蒸汽发生器传热管湍流激励功率谱密度计算

湍流激励是核蒸汽发生器换热管发生流致振动的重要机理之一,也是微振磨损的重要诱因。为计算换热管的微振磨损速率,需要首先获得湍流激励功率谱密度（PSD）,其此前只能通过试验的方法获取。为利用CFD方法获得换热管上的湍流激励功率谱密度,建立了蒸汽发生器换热管束流场的数值模型,基于LES方法计算得到了管束内部的流场分布,提取了传热管上所受流体力并计算得到了其功率谱密度,计算结果与试验结果吻合良好。结果显示,管束内部传热管所受流体力为具有尖峰特征的宽频信号,其能量集中在一定带宽内。其结果为利用CFD方法计算传热管微振磨损建立了基础。     

有压瞬变流激振理论及激振试验

对输流管道有压瞬变流波动产生的机理、传播特性进行分析,利用经典的液压波动方程对有压瞬变流激振进行数值计算。有压瞬变流激振试验测试了不同工况下不同测点的压力、速度、振幅等参数,并对其进行了对比性分析。结果表明,通过控制激波器及调定压力可实现对有压瞬变流激振的压力幅值、振动频率、位移和速度的可调与可控。     

一种受电弓动态特性试验台的研制

传统的受电弓动态特性试验系统工作频率不高,振动频率往往低于20 Hz。为了在更宽的频率范围内进行受电弓的动态特性试验,搭建了受电弓振动试验台,利用电液式激振方法模拟正弦振动环境。首先阐述了试验台的总体方案、组成以及工作原理,并设计了双闭环控制结构,最后为了测试系统的性能,进行了一系列的正弦定频、扫频试验。现场测试结果表明系统激振频率最高可达25 Hz,振幅可达8 mm,可以精确模拟弓网高频振动,对受电弓疲劳寿命及性能进行准确评估,为受电弓动态特性和结构参数优化研究提供了试验依据。     

基于FBG传感技术的深海立管涡激振动测试研究

为了探索光纤光栅传感技术在深海立管振动测试中的适用性,采用光纤光栅应变传感器,在大型波流耦合试验水池中进行了阶段流作用下大长细比深海立管的涡激振动测试。试验立管模型长为6.2 m,长细比为310,模型材料采用铜管,立管上部1.2 m处于均匀稳定的流场中,下部5.0 m处于静水之中。沿立管长度四面对称布置48个光栅测点,通过改变外流流速、内流流速和初始顶张力等影响因素,采集应变数据并结合模态分析理论,分析了不同工况下立管的振动频率、幅值及模态等振动特性,研究了阶段流作用下立管的涡激振动规律。结果表明,光纤光栅传感技术能很好地满足大长细比深海立管的涡激振动测试要求,能准确体现立管的应变时程、振幅和频率等振动特性,清晰反映出在不同外流速下立管振动的多模态特征及每阶主导频率下的锁振区间。     

轴向振动对近水平孔管柱减摩及屈曲的影响

为了解决近水平长钻孔孔内管柱受压后摩阻增大甚至管柱屈曲变形的问题,提出了轴向振动减摩和防屈曲方法。首先,建立了轴向振动减摩的力学分析模型,分析了振动减摩的内在力学机制;其次,建立了振动减摩的有限元模型,研究了激振力、激振频率对于减摩效果的影响关系,并通过现场试验进行了验证。研究结果表明：单个振动周期内管柱与孔壁摩阻存在方向变换现象,降低了单个振动周期内的平均摩阻;激振力越大,减摩效果越好;轴向振动的幅值和频率达到一定门限值后能够有效防止管柱屈曲变形,降低管柱摆动;对于长为200 m、直径为89 mm的通缆钻杆管柱,当激振力大于等于5 kN时,能够大幅度减小管柱与孔壁摩阻,防止管柱屈曲;平均摩阻与振动频率呈倒对数关系,随着激振频率的增大,平均摩阻先减小而后趋于稳定,当激振频率大于等于6 Hz后减摩效果趋于稳定。该研究结果对于减摩防屈曲钻具的研制以及钻孔工程施工具有指导意义。     

