冲击式水轮机流固耦合数值模拟研究

发布时间：2018-05-18 12:54

本文选题：水斗式水轮机 + 过渡过程　；参考：《武汉大学》2017年硕士论文

【摘要】：随着冲击式水轮机比转速、尺寸、单机容量不断增大,大量新型材料的使用导致水轮机的相对刚度降低,高速射流的冲击力作用以及转轮自身的高速旋转所引起的结构振动、水斗表面局部损坏、水斗整体断裂问题十分突出,严重影响到水轮机运行的安全和稳定,引起了国内外广大研究人员的关注。目前,国内外关于冲击式水轮机转轮结构力学性能的研究欠深入,一般选取某一瞬时状态进行静力分析,然后以此为基础进行转轮结构的模态分析,在多喷嘴水斗式水轮机结构方面的研究较少。本文在前人研究的基础上,采用流固耦合数值模拟方法,首先研究了冲击式水轮机在启动工况、额定运行工况、飞逸工况的水力特性和结构特性;然后针对多喷嘴水斗式水轮机进行了流固耦合分析,并对转轮结构进行模态分析。这是对冲击式水轮机转轮结构动力学特性研究的一种探索和尝试。本文以CJA475-W-83冲击式水轮机转轮结构为研究对象,在给定水轮机水力条件下进行转轮三维建模、流场分析、静力分析,在此基础上,探究冲击式水轮机在不同工作状态下的振动特性:(1)转轮流场分析。考虑水气二相流作用,在Fluent软件中建立转轮流场三维瞬态分析模型,进行流体流态计算,得到额定运行工况、启动过程、飞逸过程下的流态和压力分布规律;然后计算多喷嘴水斗式水轮机稳定运行工况下不同水头、不同开度情况下的水力特性,为之后转轮结构有限元分析提供荷载依据。(2)转轮结构静力分析。运用单向流固耦合的方式,提取流场分析的结果作为转轮静力分析的荷载,利用Ansys Workbench中的Static Structural模块对转轮结构进行静力分析,得到启动、额定、飞逸工况下转轮结构的应力、位移分布规律,为之后工作状态下的结构振动模态分析提供应力依据。(3)转轮结构模态分析。在静力分析的基础上,对转轮结构进行自由状态、约束状态和工作状态下的模态分析,得到转轮静频、动频以及各阶振型。通过分析频率,得到了转轮结构的固有频域范围;通过分析振型,得到了转轮结构的振动规律;同时,探究了转轮转速和射流冲击力对冲击式水轮机转轮结构模态的影响,结合冲击式水轮机的运行工况判断转轮结构共振的可能性。本文模拟了冲击式水轮机过渡过程中的水力特性和结构动力特性,并针对多喷嘴水斗式水轮机进行了分析,所得结论有助于指导水轮机设计和运行,且对实际工程有参考价值。
[Abstract]:With the increase of the speed, size and single machine capacity of the impact turbine, the use of a large number of new materials leads to the reduction of the relative stiffness of the turbine, the impact of the high speed jet and the high-speed rotation of the wheel, and the local damage to the surface of the bucket, and the problem of the overall fracture of the bucket is very prominent, which seriously affects the water. The safety and stability of the turbine operation has aroused the attention of the large number of researchers at home and abroad. At present, the research on the mechanical properties of the shock turbine runner is not deep, and the static analysis is generally selected for a certain instantaneous state, and then on the basis of the modal analysis of the rotary wheel structure, in the multi nozzle bucket turbine junction. In this paper, on the basis of the previous research, the hydraulic and solid coupling numerical simulation method is used to study the hydraulic and structural characteristics of the impact turbine at the starting, rated operating and flight conditions, and then the fluid solid coupling analysis is carried out for the multi nozzle water turbine and the structure of the runner is carried out. Modal analysis. This is a kind of exploration and attempt to study the dynamic characteristics of the structure of the shock turbine runner. This paper takes the structure of the CJA475-W-83 shock turbine runner as the research object. The three dimensional modeling, flow field analysis and static analysis are carried out under the hydraulic condition of a given hydraulic turbine. On this basis, the impact hydraulic turbine is studied in different ways. The vibration characteristics of the working state are: (1) the analysis of the flow field of the runner. Considering the effect of two phase flow of water and gas, the three-dimensional transient analysis model of the runner flow field is established in the Fluent software, the flow state is calculated, the flow state and pressure distribution under the rated operating condition, the starting process, the runaway process and the pressure distribution are obtained, and then the steady transportation of the multi nozzle water turbine is calculated. The hydraulic characteristics of different water heads and different opening conditions are provided for the finite element analysis of the rear wheel structure. (2) static analysis of the structure of the runner. Using the unidirectional fluid solid coupling method, the result of the analysis of the flow field is extracted as the load of the wheel static analysis, and the Static Structural module in the Ansys Workbench is used for the wheel. The structure is static analysis, and the stress and displacement distribution law of the runner structure in the starting, rated and flying conditions are obtained. (3) the modal analysis of the structural vibration of the runner. On the basis of static analysis, the free state, the constraint state and the working state of the wheel structure are carried out. The static frequency, dynamic frequency and various modes of the runner are obtained. By analyzing the frequency, the natural frequency range of the wheel structure is obtained. By analyzing the vibration mode, the vibration law of the wheel structure is obtained. At the same time, the influence of the rotating wheel speed and the impingement force on the structure mode of the shock turbine runner is explored, and the transport of the shock turbine is combined. This paper simulates the hydraulic and structural dynamic characteristics of the hydraulic turbine during the transition process, and analyzes the multi nozzle water turbine. The conclusions are helpful to guide the design and operation of the turbine, and have a reference value to the actual project.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV734.1

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