基于FLUENT数值模拟的离心泵内冰浆两相流流动特性分析

针对冰浆两相流在离心泵的流动特性问题,基于欧拉法建立冰浆Mixture两相流模型,通过FLUENT软件对冰浆流动特性进行数值模拟,得到了在不同流量工况下的离心泵内部压力场、速度场以及冰晶颗粒分布特性.多次数值计算,获得离心泵在输送含冰率为10％的冰浆时的性能特性曲线,并与该离心泵在输送清水时的性能曲线进行了对比分析.研...     

低比转速离心泵叶轮的设计

通过对叶轮内液流流动分析 ,提出了减小叶轮出口射流——尾流结构的措施。为减小圆盘摩擦损失 ,对叶轮结构采取了适量车削前后盖板、周向修圆叶片的方法。     

Influence of blade wrap angle on centrifugal pump performance by numerical and experimental study

The existing research on improving the hydraulic performance of centrifugal pumps mainly focuses on the design method and the parameter optimization. The traditional design method for centrifugal impellers relies more on experience of engineers that typically only satisfies the continuity equation of the fluid. In this study, on the basis of the direct and inverse iteration design method which simultaneously solves the continuity and motion equations of the fluid and shapes the blade geometry by controlling the wrap angle, three centrifugal pump impellers are designed by altering blade wrap angles while keeping other parameters constant. The three-dimensional flow fields in three centrifugal pumps are numerically simulated, and the simulation results illustrate that the blade with larger wrap angle has more powerful control ability on the flow pattern in impeller. The three pumps have nearly the same pressure distributions at the small flow rate, but the pressure gradient increase in the pump with the largest wrap angle is smoother than the other two pumps at the design and large flow rates. The pump head and efficiency are also influenced by the blade wrap angle. The highest head and efficiency are also observed for the largest angle. An experiment rig is designed and built to test the performance of the pump with the largest wrap angle. The test results show that the wide space of its efficiency area and the stability of its operation ensure the excellent performance of the design method and verify the numerical analysis. The analysis on influence of the blade wrap angle for centrifugal pump performance in this paper can be beneficial to the optimization design of the centrifugal pump.     

半开式叶轮离心泵的效率优化与分析

为了提高半开式叶轮离心泵的水力效率,应用速度系数法对半开式叶轮离心泵的水力效率进行了优化,并采用k-ε湍流模型和标准壁面函数对离心泵进行了数值模拟,仿真分析了蜗壳和叶轮顶端问不同间隙以及不同叶片数对离心泵水力效率的影响。研究结果表明,当蜗壳与叶轮顶面的间隙为0．5mm,叶片数为6时,离心泵的效率较好。     

基于SolidWorks的化工离心泵叶轮模具设计

针对传统离心泵叶轮设计步骤繁琐的不足,提出了基于SolidWorks的三维参数化离心泵叶轮注塑模设计方法。简单介绍了SolidWorks的主要功能模块及离心泵叶轮模具设计的流程,详细阐述了离心泵叶轮模具设计的步骤。设计中,叶轮采用尼龙6/10材料,其拔模斜度为1.5°,收缩率为1%。通过对模具各零部件的造型与实时修改,实现了离心泵叶轮模具的参数化设计,并完成了模具的虚拟装配及加工出详图的快速输出。本方法对工程设计具有一定的实用价值。     

3D Particle image velocimetry test of inner flow in a double blade pump impeller

The double blade pump is widely used in sewage treatment industry,however,the research on the internal flow characteristics of the double blade pump with particle image velocimetry(PIV) technology is very little at present.To reveal inner flow characteristics in double blade pump impeller under off-design and design conditions,inner flows in a double blade pump impeller,whose specific speed is 111,are measured under the five off-design conditions and design condition by using 3D PIV test technology.In order to ensure the accuracy of the 3D PIV test,the external trigger synchronization system which makes use of fiber optic and equivalent calibration method are applied.The 3D PIV relative velocity synthesis procedure is compiled by using Visual C++ 2005.Then absolute velocity distribution and relative velocity distribution in the double blade pump impeller are obtained.Test results show that vortex exists in each condition,but the location,size and velocity of vortex core are different.Average absolute velocity value of impeller outlet increases at first,then decreases,and then increases again with increase of flow rate.Again average relative velocity values under 0.4,0.8,and 1.2 design condition are higher than that under 1.0 design condition,while under 0.6 and 1.4 design condition it is lower.Under low flow rate conditions,radial vectors of absolute velocities at impeller outlet and blade inlet near the pump shaft decrease with increase of flow rate,while that of relative velocities at the suction side near the pump shaft decreases.Radial vectors of absolute velocities and relative velocities change slightly under the two large flow rate conditions.The research results can be applied to instruct the hydraulic optimization design of double blade pumps.     

