Numerical Simulation and Analysis of Solid-liquid Two-phase Flow in Centrifugal Pump

The flow with solid-liquid two-phase media inside centrifugal pumps is very complicated and the relevant method for the hydraulic design is still immature so far. There exist two main problems in the operation of the two-phase flow pumps, i.e., low overall efficiency and severe abrasion. In this study, the three-dimensional, steady, incompressible, and turbulent solid-liquid two-phase flows in a low-specific-speed centrifugal pump are numerically simulated and analyzed by using a computational fluid dynamics （CFD） code based on the mixture model of the two-phase flow and the RNG k-~ two-equation turbulence model, in which the influences of rotation and curvature are fully taken into account. The coupling between impeller and volute is implemented by means of the frozen rotor method. The simulation results predicted indicate that the solid phase properties in two-phase flow, especially the concentration, the particle diameter and the density, have strong effects on the hydraulic performance of the pump. Both the pump head and the efficiency are reduced with increasing particle diameter or concentration. However, the effect of particle density on the performance is relatively minor. An obvious jet-wake flow structure is presented near the volute tongue and becomes more remarkable with increasing solid phase concentration. The suction side of the blade is subject to much more severe abrasion than the pressure side. The obtained results preliminarily reveal the characteristics of solid-liquid two-phase flow in the centrifugal pump, and are helpful for improvement and empirical correction in the hydraulic design of centrifugal pumps.

Computational Analysis of Centrifugal Pump Delivering Solid-liquid Two-phase Flow during Startup Period

The transient behavior of centrifugal pumps during transient operating periods, such as startup and stopping, has drawn more and more attention recently because of urgent needs in engineering. Up to now, almost all the existing studies on this behavior are limited to using water as working fluid. The study on the transient behavior related to solid-liquid two-phase flow has not been seen yet. In order to explore the transient characteristics of a high specific-speed centrifugal pump during startup period delivering the pure water and solid-liquid two-phase flow, the transient flows inside the pump are numerically simulated using the dynamic mesh method. The variable rotational speed and flow rate with time obtained from experiment are best fitted as the function of time, and are written into computational fluid dynamics （CFD） code-FLUENT by using a user defined function. The predicted heads are compared with experimental results when pumping pure water. The results show that the difference in the transient performance during startup period is very obvious between water and solid-liquid two-phase flow during the later stage of startup process. Moreover, the time for the solid-liquid two-phase flow to achieve a stable condition is longer than that for water. The solid-liquid two-phase flow results in a higher impeller shaft power, a larger dynamic reaction force, a more violent fluctuation in pressure and a reduced stable pressure rise comparing with water. The research may be useful to tmderstanding on the transient behavior of a centrifugal pump under a solid-liquid two-phase flow during startup period.

Numerical simulation and analysis of solid-liquid two-phase threedimensional unsteady flow in centrifugal slurry pump

Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.

Numerical Simulation and Experimental Research on the Influence of Solid-phase Characteristics on Centrifugal Pump Performance

The law governing the movement of particles in the centrifugal pump channel is complicated; thus, it is difficult to examine the solid-liquid two-phase turbulent flow in the pump. Consequently, the solid-liquid two-phase pump is designed based only on the unary theory. However, the obvious variety of centrifugal-pump internal flow appears because of the existence of solid phase, thus changing pump performance. Therefore, it is necessary to establish the flow characteristics of the solid-liquid two-phase pump. In the current paper, two-phase numerical simulation and centrifugal pump performance tests are carried out using different solid-particle diameters and two-phase mixture concentration conditions. Inner flow features are revealed by comparing the simulated and experimental results. The comparing results indicate that the influence of the solid-phase characteristics on centrifugal-pump performance is small when the flow rate is low, specifically when it is less than 2 m3/h. The maximum efficiency declines, and the best efficiency point tends toward the low flow-rate direction along with increasing solid-particle diameter and volume fraction, leading to reduced pump steady efficient range. The variation tendency of the pump head is basically consistent with that of the efficiency. The efficiency and head values of the two-phase mixture transportation are even larger than those of pure-water transportation under smaller particle diameter and volume fraction conditions at the low-flow-rate region. The change of the particle volume fraction has a greater effect on the pump performance than the change in the particle diameter. The experimental values are totally smaller than the simulated values. This research provides the theoretical foundation for the optimal design of centrifugal pump.

Theoretical analysis of effect of solid phase on cavitation performance of deep-sea mining pump

In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq.(19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline.

