Experimental Research on Salt-out Particle Motion and Concentration Distribution in a Vortex Pump Volute

The vortex pump is suitable for salt solution transportation. But the salt-out flow mechanism in the pump has not been understood fully. Salt-out layer formation and growth rate are closely related to crystal particle motion and concentration distribution. Study on the particle hydrodynamic characteristics in the pump volute becomes a key problem, because the crystal particles are mainly distributing in this zone after they enter the pump. Phase Doppler particle analyzer（PDPA） is used to measure the two-phase flow field in a model pump volute to get more understanding about the salt-out phenomenon. The crystal particle velocities are obtained in all three peripheral, radial and axial directions. Particle size and particle number density（PND） measurements are also performed in the experiment. Results are presented and discussed along the radial direction under different pump operating conditions, as well as various axial measurement positions. It is found that particle velocity gradient of peripheral component varies with the pump discharge. There is a turning point of relation between peripheral velocity component and discharge. Radial flow velocity curves look like a saddle shape and velocity magnitudes are changing greatly with the discharge. The non-equilibrium velocity feature between liquid and solid phase on this direction is also remarkable. Particles flow into the impeller at radial position R〈I, and the axial velocity component increases in this region. The particle size curve shows an open-up parabola distribution. The largest particles are distributing near the casing peripheral wall. As flow rate increases, accordingly PND increases. It also grows up in the axial-outward direction towards the suction cover. Crystal particle aggregation phenomenon can be revealed from the analysis of particle size and PND distribution, and the aggregation region is determined as well. Research results are helpful for optimal design of this kind of pump preventing salt-out.

Effect of bionic mantis shrimp groove volute on vortex pump pressure pulsation

In order to reduce pressure pulsation of vortex pumps,the mantis shrimp was chosen as biological prototype and a bionic engineering model was developed from its abdominal segment grooves.Bionic mantis shrimp groove volute vortex pump models with different numbers of grooves were developed,and numerical simulation methods were used to calculate the models to study the effects of the volute grooves on the pressure pulsation of a vortex pump.The results show that a bionic groove volute could effectively improve the pressure pulsation of a vortex pump outlet,and reduce the pressure pulsation around the pump’s tongue and other internal points.The pressure pulsation under different conditions is impacted by shaft frequency and blade frequency.The bionic groove structure has little effect on the external characteristics of the pump,but could improve the static pressure,velocity distribution,and vortex structure of the flow field.Additionally,pressure pulsation of the whole vortex pump is reduced.

Investigation on the Flow Behavior of Side Channel Pumps Based on Vortex Identification

The momentum flow exchange between the impeller and side channel produces highly turbulent flows in side channel pumps.The turbulent flows feature complex patterns of vortex structures that are partly responsible for the dissipation of energy losses and unsteady pressure pulsations.The concept of turbulent flows in side channel pumps requires a reliable vortex identification criterion to capture and predict the effects of the vortex structures on the performance.For this reason,the current study presents the application of the new Ω-criterion to a side channel pump model in comparison with other traditional methods such as Qand λ2 criteria.The 3D flow fields of the pump were obtained through unsteady Reynolds-averaged Navier-Stokes(RANS)simulations.Comparative studies showed that the Ω-criterion identifies the vortex of different intensities with a standard threshold,Ω=0.52.The Q and λ2 criteria required different thresholds to capture vortex of different intensities thus leads to subjective errors.Comparing theΩ-criterion intensity on different planes with the entropy losses and pressure pulsation,the longitudinal vortex plays an important role in the momentum exchange development which increases the head performance of the pump.However,the rate of exchange is impeded by the axial and radial vortices restricted in the impeller.Therefore,the impeller generates the highest entropy loss and pressure pulsation intensities which lower the output efficiency.Finally,the findings provide a fundamental background to the morphology of the vortex structures in the turbulent flows which can be dependent upon for efficiency improvement of side channel pumps.