多级离心泵首级叶轮停机特性数值研究

针对多级离心泵在突然断电情况下可能出现的意外事故问题,基于滑移网格技术、用户自定义函数和SIMPLE算法,在关死点处和给定转速下降规律情况下,对一多级离心泵首级叶轮的停机过程进行了内部非定常粘性流动的数值模拟,通过数值计算获得了多级离心泵首级叶轮停机过程的外特性和内部流场演化特性,重点分析了叶轮进口、叶轮出口和反导叶出口3个位置处的瞬态物理量变化。研究结果表明,无量纲扬程系数在停机之前和停机过程前期阶段基本不变,而在停机过程末期迅速下降,叶轮停止转动时,各个物理参数并未同步趋零,总之表现出明显的瞬态行为特征;叶轮出口处的物理量参数变化受叶轮转动影响最大,其次受叶轮进口处的参数变化影响,而反导叶出口处的参数变化最小。     

Investigation of CFD calculation method of a centrifugal pump with unshrouded impeller

Currently, relatively large errors are found in numerical results in some low-specific-speed centrifugal pumps with unshrouded impeller because the effect of clearances and holes are not accurately modeled. Establishing an accurate analytical model to improve performance prediction accuracy is therefore necessary. In this paper, a three-dimensional numerical simulation is conducted to predict the performance of a low-specific-speed centrifugal pump, and the modeling, numerical scheme, and turbulent selection methods are discussed. The pump performance is tested in a model pump test bench, and flow rate, head, power and efficiency of the pump are obtained. The effect of taking into consideration the back-out vane passage, clearance, and balance holes is analyzed by comparing it with experimental results, and the performance prediction methods are validated by experiments. The analysis results show that the pump performance can be accurately predicted by the improved method. Ignoring the back-out vane passage in the calculation model of unshrouded impeller is found to generate better numerical results. Further, the calculation model with the clearances and balance holes can obviously enhance the numerical accuracy. The application of disconnect interface can reduce meshing difficulty but increase the calculation error at the off-design operating point at the same time. Compared with the standard k-ε, renormalization group k-ε, and Spalart-Allmars models, the Realizable k-ε model demonstrates the fastest convergent speed and the highest precision for the unshrouded impeller flow simulation. The proposed modeling and numerical simulation methods can improve the performance prediction accuracy of the low-specific-speed centrifugal pumps, and the modeling method is especially suitable for the centrifugal pump with unshrouded impeller.     

离心泵叶轮内水流相对速度的实验研究

该研究应用PIV系统(粒子成像测速仪)这种先进的流场测试技术在不干扰流场的情况下,进行高精度的测量,即利用撒在流体中的粒子对光的散射作用,用光学的方法记录下粒子在不同时刻的位置,从而得到粒子的位移,基于粒子对流场的跟随性,测出水流在离心泵叶片流道内的绝对速度分布,并利用软件进行数据处理,得到离心叶轮内部从吸力边到压力边相对速度的分布,为离心泵的设计提供了更为可靠的理论依据。     

离心泵内流场空化特性的数值模拟研究

针对离心泵内流场特性分析困难的问题,对离心泵流场数值模拟的几何模型建立、模型网格划分和边界条件设定进行了研究,采用计算流体力学方法,获取了在敞水性能条件下离心泵的扬程-流量、效率-流量的变化关系;结合Zwart空化模型,重点对不同有效汽蚀余量时离心泵的空化流场进行了数值模拟,得到了离心泵的内部流线和空泡分布的情况,并与该离心泵机组进行了性能测试实验,最后在此基础之上进行了对比分析。研究结果表明,所采用的数值模拟方法和空化模型合理有效,此结果可为进一步开展离心泵空化监测技术研究提供借鉴。     

