【作者】 李昳；

【导师】 朱祖超；

【作者基本信息】 浙江理工大学 ， 机械工程， 2014， 博士

【摘要】 固液两相输送离心泵在国民经济各行业应用广泛，但这类泵存在以下关键技术难题，一是由于存在固体物质导致效率低，二是由于磨损问题而导致的可靠性差，这两个问题一直制约着固液两相输送离心泵的研制和应用。本文以固液输送流道式离心泵为研究对象，对其水力性能和磨损性能开展计算和实验研究。首先通过对固液两相流场中颗粒所受作用力进行分类和量级分析，确定了颗粒直径和所受作用力的关系，提出固液两相的流动和磨损计算模型；针对不同直径颗粒，分别采用Mixture模型和DPM模型结合UDF引入颗粒体积效应的影响，对不同体积分数的固液两相流动进行数值计算，并在此基础上进行了内部流动对性能的影响以及磨损规律分析；搭建固液两相实验台对流道式离心泵进行固液两相流动工况下的外特性实验研究；最后基于理论分析，推导出设计流量点固液混输工况的扬程下降率预测公式，可供实际工程使用。论文的主要工作和结论具体如下：1.确立了离心泵内部固液两相流场的流动和磨损计算模型。首先根据液体与颗粒之间的相互作用关系，将作用力进行分类；然后将各作用力与流动阻力进行量级对比分析，确定颗粒直径与作用力的关系，在此基础上确定相应的两相流模型；考虑湍流扩散对颗粒的影响，建立基于随机游走方法的颗粒轨迹计算模型，并选择单颗粒磨损模型结合泰勒级数展开，确定颗粒碰撞磨损计算模型。2.数值模拟并验证了离心泵内部的固液两相流场。分别选择基于欧拉-欧拉方法的Mixture两相流模型和基于欧拉-拉格朗日方法的DPM两相流模型对离心泵内部固液两相流场进行数值模拟，并将离心泵性能参数的计算值与文献中的实验值对比，发现根据颗粒直径选择相应的两相流模型进行计算可以准确模拟离心泵内部的固液两相流动。3.得到了固液两相流场特性与水力性能和磨损性能的关系。分析不同颗粒直径和体积分数工况下，全流道内部的液相压力、液相流线和蜗壳内部的固液两相速度差与颗粒直径和体积分数的关系。发现不同工况下的泵流道内压力总体分布差不多，但是随着颗粒直径和固相体积分数的增加，流道内的压力值呈减小趋势。分析不同颗粒直径和体积分数工况下，流道内部不同部位的磨损速率、剪应力和颗粒分布与颗粒直径和体积分数的关系。发现在叶轮和蜗壳流道的不同部位，磨损速率均随体积分数的增加而增加；随着颗粒直径的增加，蜗壳内磨损速率呈下降趋势，叶轮流道内部则随部位的变化不尽相同。4.进行了离心泵的固液两相外特性实验研究。与清水输送工况的性能相比，随着颗粒直径和固相体积分数的增加，固液两相输送工况的扬程和效率基本呈缓慢下降趋势，仅在输送微小颗粒时，效率略有增加。效率总体下降幅值比扬程下降幅值小。实验值与计算值的对比发现，实验曲线的变化趋势与计算曲线的趋势基本一致，实验值略小于计算值。5.推导并验证了固液两相工况下的扬程下降率预测公式。基于泵出口处固液两相速度相等的假设，进行理论分析与推导，得到设计流量工况下固液两相混合输送时的扬程下降率预测公式，该公式主要通过当地体积分数来体现固相对性能参数的影响，可以较为准确方便的对设计流量点固液混输工况的扬程下降率进行计算，但预测值略小于实验值。更多还原

【Abstract】 The solid-liquid two-phase flow transportation by centrifugal pump has been more andmore widely. As the existence of solid phase and its abrasion, there were two key problems: poorefficiency and poor reliability. These two problems restrict the research and application of thesolid-liquid two-phase pump.In this dissertation, hydraulic performance and wear property of channel-type centrifugalpump were studied through numerical simulation and experimental research. The forces actingon particle in the solid-liquid two-phase flow were classified. Based on analyzing the order offorce magnitude, the solid-liquid two-phase flow model and erosion model were proposed. Aimat different particle diameters, the Mixture model and the DPM model were used to simulate thetwo-phase flow respectively on the condition of different volume fraction. The influence ofinternal flow characteristic on pump performance was analyzed. The test rig for solid-liquidtwo-phase flow transportation was constructed. And characteristic tests of the channel-typecentrifugal pump were carried out. Based on theoretical analysis, the prediction formula of headdescent ratio was derived at best efficiency point when pumping solid-liquid two-phase mixture.The main contents and conclusions of this dissertation are showed as the follows:1. Solid-liquid two-phase flow model and abrasion model for the centrifugal pump aredetermined.Firstly, acting forcesare classified according to the relationship between the particle and theliquid phase. The magnitude of each force is compared with that of resistance force to confirmthe relation between the particle diameter and the acting force. Accordingly, different two-phaseflow models are proposed. Consideringthe influence of turbulence on particle, the kinetic modelof particle motion is established based on random walk method. The model of particle abrasionfor simulation is got by the Taylor expansion of suitable abrasion model for single particle.2. The numerical simulation and results validation are carried out for the solid-liquidtwo-phase flow in the centrifugal pump.Mixture model and DPM model are used to simulate the solid-liquid two-phase internalflow field separately. Compared the simulated results with the test results in a publisheddissertation, it can be found that these two models differentiated by particle diameter are properly used in computation.3. The relationship of the solid-liquid two-phase flow characteristic, hydraulic performanceand abrasion property is revealed.On the conditions of different particle diameter and different volume fraction, the pressureand streamline of liquid phase in whole flow channel, the velocity difference between the solidphase and the liquid phase in volute channel are analyzed. It is concluded that pressuredistributions are almost the same on different working conditions. The values of pressure in flowchannel decrease with the increasing of the particle diameter and the volume fraction.On the conditions of different particle diameter and different volume fraction, the erosionvelocity ratio, shear stress and particle concentration are analyzed. It can be found that theerosion velocity ratio on the flow channel wall increases along with the increasing of the volumefraction. But along with the increasing of the particle diameter, the erosion velocity ratio on thevolute wall decreases. And the variation trend of erosion velocity ratio on the impeller channelwall changes according to the wear position.4. The performance experiments of the centrifugal pump transporting solid-liquid two-phasemixture are carried out.Compared with head and efficiency values of the water transportation, values of solid-liquidtwo-phase transportation decrease slowly as the increasing of particle diameter and volumefraction. The decreasing values of efficiency are totally smaller than the decreasing values ofhead. The comparing results indicate that the change trend of experimental values is the same asthat of simulated values basically. But experimental values are smaller than simulated values.5. The prediction formula of head descent ratio is derived and validated when pumping thesolid-liquid two-phase mixture.Assumping that two phases’velocities of pump outlet are equal, the head prediction formulaof two-phase mixture transportation is derived based on the theory analysis. The influence ofsolid phase is introduced in pump performance by local volume fraction in this formula. So theformula can be conveniently applied to compute the head at the best efficiency point. But thepredicted values are smaller than the test values.更多还原