电站自吸泵的设计及内部流场特性研究

发布时间：2018-06-13 16:28

本文选题：外混式自吸离心泵 + 实验测试　；参考：《兰州理工大学》2017年硕士论文

【摘要】：由于普通离心泵吸入液面如果在叶轮以下,启动时必须预先灌水,为了在泵体内部及吸入管路能够存住水,入口需安装阀门,泵工作时阀门造成的水力损失较大,且阀口容易夹杂石块、树枝等杂物,导致封水不严而无法灌满水,这样自吸泵随之出现并得到广泛的应用,自吸泵具有体积小、工作可靠、便于远程集中控制等特点,近年来人们对于自吸泵性能做了大量的理论研究工作,其一:水力性能设计是否优秀是影响自吸性能的关键因素。其二:自吸泵的启动阶段是非常紊乱的瞬态气液两相流动过程,同时在启动阶段气液混合和分离的效果与否对于自吸性能有着显著影响。本文主要的研究内容及结果如下:(1)较为全面的概述和总结了自吸泵的研究近况及发展方向。(2)主要从自吸泵现有设计理论研究成果总结的基础上,根据电站的实际需要采用速度系数法对ZX80-65-178自吸式离心泵进行设计,满足规定的设计目标和自吸性能要求。(3)应用计算流体力学CFD对自吸泵的内部流场进行定常模拟计算,分析和研究该泵在各工况下的能量性能、内部流动机理、速度特征,并进行相关的外特性试验验证,检验自吸泵水力设计是否达到设计目标。(4)回流孔设计是在经验公式设计的基础上进行估算得到,一般很难达到最优设计值,对于特定的自吸泵,存在一个最佳回流孔的面积及其安放位置,在初次设计的基础上根据数值模拟结果研究和分析回流孔的内部流动特性,对回流孔大小重新定义,分析得到随着回流孔大小的变化,导致回流孔两侧压力差及其回流量的变化,最终反映到自吸泵外特性的变化,从而确定该自吸泵回流孔的最佳面积。(5)自吸泵的启动过程是三维非稳态的湍流运动,实验发现自吸泵的自吸初期含气率有一个激增的过程,最大能达到一半。所以本文通过气液两相流数值模拟理论研究叶轮入口在不同含气率情形下泵体内部的气液两相流动特点,为探究启动阶段的流动机理具有一定的参考价值。(6)本章主要是非稳态数值模拟,主要研究自吸泵在水力设计基础上的压力脉动变化情况,运用基于结构化网格大涡数值模拟理论的研究方法,通过设置泵内重要部位监测点监测其压力变化,从而得到监测点的压力脉动时域图和通过快速傅里叶的变化获得频域图,同时通过速度和压力云图进行分析说明。
[Abstract]:If the suction level of ordinary centrifugal pump is below the impeller, it must be filled in advance when starting. In order to store water inside the pump body and in the suction pipeline, the valve must be installed at the entrance of the pump, and the hydraulic loss caused by the valve when the pump is working is large. And the valve opening is easily mixed with stones, branches and other sundries, resulting in the sealing of water is not strict enough to fill the water, so the self-priming pump appears and is widely used. The self-priming pump has the characteristics of small volume, reliable work, convenient remote centralized control, etc. In recent years, people have done a lot of theoretical research on the performance of self-priming pump. Firstly, whether the design of hydraulic performance is good or not is the key factor to affect the self-priming performance. Second, the starting stage of the self-priming pump is a very disordered transient gas-liquid two-phase flow process. At the same time, the effect of gas-liquid mixing and separation has a significant effect on the self-priming performance. The main research contents and results of this paper are as follows: (1) A more comprehensive overview and summary of the research status and development direction of the self-priming pump. (2) based on the summary of the research results of the existing design theory of the self-priming pump, The ZX80-65-178 self-priming centrifugal pump is designed according to the actual needs of the power station. The design objective and the self-priming performance requirement are met. The CFD of computational fluid dynamics is applied to the steady simulation of the internal flow field of the self-priming pump. The energy performance, internal flow mechanism, velocity characteristics of the pump under various operating conditions are analyzed and studied. Check whether the hydraulic design of the self-priming pump has reached the design target.) the design of the backflow hole is estimated on the basis of the empirical formula design. It is generally difficult to reach the optimal design value. For a specific self-priming pump, There exists an optimum reflow hole area and its location. Based on the numerical simulation results, the internal flow characteristics of the reflow hole are studied and analyzed, and the size of the reflow hole is redefined. The results show that with the change of the size of the reflux hole, the pressure difference on both sides of the reflux hole and its reflux volume change, which is reflected in the change of the external characteristics of the self-priming pump. Thus, it is determined that the starting process of the self-priming pump is a three-dimensional unsteady turbulent motion. It is found that the initial gas content of the self-priming pump has a surge process, the maximum of which can reach half. In this paper, the characteristics of gas-liquid two-phase flow in the impeller inlet under different gas content are studied by numerical simulation of gas-liquid two-phase flow. In order to explore the flow mechanism of start-up stage, this chapter is mainly about unsteady numerical simulation, which mainly studies the variation of pressure fluctuation on the basis of hydraulic design of self-priming pump. Based on the theory of structured grid large eddy numerical simulation, the pressure variation is monitored by setting the monitoring points in important parts of the pump, and the time-domain map of pressure pulsation and the frequency domain diagram are obtained by the change of fast Fourier transform. At the same time, the velocity and pressure clouds are analyzed and explained.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV136.2;TV734

【参考文献】