稀薄气体流动的粒子图像测速实验研究

建立了一套可对真空度进行调节的实验装置,从大气压开始逐渐降低系统压力,进行系列稀薄气体流动的PIV流场实验.系统压力从101kPa、90kPa逐次降至10kPa,使用所选粒子在不同系统压力下分别进行PIV实验获得测量区域流场分布情况.运用计算流体力学的方法模拟大气压条件下实验区域的内部流动,对比结果发现该种条件下数值模...     

基于PIV技术的磨料水射流中固体磨料粒子速度分布实验研究

为了解决磨料射流磨料速度测试难问题,本文基于PIV技术,结合图像处理与滤波分析技术,提出了一种测量磨料射流磨料速度的非接触式测试方法。该方法能同时得出磨料速度以及磨料在射流中的位置信息。利用该方法对磨料射流进行磨料速度测试实验,实验结果表明：(1)利用该方法能快速地得到磨料射流中磨料速度;(2)利用该方法得到了磨料在喷嘴出口沿射流方向的速度变化规律,即磨料在喷嘴出口速度先增大后减小,存在速度最大处,意味着磨料射流存在最优靶距;(3)利用该方法得到了磨料沿射流径向的速度变化规律,磨料在射流中心速度最大,其速度从射流中心往射流边界方向逐渐减小,呈现出钟形速度分布。     

Application of particle image velocimetry for measuring He II thermal counterflow jets

The particle image velocimetry (PIV) technique was successfully applied for measuring the velocity of a He II thermal counterflow jet. Neutrally buoyant hydrogen-deuterium solid particles were used as tracer particles for PIV measurement. In the application, the normal component velocity was measured. The jet velocity profile and spatial decay of the jet velocity were compared with those of turbulent round jets of ordinary viscous fluids. The velocity measured near the jet nozzle exit was compared with the theoretical prediction for the normal component flow velocity.     

基于可调谐半导体激光吸收光谱法测定天然气水露点技术研究

天然气水露点是关系天然气管道输送安全的重要指标之一,基于可调谐半导体激光吸收光谱技术(TDLAS)设计开发了天然气水露点分析装置.根据天然气现场应用需求,搭建天然气在线分析计量装置并进行测试,进行了激光法天然气在线分析计量装置关键技术集成与装备试制.开展了仪器的离线标定及实验室稳定性测试,在天然气输气站现场开展了仪器的...     

Temperature and velocity measurement fields of fluids using a schlieren system

This paper proposes a combined method for two-dimensional temperature and velocity measurements in liquid and gas flow using a schlieren system. Temperature measurements are made by relating the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the schlieren system. The same schlieren images were also used to measure the velocity of the fluid flow. The measurement is made by using particle image velocimetry (PIV). The PIV software used in this work analyzes motion between consecutive schlieren frames to obtain velocity fields. The proposed technique was applied to measure the temperature and velocity fields in the natural convection of water provoked by a heated rectangular plate.     

共路激光干涉测量系统的研究

激光干涉测量系统在精密测量领域占有重要地位,它对温度变化、大气变化、激光波长变化、机械安装误差和外界振动等比较敏感,影响系统的测量精度和稳定性。针对此情况,该文提出一种新型的激光干涉光路,两光臂呈完全共路结构,使干涉条纹信号具有极强的抗干扰能力;对光路进行抗干扰分析和理论推导;构建位移测量系统,进行系统测试实验和误差分析。实验表明,本系统测量分辨力0.72nm,合成标准不确定度5．2nm（k=2）,运行速度0．56mm／s,量程0．01mm。     

Novel particle image velocimetry system based on three-color pulsed lamps and image processing

A novel particle image velocimetry (PIV) measurement system based on flashed lamps as light sources and digital reconstruction of particle positions by image processing is presented. Three different colors are used in order to distinguish, on a same photograph, the corresponding positions of each moving particle at three different instants of time. This solution can give significant advantages in several aerodynamic and hydrodynamic situations. In particular, it allows high flexibility for velocity measurements and independent settings of different acquisition parameters, like pulse powers and timing. Furthermore, the developed PIV measurement system is fully transportable, eye-safe, practical, and economical. The first hydrodynamics measurements achieved by using the proposed velocimetry measurement system are reported.     