Influence on the Solid−Liquid Two-Phase Flow from Cross-Section Area of Slurry Pumps for Deep-Sea Mining

To explore the mechanism of solid-liquid two-phase flow in deep-sea mining pumps,this paper investigates the influences of the impeller cross-section area on the multi-phase flow in the slurry pump.Experimental and numerical results are presented for two-phase flow in four impellers with different cross-section areas.They show that the degree of vortex strength and the passing capacity of particles increase as the cross-section area of the impeller.In addition,the correlations between the two-phase flow and cross-section area have been revealed by a mathematical model taking the force of the flow field into account.The simulation results confirm the theoretical analysis,while the experimental pump performances validate the numerical calculation.The influence of the cross-section area on two-phase flow and pump performance could provide theoretical support for the design of high-performance deep-sea mining slurry pumps.

Effects of Particle Concentration on the Dynamics of a Single-Channel Sewage Pump under Low-Flow-Rate Conditions

Single-channel sewage pumps are generally used to transport solid-liquid two-phase media consisting of a fluid and solid particles due to the good non-clogging property of such devices.However,the non-axisymmetric structure of the impeller of this type of pumps generally induces flow asymmetry,oscillatory outflow during operations,and hydraulic imbalance.In severe cases,these effects can jeopardize the safety and stability of the overall pump.In the present study,such a problem is investigated in the framework of a Mixture multiphase flow method coupled with a RNG turbulence model used to determine the structure of the flow field and the related motion of transported particles.It is shown that under different inlet particle concentrations,the flow field in the pump exhibits periodic variations of the pressure.The volume fraction of solid particles at the trailing edge of the suction surface of the blade is the largest,and solid particles tend to be concentrated at the outer edge of the pump body.With a rise in import particle content,the pressure and volume fraction of particles in the sewage pump also increase;for a fixed inlet particle concentration,the pressure pulsation amplitude increases with an increase in the flow rate.In addition,under small flow conditions,as the inlet particle concentration increases,the flow field leaving the sewage pump diaphragm near the outlet of the volute becomes more turbulent,and even a secondary back-flow vortex appears.

Bi_(2)O_(3)掺杂Ba_(0.85)Ca_(0.15)(Zr_(0.1)Ti_(0.88)Mn_(0.02))O_(3)压电陶瓷及微型气泵的制备与性能研究

采用固相法制备了Bi_(2)O_(3)掺杂的Ba_(0.85)Ca_(0.15)(Zr_(0.1)Ti_(0.88)Mn_(0.02))O_(3)压电陶瓷,研究了体系的微观结构,以及Bi_(2)O_(3)掺杂量对体系压电性能的影响;将体系最优性能的样品装配成微型气泵,并与日本村田的MZB1001T02微型泵进行了性能对比。研究表明,Bi_(2)O_(3)掺杂Ba_(0.85)Ca_(0.15)(Zr_(0.1)Ti_(0.88)Mn_(0.02))O_(3)的无铅压电陶瓷呈单一的钙钛矿结构,少量的Bi_(2)O_(3)掺杂使体系保持了三方-四方相共存的特性。当掺杂量(质量分数)为0.05%时,样品晶粒分布均匀,介电和压电性能最优,即ε^(T)_(33)=5 289、k_(p)=0.46、d_(33)=377pC/N、tanδ=0.72%、T_(c)=80℃,样品具有典型的介电弛豫特性。将上述样品装配在微型气泵中,在输入频率(25±2)kHz、输入电压15V条件下,测得微型气泵的气压略低于日本村田的微型泵。在某些对气压要求不高的领域,样品能够满足使用要求。

不对称电极介电弹性体的电致动响应与有限元分析

以DowCorning 186硅橡胶为介电弹性体(DE)基底膜,以精细Ag纳米颗粒和导电石墨掺杂的硅橡胶为电极,组装了不对称DE电致动膜。两电极膜存在显著的力学性能、导电性能差异,其厚度、模量、面电阻分别为96.8μm、26.6MPa、8.42kΩ/cm^2和179.3μm、32.6MPa、3.87kΩ/cm^2。导入4kV、2Hz、25%占空比的激励信号,不对称DE膜发生上下振动,中心偏离平衡位置的最大振幅为3.6mm,偏离角为17.4°。利用激光位移传感器研究了偏振位移与驱动电压、频率之间的关系,结果表明,偏振位移随驱动电压的增加而增加,随激励频率的增加而减小。同时利用ANSYS模拟了不对称DE泵膜的应力输出、功率、流量,计算结果可为研制新型智能可控微泵提供实验数据和研究基础。

