固液两相双流道泵的设计与试验研究

提出了双流道固液混合输送离心泵的水力设计方法,研制了2台输送大直径固体颗粒的双流道离心泵,并进行了清水试验、清淤试验及输送卵石的试验研究。试验结果表明双流道泵不仅具有较好的水力性能,而且在清淤及输送较大的固体颗粒时同样具有良好的通过能力和较高的效率,证实了本文提出的固液两相双流道离心泵的设计方法是合理可行的,对固液两相离心泵的进一步研制和推广应用有一定的指导意义。     

双吸双流道泵固液两相流动特性分析

为研究双吸双流道泵的固液两相流动规律,本文基于CFD性能预测方法,计算泵在不同沙粒直径、不同沙粒浓度、不同流量工况的内部流动规律与外部特性曲线,并与单相流进行对比分析。研究结果表明:含沙多相流,流道中的压力梯度更大,压差分布更明显;流道内的脱流损失更严重,漩涡区域更明显,叶轮出口与蜗壳进口的动静耦合作用更剧烈;固相颗粒主要集中在叶轮的上下盖板处以及靠近蜗壳出口侧的流道区域;叶轮流道进口处的颗粒相对较少,出口处的颗粒相对较多;颗粒直径的变化对固相的离析作用明显,随着泥沙直径与流量的增大,泵的进出口总压差减小,随着泥沙浓度的增大,泵进出口总压差增大。     

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。     

小粒径固液两相流在旋流泵内运动的数值模拟

为了分析旋流泵内固液流动特性,采用Eulerian多相流模型,扩展的标准κ-ε湍流方程与SIMPLEC算法,应用流体动力学软件FLUENT对旋流泵叶轮内固液两相湍流进行了数值模拟。分析了多种粒径及浓度条件下的固相体积浓度分布规律。在旋流泵叶轮固液两相流动中,固体颗粒还是主要集中于叶轮工作面,因而会加剧叶轮工作面磨损破坏速度。数值结果表明,泥沙颗粒直径变大以及泥沙浓度的加大都会使旋流泵扬程和效率下降,其中浓度的变化对扬程和效率的影响更明显。     

两相流离心泵水力输送性能计算分析

为探索一台固液两相流离心泵的水力性能与磨损特性,基于代数滑移混合物模型(Algebraic slip mixture model,ASMM)对其内部流场进行三维不可压缩定常流动数值计算,其中转子与定子之间的动静耦合采用"冻结转子法"实现。多相位定常流动计算结果与水力试验结果的对比确定最佳的转动位置,并确认数值计算方法的准确性。预测结果表明,颗粒属性对模型泵水力性能影响的次序为固相体积分数、颗粒密度和粒径。随着颗粒直径、密度和固相体积分数的增加,预测扬程均下降;效率总体上也呈现下降趋势,但在固相体积分数为10%时输送效率最高。在靠近隔舌的叶轮出口处存在由低、中、高三种速度组合的双剪切层射流—尾流结构。总体而言,模型泵叶片吸力面的磨损程度比压力面更为严重。固相体积分数对叶片表面磨损程度的影响比较明显,颗粒密度影响较小,颗粒直径仅对吸力面磨损程度影响显著,对压力面影响不明显。     

轻型化工渣浆泵叶轮轴向间隙泄漏流及磨损特性分析

针对渣浆泵的泵腔及叶轮磨损问题,基于DPM模型对LCF100/350型化工渣浆泵叶轮轴向叶顶间隙泄漏流及磨损特性进行数值分析。在清水介质条件下对泵轴向叶顶间隙泄漏流结构及泵外特性进行模拟,并与试验结果进行对比分析;固液两相流分析中液相采用k-ε Realizable湍流模型,固体颗粒相采用离散相模型,分析了叶轮轴向叶顶间隙处固液两相流场分布及其前泵腔磨损特性。分析结果表明:叶轮轴向叶顶间隙泄漏流与主流相互作用,在叶轮流道内产生泄漏涡;泵体磨损强度分布呈螺旋线分布,与实际的泵体磨损情况完全一致。研究结果为渣浆泵的磨损特性的优化提供了理论依据。     

离心泵叶轮内部液固两相湍流的数值模拟

为了深入了解离心泵叶轮内液固两相流流态，利用商用软件FLUENT6．2对叶轮内部不可压液固两相流动进行了数值模拟，获得了叶轮内的相对速度分布、压力分布以及固相浓度分布。研究结果表明。由于固体颗粒的存在将对液相相对速度场产生影响，造成泵输送液固两相流时的扬程比输送单相流时有所下降。     

泵抽送固液混合物时的输送效率

一、前言现场运行和室内试验均表明,当泵抽送含有固体颗粒的固液混合物时,共性能发生变化。图1是一台4PN杂质泵抽送粗砂浆时的试验结果。从图1可以看出,在同一输送流量下,泵抽送的固液混合物的浓度C_w越高,需要的功率就越大。但这并不意味着泵抽送的固液混     

