旋流泵无叶腔内盐析颗粒湍流脉动特性研究

盐析晶体颗粒脉动特性是研究湍流输运状态下盐析过程的重要问题之一.为探索泵内盐析晶体颗粒湍流脉动规律及其对液相流场的影响,采用相位多普勒粒子速度场仪对旋流式输送泵无叶腔内的盐析湍流流场进行了测量,通过对改变泵运行工况、运行介质温度后颗粒脉动速度分布情况的分析,初步掌握了无叶腔中盐析晶体颗粒的湍流脉动特性;同时,讨论了晶体颗粒存在对液相湍流结构的影响。实验结果表明,随着流量的增加,颗粒的周向、径向及轴向脉动速度相应提高;盐析颗粒脉动速度值随温度发生变化,较高温度时速度脉动也较大;在一定条件下,盐析晶体颗粒表现出抑制湍流的行为。     

旋流泵内部盐析两相流速度场的PDPA实验

以旋流式模型泵内部氯化钠盐析两相流场为研究对象,采用相位多普勒粒子测速仪(PDPA)对该泵在最优工况下的两相速度场进行了测量,给出各相在无叶腔及叶轮内部的三维速度及其对应的脉动速度分布曲线.通过对两相的周向速度、轴向速度及径向速度分布情况的分析,揭示了该型泵内盐析两相流速度场的分布特征.泵内同时存在循环流与贯通流,是强制涡旋和自由涡旋的叠加,与前人提出的流动模型相符;在叶轮进口处,液流已有强力预旋;随着半径增大,两相的周向和轴向速度呈现先增大后减小趋势,而径向速度先减小后增大,对应的脉动速度变化趋势则相反;泵内两相速度及脉动速度有滑移,但差异总体上并不显著.本文的研究有助于进一步认识盐析与流动的关系.     

基于DEM-CFD耦合的泵内颗粒流动特性研究

随着我国加快深海、深地资源的开发力度,对此类应用环境下的液体提升泵的可靠性提出了更高的要求。而泵内固体颗粒引起的磨损破坏是其中一个严重问题。本文基于DEM-CFD耦合方法,针对自开发的两级混流泵研究了颗粒在泵内部与流体相互作用下的流动特性和对泵的磨损规律,并基于该泵分析了不同颗粒形状、颗粒浓度下的运动特性和泵磨损分布,发现颗粒主要沿着叶轮工作面以及导叶凹面运动,且随着浓度增加,磨损速率会逐渐达到一个饱和值。本文分析探讨了颗粒在泵内的流动特性、颗粒与叶轮导叶发生碰撞的形式及磨损严重区域,对设计抗磨损多级混流泵提供了理论支撑。     

基于壁面磨损的渣浆泵内固液两相流动分析

为探究渣浆泵内固液两相流动与过流部件磨损之间的关系,结合计算流体动力学与离散元方法,加入磨损模型,对泵内固液两相流动和过流部件的磨损进行模拟;借助试验结果验证数值模拟方案的物理有效性;考虑固体颗粒尺寸和固相质量分数的影响。结果表明:所建立的数值模拟方案可以较准确地预测泵内磨损的位置及磨损程度;随着固相质量分数和固体颗粒平均直径增加,叶轮和压水室表面的磨损加剧,磨损严重的区域集中在叶片进口边附近和叶片工作面出口处,磨损位置受固相质量分数的影响不明显;法向累积接触能量是导致磨损的关键因素;压水室的磨损程度较叶轮轻,且磨损量分布不均匀。     

热斑旋流对燃气透平高压静叶的影响研究

为了揭示热斑和旋流对燃气透平高压静叶的影响机制,本文运用自主开发的有限体积求解器,对LISA一级半透平受到正对通道中心的热斑旋流影响进行了数值计算研究。本文详细阐述了热斑和旋流在叶片通道内的流动过程,研究了其对燃气透平高压级静叶的温度分布、叶片表面压力分布的复杂影响以及热斑旋流通过静叶通道时热斑形态变化和通道内涡系结构变化。     

旋转离心风机叶轮内两相流动的高速摄影研究

固体颗粒与叶栅的磨擦与碰撞，危及叶轮的可靠性和整体装置的稳定性。为研究风机内气固两相流动，利用自制的图象消转装置，拍摄了旋转风机内部固体颗粒相对于叶轮流道的相对运动轨迹的高速摄影照片，对旋转离心风机内颗粒运动特性、颗粒与叶片的碰撞过程及碰撞恢复特性进行了研究，分析了颗粒对叶片的冲蚀机理并指出改进设计思路。     

非均衡进气双面离心压气机流场差异分析

采用数值方法研究了在蜗壳内部和压气机进口非对称流场的耦合作用下,非均衡进气双面离心压气机周向流场结构的差异。结果表明:后方叶轮进口轴向速度在周向上存在着较大的差异,且其不均匀程度随流量增大而增强。叶轮不同叶片槽道出口射流-尾迹结构也存在差别,蜗壳内高静压区对应的叶片槽道尾迹区域增大。扩压器内周向静压分布形式与蜗壳内部相同,不同半径位置上静压分布的不均匀程度基本相同,但随着流量的减小,不均匀程度减弱。     

