacteristicsofcontrolvalves实际投用Actualapplication开度在30%以下，温度波动非常大，很难控制；Whentheopeningisbelow30%,temperaturefluctuationsareverylargeanditisdifficulttocontrol;开度超过70%后，出现了调节过于迟缓的问题。Whentheopeningexceeds70%,thecontrolisoverlysluggish.Workingflowcharacteristicsofcontrolvalves调节阀的工作流量特性某化工厂的反应釜温度控制系统，选用了具有线性流量特性的调节阀。Acontrolvalvewithlinearflowcharacteristicsisselectedinthereactorkettletemperaturecontrolsystemofachemicalplant.实际投用Actualapplication开度在30%以下，温度波动非常大，很难控制；Whentheopeningisbelow30%,temperaturefluctuationsareverylargeanditisdifficulttocontrol;开度超过70%后，出现了调节过于迟缓的问题。Whentheopeningexceeds70%,thecontrolisoverlysluggish.Workingflowcharacteristicsofcontrolvalves调节阀的工作流量特性调节阀工作流量特性Workingflowcharacteristicsofcontrolvalves调节阀装在具有阻力的实际管道中，管道对流体的阻力随流量大小变化，阀前后（剩余）压（力）差也会发生变化，使调节阀固有流量特性发生畸变。Whenacontrolvalveisinstalledinapipelinewithresistance,thepipeline’sresistancetofluidchangeswiththeflow,causingtheupstreamanddownstream(residual)pressuredifferencetovary,whichdistortstheinherentflowcharacteristicsofthecontrolvalve.Workingflowcharacteristicsofcontrolvalvesinserieswithpipelines与管道串联时调节阀工作流量特性管道系统总压力ΔP等于管路系统的压降ΔPG与调节阀的压降ΔPT之和。ThetotalpressureΔPofthepipelinesystemequalsthesumofthepipelinesystem’spressuredropΔPGandthecontrolvalve’spressuredropΔPT.调节阀Controlvalve管路及设备管道PipelineandequipmentpipelinesΔPTΔPGΔPΔPΔPGΔPTPQWorkingflowcharacteristicsofcontrolvalvesinserieswithpipelines与管道串联时调节阀工作流量特性调节阀Controlvalve管路及设备管道PipelineandequipmentpipelinesΔPTΔPGΔPΔPΔPGΔPTPQ调节阀全关时，阀前后（剩余）压（力）差最大，基本等于系统总压力ΔP。Whenthecontrolvalveisfullyclosed,theupstreamanddownstream(residual)pressuredifferenceisatitsmaximum,essentiallyequalingtothetotalsystempressureΔP.从串联管道中调节阀两端压差ΔPT

的变化曲线可看出：ThevariationcurveofpressuredifferenceΔPTacrossthecontrolvalveinserieswithpipelinesshowsthat:调节阀全开时阀前后（剩余）压（力）差降至最小。Whenthecontrolvalveisfullyopen,theupstreamanddownstream(residual)pressuredifferencedropstoitsminimum.Workingflowcharacteristicsofcontrolvalvesinserieswithpipelines与管道串联时调节阀工作流量特性调节阀Controlvalve管路及设备管道PipelineandequipmentpipelinesΔPTΔPGΔPΔPΔPGΔPTPQ

Workingflowcharacteristicsofcontrolvalvesinserieswithpipelines与管道串联时调节阀工作流量特性

相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)Workingflowcharacteristicsofcontrolvalvesinserieswithpipelines与管道串联时调节阀工作流量特性理想直线特性的畸变Distortionofideallinearcharacteristics理想等百分比特性的畸变DistortionofidealequalpercentagecharacteristicsWorkingflowcharacteristicsofcontrolvalvesinserieswithpipelines与管道串联时调节阀工作流量特性相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)S值越接近1，说明阀前后压差变化越小，工作流量特性越接近固有特性；S值越小，压差变化越剧烈，特性畸变越严重。TheclosertheSvalueisto1,thesmallertheupstreamanddownstreampressuredifferencedeviationofthevalveandtheclosertheworkingflowcharacteristicistotheinherentcharacteristic;thesmallertheSvalue,themoredrasticthepressuredifferencedeviationandthemoreseverethecharacteristicdistortion.Workingflowcharacteristicsofcontrolvalvesinserieswithpipelines与管道串联时调节阀工作流量特性相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)串联管道会使调节阀的放大系数减小，调节能力降低，S值低于0.1时，调节能力基本丧失。Pipelinesinseriesreducetheamplificationcoefficientofcontrolvalvesanddiminishtheircontrolcapability.WhenSfallsbelow0.1,thecontrolcapabilityisessentiallylost.Workingflowcharacteristicsofcontrolvalvesinserieswithpipelines与管道串联时调节阀工作流量特性相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)结论ConclusionsWorkingflowcharacteristicsofcontrolvalves调节阀的工作流量特性串联管道对调节阀工作流量特性Effectofpipelinesinseriesontheworkingflowcharacteristicsofcontrolvalves另一种常见的安装形式——与管道并联Anothercommoninstallationform-parallelconnectionwiththepipelineWorkingflowcharacteristicsofcontrolvalvesinparallelwithpipelines与管道并联时调节阀工作流量特性当并联管道上的阀门打开（全开或部分打开）时，调节阀的（总管道）流量特性曲线如图所示。Whenthevalveonthepipelineinparallelisopened(fullyorpartially),theflowcharacteristicscurveofthecontrolvalve(mainpipeline)isasshowninthefigure.Workingflowcharacteristicsofcontrolvalvesinparallelwithpipelines与管道并联时调节阀工作流量特性相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)Workingflowcharacteristicsofcontrolvalvesinparallelwithpipelines与管道并联时调节阀工作流量特性当S=1，即旁通管道（阀门）关闭时，调节阀总流量特性与理想流量特性一致。WhenS=1,thatis,thebypasspipeline(valve)isclosed,thetotalflowcharacteristicsofthecontrolvalvematchtheidealflowcharacteristics.相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)Workingflowcharacteristicsofcontrolvalvesinparallelwithpipelines与管道并联时调节阀工作流量特性随着旁通阀逐渐打开，旁通流量逐步增大，S持续减小，调节阀可调范围不断下降。控制的流量越来越小，直至失去流量控制作用。Asthebypassvalveisgraduallyopened,thebypassflowgraduallyincreases,Scontinuestodecrease,andtheadjustablerangeofthecontrolvalvesteadilydeclines.Thecontrolledflowbecomesincreasinglysmalleruntiltheflowcontrolfunctionislost.相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)Workingflowcharacteristicsofcontrolvalvesinparallelwithpipelines与管道并联时调节阀工作流量特性总管道的串联管阻（力）会使调节阀特性发生畸变，导致调节阀流量控制能力进一步下降。Theresistanceofpipelinesinseriesofthemainpipelinewilldistortthecharacteristicsofthecontrolvalve,furtherreducingitsflowcontrolcapability.相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)Workingflowcharacteristicsofcontrolvalvesinparallelwithpipelines与管道并联时调节阀工作流量特性结论Conclusions

