基于电磁-结构场耦合的干式空心电抗器短路电动力计算

为研究叶片数对船用离心泵性能的影响,结合CFD软件CFX对三种不同叶片数的船用离心泵作全流场定常计算。计算时选用NSL125 415/A02型船用离心泵,以清水为工作介质,基于雷诺时均N S方程和标准κ ε紊流模型,压力、速度耦合采用SIMPLEC算法进行速度分量和压力方程的分离求解。通过不同叶片数船用离心泵在设计工况下的数值模拟和对比分析,揭示了不同叶片数船用离心泵的内部流动规律,获得了叶片数对船用离心泵的扬程、效率和性能的影响程度,为船用离心泵叶片数选取提供了参考。     

叶片进口边位置对小流量工况下离心泵空化特性的影响

为研究叶片进口位置对小流量工况下离心泵空化性能的影响,应用数值计算方法模拟了比转数为81的离心泵的三种模型,得到不同进口边位置的离心泵空化特性,并分析了叶轮内部流场与空化性能曲线的影响关系。结果表明,在小流量工况下,低比转速离心泵叶片进口边位置越靠前,抗空化性能较好,但严重空化后扬程衰减更快,流道直接被空泡堵塞,流道和叶片表面气泡分布较均匀,且气泡充斥流道速度较快,气泡体积分数各流道差值越小。相比较而言,叶片进口位置越靠后,气泡在流道内部和叶片背面分布不均匀,易出现噪声和振动,但在断裂空化状态,气泡并未完全堵塞流道,扬程下降速度较慢。整体来看,在小流量工况下,叶片进口边位置越靠前,离心泵的抗空化性能较好,并通过试验研究验证了模拟结果的可靠性。研究成果可为小流量工况下低比转速离心泵抗空化性能的优化提供参考。     

分流叶片进口直径对离心泵空化特性影响

为探究分流叶片对离心泵空化性能的影响,以IS80-50-200模型泵为研究对象,在模型泵上设计添加了3种不同进口直径分流叶片,利用CFD软件对离心泵进行全流道三维定常湍流空化数值模拟,分析不同汽蚀余量对离心泵空化特性和叶轮内部流场的影响,探究叶轮空化初生和发展规律。结果表明:添加分流叶片后,泵的扬程、效率均有一定程度的提高,且分流叶片的进口直径对扬程和效率的影响不大;泵的H-Q曲线驼峰减弱;泵的抗空化性能均有提高。在研究的水力模型中,当离心泵短叶片进口直径为0.8D2时,泵的抗空化性能最好。添加分流叶片后,长叶片两侧压差减小,叶轮进口处的低压区范围变小,有利于提高泵的抗空化能力。     

过渡流道径向长度对离心泵水力性能的影响

为研究过渡流道径向长度对离心泵水力性能的影响,建立了4种不同径向长度的过渡流道模型,并借助ANSYS软件对离心泵进行了全流场的数值模拟。根据数值模拟结果,对比分析了泵外特性曲线和设计工况下过渡流道内部的流动状态。研究表明:额定工况及小流量工况下,径向长度对离心泵外特性的影响不大,但在大流量工况下,随着长度的减小,离心泵的扬程和效率均有所降低;过渡流道径向长度为510和610 mm的离心泵,扬程与效率的波动不大;过渡流道扩散段内部的回流和漩涡较为明显,且小径向长度过渡流道扩散段内部的回流和漩涡更为明显。     

长短叶片离心泵内固液两相流场三维数值模拟

为了分析长短叶片离心泵输送固液两相流时叶轮内部流场和流动规律,应用FLUENT软件分别对普通叶片离心泵和长短叶片离心泵内的固液两相流场进行数值模拟,对比分析两者的总压、静压以及固相颗粒浓度的分布规律。结果表明:无论是普通离心泵还是长短叶片离心泵,它们的静压和总压的变化规律相同,均沿着出流方向有增大趋势,在叶轮出口处压力达到最大值;长短叶片离心泵内固相颗粒浓度减小,明显提高了泵的抗磨损性能;与普通离心泵相比,长短叶片离心泵叶轮流道内颗粒的高浓度区域明显变小,运行更加平稳;长短叶片离心泵中颗粒的分布更均匀,流动损失大大减小,流动状态更好。     

