流体激振力对高速泵转子振动特性的影响研究

对高速泵三维流场进行了非定常计算,分析了高速泵内的压力分布情况。研究了高速泵叶轮上的稳态径向力和脉动径向力,分析了流体激振力对高速泵叶轮系统的振动及其轴心轨迹的影响。计算结果表明:泵内部流场的压力分布合理,稳态作用力的计算符合实际数据;瞬态作用力与叶轮和隔舌的干涉流动有很大关系;在脉动激振力作用下,泵转子振动响应谱图中出现了脉动激振力的频率及其谐波频率。     

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。     

Investigation of the correlation between noise & vibration characteristics and unsteady flow in a circulator pump

Circulator pumps have wide engineering applications but the acoustics, vibration and unsteady flow structures of the circulator pump are still not fully understood. We investigated the noise and vibration characteristics and unsteady flow structures in a circulator pump at different flow rates. Three-dimensional, unsteady RANS equations were solved on high-quality structured meshes with SST k-ω turbulence model numerically. Measurements were made in a semi-anechoic chamber to get an overview of noise and vibration level of a pump at different flow rates. The 1/3 octave-band filter technique was applied to obtain the explicit frequency spectra of sound, pressure fluctuations and vibration signals and their principal frequencies were identified successfully. The air-borne noise level of the designed condition is lower than that of the off-design conditions, and the highest sound pressure level is found at part-load condition. The acoustic emission from the pump is mainly caused by unsteady flow structures and pressure fluctuations. In addition, both the link between airborne noise and pressure fluctuation, and the correlation between vibration and unsteady hydrodynamic forces, were quantitatively examined and verified. This work offers good data to understand noise and vibration characteristics of circulator pumps and the relationships among the noise, vibration and unsteady flow structures.     

单流道泵叶轮水力径向力的数值计算

将叶片和蜗壳作为一个整体,采用边界元法对单流道泵内部三维非定常势流流动进行了数值模拟,计算了泵叶片表面压力,并在此基础上进一步计算了叶轮上所受的水力径向力及其变化趋势,对提高泵的运行稳定性具有指导意义。     

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。     

Numerical and experimental investigations on the hydrodynamic radial force of single-channel pumps

In order to clarify the generation mechanism and characteristics of hydrodynamic radial force in single-channel pumps, the transient flow in three single-channel pumps was analyzed by computational fluid dynamics (CFD). The three pumps had the identical impeller but with a spiral volute (model 1), a circular volute (model 2), and a torus (model 3). Experiments on pump performance were performed and high frequency pressure sensors were mounted in the spiral volute to measure pressure distribution in the volute of model 1. It indicates that the numerical results are approximately consistent with the experimental results. The radial force is mainly caused by the pressure acting on the blade. The impeller radial force in model 1 was the largest while the model 3 was the smallest, as it is not affected by rotor stator interaction, and rotor stator interaction plays a vital role in the shock load of pumps. The radial forces of different rotational speed were analyzed and indicated that Reynolds number has little influence on the radial force coefficient C_F. The dominant frequency of the radial force on the impeller is the rotational frequency of impeller for all rotational speeds. Moreover, the amplitude of the radial force fluctuations increased with increasing flow rate in model 2, but the change was not obvious with the increasing of flow rate in model 3, while at lower flow rate the largest amplitude of the radial force fluctuations was presented in models 1.     

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.     

混流泵径向间隙对内部非定常流场影响的分析

采用调整混流泵径向间隙的方法,设计了蜗壳基圆直径为280、290、300mm的计算模型,并对其进行了定常和非定常计算.通过对3种模型进行非定常数值计算,得到了不同基圆直径混流泵的压力脉动特性并对其进行比较分析.结果表明:叶轮旋转时叶片和隔舌的动静干涉作用导致蜗壳近壁面各监测点的压力脉动具有明显的周期性;在相同流量下,径向间隙越小,监测点频域振幅越大;隔舌处监测点压力脉动幅度大于其他监测点幅度.对基圆直径为290mm的泵进行数值模拟与外特性试验研究,泵模拟效率为82.3%,试验效率为80%,模拟效率比试验效率高2.3%.对比两者结果可知:数值模拟的结果是可信的.     

