旋流泵内盐析两相流场的计算及试验研究

为研究流体机械内部伴有盐析的液固两相流动情况,自行设计了旋流式模型泵,采用双流体模型计算了该泵在最优工况下的氯化钠盐析两相流场,并采用先进的激光相位多普勒粒子测速仪测量了泵无叶腔及叶轮内部盐析两相流的三维速度场。将试验结果与计算结果进行对比,验证了计算模型的适用性,并给出了误差分析。通过对试验测得的周向、轴向、径向速度及其对应的脉动速度分布曲线讨论,初步揭示了该型泵内盐析两相流动特征。在整个流道内,盐析晶体颗粒大部分集中于无叶腔,且分布较均匀;进入叶轮后向叶片工作面靠拢;颗粒浓度最低处是在叶轮进口叶片背面靠近叶轮后盖板附近;液固两相在叶轮与无叶腔中的周向速度分布差异明显;两相间速度及脉动速度有滑移,但差异总体上并不显著。     

基于几何光学的图像矫正法在圆管PIV实验中的应用研究

粒子图像速度技术被广泛用于流体流动测量,介质折射率差异使光在圆管壁面发生偏折,导致图像失真,直接影响速度测量精度。本文建立了光学折射的物理模型,得到圆形管道中物点和图像点之间的函数关系进而得到矫正后图像的像素坐标,使用双线性插值算法得到像素灰度值重建出矫正后的粒子图像,最后根据多重网格迭代算法计算管内速度场。分别对流体进行管内静态流体与管内层流速度场测量实验,对比了光学矫正箱法、线性矫正以及基于光学模型的畸变矫正方法误差。结果表明,本文提出的基于几何光学的图像矫正方法精度优于光学矫正箱法和线性矫正方法,并通过静态与流动实验充分验证了所建立几何光学模型的准确性和有效性。     

聚合物稀溶液对同心旋转圆柱间层流失稳的影响

根据有效粘度模型，利用原始变量法计算了聚合物稀溶液对无限长同心旋转间流体流动层流失稳的影响。讨论了不同浓度的聚氧化乙烯（ Ｐｏｌｙｏｘ Ｗ Ｓ Ｒ３０１）水溶液对临界 Ｔａｙｌｏｒ数以及速度场的影响。计算结果表明，聚合物稀溶液减缓了扰动速度的增长，能有效地抑制流体的层流失稳。     

化工泵叶轮内部固液两相流场的研究

为了研究化工泵叶轮内部伴有盐析的固液两相流动,本文利用先进的流场测试仪器PIV（粒子成像测速仪）对改型后的化工泵叶轮内部流场进行测量,并编写了图像处理软件,用来区分流场中固液两相,分别对固液两相进行互相关算处理后得到固液两相的速度场,实验结果发现固体颗粒具有向压力面移动的趋势,这与数值模拟的结果一致。     

变速搅拌混沌混合的PIV试验研究

针对搅拌槽内部的流体混合在湍流状态不成问题,但当流体处于层流状态下如何提高混合效率的实际问题,为提高层流状态下搅拌槽内流体的混合效率,采用混沌混合使叶轮以变转速做周期性运动。利用粒子图像测速技术对层流搅拌槽变速混沌混合流场进行试验研究,对所测得的粒子图像采用相应图像处理软件处理,得到了六个不同角度处流体径向速度分布云图,并对比分析变速搅拌与常速搅拌混合流场速度分布曲线的不同。试验结果表明,叶轮变转速运动时,搅拌槽内径向速度范围宽,扰动区域大,说明变转速运动比常转速运动的搅拌混合效果好、搅拌效率高。所做研究对充分认识变速层流搅拌诱发混沌混合的机理,为大型层流混沌混合搅拌槽的设计提供指导性建议,具有重要理论意义及实际应用价值。     

PDA在炉膛气固两相流动特性研究中的应用

介绍了激光相位多普勒粒子动态分析仪(PDA)的测量原理,对冷态模化的炉膛再燃区域气固两相流场的速度和粒子粒径、浓度进行了测量,研究了炉膛主燃区过量空气系数在0.9时的再燃区的气固两相湍流流场的动力特性,分析了气固两相的速度分布、速度滑移以及颗粒数密度的分布规律,结果表明主燃区过量空气系数0.9时再燃区的气固两相流动及混合特性有利于形成均匀的还原场.     

