【摘要】：蒸汽管道是電廠的重要組成部分,而三通應(yīng)力比較復(fù)雜,是主蒸汽管道和再熱蒸汽管道強(qiáng)度分析的主要元件,需要給予特殊關(guān)注。由于三通幾何結(jié)構(gòu)的復(fù)雜性,當(dāng)三通內(nèi)流體發(fā)生瞬態(tài)流動(dòng)時(shí),三通的主管與支管交貫處附近形成分離區(qū),管道橫截面上產(chǎn)生的二次流導(dǎo)致三通內(nèi)流體的速度場(chǎng)、壓力場(chǎng)發(fā)生變化,三通交貫處附近的對(duì)流傳熱系數(shù)亦會(huì)顯著變化。當(dāng)研究主蒸汽三通熱應(yīng)力以及壽命時(shí),工程實(shí)踐中通常是依據(jù)圓形直管傳熱關(guān)聯(lián)式得到的三通主管與支管平均對(duì)流傳熱系數(shù)常數(shù)作為邊界條件,繼而對(duì)三通進(jìn)行熱應(yīng)力和壽命分析。那么,三通幾何結(jié)構(gòu)復(fù)雜性產(chǎn)生的沿程分布不均的對(duì)流傳熱系數(shù)與工程實(shí)踐中常常采用的恒定對(duì)流傳熱系數(shù)相比,兩種邊界條件對(duì)三通熱應(yīng)力和壽命的計(jì)算有何差距,需要詳細(xì)分析和驗(yàn)證。本文依托于“基于典型失效模式的超(超)臨界電站鍋爐事故預(yù)防關(guān)鍵技術(shù)研究”課題,對(duì)三通的傳熱特性、熱應(yīng)力和壽命進(jìn)行了分析。本文以某電站300MW機(jī)組為范例,通過(guò)確定三通考核點(diǎn)在鍋爐啟停過(guò)程中的內(nèi)壓應(yīng)力與熱應(yīng)力的合成應(yīng)力強(qiáng)度隨時(shí)間變化曲線,得到三通考核點(diǎn)在鍋爐啟停過(guò)程中的谷值時(shí)刻和峰值時(shí)刻;采用FLUENT流體軟件,對(duì)谷值時(shí)刻和峰值時(shí)刻的流體與三通的共軛傳熱進(jìn)行數(shù)值模擬,探討三通內(nèi)流體與壁面的對(duì)流傳熱系數(shù)的沿程變化規(guī)律;采用ANSYS有限元軟件,分別以FLUENT數(shù)值模擬得到的沿程變化對(duì)流傳熱系數(shù)作為三通內(nèi)壁面施加條件以及以圓形直管強(qiáng)制對(duì)流傳熱關(guān)聯(lián)式得到的三通主管與支管的恒定平均對(duì)流傳熱系數(shù)作為三通內(nèi)壁面施加條件,得到峰值工況與谷值工況的熱應(yīng)力;分別采用ASME疲勞壽命計(jì)算方法和疲勞-蠕變交合作用下的壽命計(jì)算方法,對(duì)兩種壁面?zhèn)鳠徇吔鐥l件下的三通進(jìn)行壽命計(jì)算和對(duì)比,研究三通復(fù)雜的幾何結(jié)構(gòu)導(dǎo)致的沿程對(duì)流傳熱系數(shù)分布不均,對(duì)三通熱應(yīng)力以及壽命的計(jì)算結(jié)果是否存在差異,以及它們的差異程度如何,從而為以后工程中對(duì)三通熱應(yīng)力以及壽命計(jì)算的進(jìn)一步修正和完善提供合理的依據(jù)。
[Abstract]:Steam pipeline is an important part of power plant, and the three-way stress is complex, which is the main component of strength analysis of main steam pipeline and reheat steam pipeline, which needs special attention. Because of the complexity of the geometry structure of the three-way, when the transient flow occurs in the three-way, a separation zone is formed near the intersection between the supervisor of the three-way and the branch pipe, and the secondary flow on the cross section of the pipeline leads to the velocity field of the fluid in the three-way. When the pressure field changes, the convection heat transfer coefficient near the junction of the three links will also change significantly. When studying the thermal stress and life of the main steam three-way connection, the average convection heat transfer coefficient constant of the three-way pipe and the branch pipe is usually used as the boundary condition in engineering practice according to the heat transfer correlation formula of the circular straight pipe. Then the thermal stress and life of the three links are analyzed. So, compared with the constant convection heat transfer coefficient which is often used in engineering practice, the difference between the two boundary conditions and the calculation of thermal stress and life of the three-way connection is different from the convection heat transfer coefficient with uneven distribution along the path caused by the complexity of the geometry structure of the three-way connection. Need detailed analysis and validation. In this paper, the heat transfer characteristics, thermal stress and service life of three links are analyzed on the basis of "study on the key Technology of accident Prevention of Super-critical Boiler based on typical failure Mode". Taking the 300MW unit of a power station as an example, the variation curve of internal pressure stress and thermal stress intensity with time is determined by determining the internal pressure stress and thermal stress of the three-way test point in the process of boiler starting and stopping. The valley value and peak value of the three-way check point in the process of boiler start and stop are obtained. By using FLUENT software, the conjugate heat transfer between the fluid and the three-way is simulated at the valley time and the peak time, and the variation law of the convection heat transfer coefficient between the fluid and the wall in the three-way is discussed. Using ANSYS finite element software, The constant average convection heat transfer coefficient obtained by FLUENT numerical simulation is used as the condition of applying convection heat transfer coefficient along the inner wall of the three way and the constant average convection heat transfer coefficient between the tube and branch tube is obtained by the correlation of forced convection heat transfer in circular straight tube. Imposing conditions on the inner wall of the three links, The thermal stress of peak and valley conditions is obtained. The ASME fatigue life calculation method and the fatigue creep interaction method are used to calculate and compare the life of the three links under two wall heat transfer boundary conditions. This paper studies the uneven distribution of the convection heat transfer coefficient along the path caused by the complicated geometry structure of the three links, whether there are differences in the calculation results of the thermal stress and lifetime of the three links, and the degree of their differences. It provides a reasonable basis for the further modification and perfection of the thermal stress and life calculation of the three-way connection in the future engineering.
【學(xué)位授予單位】：上海發(fā)電設(shè)備成套設(shè)計(jì)研究院
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TM621.72;TK124

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