单流道泵内部非定常流动特性

将叶片和蜗室作为一个整体,对单流道泵内部三维非定常流动特性进行研究,经分析提出了单流道泵内部三维非定常势流流动和三维非定常湍流流动的数值模拟方法,分别计算了单流道泵内部的速度场、压力场和叶片表面的压力分布,对进一步研究单流道泵内部流动具有重要意义。在此基础上计算了叶轮所受的径向力及其变化趋势,为提高单流道泵运行稳定性提供了理论依据。此外还计算了扬程、平均水功率和效率,并与试验值作对比。尽管忽略粘性使得势流计算得到的速度场在蜗壳的局部区域出现反方向流动,从而导致叶片压力面压力沿展向波动变化,但其性能曲线与试验值变化趋势一致,粘性计算结果与试验值相比,精度较高。     

离心压缩机机壳在基频气动力激励下的振动噪声研究

研究了离心压缩机机壳在内部基频气动力激励下的振动辐射噪声。考虑机壳与轮盘、轮盖之间的间隙,采用SSTk-co湍流模型模拟了离心压缩机的整机三维非定常流场,得到蜗壳内表面的脉动压力,然后将脉动压力的基频部分加载到蜗壳上,模拟离心压缩机蜗壳在非定常气动力激励下的振动噪声。研究表明：机壳内壁面基频压力脉动主要分布在无叶扩压器靠近叶轮出口一侧;机壳主要基频振动噪声源位于蜗壳靠近出口管道一侧;该离心压缩机机壳基频振动位移幅值很小,最大振动位移仅为11．8×10^-9m,因此可以忽略机壳的基频振动对离心压缩机运行安全性的影响。     

液电混合直线驱动系统耦合特性及位置控制

液压系统与电-机械系统是广泛应用于航空航天、工业、非道路移动机械等领域的两种不同驱动方案。在实际中,两者通常单独使用,电-机械驱动方案能效高,但承载能力弱,液压驱动方案功率密度大、动态响应快,但能量效率低。为此,结合两个驱动方案优点,集成设计电-机械执行器与液压缸,构建一种新型液电混合直线驱动系统,分析系统工作原理及两个非相似驱动子系统耦合特性、力纷争现象及其影响。在此基础上,提出一种电-机械驱动单元运动控制与液压驱动单元力控制的调控方案。研究结果表明,采用所提调控方案可减轻两个非相似驱动子系统耦合作用,在液压阀低压损的同时,可获得良好的位置控制特性。新型液电混合直线驱动系统将为液压系统和电-机械系统的进一步发展提供新思路。     

PREDICTION OF PUMP CHARACTERISTICS ACCORDING TO GEOMETRICAL PARAMETERS OF IMPELLER AND VOLUTE CASING

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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.     

Effect of the blade loading distribution on hydrodynamic performance of a centrifugal pump with cylindrical blades

The effect of the blade loading distribution on head, radial force and pressure pulsation of a low specific-speed centrifugal pump with cylindrical impeller blades were investigated in the present study. Blade shapes were obtained by adopting the 1D inverse design method, impellers with different blade loading curves were obtained while the distribution of the blade loading was carefully tailored. Threedimensional URANS simulation method based on the Shear stress transport (SST) k-ω turbulence model was employed for the analyzation of flow patterns. Numerical results including the pressure distribution and velocity profile were validated by comparing with the available experimental data, and an acceptable agreement was obtained. Three typical parameters of the blade loading curve, including the location of the fore-loading point (m_pre), location of the aft-loading point (m_post) and slope of the rectilinear segment (K), were analyzed. Results showed that the well-designed blade loading curve, such as the fore-loading impeller, can effectively reduce the pressure pulsation amplitude and the radial force. The significant effect of the variation of the aft-loading point on pump hydrodynamic performance was also investigated. Meanwhile, pressure and velocity distributions at different slopes of the blade loading curves show that the fore-loading impeller produces more uniform flow issuing from the impeller than that of the pump with aft-loading impeller, thus reduces the radial force and pressure pulsation of the pump.     