基于实验系统的电梯轿厢水平振动研究

针对导轨不平顺作用下曳引电梯轿厢的水平方向振动问题,对导轨在不同激振频率下电梯轿厢的动态特性进行了研究。设计了一套滚动导靴-导轨接触式电梯实验系统,该系统主要包含:电梯轿厢模型、滚动导靴装置以及激励系统;根据电梯系统零件繁多,轿厢、轿架结构件非标准化的情况,以及电梯固有频率经验值、相似性原理,建立了水平电梯振动分析实验平台,保证了实验系统与理论分析的契合性;将Lab VIEW数据采集技术应用到导轨的受迫振动实验中,利用DH1301型激振器给予其中一侧导轨两种不同频率的正弦激励,进行了测试,并收集了轿厢3个不同位置的水平振动加速度实验数据,并对其进行了频谱分析。研究结果表明:在不同的正弦激励频率下,激振频率越接近系统固有频率值,质心处水平振动加速度响应幅值越大。     

以管路为振动输出源的液压激振系统研究

根据有压瞬变流产生的原理,该文提出一种新型液压激振方式。该激振方式将高压管路作为新的激振源,利用激波器产生周期性的有压瞬变流,使高压管路产生振动。构建了管道产生振动的变频液压振动系统,建立了管路流固耦合的振动模型,仿真了振动的工作模态,并进行试验验证。管道的此种振动形式是一个非简谐的周期性振动,并能够受变频系统控制,表明该振动是可以被利用的。     

基于FBG传感技术的立管涡激振动过程分析

为深入研究光纤光栅传感技术在海洋立管涡激振动测试中的适用性,在风-浪-流联合水槽中进行均匀来流下立管涡激振动试验。数据测试采用光纤光栅传感器,同时采用动态电阻传感器作为对比。通过改变多级外流流速,对比分析基于两种传感技术的立管涡激振动过程差异。同时基于光纤光栅传感技术采集应变数据并结合频谱分析及模态理论,研究立管振动的主导频率、幅值及模态响应等振动特性。研究结果表明,光纤光栅传感技术对海洋立管的涡激振动测试性能优越,能够准确体现立管的应变时程、振幅以及主导频率等振动特性,清晰反映伴随流速进程的立管模态特征及涡激振动过程,同时由模态响应和涡激振动过程分析发现立管锁频区间的产生具有瞬时性及自激性规律,这对海洋立管的模型试验与工程设计具有较大的参考价值。     

不等频率比转置三角形管束流体弹性失稳试验研究

管壳式换热器是最为常用的热交换设备,管束的流致振动问题是设计和制造关注的重点,虽然换热器的设计过程对管束流致振动问题有所要求,但是由于管束的支撑存在不对称性,造成实际工作中的管束振动问题难以准确预测。采用水洞试验,研究了节径比为1.41的不同频率比转置三角形管束的流体弹性失稳特征,对比分析了振幅、频率响应和相图特性。结果表明,当R_f<0.8时,单弹性管模型很难准确预测管束横流向失稳临界流速。随着频率比R_f的减小,横流向失稳前振动形式由混沌形式向双周期振动转化,而顺流向振动形式在失稳后,则由准周期振动向双周期振动形式转化。同时,管束顺流向可能出现超过标准的振幅,在换热器设计和运行过程中应予以关注。     

管壳式换热器管束的约束条件对振动固有频率的影响

本文采用有限元方法,分析了管壳式换热器的换热管及管束的约束对其振动固有频率的影响。通过对比分析不同管板厚度下,单个换热管前三阶固有频率的变化特性,发现换热管的固有频率随着管板厚度的增加逐渐增加。分析了GB151-1999中给出的管束的振动特性,发现管束的固有频率在解析解频率附近范围内存在较多频率。因此,在计算换热管束振动特性时,为了获得较为精确的结果,采用有限元方法计算是有必要的。     