经验模态分解和空间滤波在两相流速度测量中的应用

在利用空间滤波和电容传感器测量两相流速度时,需要准确测量电容传感器输出信号的带宽.针对此问题提出一种利用经验模态分解算法来测量传感器带宽的方法.文章首先介绍电容传感器的空间滤波效应和经验模态分解的基本原理,并给出固体速度和电容传感器输出信号带宽之间的关系.然后将经验模态分解和平滑滤波器结合对测量信号进行平滑处理,测量处...     

电能表现场校验仪在线测量引入的附加误差的研究

文中旨在探讨电能表现场校验仪在线测量电能表时可能引入的附加误差及纠正措施。根据电能表现场校验仪的工作原理,并结合工业现场的实际应用情况,分析影响电能表现场校验仪的测量结果的典型分量,确定各分量所带来的附加干扰,并提出相应的预防纠正的措施,确保电能表现场校验仪在线测量的准确性。     

On-line fault detection and diagnosis obtained by implementingneural algorithms on a digital signal processor

A measurement instrument for on-line fault detection and diagnosis is proposed. It is based on the implementation of a neural network algorithm on a processor specialized in digital signal processing and provided with suitable data acquisition and generation units. Two specific implementations are detailed. The former uses the neural-network to simulate on-line the correct system behavior, thus allowing the fault detection to be achieved by comparing the neural network output with the measured one. The latter uses the neural network to classify on-line the system as correct or faulty, thus allowing the fault detection and diagnosis to be achieved simultaneously. These two implementations are applied to detect on-line and diagnose faults on a real system in order to point out different fields of application and to highlight the performance of the measurement apparatus     

Study of Particle Motion in He II Counterflow Across a Wide Heat Flux Range

Some discrepancy exists in the results of He II counterflow experiments obtained using particle image velocimetry (PIV) when compared with those obtained using particle tracking velocimetry (PTV): using PIV, it was observed that tracer particles move at roughly half the expected normal fluid velocity, \(v_n/2\), while tracer particles observed using PTV moved at approximately \(v_n\). A suggested explanation is that two different flow regimes were examined since the range of heat flux applied in each experiment was adjacent but non-overlapping. Another PTV experiment attempted to test this model, but the applied heat flux did not overlap with any PIV experiments. We report on the beginnings of a study of solid \(\hbox {D}_2\) particle motion in counterflow using PTV, and the heat flux range overlaps that of all previous visualization studies. The observed particle velocity distribution transitions from a two-peak structure to a single peak as the heat flux is increased. Furthermore, the mean value of one peak in the bi-modal distributions grows at approximately the same rate as \(v_n\), while the mean value of the single-peak distributions grows at roughly \(0.4v_n\), in reasonable agreement with both previous experiments and with the suggested model.     

基于激光位移传感器的手持式轮对尺寸测量仪设计

针对轨道交通轮对几何尺寸检测需求不断增加、检测工具自动化水平低、检测精度低的现状,设计一种基于一维激光位移传感器的手持式轮对尺寸测量仪。该设备以STM32F407芯片作为微控制器,通过控制直线步进电机,配合激光位移传感器实现对轮对廓形二维点云数据的采集,采用基于中值误差与连续度调整权值的平滑算法对点云数据预处理,采用基于轮对轮廓特征的廓形匹配实现轮对尺寸参数的计算。该仪器对车轮轮廓进行全面记录和质量评估,试验证明,该设备在保持较高测量精度的情况下,同时具有高效测量、长时间工作等特点。     

A stereo PIV system for measuring the velocity vector in complex gas flows

A stereo PIV system for investigating complex highly turbulent flows, typical for gas flows in aircraft engines and gas turbines, is developed, and the values obtained for the velocity are compared with the results measured using a laser Doppler anemometer. The features of the use of the PIV system for measurements in three-dimensional highly turbulent flows with high velocity gradients are investigated.     