离心泵非设计工况内部流动特性研究

以单级蜗壳式离心泵为研究对象,基于RANS进行了全流场的非定常数值计算,探讨了叶轮的非定常流动特征,重点分析了叶轮出口沿轴向变化的圆周面流域内各节点的压力分布特性。结果表明:在叶片压力面及叶片后缘尾迹区发生了剧烈的湍流脉动现象;不同工况下叶轮出口圆周方向的压力系数C_p均在隔舌附近产生极值;额定工况Q/Q_N=1时,叶轮出口圆周方向的压力系数C_p呈稳定周期性分布,随着工况的改变,压力系数C_p沿蜗壳周向分布不均匀性增加;小流量工况下叶轮流域内发生了明显的流动分离现象,流道内产生了较大尺度的分离涡,破坏了叶轮出口圆周方向压力系数C_p的周期性分布特性;叶轮出口圆周压力系数C_p沿中截面两侧的流域内几乎对称分布;在Q/Q_N=0.2小流量工况下,压力脉动频谱图低频段内出现了较多复杂的激励信号,认为这与流域内的分离涡结构具有一定关联。     

旋流泵全流道三维定常流场的数值模拟

本文在计算模型采用分块非结构化六面体网格的基础上,利用雷诺平均N-S方程,标准k-ε紊流模型,结合 SIMPLEC算法,数值模拟了旋流泵的内部流动,得到了旋流泵压力面、吸力面上的压力分布,同时也估算了叶轮的效率, 比较了旋流泵试验性能与数值模拟性能,有助于了解旋流泵的内部流动特性,指导旋流泵的水力设计。     

蜗壳非轴对称性对离心压缩机内部非定常流动影响的数值研究

本文采用非定常数值模拟方法研究了蜗壳几何非轴对称性对离心压缩机内部非定常流场的影响。结果表明:流场的非定常波动主要受叶轮影响。远离蜗壳设计工况时,蜗壳非对称性的影响可传播至叶轮主叶片前缘。蜗壳非对称性对扩压器叶片压力面瞬时压力的影响在小流量和设计流量工况下主要体现叶轮主叶片与分流叶片通过频率的影响,而在大流量工况下叶轮主轴旋转频率也占一定比重。叶轮主叶片压力面的非定常压力波动主要受叶轮主轴旋转频率及其倍频与扩压器叶片通过频率及其倍频的影响。     

离心泵蜗壳内旋涡流动的数值研究

采用"冻结转子法"处理叶轮与蜗壳间动静耦合流动的参数传递和相互干扰问题,研究了蜗壳进口周向非均匀来流对其内旋涡的演化发展的影响。分析表明,叶轮与蜗壳的干扰所造成的蜗壳进口周向流动的不均匀性是非常强烈的,整个蜗壳内的流动是以旋涡形式向出口推进的,且随工况的不同表现不同的演化过程,从而导致蜗壳内较大的流动损失。同时也说明只有考虑蜗壳来流的非均匀性影响,才能准确地模拟其内的旋涡运动。     

A simple acoustic model to characterize the internal low frequency sound field in centrifugal pumps

Conventional centrifugal pumps with volute casing generate fluid-dynamic noise particularly at the so-called blade-passing frequency, which is attributed to the interaction of the flow exiting the pump impeller with the volute tongue. Following previous work by the authors to characterize the effect of that blade–tongue interaction on the tonal sound produced, this paper presents a simple acoustic model for centrifugal pumps that considers ideal sound sources of arbitrary position and properties. The model is to be implemented in a software code that applies it systematically to a pump previously tested at laboratory, until identifying the set of ideal sources that best reproduce the pressure fluctuation measurements. In this model, the ideal sources are assumed to radiate plane sound waves along the impeller channels, volute, and outlet diffuser. The volute was considered to be composed by a succession of slices, each of them equivalent to a linear 3-port acoustic system with individual sound transmission and reflection coefficients. A series of tests was conducted to check the validity of the acoustic model, by applying an external acoustic load onto the pump outlet duct and measuring the noise reflected. The resulting reflection coefficient was in good agreement with the predictions of the acoustic model. Finally, the model was used to investigate the pump internal sound field at the blade-passing frequency when operating at 70% of nominal flow rate. It was concluded that the sound field can be characterized reasonably by a dipole-like source located at the tongue region.     