A study of mass flow rate measurement based on the vortex shedding principle

Mass flow rate measurement is very important in the majority of industry processes because the mass of fluid is not affected by ambient temperature and pressure as the volume will be. Conventional mass flow rate is normally derived from the volumetric flow rate multiplied by fluid density. The density can be obtained by a densitometer or calculated according to the temperature and pressure measured by a thermometer and pressure gauge respectively. However the measurement accuracy is not always satisfactory. Flowmeters directly measuring mass flow rate have been studied and developed recently, such as Coriolis and thermal flowmeters. Unfortunately they still have some limits in practical applications. A new method in which mass flow rate can be directly measured based on the vortex shedding principle is presented in this paper. As a vortex flowmeter, von Kàrmàn vortex shedding is generated by a bluff body (vortex shedder), leading to a pressure drop and pressure fluctuation. A single differential pressure sensor is employed to detect the pressure difference between upstream and downstream sides of the vortex shedder. Both vortex shedding frequency and pressure drop are contained from the output signal of the differential pressure sensor, so that the mass flow rate can be obtained from the pressure signal. Numerical simulation has been done to analyze the characteristics of the fluid field and design the measurement device. The Computational Fluid Dynamics (CFD) codes Fluent were used in the numerical simulation. Experiments were carried out with water and gas, and the results show that this method is feasible and effective to measure the mass flow rate. This method has also robustness to disturbances such as pipe vibration and fluid turbulence.     

The experiment of flow induced vibration in PWR RCCAs

Recently, severe wear on the shutdown rod cladding of Ulchin Nuclear Power Plant #1, #2 were observed by the Eddy Current Test (E.C.T.). In particular, the wear at the sixth card location was up to 75%. The test results indicated that the Flow Induced Vibration (F.I.V.) might be the cause of the fretting wear resulting from the contact between Rod Cluster Control Assemblies (RCCAs) and their spacing cards (guide plates) arranged in the guide tube. From reviewing RCCAs fretting wear reports and analyzing the general characteristics of F. I. V. mechanism in the reactor, geometric layout and flow conditions arround the control rod, it is concluded that the turbulence excitation is the most probable vibration mechanism of RCCA. To identify the governing mechanism of RCCA vibration, an experiment was performed for a representative rod position in which the most serious fretting wear was experienced among the six rod positions. The experimental rig was designed and set up to satisfy the governing nondimensional numbers which are Reynolds number and mass damping parameter. The vibration amplitude measurement by the non-contact laser displacement sensor showed good agreements in the frequency and the maximum wearing (vibration) location with Ulchin E. C. T. results and Framatome report, respectively. The sudden increase in the vibration amplitude was sensed around the 6th guide plate with mass flow rate variation. Comparing the similitude rod behaviour with the idealized response of a cylinder in flow induced vibration, it was found that the dominant mechanism of vibration was transferred from turbulence excitation to periodic shedding at the mass flow rate 90l/min. Also the critical velocity of the vibration in RCCAs was determined and the vibration can be prevented by reducing the bypass flow rate below the critical velocity.     

某火箭发动机振动试验装置结构设计及优化

火箭发动机振动试验装置是在做火箭发动机环境振动试验时,用来连接火箭发动机与振动台体的必需工装.对某火箭发动机振动试验装置进行了结构设计,采用了箱体、托架和包带组合的结构形式,并利用ANSYS有限元分析软件对装置的整体结构进行了强度校核和模态分析.根据有限元分析结果,对主要影响装置整体强度和固有频率的结构进行了优化设计,包括在箱体上布置加强筋、加大托架宽度、加大托架与下包带接触面积等措施.优化后振动装置的强度满足试验要求,且其一阶固有频率高于振动试验最高频率,不会发生共振.     

