电站自吸泵气液混合与分离及性能优化研究

发布时间：2018-02-21 20:57

本文关键词： 外混式自吸泵改型设计数值模拟气液两相流动非定常　出处：《兰州理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：近几年来,由于自吸泵优越的水利性能和使用的方便性,在工农业生产领域得到广泛应用,相比液下泵抽水易出故障,检修不便,自吸泵在这方面有足够的保障,部分水电站逐渐采用自吸泵代替原先的液下泵。自吸泵的安全性和稳定性是近几年来水泵领域研究的热门话题和科研的重要方向,而水力性能是否优越和自吸时间和自吸高度是否达标都成为关键的衡量指标。自吸泵的启动过程是一个复杂的非定常气液两相流动问题,其气液混合和分离的好坏,直接影响自吸时间和自吸高度,而自吸时间和自吸高度是衡量自吸泵自吸性能的关键指标。可见研究并找到自吸泵启动过程的气液两相流动规律是改善自吸泵自吸性能的关键。本文主要从自吸泵现有的设计理论出发,对ZX80外混式自吸泵进行改型设计;结合应用计算流体力学CFD模拟技术,对比改型前后的水力性能及内部流动情况进行对比分析,说明改型的合理性和可行性。在改型的基础上研究外混式自吸泵自吸过程的非定常气液两相流动规律。主要工作和研究成果如下:(1)选用ZX80外混式自吸泵作为本文的研究对象。在原先图纸的基础上,结合近几年自吸泵的设计理论的研究,对ZX80自吸泵进行设计。(2)建立改型前后的ZX80外混式自吸泵的物理模型,分别进行网格的划分,利用雷诺平均法和标准k-ε双方程湍流模型,取5个流量工况点对改型前后的ZX80外混式自吸泵进行定常数值模拟计算。(3)在改型前后ZX80外混式自吸泵定常数值模拟结果的基础上,分别对外特性和内部流场进行对比分析。一方面将改型前后ZX80泵的流量-扬程曲线、流量-轴功率曲线、流量-效率曲线进行了对比,研究发现:对气液分离室进行改型后,其扬程、效率有所提高,轴功率减小;另一方面通过对改型前后的气液分离室的流线和湍动能耗散率进行分析,改型后的流线更为顺畅,气液分离室的流动紊乱程度降低、效率提高。可见,本文对于对于分离室的改型是成功的,不仅提高了ZX80泵的水利性能,同时也改善了气液分离室的紊乱涡态的分布。(4)基于多相流理论基础,对改型后的ZX80外混式自吸泵启动过程进行数值模拟。设置进口边界条件为速度进口,利用C语言编程,将接近实际的速度变化程序导入Fluent软件自带的UDF,使进口速度的变化更接近实际情况;探讨启动过程中的气液两相流动现象,描述研究自吸泵内部流场的演变过程。
[Abstract]:In recent years, due to its superior water conservancy performance and ease of use, the self-priming pump has been widely used in the field of industrial and agricultural production. Compared with the subliquid pump, pumping water is prone to failure and maintenance is inconvenient, so the self-priming pump has sufficient protection in this respect. In some hydropower stations, the self-priming pump has been gradually used instead of the original submersible pump. The safety and stability of the self-priming pump has been a hot topic and an important direction of scientific research in the field of water pump in recent years. Whether the hydraulic performance is superior or not and whether the self-priming time and height are up to the standard are the key indexes. The starting process of the self-priming pump is a complicated problem of gas-liquid two-phase flow, and its gas-liquid mixing and separation are good or bad. Directly affect the time and height of self-priming, The self-priming time and height are the key indexes to measure the self-priming performance of the self-priming pump. It can be seen that the gas-liquid two-phase flow pattern in the starting process of the self-priming pump is the key to improve the self-priming performance of the self-priming pump. The pump's current design theory, The design of ZX80 external mixing self-priming pump is modified, and the hydraulic performance and internal flow before and after modification are compared and analyzed by using CFD simulation technology of computational fluid dynamics. On the basis of the modification, the unsteady gas-liquid two-phase flow law of the self-priming process of the external mixing self-priming pump is studied. The main work and research results are as follows: 1) the ZX80 external mixing self-priming pump is selected as this paper. Based on the original drawings, Combined with the research of the design theory of the self-priming pump in recent years, the physical model of the ZX80 external self-priming pump before and after modification is established. The physical model of the ZX80 external self-priming pump before and after modification is established, and the grid is divided, and the Reynolds average method and the standard k- 蔚 two-equation turbulence model are used. The steady numerical simulation of ZX80 external mixing self-priming pump before and after modification was carried out at five flow rate working points. (3) on the basis of the steady numerical simulation results of ZX80 external mixing self-priming pump before and after the modification, On the one hand, the flow-head curve, flow-axis power curve and flow-efficiency curve of ZX80 pump before and after modification were compared. On the other hand, by analyzing the streamline and turbulent kinetic energy dissipation rate of the gas-liquid separation chamber before and after the modification, the flow line of the modified chamber is more smooth, and the flow disorder degree of the gas-liquid separation chamber is reduced. It can be seen that the modification of the separation chamber is successful in this paper, which not only improves the hydraulic performance of the ZX80 pump, but also improves the distribution of the turbulent vortex state in the gas-liquid separation chamber based on the theory of multiphase flow. The starting process of the modified ZX80 external mixing self-priming pump is numerically simulated. The inlet boundary condition is set as the velocity inlet, and the C language is used to program. In order to make the change of inlet velocity closer to the actual situation, this paper discusses the phenomenon of gas-liquid two-phase flow during start-up, and describes the evolution process of flow field in self-priming pump.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH317

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