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LU Junfu YUE Guangxi YANG Hairui ZHANG Jiansheng YU Long ZHANG Man YANG Zhongming 《Frontiers in Energy》2008,2(2):134
The future of circulating fluidized bed (CFB) combustion technology is in raising the steam parameters to supercritical levels. Understanding the heat flux distribution on the water wall is one of the most important issues in the design and operation of supercritical pressure CFB boilers. In the present paper, the finite element analysis (FEA) method is adopted to predict the heat transfer coefficient as well as the heat flux of the membrane wall and the results are validated by direct measurement of the temperature around the tube. Studies on the horizontal heat flux distribution were conducted in three CFB boilers with different furnace size, tube dimension and water temperature. The results are useful in supercritical pressure CFB boiler design. 相似文献
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Junfu Lu Long Yu Guangxi Yue Hairui Yang Jiansheng Zhang Man Zhang Zhongming Yang 《Frontiers of Energy and Power Engineering in China》2008,2(2):134-139
The future of circulating fluidized bed (CFB) combustion technology is in raising the steam parameters to supercritical levels.
Understanding the heat flux distribution on the water wall is one of the most important issues in the design and operation
of supercritical pressure CFB boilers. In the present paper, the finite element analysis (FEA) method is adopted to predict
the heat transfer coefficient as well as the heat flux of the membrane wall and the results are validated by direct measurement
of the temperature around the tube. Studies on the horizontal heat flux distribution were conducted in three CFB boilers with
different furnace size, tube dimension and water temperature. The results are useful in supercritical pressure CFB boiler
design.
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Translated from Journal of Power Engineering, 2007, 27(3): 336–340 [译自: 动力工程] 相似文献
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J.F. Lu J.S. Zhang G.X. Yue Q. Liu L. Yu X.D. Lin W.J. Li Y. Tang T.Y. Luo R.S. Ge 《亚洲传热研究》2002,31(7):540-550
Knowledge of heat transfer coefficients is important in the design and operation of CFB boilers. It is the key to determining the area and the layout of the heat transfer surfaces in a CFB furnace. Local bulk density has a close relationship to the local heat transfer coefficient. Using a heat flux probe and bulk density sampling probe, the local bed to wall heat transfer coefficient in the furnace of a 75 t/h CFB boiler was measured. According to the experimental results and theoretical analysis of the facts that influence the heat transfer, the heat transfer coefficient calculation method for the CFB furnace was developed. The heat transfer surface configuration, heating condition, and the material density are considered in this method. The calculation method has been used in the design of CFB boilers with a capacity from 130 t/h to 420 t/h. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 540–550, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10056 相似文献
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根据300MW循环流化床(CFB)锅炉现场测试数据并结合以往CFB锅炉传热系数的研究成果,建立了屏式受热面烟气侧的传热模型,包括辐射传热模型和对流传热半经验公式.利用该模型对某300MWCFB锅炉在94%锅炉最大连续蒸发量(BMCR)工况下炉膛内屏式受热面的传热系数进行了计算,分析了屏式受热面管间节距、炉膛温度、工质温度、壁面黑度及烟气速度等因素对传热系数的影响.结果表明:烟气速度、炉膛温度和壁面黑度对传热系数的影响较大,所建立的传热模型能够合理地反映主要因素对CFB锅炉屏式受热面传热的影响. 相似文献