切线泵整机多相位定常流动数值模拟

本文对一单级切线泵在设计工况进行了多相位定常流动数值模拟,分析了由于叶轮与蜗壳相对位置的变化引起的泵的扬程、叶轮流道内的质量流量、速度场、压力场的变化规律。计算表明,切线泵内流场非常复杂,整机多相位定常流动数值模拟的结果实际上是泵内流场非定常特性在定常计算中的反映,其内部流动呈周期性变化,叶轮流道在不同的位置流动情况差别很大。本次计算为进一步提高切线泵性能、减少水力损失提供了一定的理论依据。     

Energy Loss and Radial Force Variation Caused by Impeller Trimming in a Double-Suction Centrifugal Pump

Impeller trimming is an economical method for broadening the range of application of a given pump, but it can destroy operational stability and efficiency. In this study, entropy production theory was utilized to analyze the variation of energy loss caused by impeller trimming based on computational fluid dynamics. Experiments and numerical simulations were conducted to investigate the energy loss and fluid-induced radial forces. The pump’s performance seriously deteriorated after impeller trimming, especially under overload conditions. Energy loss in the volute decreased after trimming under part-load conditions but increased under overload conditions, and this phenomenon made the pump head unable to be accurately predicted by empirical equations. With the help of entropy production theory, high-energy dissipation regions were mainly located in the volute discharge diffuser under overload conditions because of the flow separation and the mixing of the main flow and the stalled fluid. The increased incidence angle at the volute’s tongue after impeller trimming resulted in more serious flow separation and higher energy loss. Furthermore, the radial forces and their fluctuation amplitudes decreased under all the investigated conditions. The horizontal components of the radial forces in all cases were much higher than the vertical components.     

部分流泵蜗壳壁面静压及外特性研究

本文在设计工况下对部分流泵蜗壳壁面静压进行了实验测量,同时详细研究了部分流泵的外特性。结果表明, 部分流泵内流非定常特性强烈,非定常计算结果能够反映其内流的实质,并且可以准确预测外特性;其瞬时效率的变化主要是由于蜗壳与叶轮的相互作用。本文结论为进一步研究部分流泵内流现象、提高效率、减少水利损失提供了一定的理论依据。     

螺旋轴流式多相泵的设计与实验研究

本文借鉴单相泵和压缩机中相关部件的结构形式和设计方法,兼顾避免泵内相态分离过程的发生和多相增压两 个方面的要求,针对泵内多相流动的特点,提出螺旋轴流式多相泵样机及其主要过流部件的基本结构形式和设计方法,给 出了主要设计参数的选取原则和范围,并给出目前样机实验研究结果,为进一步的开发研制奠定了工作基础。     

Experiments on the unsteady flow field and noise generation in a centrifugal pump impeller

This paper reports on an experimental investigation of large-scale flowfield instabilities in a pump rotor and the process of noise generation by these instabilities. Measurements of the fluctuating components of velocity and surface pressure were made with hot-wire probes and surface mounted pressure transducers on a seven bladed back swept centrifugal water pump impeller operating with air as the working fluid. The impeller was operated without a volute or scroll diffuser, thereby eliminating any sound generation from pressure fluctuations on the volute cutoff. Thus the study focused on flow field and noise components other than the blade passage frequency (and its harmonics). The primary goal of the study was to provide fundamental information on the unsteady flow processes, particularly those associated with the noise generation in the device. It was further anticipated that detailed flow measurements would be useful for the validation of future computational simulations.The measured data at the discharge show a jet-wake type of flow pattern which results in a strong vorticity field. The flow with high velocity found on the pressure side of the impeller tends to move to the low-pressure region present at the suction side of the passage as a form of roll-up around the blade trailing edge. This motion causes an unsteady flow separation at the suction side of the blade and consequently disturbs the flow in the adjacent passage. By interacting with the impeller blades near the trailing edges, this instability flow causes a periodic pressure fluctuation on the blade surface and generates noise by a trailing edge generation mechanism. The spectrum of surface pressure measured at the trailing edge of each blade reveals a cluster of peaks which were identified with azimuthal mode numbers. The correlation between the acoustic farfield pressure and the surface pressure on the impeller blade has proven that the azimuthal modes synchronized with the number of impeller blades generate noise much more efficiently than the other modes. The paper also clarifies the correlation between unsteady flowfield measurements, in both impeller and laboratory co-ordinates, with the radiated noise properties. Thus some light is shed on the noise generation mechanisms of this particular device.     

部分流泵整机非定常流动数值模拟

本文在设计工况下采用滑移网格技术对部分流泵进行了整机非定常流动数值模拟,分别分析了叶轮、蜗壳内的非定常流动规律。计算表明,部分流泵内流的非定常特性极其强烈,只有采用非定常计算方法才能反映其内流的实质。本文的计算为进一步研究部分流泵的内流现象、提高效率、减少水利损失提供了一定的理论依据。     

蜗壳进口周向非均匀流动的数值研究

本文提出一种考虑进口非均匀流动的蜗壳流场计算方法。该方法通过叶轮出口边界与蜗壳进口边界上静压分布的迭代计算,并逐步修正蜗壳入口气流方向模拟叶轮与蜗壳内流场的相互作用。通过计算结果表明:该方法计算量小,且能获得一定程度的蜗壳进口非均匀流动。