Numerical prediction and performance experiment in a deep-well centrifugal pump with different impeller outlet width

The existing research of the deep-well centrifugal pump mainly focuses on reduce the manufacturing cost and improve the pump performance,and how to combine above two aspects together is the most difficult and important topic.In this study,the performances of the deep-well centrifugal pump with four different impeller outlet widths are studied by the numerical,theoretical and experimental methods in this paper.Two stages deep-well centrifugal pump equipped with different impellers are simulated employing the commercial CFD software to solve the Navier-Stokes equations for three-dimensional incompressible steady flow.The sensitivity analyses of the grid size and turbulence model have been performed to improve numerical accuracy.The flow field distributions are acquired and compared under the design operating conditions,including the static pressure,turbulence kinetic energy and velocity.The prototype is manufactured and tested to certify the numerical predicted performance.The numerical results of pump performance are higher than the test results,but their change trends have an acceptable agreement with each other.The performance results indicted that the oversize impeller outlet width leads to poor pump performances and increasing shaft power.Changing the performance of deep-well centrifugal pump by alter impeller outlet width is practicable and convenient,which is worth popularizing in the engineering application.The proposed research enhances the theoretical basis of pump design to improve the performance and reduce the manufacturing cost of deep-well centrifugal pump.     

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.     

Predicting performance of radial flow type impeller of centrifugal pump using CFD

The main objective of this work is to use the computational fluid dynamics (CFD) technique in analyzing and predicting the performance of a radial flow-type impeller of centrifugal pump. The impeller analyzed is at the following design condition: flow rate of 528 m³/hr; speed of 1450 rpm; and head of 20 m or specific speed (N_s) of 3033 1/min in US-Units. The first stage involves the mesh generation and refinement on domain of the designed impeller. The second stage deals with the identification of initial and boundary conditions of the mesh-equipped module. In the final stage, various results are calculated and analyzed for factors affecting impeller performance. The results indicate that the total head rise of the impeller at the design point is approximately 19.8 m. The loss coefficient of the impeller is 0.015 when 0.6 < Q/Q_design < 1.2. Maximum hydraulic efficiency of impeller is 0.98 at Q/Q_design = 0.7. Based on the comparison of the theoretical head coefficient and static pressure rise coefficient between simulation results and experimental data, from previous work reported in the literature [Guelich, Kreiselpumpen, Springer, Berlin, 2004], it is possible to use this method to simulate the performance of a radial-flow type impeller of a centrifugal pump. This paper was recommended for publication in revised form by Associate Editor Seungbae Lee Somchai Wongwises is currently a Professor of Mechanical Engineering at King Mongkut’s University of Technology Thonburi, Bangmod, Thailand. He received his Doktor Ingenieur (Dr.Ing.) in Mechanical Engineering from the University of Hannover, Germany, in 1994. His research interests include two-phase flow, heat transfer enhancement, and thermal system design. Professor Wongwises is the head of the Fluid Mechanics, Thermal Engineering and Two-Phase Flow Research Laboratory (FUTURE). Suthep Kaewnai obtained a B. S. degree in Mechanical Engineering, 1980 from the King Monkut’s University of Technology Thonburi and M. S. degree in Mechanical Engineering, 1983 from Chulalongkorn University. He is currently an assistant professor at King Mongkut’s University of Technology Thonburi. Suthep’s research interests are in the area of pumps and small hydroturbine. Manuspong Chamaoot received a B. S. degree, 1972 and M.S. degree in Mechanical Engineering, 1979 from the King Monkut’s University of Technology Thonburi. He is currently an assistant professor at King Monkut’s University of Technology Thonburi. His research interests are in the field of mechanical vibration for rotating equipment and computational fluid dynamics.     