电磁感应原理在检测分析仪表中的应用——日本DKK公司无电极电导率计及无电极酸碱盐浓度计

本文介绍了日本 DKK公司利用电磁感应原理制造的无电极电导率计及无电极酸碱盐浓度计。本文列出了 H2 SO4 、HNO3、HCL、Na OH、Na Cl溶液浓度对电导率的二维相关曲线 ;H2 SO4 溶液浓度对电导率和温度的三维相关曲面 ;以及 DKK公司无电极酸碱盐浓度计与其他公司同类产品浓度测量范围比较表     

多出口管内层流稳态流动温度场数值仿真分析

研究多出口圆管稳态层流流动对发展热对流理论具有重要意义。以液态饱和水为流动工质,通过数值仿真的方法研究了具有支流出口的圆管稳态层流流动温度场分布,通过三个典型工况的模拟计算并与试验结果对比表明,仿真模型和试验解最大误差在2.2%以内,证明了数值模型的正确性,为后续验证新热对流理论模型奠定了基础。同时也对支流出口开启和关闭时对主流出口温度场、速度场和管内流场的影响进行了定量分析和对比。     

增加算子扰动项的粒子群优化算法研究

为了提高粒子群算法的稳定性,改善陷入局部最优的弊端,提出了一种增加算子扰动且对惯性权重进行正弦调整的粒子群优化算法。该方法首先利用差分方程对粒子的速度与位置变化过程进行深入分析,然后找到粒子群算法收敛的约束条件,进而获得改进后的惯性权重。最后在粒子群算法的速度公式中引入算子扰动项,其对粒子施加扰动,能够有效的抑制算法陷入局部最优问题,使算法在迭代后期也拥有一定的搜索能力。利用4个典型测试函数对算法进行验证,实验结果表明改进的惯性权重及速度更新公式使得该算法具备了较快的收敛速度和较佳的全局收敛性能,与标准粒子群算法相比,改进后的粒子群算法收敛精度高、鲁棒性强。     

混流式水轮机尾水管内部流场的PIV测试

以混流式水轮机尾水管为研究对象,设计构建了用于内部流场激光测量的模型水轮机尾水管试验台,对粒子图像测速仪(Particle image velocimetry,PIV)技术测量水轮机尾水管内部流动的应用进行了实践。试验尾水管测试面由透明的有机材料制成,分别测试了在不同导叶开度下混流式水轮机尾水管的锥管段、肘管段出口、扩散段进出口不同测试位置上的瞬时速度,再通过时均处理,给出了速度、涡量及流线分布。在本试验条件下观察到锥管段内存在着与中心线垂直断面上的环形流动和小开度时子午面内的回流,肘管段和扩散段内产生了二次流,以及扩散段左右部分的流动不对称等现象。试验测量结果不仅加深了对尾水管内流动的理解,同时也为校验数值模拟结果提供了试验基础数据。     

A modified cross-correlation algorithm for PIV image processing of particle-fluid two-phase flow