介电弹性体无阀微泵设计

无阀微泵原理新颖,但压电式无阀微泵工艺复杂。介电弹性体是具有大变形的智能材料,采用图像处理的方法对其变形特性做了测试,并利用其特殊性能研制了介电弹性体无阀微泵。从流道设计、尺寸、流量和效率3个方面研究了介电弹性体无阀微泵,得到流量为142.12 m L/min,效率为0.738的介电弹性体无阀微泵。其特点是原理新颖、结构简单、流量和效率理想。

一种高速低尖峰电流功率管驱动器电路的设计

利用电荷泵自举原理,提出一种新颖的CMOS驱动电路。该电路在输入信号未进行开关操作时对电容充电,在开关操作发生时,由电荷泵电容和电源一起向负载电容充放电,从而可在不影响充放电时间的前提下降低电源对负载电容的充放电尖峰电流,减小电源噪声。该电路特别适合用来驱动采用高k介质或深槽隔离工艺的功率集成电路,可同时降低上升/下降沿时间和电源尖峰电流,并大幅减小芯片面积。采用中芯国际0.35μm标准CMOS工艺进行流片,测试结果表明,该电路可同时降低负载电容充放电尖峰电流与上升/下降沿时间。

多元高铬铸铁在介质固液泵上的应用研究

以高铬铸铁为基础并加入多种少量和微量合金,开发研制出多元高铬铸铁的过流部件,其抗磨效果得到提高,并具有良好的综合力学性能,达到了使用条件要求。寿命比原产品提高了2倍以上,且安全可靠。

能化态与线粒体及其内膜体膜表面局部脱水

荧光探针ＤＰＥ（Ｄｉｐａｌｍｉｔｏｙｌ－Ｎ－ＤａｎｓｙｌＰｈｏｓｐｈａｔｉｄｙｌｅｔｈａｎｏｌａｍｉｎｅ）标记于鼠肝线粒体及其内膜体膜表面，以测定其膜表面介电常数（ε）的变化与膜能化态的关系．在含有鱼藤酮的线粒体或其内膜体悬液中，加入琥珀酸，使膜处于能化态，可使膜表面。值分别下降１１％和２０％，分别再加ＫＣＮ，ＣＣＣＰ或Ｎｉｇｅｒｉｃｉｎ均能使ε值回升９％；若在上述悬液中，先加ＫＣＮ或ＣＣＣＰ，然后加入琥珀酸，则膜表面ε值无变化。若在线粒体或其内膜体悬液中，先加入ＣＣＣＰ或Ｎｉｇｅｒｉｃｉｎ，两者可使膜表面ε值升高１２％，其后加入鱼藤酮或琥珀酸等，则ε值均无变化，说明呼吸链抑制剂或解偶联剂抑制或解除膜的能化态，均可使膜表面ε值不发生变化。在另一组实验中，先加ＫＣＮ后，再加ＡＴｈ，使线粒体内膜处于能化态，表面ε值下降８％，此时再加寡霉素，则膜表面ε值相反上升１０％。这些实验事实均证明，线粒体膜处于能化态时，ε值下降，解除给化态，使ε值又上升。为能化态与线粒体膜表面水化力下降的相互关系提供了新信息．也为质子泵引起膜表面质子化，进而引起表面脱水，驱动膜融合的理论模型提供了新的证据。

多因子老化对抽水蓄能发电电动机定子线棒主绝缘介电性能的影响

设计搭建了新型定子线棒多因子老化平台,对抽水蓄能发电电动机定子线棒进行电、热及机械振动多因子老化试验,测量定子线棒在老化试验各老化周期后和部分周期中的介质损耗因数和电容值,并利用扫描电镜对老化后的绝缘层材料进行观察。结果表明:在测试电压高于一定值时,介质损耗因数随老化周期的增加而增大;在不同测试电压下,电容均随老化周期的增加而减小;介质损耗因数增量及电容增量均随老化周期的增加而增大;在影响介电性能变化的各老化因子中,冷热循环老化和机械振动老化起主要作用;结合老化线棒的局部放电起始电压和绝缘层老化试样的显微结构认为,多因子联合老化使得线棒主绝缘内产生的越来越多气隙等缺陷是导致其性能劣化的主要原因。

