螺旋离心泵内能量转换特性及设计方法研究

发布时间：2018-10-21 16:03

【摘要】：固体物料的水力输送是固液两相流典型的工程应用,螺旋离心泵作为一类新型的杂质泵,在输送固液两相流体时具有突出的优越性,如高效、耐磨、抗堵塞等。其独特的螺旋型叶轮在输送固液两相流介质时的能量转化规律和非稳态流体动力学特性与传统离心泵叶轮必然有较大不同。螺旋离心泵已有的研究成果主要集中在对设计方法、外特性及内部流场结构方面的研究,而对螺旋离心泵内能量转换特性的研究相对比较少,尤其是对泵在输送固液两相流时叶轮和压水室内,不同区域能量传递、转化和耗散过程的研究更是缺乏。本文通过试验和数值计算相结合的方法,重点研究了螺旋离心泵内沿叶轮螺旋流道及压水室流向不同区域,在清水和固液两相流介质时能量转换的能力与影响因素,揭示了在输送清水和固液两相流介质时叶轮和螺旋型压水室内稳态和非稳态能量的时空分布规律及转换特性。并在此基础上,提出了基于两相流速比理论的叶轮型线方程和压水室水力设计方法。本文主要研究内容分为3个部分： 1.螺旋离心泵在输送清水介质时叶轮和压水室内能量转换特性。分别从稳态和非稳态两个方面研究了叶轮输入功率、能量转换效率和能量损失的特点,结果表明,叶轮对流体做功主要表现为压力做功,而流体的粘性力做功只占较小的比重。给出了叶轮螺旋段、过渡段和离心段划分方法和依据,发现叶轮螺旋段是叶轮对流体做功和流体获得能量的关键区域。叶轮旋转时,流道内瞬时能量转换和损失一直在发生变化,且具有周期性规律。叶片的不对称及压水室和叶轮动静干涉作用,引起叶轮输入和输出功率、叶轮表面压力的周期性变化,也造成压水室内动静压能转换的不稳定。流量变化对于叶轮螺旋段能量转换效率的影响要大于离心段,离心段对叶轮输出功率的波动特性起决定作用。叶轮内能量损失的主要形式是湍流耗散和壁面摩擦损失,小流量时以湍流耗散损失为主,大流量时以摩擦损失为主；湍流耗散损失的主要区域在叶轮出口,摩擦损失的主要区域在叶轮离心段。压水室内的能量损失主要是隔舌处的冲击损失和湍流耗散损失,其值随流量增加呈几何倍数增长。 2.螺旋离心泵在输送固液两相流时泵内的非稳态能量转换特性。采用欧拉(Eulerian)固液两相流模型分别对固相浓度和粒径变化对叶轮相对轴功率、截面湍流强度、效率、湍动能耗散率、动扬程系数以及压水室能量转换特性的影响进行了非稳态数值分析。结果表明,固相浓度增加时,泵扬程的平均值有所下降,但波动幅度加大。随粒径和固相浓度增加,叶轮输入相对轴功率波动幅度加大,泵效率的下降幅度也明显增加,但瞬时效率曲线的高效区范围变化不大,其位置是由叶轮、压水室形状和两者的相对位置共同决定的,而与输送介质几何物性参数的相关性不强。叶轮效率和叶轮流道截面上湍流强度表现出较强的周期性变化规律。固相浓度对湍流强度的影响要大于粒径变化的影响。随着固相浓度、粒径增加压水室各截面湍流动能耗散率均有增加的趋势,变化最强烈的截面都是靠近隔舌和喉部位置。叶轮螺旋段流道的螺旋推进作用使得颗粒直径和液体流速变化导致的湍流耗散率的变化被降低,固相体积分数和颗粒直径的变化对叶轮湍动能耗散的影响主要集中在离心段流道区域内。 3.螺旋离心泵固液两相流水力设计方法根据螺旋离心泵在输送固液两相流时叶轮内能量转换特性及固相分布规律,利用固液两相流速比系数,基于轴向流速匹配的原则,得到了叶轮固液两相流叶片型线方程。同时基于叶轮和压水室能量转换相匹配原则给出了压水室水力设计方法,并对给出的设计方法进行了数值验证,改进后的模型在输送己知固相浓度两相流介质时泵效率较原模型提高了8.5%,证明了本文给出的设计方法达到了预期的效果。
[Abstract]:The hydraulic transportation of solid materials is a typical engineering application of solid-liquid two-phase flow. The spiral centrifugal pump is a kind of new type of impurity pump. It has outstanding advantages in conveying solid-liquid two-phase fluid, such as high-efficiency, wear-resistant, anti-clogging and so on. The energy conversion rule and non-steady-state fluid dynamics characteristic of the unique spiral impeller in conveying solid-liquid two-phase flow medium are different from that of the traditional centrifugal pump impeller. The research results of the spiral centrifugal pump mainly focus on the research on the design method, the outer characteristic and the internal flow field structure, and the research on the energy conversion characteristics in the spiral centrifugal pump is relatively few, especially the impeller and the pressure water chamber when the pump is in two-phase flow of the conveying solid liquid, The research on energy transfer, transformation and dissipation in different regions is lacking. Through the combination of experiment and numerical calculation, the paper mainly studies the capacity and influence of the spiral flow channel and the pressure water chamber of the spiral centrifugal pump in different areas, and the energy conversion in the two-phase flow medium of clean water and solid solution. The spatial and temporal distribution of steady state and non-steady state energy in both the impeller and the screw-type pressure water chamber when the two-phase flow medium of clean water and solid solution are conveyed is revealed. The characteristics of impeller type line equation and pressure water chamber based on two-phase flow rate ratio theory are presented. Methods: The main contents of this paper are divided into three parts: Part: 1. Inside the impeller and pressure water chamber when the spiral centrifugal pump delivers clean water medium The characteristics of the input power, energy conversion efficiency and energy loss of the impeller were studied from both steady state and unsteady state. The results show that the main performance of the impeller on the fluid is the pressure work, and the hydrodynamic force of the fluid The method and basis for dividing the spiral section, the transition section and the centrifugal section of the impeller are given, and the spiral section of the impeller is found to be