泵站进水流道的两种基本流态

概述开敞式流道、斜式流道、肘形流道、钟形流道、簸箕形流道以及方箱式双向流道等各种形式的泵站进水流道内水流的基本流动形态,并从流体动力学的角度,将进水流道分为单面进水和四面进水两种基本类型。     

叶片角度对采用肘形流道的轴流泵装置特性的影响

基于RNG k-ε湍流模型和雷诺时均N-S方程,运用CFD技术对采用肘形流道的某泵站轴流泵装置分别在叶片角度为-2°,0°和+2°时进行三维流动数值模拟,以探究不同叶片角度下肘形流道的流动特性,以及肘形流道与叶片角度对轴流泵装置性能的影响,并对肘形流道内进行了非定常计算。通过计算得到叶片角度对肘形流道内水流流动状态会产生影响,叶片角度的不同导致肘形流道内的流态也会不同,不同叶片角度下叶轮进口的流速均匀度也会产生差异。在不同叶片角度下,轴流泵装置的肘形进水流道内压力脉动同样会产生很大的差异,压力脉动的差异会对机组的振动产生影响,通过对比叶片角度对采用肘形流道的轴流泵装置特性的影响,可以为工程中轴流泵装置叶片角度的调节提供一定的参考。     

污水泵站水泵吸水型式的选择

大中型污水泵站水泵吸水型式的合理选择和设计,直接影响流道内水头损失和流态,影响泵装置效率和泵站的造价。本文结合对上海污水治理二期工程某站吸水型式选型进行的模型试验内容,对吸水管、肘形进水流道及钟形进水流道三种吸水型式进行分析、比较,认为钟形水流道是大中型城市污水立式泵站理想的吸水型式。     

进水流道对轴流泵装置水力性能的影响

分析比较了包括轴流泵水力特性、装置水力特性及进出水流道水力特性在内的三组模型试验资料,指出:进水流态显著地影响泵装置的特性;泵装置的水力特性并不是泵水力特性与流道水力特性的简单迭加;进水流道最优水力设计是获得优异的泵装置特性的重要条件之一.     

进水流道对轴泵装置水力性能的影响

分析比较了包括轴流泵水力特性，装置水力特性及进出水流道水力特性在内的三组练武试验资料，指出：进水流态显著地影响泵装置的特性；泵装置的水力特性不是泵力特性与流道水力特性的简单迭加；进水流道最优水力设计是获得优异的泵装置特性的重要的条件之一。     

肘型进水、屈膝式出水流道在轴流泵站的应用研究

对国内2.3 m口径某大型轴流机组泵站装置进行了设计优化及应用研究。泵站装置由进水池、进水流道、轴流泵、出水流道、出水池组成,同时对肘型进水流道、屈膝式出水流道进行了着重研究。运用CFD数值模拟分析技术进行设计优化,确定了最优的设计方案,保证装置高效率及可靠、稳定运行。     

大型水泵出水流道优化水力设计

研究大型水泵出水流道扩散角、断面形状和中心线走向对水力损失的影响,提出当量扩散角概念,以包括沿程摩阻水力损失、扩散水力损失和出口水力损失在内的总水力损失最小为目标,对出水流道扩散角和断面形状进行优化,提出流道中心线走向优化的原则。研究结果表明,在进、出口断面位置一定的情况下,出水流道存在最优扩散角,使总水力损失最小。试验证明,由于水泵出水弯管的作用,出水流道实际开始脱流的扩散角小于理论计算的最优扩散角;采用优化渐变扩散角,可使水力损失进一步减小;矩形流道断面以正方形为最优,且存在最优角圆,使单位长流道沿程水力损失最小。成果对减小出水流道水力损失,实现泵装置优化设计,提高泵装置效率有重大意义。     

大型双向流道泵装置优化与试验研究

引江济淮工程枞阳泵站采用双向流道立式轴流泵装置型式。根据枞阳泵站的控制性尺寸,对双向进出水流道进行了参数化数学建模。基于Isight多学科优化平台,搭建了双向进出水流道的水力优化设计平台。采用多岛遗传算法对优化目标进行寻优,得到了高效双向进出水流道型线优化结果,并与TJ04-ZL-20水力模型匹配得到高效泵装置。通过泵装置模型试验可知,枞阳泵站模型泵装置在装置扬程为5.67 m时,泵装置最高效率达到78.59%,已达到了单向立式泵装置的较高水平,为双向流道立式泵装置的进一步推广和应用提供了参考。     

