油浸式电力变压器流场及温度场耦合有限元方法研究

发布时间：2018-06-08 13:08

本文选题：流场 + 温度场　；参考：《华北电力大学(北京)》2017年博士论文

【摘要】：油浸式电力变压器是输配电网的重要设备之一,热点温升关系到油浸式电力变压器的使用寿命及运行的安全稳定性。油浸式电力变压器的温升计算问题是一个电磁场、流场及温度场相互耦合的多物理场耦合计算问题。论文围绕油浸式电力变压器内部温升计算过程中流场方程的计算问题、流固耦合传热问题、流场与温度场耦合计算问题、考虑随机特性的温度场计算方法等问题展开研究,主要研究工作有:(1)针对稳态流场的计算问题,推导了求解稳态不可压缩流体流动问题的最小二乘有限元离散格式,研究了基于单元刚度矩阵存储的有限元方程计算方法,提出了基于单元刚度矩阵存储的第一类边界条件处理方法。以方腔顶盖驱动流模型为基本算例分析了最小二乘有限元法计算稳态流场方程的基本特征,验证了计算方法的有效性。(2)针对计算瞬态流场问题时方程自由度过大、计算效率过低的问题,提出了求解瞬态流场问题的降阶最小二乘有限元方法。该方法首先应用最小二乘有限元法计算部分时刻流场的解构成瞬像矩阵,然后对瞬像矩阵进行特征正交分解(Proper Orthogonal Decomposition,POD)提取流场的特征正交基,结合离散经验插值方法(Discrete Empirical Interpolation Method,DEIM)及Galerkin正交投影方法构建求解瞬态流场方程的POD-DEIM降阶计算模型。数值计算结果验证了降阶计算方法的准确性及计算效率的高效性。(3)针对油浸式电力变压器内部温升的计算问题,提出了一种流场与温度场耦合有限元计算方法。该方法应用最小二乘有限元法计算油流的流场控制方程,得到油道中的油流速度分布。构建流固耦合传热问题的整场计算模型,采用流线迎风有限元法计算整场传热方程,得到整场的温度分布。通过顺序耦合依次迭代计算流场及温度场的有限元控制方程,得到最终的油流速度及整场温度分布情况。应用该方法计算了一台油浸式电力变压器局部绕组结构模型的温度分布,计算结果与Fluent软件对比验证了计算方法的准确性。(4)结合油浸式电力变压器饼式绕组的基本结构,应用所提出的流场及温度场耦合有限元方法分析了饼式绕组油道油流及整场温度的分布特征。同时,结合变压器设计理论,分析了饼式绕组水平油道高度、竖直油道宽度、分区数及入口油流速度等设计参数对绕组结构中油流速度及温度分布的影响,讨论了油流速度分布对于绕组温升的影响机理,为变压器绕组散热结构设计及绕组温升过热分析提供指导。(5)为了研究不确定性因素对温度场的影响,论文提出了一种求解随机温度场分布的降阶蒙特卡洛随机有限元方法。首先,结合POD及DEIM方法开发了一套求解非线性流场及温度场问题的POD-DEIM降阶有限元计算方法。接着,将降阶计算方法与蒙特卡洛随机有限元法结合,构建了求解随机温度场问题的降阶蒙特卡洛随机有限元计算模型。应用所提方法计算了在考虑油道入口油流速度随机分布时油浸式电力变压器局部绕组温度的随机分布,分析了局部绕组热点温度的统计分布类型,验证了所提降阶计算方法的准确性及计算的高效性。
[Abstract]:The oil immersed power transformer is one of the important equipment for the transmission and distribution network. The hot temperature rise is related to the life and safety stability of the oil immersed power transformer. The temperature rise calculation problem of the oil immersed power transformer is an electromagnetic field, the coupling of the flow field and the temperature field coupled with the multi physical field coupling calculation. The calculation of the flow equation in the calculation process of the internal temperature rise of the power transformer, the problem of fluid solid coupling heat transfer, the coupling calculation of the flow field and the temperature field, the calculation method of the temperature field considering the random characteristics are carried out. The main research work is as follows: (1) the steady incompressible fluid flow is derived for the calculation of the steady flow field. The finite element method of finite element method based on the element stiffness matrix storage is studied. The first kind of boundary condition treatment method based on the element stiffness matrix storage is proposed. The equation of the steady flow field is calculated by the minimum two multiplied finite element method with the square cavity top drive flow model as the basic example. The basic characteristics verify the effectiveness of the calculation method. (2) in order to solve the problem of calculating transient flow problem with large free equation and low calculation efficiency, a reduced order least square finite element method for solving transient flow problem is proposed. Then the characteristic orthogonal decomposition (Proper Orthogonal Decomposition, POD) is used to extract the characteristic orthogonal basis of the flow field, and a POD-DEIM descending order calculation model for solving the transient flow field equation is constructed with the discrete empirical interpolation method (Discrete Empirical Interpolation Method, DEIM) and Galerkin orthogonal projection method. The numerical results are verified. The accuracy of the reduced order calculation method and the efficiency of calculation efficiency are proved. (3) in view of the calculation of the internal temperature rise of the oil immersed power transformer, a finite element method of coupling the flow field and the temperature field is proposed. The method is used to calculate the flow field control equation of the oil flow by the least square finite element method, and the oil flow velocity distribution in the oil channel is obtained. The whole field calculation model of the fluid solid coupling heat transfer problem is built. The whole field heat transfer equation is calculated by the flow line upwind finite element method. The finite element control equation of the flow field and the temperature field is iteratively calculated by sequential coupling. The final oil flow velocity and the distribution of the whole field temperature are obtained. An oil is calculated by this method. The temperature distribution of the local winding structure model of the immersed power transformer and the calculation results are compared with the Fluent software to verify the accuracy of the calculation method. (4) combining the basic structure of the oil immersed power transformer pancake winding, the oil flow and the whole temperature of the cake winding oil channel are analyzed by the coupled finite element method of the flow field and the temperature field proposed. At the same time, combined with the transformer design theory, the influence of the design parameters such as the horizontal oil channel height, the vertical oil channel width, the number of zoning and the inlet oil flow velocity on the oil flow velocity and temperature distribution in the winding structure are analyzed. The influence mechanism of the oil flow velocity distribution on the winding temperature rise is discussed, which is the heat dissipation structure of the transformer winding. The design and the analysis of temperature rising and overheating of windings provide guidance. (5) in order to study the influence of uncertain factors on the temperature field, a reduced order Monte Carlo stochastic finite element method for solving the distribution of random temperature field is proposed. First, a set of POD-DEIM reduction finite order for solving the problem of non linear flow field and temperature field is developed with POD and DEIM method. Then, combining the reduced order calculation method with the Monte Carlo stochastic finite element method, a reduced order Monte Carlo stochastic finite element calculation model for the problem of random temperature field is constructed. The random distribution of local winding temperature of the oil immersed power transformer when the oil flow velocity random distribution of the oil channel inlet is taken into account is calculated. The statistical distribution types of hot spot temperature of local windings are analyzed, and the accuracy and efficiency of the proposed method are verified.
【学位授予单位】：华北电力大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM411

【参考文献】