Design and Experiment of Streamlined Piezoelectric Pump with Low Vortex and Large Flow Rate

Valveless piezoelectric pump is widely used in the medical,however,there is a general and difficult problem to be solved:Low vortex and large flow rate are not compatible,resulting in the blood prone to thrombosis during blood delivery.In this paper,a new valveless piezoelectric(PZT)pump with streamlined flow tubes(streamlined pump)is proposed.The design method and the working principle of the pump are analyzed.The velocity streamlines are simulated,and the results demonstrate that there are no obvious vortexes in the flow tube of the streamlined pump.Five prototype pumps(two cone pumps and three streamlined pumps)are designed and fabricated to perform flow rate and flow resistance experiments.The experimental results illustrate that the maximum flow rate of the streamlined pump is 142 mL/min,which is 179%higher than that of the cone piezoelectric pump,demonstrating that the streamlined pump has a large flow rate performance.This research provides an inspiration for future research on simple structure,low vortex and large flow rate volume-type pumps,and also provides a useful solution for thrombosis preventing.

Experimental study on inlet vortex in pump sump

In order to study the mechanism of the vortex generation at the bottom of the pump sump below the flare tube,twenty pressure pulsation monitoring points were arranged at the bottom of the pump sump below the flare tube,and the pressure fluctuation experiments were carried out under different flow conditions.The experimental results show that the frequency of pressure fluctuation at the bottom of the pump sump is twice of the rotational frequency of the impeller blade.The vortex below the flare tube is easy to generate under the large flow conditions and mainly concentrates at the right front position below the flare tube.The position of the vortex occurring is corresponding to the position of the low-pressure region below flare tube.

Effect of tongue clearance on hydraulic performance of double support vortex pump

In order to study influence of tongue clearance on the hydraulic performance of double support vortex pump,three dimensional flow model with symmetric variable size tongue clearance was established by changing section parameter of tongue clearance,and applied to numerically simulate the steady inner flow in a vortex pump based on fixed working conditions and impeller through ANSYS FLUENT.The numerical results show the influence of tongue channel with two sections(non-uniform and uniform sections)on flow field characteristics in vortex pump.Firstly,the variation of tongue channel section changes the vortex structure distribution in circumferential flow channel.Specifically the spiral forward vortex structure in the circumferential direction shifts to large radius side with increasing tongue width.Secondly,the circumferential velocity gradient and axial pressure gradient both diminish with the increase of the tongue section,and the inlet/outlet pressure difference and velocity distribution also reduce with increasing tongue channel section.Finally,for vortex pump with non-uniform section of tongue channel,the head diminishes and the efficiency remains constant approximately with the increase of the tongue width,while the head and the efficiency both diminish for uniform section of tongue channel.

水泵水轮机尾水管压力脉动特性及涡带特性分析

抽蓄电站是电网的重要组成部分,水泵水轮机长时间偏离最优工况运行会导致水力不稳定问题,其中,尾水管涡带和压力脉动问题备受关注,严重影响机组安全稳定运行。以水泵水轮机为研究对象,分析了其尾水管内流特性与压力脉动时频特性。对比了两种第二代和两种第三代涡识别方法对尾水管涡带演化过程的可视化效果,Omega-Liutex涡识别方法对阈值依赖性小且对涡带形态的识别更清晰完备,因此,采用Omega-Liutex涡识别方法研究了不同负荷工况下尾水管涡带的瞬态变化特性。研究结果可以为水泵水轮机稳定运行提供一定的理论参考。

基于熵产理论的管道泵流动损失特性分析

为了揭示管道泵运行过程中的流动损失特性,基于熵产理论,采用数值计算方法对管道泵吸水室和叶轮内的总熵产以及局部熵产率进行了研究,并结合压力脉动及涡核分布对其产生流动损失的原因进行了分析。研究结果表明,叶轮总熵产和吸水室总熵产保持高度一致性,吸水室内部流动影响了叶轮内部流动。随着流量的增大,叶轮和吸水室总熵产先减小,随后增大,这与其内部监测点的压力脉动主频幅值变化规律基本一致。叶轮总熵产显著大于吸水室总熵产,偏工况下更为明显,前者至少是后者的4倍。湍流耗散熵产占据吸水室和叶轮总熵产的90%以上,构成了流动损失的主要部分。吸水室高熵产率区主要分布在第二弯道及出口处,小流量工况下的熵产率是其余工况下的数百倍,该位置的大尺度带核涡以及附壁涡是导致熵产率增加的主要原因。叶轮高熵产率区主要集中在叶轮进口和出口,在大部分区域,小流量下的熵产率是其余工况的6倍以上,小流量工况下叶轮进口预旋和出口失速涡以及大流量工况下叶轮中上游的分离涡是导致熵产率较高的主要原因。该研究可为管道泵局部流动损失识别以及开展针对性优化提供参考。