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In the present work, the heat transfer study focuses on assessment of the impact of bed temperature on the local heat transfer characteristic between a fluidized bed and vertical rifled tubes (38mm-O.D.) in a commercial circulating fluidized bed (CFB) boiler. Heat transfer behavior in a 1296t/h supercritical CFB furnace has been analyzed for Geldart B particle with Sauter mean diameter of 0.219 and 0.246mm. The heat transfer experiments were conducted for the active heat transfer surface in the form of membrane tube with a longitudinal fin at the tube crest under the normal operating conditions of CFB boiler. A heat transfer analysis of CFB boiler with detailed consideration of the bed-to-wall heat transfer coefficient and the contribution of heat transfer mechanisms inside furnace chamber were investigated using mechanistic heat transfer model based on cluster renewal approach. The predicted values of heat transfer coefficient are compared with empirical correlation for CFB units in large-scale. 相似文献
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对循环流化床锅炉内水冷壁的传热机理进行了分析,验证了循环流化床炉内受热面的传热计算经验公式,可供设计、调试和运行时参考。 相似文献
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炉膛中间截面边界条件对双切圆锅炉空气动力场计算的影响 总被引:1,自引:1,他引:0
大容量超超临界锅炉广泛采用单炉膛双切圆的空气动力组织方式,在计算流体力学软件FLUENT平台上,针对1GW超超临界单炉膛双切圆锅炉,计算了全炉膛和炉膛中间截面边界条件设为对称面和边壁条件的炉内空气动力场。计算表明,与标准κ-ε双方程模型相比雷诺应力模型(RSM)具有更高的计算精度;中间截面采用对称边界条件时,其流场分布规律与全炉膛模拟结果相似;中间截面为边壁条件时炉膛中间截面附近流速降低,但对整个炉膛流场影响较小;中间截面采用这两种边界条件均会导致1#、6#角射流衰减缓慢而冲刷炉膛前墙中间水冷壁。 相似文献
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目前,燃煤锅炉三维CFD数值模拟中对炉膛水冷壁传热分布的预测大都基于给定的壁面温度边界条件。然而,此方法无法体现锅炉运行状态对壁面传热与壁温分布的影响。提出了一种基于锅炉烟气侧放热与汽水侧吸热间热平衡关系的壁面传热计算方法,并重点讨论了壁面传热系数的物理意义及取值方法。研究发现,壁面传热系数基本由壁面结渣状态决定,因此可根据壁面渣层的传热系数确定。本文方法将影响壁面传热的关键因素合理地体现在计算过程中,同时在模型复杂性与工程适用性之间保持了合理的平衡。采用此方法对一台320 MW锅炉的燃烧与传热分布进行了数值模拟,水冷壁吸热量的预测结果与锅炉运行数据吻合良好。 相似文献
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针对某75 t/h循环流化床锅炉炉膛出口NOx排放超标问题进行分析探讨,以合理的低氮燃烧控制技术为主,辅以SNCR烟气脱硝技术,争取达到NO x超净排放要求。采用CPFD计算方法对循环流化床锅炉炉膛内的气固流动和燃烧特性进行数值模拟,运用低过量空气燃烧法和空气分级技术对锅炉进行低氮燃烧控制,研究一、二次风配比、二次风射流、过量空气系数、循环倍率和颗粒粒径等因素对炉内燃烧及NO x排放的影响。结果表明:通过低氮燃烧控制后,炉内速度场和温度场分布均匀,炉膛出口处烟气流速增加,炉膛平均烟温和出口氧浓度降低,还原性气体CO浓度和优化前基本相同,炉膛出口NOx浓度降低,减排效果显著,为以后的锅炉运行提供实际指导经验。 相似文献
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针对国内某电厂200MW四角切圆锅炉NOx排放量较高,结渣严重的问题,利用CFD软件平台,采用数值模拟方法对其改造前后炉内燃烧过程进行研究。计算结果表明:由于附壁射流的作用,使得高温区集中在炉膛中部,有效地防止了锅炉结渣;改造后炉内有比常规燃烧方式锅炉更大的还原气氛区域,抑制了NOx的产生,使其排放降低34.6%。改造后的计算结果与试验相符的较好,所以此次数值模拟为锅炉设计、改造和运行提供理论依据。 相似文献
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提出一种基于燃烧与水动力耦合模型的锅炉蒸汽管壁温度数值模拟方法,对某660 MW超临界切圆燃烧锅炉壁温进行了计算分析。以均匀外壁温为边界条件,利用Fluent软件模拟了煤粉气固流动、燃烧和辐射等过程,获得了炉内不同位置受热管的传热热流。再以热流分布为边界,采用MATLAB软件建立了工质流动及气-壁-汽换热方程组,Fluent软件重新计算的壁温边界。通过编写模型间的网格映射函数,实现壁温的耦合计算。研究表明:壁温计算值与实测值的最大相对误差在2%以内;炉膛出口残余旋转使水平烟道左侧和右上方热流较大,高温再热器和末级过热器的外壁温沿炉宽方向呈双峰分布;高温再热器整级受热管出口壁温的峰谷差值远高于末级过热器,实际运行中应特别注意高温再热器靠烟道左侧管屏外圈管子向火侧弯头处的超温。 相似文献
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The efficient use of pulverized coal is crucial to the utility industries. The use of computational fluid dynamics (CFD)‐based numerical models has an important role in the design of new boiler furnaces or in retrofitting situations. The results of CFD simulations can be used to better understand the complex processes occurring within the boiler furnace. The use of these results to support boiler operation and training of operators requires that the CFD models can be easily accessed and the results are easily analysed. This paper discusses two ways to simulate the heat transfer process in boiler furnaces. The method directly applying CFD results is employed, in which the grid for solving the energy equation is the same as the flow grid in the CFD simulation while radiation heat transfer is solved in another relatively coarse grid. Comparison of the prediction results between CFD and Heat Transfer code (Simple model) is performed under boiler full load (100%) with one side wall fouling, as well as for different boiler loads (100, 98 and 95 per cent boiler full load, respectively). Finally, the flexible use of the results of CFD and the simple model for pulverized coal‐fired boilers is presented. To facilitate the use of the system, a user‐friendly interface was developed which enables the user to manipulate new calculations and to view results, namely performing ‘what–if’ analysis. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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