A virtual instrumentation system for integrated bearing conditionmonitoring

This paper presents the design, optimization, and implementation of a virtual instrument (VI), which is an essential part of an integrated bearing condition monitoring system. The VI is designed using the graphical programming language LabVIEW and is capable of performing on-line measurement functions, including data acquisition, display, and analyses in the time and frequency domains, as well as data archiving. The issues of data length selection and VI real-time capability have been investigated to optimize the VI operation and improve data-processing efficiency. The VI system presents an effective and user-friendly human-machine interface for on-line bearing condition monitoring, which is of critical importance to real-time fault diagnosis and intelligent manufacturing     

线性运动平台多自由度几何运动误差测量技术

线性运动平台是精密制造和测量的基础,其定位精度直接影响着制造和测量的精度。由于制造和装配误差的影响,运动平台存在六个自由度的运动误差,将影响运动平台的定位精度。为了提高运动平台的定位精度,需要准确地测量各项运动误差。传统的测量方法只能对单一误差进行测量,并且测量仪器体积较大,无法集成在运动平台中进行实时误差测量。本文提出了一系列成本低、体积小、易集成的高精度多自由度几何运动误差同时测量技术,可以根据测量需求选择测量系统的自由度,在提高测量精度的同时,还可以实现在线测量,为提高线性运动平台运动精度起到重要作用。     

A New Method for Measuring Cake Thickness by a Powder Pressure—Displacement System

An on-line powder pressure–displacement measurement system was developed based on a static measurement instrument (vernier caliper). This system consists of a pressure sensor and a displacement subsystem, and has the on-line capability to measure the thickness of powder packing with different powder sizes. The design principle employs a pressure sensor to determine the thickness by different signals generated when the pressure sensor contacts the free surface zone of powder packing and when it contacts the other powder zone. The powder materials adopted to validate this newly developed system were glass beads, sand and dust. This measurement technique can be applied under different measurement conditions.     

摄象法热轧圆钢直径在线检测的研究

阐述了摄象法实现热轧圆钢的直径在线检测原理。通过研究热轧圆钢运动时的物距变化摄象法在线检测的影响,提出了建立热轧圆钢运动中的相对监测系统。分析了摄象法热轧圆钢直径在线检测系统的误差,并给出了该系统综合误差的补偿方法以及测量小型棒材的综合测试结果。     

圆形重力式网箱流场效应的试验研究

为探索圆形重力式网箱在动态流场中的水动力学特性,同时获得网箱系统内部与周围流场分布及流速变化规律,设计了4种不同网目形状和不同网目大小的网箱模型(C1、C2、C3、C4),选取4种不同水流流速(0.068 m/s、0.105 m/s、0.143 m/s、0.182 m/s),分别采用声学多普勒流速仪(ADV)和粒子图像测速(PⅣ)技术对网箱系统内外的流速及流场变化进行测定。结果表明,ADV试验与PⅣ技术测量结果基本一致;来流速度不同时,单个网箱范围内的水流衰减程度差异不大;来流速度相同时,小网目网箱的减流效果优于大网目网箱;网目大小相同时,菱形网目网箱减流效果优于方形网目网箱;群组网箱减流效果明显,且随着水流通过网箱数目的增加,网箱内与网箱后的流速降低明显,其中第2个网箱中心的流速衰减率已经达到了67.6%,第4个网箱中心的流速衰减率为88.2%,网箱后的流速衰减率为72.1%。研究结果可为养殖生产实践中网箱类型的选择提供理论参考。     

基于PIV技术的复合流道板式结构实验

目的在包装工程流场测量的研究中,验证粒子图像测速(PIV)技术的可行性。方法用超白玻璃制作复合流道板式换热器的模型,基于PIV技术采集被测区域图像,应用互相关分析法进行计算,获得流场数据,并与数值模拟结果比对进行验证。结果实验结果流型清晰,数据和数值模拟基本一致。结论PIV技术可应用于流动复杂、非接触的包装工程类的流场测量,且超白玻璃是一种理想实验材料,能够为拓展该领域的探索思路提供参考。     

High-Resolution Precision Digital Tachometer

A new approach to the digital measurement of angular velocity is presented. This new instrument performs the division by time that has been carefully avoided in the existing instruments. The accuracy and resolution of the transducer does not depend upon the number of quantizations/revolution. The measurements can be made in a very short time, leading to up to 14700 samples per second. An important feature of this instrument is that even at speeds close to zero (or at zero), the error is less than 0.02 percent and 1600 samples of the angular velocity can be obtained/second. This makes the instrument particularly suitable for the study and control of the transient behavior of motors and other rotating devices.