基于CFD的离心泵叶轮内部流动分析与试验对比

为了解有空间导叶的离心泵叶轮内部水力性能,借助NUMECA公司的FINE软件,采用NavierStokes方程和Spalart-Allmaras湍流模型,分别在0.8Qopt、Qopt、1.2Qopt工况下对离心泵内部流动进行数值模拟计算。结果表明,随流量的增加,靠近进口边叶片吸力面的抗空蚀性能逐渐增强;叶片间轴向漩涡的位置与流量无关;出口边径向速度随流量增加而增大;出口边切向速度随流量增加而减小。与试验结果的比较表明,在Qopt工况下,数值模拟能有效预测泵内部的复杂三维流动与水力性能。     

基于CFD的离心泵内部流场数值模拟

采用GAMBIT建模划分网格,基于CFD技术,采用雷诺时均N-S方程和RNG k-ε湍流模型对离心泵内部的二维湍流流动进行了数值模拟,得到了离心泵内部流场的压力分布、速度分布及气蚀特性规律。结果表明,叶轮内部流体从叶片入口到离心泵出口速度不断降低,压力不断升高。同时,得到了气蚀分布特性,在所研究工况条件下,气蚀首先在叶片两侧出现。模拟结果对工程实践和离心泵水力性能研究有一定的指导意义。     

叶片后弯角对车用离心压气机性能的影响

对比分析了6种不同转速下压气机性能的试验与仿真结果.在验证了ANSYS CFX软件用于压气机性能模拟分析中的可靠性后,采用数值模拟方法对3种不同叶片后弯角的叶轮进行了性能计算,得到了相关转速下的压气机特性曲线.仿真结果表明:在不改变压气机出口静压时,在一定的叶片出口角范围内,叶片后弯角的增加使两条特性曲线均向小流量方向偏移,但近喘振点边界得到了拓展,使得压气机的流量范围变得更宽;在小流量区域内,叶片后弯角的增大能够改善压气机内部流动状况,提高叶轮工作效率;而在大流量区域内,较大的叶片后弯角会使叶轮的流通特性降低,叶轮的工作效率反而会降低;适当增加叶片后弯角可以增大压气机工作范围,使压气机效率和流道内的流动均得到提高和改善.     

带可调进口导叶离心压缩机的性能分析

以数值模拟的方式对某带可调进口导叶的离心压缩机级内部流动进行了分析研究。对计算得到的性能曲线及相对速度矢量图的分析表明，进口导叶正旋绕时性能曲线向小流量区移动，负旋绕时向大流量区移动；经最高效率点进入小流量区后效率下降较快；在进口导叶大安装角情况下，在大的流量范围内导叶区域均存在显著分离，大流量时短叶片吸力面前部有回流区，小流量时长叶片吸力面上发生分离。     

分流叶片对离心泵非定常空化流动特性影响分析

采用ANSYS(有限元分析)软件,对有/无分流叶片的离心泵流道内的空化流动进行定常及非定常的数值模拟,分析分流叶片对离心泵空化性能的影响,同时对叶轮进出口以及蜗壳内的压力场进行监测,得到空化条件下的压力脉动规律。结果表明:添加分流叶片后,泵的空化性能提高,临界空化余量减小。随着空化余量NPSHA的不断下降,空化所诱导的压力脉动逐渐加剧,其中以泵隔舌处的压力脉动最为明显。有/无分流叶片离心泵内压力脉动主要发生在叶频及其谐波位置。添加分流叶片后,离心泵内的压力脉动得到明显改善。     

基于湍流数值模拟的双吸泵性能预测与验证

为了提高双吸泵的性能,采用RNGk-ε方程湍流模型和标准SIMPLE算法对某双吸离心泵全流道进行了三维湍流数值模拟分析。在流场数值模拟的基础上进行多工况的流体动力性能预测,并与实验值进行比较验证,表明该方法能够较为准确地预测出双吸泵的性能曲线。数值模拟得到的双吸泵内部流动速度、压力分布等能够进一步对双吸泵的内部特性进行预测分析。通过性能预测,对指导流道水力优化设计或实际工程改型设计等发挥了重要作用。     