轴流泵流道优化设计及其装置模型试验验证

本文对国内某泵站肘型进水流道进行了优化设计,通过调整宽度Bj、长度XL、高度Hw、流道喉部高度Hk、直线段长度Xz1、弯曲段长度Xw、过渡圆弧段长度Xr、流道进口高度Hj、流道上板倾斜角α、流道底板倾斜角β等参数进行了多个方案的对比,运用CFD数值分析确定最优方案,该项目在扬州大学装置模型试验台进行了装置模型试验验证。     

双流道泵叶轮轴面图的数学模型

利用几何法推导出双流道泵叶轮轴面图前，后盖板型线方程以及轴面图流道中线方程，首次给出了双流道泵叶轮轴面图流道中线分点的计算方法。研究结果将会对双流道泵叶轮水力设计CAD软件的开发和手工绘型提供很大帮助。     

High-efficiency design optimization of a centrifugal pump

Design optimization of a backward-curved blades centrifugal pump with specific speed of 150 has been performed to improve hydraulic performance of the pump using surrogate modeling and three-dimensional steady Reynolds-averaged Navier-Stokes analysis. The shear stress transport model was used for the analysis of turbulence. Four geometric variables defining the blade hub inlet angle, hub contours, blade outlet angle, and blade angle profile of impeller were selected as design variables, and total efficiency of the pump at design flow rate was set as the objective function for the optimization. Thirty-six design points were chosen using the Latin hypercube sampling, and three different surrogate models were constructed using the objective function values calculated at these design points. The optimal point was searched from the constructed surrogate model by using sequential quadratic programming. The optimum designs of the centrifugal pump predicted by the surrogate models show considerable increases in efficiency compared to a reference design. Performance of the best optimum design was validated compared to experimental data for total efficiency and head.     

Effects of meridional flow passage shape on hydraulic performance of mixed-flow pump impellers

During the process of designing the mixed-flow pump impeller, the meridional flow passage shape directly affects the obtained meridional flow field, which then has an influence on the three-dimensional impeller shape. However, the meridional flow passage shape is too complicated to be described by a simple formula for now. Therefore, reasonable parameter selection for the meridional flow passage is essential to the investigation. In order to explore the effects of the meridional flow passage shape on the impeller design and the hydraulic performance of the mixed-flow pump, the hub and shroud radius ratio (HSRR) of impeller and the outlet diffusion angle (ODA) of outlet zone are selected as the meridional flow passage parameters. 25 mixed-flow pump impellers, with specific speed of 496 under the design condition, are designed with various parameter combinations. Among these impellers, one with HSRR of 1.94 and ODA of 90° is selected to carry out the model test and the obtained experimental results are used to verify accuracies of the head and the hydraulic efficiency predicted by numerical simulation. Based on SIMPLE algorithm and standard k-ε two-equation turbulence model, the three-dimensional steady incompressible Reynolds averaged Navier-Stokes equations are solved and the effects of different parameters on hydraulic performance of mixed-flow pump impellers are analyzed. The analysis results demonstrate that there are optimal values of HSRR and ODA available, so the hydraulic performance and the internal flow of mixed-flow pumps can be improved by selecting appropriate values for the meridional flow passage parameters. The research on these two parameters, HSRR and ODA, has further illustrated influences of the meridional flow passage shape on the hydraulic performance of the mixed-flow pump, and is beneficial to improving the design of the mixed-flow pump impeller.     

Effects of Blade Number on Characteristics of Centrifugal Pumps

The blade number of impeller is an important design parameter of pumps,which affects the characteristics of pump heavily.At present,the investigation focuses mostly on the performance characteristics of axis flow pumps,the influence of blade number on inner flow filed and characteristics of centrifugal pump has not been understood completely.Therefore,the methods of numerical simulation and experimental verification are used to investigate the effects of blade number on flow field and characteristics of a centrifugal pump.The model pump has a design specific speed of 92.7 and an impeller with 5 blades.The blade number is varied to 4,6,7 with the casing and other geometric parameters keep constant.The inner flow fields and characteristics of the centrifugal pumps with different blade number are simulated and predicted in non-cavitation and cavitation conditions by using commercial code FLUENT.The impellers with different blade number are made by using rapid prototyping,and their characteristics are tested in an open loop.The comparison between prediction values and experimental results indicates that the prediction results are satisfied.The maximum discrepancy of prediction results for head,efficiency and required net positive suction head are 4.83%,3.9% and 0.36 m,respectively.The flow analysis displays that blade number change has an important effect on the area of low pressure region behind the blade inlet and jet-wake structure in impellers.With the increase of blade number,the head of the model pumps increases too,the variable regulation of efficiency and cavitation characteristics are complicated,but there are optimum values of blade number for each one.The research results are helpful for hydraulic design of centrifugal pump.     

