固液两相流离心泵非定常流动诱导磨损机理研究

The wear of parts in contact with fluid in solid-liquid two-phase flow centrifugal pump is one of the bottlenecks in power plant and chemical industries etc. At present the mechanism of wear in solid-liquid two-phase flow centrifugal pump isn't clear and the wear models aren't perfect. Mechanism of wear induced by unsteady flow in solid-liquid two-phase flow centrifugal pump hasn't been reported at home and abroad and will be studied in the project. In the study large eddy simulation based on a thin boundary layer equation and wear models will be used to predict the flow field in solid-liquid two-phase flow centrifugal pump. The law of characteristic parameters of the flow field such as pulsating frequency, turbulent kinetic energy of particle etc. affected by particle size and blade shapes etc. will be studied with CFD simulation and PIV flow field tests. The relationship between the flow field characteristic parameters and the wear weight will be abtained by wear simulation and wear tests. The wear model of solid-liquid two-phase flow centrifugal pump will be established with multiple linear regression method after flow field characteristic parameters dimensionality reducted with rough set theory etc. The study aims at resealing the mechamism of wear induced by unsteady flow in solid-liquid two-phase flow centrifugal pump and will have an important social and scientific significance in wear control, resources conservation and technology level improvement for solid-liquid two-phase flow centrifugal pump.

固液两相流离心泵过流部件的磨损是电厂、化工等行业的瓶颈问题之一。目前固液两相流离心泵的磨损机理尚不清晰、磨损模型尚不完善，非定常两相流诱导磨损的机理在国内外未见报道。本项目拟对薄边界层方程的大涡模拟方法、Finnie磨损模型等在模拟固液两相流离心泵非定常流动及磨损方面的适用性进行研究；采用CFD数值模拟与PIV实验相结合的方法，研究颗粒粒径、液相流速等两相流参数及叶轮形状对流体脉动频率、颗粒湍动能等非定常流场特性参数的影响规律；通过磨损模拟和磨损实验相结合的方法，建立固液两相流离心泵非定常流场特征参数与磨损量的对应关系，用粗糙集理论等方法对流场特征参数降维，用多元线性回归的方法建立固液两相流离心泵的磨损模型。该项目研究旨在揭示非定常两相流诱导固液两相流离心泵磨损的机理，对控制固液两相流离心泵磨损，节约资源及对提升固液两相流离心泵技术水平具有重要的社会意义和科学意义。

固液两相流离心泵的过流壁面容易磨损是大型火电厂湿法脱硫工艺中急需解决的问题。随着固液两相流离心泵广泛在环境保护、污水、煤矿、食品、电力等行业的应用，磨损问题显得日益突出。.本研究的主要内容与创新点如下：1.查阅大量国内外文献，了解固液两相流离心泵的国内外研究现状和发展动态，结合数值模拟计算的理论基础，为本文三维不可压缩的湍流计算建立流体力学基本方程、选择湍流模型、多相流模型和离散相模型的方法提供基础。２.利用三维造型软件Pro/E及网格划分软件ICEM把固液两相流离心泵全流道中各个水力部件进行建模装配以及网格划分，并且对模型的网格进行无关性检查。３.通过不同颗粒密度、不同进口流量、不同叶轮转速三个方面对固液两相离心泵内部流场和磨损特性进行了定常模拟分析，总结归纳磨损特征与流场特征及初始条件的关系。在混合相模型下通过分析颗粒浓度分布、速度以及内部流场随着不同初始条件变化规律，定性预测不同初始条件对过流部件磨损的影响，得出以下结论：颗粒密度越大、流量越小、转速越高，叶轮流道越容易形成回流，加剧对壁面的磨损；叶片工作面比叶片背面容易受到磨损。从隔舌沿着蜗壳圆周壁面至泵出口各部位均是磨损严重区。.在离散相模型下结合颗粒运动轨迹以及Finnie冲蚀磨损模型，定量预测不同初始条件对过流部件磨损的影响，得出以下结论：随着颗粒密度的增大，叶片工作面磨损总量依次是叶片背面的69.8%、233.7%、240.2%；随着流量的增大，叶片工作面磨损总量依次是叶片背面的1140.8%、233.7%、306.5%；随着转速的增大，叶片工作面磨损总量依次是叶片背面的136.48%、233.7%、252.2%；从隔舌沿着蜗壳壁面至泵出口均有不同程度的磨损，尤其是隔舌附近更加严重，蜗壳总磨损量数量级远大于叶轮总磨损数量级；颗粒密度、叶轮转速的增大以及进口流量偏离设计流量时都会导致过流部件磨损增大。4.通过不同颗粒密度、不同进口流量、不同叶轮转速三个方面对固液两相离心泵内部流场和磨损特性进行了非定常模拟分析。在混合相模型下通过分析蜗壳近壁处压力脉动、颗粒瞬态浓度分布、瞬态速度随着不同初始条件的变化规律，归纳脉动流对颗粒瞬态浓度、速度随时间变化规律，得出以下结论：蜗壳内各监测点压力脉动均呈周期性变化，脉动流对颗粒分布影响很小，但对颗粒速度影响很大，颗粒瞬时速度同样呈现周期性变化。