冲击式水轮机及其内部不良流动的数值模拟研究

发布时间：2018-03-25 07:38

本文选题：水力机械　切入点：CFD　出处：《哈尔滨工业大学》2014年硕士论文

【摘要】：我国西部高水头水力资源的蕴含量非常丰富，冲击式水轮机具有适应高水头运行的特点，，是高水头水力开发必不可少的机型。然而与反击式水轮机已经非常成熟的技术相比，我国对冲击式水轮机的研究可以说才刚刚起步。冲击式水轮机内部的流动要比反击式水轮机内部流动复杂很多，因为其内部流动是三维非定常的气液两相流流动，分析其流动特点时，不仅要考虑气体相与液体相之间的相互作用，还要考虑射流与射流之间相互干涉、射流与转轮之间相互干涉等很多不良流动现象，这些不良流动现象会很大的降低水轮机的出力和效率，也会造成水轮机机组的不稳定，因此对冲击式水轮机内部流动状态进行分析，研究其内部的存在的各种不良流动现象就显得特别重要。为实现对冲击式水轮机内部流动进行分析，本文中对某一在运水电站的水斗式水轮机原型内部流动进行了数值模拟，本文研究的主要内容如下： 1.对冲击式水轮机的导水部件配水管进行数值模拟，分析其内部的流动不均匀现象和流动损失，并对喷嘴内流场进行数值模拟，得到此喷嘴中喷针行程与喷嘴流量的关系。 2.通过对冲击式水轮机转轮内部两相流流动进行数值模拟，对不同时刻同一水斗内的流动状态进行了分析，对同一时刻转轮中受两射流作用的不同水斗内流场进行了分析。 3.通过对冲击式水轮机转轮内部两相流流动全过程的数值模拟，找到本文研究水轮机内部存在的三种不良流动现象，并给予合理的解释，最后针对每一种不良流动给出合理的解决方案，并分析各种方案的可行性。结果表明，配水管中支路突然转折是造成配水管中流动不均匀的原因，喷嘴内绝大部分流动损失产生在喷嘴出口的薄壁小孔口出流处，数值计算的喷针行程与流量关系曲线比理论值偏低，但大体趋势相同。本文研究冲击式水轮机内部一共存在三种不良流动现象，分别是两射流同时流入流出同一水斗的不良流动，出水边流出流体与下一水斗背面干涉的不良流动和背面打水现象，这三种不良流动现象均可以通过适当改型或对水轮机转轮重新选型来避免。
[Abstract]:The high head hydraulic resources in the west of China are very rich in content. The impact turbine has the characteristics of adapting to the high head operation and is an indispensable model for the high head hydraulic development. However, compared with the counterattack turbine, it is very mature. The research on impingement turbine in our country is just beginning. The internal flow of impingement turbine is much more complicated than that of counterattack turbine, because the internal flow is three dimensional unsteady gas-liquid two-phase flow. When analyzing its flow characteristics, it is necessary to consider not only the interaction between gas phase and liquid phase, but also the interference between jet and jet, interference between jet and runner, and so on. These bad flow phenomena will greatly reduce the turbine productivity and efficiency, but also lead to the turbine unit instability, so the impact turbine internal flow state analysis, It is particularly important to study the existence of various undesirable flow phenomena within it. In order to analyze the internal flow of impingement turbine, a numerical simulation of the flow inside the prototype of a hydraulic bucket turbine is carried out in this paper. The main contents of this paper are as follows:. 1. Numerical simulation is carried out on the water distribution pipe of the impinging turbine, and the inhomogeneity and loss of the flow inside the nozzle are analyzed, and the relationship between the injection stroke and the flow rate of the nozzle is obtained by numerical simulation of the flow field inside the nozzle. 2. Through the numerical simulation of the two-phase flow in the impinging turbine runner, the flow state in the same bucket at the same time is analyzed, and the flow field of the different water hoppers acting on the two jets in the runner at the same time is analyzed. 3. Through the numerical simulation of the whole process of the two-phase flow in the impact-type turbine runner, it is found that there are three kinds of bad flow phenomena in the turbine, and the reasonable explanation is given. Finally, a reasonable solution for each kind of bad flow is given, and the feasibility of each scheme is analyzed. The results show that the sudden turning of the branch in the distribution pipe is the cause of the uneven flow in the distribution pipe, and most of the flow losses in the nozzle occur at the outlet of the thin wall orifice of the nozzle. The calculated curve of the relationship between the injection stroke and the flow rate is lower than the theoretical value, but the general trend is the same. In this paper, there are three kinds of bad flow phenomena in the impingement turbine. Two jets flow simultaneously into and out the same water hopper, the bad flow of the outflow fluid from the water side interferes with the back of the next bucket, and the backside water pumping phenomenon, These three bad flow phenomena can be avoided by proper modification or re-selection of turbine runner.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TK735

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