PIV (Particle Image Velocimetry) technique for flow field measurement has achieved popular self-identify through over ten years development, and its application range is becoming wider and wider. PIV post-processing techniques have a great influence on the success of particle-fluid two-phase flow field measurement and thus become a hot and difficult topic. In the present study, a Phase Respective Identification Algorithm (PRIA) is introduced to separate low-density solid particles or bubbles and high-density tracer particles from the PIV image of particle-fluid two-phase flow. PTV (Particle Tracking Velocimetry) technique is employed to calculate the velocity fields of low-density solid particles or bubbles. For the velocity fields of high-density solid particles or bubble phase and continuous phase traced by high-density smaller particles, based on the thought of wavelet transform and multi-resolution analysis and the theory of cross-correlation of image, a delaminated processing algorithm (MCCWM) is presented to conquer the limitation of conventional Fourier transform. The algorithm is firstly testified on synthetic two-phase flows, such as uniform steady flow, shearing flow and rotating flow, and the computational results from the simulated particle images are in reasonable agreement with the given simulated data. The algorithm is then applied to images of actual bubble-liquid two-phase flow and jet flow, and the results also confirmed that the algorithm proposed in the present study has good performance and reliability for post-processing PIV images of particle-fluid two-phase flow.     

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.     

Review of certain key issues in indirect measurements of the mass flow rate of solids in pneumatic conveying pipelines

On-line mass flow measurement of particulate solids in pneumatic conveying pipeline is a technically challenging area, where mass flow measurement presents a range of problems. These problems are not normally relevant to a single phase flow, but are always involved in gas–solids two-phase flows, like inhomogeneous distribution of solids over the pipe cross section, irregular velocity profiles, variations in particle size, moisture content, and deposition of fine particles on the inner wall of the pipeline. These variables may affect the response of a solids flow meter in ill-defined ways. All of these make the design and the calibration of solids’ mass flowmeter more difficult. Based on a review of non-invasive mass flow measurements of particulate solids, this paper summarizes and highlights several key issues, which often rely on structures of sensors or measurement methods, in indirect mass flow metering of pneumatically conveyed solids. They are: (i) spatial filtering effect; (ii) averaging effect; (iii) measurement resolution and sensitivity of array structures in tomography sensors.     

耐磨气固两相流离心风机的理论研究与开发

分析了气固两相流风机的使用背景和存在的问题，通过对固粒穿过湍流和层流边界层时造成叶片磨损的比较，建立了风机叶片附近流场特性与磨损之间的关系，说明叶片附近流场的湍化程度高能减轻固粒对叶片的磨损，而由计算表明叶片表面加肋条能提高流场的湍化程度，因而能减轻磨损。在理论研究的基础上，通过固粒对壁面的冲击角与冲击速度对磨损率影响的实验研究，设计了耐磨风机，经实际运行，耐磨效果很好。     

气固两相管道输送分支流动阻力特性的研究

在水平T型分支管道中用压缩宅气对平均粒径为0．5mm砂石进行了气力输送试验,对气固两相分支管道输送的阻力性能进行了研究。试验结果表明,在发送压力基本保持不变的情况下,当输送气速下降时各分支管的单位长度压差在开始时逐渐减小;但当气速下降到一定程度后,单位长度压差下降趋势减缓,其中局部阻力相对较大的分支管路则开始增大。当分支管流量控制阀开度差值由小变大时,两分支管各自的压差曲线逐渐远离,局部阻力较大的分支管路的临界速度增大。     

Measurement of vertical oil-in-water two-phase flow using dual-modality ERT–EMF system

Oil-in-water two-phase flows are often encountered in the upstream petroleum industry. The measurement of phase flow rates is of particular importance for managing oil production and water disposal and/or water reinjection. The complexity of oil-in-water flow structures creates a challenge to flow measurement. This paper proposes a new method of two-phase flow metering, which is based on the use of dual-modality system and multidimensional data fusion. The Electrical Resistance Tomography system (ERT) is used in combination with a commercial off-the-shelf Electromagnetic Flow meter (EMF) to measure the volumetric flow rate of each constituent phase. The water flow rate is determined from the EMF with an input of the mean oil-fraction measured by the ERT. The dispersed oil-phase flow rate is determined from the mean oil-fraction and the mean oil velocity measured by the ERT cross-correlation velocity profiling. Experiments were carried out on a vertical upward oil-in-water pipe flow, 50 mm inner-diameter test section, at different total liquid flow rates covering the range of 8–16 m³/hr. The oil and water flow rate measurements obtained from the ERT and the EMF are compared to their respective references. The accuracy of these measurements is discussed and the capability of the measurement system is assessed.     