固相粒径对深海采矿矿浆泵空化特性影响的规律

针对深海采矿矿浆泵空化现象,研究固相粒径对其空化特性的影响。根据空化核子理论、质能方程建立气液两相之间的质量转换方程,运用Fluent软件和Singhal et al的空化模型对在不同固相颗粒粒径工况下的深海采矿矿浆泵进行稳态全流道空化仿真研究。分析叶轮叶片背面压力和气相体积分布规律,对不同区间气相体积分数进行统计,计算出不同颗粒粒径下泵的空化余量和扬程。研究结果表明:随着固相颗粒的增大,叶轮叶片背面入口处的低压区面积逐渐扩展,泵的空化现象趋于严重,扬程下降。当粒径为25 mm时空化余量陡降至最低1.11m,空泡分布广泛,部分区域体积分数高达0.9;粒径从10 mm到25 mm的过程中扬程下降了8.67 m;继续增大粒径,泵的空化性能有所提升,空化余量稳定在3.5 m,但泵的扬程在空化和颗粒磨损共同作用下继续下降至65.3 m。     

叶片型线改型对渣浆泵水力性能及磨损特性的影响

渣浆泵工作过程中,浆液中的硬质固体颗粒会对泵壁面造成强烈的冲蚀磨损,导致渣浆泵效率降低,使用寿命缩短。为了解决渣浆泵效率较低、磨损速度过快等问题,采用变角螺旋线法(VASM),对渣浆泵叶轮叶片型线进行了改型设计,研究了不同颗粒粒径、浓度、密度等对不同型线渣浆泵性能的影响。首先,介绍了变角螺旋线方法和离散相模型,对数值计算模型进行了验证;然后,在叶轮前、后盖板和叶片型线不变的前提下,采用变角螺旋线法对LC100/350型渣浆泵叶片进行了改型设计;采用雷诺时均N-S方程、RNG k-ε湍流模型和SIMPLE耦合算法和离散相模型(DPM)对渣浆泵内部固液两相流动进行了模拟,以额定工况下泵的扬程、效率、磨损强度为改进性能指标,评估了改进效果;最后,通过CFD数值模拟方法,分析和对比了改型后各种叶型的渣浆泵扬程、效率和叶轮磨损强度。研究结果表明：相对于渣浆泵叶轮的原叶型,采用变角螺旋线法设计的渣浆泵叶轮叶片能够明显地提高渣浆泵的效率,降低叶轮的磨损强度,且对渣浆泵的扬程影响较小。虽然颗粒粒径和浓度的增大会使效率降低,磨损强度增大,颗粒粒径和颗粒浓度的变化不影响最优叶型的选择;综合考虑渣浆泵的水力...     

Numerical simulation and analysis of flow characteristics in the front chamber of a centrifugal pump

We performed numerical simulations to study the flow characteristic in a centrifugal pump based on the RANS equations and the RNG k-ε turbulent model. The flow field, including the front and back pump chambers, the impeller wear-ring, the impeller passage, the volute casing, the inlet section and outlet section was calculated to obtain accurate numerical results of fluid flow in a centrifugal pump. The flow characteristic was studied from the internal flow structure in pump chambers, the radial velocity at impeller outlet as well as the pressure inside of the pump, the circumferential velocity and the radial velocity in front pump chamber. The variation of flow parameters in internal flow versus flow rate in the centrifugal pump was analyzed. The results show that the overall performance of the pump is in good agreement with the experimental data. The simulation results show that the distribution of flow field in the front pump chamber is axial asymmetry. The energy dissipation at the impeller outlet is larger than other areas. The distribution of the circumferential velocity and that of radial velocity are similar along the axial direction in the front pump chamber, but the distribution of flow is different along the circumferential and the radial directions. It was also found that the vorticity is large at the impeller inlet compared with other areas.     

变转速工况下离心泵蜗舌处压力波动的试验研究

对某一单吸离心泵在变转速工况下蜗舌处的压力波动进行了测量与分析。该离心泵的叶轮为半开式叶轮并具有背叶片,它由原叶轮车削后得到,从而使得叶轮出口离蜗舌距离较大。结果显示:随着转速的提高,离心泵的流量及效率线性增大,而扬程以二次曲线形式增加。该离心泵蜗舌附近的压力波动频谱以叶轮转动频率整数倍的离散分量为主,特别是叶片通过频率及其二次谐波。最大波动分量的幅度占参考动压ρv22/2(v2为叶轮出口周向速度)的0.5%左右。随着转速的增大,压力波动的增加速度比转速提高速度快,且宽频波动幅度的提高比离散分量显著。另外,频谱分量中存在叶轮转动频率非整数倍的离散分量,以及与转速无关而取决于流体系统固有振动特性的离散分量。     