Experimental study of the influence of flow passage subtle variation on mixed-flow pump performance

In the mixed-flow pump design, the shape of the flow passage can directly affect the flow capacity and the internal flow, thus influencing hydraulic performance, cavitation performance and operation stability of the mixed-flow pump. However, there is currently a lack of experimental research on the influence mechanism. Therefore, in order to analyze the effects of subtle variations of the flow passage on the mixed-flow pump performance, the frustum cone surface of the end part of inlet contraction flow passage of the mixed-flow pump is processed into a cylindrical surface and a test rig is built to carry out the hydraulic performance experiment. In this experiment, parameters, such as the head, the efficiency, and the shaft power, are measured, and the pressure fluctuation and the noise signal are also collected. The research results suggest that after processing the inlet flow passage, the head of the mixed-flow pump significantly goes down; the best efficiency of the mixed-flow pump drops by approximately 1.5%, the efficiency decreases more significantly under the large flow rate; the shaft power slightly increases under the large flow rate, slightly decreases under the small flow rate. In addition, the pressure fluctuation amplitudes on both the impeller inlet and the diffuser outlet increase significantly with more drastic pressure fluctuations and significantly lower stability of the internal flow of the mixed-flow pump. At the same time, the noise dramatically increases. Overall speaking, the subtle variation of the inlet flow passage leads to a significant change of the mixed-flow pump performance, thus suggesting a special attention to the optimization of flow passage. This paper investigates the influence of the flow passage variation on the mixed-flow pump performance by experiment, which will benefit the optimal design of the flow passage of the mixed-flow pump.     

叶轮进口宽度对液力透平性能的影响

针对叶轮进口宽度对液力透平性能影响规律的认识不足问题,建设了一开式液力透平实验台,对一单级液力透平进行了实验研究,得到了该比转速液力透平的外特性曲线。采用结构化网格技术对液力透平进行了全流场数值计算与分析,数值与实验相结合,验证了数值计算的准确性。对不同进口宽度透平叶轮的数值计算结果分析表明,随着透平叶轮进口宽度的增加最高效率点向大流量偏移,大流量时的效率逐渐增加;对于一定几何参数组合的液力透平,存在最佳叶轮进口宽度使液力透平最优工况点效率最高;透平的流量扬程曲线随叶轮进口宽度的增加变得更加平坦;透平的轴功率变化相对较小。     

基于流场仿真的多路阀流道结构优化

采用流体仿真软件对多路换向阀的桥路进行流场仿真,并通过速度场和压力场的对比,指出了多路阀桥路流道结构的优化方向和优化结果.仿真结果表明,在桥路结构转折处采用圆弧过渡,能够大大减少压力损失、平缓流场,为液压元件流道结构设计提供了一种工程设计的新途径,具有广阔的应用前景.     

立式轴流泵装置流道内部流动特性及消涡试验

采用数值计算和高速摄影技术研究分析了立式轴流泵装置的箱涵式进水流道水力特性,数值预测的附底涡与高速摄影捕捉到的附底涡均发生于喇叭管正下方,各工况时附底涡的运动轨迹较为一致,表明了数值计算的有效性。相比无消涡锥的进水流道,有消涡锥时进水流道出口断面的轴向速度分布均匀度平均提高了0.423%,速度加权平均角平均提高0.397°。设计的复合型消涡短锥可消除各工况运行时箱型进水流道附底区的涡带,提高泵装置运行的安全可靠性。对于箱涵式进水流道,为保证泵装置的安全稳定运行,需在流道附底区设置消涡装置。     

基于MATLAB的水压溢流阀动态特性仿真

分析并建立了先导式水压溢流阀动态特性的数学模型,并在某个稳定工作点对微分方程进行了线性化处理和拉氏变换。采用MATLAB中的Simulink软件对数学模型的方框图进行仿真,得出主阀阻尼孔直径d1、主阀进口受控容积V0、导阀入口容积V1、主阀芯上腔容积V2的大小均对阀的动态性能有较大影响。分析结果对先导式溢流阀的优化设计有一定的指导意义。     

基于流场仿真的多路阀流道结构优化设计

采用流体仿真软件对多路换向阀的桥路进行流场仿真,并通过速度场和压力场的对比指出了桥路流道优化方向和优化结果,为液压元件流道结构设计提供了一种工程设计的新途径.