导流孔径变化对磁力驱动离心泵流动性能的影响

为研究导流孔径变化对磁力驱动离心泵内部流场及水力性能的影响规律,分别以6、8、10 mm~3种不同导流孔径的磁力驱动离心泵模型为研究对象,通过定常、非定常以及流热耦合数值计算与外特性试验相结合的研究方法,分析并得到了导流孔径变化对磁力驱动离心泵外特性、内部流场、温度场以及压力脉动特性的影响规律。研究表明:导流孔径的变化对磁力驱动离心泵外特性曲线、内部流场以及压力脉动特性的影响较小,对冷却循环流道内的流场、温度场以及压力脉动特性的影响较大。     

基于响应面法的圆盘泵叶轮优化研究

为了提高圆盘泵的水力性能,以径向直叶片圆盘泵为研究对象,结合计算流体动力学方法(CFD)与响应面分析法,研究叶轮结构参数对泵扬程和效率的影响。以叶片高度、叶片数量和盘间距为优化设计变量,泵的扬程和效率为响应变量,基于Box-Behnken样本点设计法进行三因素三水平设计,建立17组样本点。通过ANSYS CFX数值计算软件对各个样本点的设计模型进行数值模拟,并基于二阶响应面回归方程拟合了叶轮结构参数与扬程和效率之间的关系表达式。研究结果表明:叶片高度、叶片数量和盘间距均对泵的水力性能有明显的影响。多因素交互作用中叶片高度和盘间距的组合影响最为显著。通过响应面方程找到了最优参数组合,优化后的圆盘泵扬程在各流量工况下平均提升了22 m,最高效率提升了15%。     

Unsteady internal flow conditions of mini-centrifugal pump with splitter blades

Mini centrifugal pumps having a diameter smaller than 100mm are employed in many fields. But the design method for the mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Therefore, mini centrifugal pumps with simple structure were investigated by this research. Splitter blades were adopted in this research to improve the performance and the internal flow condition of mini centrifugal pump which had large blade outlet angle. The original impeller without the splitter blades and the impeller with the splitter blades were prepared for experiment. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on performance and internal flow condition of mini centrifugal pump. On the other hand, a three dimensional unsteady numerical flow analysis was conducted to investigate the change of the internal flow according to the rotor rotation. It is clarified from the experimental results that the performance of the mini centrifugal pump is improved by the splitter blades. The blade-to-blade low velocity region was suppressed in the case with the splitter blades. In addition to that, the unsteady flows near the volute casing tongue were suppressed due to the splitter blades. In the present paper, the performance of the mini centrifugal pump is shown and the unsteady flow condition is clarified with the results of the numerical flow analysis. Furthermore, the effects of the splitter blades on the performance and the unsteady internal flow condition are investigated.     

Flow and transmission characteristics of the multistage hydrogen Knudsen pump in the micro-power system

The multistage hydrogen Knudsen pump based on the thermal transpiration effect has exciting application prospects for hydrogen transport in the micro-power system. The multistage hydrogen Knudsen pump with the silica microchannel is beneficial to its temperature control, which can accurately provide hydrogen transport and storage for the micro-power system. In this paper, the model of the multistage hydrogen Knudsen pump with the silica microchannel is established. The effects of the microchannel height, width and parallel number on the flow and transmission characteristics of the multistage hydrogen Knudsen pump are studied by using the method of N–S equations with the slip boundary. The temperature difference, Knudsen number, thermal transpiration effect, maximum mass flow rate, maximum pressure difference and performance curve under different microchannel parameters are analyzed in detail. The results show that the thermal transpiration effect increases with the microchannel height and decreases with the microchannel width. As the number of parallel microchannels increases, the microchannel is closer to the silicon cantilever, and the thermal transpiration effect becomes stronger. The pumping performance increases with the microchannel height, width and parallel number. The pressurization performance increases with the microchannel height and parallel number. The research results have important guiding significance for the application and design of the multistage hydrogen Knudsen pump in the micro-power system.     

