实验用离心泵叶轮内流场的PIV测量

离心泵叶轮内流场的流动规律直接影响泵的扬程、效率等外特性指标,利用PIV测试技术可以在不干扰流场的情况下,进行高精度的测量。在实验中,使用PIV测量技术测量了离心泵内部流场,得到了离心泵内的速度分布,初步掌握了离心泵在不同工作条件下内部的流动特性。     

全透明模型泵的设计及PIV流场测量

为了便于观察挖泥船泥泵内部的流动情况,设计了一台全透明模型泥泵。泵入口流道位于泵轴侧,便于对泵内部流场进行全域整体观测。探讨了泥泵的水力特性和可拍摄性,获得了叶轮内瞬时流场的速度矢量。结果表明,所设计的模型泵适用于PIV流场测量。     

PIV测量用模型泵的设计及测量中的误差分析

PIV(Particle Image Velocimetry)是进行离心泵内部流场研究的重要手段.为了研究离心泵内部流动情况,在参考现有离心泵结构的基础上,设计了一台PIV测量用有机玻璃模型泵,并对模型泵的可拍摄性能和水力性能进行了分析,表明模型泵适用于PIV测量,且水力性能满足要求.同时,介绍了模型泵、片光和CCD相机的布置及流场拍摄方法,分析了利用PIV测量离心泵内部流场过程中的主要误差:系统误差、示踪粒子跟随性导致的误差和光折射导致的误差,并对减小或消除误差的方法进行了探讨.     

离心泵叶轮内部湍流流动的数值计算及试验

对IH65型离心泵叶轮内部流动进行研究,基于Reynolds时均化的N-S方程和标准的k – e 两方程湍流模型,运用流场计算软件Fluent,计算该泵叶轮在不同工况下的内部流场,并将计算结果与粒子图像测速仪(PIV)实测结果进行比较。在对该泵叶轮内部流速分布、压力分布以及试验得到的流动撞击、二次流、回流等现象分析的基础上,提出设计上的一些改进措施,为该型泵叶轮优化设计及其内部两相流动研究提供参考。     

双流道泵内非定常流动数值模拟及粒子图像测速测量

为探讨双流道泵内部的非定常流动机理,采用Fluent软件,基于滑移网格技术、 湍流模型计算了一双流道泵在不同工况下的内部流动,并将计算结果与粒子图像测速仪(Particle image velocimeter, PIV)实测结果进行比较。结果表明：计算所得双流道泵内部流场符合叶轮机械内部流动的一般规律,且与PIV实测结果总体变化趋势一致;由于双流道泵结构特殊,其进口处的流动状态与普通叶轮相差较大,出口处的流动状态与普通叶轮类似;叶轮进口处,流体基本沿流道吸力面流动,流道工作面上的相对速度很小,存在严重的脱流和旋涡;叶轮出口处,压力面和吸力面的速度趋于相等,射流—尾迹现象并不明显;由于叶轮—蜗壳动静干涉,两个叶轮流道内的静压分布有所不同;同一流道内,静压随着半径的增加而逐步增大,压力面侧静压大于吸力面侧;蜗壳流道内静压随半径增大,最大静压值在隔舌处。此项研究不仅加深了人们对双流道泵内非定常流动图画的理解,从而进一步完善双流道泵设计方法,同时也可为其他类型泵的内流研究提供借鉴。     

应用PIV技术测量射流泵内部流场

射流泵有着广泛的应用。但对其内部流动机理认识的不足制约了射流泵的设计理论的完善，致使射流泵效率较低。本文采用PIV(粒子成像测速)技术，测量显示了射流浆内部流动发展情况，并分析了其内部流动结构。     

漂浮取水泵内部流场的数值模拟及性能试验

为了研究漂浮取水泵内部流场分布规律,基于Pro/E建立了内部流场模型,利用FLUENT对内部流场进行了数值模拟,得到了压力、速度分布规律以及外特性曲线,并结合性能试验,对数值模拟进行了验证。结果表明:漂浮取水泵存在无过载的功率曲线及高效区较宽的效率曲线;叶片旋转中心受静压较边缘低;旋转叶片速度较大;在额定流量工况下,叶轮具有较均匀的速度和流场分布规律;性能试验验证了数值模拟的正确性。研究结果为掌握泵的内部流场分布规律、改善泵的水力特性、提高泵的效率提供一定参考。     

超小型粘性泵内部流场的PIV试验研究

根据偏置于两平板间转子轴两端剪切力不平衡的原理，著者制造了本文中偏置式垂直转子轴超小型粘性泵，并利用PIV技术对其内部的流动进行了可视化量测。对采集到的数据进行了进一步的分析。得到了其内部流场的流线分布及相关性能曲线，为超小型粘性泵的性能预测及优化设计提供了初步的实验依据。     

带导流体的旋流非接触吸盘仿真及PIV实验验证

PIV(Particle Image Velocimetry)技术是一种流场可视化光学方法,经过十年的发展,该技术已经成为研究流场的基本测试手段。由于旋流非接触搬运器内部流道很小,传统的侵入式测量方法很难对搬运器内部流场进行测量。针对这个问题,该文设计了一套PIV实验测试方法,用PIV技术来获得旋流吸盘内部流场的流动规律,采用三种基本旋涡模型对旋流非接触吸盘进行一维数值建模,并且以三种数学模型为目标函数,应用最小二乘拟合方法对PIV数据进行拟合。通过比较拟合效果,辨识出了能够准确描述吸盘内部流场流动特性的数学模型。     

