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.

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.

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.

Investigation on pumping oxygen characteristics of (Bi_2O_3)_(0.73)(Y_2O_3)_(0.27) solid electrolyte

（Bi2O3）0.73（Y2O3）0.27 fine powders prepared by wet chemical precipitation method were cold isostatically pressed to form solid electrolyte tubes, and sintered at 900 ℃ for 10 h in the air. Their pumping oxygen characteristics in non-dehydrated Ar gas were investigated, where a ZrO2 （Y2O3 stabilized） oxygen sensor was used to measure the oxygen partial pressure Po2. The results showed that the Po2 value reached magnitudes of 1×10^-2-1×10^-10 Pa at the applied pumping oxygen voltage of 0.5 V, 1×10^-37-1×10^-27 Pa at 1.0 V and 1×10^-53-1×10^47 Pa at 2.0 V within the temperature range from 550 to 650 ℃. Moreover, no cracks were found in the tested solid electrolyte tubes. Thus, the Bi2O3-Y2O3 system might be used in solid electrolyte oxygen pump for purifying gases.

The Development of Gear Pump CAD/CAPP Based on Solid Works

Nowadays, many kinds of software, which have succes sf ully created the integration of CAD, CAPP and CAM, find their disadvantages in p ractical manufacturing. As a result, it is welcomed to develop small CAD/CAPP sy stems on a proper CAD platform, which aim at requirements of factories. Based on the one of the most popular three-dimensional design software SolidWorks, we successfully developed a set of gear pump CAD /CAPP software for Huaiyin Gene ral Factory of Mechanics. 1 The architecture and function of the software According to the need of the enterprises, the general structure of the software contain two subsystems, which are detailed as follows: · The gear pump CAD subsystem contains four main modules, including the optiona l design module of gear pump, module of part design, the module of entity modeli ng and the module of drawing which creates 2 D drawings of parts and assembly c orresponding 3 D modals. · The gear pump CAPP subsystem, which is a combination of creative mode and der ivate mode, also includes four modules, they are the module of access to feature s, the module of planning process route, the module of designing process sheets and the module of generating process documents. 2 The developing environment of the system Basing on Windows 98 and SolidWorks2001 platform, this system creates all functi ons by using Visual C++ 6.0 as developing tools. 3 The keys to the CAD/CAPP integration 3.1 The establishment of product information modal The information of parts is the basis of process planning. In this system, we us e feature modeling to describe the information of parts and assembly of gear pum p, and set up a fundamental basis for the whole system. The information module o f gear pump includes the information of both the assembly and the parts; the par t-describing module uses four-layer structure that is subassembly layer, part layer, feature layer and geometric layer. 3.2 The operation of the information on feature modeling After establishment of information mode of gear pump, the next key problem is ho w to transmit information of product to CAPP subsystem. In order to integrate pe rfectly, connecting CAD with CAPP directly can be a good method. In this system, all information of parts is store in the part drawing files, and the CAPP syste m can load these files to get information. The gear pumps, which are produced by Huaiyin General Factory of Mechanics, are usually belong to several similar typ es, and this means that most products possess large number of similar feature. T herefore, we can easily establish a specific feature for gear pump CAD/CAPP syst em. All parts are created by selecting these features and/or adding few special features. In the module of access to feature of CAPP subsystem, the main task is to find the features and the information will be easily got. 4 Conclusion This system successfully creates gear pump CAD/CAPP integration based on SolidWo rks. 3D CAD software provide more convenient platform for integration and will i nevitably become the mainstream of product design. By developing this system, we clearly realize the promising future of SolidWorks.