气液两相条件下叶片开孔对电潜泵性能和内部流场的影响

为了研究电潜泵内部流动机理,从而改善高含气工况下电潜泵的气液混输性能,文中基于欧拉-欧拉非均相流模型,对不同入口含气率工况下叶片开孔前后的气液两相流动特性进行了数值模拟分析,探究了气液两相流条件下叶片开孔对电潜泵性能和内部流场的影响.结果表明,在纯水工况以及低含气率、小流量工况下,叶片开孔会降低电潜泵性能;但是叶片开孔可以改善电潜泵在大流量下的气液混输性能.叶片开孔后会改变叶轮内部压力分布,使电潜泵叶轮内部平均压力升高,进而改善叶轮内部流态.叶片开孔后会冲散气相聚集,使气体分布更加均匀,叶轮流道内涡核分布明显减少,减少了能量耗散.该研究为改善电潜泵气液混输性能提供了理论依据.

空化诱导的离心泵叶轮区流动特性与压力脉动分析

空化是一种复杂的多相流现象,空化发展中液体和蒸汽之间瞬态相变的产生,导致多尺度旋涡运动。瞬态空化动力学与空化涡结构的演化密切相关。采用对比结合Q准则、Omega判别法两种涡识别方法,探究设计流量Qd为0.321 m3/s下不同空化程度时离心泵叶轮区的空泡、涡旋特性及其对压力脉动的影响。基于Schnerr-Sauer空化模型对立式单级单吸蜗壳式离心泵在空化初始阶段、空化发展阶段、空化状态转变阶段、空化恶化阶段4个不同空化程度时的全流道流场进行数值模拟分析。结果表明,空化情况下叶轮区域流动复杂,空泡形态与旋涡的生成变化相互影响,二者共同影响叶轮域内压力脉动的变化。Omega方法能够精准捕捉到叶轮进口的回流涡、叶轮流道内通道涡和叶轮尾缘处的尾迹涡;空化初期,受通道内大面积通道涡及蜗壳隔舌动静干涉的影响,出现各叶片上空泡大小不同的情况;空化严重时受空泡脱落影响出现气液混合的高速涡团,导致低频压力脉动信号增加,空泡移动至高压区溃灭释放的能量导致出口压力脉动显著升高。

空间导叶式多级离心泵级间能量损失机理

为探究空间导叶式多级离心泵级间能量损失的原因,以1个单级和1个3级潜水泵为研究对象,通过试验和数值模拟相结合的方法,分析其级间能量损失的机理.对单级和3级潜水泵分别进行全流场外特性试验.基于ANSYS软件对3级潜水泵不同流量点进行数值模拟和内流场分析,着重对各级叶轮进口流态、内部旋涡结构和叶片载荷分析比较.结果表明:小流量工况下,3级潜水泵各级扬程接近且与单级扬程相差不大;额定流量工况和大流量工况下,3级潜水泵第1级扬程与单级扬程仍相差不大,但后2级扬程相比于第1级降低了6%~10%.随着流量的增大,首级叶轮来流稳定性不受影响,其后各级叶轮进流流态变差.后2级叶轮进口液体介质冲角变化使其对叶片进口边的冲击增大.后2级叶轮进口处的涡在流量较大时发展为流向涡,从而引起叶片载荷突变,削弱了叶轮做功能力,导致后2级能量损失.研究结果可为多级离心泵的设计提供理论依据.

旋流泵叶轮流道固液两相流动不稳定性分析

由于结构的特殊性以及固液两相存在的密度差,旋流泵在输送固液两相介质过程中,内部会出现多方面的不稳定性特征,基于Particle模型,运用ANSYS CFX软件对额定转速下旋流泵在不同流量下输送不同固相体积分数的多种工况进行了非定常数值模拟,分析了叶轮流道内的固相分布、压力脉动和叶轮径向力,从而深入了解叶轮内部不稳定性。结果表明:在C_(v)=5%体积分数下,0.8 Q_(d)、1.0 Q_(d)流量下叶轮流道内固相体积分布均匀,1.2 Q_(d)分布不均匀;在C_(v)=10%体积分数下,0.8 Q_(d)流量下分布均匀,1.0 Q_(d)和1.2 Q_(d)流量下分布不均匀;在C_(v)=20%体积分数下,0.8 Q_(d)、1.2 Q_(d)流量下分布均匀,1.0 Q_(d)分布不均匀;在C_(v)=20%、1.0 Q_(d)工况的一个旋转周期内,叶轮内部始终存在一个条形固相分布区域,且其旋转速度滞后于叶轮旋转速度。在1.0 Q_(d)流量下,随着固相体积分数的增加,各监测点压力系数幅值波动逐步变大;后缩腔监测点叶频处的幅值基本不变,叶轮流道内监测点轴频处的幅值逐步变大;在C_(v)=20%体积分数下,随着流量的增加,各监测点压力系数幅值波动先增后减,后缩腔监测点叶频处幅值逐步增大,流道内监测点轴频处的幅值先增后减。相同固相体积分数下,随着流量的增加,径向力逐步增大;不同固相体积分数下,随着体积分数的增加,0.8 Q_(d)流量下径向力波动不大,1.0 Q_(d)流量下波动逐步变大,1.2 Q_(d)流量下波动逐步变小。

