一维流固耦合振动问题的有限元分析

流体管道的振动，是典型的一维流固耦合振动，管内流体振荡引起管道产生机械振动．而管道机械振动反过来又会影响管内流体的动态行为。本文应用半解析有限单元法对流体管道固有特性的数值解进行了研究。半解析单元采用了周向解析、轴向离散的位移函数，可减少计算量，节省计算时间。     

Inconel 625镍基合金管道焊接残余应力的数值模拟

以Inconel 625镍基合金管道的焊接接头为研究对象,建立了热-力学耦合的三维有限元模型,采用ANSYS软件对该合金管道环焊缝对称焊的残余应力进行了数值模拟,分析了管道外表面轴向和环向残余应力分布,并进行了试验验证;此外,还分析了预热温度对管道残余应力的影响。结果表明:该合金管道焊后外表面轴向与环向残余应力的模拟结果与试验结果在数值和分布趋势上均比较吻合,证明了模型的准确性;在焊缝及近焊缝区的管道外表面形成了轴向压应力和环向拉应力,随着距焊缝中心距离的增加,轴向压应力逐渐变为拉应力,而环向拉应力逐渐转变为压应力,并最终趋向于0;随着预热温度的升高,管道外表面轴向和环向残余应力均降低。     

外在激励对流体静压型机械密封动态稳定性的影响

机械密封动力学性能对密封系统稳定性有很大的影响,微小的振动会导致密封泄漏量增加和端面磨损加剧。根据机械动力学原理,建立了流体静压型机械密封静环轴向振动和角向摆动的动力学耦合方程,通过解耦得到两个独立的线性振动方程。在Simulink环境下,利用MATLAB软件编程模拟分析了几种典型的外在激励对密封环动态稳定性的影响,得到最佳的试验密封环结构参数值。模拟分析表明,若要密封环在角向有尽量小的摆动,就必须选取较大的转折半径,且端面锥角尽量趋向于零;若要减小轴向的振动强度,就须减小端面锥角,且尽量避免取转折半径可选范围的中间值。     

惯性冲击式运动原理的理论分析与仿真

利用拉格朗日方程建立基于惯性冲击式驱动原理的微小型机器人的动力学模型，对该模型进行求解与仿真；利用有限元分析方法对机器人机构连行模态分析与瞬态动力学分析。两种分析方法都考虑了双压电膜机构与电场的耦合关系，以及机器人的支撑与管壁之间的接触摩擦。通过对两种方法的分析结果对比，验证了惯性冲击式运动原理的正确性，以及该原理用于管内移动微小型机器人驱动是可行的。     

流固耦合效应对输液管道的振动影响研究

压力管道系统中存在流体和结构之间的耦合振动。在考虑流固耦合效应的情况下,应用ADINA中流固耦合分析求解器ADINA-FSI,建立了输液管道的直管有限元模型,介绍了管壁模型和流体模型的建模过程以及流固耦合计算过程、压力突变和约束的施加以及模型参数选择等。依据仿真结果,分析了压力突变、管道模型和简支等因素对管道振动的影响。有压流动对管道横向和轴向振动的影响受到支承条件的影响,固支数量的增多有助于消减压力突变等因素引起的管道振动,管道及流体参数的合理选取等也对振动有重要影响。     

非接触机械密封的非线性动特性系数及瞬态振动响应分析

建立了考虑倾斜情况的弹性补偿单元支撑的非接触机械密封瞬态振动响应分析模型,该模型包括了瞬态Reynolds方程、运动方程以及二阶非线性动特性系数求解方程等。采用Euler法求解获得了非接触机械密封在轴向振动位移和静环倾角随时间变化时的瞬态振动响应特性。计算得到瞬态油膜力作用下的密封轴向力和倾覆力矩相关的14个动特性系数。结果表明：密封间隙内流体阻尼对密封副和摆动的影响是线性的;密封副瞬态振动影响油膜厚度分布,从而引起油膜压力分布发生变化,结果导致密封环发生摆动;密封副摆动同样也会引起密封轴向振动。     

非稳定流输送管道的耦合振动

以Timoshenko梁模型为基础,通过连续方程和动量方程建立了非稳定流输送管道的耦合振动非线性偏微分方程组,这些偏微分方程通过管壁-液体接触面的力平衡、法向速度协调方程以及流体质量守恒和动量守恒而完全耦合。耦合包括管道与液体之间的摩擦耦合、系统轴向振动与横向振动之间的耦合、管道径向与轴向的Poisson耦合。以该模型为基础分别得到了一次简化模型和用于预测输液管道流固互动现象的扩展水锤4-方程模型。分别采用一次简化模型和4-方程模型对一实验进行仿真,并与实验结果进行了比较,表明一次简化模型的仿真结果比4-方程模型更能反映耦合的影响。     