基于SolidWorks的齿轮泵CAD/CAPP集成

结合作者的开发实践,介绍了基于集成的产品特征建模技术的齿轮泵CAD/CAPP集成的结构和功能以及利用VC^++在SolidWorks环境中编程实现系统的方法。

基于Solid Edge的齿轮泵虚拟装配系统

利用SolidEdge提供的Part模块进行三维实体设计 ,用Draft模块生成零件图 ,采用VB的ActiveXAutomation技术调用工程库文件对零件实现尺寸驱动。利用VB作为平台将整个工作过程进行整合 。

用VB开发Solid Edge柱塞泵虚拟装配系统的研究

利用SolidEdge提供的Part模块进行三维实体设计 ,并以Draft模块生成零件图 ,通过VB的ActiveXAutomation技术调用工程库文件对零件进行尺寸驱动。在VB平台上将整个工作过程整合 ,实现了柱塞泵的虚拟装配。

基于Solid Edge的齿轮泵CAD系统

齿轮泵CAD系统是用VB作为平台,开发Solid Edge软件,用编程方法生成三维模型的参数化设计,实现了完全的程序驱动,在生产加工中只需改动相关变量的尺寸,即可设计出变形新产品。该系统由方案选择、结构设计计算、零件建模、装配、零件图转换、尺寸驱动、数据库管理、帮助等8个模块组成。

基于SolidWorks与ANSYS的高压乳化液泵曲轴力学特性分析

以BRK500/37.5型高压乳化液泵曲柄连杆机构为研究对象,通过Solid Works三维软件建立了高压乳化液泵的三维实体模型,并利用自行研发的曲轴受力自动计算系统对曲轴进行了受力分析,得到曲轴载荷的变化规律。选取其中5种最危险的工况,利用ANSYS WORKBENCH和Solid Works之间的无缝连接,将做好的模型导入到ANSYS WORKBENCH软件中去,对曲轴进行静力学分析,得到曲轴的应力和应变分布情况,证明了该曲轴在强度和刚度方面均满足工作要求。同时对曲轴进行了自由状态和约束状态下的模态分析,计算得到其固有频率和振型,并对两种模态分析结果进行了比较,证明了该曲轴具有良好的动态特性,结构设计较为合理。分析结果为乳化液泵曲轴的结构改进和优化设计提供参考。

LD Pumped High Efficient Intracavity Frequency-Doubled Green Laser

A laser diode (LD) pumped Q switched high efficient intracavity frequency doubled Nd ∶YAG laser is reported here. The authors have designed an optical coupler and pointed out that the key to increasing harmonic conversion efficiency is to decrease the loss of fundamental wave. In the experiments, a fundamental mode output laser was acquired. When the pumping power was 12 W, 2.6 W average output power at 1 064 nm with AO Q switch was obtained. 2.1 W average output power at 532 nm was obtained with intracavity frequency doubling, and the highest second harmonic conversion efficiency was 82 0 0.

A tunable corner-pumped Nd:YAG/YAG composite slab CW laser

A corner-pumped Nd：YAG/YAG composite slab continuous-wave laser operating at 1064 nm,1074 nm,1112 nm,1116 nm,and 1123 nm simultaneously and a laser that is tunable at these wavelengths are reported for the first time.The maximum output power of the five-wavelength laser is 5.66 W with an optical-to-optical conversion efficiency of 11.3%.After a birefringent filter is inserted in the cavity,the five wavelengths can be separated successfully by rotating the filter.The maximum output powers of the 1064 nm,1074 nm,1112 nm,1116 nm,and 1123 nm lasers are 1.51 W,1.3 W,1.27 W,0.86 W,and 0.72 W,respectively.

基于Solid Works的P2200泥浆泵曲轴连杆机构动态仿真分析

基于P2200泥浆泵曲轴连杆机构的结构以及受力的基础上,运用Solid Works软件对泥浆泵曲轴连杆机构进行三维实体建模及装配。并用Solid Works Motion,利用多体系统动力学理论,在Solid Works Motion中给模型添加转动力矩,对曲轴连杆机构进行运动学仿真分析,得出十字头的位移、速度和加速度曲线,验证了模型的可用性,完成了P2200泥浆泵曲轴连杆的设计。

High-power and high optical conversion efficiency diode-end-pumped laser with multi-segmented Nd：YAG/Nd：YVO-4

