中比转数混流式水轮机尾水管压力脉动特性研究

发布时间：2018-04-04 07:44

本文选题：混流式水轮机　切入点：压力脉动　出处：《哈尔滨工业大学》2014年硕士论文

【摘要】：随着水力资源开发及混流式水轮机设计与制造技术的逐步提高，混流式水轮机逐渐向着中比转数、大功率方向发展，对机组的稳定、安全运行有着重要影响的压力脉动问题已经得到广大学者的重视。本文针对尾水管涡带产生的压力脉动问题，，采用瞬态全流道数值模拟方法对压力脉动在尾水管处的规律进行分析，并采用部分流道的模拟得出压力脉动的成分和来源。为了实现上述目的，本文对中比转数模型水轮机4个导叶开度工况的内部流场进行了数值模拟，通过定常数值模拟研究水力特性情况，验证数值计算的准确性和流场各参数的分布情况，通过非定常数值模拟得到水轮机压力脉动随时间的变化，分析混流式水轮机的压力脉动在各区域的频率分布，研究各主要脉动频率成分原因。具体的研究内容包括以下几个方面：首先，采用定常方法对小开度、最优开度、和两个大开度等4个工况下水轮机内部流场进行了数值模拟，研究各工况流动情况，分析流动状态产生的不稳定原因，研究各个工况主要外特性和流场中的流动变化规律，得到各工况的水力效率等关键信息。其次，对各开度工况进行瞬态的全流道数值模拟研究，获得了流道内各部件所布测点的压力脉动数据。为了更好的分析压力脉动能量分布，采用快速傅里叶变换(FFT)方法对得到的压力脉动进行处理，将脉动的时域信息转化到频域上。研究各测点在频域上的共有特性，分析尾水管主要频率压力脉动的是由尾水涡带的旋转运动产生的。再次，在研究部分流道压力脉动时，对各开度的工况的无蜗壳流道和无固定导叶流道进行数值模拟研究，获得各测点的压力脉动值，并对其进行FFT方法处理，将时域的脉动信息转换到频谱图上，分析各区域的主要脉动频率，与全流道的各区域的主要频率对比，发现上游部件的结构在尾水管处将不产生新频率的压力脉动。
[Abstract]:With the development of hydraulic resources and the gradual improvement of Francis turbine design and manufacture technology, the Francis turbine is developing towards the direction of middle ratio and high power, which is stable to the unit.The problem of pressure fluctuation, which has an important effect on safe operation, has been paid more attention by many scholars.In this paper, the transient full-channel numerical simulation method is used to analyze the law of pressure pulsation in the tail water pipe, and the components and sources of pressure pulsation are obtained by the simulation of some channels.In order to achieve the above purpose, the internal flow field of the four guide vane opening conditions of the medium-specific rotation model hydraulic turbine is numerically simulated in this paper, and the hydraulic characteristics of the turbine are studied by the steady numerical simulation.The accuracy of numerical calculation and the distribution of flow field parameters are verified. The variation of turbine pressure pulsation with time is obtained by unsteady numerical simulation, and the frequency distribution of pressure pulsation in each region of Francis turbine is analyzed.The main pulsating frequency components were studied.The specific research contents include the following aspects:Firstly, the flow field in the turbine under four operating conditions, such as small opening, optimal opening, and two large opening, is numerically simulated by using the steady method, and the flow situation of each working condition is studied, and the reasons for the instability of the flow state are analyzed.The main external characteristics of each working condition and the law of flow variation in the flow field are studied, and the key information such as hydraulic efficiency of each condition is obtained.Secondly, the transient full-channel numerical simulation is carried out to obtain the pressure pulsation data of the measured points in the flow channel.In order to better analyze the energy distribution of pressure fluctuation, the fast Fourier transform (FFT) method is used to deal with the pressure fluctuation, and the time domain information of the pulse is converted to the frequency domain.The common characteristics of each measuring point in frequency domain are studied. It is analyzed that the main frequency pressure pulsation of the draft tube is caused by the rotating motion of the tailwater vortex belt.Thirdly, when the pressure pulsation of some channels is studied, numerical simulation is carried out on the non-volute flow channel and the non-fixed guide vane runner under various open working conditions, and the pressure pulsation values of each measuring point are obtained, and the FFT method is used to deal with the pressure pulsation.The pulsation information in time domain is converted to the spectrum chart, and the main pulsation frequency of each region is analyzed. Compared with the main frequency of each region of the whole channel, it is found that the structure of upstream component will not produce pressure fluctuation of new frequency in the tailwater pipe.
【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】：TK733.1

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