基于数值模拟的HL160水力压力脉动研究

发布时间：2018-04-24 01:13

本文选题：混流式水轮机 + 水力振动　；参考：《河北工程大学》2014年硕士论文

【摘要】：作为水电站的核心部件的水轮机组，对水电站的整体性能起着关键性的作用。随着水轮机组单机容量和装机尺寸的逐渐增大，水轮机比转速日益提高，水轮机振动问题越来越突出，因而人们对于混流式水轮机的运行稳定性越来越重视，其中流场不稳定流动现象是引起振动的主要原因之一。利用CFD技术，对混流式水轮机过流部件内部流动进行三维定常及非定常流动分析，可以比较深入地了解水轮机水力振动方面的内在机理，这样对水轮机的综合水力性能的提高、水轮发电机组的运行稳定性的改善具有非常重要的实际意义。本文以学校试验台的模型水轮机HL160-LJ-25为研究对象，，主要研究内容如下：（1）利用三维造型软件Solidworks和ICEM网格划分软件对水轮机的蜗壳、固定导叶、尾水管的过流流道进行实体造型和网格划分，利用专业旋转机械软件Bladegen和Turbogrid对活动导叶和转轮进行实体造型和结构化网格划分。（2）采用k-ε湍流模型对水轮机整体内部流动进行数值计算。因为蜗壳和固定导叶造型时放在了一起，所以水轮机整个流道由四个计算域组成，存在三对交界面，两个不转动计算域的交界面采用General Connection方式连接，不转动的与转动的计算域交界面采用Frozen Rotor Model方式连接，由此对若干工况下水轮机的内部流动进行了三维定常湍流计算。研究发现大流量工况下转轮的内部流动特性普遍比小流量工况的流动特性好，最优工况附近流动特性最好，与以往传统认识相符。（3）以#1小流量工况全流道的三维定常计算结果作为初始条件，对水轮机进行三维非定常湍流计算，重点分析了活动导叶和转轮之间动静干涉下的流场和尾水管内流场的流动特点。研究发现由于导叶出流的影响在某固定位置上总是出现压强最大值和压强最小值，在不同的时间步下，对于一个固定点，其压强是随着转轮的转动在不停地作周期性变化。#1工况下涡带从转轮出口直至发育到弯肘段消失，在直锥段呈现比较大的压力脉动，肘管段的脉动主要集中于肘管的外壁侧，在肘管段的下部直至扩散段压力脉动很小。分析计算结果表明，虽然转轮内部也存在流动不稳定问题，存在压力分布不理想现象，但压力脉动振幅很小，且无明显规律，有待于今后作更深入研究探讨。
[Abstract]:As the core component of hydropower station, hydraulic turbine unit plays a key role in the whole performance of hydropower station. With the increasing of the unit capacity and the size of the turbine unit, the specific speed of the turbine increases day by day, and the vibration problem of the turbine becomes more and more prominent, so people pay more and more attention to the operation stability of the Francis turbine. The unstable flow is one of the main causes of vibration. By using CFD technology, three-dimensional steady and unsteady flow analysis is carried out on the internal flow of the flow passing parts of a Francis turbine. The inherent mechanism of hydraulic vibration of the turbine can be deeply understood, and thus the comprehensive hydraulic performance of the turbine can be improved. It is of great practical significance to improve the operation stability of hydroelectric generating sets. In this paper, the model hydraulic turbine HL160-LJ-25 of the school test bench is taken as the research object. The main research contents are as follows: 1) solid modeling and meshing of turbine volute, fixed guide vane and draft tube flow passage are carried out by using 3D modeling software Solidworks and ICEM mesh division software. The solid modeling and structured meshing of moving guide vane and runner are carried out by using professional rotating machine software Bladegen and Turbogrid. K- 蔚 turbulence model is used to calculate the internal flow of hydraulic turbine. Because the volute and the fixed guide vane are placed together, the whole runner of the turbine is composed of four calculation fields, and there are three pairs of interfaces. The two interfaces in the non-rotating computing field are connected by General Connection. The interface between the non-rotating and rotational computational domain is connected by Frozen Rotor Model mode. Thus, the three-dimensional steady turbulent flow of the turbine is calculated under a number of operating conditions. It is found that the internal flow characteristics of the runner under large flow conditions are generally better than those of small flow conditions, and the flow characteristics near the optimal conditions are the best, which is consistent with the previous traditional understanding. (3) taking the three-dimensional steady calculation results of the whole flow channel in #1 small flow condition as the initial condition, the three-dimensional unsteady turbulent flow calculation of the turbine is carried out. The characteristics of the flow field and the flow field in the draft tube under the dynamic and static interference between the guide vane and the runner are emphatically analyzed. It is found that the maximum and minimum pressure always occur at a fixed position due to the influence of the flow out of the guide vane. At different time steps, for a fixed point, The pressure fluctuates periodically with the rotation of the runner. Under the condition of #1, the vortex band disappears from the runner outlet to the elbow section, showing a relatively large pressure pulsation in the straight cone, and the pulsation of the elbow tube is mainly concentrated on the outside side of the cubital tube. The pressure fluctuation from the lower part of the elbow to the diffusion section is very small. The results of analysis and calculation show that although the flow instability exists in the runner and the pressure distribution is not ideal, the amplitude of pressure pulsation is very small and has no obvious regularity, so it needs to be further studied in the future.
【学位授予单位】：河北工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV734.1;TV136.1

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