A novel flat-flat resonator consisting of two crystals（Nd：YAG ＋ Nd：YVO4） is established for power scaling in a diode-end-pumped solid-state laser. We systematically compare laser characteristics between multi-segmented（Nd：YAG ＋ Nd：YVO4） and conventional composite（Nd：YAG ＋ Nd：YAG） crystals to demonstrate the feasibility of spectral line matching for output power scale-up in end-pumped lasers. A maximum continuous-wave output power of 79.2 W is reported at 1064 nm, with Mx2= 4.82, My2= 5.48, and a pumping power of 136 W in the multi-segmented crystals（Nd：YAG ＋ Nd：YVO4）. Compared to conventional composite crystals（Nd：YAG ＋ Nd：YAG）, the optical-optical conversion efficiency of multi-segmented crystals（Nd：YAG ＋ Nd：YVO4） from 808 nm to 1064 nm is enhanced from 30% to 58.8%,while the laser output sensitivity as affected by the diode-laser temperature is reduced from 55% to 9%.

Analytical modelling of end thermal coupling in a solid-state laser longitudinally bonded by a vertical-cavity top-emitting laser diode

The intrinsic features involving a circularly symmetric beam profile with low divergence, planar geometry as well as the increasingly enhanced power of vertical-cavity surface-emitting lasers （VCSELs） have made the VCSEL a promising pump source in direct end bonding to a solid-state laser medium to form the minimized, on-wafer integrated laser system. This scheme will generate a surface contact pump configuration and thus additional end thermal coupling to the laser medium through the joint interface of both materials, apart from pump beam heating. This paper analytically models temperature distributions in both VCSEL and the laser medium from the end thermal coupling regarding surface contact pump configuration using a top-emitting VCSEL as the pump source for the first time. The analytical solutions are derived by introducing relative temperature and mean temperature expressions. The results show that the end contact heating by the VCSEL could lead to considerable temperature variations associated with thermal phase shift and thermal lensing in the laser medium. However, if the central temperature of the interface is increased by less than 20 K, the end contact heating does not have a significant thermal influence on the laser medium. In this case, the thermal effect should be dominated by pump beam heating. This work provides useful analytical results for further analysis of hybrid thermal effects on those lasers pumped by a direct VCSEL bond.

Red-shift law of intense laser-induced electro-absorption in solids

A theoretical study on the red-shift of laser-induced electro-absorption is presented. It is found that laser-induced red-shift scales with the cube root of the pump laser intensity in the optical tunneling regime and has an obvious deviation from this scale in the multi-photon regime. Our results show that in the optical tunneling regime, the laser-induced red shift has the same law as that in the direct current （DC） approximation. Though the scales are the same in the optical tunneling regime, the physical pictures in the two cases are quite different. The electro-absorption in the DC case is a tunneling-assisted transition process, while the laser-induced electro-absorption is a mixed multi-photon process.

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。

螺杆泵转速对油水旋流分离管流场特性的影响

旋流分离器在井下采油螺杆泵作用下会发生复杂的振动现象,对旋流分离器内部流场造成一定影响。为研究螺杆泵不同转速下旋流分离器内部流场的变化规律,以同井注采工艺中螺杆泵作用下的旋流分离管柱为研究对象,针对振动壁面旋流分离管柱结构及工作特点,基于计算流体动力学方法、计算固体力学方法以及流固耦合理论,建立流固耦合力学模型;利用流固耦合分析方法,对双螺杆泵转动条件下井下旋流分离管柱内速度场、油相分布、涡量及湍动能等流场特性进行分析。分析结果表明:随着螺杆泵转速升高,分离器内切向速度和轴向速度强度逐渐减弱,径向速度的不对称性逐渐加剧,转速的周期性变化还会造成径向速度场分布的偏移;螺杆泵不同转速下旋流分离器内部涡量分布不同,随着转速升高,溢流管以及锥段部分附近相关流场的涡旋明显增强;旋流器溢流口附近油相体积分数会随着螺杆泵转速的升高而减小;不同螺杆泵转动状态下,大颗粒油滴的分布不同。所得结果可为螺杆泵井下旋流分离同井注采系统的设计及螺杆泵的转速设定提供参考。

Development and Research on All-solid-state Intracavity Sum-frequency laser

Generation of intracavity multi-wavelength and the basic principle of sum-frequency lasers are discused, and the current research status and development of laser diode pumped lasers are introduced in detail.