水泵水轮机MGV装置协联及性能研究

发布时间：2018-06-19 09:27

本文选题：水泵水轮机 + 预开导叶　；参考：《兰州理工大学》2017年硕士论文

【摘要】：随着抽水蓄能电站的装机容量增加,对电站的核心部件水泵水轮机稳定运行提出了更高的要求。但机组在启动、甩负荷等一些过渡过程中易进入“S”曲线特性区域,机组在此区域中运行状态很不平稳,易造成并网困难。虽现阶段多使用增设MGV装置(misaligned guide vanes,非同步导叶装置)改善机组“S”特性,但在机组过渡过程中同步导叶与非同步导叶未能协联,致使其机组振动增加,运行稳定性降低。因此,本文通过对水泵水轮机内部流场流动特性、动力特性以及压力脉动特性的研究,最终得出机组MGV装置协联特性性能的内在规律。本文主要研究内容及成果如下:(1)对水泵水轮机机组启动过程中不同工况点的研究发现,主要引起启动过程中机组振动的原因是由于活动导叶开度较小,导致流过活动导叶内侧流面产生附着涡,在活动导叶内侧尾段有涡脱落的现象,使漩涡进入无叶区,使其流动复杂化。且流体通过活动导叶时相对速度与绝对速度间夹角减小,产生滑移现象,使流体进入转轮的流速降低从而导致对转轮冲撞作用加大,增加了流体的水力损失。(2)无叶区压力脉动频率与叶频保持一致,活动导叶后转轮前的无叶内流区域的压力脉动与转轮旋转所引起的动静干涉有很大关系。对于机组启动过程中不同工况的压力脉动频率,第一主频与第二主频的幅值随着流量的增大而减小,且在同一工况下各个监测点主频幅值变化程度相似。(3)通过对水泵水轮机加装MGV装置后无叶区压力脉动幅值变化的研究发现,MGV装置对机组的稳定性有一定的影响,在其他同步导叶开度开至16mm ((?)0=32.6%,其中(?)0为相对开度,定义为该活动导叶开度与最大活动导叶开度的比值),MGV装置预开活动导叶至24mm ((?)0=48.9%)时对机组振动具有减缓作用。当机组其他同步导叶开度分别开至19mm((?)0=38.7%),MGV装置导叶开度为24mm时对机组振动影响较小。当其他同步导叶开度开至22mm((?)0=44.8%),MGV装置导叶开度为33mm((?)0=67.3%)时机组无叶区压力脉动幅值相对较小。(4)通过对机组的内流特性与压力脉动特性研究,发现当机组启动时MGV装置的活动导叶预开至24mm,待水轮机进入额定转速且转速保持稳定之后,关至与其他同步导叶相同开度。此协联策略可以使机组在启动过程中产生振动最小化,从而保证机组的稳定运行。
[Abstract]:With the increase of installed capacity of pumped storage power station, a higher requirement is put forward for the stable operation of pump turbine, the core component of the power station. However, in the process of start-up and load rejection, the unit can easily enter the characteristic region of "S" curve, and the running state of the unit in this area is very unstable, which is easy to cause difficulties in connection to the grid. Although it is often used to improve the "S" characteristic of the unit by adding misaligned guide vanes (asynchronous guide vane) at present, the synchronous guide vane and the asynchronous guide vane are not cooperatively connected during the transition of the unit, which results in the increase of the unit vibration and the decrease of the operation stability. Therefore, through the study of the flow field characteristics, dynamic characteristics and pressure pulsation characteristics of the pump turbine, the inherent law of the coconnection characteristic of the MGV unit is obtained. The main research contents and results of this paper are as follows: (1) the research on different working conditions of water pump turbine units during start-up shows that the main cause of unit vibration during start-up is the small opening of the active guide vane. The phenomenon of vortex shedding in the inner tail of the active guide vane leads to the vortex flowing through the inner flow surface of the active guide vane, which makes the vortex enter the vaneless region and complicate the flow. And the angle between the relative velocity and the absolute velocity decreases when the fluid passes through the moving guide vane, which results in the slip phenomenon, which reduces the velocity of the fluid entering the runner, resulting in the increase of the impact on the runner. The hydraulic loss of fluid is increased. 2) the frequency of pressure pulsation in the vaneless region is consistent with the frequency of the blade. The pressure pulsation in the impeller flow region in front of the moving guide vane is closely related to the dynamic and static interference caused by the rotation of the runner. For the pressure pulsation frequency of different working conditions during the start-up of the unit, the amplitude of the first main frequency and the second main frequency decrease with the increase of the flow rate. Under the same condition, the main frequency amplitude of each monitoring point is similar. (3) through the study of the pressure fluctuation amplitude change in the leafless area after the pump turbine is installed with MGV device, it is found that the MGV device has a certain influence on the stability of the unit. When the other synchronous guide vane is opened to 16mm, the relative opening is defined as the ratio of the active guide vane opening to the maximum active guide vane opening, and the moving guide vane is preopened to 48.9g / 24mm. The vibration of the unit can be alleviated when it is defined as the ratio of the active guide vane opening degree to the maximum active guide vane opening degree (MGV device is the ratio of the active guide vane opening to the maximum active guide vane opening degree). When the opening degree of other synchronous guide vane of the unit is 19mm and 38.7 respectively, the effect on the vibration of the unit is less when the guide vane opening of the MGV unit is 24mm. When other synchronous guide vane openings reach 22mm and 44.8mm, when the guide vane opening of the MGV unit is 33mm / 67.3mm), the amplitude of pressure pulsation in the vaneless area of the unit is relatively small. (4) by studying the internal flow characteristics and the pressure pulsation characteristics of the unit, It is found that the active guide vane of the MGV unit is preoperated to 24mm when the unit is started, and when the turbine enters the rated speed and the speed remains stable, it is turned off to the same opening degree as the other synchronous guide vane. The cocoupling strategy can minimize the vibration of the unit during start-up and ensure the stable operation of the unit.
【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

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