贯流泵站前池表面涡数值预测与分析

贯流泵站因其流道水力损失小,装置效率高的优点在灌溉、调水和排水等领域应用广泛,受水位、工况等影响,泵站前池常出现表面漩涡等不良现象,影响泵站效率及稳定性。以淮安三站灯泡式贯流泵站为研究对象,通过计算流体动力学数值模拟了泵站进水流道和前池,采用BM模型捕捉表面涡的旋转特性,采用S-CLSVOF跟踪自由表面,研究了设计工况下贯流泵站的内部的流动规律和表面涡的发展,结果表明:淹没深度越大,表面涡越弱,但水面的波动更强;表面涡的出现将使进水流道流速均匀性降低。研究结果为大中型贯流泵站吸气涡的数值模拟提供理论参考。

空化对尾水管区域驼峰特性影响研究

为了研究水泵水轮机空化对驼峰特性的影响,采用SST k-ω湍流模型和Z-wart空化模型对全流道进行了三维定常数值模拟计算,并分析了不同工况点下尾水管在驼峰区域的水力性能和内部流动状态。研究结果表明,不同工况点下,流量大小会改变尾水管区域液流的流动方向,从而产生偏心涡带使尾水管区域出现不稳定性,造成机组振动和噪声;单相计算结果比空化计算结果更早受到剪切流的影响。来流与壁面射流相互作用产生漩涡,出现回流现象。在速度梯度变化方面,空化计算结果的速度值要比单相的值高,能量损失有所增加。

阀板尾迹对离心泵性能的影响

离心泵进水管路通常布置阀门供检修时切断水流,这会导致离心泵入流畸变。该研究旨在分析泵前检修阀所诱发的非定常尾迹特征及其对大流量工况离心泵运行特性的影响机理。试验对比了均匀来流和畸变来流条件下离心泵的外特性,数值模拟研究了阀板尾迹涡的流动特征及其对离心泵非稳态内流场的影响,分析了阀板尾迹涡诱发的叶轮径向力。结果表明:两种来流条件下数值模拟与试验得到的离心泵外特性误差在5%以内;对离心泵性能产生主要影响的尾迹涡主要来自阀门阀板一侧的边界层分离与卷吸,入流畸变导致大流量工况下离心泵效率相较于均匀入流下降9.15%,扬程降低1.2 m;阀板尾迹在离心泵入口产生1.9倍转频的脉动频率;尾迹涡的周期性入流导致两个叶片前缘的最大相对液流角由30°分别增大至43°和39°,这两个叶片的压力面脱流加剧,产生逐渐向下游耗散的失速团,叶片承受2倍转频的非稳态激振力;尾迹涡的周期性吸入导致叶轮上的时均径向力增大至均匀入流的4.5倍左右,最大径向力达到均匀入流的7倍左右,径向力矢量发生偏移,离心泵断轴风险加剧。研究结果可为工业现场中离心泵运行稳定性的改善提供理论依据。

基于光泵效应诱导涡旋光的通断控制实验教学设计

随着对涡旋光研究的深入,对涡旋光在各种介质中的传输控制提出了更高的要求。本实验利用光泵效应在三能级热源子系统中完成了对涡旋光传输通断的控制,通过分别控制信号光的失谐程度、泵浦光的光功率大小以及铷原子气体池的温度高低等参数来调控信号光的传输透过率,从而实现对涡旋光传输的通断控制。本文将理论与实验相结合,使学生通过实验更加充分地理解理论知识,培养和提高了学生的实践能力和创新意识。