旁路流量占总流量比例不能太大，否则并联调节阀流量的有效调节范围会变得很小，失去流量调节作用。

Theproportionofbypassflowtototalflowshouldnotbetoolarge,otherwise,theeffectiveadjustablerangeoftheflowofthecontrolvalveinparallelbecomesverysmall,losingtheflowcontrolcapacity.相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)相对行程l/L(%)Relativestrokel/L(%)相对流量Q/Qmax(%)RelativeflowQ/Qmax(%)Caseanalysis案例分析Caseanalysis案例分析某化工厂的反应釜温度控制系统:当调节阀开度在30%以下时，温度波动非常大，很难控制；而当开度超过70%后，又出现了调节过于迟缓的问题。Temperaturecontrolsysteminthereactorofachemicalplant:Whenthecontrolvalveopeningisbelow30%,temperaturefluctuationsbecomeextremelysevereanditisdifficulttocontrol;whentheopeningexceeds70%,thecontrolisoverlysluggish.核心原因Thecorereason实际工况中调节阀的工作流量特性偏离了理想的线性流量特性。Thedeviationofthecontrolvalve'sactualflowcharacteristicsfromtheideallinearflowcharacteristicsunderrealoperatingconditions.Caseanalysis案例分析某化工厂的反应釜温度控制系统:当调节阀开度在30%以下时，温度波动非常大，很难控制；而当开度超过70%后，又出现了调节过于迟缓的问题。Temperaturecontrolsysteminthereactorofachemicalplant:Whenthecontrolvalveopeningisbelow30%,temperaturefluctuationsbecomeextremelysevereanditisdifficulttocontrol;whentheopeningexceeds70%,thecontrolisoverlysluggish.在理想状态下，线性流量特性的调节阀流量与开度成线性关系，能均匀调节流量。Underidealconditions,amongthelinearflowcharacteristics,theflowofthecontrolvalvehasalinearrelationshipwiththeopening,enablinguniformcontroloftheflow.Caseanalysis案例分析调节阀并非孤立存在，会受到管道阻力和前后压差变化的影响：Controlvalvesdon'toperateseparatelybutwillbeaffectedbypipelineresistanceandupstreamanddownstreampressuredifferencedeviation:当调节阀开度在30%以下时，阀门开度小，流通面积小。Whenthevalveopeningisbelow30%,thevalveopeningissmallandtheflowareaisalsosmall.此时管道系统的阻力主要集中在调节阀上，阀前后压差较大。Insuchcase,theresistanceofthepipelinesystemismainlyconcentratedonthecontrolvalveandthereisasignificantupstreamanddownstreampressuredifference.Caseanalysis案例分析但由于开度小，流量对开度的变化非常敏感，微小的开度变化就会导致流量大幅波动，进而引起反应釜温度剧烈变化，表现为“难以控制”。Duetothesmallopening,theflowishighlysensitivetothechangeintheopenings-tinychangesinopeningcausesignificantfluctuationsinflow,triggeringviolenttemperaturefluctuationsinthereactor,manifestingas“difficultcontrol”.Caseanalysis案例分析而当开度超过70%后，阀门流通面积较大，此时管道系统的阻力更多由管道自身承担，阀前后压差变小。Whentheopeningexceeds70%,theflowareaofthevalveisrelativelylarge.Atthispoint,theresistanceofthepipelinesystemismainlybornebythepipelineitself,andtheupstreamanddownstreampressuredifferenceofthevalvebecomessmaller.Caseanalysis案例分析此时流量随开度的变化变得平缓，即使开度有较大调整，流量变化也不明显，导致对反应釜温度的调节作用减弱，表现为“调节过于迟缓”。​Atthispoint,theflowchangesbecomestableastheopeningdegreechanges,evensubstantialopeningadjustmentsgenerateminimalflowvariations,weakeningtemperaturecontrolfunctionofthereactorandmanifestingas“overlysluggishcontrol”.​Caseanalysis案例分析管道系统的存在Thepipelinesystem改变了调节阀实际的压差和流量关系Altersthevalve'sactualrelationshipbetweenthepr