低比转数高效率蜗壳泵的开发

为了开发出一种高效率低比转数 (ns<70 )的蜗壳泵 ,总结了比转数ns=60时的两种试验结果 ,进行了叶轮设计和蜗壳设计的优化 ,并进行了新的试验 ,以揭示叶轮与蜗舌之间的流动干扰。结果表明 ,低比转数蜗壳泵不宜采用常规设计 ,进而提出了一种新的设计方法。     

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.     

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。     

CFD investigation of the influence of volute geometrical variations on hydrodynamic characteristics of circulator pump

Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump’s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics(CFD) technology is presented. Five main volute geometrical parametersD3,A8,a0,j0 andRt are selected and 25 different volute configurations are generated by using design of experiments(DOE) method. The 3D unsteady flow numerical simulations, which are based on the SSTk-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parametersD3 andA8 are major influence factors on hydrodynamic characteristics of the pump, whilea0,j0 andRt are minor influence factors. The minimum contribution from bothD3 andA8 is 58% on head, and maximum contribution from bothD3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect toD3/D2 andA8/A10, and fluctuating level of radial force has a quadratic polynomial functional relationship with respect toD3/D2. While for the other volute parametersa0,j0 andRt, no special function has been found related to pressure pulsation and radial force. The presented work could be a useful guideline in engineering practice when designing a circulator pump with low hydrodynamic force.     

前向多叶风机降噪研究

研究了前向多叶风机的降噪问题。通过对叶轮、蜗壳、进风口、蜗舌、挡风板以及靠近蜗舌出口附近蜗壳上打孔等几个方面的分析研究,给出了风机降噪的改进设计。最后通过计算与实验,证明本文提出的方法是合理、可行的。     

Exit flow measurements of a centrifugal pump impeller

Discharge flows from a centrifugal pump impeller with a specific speed of 150 [rpm, m³/min, m] were experimentally investigated. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow, i.e. without interaction of the impeller and the volute. The unsteady flow was measured at the impeller exit and vaneless diffuser using a hot film probe and a pressure transducer. The flow at impeller exit showed pronounced jet-wake flow patterns. The wake, which was on the suction/hub side at high flow rate, became enlarged pitchwisely on both the hub and the shroud side as the flow rate decreases. The pitchwise non-uniformity of the flow rapidly decreased along the downstream and the nonuniformity almost disappeared at radius ratio of 1.18 for medium flow rate. The mean vaneless diffuser flow was reasonably predicted using a one dimensional analysis when an empirical constant was used to specify the skin friction coefficient. The data can be used for a centrifugal pump impeller design and validation of CFD codes and flow modeling.     

高比转数蜗壳式混流泵的设计与试验

采用线性分布的轴面流线速度环量和叶片角度变化规律来设计叶轮,采用圆弧翼型进行固定导叶的设计,蜗壳断面采用非对称断面,进而设计了一叶片可调比转数为564.3的蜗壳式混流泵。应用FLUENT对该泵的内部流动进行了数值模拟并根据模拟结果进行了能量性能预测。内流模拟结果显示该泵内部流动均匀,性能预测结果表明该泵可以满足设计要求。真机性能测试表明该泵在叶片角度为0°时最高运行效率达85.76%,在设计点运行效率要比设计要求高约3%。研究结果对于更高比转数蜗壳式混流泵的设计具有比较重要的指导作用。     

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.     

螺旋离心泵叶轮背叶片对轴向力影响的数值分析

基于相对坐标系下的雷诺时均N-S方程和RNG k-湍流模型,采用非结构化混合网格技术和SIMPLEC算法,以清水为介质,对带有叶轮背叶片的80LN-6型螺旋离心泵进行全三维数值模拟。通过改变叶轮背叶片数目和宽度设计出6种不同螺旋离心泵叶轮方案,对各种方案下泵内流动进行数值模拟,获得螺旋离心泵叶轮无背叶片和不同背叶片数目及宽度下轴向力的变化趋势和规律。通过对外特性试验数据和CFD数值模拟数据对比,间接地验证了数值模拟方法的可靠性。并对6种不同螺旋离心泵叶轮方案模拟数据进行分析,结果表明,螺旋离心泵添加叶轮背叶片之后,轴向力大小发生变化,同时在不同方案中不同工况下轴向力方向也发生改变;背叶片数目、背叶片宽度对于平衡轴向力均存在最优值且对后腔及蜗壳内的压力分布有较大影响。     