减轻双吸式离心泵叶片汽蚀的试验研究

通过大量运行观测和对比,揭示了叶片进口形状改变对水泵汽蚀过程的影响和汽蚀产生的原因。通过改变离心泵叶片结构试验,提出了减轻离心泵叶片汽蚀的途径。     

离心式渣浆泵叶轮磨损机理研究及强度的有限元分析

通过对离心式渣浆泵在工作时的磨损机理研究和叶轮强度的有限元分析,来研究渣浆泵叶轮的主要磨损部位和形貌特征,为提高渣浆泵的使用寿命研究提供依据。     

短叶片转角对开缝叶片离心鼓风机叶轮性能的影响

以数值模拟的方式,对某开缝叶片离心鼓风机叶轮内部流动进行了研究,探讨了短叶片转角对离心叶轮流场及性能的影响,比较了叶片表面极限流线图谱的差异,分析了边界层分离区、叶片尾迹区及夹缝射流区流场的相互影响。     

串列叶片对离心风机叶轮性能及内部流场的影响

对串列叶片式离心风机叶轮的内部流场采用NUMECA软件进行了数值模拟研究,分析了串列叶轮不同相对周向位置因子对离心叶轮性能的影响,并对串列叶轮与原始叶轮进行了详细的流场对比分析。结果表明:相对周向位置因子对离心叶轮性能影响较大,当相对周向位置因子取0.05⁰.20时串列叶轮在性能上均有所提高且取0.10时性能达到最好;串列叶片能有效地削弱叶轮出口射流-尾迹结构对流场的影响,改善叶轮出口的速度均匀性,对控制风机的气动噪声有十分有利的影响。     

Dynamic stress analysis of sewage centrifugal pump impeller based on two-way coupling method

Current research on the operational reliability of centrifugal pumps has mainly focused on hydrodynamic instability. However, the interaction between the fluid and structure has not been sufficiently considered; this interaction can cause vibration and dynamic stress, which can affect the reliability. In this study, the dynamic stresses in a single-blade centrifugal pump impeller are analysed under different operating conditions; the two-way coupling method is used to calculate the fluid-structure interaction. Three-dimensional unsteady Reynolds-averaged Navier-Stokes equations are solved with the SST k-o9 turbulence model for the fluid in the whole flow passage, while transient structure dynamic analysis is used with the finite element method for the structure side. The dynamic stresses in the rotor system are computed according to the fourth strength theory. The stress results show that the highest stress is near the loose bearing and that the equivalent stress increases with the flow rate because the dynamic stresses are closely related to the pressure load. The stress distributions on the blade pressure side, suction side, leading edge, and trailing edge are each analysed for different flow rates; the highest stress distribution is found on the pressure side. On the blade pressure side, a relatively large stress is found near the trailing edge and hub side. Based on these results, a stress distribution prediction method is proposed for centrifugal pumps, which considers the interaction between the fluid and structuxe. The method can be used to check the dynamic stress at different flow rates when optimising the pump design to increase the pump reliability.     

固液两相离心泵内部非定常流动特性研究

为研究固液两相流离心泵内部的非定常流动特性,基于滑移网格方法,采用RNGκ-ε湍流模型以及ASMM代数滑移混合物模型,对一台高比转速固液两相离心泵内部流场进行非定常流动的数值模拟,通过分析清水工况数值计算结果、外特性性能实验结果以及固液两相流非定常数值计算结果,获得了非定常条件下固液两相输送离心泵的瞬时外特性曲线和内部流动及磨损规律。研究结果表明:在一个转动周期内,离心泵的扬程、效率和轴功率均呈现正弦波动特征;动静干涉效应使得叶轮出口处的速度和静压分布均呈现周期性波动;模型泵叶轮前后盖板的磨损情况比蜗壳壁面的磨损严重。上述计算结果可为实现高比转速固液两相流离心泵的优化水力设计和减轻磨损提供一定的理论参考。     

螺旋式纸浆离心泵内部流动的数值模拟

为分析螺旋式纸浆离心泵内部流动状态,给优化过流部件结构的优化设计提供基础,采用CFD分析软件Fluent对螺旋式离心泵内部单相流动和固液两相流动进行了数值模拟。给出了螺旋式叶轮建模方法和流场分析方法,分析了泵内流体速度和压力的分布特性,并基于流动模拟结果预测了水力性能,单相输送条件下的计算结果与试验结果取得了较好的一致。通过对一定体积浓度和颗粒粒径下固液两相流的研究计算,分析了螺旋式离心泵叶片表面以及流道内的固液相分布状态,对螺旋式结构的优化具有一定的参考意义。