Application of dual-plane ERT system and cross-correlation technique to measure gas–liquid flows in vertical upward pipe

The progress of process tomography provides a new method for two-phase flow measurement. The dual-plane electrical resistance tomography (ERT) is combined with the correlation measurement technique to carry out the two-phase flow measurement in which the continuous phase is conductive liquid. The method of the estimation of void fraction and the disperse phase velocity by extracting the eigenvalue of the dual-plane ERT boundary measured data is presented. This method is applied to the transient flow-rate measurement of the air–water two-phase flow in vertical pipe. The information of disperse phase void fraction and distribution variation with time change can be considered adequately, and the estimated value of disperse phase void fraction and velocity can be gained fairly accurately in this method, which provides the data for the calculation of the transient flow-rate. The experiment results indicate that this kind of measurement method is valid when the distance between the upstream and downstream measured cross section is short enough.     

A system to estimate coarse particle velocities at the pipe wall in settling slurry flow

Understanding and modelling of coarse particle (settling) slurries in laminar flow in pipes is still not complete. Better analytical procedures will enable more efficient pipeline operation which could result in significant power savings in the transport of coarse materials. The depth and velocity of the settled bed significantly affect the pressure gradients required to pump these slurries and knowledge of these parameters is of importance. Existing measurement techniques that can be used for monitoring of these complex fluid systems are either very expensive, not easy to implement or mostly used under controlled laboratory conditions. A new measurement system was developed that is capable of detecting the deposition of solids, the depth of a settled bed and the velocity of coarse particles at the pipe wall, around the pipe circumference. Particle velocities were determined by cross-correlating modulated signals from pairs of electrodes mounted flush with the pipe wall, in contact with the slurry. Tests were conducted using a mixture of acetal beads in water, at bulk velocities between 0.5 and 4 m/s. Estimated particle velocities from the cross-correlation analyses were compared with those obtained using a 30 fps video camera combined with visual inspection, and found to be within ±6%, thus validating the viability of the system. Particle velocity resolution using the cross-correlation technique is limited by block size, sample rate and the measurement distance between electrode pairs. Further test work with a range of real slurries (different particle sizes, solids concentrations and rheologies) needs to be conducted, along with more extensive verification of the results, to establish the limits of the system. Initial testing and evaluation of the system, which is capable of coarse particle flow monitoring in real time, showed significant potential for development of a new commercial sliding bed detector that can be used in a wide range of industrial applications in which particles are transported hydraulically.     

Analytical investigation of an inductive flow sensor with arc-shaped electrodes for water velocity measurement in two-phase flows

An inductive flow sensor with spot-shaped electrodes (IFS-SE) is sensitive to the shape of the flow profile and is restricted to be used to measure the flow rate of axisymmetric single-phase flows in a circular pipe. In many cases of application, it is not possible to provide a fully developed flow profile. Therefore, the inductive flow sensor has to cope with flow profiles that are not fully developed. To improve the accuracy, an inductive flow sensor with a pair of arc-shaped electrodes flush-mounted on the internal surface of an insulating section of a pipe is proposed in this article to investigate the characteristics of vertical gas-water two-phase flows. The effect of the flow profile on the inductive flow sensor is analyzed. A key contribution of the present work is to estimate the relationship between the induced voltage and the velocity of the conductive phase in two-phase flows. The estimation is achieved by the analytical calculation of magnetic-inductive equations through the method of variables separation. The analytical solution is compared with the results from an ideal model and from numerical simulation. Experiments are conducted to calibrate the inductive flow sensor with arc-shaped electrodes (IFS-AE). It is noted that the proposed IFS-AE can be adopted to obtain the velocity of the conductive phase in two-phase flows by measuring the voltage induced on the arc-shaped electrodes.