Abrasion characteristic analyses of solid-liquid two-phase centrifugal pump

Based on the solid-liquid two-phase mixture transportation test, the renormalization group (RNG) k-e turbulent model was utilized to simulate the solid-liquid two-phase turbulent flow in a centrifugal pump. By comparing the simulated and experimental results, inner flow features were revealed to improve the abrasion characteristic of the solid-liquid two-phase centrifugal pump. The influence of the solid phase on centrifugal pump abrasive performance is small when the particle volume fraction is less than 2.5%. The aggregation degree of the solid particles is enhanced as the particle diameter increases from 0.1 to 1 mm; however, the mixture density on the pressure side is reduced when the particle diameter increases to 1 mm for the impact of inertia. The wear on the hub is most severe for the shear stress on this position; it is also the largest. The wear characteristic is affected greatly by the parameters of the solid phase. The wear chracteristic can be optimized by decreasing the blade outlet angle. In the modified design, the blade angle is different, whereas the other geometric dimensions remain the same. The improved pump is simulated to contrast with the original pump. The results show that the values of mixture density and shear stress both decrease. The wear condition of the blade is improved to a certain extent.

基于DPM模型的离心泵非定常固液两相流及磨损计算（英文）

In this paper, the discrete phase model （DPM） and semi-empirical wear model were used to simulatethe unsteady solid-liquid two-phase flows and wear in a centrifugal pump, to explore the solid particle movementand the wear of the pump. The liquid phase was solved by the fluid governing equations in the Euler coordinatesystem; the solid particle phase was treated as a discrete medium and solved by the equations of particle motion inLagrange coordinate. The solid-liquid phase coupling was performed using iterative numerical method. An IS typecentrifugal pump was selected in the simulation. Water and sand particle were chosen as the continuous phase andthe discrete phase, respectively. The particle volumetric ratio at the pump inlet was in the range of 0.5%-3%with the particle size of 0.05-0.2 mm. The flow characteristics of the solid-liquid two-phase flows, the trajectoryof the particle cluster and the distribution of wear rate in the centrifugal pump were obtained by the simulation.

离心泵汽蚀的压力脉动判据研究

离心泵汽蚀的研究是多年来研究工作者极关注的问题之一，本文以流体动力学为基础，以空泡动力学为指导，对离心泵空化空蚀的机理和早期判据进行了深入的探讨。为汽蚀的早期诊断和汽蚀检测的工程应用，提供了有用的依据。

典型电流体动力学传导泵性能的实验研究

为考查典型电流体动力学传导泵性能,推动其应用于电子元器件微通道液冷,设计了平嵌电极与多孔电极电导泵,并搭建电导泵实验系统,测试了这2种电导泵泵送介电液体HFE-7100的性能。结果表明:施加10 kV直流电压时,6对平嵌电极电导泵产生流量194.5 mL/min,动压40.3 Pa,最大静压72.1 Pa;3对孔径为1.5 mm的多孔电极电导泵产生流量438.2 mL/min,动压173.0 Pa,最大静压363.5 Pa。可见,相比平嵌电极电导泵,多孔电极电导泵具有更好的性能。

Homogeneous large deformation analysis of a dielectric elastomer peristaltic actuator

A series of isometric,radially expanding tubular units,made of dielectric elastomer with compliant electrodes,constitute a soft linear peristaltic pump with distributed actuation for transport of incompressible fluids.Based on the Gent strain energy model,this paper theoretically analyzes the homogeneous large deformation of the peristaltic unit.We discuss the effects of axial prestretch on the actuation of the actuator.We then predict the maximum actuation strain of this actuator which is limited by dielectric strength of the polymer.The results presented here extend the previous study based on linear elasticity,and can predict the electromechanical behaviors of the novel actuator at large deformations.

电流体动力学传导泵研究进展

本文介绍了一种新兴的流体流动生成与控制技术——电流体动力学传导泵(电导泵).该种泵是基于电场与介电液体直接相互作用的一类非机械泵.库仑力为泵驱动力,自由电荷来源于液体中杂质或弱电解质的解离过程.除了拥有电流体泵的普遍优点(如可通过电场实现智能主动控制、无机械运动部件、设计简单、重量轻、适用于低重力空间等特殊环境、能耗低等),电导泵还具有性能稳定、工作寿命长等独特优势.除了流量调控、传热强化和增强混合等传统应用,近年来电导泵在微型机器人驱动、可穿戴设备、机电一体化(制动器)等领域获得多种创新应用.目前,国外电导泵技术已从宏观尺度单相流体逐步发展到微尺度多相流研究,并开始在低重力环境在轨进行测试,有望应用于未来航天器空间热管理等领域.国内对电流体动力学的研究起步较晚,缺少电导泵相关的研究.因此,本文从电导泵工作原理、理论模型、数理方程、研究现状和前沿进展等方面进行了总结,并对未来发展进行了展望.