基于集中参数法内啮合齿轮泵AMESim模型的建模方法与仿真研究

通过集中参数的建模方法,在AMESim平台上搭建了内啮合齿轮泵的流量动态子模型和齿轮受到的径向液压力子模型,分析了泵的流量、压力脉动以及齿轮径向力特性。得出影响脉动的因素除了几何体积的变化外,还有油液的可压缩性、泵的内泄漏、过渡区流量回冲等因素,各个因素的综合作用导致了泵的流量脉动相比几何流量脉动有所升高。同时得出作用在齿轮上的液压径向力大小和方向都是周期性变化的,并且在不同压力等级下,主动齿轮上的合力方向随着压力的升高向顺时针方向偏转,而在内齿圈上,不同压力下的合力方向值曲线几乎都重合在一起。     

离心泵蜗壳内非定常流动特性的数值模拟及分析

基于RNG k-ε湍流模型和Zwart-Gerber-Belamri空化模型,对离心泵内部非空化和空化工况下的非定常流动特性进行数值模拟,分析空化模型中凝结项经验系数对数值模拟结果的影响,并根据试验结果修正离心泵空化流动数值模拟中凝结项经验系数;数值模拟得到的离心泵扬程随有效空化余量的变化曲线与试验结果吻合较好,验证数值计算模型和方法的准确性和可靠性。数值模拟结果表明：离心泵非定常流动中,非空化、临界空化和充分发展空化工况下,蜗壳内监测点的压力脉动主频均为叶片通过频率;空化对离心泵蜗壳内压力脉动的影响较大,非空化时压力脉动最大幅值在蜗舌处,空化时压力脉动最大幅值在第1断面附近,其原因是离心泵出现空化时第1断面处旋涡强度增强,且随时间变化剧烈,对流动产生强烈扰动。     

超低比转速复合式离心泵内部流动特性分析

为研究超低比转速复合式离心泵内部流动特性,以一台比转速为16、半开式复合叶轮离心泵为研究对象,应用ANSYS-Fluent19R1软件对模型泵进行三维全流场数值模拟计算,得出泵内部流场及作用在叶轮、蜗壳上的径向力分布规律。结果表明:在不同流量工况下,随着流量的增加,在隔舌附近出现较大的压力梯度;在长叶片与短叶片相间隔流道内低速区面积较大、叶轮出口处分布较多的旋涡;当流量从0.2倍增加至1.8倍额定流量时,作用在蜗壳上的径向力幅值逐渐减小,作用在叶轮上的径向力幅值先减小后增加,在1.0倍额定流量时径向力幅值达到最小,而后增大。为超低比转速复合式离心泵的设计优化提供参考。     

多级离心泵扬程预测及内部流场数值模拟

为了研究多级离心泵的性能及其内部流场分布,采用SST k-ε湍流模型对原型泵的首级、第二级及第三级叶轮进行定常和非定常数值模拟计算,分析其外特性、内部流场和压力脉动.研究表明,通过前三级叶轮的扬程能较准确地预测原型泵的扬程.不同流量工况下隔舌处均易出现低压区域,大流量工况蜗壳出口近隔舌处也易出现局部低压区和高压区,隔舌...     

离心泵流动诱导噪声的数值预测

通过计算流体力学(Computational fluid dynamics,CFD)结合声振耦合求解方法针对一离心泵所产生的流动诱导噪声在泵壳外部的辐射情况进行数值预测。蜗壳内壁面上的非定常压力脉动监测值显示出蜗舌附近区域的脉动幅值较大,而在远离蜗舌位置处的脉动相对变化较小,在叶片扫掠频率及其谐频下的压力脉动要明显高于其他频率。通过声振耦合计算之后得到的泵壳外部声场辐射结果来看,当斯特劳哈尔数Sr=4时,由于该处所对应的压力脉动频率与泵壳结构的第四阶固有频率接近,可能会在声场与结构之间发生小幅共振,进而使得外场辐射噪声较大,也说明泵壳结构的振动模态对声场计算结果影响十分显著。通过外场监测点上叠加后的总声压级结果显示,各点基本上在60 dB上下波动,外场噪声辐射是泵内流体的压力脉动与壳体结构模态综合作用的结果。     

三相活齿泵的理论研究

根据活齿传动原理与活齿泵的工作原理,提出了三相活齿泵的结构原理,推导出了中心轮的齿廓曲线方程,验证了激波器所受的径向液压力完全平衡,分析了三相活齿泵定量与变量形式的流量特性.研究表明,该活齿泵受力对称,液压力平衡,消除了轴承的磨损,流量大,泄漏小,效率高,提高了泵的工作压力,是一种双向泵和变量泵,从理论上讲可以作为液压马达.