滚动轴承噪声与振动测试环境系统的改进

针对常规轴承噪声与振动测试环境系统的不足,提出一种更加完善的轴承噪声与振动测试系统。该系统采用房中房结构,内房和外房采用浮动连接,轴承驱动装置设计为穿墙驱动与无级调速等;测量载荷设计为无级可调,自动加载,测试装置所处环境的周边安装吸声尖劈,减少了外界环境的干扰。该测试环境系统用于测试和分析中小型家电轴承、电机轴承、汽车轴承、医疗器械等用各类轴承的噪声和振动,也可以测试轴承声压级噪声和声功率级噪声等。     

多级降压调节阀流激振动特性分析

分析某管路系统多级降压调节阀的流激振动问题,仿真得到调节阀小开度、中等开度、全开3种工况下压力、速度、漩涡速度云图、压力脉动时域与频域特性曲线及流激振动频率范围.利用热流固耦合模态分析得到调节阀固有频率.将流激振动主频与固有频率相对比,验证调节阀工作可靠性.分析得出:随着开度增大,各级降压效果明显,大涡逐渐形成小涡,且...     

阵列式扰振力测量平台及其测量策略

为了测量大质量设备的多维扰振力,设计了一种基于传感器阵列式分布的多维扰振测量平台.该平台基于压电传感器采用了冗余式阵列的振动测量策略,解决了大负载及高刚度的测量要求,避免了结构耦合引入的测量精度损失.同时,为了克服阵列式测量引入的冗余测量误差,本文基于广义逆求解法进行测量精度优化,针对不同的被测振源选取不同位置的传感器...     

一种扰流装置在管壳式换热器中的应用

利用有限体积法对一种应用于列管式换热器壳程入口处的螺旋扰流装置进行了流体动力学计算和分析.分析结果表明:该螺旋扰流装置能够改变壳程流体入口流向,具有流阻小,减少流动死区,提高换热效率,降低管束振动等特点.     

Experimental investigation on the flow-induced noise under variable conditions for centrifugal pumps

With extensively using of centrifugal pumps,noise generation in these pumps is increasingly receiving research attention in recent years.The noise sources in centrifugal pumps are mainly composed of mechanical noise and flow-induced noise.And the study of flow-induced noise has become a hotspot and important domain in the field.The flow-induced noise closely related to the inner pressure pulses and vibration of volute in pumps,therefore,it is necessary to research the interaction and mechanism among them.To investigate the relationships,a test system is designed which includes a test loop and a measurement system.The hydrophones and pressure sensors are installed on the outlet of the pump and vibration acceleration sensors are disposed on the pump body.Via these instruments,the signals of noise,pressure pulses and vibration are collected and analyzed.The results show that the level of flow-induced noise becomes smaller as the flow increment during low flow rate operations,and it is steadily close to the design point,then it increases with the growing of flow rate in high flow rate conditions.Furthermore,there are some similar peak points in the power spectrum charts of noise,pressure pulses and vibration.The broadband noise at low flow rate is mostly focused on the region of 0-40 times shaft frequency,which is mostly made by rotating stall and vortex;while the noise at high flow rate conditions is focused on the region of 60-100 times shaft frequency,which may be mostly made by cavitations.The proposed research is of practical and academic significance to the study of noise reduction for centrifugal pumps.     

基于双目立体视觉的低频振动测量

为了满足物体振动的测量要求,基于双目立体视觉测量的原理,设计了一套可以在线采集、离线处理的非接触式低频振动测量的视觉系统。通过滤波去除噪声,采用Canny算子和最小二乘法椭圆拟合提取到标志点的轮廓和中心坐标,在已知特征点的空间分布规律的条件下,通过相应的坐标排序方式,对左右视图对应特征点进行准确的匹配,获得了特征点的三维坐标数据。最后对比每一帧图像中对应特征点三维坐标数据,得到待测物的振动信息。通过直线导轨作为振动源带动待测物运动的方式进行了测量实验,实验结果显示,该系统的检测精度达到±0.15mm/m以上,基本满足低频振动测量的稳定可靠、精度高等要求。     

车用扭振减振器性能检测试验台

为解决车用扭振减振器与发动机匹配实验危险系数较高的问题,基于虚拟仪器技术开发了一套车用扭振减振器性能检测试验台.试验台控制系统模拟车用发动机产生扭转振动,通过变频器及变频电机实现了扭振激励的转速、频率及振幅可调.信号采集系统由多路磁电传感器及NI-DAQ采集设备组成.试验台采用高频记数原理,记录测速齿盘旋转过程中每一齿...