利用流体能量的管道机器人速度计算与控制

研究一种利用流体能量驱动和发电的管道机器人,该机器人完全浸润在充满流动介质的管道内,利用流体压力以及流体速度能量获得驱动力。机器人随着管内流体的流动向前推进,需要克服惯性质量以及与管壁之间的摩擦阻力的影响,对于不同的流体介质,机器人需要根据工作要求自动进行速度调节,因此必须对机器人的结构和尺寸进行合理设计,确定管道内的流体力学条件,并设计速度控制装置,对机器人速度实现行为控制。     

螺旋槽干气密封系统非线性动力学行为分析

建立了轴向振动下气膜-密封动环系统动力学模型,利用Maple程序求解了轴向振动方程,获得了螺旋槽结构参数响应的振动相轨图、Poincaré映射图和时间历程图,进而分析了螺旋槽干气密封系统非线性动力学行为。研究结果表明:在特定的螺旋槽结构参数范围内存在着振动混沌现象,通过选择合理的螺旋槽结构参数可以控制混沌,为干气密封动态优化设计提供了理论基础。     

爆炸地震波作用下埋地管道流固耦合动力响应研究

为了探讨埋地管道在爆炸地震波作用下的响应问题,在考虑管内运动流体的情况下,利用数值模拟的方法建立了埋地管道外爆流固耦合模型,并进行了动力响应分析。基于该模型,对比分析了运动流体对管道在爆炸地震波作用下的响应影响,并通过设置不同流体压力、不同流体流速进一步探讨管内流体运动状态对管道响应的影响。结果表明,管内运动流体的存在能有效抵抗爆炸地震波给管道带来的振动效应,选取的充液管道模型应力变化范围比空管缩小了88%,随着流体输送压力的升高,爆炸地震波对管道的振动影响越小;随着流体流速的升高,爆炸地震波对管道的振动影响越大,管道振动越明显。     

Verification of the Theoretical Model for Analyzing Dynamic Behavior of the PIG from Actual Pigging

This paper deals with verification of the theoretical model for dynamic behavior of Pipeline Inspection Gauge (PIG) traveling through high pressure natural gas pipeline. The dynamic behavior of the PIG depends on the differential pressure across its body. This differential pressure is generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze the dynamic behavior characteristics such as gas flow in pipeline, and the PIG position and velocity, not only the mathematical models are derived, but also the theoretical models must be certified by actual pigging experiment. But there is not any found results of research on the experimental certification for dynamic behavior of the PIG. The reason is why the fabrication of the PIG as well as, a field application are very difficult. In this research, the effectiveness of the introduced solution using the method of characteristics (MOC) was certified through field application. In-line inspection tool, 30” geometry PIG, was fabricated and actual pigging was carried out at the pipeline segment in Korea Gas Corporation (KOGAS) high pressure system, Incheon LT(LNG Terminal) -Namdong GS(Governor Station) line. Pigging is fulfilled successfully. Comparison of simulation results with experimental results show that the derived mathematical models and the proposed computational schemes are effective for predicting the position and velocity of the PIG with a given operational conditions of pipeline.     

Modeling and simulation for PIG with bypass flow control in natural gas pipeline

This paper introduces modeling and simulation results for pipeline inspection gauge (PIG) with bypass flow control in natural gas pipeline. The dynamic behaviour of the PIG depends on the different pressure across its body and the bypass flow through it. The system dynamics includes: dynamics of driving gas flow behind the PIG, dynamics of expelled gas in front of the PIG, dynamics of bypass flow, and dynamics of the PIG. The bypass flow across the PIG is treated as incompressible flow with the assumption of its Mach number smaller than 0.45. The governing nonlinear hyperbolic partial differential equations for unsteady gas flows are solved by method of characteristics (MOC) with the regular rectangular grid under appropriate initial and boundary conditions. The Runge-Kuta method is used for solving the steady flow equations to get initial flow values and the dynamic equation of the PIG. The sampling time and distance are chosen under Courant-Friedrich-Lewy (CFL) restriction. The simulation is performed with a pipeline segment in the Korea Gas Corporation (KOGAS) low pressure system, Ueijungboo-Sangye line. Simulation results show us that the derived mathematical model and the proposed computational scheme are effective for estimating the position and velocity of the PIG with bypass flow under given operational conditions of pipeline.     

Development of inspection gauge system for gas pipeline

An autonomous pipeline inspection gauge system has been developed for determining position, orientation, curvature, and deformations such as dents and wrinkles of operating pipelines by Korea Gas Company and Seoul National University. The most important part of several subsystems is the Strapdown Inertial Measurement Unit (SIMU), which is integrated with velocity and distance sensors, weld detection system, and digital recording device. The Geometry Pipeline Inspection Gauge (GeoPIG) is designed to operate continuously and autonomously for a week or longer in operating gas pipelines. In this paper, the design concepts, system integration, and data processing/analysis method for the PIG will be presented. Results from the recent experiment for a 58 kilometer gas pipeline will be discussed.     