旋流泵内颗粒分布特性及对泵性能的影响

基于Eulerian多相流模型和RNG κ-ε两方程湍流模型对旋流泵内的液固两相流场进行了数值模拟,获得了不同粒径、浓度时泵内的颗粒分布特性及对泵性能的影响。研究结果表明:固体颗粒进入泵内后主要集中于无叶腔内,无叶腔中的颗粒分布以泵轴为中心呈现一定的轴对称分布,随着粒径的增大,颗粒在无叶腔内壁面聚集的更加明显,随着浓度的增大,颗粒在无叶腔内的分布规律几乎没有变化,随着流量的增大,无叶腔中心部分颗粒浓度几乎不变的区域扩大;在叶轮内,叶片工作面附近的颗粒浓度要大于叶片背面的;随着粒径及浓度的增大旋流泵的效率会降低,随着粒径的增大泵的扬程会降低。     

双流道泵输送固液介质的水力性能及磨损试验研究

为分析固液混合物对双流道输送泵性能的影响,采用平均粒径为10 mm和36 mm的固体颗粒对双流道泵在不同浓度和流量下开展输送固液两相介质的水力性能试验,并对泵的磨损进行分析。水力试验结果表明,在一定的流量下,随着输送混合物中固体颗粒浓度的增加,入口表压、出口表压、扬程及效率呈递减趋势。 与输送清水时比较,当输送固液两相介质时,随着流量的增大,轴功率上升较快,扬程的下降量在不同流量下几乎相同;效率曲线在不同流量下比输送清水时效率要低,差值随着流量的增大而增大。在同流量同浓度比工况下,泵的进出口压力、扬程和汽蚀性能在输送较大直径固体颗粒时,明显下降。通过对双流道泵磨损的分析表明,叶轮磨损部位主要在前盖板外缘、流道内偏前盖板的流道表面、压力面进口边,压力面的磨损区域呈三角形;泵体的磨损部位主要在周壁、隔舌及泵体口环处。本研究可为固液两相双流道离心泵的理论研究与设计应用提供试验依据。     

特小比转数的后向离心通风机的研究与开发

针对一台比转数为9的前向通风机，保持风机设计参数和叶轮直径不变，改为后向通风机来提高性能。利用气动性能数值预估对叶轮和蜗壳的主要参数进行优化后，再对无叶扩压器的大小和叶轮与蜗壳的相对位置进行优化，减少摩擦损失，最终得到的后向通风机测试结果，全压和效率均提高了11％。     

尺寸限制条件下离心风机蜗壳型线的设计研究

由于暖通空调行业在通风换热系统中的一些产品对于紧凑结构的要求很高,因此前向多翼离心风机及其风道系统的设计常常受到结构尺寸的限制。在实际应用中大量多翼离心风机采用"大叶轮、小蜗壳"结构,造成蜗壳型线与叶轮流动参数的不匹配。为了能够在空间受限的条件下,尽可能设计出相对高效和大风量的前向多翼离心风机,本文对比分析了受限空间下两种思路设计得到的多种蜗壳型线方案,利用数值仿真确定最优方案,并通过实验测试对仿真计算结果进行了验证。在此基础上分析了最优方案内部的流动特征。     

Investigation on Reduction of Pressure Fluctuation for a Double-Suction Centrifugal Pump

Double-suction centrifugal pumps have been applied extensively in many areas,and the significance of pressure fluctuations inside these pumps with large power is becoming increasingly important.In this study,a double-suction centrifugal pump with a high-demand for vibration and noise was redesigned by increasing the flow uniformity at the impeller discharge,implemented by combinations of more than two parameters.First,increasing the number of the impeller blades was intended to enhance the bounding effect that the blades imposed on the fluid.Subsequently,increasing the radial gap between the impeller and volute was applied to reduce the rotor-stator interaction.Finally,the staggered arrangement was optimized to weaken the efficacy of the interference superposition.Based on numerical simulation,the steady and unsteady characteristics of the pump models were calculated.From the fluctuation analysis in the frequency domain,the dimensionless pressure fluctuation amplitude at the blade passing frequency and its harmonics,located on the monitoring points in the redesigned pumps(both with larger radial gap)are reduced a lot.Further,in the volute of the model with new impellers staggered at 12°,the average value for the dimensionless pressure fluctuation amplitude decreases to 6% of that in prototype pump.The dimensionless rootmean-square pressure contour on the mid-span of the impeller tends to be more uniform in the redesigned models(both with larger radial gap);similarly,the pressure contour on the mid-section of the volute presents good uniformity in these models,which in turn demonstrating a reduction in the pressure fluctuation intensity.The results reveal the mechanism of pressure fluctuation reduction in a double-suction centrifugal pump,and the results of this study could provide a reference for pressure fluctuation reduction and vibration performance reinforcement of doublesuction centrifugal pumps and other pumps.     

