基于動網(wǎng)格技術(shù)及浸潤邊界法的飛灰沉積數(shù)值模擬研究
發(fā)布時間：2019-03-05 12:57
【摘要】：鍋爐的尾部煙道和水平煙道受熱面上的飛灰沉積現(xiàn)象十分普遍。國內(nèi)外利用數(shù)值模擬方法對鍋爐內(nèi)飛灰沉積的研究由來已久。隨著對飛灰輸運、碰撞以及沉積等相關(guān)機理的深入研究,數(shù)值模型和算法的不斷改進,飛灰沉積數(shù)值模擬研究目前進入到了比較成熟的階段。早期的研究主要借助自編程代碼作為研究手段,隨著商業(yè)數(shù)值軟件如Fluent、CFX等的出現(xiàn),大量研究人員開始使用方便快捷的模塊化操作對沉積現(xiàn)象進行研究并獲得了一些成果。商業(yè)軟件在物理建模,控制方求解,兩相耦合,顆粒輸運等方面給予用戶極大的方便和一定程度的選擇,但是,在某些特殊情況下由于功能的限制并不能完全滿足用戶的要求,自編程代碼求解飛灰沉積問題仍然有著不可替代的作用。本文首先對飛灰沉積數(shù)值模擬研究方面進行了簡要的回顧和總結(jié),最后分析發(fā)現(xiàn),在沉積機理過程以及沉積判定等方面,研究內(nèi)容較為豐富,沉積過程主要涉及輸運、黏附、慣性碰撞等,而沉積判定主要有速度模型,粘度模型和力準則模型三種判定準則。研究方式主要以自編程代碼完成,也有使用商用軟件Fluent編寫UDF代碼完成飛灰沉積判定過程。本文主要通過兩種方式對飛灰沉積過程進行了研究,分別是:Fluent軟件借助UDF代碼,利用動網(wǎng)格模塊實現(xiàn)飛灰沉積過程模擬;利用C++自編程代碼,離散分步方程,借助IBM浸潤邊界法對飛灰沉積過程進行模擬。利用兩種方式得出數(shù)值計算結(jié)果之后,與沉降爐所得內(nèi)蒙古通遼褐煤灰試驗結(jié)果進行了對比比較。試驗結(jié)果顯示,隨著二次風(fēng)流速的增加,圓形探針上飛灰沉積高度逐漸增加;更改探針直徑后,沉積高度變化不大,各個時刻下小直徑探針上沉積高度略高于大直徑探針上的沉積高度。兩種數(shù)值模擬方式所得結(jié)果與試驗結(jié)果對比后發(fā)現(xiàn),在沉積高度方面,動網(wǎng)格技術(shù)所得數(shù)值結(jié)果與試驗結(jié)果貼合更好,而IBM浸潤邊界法在前期的沉積趨勢不明顯,增長緩慢,后期的增長逐漸開始與試驗結(jié)果吻合;在沉積層形貌方面,動網(wǎng)格技術(shù)的沉積層更顯光滑,但是形貌的邊界呈窄尖狀,與試驗結(jié)果不符,IBM浸潤邊界法所得的沉積層形貌略顯粗糙。動網(wǎng)格技術(shù)與IBM浸潤邊界法的計算效率相差較大,同樣為90000左右網(wǎng)格數(shù)下的模型,對同一算例,IBM浸潤邊界法計算效率比動網(wǎng)格技術(shù)快了近10倍。在實際應(yīng)用中,要根據(jù)合適的情況選取合適的數(shù)值計算方法。
[Abstract]:Fly ash deposition on the heating surface of boiler tail flue and horizontal flue is very common. The study of fly ash deposition in boiler has been studied for a long time by using numerical simulation method at home and abroad. With the in-depth study of fly ash transport, collision and deposition mechanism and the continuous improvement of numerical model and algorithm, the numerical simulation of fly ash deposition has entered a relatively mature stage. With the emergence of commercial numerical software such as Fluent,CFX, a large number of researchers began to use convenient and rapid modular operation to study the deposition phenomenon and obtained some achievements. Commercial software provides users with great convenience and a certain degree of choice in physical modeling, control solution, two-phase coupling, particle transport and so on. However, in some special cases, due to the limitation of function, it can not fully meet the requirements of users. Self-programming code still plays an irreplaceable role in solving the problem of fly ash deposition. In this paper, the numerical simulation of fly ash deposition is briefly reviewed and summarized in this paper. Finally, it is found that the deposition process is rich in deposition mechanism and deposition judgment, and the deposition process is mainly related to transport, adhesion, and so on. Inertial collision and so on. There are three criteria to determine deposition, such as velocity model, viscosity model and force criterion model. The research method is mainly completed by self-programming code, but also using commercial software Fluent to write UDF code to complete the determination process of fly ash deposition. In this paper, the process of fly ash deposition is studied in two ways: the Fluent software realizes the simulation of fly ash deposition process with the aid of UDF code and dynamic grid module; The process of fly ash deposition is simulated by using C self-programming code, discrete step equation and IBM infiltration boundary method. The numerical results obtained by two methods are compared with the experimental results of Tongliao lignite ash in Inner Mongolia obtained by settling furnace. The experimental results show that with the increase of secondary air velocity, the height of fly ash deposition on circular probe increases gradually. After changing the diameter of the probe, the deposition height does not change much, and the deposition height on the small diameter probe is slightly higher than the deposition height on the large diameter probe at each time. The results obtained by the two numerical simulation methods are compared with the experimental results. It is found that the numerical results obtained by the dynamic mesh technique agree better with the experimental results in terms of sedimentation height, while the deposition trend of the IBM infiltration boundary method is not obvious and the growth rate is slow. The growth of the later period began to coincide with the results of the experiment. In terms of the morphology of the deposition layer, the dynamic mesh technique is more smooth, but the boundary of the deposit layer is narrow pointed, which is not consistent with the experimental results. The morphology of the deposition layer obtained by the IBM infiltration boundary method is slightly rough. The computational efficiency of the moving mesh method is different from that of the IBM infiltration boundary method, which is about 90000 mesh numbers. For the same example, the computational efficiency of the IBM infiltration boundary method is nearly 10 times faster than that of the moving mesh method. In practical application, the appropriate numerical calculation method should be selected according to the appropriate situation.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TK221