Performance analysis of mini centrifugal pump with splitter blades

Design method for a mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Then, a semi-open impeller for the mini centrifugal pump with 55mm impeller diameter is adopted in this research to take simplicity and maintenance into consideration. Splitter blades are adopted in this research to improve the per- formance and internal flow condition of mini centrifugal pump having large blade outlet angle. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on the performance and internal flow condition of the mini centrifugal pump. A three dimensional steady numerical flow analysis is con- ducted to analyze rotor, volute efficiency and loss caused by a vortex. It is clarified from the experimental results that the performance of the mini centrifugal pump is improved by the effect of the splitter blades. Flow condition at outlet of the rotor becomes uniform and back flow regions are suppressed in the case with the splitter blades. Further, the volute efficiency increases and the vortex loss decreases. In the present paper, the performance of the mini centrifugal pump is shown and the flow condition is clarified with the results of the experiment and the nu- merical flow analysis. Furthermore, the performance analyses of the mini centrifugal pumps with and without the splitter blades are conducted.     

Performance enhancement of a pump impeller using optimal design method

This paper presents the performance evaluation of a regenerative pump to increase its efficiency using optimal design method.Two design parameters which defme the shape of the pump impeller,are introduced and analyzed.Pump performance is evaluated by numerical simulation and design of experiments(DOE).To analyze three-dimensional flow field in the pump,general analysis code,CFX,is used in the present work.Shear stress turbulence model is employed to estimate the eddy viscosity.Experimental apparatus with an open-loop facility is set up for measuring the pump performance.Pump performance,efficiency and pressure,obtained from numerical simulation are validated by comparison with the results of experiments.Throughout the shape optimization of the pump impeller at the operating flow condition,the pump efficiency is successfully increased by 3 percent compared to the reference pump.It is noted that the pressure increase of the optimum pump is mainly caused by higher momentum force generated inside blade passage due to the optimal blade shape.Comparisons of pump internal flow on the reference and optimum pump are also investigated and discussed in detail.     

脉冲液体射流泵能量平衡的数值研究

运用能量平衡分析原理,根据脉冲液体射流泵主要流动部件的能量损失压力比公式,利用脉冲液体射流泵性能数值计算模块,对脉冲液体射流泵能量平衡进行了数值研究,分析了主要流动部件的能量损失变化及其对脉冲液体射流泵性能的影响,并与恒定液体射流泵的能量损失压力比、性能及效率进行了对比。结果表明,脉冲射流是提高射流泵传能、传质效率的有效途径。     

径向导叶与空间导叶的优劣分析与试验

对某一参数的节段式多级泵导叶进行研究。通过数值模拟对比分析传统的径向导叶(正、反导叶)与空间导叶对泵性能的影响并进行试验验证。以通用CFD软件NUMECA为计算平台,分别对叶轮加径向导叶及空间导叶流场进行分析,发现空间导叶在大流量区容易获得较好性能,但在小流量区损失较大,扬程曲线容易出现驼峰。在小流量区径向导叶性能要优于空间导叶。     

The effect of blade outlet angle on performance and internal flow condition of mini turbo-pump

Mini turbo-pumps having a diameter smaller than 100mm are employed in many fields; automobile radiator pump, ventricular assist pump, cooling pump for electric devices, washing machine pump and so on. Further, the needs for mini turbo-pumps would become larger with the increase of the application of it for electrical machines. It is desirable that the mini turbo-pump design is as simple as possible due to restriction to make precise manufactures. But the design method for the mini turbo-pump is not established because the internal flow condition for these small-sized fluid machineries is not clarified and conventional theory is not conductive for small-sized pumps. Three types of rotors with different outlet angles are prepared for an experiment and a numerical analysis. The performance tests are conducted with these rotors in order to investigate the effect of the blade outlet angle on performance and internal flow condition of mini turbo-pumps. It is clarified from the experimental results that head of the mini turbo-pump increases and maximum efficiency flow rate shifts to larger flow rate according to the increase of the blade outlet angle, however the maximum efficiency decreases with the increase of it. In the present paper, the performance of the mini turbo-pump is shown and the internal flow conditions are clarified with the results of the experiment and the numerical flow analysis. Furthermore, the effects of the blade outlet angle on the performance are investigated and high performance design with simple structure for the mini turbo-pump would be considered.