本文選題：流場 + 溫度場�。� 參考：《華北電力大學(xué)(北京)》2017年博士論文

【摘要】：油浸式電力變壓器是輸配電網(wǎng)的重要設(shè)備之一,熱點溫升關(guān)系到油浸式電力變壓器的使用壽命及運行的安全穩(wěn)定性。油浸式電力變壓器的溫升計算問題是一個電磁場、流場及溫度場相互耦合的多物理場耦合計算問題。論文圍繞油浸式電力變壓器內(nèi)部溫升計算過程中流場方程的計算問題、流固耦合傳熱問題、流場與溫度場耦合計算問題、考慮隨機特性的溫度場計算方法等問題展開研究,主要研究工作有:(1)針對穩(wěn)態(tài)流場的計算問題,推導(dǎo)了求解穩(wěn)態(tài)不可壓縮流體流動問題的最小二乘有限元離散格式,研究了基于單元剛度矩陣存儲的有限元方程計算方法,提出了基于單元剛度矩陣存儲的第一類邊界條件處理方法。以方腔頂蓋驅(qū)動流模型為基本算例分析了最小二乘有限元法計算穩(wěn)態(tài)流場方程的基本特征,驗證了計算方法的有效性。(2)針對計算瞬態(tài)流場問題時方程自由度過大、計算效率過低的問題,提出了求解瞬態(tài)流場問題的降階最小二乘有限元方法。該方法首先應(yīng)用最小二乘有限元法計算部分時刻流場的解構(gòu)成瞬像矩陣,然后對瞬像矩陣進行特征正交分解(Proper Orthogonal Decomposition,POD)提取流場的特征正交基,結(jié)合離散經(jīng)驗插值方法(Discrete Empirical Interpolation Method,DEIM)及Galerkin正交投影方法構(gòu)建求解瞬態(tài)流場方程的POD-DEIM降階計算模型。數(shù)值計算結(jié)果驗證了降階計算方法的準(zhǔn)確性及計算效率的高效性。(3)針對油浸式電力變壓器內(nèi)部溫升的計算問題,提出了一種流場與溫度場耦合有限元計算方法。該方法應(yīng)用最小二乘有限元法計算油流的流場控制方程,得到油道中的油流速度分布。構(gòu)建流固耦合傳熱問題的整場計算模型,采用流線迎風(fēng)有限元法計算整場傳熱方程,得到整場的溫度分布。通過順序耦合依次迭代計算流場及溫度場的有限元控制方程,得到最終的油流速度及整場溫度分布情況。應(yīng)用該方法計算了一臺油浸式電力變壓器局部繞組結(jié)構(gòu)模型的溫度分布,計算結(jié)果與Fluent軟件對比驗證了計算方法的準(zhǔn)確性。(4)結(jié)合油浸式電力變壓器餅式繞組的基本結(jié)構(gòu),應(yīng)用所提出的流場及溫度場耦合有限元方法分析了餅式繞組油道油流及整場溫度的分布特征。同時,結(jié)合變壓器設(shè)計理論,分析了餅式繞組水平油道高度、豎直油道寬度、分區(qū)數(shù)及入口油流速度等設(shè)計參數(shù)對繞組結(jié)構(gòu)中油流速度及溫度分布的影響,討論了油流速度分布對于繞組溫升的影響機理,為變壓器繞組散熱結(jié)構(gòu)設(shè)計及繞組溫升過熱分析提供指導(dǎo)。(5)為了研究不確定性因素對溫度場的影響,論文提出了一種求解隨機溫度場分布的降階蒙特卡洛隨機有限元方法。首先,結(jié)合POD及DEIM方法開發(fā)了一套求解非線性流場及溫度場問題的POD-DEIM降階有限元計算方法。接著,將降階計算方法與蒙特卡洛隨機有限元法結(jié)合,構(gòu)建了求解隨機溫度場問題的降階蒙特卡洛隨機有限元計算模型。應(yīng)用所提方法計算了在考慮油道入口油流速度隨機分布時油浸式電力變壓器局部繞組溫度的隨機分布,分析了局部繞組熱點溫度的統(tǒng)計分布類型,驗證了所提降階計算方法的準(zhǔn)確性及計算的高效性。
[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.
【學(xué)位授予單位】：華北電力大學(xué)(北京)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TM411

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本文編號：1995893