【作者】 程效锐；

【导师】 李仁年；

【作者基本信息】 兰州理工大学 ， 流体机械及工程， 2014， 博士

【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。更多还原

【Abstract】 Hydraulic transport of solid materials is typical application in engineering of solid-liquid two phase flow. As a new type of impurity pump, the screw centrifugal pump has the outstanding advantages, such as high efficiency, wear resistant, anti-clogging, etc. The law of energy conversion and unsteady hydrodynamic characteristics in unique spiral impeller must be greatly different with the traditional centrifugal pump impeller, when transporting solid-liquid two phase medium. The existing research results about the screw centrifugal pump are mainly concentrated on the design method, external characteristic, structure of flow field. The research of energy conversion characteristics in the screw centrifugal pump is relatively less, especially when transporting solid-liquid two phase medium, the current research of the energy transfer, transformation and dissipation process in impeller and casing, is lacking.In this paper, through test and numerical calculation method, the energy conversion ability and the influence factors are mainly studied along different regions in the screw centrifugal pump impeller spiral flow channel and casing, when transporting the water and the solid-liquid two phase medium. The steady and unsteady energy distribution and conversion characteristics of space and time are revealed in impeller spiral channel and casing. And on this basis, the hydraulic design method of the impeller and the casing is put forward based on the theory of two phase flow rate ratio. The main research content is divided into three parts:1. The characteristics of energy conversion in impeller and casing with screw centrifugal pump transporting water.From two aspects of steady and unsteady, the impeller input power, the characteristics of the energy conversion, efficiency and energy loss are studied respectively. The results show that the impeller mainly do power work on fluid through pressure, and the fluid viscous forces work power account for only a small proportion. The method and basis to segment spiral part, transitional part and centrifugal impeller part are given, meanwhile the results show that the spiral part of impeller is critical area of fluid gain energy.As impeller rotating, the instantaneous energy conversion and loss in the impeller continue to change, and has periodic trends. Asymmetry of the blade, the impeller and casing interference effect cause periodic change of the input and output power, impeller surface pressure, also causes instability mutual conversion between the static pressure and dynamic pressure. For flow rate changing, the energy conversion efficiency of impeller spiral part is greater change than the impeller centrifugal part, and the centrifugal part decides the fluctuation characteristics of impeller output power.The main form of energy loss in the impeller is turbulence dissipation loss and wall friction loss. As small flow rate, the loss is given priority to with turbulent dissipation loss, and as large flow rate, the loss is given priority to with friction loss. The main area of the turbulent dissipation loss is in the impeller outlet, and the main area of the friction loss is in the centrifugal part of impeller. The energy loss in casing is mainly impact losses of tongue and turbulent dissipation losses, and its value increase with geometric ratio when flow rate increase.2. The characteristics of unsteady energy conversion in impeller and casing with screw centrifugal pump transporting solid-liquid two phase medium.Using Eulerian solid-liquid two phase flow model, it has carried on the unsteady numerical analysis for impeller shaft power, turbulence intensity of cross section, efficiency, turbulent kinetic energy dissipation rate, dynamic pressure coefficient and the influence of casing energy conversion characteristic when the solid phase concentration and particle size change respectively.The results show that the pump average head will fell, but the fluctuation increased when the solid phase concentration increases. As the increase of particle size and solid phase concentration, the impeller input relative shaft power fluctuations increase, and the efficiency of the pump declines significantly. And the range of high efficient on instantaneous efficiency curve is a little change, its location is made up of impeller, casing shape and relative position of two, but not the physical parameters of the mediumThe impeller efficiency and turbulence intensity on the impeller flow channel section shows strong periodic change rule. Solid phase concentration on the influence of turbulence intensity is greater than the influence of particle size change. As solid phase concentration and particle size increased, each section of turbulent kinetic energy dissipation rate in casing are increasing trend, especially turbulent kinetic energy dissipation rate of sections close to the position of the tongue are dramatic change. The spiral propulsion function of spiral part of impeller flow channel makes effect of the particle diameter and fluid velocity change on turbulence dissipation rate is reduced, the change of the solid phase volume fraction and particle diameter on the influence of the turbulent kinetic energy dissipation are mainly concentrated in the centrifugal impeller part.3. Screw centrifugal pump solid-liquid two phase hydraulic design methods.According to the rule of energy conversion and distribution within the screw centrifugal pump and impeller when transporting solid-liquid two phase medium, and based on the solid liquid two phase flow rate ratio coefficient and the axial velocity matching, the solid liquid two phase flow impeller parameter equation is worked out. And on basis of energy conversion characteristic matching between the casing and impeller, the area of NO.8calculation method is given, Then through numerical analysis, the results show that the pump efficiency increased by8.5%than that of the original model When transporting given volume fraction of solid-liquid two phase flow,therefore proved the design method in this paper to achieve the desired effect.更多还原