【作者】 李春燕；

【导师】 阎维平；

【作者基本信息】 华北电力大学（河北） ， 热能工程， 2010， 博士

【摘要】 我国火力发电行业近年来投运了大量超临界压力参数发电机组,超临界锅炉水冷壁管的安全运行已经成为倍受关注的重要研究课题。本文针对某电厂600MW超临界燃煤电站锅炉,对炉膛螺旋管圈水冷壁不同标高区段的壁面热负荷、管内工质在超临界及近临界压力区的状态变化、水冷壁管及鳍片截面温度场分布、最高管壁温度的位置及不同运行方式下的壁温变化规律进行了深入的研究,具体研究内容及主要研究成果如下:(1)采用矩量法对锅炉水冷壁温度场进行数值计算。在建立螺旋管圈水冷壁及鳍片截面的二维稳态导热方程的基础上,引入矩量法的基本计算原理,证明了矩量法与变分法的等价性。采用双线性四边形单元对截面进行剖分,推导了基于矩量法的有限元数值计算式。(2)根据炉内燃烧热负荷沿炉膛高度分布的特点,对600MW超临界锅炉炉膛螺旋管圈水冷壁进行了7个区段的合理划分,建立了各区段的热量平衡方程,进行了分区段热力计算,得到了各个区段上的平均壁面热负荷。在能量平衡的基础上,对分区段热力计算的热负荷结果进行了合理修正,确定了炉膛螺旋管圈水冷壁管外壁热负荷分布。(3)对超临界及近临界条件下的7个工况共计49个水冷壁管截面进行了温度场数值计算。计算中考虑了螺旋管圈的倾斜布置和半周加热的特点,计算了管内表面传热系数沿周向的分布值。(4)根据炉膛螺旋管圈水冷壁管在炉膛各个区段的不同的绕制方式,从冷灰斗水冷壁进口联箱开始,分析了因各管的不同几何长度所造成的吸热差异,确定了吸热最多的偏差管,对各个工况条件下螺旋管圈水冷壁偏差管出口处的管壁温度进行了计算,并与该锅炉在相应运行工况下的管壁温度实际测量值进行了比较,证明了本文所采用的螺旋管圈水冷壁温度场计算模型是比较合理的,计算结果是可信的。(5)在超临界工况条件下稳态温度场计算的基础上,计算和分析了在不同启动方式下的水冷壁管壁温度变化率,结果表明,在超临界压力区管壁内侧壁温变化较快,在极热态启动时会超过运行要求的管壁温度变化率。(6)在近临界工况条件下,沿炉膛高度对管内工质的汽化过程进行逐段计算与分析,以确定传热恶化可能出现的位置;计算与分析了传热恶化所引起的管壁超温,计算表明,汽化过程出现在燃烧器区段即热负荷最高区段,当工质在两相区发生传热恶化时会造成管壁温度飞升。更多还原

【Abstract】 Many supercritical coal-fired boilers have been put into running in China in recent years. The safety operation of water-wall has become an important subject attracting concern. A 600MW supercritical boiler is studied in present paper. Heating load of spirally-wound water wall tube at different elevation and the thermal states of working medium at supercritical and near-critical conditions were determined. The temperature profiles at different running conditions were calculated, the changing characteristic of the temperature profile was analyzed, the positions of the highest temperature were determined. The research contents and results are as follows:(1) Numerical calculations of water-wall temperature profile of a 600MW supercritical boiler were conducted by the moment method. Two-dimensional heat conduction differential equations were established for the cross sections at different heights. The basic principle and calculation formula of moment method were introduced. The equivalency of matrix method and variational method has been proved. The mesh with bilinear quadrilateral grid has been generated, and numerical calculation formula of finite element based on moment method was deduced.(2)The spirally-wound water wall tube in furnace was partitioned into 7 zones along the height. The heat conservation equations for the 7 zones were established, and thermal calculations in the 7 zones were conducted and the heat loads were determined. The derived heat loads were modified based on the theory of energy balance.(3)Temperature profiles of 49 cross sections under 7 supercritical and near-critical working conditions were calculated. The characteristics of the spirally-wound water wall tube inclination arrangement and circumferentially non-uniform heating were considered. The heat convection coefficient curve along the circumferential direction was determined.(4)The heat absorption difference was analyzed based on the different wound modes of the spirally-wound water wall tube in every furnace zone. The heat absorped difference of the water-wall tube caused by the dimension difference from the entrance header to the outlet of the spirally-wound water wall tube was analyzed in present paper. The deviation tubes which have the highest heat absorption were confirmed. The outlet temperatures of deviation tubes were calculated. The calculated results and the measured results were compared. And the model of the calculation of the water-wall temperature profile was proved reasonable, and the calculation result was credible. (5)The temperature rising rates of the water-wall under different start-up modes were studied on the basis of steady temperature profile calculation under supercritical pressure. The results indicate that the inner side temperature of the water-wall changed quickly. The change rate can exceed the operation requirement obviously.(6)Under near critical condition, the vaporization process was calculated and analyzed along the height. The position of heat transfer deterioration was determined. The overheating caused by transfer deterioration was analyzed. It is indicated that vaporization happened in the burner zone of the furnace. And the heat transfer deterioration in two-phase region can lead to overheating.更多还原