，
本文編號：2434926
[Abstract]:Fly ash deposition on the heating surface of boiler tail flue and horizontal flue is very common. The study of fly ash deposition in boiler has been studied for a long time by using numerical simulation method at home and abroad. With the in-depth study of fly ash transport, collision and deposition mechanism and the continuous improvement of numerical model and algorithm, the numerical simulation of fly ash deposition has entered a relatively mature stage. With the emergence of commercial numerical software such as Fluent,CFX, a large number of researchers began to use convenient and rapid modular operation to study the deposition phenomenon and obtained some achievements. Commercial software provides users with great convenience and a certain degree of choice in physical modeling, control solution, two-phase coupling, particle transport and so on. However, in some special cases, due to the limitation of function, it can not fully meet the requirements of users. Self-programming code still plays an irreplaceable role in solving the problem of fly ash deposition. In this paper, the numerical simulation of fly ash deposition is briefly reviewed and summarized in this paper. Finally, it is found that the deposition process is rich in deposition mechanism and deposition judgment, and the deposition process is mainly related to transport, adhesion, and so on. Inertial collision and so on. There are three criteria to determine deposition, such as velocity model, viscosity model and force criterion model. The research method is mainly completed by self-programming code, but also using commercial software Fluent to write UDF code to complete the determination process of fly ash deposition. In this paper, the process of fly ash deposition is studied in two ways: the Fluent software realizes the simulation of fly ash deposition process with the aid of UDF code and dynamic grid module; The process of fly ash deposition is simulated by using C self-programming code, discrete step equation and IBM infiltration boundary method. The numerical results obtained by two methods are compared with the experimental results of Tongliao lignite ash in Inner Mongolia obtained by settling furnace. The experimental results show that with the increase of secondary air velocity, the height of fly ash deposition on circular probe increases gradually. After changing the diameter of the probe, the deposition height does not change much, and the deposition height on the small diameter probe is slightly higher than the deposition height on the large diameter probe at each time. The results obtained by the two numerical simulation methods are compared with the experimental results. It is found that the numerical results obtained by the dynamic mesh technique agree better with the experimental results in terms of sedimentation height, while the deposition trend of the IBM infiltration boundary method is not obvious and the growth rate is slow. The growth of the later period began to coincide with the results of the experiment. In terms of the morphology of the deposition layer, the dynamic mesh technique is more smooth, but the boundary of the deposit layer is narrow pointed, which is not consistent with the experimental results. The morphology of the deposition layer obtained by the IBM infiltration boundary method is slightly rough. The computational efficiency of the moving mesh method is different from that of the IBM infiltration boundary method, which is about 90000 mesh numbers. For the same example, the computational efficiency of the IBM infiltration boundary method is nearly 10 times faster than that of the moving mesh method. In practical application, the appropriate numerical calculation method should be selected according to the appropriate situation.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TK221
，
本文編號：2434926
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