超超临界锅炉受热面管失效概率与温度场数值模拟研究

发布时间：2018-05-19 00:35

本文选题：数值模拟 + 温度场　；参考：《中国矿业大学》2015年硕士论文

【摘要】：超超临界机组通过提高蒸汽参数来提高燃煤机组的发电效率,有效降低供电煤耗,实现节能与低污染排放,得到快速的发展。然而装机机组逐年增大,管道运行工况一再恶化,使得管道爆管事故时有发生,给电厂正常运行带来极大的经济损失。针对大型机组,仅用原有的热偏差及壁温计算方法已不适用。鉴于此,本文采用数值模拟和实验相结合的分析方法对超超临界机组下炉膛燃烧情况及上炉膛受热面温度分布进行研究。本文运用层次分析法对超超临界锅炉的失效模式及导致失效的各因素进行了分析。通过建立水冷壁、过热器、再热器的失效模型,对失效模型构造相对应的判断矩阵进而求出各失效因素的权重,得出了不同类型受热面的失效因素相对重要性,为后续有针对性的研究受热面失效原因提供依据。对于炉膛燃烧模拟,通过对炉膛1:1实体建模计算与分析,详细探讨了进煤量、过量空气、煤粉细度、煤种及工况变化对燃烧的影响作用,结果表明:在二次风一定的情况下,炉膛整体温度随着煤量的增加温度呈先升高后降低的趋势,进煤量的调整仅仅使各个部分的温度改变,对切圆形态影响不大,11kg/s进煤量燃烧效果最好。进煤量一定的情况下,炉膛温度和峰值温度随着过量空气量的增加先升高而后降低,在过量空气系数为1.15时煤粉燃烧较为充分。煤粉越细进行燃烧的表面积越大,煤粉本身的热阻越小,加热煤粉至着火温度所需要的时间越短,燃烧越完全,可以在炉膛较低位置开始很剧烈的燃烧并形成较高的炉膛温度。低位发热量高与挥发分含量高的煤种形成的炉膛整体温度较高。高负荷工况下的燃尽区发热多,炉膛出口温度较高,辐射强度较大。本文采用解析计算与数值模拟相结合的方法考察了不同高度下炉膛水冷壁的温度分布、应力分布,并且找出了水冷壁的危险区域。结果表明:水冷壁的截面最高温度在向火侧鳍片端部位置,其温度分布随着炉膛高度的增加呈先升高后降低的趋势,在高度为38m处达到最高值。管壁截面最高温度出现在向火侧最高点处,最大应力位置为背火侧管壁与鳍片接触面,水冷壁危险区域为上下燃烧器中间部位。对于上炉膛受热面模拟,本文基于燃烧模拟得到受热面所处的管屏区进口的烟气温度和速度边界,将下炉膛烟气组分通过运输方程传递上去,在此基础上对管屏区进行流固共轭传热分析,得到各工况下管道外壁温度分布及波动情况并且与电厂实测数据进行了验证。结果表明:一级过热器与三级过热器类似,高温区出现炉膛中心处,变工况情况下管外壁温度的波动幅度由炉膛中心向炉膛两侧逐渐减小,炉膛中心处波动最大。从二级再热器以上开始,高温区由炉膛中心向炉膛两侧扩展,并且工况越低扩展越迅速,扩展的距离越长。温度波动大的区域也随着炉膛高度的增加从炉膛中心向两侧扩展,危险区域从炉膛中心附近向炉膛两侧扩展。通过对锅炉已发生的过热器失效管道及水冷壁焊缝裂纹进行失效分析,找出了其相应的失效原因,验证了失效模型建立和模拟结果的正确性,提出了改进措施。
[Abstract]:The super supercritical unit improves the efficiency of the power generation by improving the steam parameters, effectively reducing the power supply coal consumption, realizing the energy saving and low pollution emission, and gets the rapid development. However, the installed unit is increasing year by year, the running condition of the pipeline is deteriorating again and again, which makes the pipe burst accident happen and brings great economy to the normal operation of the power plant. For large units, only the original thermal deviation and wall temperature calculation method is not applicable. In view of this, this paper uses numerical simulation and experimental analysis method to study the combustion of the lower furnace and the temperature distribution of the heating surface in the upper furnace. This paper uses the analytic hierarchy process to the failure mode of ultra supercritical boiler. Through the establishment of the failure model of water cooling wall, superheater and reheater, the corresponding judgement matrix of the failure model is constructed and the weight of each failure factor is obtained. The relative importance of the failure factors of different types of heat surface is obtained, which is the cause for the subsequent research on the failure of the heating surface. For the furnace combustion simulation, the effect of coal intake, excess air, pulverized coal fineness, coal and working conditions on combustion is discussed in detail through the calculation and analysis of 1:1 solid modeling in the furnace chamber. The results show that the overall temperature of the furnace increases first and then decreases with the increase of coal quantity in the case of two times of wind. The adjustment of coal intake is only the change of the temperature of each part, which has little influence on the tangential shape. The effect of 11kg/s coal intake is the best. Under the condition of certain amount of coal intake, the furnace temperature and peak temperature rise first and then decrease with the increase of excess air. The pulverized coal is finer when the excess air coefficient is 1.15, the finer the pulverized coal is. The larger the surface area of the row combustion, the smaller the thermal resistance of the pulverized coal, the shorter the time to heat the pulverized coal to the ignition temperature, the more complete the combustion, the higher the combustion and the higher furnace temperature in the lower chamber of the hearth, the higher the overall temperature of the hearth formed by the high calorific value and the high volatile content of the coal. The temperature of the furnace outlet is high and the furnace outlet temperature is high and the radiation intensity is high. In this paper, the temperature distribution and stress distribution of the water cold wall at the furnace chamber at different heights are investigated by the method of analytical calculation and numerical simulation, and the dangerous area of the water wall is found. The results show that the highest temperature of the section of the water wall is on the side fin of the fire side. With the increase of the furnace height, the temperature distribution at the height of the furnace increases first and then decreases, and reaches the highest value at the height of 38m. The highest temperature of the section of the tube wall appears at the highest point of the fire side, the maximum stress position is the contact surface of the back fire side tube wall and the fin, and the dangerous area of the water wall is the middle part of the upper and lower burner. On the basis of combustion simulation, the temperature and velocity boundary of the inlet of the tube screen area of the heated surface is obtained based on the combustion simulation, and the flue gas components in the lower furnace are passed through the transport equation. On this basis, the flow solid conjugate heat transfer analysis is carried out on the tube screen area, and the temperature distribution and fluctuation of the outer wall of the pipe are obtained and the power plant is obtained. The measured data are verified. The results show that the first class superheater is similar to the three stage superheater, and the high temperature zone appears at the hearth center. The fluctuation range of the outer wall temperature is gradually reduced from the furnace center to the hearth, and the center of the furnace fluctuates most. From the two reheater, the high temperature zone is from the furnace center to the furnace two. The larger the range of temperature fluctuates from the furnace center to both sides of the furnace center, and the danger zone extends from the furnace center to the hearth. The failure analysis of the superheater failure pipeline and the water wall weld crack has been carried out. The corresponding failure causes were found out, the correctness of the failure model establishment and the simulation results were verified, and the improvement measures were put forward.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM621.2

【参考文献】