水泵水轮机S特性区能量损失及流动特性研究

为了调节电网的稳定性,抽水蓄能电站需要频繁启停和变换工况运行,导致水泵水轮机容易进入S特性区,机组振动增加,并网失败。本文以模型水泵水轮机为研究对象,采用熵产理论详细分析了S特性区不同工况下的能量损失规律,明确了熵产率分布与内部流动结构的关系。结果表明:S特性区内近飞逸工况总熵产最大,约为设计工况的5.1倍,脉动熵产占据的比例接近80%,随着流量的减小,转轮熵产占比逐渐降低,活动导叶和尾水管的熵产占比增加。小流量工况转轮进口靠近下环位置首先出现了明显的漩涡,导致了活动导叶出口和转轮进口的高熵产区,随着流量进一步减小,漩涡逐渐向上冠转移,并且切向速度增大,在转轮进口形成挡水环,阻碍水流进入转轮,在无叶区内出现了环状分布的高熵产区。反水泵工况,水流在低压边与逆时针旋转的叶片撞击,导致水流很难进入叶片内部,形成了大尺度的回流涡结构;双列叶栅内充满大量涡结构,导致活动导叶吸力面的熵产率增大,并且向固定导叶传播。

内回流槽结构对罗茨泵内部流动特性的影响

针对罗茨泵工作时排气口气体压力高、基元容积内压力低以及气体回流引起出口气流脉动大等问题,应用Pumplinx对MB7300型罗茨泵进行全流场数值计算,通过Tecplot软件并采用Q准则对罗茨泵内流场涡结构进行定性分析,研究内回流槽厚度和角度2个关键参数对罗茨泵内部流动的影响规律,尤其对出口压力脉动和流量脉动的影响.研究结果表明:内回流槽结构对进口侧流态改善效果不明显,但可以很好地降低排气压力脉动、流量脉动以及排气段涡流,内回流槽厚度越大,角度越大,效果越明显;内回流槽厚度、角度增大过大时,转子与机壳之间间隙增大,泄漏量增多,排气量降低幅度大幅升高;内回流槽厚度和角度存在较为优选的组合,在有效降低压力和流量脉动的同时,可最大限度降低流量的损失,综合考虑流量和出口脉动性能时,内回流槽角度约为45°,厚度约为7.5 mm时组合效果较好;如果使出口流量不出现负值,内置回流槽的尺寸应选择角度45°~60°,厚度7.5~10.0 mm.研究结果可为罗茨泵气流脉动和壳体结构优化设计提供一定依据.

含沙条件下泵站进水池控涡技术研究

含沙水流会对沿黄泵站造成严重的磨损破坏。泵站进水池漩涡的存在将会加重水泵磨损,严重影响水泵的运行寿命。为探究含沙条件下泵站进水池控涡技术,基于仿生学原理研发了一种带波状前缘翼型喇叭口的消涡装置,并通过模型试验,在清水和含沙水两种环境下,研究波状前缘翼型喇叭口对进水池内漩涡的影响特性。结果表明:无论在清水还是含沙水条件下,波状前缘翼型喇叭口均能有效抑制附底涡的产生、降低附底涡的出现频率、减小进水管内水流的预旋强度,有利于改善水泵的进水流态,防止泥沙磨损的进一步加剧。

基于涡分析的旋涡泵内流动能量转换特性研究

为研究旋涡泵内复杂的旋涡特征,量化泵内旋涡体积和强度,分析旋涡结构对能量转换和能量损失的影响规律,采用非定常数值模拟和外特性实验相结合的方法对单级旋涡泵进行分析,综合使用Ω方法和Liutex方法对泵内旋涡进行识别和强度表征,提出平均旋涡强度进行量化研究,并结合动能方程的涡动力学分解式以及涡量分解理论进行分析。结果表明:泵内的旋涡充分发展区域存在螺旋形的管状旋涡结构,该旋涡从叶轮流道流出进入侧流道,并且随着流量的增大,涡管数量减少且旋涡强度降低;流量的增大使得叶轮内的旋涡体积和强度减小,而其在侧流道内相对变化较小,相同工况时叶轮内的平均旋涡强度远大于侧流道内;压力梯度对流体动能转换的贡献最大,旋涡结构引起的动量输运和耗散损失占比较小,但刚性涡量即旋涡结构的强度与动量输运呈正相关,变形涡量则与拟涡能损失相关性较强。