the impeller to do work and fluid to the fluid. Critical area of energy. During rotation of the impeller, instantaneous energy conversion and loss in the flow path have been occurring and the pressure water chamber is also caused by the periodic change of the pressure on the surface of the impeller. The influence of flow variation on the energy conversion efficiency of the spiral section of the impeller is greater than that of the centrifugal section, and the centrifugal section is used for the output of the impeller. The main form of energy loss in the impeller is turbulence dissipation and wall friction loss, while small flow is mainly caused by turbulence dissipation loss, while large flow is mainly caused by friction loss; the main area of the turbulent dissipation loss is at the outlet of the impeller. the main area of the wiping loss is in the centrifugal section of the impeller, the energy loss in the pressure water chamber is mainly the impact loss and the turbulent dissipation loss at the baffle, The value of the spiral centrifugal pump increases with the increase of the flow rate. The non-steady-state energy conversion characteristics of two-phase flow of liquid are studied. The relative axial power, turbulent intensity, efficiency, kinetic energy dissipation rate, dynamic lift coefficient and pressure water of the impeller are calculated by Eulerian solid-liquid two-phase flow model, respectively. Non-steady-state numerical analysis was carried out on the effect of the energy conversion characteristics of the chamber. The results showed that the solid phase concentration increased. The average value of pump head decreases, but the fluctuation amplitude increases. With the increase of particle size and solid phase concentration, the amplitude of relative axial power fluctuation of impeller is increased, and the decrease amplitude of pump efficiency is increased obviously, but the range of high efficiency area of instantaneous efficiency curve is not large, and its position is composed of leaves. The shape of the wheel, the pressure chamber and the relative position of the two are determined together and the relationship between the geometric physical properties of the conveying medium is not strong, The turbulence intensity on the cross section shows a strong periodic rule. The effect of solid phase concentration on turbulence intensity is larger than that of particle size variation. With the solid phase concentration, the dissipation rate of turbulent kinetic energy in each section of the pressure water chamber increases with the increase of the solid phase concentration. The change of the turbulent dissipation rate caused by the change of particle diameter and liquid flow velocity is reduced, the volume fraction of solid phase and the change of particle diameter are changed. The influence of the kinetic energy dissipation of the impeller is mainly concentrated in the centrifugal section The hydraulic design method of solid-liquid two-phase flow of spiral centrifugal pump in flow channel region is based on the energy conversion characteristic and solid state of spiral centrifugal pump in the two-phase flow of conveying solid liquid. phase distribution law, using two-phase flow rate ratio coefficient of solid solution Based on the principle of matching the axial flow velocity, the two-phase flow blade type line equation of the impeller solid solution is obtained. At the same time, the hydraulic design method of the pressure water chamber is given based on the matching principle of the energy conversion of the impeller and the pressure water chamber, and the design method is validated and the improved model is improved. The pump efficiency is higher when the two-phase flow medium with known solid phase concentration is conveyed
【学位授予单位】：兰州理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TH311

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