PIV measurement on internal instantaneous flows of a centrifugal pump

In this paper,the internal flow field in a centrifugal pump working at the design flow rate operating condition has been measured using the particle image velocimetry(PIV)technique with the fluorescent particles and the index-matched fluid technology.The index-marching fluid with the same refractive index as the transparent material has been prepared and applied in the present test of pump with geometrical complex walls.The comparison between velocity distributions of PIV results both with and without fluor...     

扫描光屏法在PIV技术测量自由剪切层中的应用

ＰＩＶ技术是九十年代实验流体力学的重大成就。它能够提供瞬时整个流场的定量信息，而且具有很高的空间分辨率和很好的精度。为了获得清晰可靠的ＰＩＶ底片，人们对实验方法作了很多改进。本文讨论了近年使用较多的扫描光屏法，提出了该方法在使用中特别注意的一些问题，并给出了用该方法测量自由剪切流场的结果。     

基于MEMS技术的微流体混合器及相关技术

介绍了基于MEMS技术的微流体混合器及相关技术,给出了各种微流体混合器的结构、原理和特点,同时对微管道中流体混合的仿真、实验技术以及微管道中微量流体混合程度的评价方法等作了概述。     

旋转切向流强化管式膜微滤机理研究

首次设计出了旋转切向流管式膜分离器及其实验系统，通过理论研究和实验测试，系统地研究了旋转直线切向流和旋转圆弧切向流聚丙烯管式膜微滤的流场特征，揭示了旋转切向流强化膜微滤的机理。     

Fully Stratified Particle-Laden Flow in Horizontal Circular Pipe

This article describes the results of an experimental measurement and visualization of coarse-grained fully stratified particle-water mixtures. This article focuses on the study of the carrier liquid velocity field and behavior and local velocities of conveyed particles. Glass balls and graded pebble gravel of 6 mm mean diameter were conveyed by water in a horizontal smooth pipe loop with a transparent pipe viewing section of inner diameter 40 mm. The measurements were performed in the smooth pipe and the pipe with rough stationary bed created by two layers of spherical particles of the same mean diameter as the conveyed particles. Particle movement along the pipe bottom was studied and the effect of the stationary bed on local velocity values of the carrier liquid and conveyed particles were evaluated. It was concluded that in the flow with stationary bed the maximum liquid velocity is markedly shifted from the pipe center to its top. The coarse-grained particles moved principally in a layer close to the pipe invert, for higher flow velocities particle saltation becomes the dominant mode of transport.     

旋流燃烧室内等温流场特性的研究

采用三维轴对称RNG k ε湍流模型模拟了微型燃气轮机旋流燃烧室内的等温流场,用粒子测速仪(PIV)测量了旋流燃烧室内不同截面位置的速度矢量分布。对数值模拟结果与实验数据进行了比较分析,研究结果表明:旋流空气在燃烧室头部形成回流区,PIV实验测量的中心回流区范围小于计算结果,燃烧室中心轴的速度小于周围区域的速度,旋流燃烧室内的环向速度衰减较慢,燃烧室内充满旋流。在实验过程中,发现垂直于轴向的横截面PIV测量结果优于轴向截面的PIV测量结果;适当地增加光面厚度,有利于捕捉到更多的粒子,提高测量精度。图6参7。     

Simultaneous visualization of flow field and evaluation of local heat transfer by transitional impinging jets

A combined approach has been employed to characterize the flow field and local heat transfer in jet impingement configurations, featuring a mass transfer experiment and a digital visualization technique. A jet velocity range is spanned to ensure flow regime transition.The well-known heat/mass transfer analogy has been used to infer on the local heat exchange on a infinite plate. In this experiment, a naphthalene film is ablated from a disk, due to jet exposure. Automated contact measurements of the variation of film depth in the stagnation region and beyond have been performed. From the local naphthalene loss rate the local heat transfer is then inferred. Coherent structures are created both at the interface between free jet and quiescent medium and upon impingement at plate, and need to be visualized in the vicinity of stagnation. To this end a particle image velocimetry system is exploited to extract the two components velocity instantaneous information.Ablation measurements confirm the non-monotonic progress of local heat transfer for small nozzle-to-plate spacings. The visualizations evidence that local heat transfer is strongly influenced by impingement structures: the maximum heat transfer coefficient offset which can be detected is due, even for laminar or transitional jet, to large-scale toroidal vortices impacting on the plate.     

过冷沸腾汽泡顶部射流可视化实验研究

通过商速摄像井配合激光PIV技术，对过冷沸腾中微小汽泡顶部射流进行细致现察，确认过冷沸腾中顶部射流的存在，测量显示其速度场，具体分析讨论此类射流与汽泡生长的联系。     

利用切向进气降低压气机喘振流量的研究

采用粒子图像速度场仪 (PIV)对叶轮进口处的旋流速度场进行测定 ,研究了切向进气装置的不同结构和工作参数对压气机叶轮进口处旋流流场的影响规律 ,并对采用切向进气方式降低压气机喘振流量进行了试验研究。试验结果表明 :采用切向进气能够有效改变压气机叶轮进口处气流的预旋角 ,可以通过改变切向进气装置的结构和工作参数来改变叶轮进口处的旋流场。压气机逼喘试验结果证明 ,即使采用简单的切向进气结构也能够有效降低压气机的喘振流量     

用PIV方法研究四气门汽油机缸内滚流运动

选取一台Cagiva350单缸四气门汽油机作为试验样机,重新设计了具有透明活塞顶和透明缸套的加长部分,并使之与丰田8A汽油机的基本参数接近,以二氧化钛为示踪粒子,采用激光粒子图像速度法(PIV)研究了该样机在进气和压缩冲程缸内滚流流场的变化情况.研究结果表明,滚流在进气过程中开始形成,逐渐演变成与缸径同大的大尺度旋涡,并在实验所能实测的曲轴转角范围内一直保持,在60°CABTDC时旋涡发生严重畸变,但仍未破碎为小尺度的湍流.