离心泵内部三维流场的试验研究

利用五孔球形测针仪对离心泵内部三维流场的速度、压力进行了试验研究,初步得出了内部流场主要特征和分布规律。为进一步探索泵内部三维流场的其它参数及泵的设计提供了理论依据。     

清淤泵的水力设计与内流特性

目前我国河道污染极其严重,利用清淤泵完成水力治淤是定期治理河道的有效方法之一。文中首先根据速度系数法,并结合设计经验完成了一台低比转速清淤泵的水力设计计算,获得了各个过流部件的几何参数。在此基础上,采用ASMM模型对清淤泵内部的固液两相流进行了数值计算分析,获得了初步的内部三维流动特征。该研究结果将为后续进一步优化清淤泵提供很好的依据。     

3D Particle image velocimetry test of inner flow in a double blade pump impeller

The double blade pump is widely used in sewage treatment industry,however,the research on the internal flow characteristics of the double blade pump with particle image velocimetry(PIV) technology is very little at present.To reveal inner flow characteristics in double blade pump impeller under off-design and design conditions,inner flows in a double blade pump impeller,whose specific speed is 111,are measured under the five off-design conditions and design condition by using 3D PIV test technology.In order to ensure the accuracy of the 3D PIV test,the external trigger synchronization system which makes use of fiber optic and equivalent calibration method are applied.The 3D PIV relative velocity synthesis procedure is compiled by using Visual C++ 2005.Then absolute velocity distribution and relative velocity distribution in the double blade pump impeller are obtained.Test results show that vortex exists in each condition,but the location,size and velocity of vortex core are different.Average absolute velocity value of impeller outlet increases at first,then decreases,and then increases again with increase of flow rate.Again average relative velocity values under 0.4,0.8,and 1.2 design condition are higher than that under 1.0 design condition,while under 0.6 and 1.4 design condition it is lower.Under low flow rate conditions,radial vectors of absolute velocities at impeller outlet and blade inlet near the pump shaft decrease with increase of flow rate,while that of relative velocities at the suction side near the pump shaft decreases.Radial vectors of absolute velocities and relative velocities change slightly under the two large flow rate conditions.The research results can be applied to instruct the hydraulic optimization design of double blade pumps.     

离心泵偏置短叶片叶轮内部流动的粒子图像速度测量

对三副短叶片不同偏置的低比转数复合叶轮离心泵,应用粒子图像速度仪分别测试大流量、设计流量和小流量三种工况下长短叶片叶轮同一叶槽内的瞬时流场.分析叶槽内相对速度矢量、速度等值线的特征,揭示短叶片不同偏置时的速度分布规律.研究三副长短叶片复合叶轮出口处径向速度、切向速度、相对速度和相对液流角沿圆周的分布,测得与三副叶轮相对应的泵外特性曲线.测量结果表明,分流短叶片不同偏置对叶槽内流场的影响差异明显,当短叶片进口相对出口向压力面偏转时,叶轮出口相对速度分布很不均匀,短叶片工作面出口存在较大的低速区;与之相反,当短叶片进口相对出口向吸力面偏转时,叶轮出口速度分布较均匀,并且泵的扬程与流量曲线明显右移,大流量时,效率显著提高.     

Phase discrimination and a high accuracy algorithm for PIV image processing of particle–fluid two-phase flow inside high-speed rotating centrifugal slurry pump

PIV technology is an efficient and powerful measurement method to investigate the characteristics of fluid flow field. But for PIV particle image post-processing, some problems still exit in two-phase particles discrimination and velocity field algorithm, especially for high-speed rotating centrifugal slurry pump. In this study, through summarization and comparison of the various phase discrimination methods, we proposed a two-phase identification method based on statistics of gray-scale level and particle size. The assessment of performance through experimental PIV images shows that a satisfying effect for particle identification. For high speed rotation of the impeller, a combination of adaptive cross-correlation window deformation algorithm and multistage grid subdivision is presented. The algorithm is applied to experimental PIV images of solid–liquid two-phase flow in a centrifugal slurry pump, the results show that the algorithm in the present study has less pseudo vector number and more matching particle pairs than those of fixed window and window translation methods, having the ability to remove pseudo vector efficiently. It confirmed that the algorithm proposed in the present study has good performance and reliability for PIV image processing of particle–fluid two-phase flow inside high-speed rotating centrifugal slurry pump.     

EFFECTS OF SPLITTER BLADES ON THE LAW OF INNER FLOW WITHIN CENTRIFUGAL PUMP IMPELLER

Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carried out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. New results are obtained from the analysis of turbulence kinetic energy and relative velocity distribution: Firstly, unreasonable length or deviation design of the splitter blades may cause great turbulent fluctuation in impeller channel, which has a great effect on the stability of impeller outlet flow; Secondly, it is found that the occurrence of flow separation can be decreased or delayed with splitter blades from the analysis of blade loading; Thirdly, the effect of splitter blades on reforming the structure of "jet-wake" is explained from the relative velocity distribution at different flow cross-sections, which shows the flow process in the impeller. The inner flow analysis verifies the results of performance tests results and the PIV test.     

离心泵内部流场测量系统设计及测量方法研究

离心泵是工业生产过程中的重要设备.离心泵内部流场的测量对优化泵的结构,提高泵的效率,减小泵工作时产生的噪声具有重要的意义.设计、构建了一套多功能离心泵性能试验台,该试验台能够满足泵内非定常流动非接触测量和离心泵外特性测量的需要.介绍了离心泵特性测定的方法和步骤,探讨了应用PIV(Particle Image Velocimetry)测量离心泵内部流场的关键技术及其主要试验参数的确定方法.