Performance study based on inner flow field numerical simulation of magnetic drive pumps with different rotate speeds

Magnetic drive pump has gotten great achievement and has been widely used in some special fields.Currently,the researches on magnetic drive pump have focused on hydraulic design,bearing,axial force in China,and a new magnetic drive pump with low flow and high head have been developed overseas.However,low efficiency and large size are the common disadvantages for the magnetic drive pump.In order to study the performance of high-speed magnetic drive pump,FLUENT was used to simulate the inner flow field of magnetic drive pumps with different rotate speeds,and get velocity and pressure distributions of inner flow field.According to analysis the changes of velocity and pressure to ensure the stable operation of pump and avoid cavitation.Based on the analysis of velocity and pressure,this paper presents the pump efficiency of magnetic drive pumps with different rotated speeds by calculating the power loss in impeller and volute,hydraulic loss,volumetric loss,mechanical loss and discussing the different reasons of power loss between the magnetic drive pumps with different rotated speeds.In addition,the magnetic drive pumps were tested in a closed testing system.Pressure sensors were set in inlet and outlet of magnetic drive pumps to get the pressure and the head,while the pump efficiency could be got by calculating the power loss between the input power and the outlet power.The results of simulation and test were similar,which shows that the method of simulation is feasible.The proposed research provides the instruction to design high-speed magnetic drive pump.     

双流道泵内非定常流动数值模拟及粒子图像测速测量

为探讨双流道泵内部的非定常流动机理,采用Fluent软件,基于滑移网格技术、 湍流模型计算了一双流道泵在不同工况下的内部流动,并将计算结果与粒子图像测速仪(Particle image velocimeter, PIV)实测结果进行比较。结果表明：计算所得双流道泵内部流场符合叶轮机械内部流动的一般规律,且与PIV实测结果总体变化趋势一致;由于双流道泵结构特殊,其进口处的流动状态与普通叶轮相差较大,出口处的流动状态与普通叶轮类似;叶轮进口处,流体基本沿流道吸力面流动,流道工作面上的相对速度很小,存在严重的脱流和旋涡;叶轮出口处,压力面和吸力面的速度趋于相等,射流—尾迹现象并不明显;由于叶轮—蜗壳动静干涉,两个叶轮流道内的静压分布有所不同;同一流道内,静压随着半径的增加而逐步增大,压力面侧静压大于吸力面侧;蜗壳流道内静压随半径增大,最大静压值在隔舌处。此项研究不仅加深了人们对双流道泵内非定常流动图画的理解,从而进一步完善双流道泵设计方法,同时也可为其他类型泵的内流研究提供借鉴。     

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.     

Comparison of cavitation prediction for a centrifugal pump with or without volute casing

Cavitation may not only cause head and efficiency breakdown of hydraulic machines but also generate other unfavorable phenomena such as noise and vibration. Therefore, the accurate prediction of cavitation development is important for various pump applications. In this paper, two numerical models, namely, models A and B, are applied to simulate the turbulent cavitating flows inside a centrifugal pump to investigate the effect of calculation domain on the prediction accuracy of cavitation performance for hydraulic machines. Model A has a calculation domain with volute casing, whereas model B has a single blade-to-blade flow passage without volute casing. Steady simulations of cavitating flow in the pump have been conducted based on the shear stress transport k-ω turbulence model and the homogeneous cavitation model. Both models A and B predicted that the pump performance decreases with decreasing cavitation number. Experimental results show that model B can predict better the critical cavitation number at the best efficiency point compared with model A, which is the full flow passage model. Internal flow investigations indicate that an asymmetrical feature of cavitating flow exists when the calculation domain with volute casing is applied. The asymmetrical cavitation development in different blade-to-blade flow passages for model A results in an over-estimation of the decrease in pump performance because of the interaction between the impeller blade and the tongue of the volute casing. A simple calculation domain without volute casing is preferred for steady cavitation prediction in pumps rather than the full flow passage with volute casing because the former has better convergence, less resource requirements, and lower time consumption.     

混流式核主泵叶轮叶片厚度分布规律对能量性能的影响

采用数值计算方法,开展混流式核主泵叶轮叶片自前盖板至后盖板方向厚度分布规律对能量性能影响的研究。通过对5种具有不同厚度分布规律叶片的叶轮进行比较分析,探索最佳叶片厚度比值和其对叶片表面静压力分布规律的影响。结果表明:当叶片后盖板处厚度与前盖板处厚度比值L=1.5时,叶轮的水力效率达到最高,当L=1.25时叶片做功能力低,叶轮内能量损失大,水力效率较低;在小流量工况下,随着比值L的增加,相同流量下扬程和水力效率都随之升高;在大流量工况下,扬程和水力效率都随着L的增大而降低;叶轮流道内压能沿着前盖板至后盖板方向增大并且最大压能位置向中间移动。