超(超)临界疏水阀开阀水锤及管道振动

针对超(超)临界疏水阀开阀水锤及阀后管道振动问题,运用充液管道振动分析的流固耦合理论及特征线法,建立开阀水锤及管道振动的数学模型,求解得到疏水阀在不同流量特性及不同套筒层数下阀开启时水锤压力、流体流速、管道轴向内力和管道振速的时域曲线。研究结果表明:水锤压力取决于流体的流速与压力相互作用,管道内力受水锤压力影响较大,局部受管道振速影响;额定流量恒定时,线性流量特性下水锤峰值压力明显小于快开特性,流速大于等百分比特性,超(超)临界疏水阀宜选用线性流量特性;随着套筒层数增加,水锤压力峰值和管道轴向内力峰值减小,但开阀初始阶段流速波动和管道振动增加。     

Modeling and simulation for PIG flow control in natural gas Pipeline

This paper deals with dynamic analysis of Pipeline Inspection Gauge (PIG) flow control in natural gas pipelines. The dynamic behaviour of PIG depends on the pressure differential generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze dynamic behaviour characteristics (e.g. gas flow, the PIG position and velocity) mathematical models are derived. Two types of nonlinear hyperbolic partial differential equations are developed for unsteady flow analysis of the PIG driving and expelled gas. Also, a non-homogeneous differential equation for dynamic analysis of the PIG is given. The nonlinear equations are solved by method of characteristics (MOC) with a regular rectangular grid under appropriate initial and boundary conditions. Runge-Kutta method is used for solving the steady flow equations to get the initial flow values and for solving the dynamic equation of the PIG. The upstream and downstream regions are divided into a number of elements of equal length. The sampling time and distance are chosen under Courant-Friedrich-Lewy (CFL) restriction. Simulation is performed with a pipeline segment in the Korea gas corporation (KOGAS) low pressure system, Ueijungboo-Sangye line. The simulation results show that the derived mathematical models and the proposed computational scheme are effective for estimating the position and velocity of the PIG with a given operational condition of pipeline.     

飞机管路连接件装配偏差对密封性影响的仿真分析与试验验证*

为研究管道装配偏差对管路连接件密封性能的影响规律,建立管道连接件模型,提出有效密封的判定条件,并通过静力学仿真分析管接头接触面摩擦因数、管道装配偏差(轴向、径向及角度)对管接头连接件密封性能的影响。结果表明:拧紧力矩的增加会使密封性能增强,但超过某一极限值,管路连接件可能发生破坏;管接头与管道接触面的摩擦因数增加,密封性能降低;装配过程中的轴向偏差会降低密封性,甚至失去密封性;径向偏差和角度偏差会稍稍降低密封性,但管道会出现塑性变形。建立管道密封试验系统,试验验证了仿真分析的正确性。     

西气东输管道环焊缝强度匹配工艺探讨

采用失效评定图技术分析了油气长输管道特别是高强度大口径管道环焊缝不同强度匹配形式对管道极限承载能力以及抗断性能的影响。以西气东输管道为例，计算分析了环焊缝不同强度匹配对管道抗断能力的要求。最后综合各种因素分析了西气东输管道应采用的环焊缝匹配工艺。     

基于声检测的管道内检测器定位系统

管道内检测器是保证管道安全运营的重要工具,定位系统则用来确定管道中的内检测器位置.定位系统基于对声信号检测原理,采用三路信号采集和存储系统.针对硬件系统的非线性相位时延,本文设计了具有线性相位时延的FIR软件滤波系统,并应用互功率谱相位法计算三路信号相对时延,根据几何关系,得到内检测器位置.通过实脸验证了系统的定位作用...     

基于叶轮转子系统下的干气密封轴向振动分析*

为探究基于叶轮转子系统下干气密封轴向振动特性,基于干气密封结构特性,建立叶轮转子-轴承-干气密封系统轴向振动模型,采用待定系数法进行求解,推导得出静环轴向振动幅值表达式;建立叶轮转子-轴承-干气密封系统几何模型,运用ANSYS Workbench软件进行模拟仿真计算,分析气膜刚度和激振力对轴向振动的影响。结果表明:气膜刚度对动、静环振动幅值的影响不大;动、静环振动频率相同、振动幅值相同,说明动、静环的追随性高,其间隙稳定,从而保证干气密封的稳定运行;动、静环位振动幅值与激振力成正比关系,说明激振力严重影响干气密封的稳定性,为提高干气密封的稳定性,应平衡好叶轮的轴向激振力。