挖泥泵数值仿真与实测比较

通过求解包括进水管、叶轮、泵体等过流部件在内的水泵流道内的三维稳定雷诺平均Navier-Stokes方程,获得水泵内部的流场分布特征。对计算结果与实测结果进行了对比。表明计算所得流量-扬程曲线与实测值吻合良好;流量．效率曲线在小流量相差较大,在大流量吻合得较好。虽然在部分运行工况模拟计算不是很准确,但计算的各工况压力、速度分布以及整个流道的其它流动特性,对分析挖泥泵的各种流动问题很有帮助。     

侧壁式压水室离心泵的压力脉动特性

压力脉动是引起泵振动的主要因素之一,为有效地降低离心泵内压力脉动水平,提出具有特殊结构的侧壁式压水室。为研究其压力脉动特性,采用FLUENT软件对比转数130的侧壁式压水室离心泵进行数值计算,并将时域信号进行快速傅里叶变换为频域信号,结果如下:由于叶轮和隔舌的动静干涉作用,侧壁式压水室内压力脉动周期性明显,叶频在由压力脉动诱发的振动中占主导作用;由于隔舌位置及结构的变化,叶轮出口处液流与隔舌的直接冲击、干涉作用减弱,因此侧壁式压水室内隔舌附近监测点处的脉动幅值并未明显地高于其他点。与常规螺旋形压水室相比,侧壁式压水室可以大幅地降低泵内压力脉动水平,因此采用侧壁式压水室可以显著地降低由压力脉动诱发的振动,改善泵的振动性能。     

不同叶片数下管道泵内部流动及振动特性的数值与试验研究

为研究不同叶片数下管道泵内部的流动特性及振动特性,采用标准k-ε湍流模型和滑移网格技术,在CFX数值计算软件中,分别对6叶片和7叶片的管道泵内部全流场进行三维非定常数值模拟,计算得到不同流量下叶轮内部流动特性、蜗壳内部静压特性以及叶轮转矩波动特性。对比0.1qV工况下两种叶片数下的数值计算结果,发现6叶片下的“射流-尾迹”效应及静压变化梯度均大于7叶片,6叶片下的转矩波动强度大于7叶片;不同叶片数下,叶轮内部的相对速度变化规律、静压变化规律以及蜗舌附近低压区的发展变化规律与蜗舌和叶轮的相对位置有关。采用振动试验测量不同叶片数下管道泵的振动水平,分析振动试验结果和数值计算结果表明,在不同流量下,6叶片的振动水平高于7叶片,主要在于6叶片具有较强的压力脉动和不稳定流体力的作用;叶频及其倍频是管道泵产生振动的主要激励频率。因此,可以通过优化叶片设计参数(Z,β2,β1)来改善管道泵内部的不稳定流动状态,进而降低振动水平。     

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。     

双吸双流道泵流动特性研究

为探讨双吸双流道泵的内部流动规律,本文基于CFD性能预测方法,计算泵在不同时刻和不同工况下的速度-压力分布,探讨其蜗壳喉部的速度分布和蜗壳内部的压力脉动。研究结果表明:叶轮进口处的流动状态与普通叶轮相差较大,在流道的工作面上存在脱流和旋涡。叶轮流道旋转至隔舌左侧靠近蜗壳出口时,叶轮流道以及蜗壳喉部的速度-压力分布均匀。各监测点为低频振动。此项研究可为进一步优化此类泵提供一定的参考。     

Influence of Cross-Sectional Flow Area of Annular Volute Casing on Transient Characteristics of Ceramic Centrifugal Pump

The annular volute is typically used in a slurry pump to reduce the collisions between solid particles and the volute tongue and to achieve a better resistance to blocking. However, only limited studies regarding annular volutes are available, and there is no systematic design method for annular volutes. In this study, the influence of volute casing cross-sectional flow area on the hydraulic loss, pressure pulsations, and radial force under varying working conditions in a centrifugal ceramic pump are discussed in detail. Experimental tests were conducted to validate the numerical results. The results indicated that, when the volute casing flow area increases, the hydraulic performance decreases marginally under the rated working conditions, but increases at the o-design points, specifically under large flow condition. However, the volute casing with a larger flow area has a wider high-e ciency region. In addition, the increase in the volute casing flow area will decrease the pressure pulsations in the volute, regardless of the working condition, and decrease the radial force on the shaft, therefore, providing an improved pump operational stability. It is anticipated that this study will be of benefit during the design of annular volutes.