【作者】 张科；

【导师】 陆慧林；

【作者基本信息】 哈尔滨工业大学 ， 热能工程， 2008， 硕士

【摘要】 循环流化床燃烧技术作为一种新型高效低污染燃烧技术,在环保和劣质燃料利用等方面显示出极大的优势。循环流化床锅炉炉膛内局部高浓度颗粒聚团的传热不同于分散单颗粒,研究颗粒聚团的传热特性有着重要的意义。数值模拟了空气、烟气流过不同温度的孤立颗粒聚团时的对流换热情形,计算表明颗粒聚团总表面换热系数随着进气速度的增大和聚团温度的升高而线性增大,随着聚团空隙率的增大而加速增大,随着组成颗粒聚团的颗粒数的增加而减小。颗粒聚团与烟气的对流换热系数要大于对空气的对流换热系数。同样的初始条件下,孤立单颗粒与空气的对流换热系数高于聚团中任何一个单颗粒对空气的对流换热系数。数值模拟了在对流、辐射耦合情况下,烟气与孤立颗粒聚团的换热特性,研究表明,烟气辐射参数的选择对模拟结果影响很大,计算域的大小对模拟颗粒与气体间的辐射换热也有很大影响。颗粒聚团与烟气的总表面辐射换热系数与各影响因素的关系是:随着烟气入口速度增大而增大,且增加幅度逐渐减小;随着颗粒聚团空隙率的增大而增大,其增加幅度也逐渐变小;随着烟气温度的升高而加速增大;随着组成聚团的颗粒数的增多而曲线减小;随着颗粒表面发射率的增大而近似线性增大;随着烟气吸收系数的增大而增大。更多还原

【Abstract】 As a kind of newly high efficiency and low pollution combustion technology, the circulating-fluidized-bed combustion technology takes great advantages to others in fields of environmental protection and burning inferior fuels. In some local place with high concentration of particles in circulating fluidized bed, particle’s clusters are formed. The heat transfer characteristics of clusters are different from isolated single particles. To do research with the heat transfer characteristics of particle clusters is important.The convection heat transfer characteristics of gas (air\smog) and isolated particles cluster were numerically studied in the stream. It is found that the total surface heat transfer coefficient of cluster has a linear growth with the increase of gas velocity and cluster’s temperature, and it has an accelerate growth with the increase of porosity; it decrease with the increase of particles number in one cluster. The heat transfer capacity of cluster-to-smog is better than cluster-to-air. In the same conditions, the single isolated particle’s heat transfer capacity is better than any single particle in cluster.The combined heat transfer (convection and radiation) characteristics of smog and particle cluster were numerically studied in the stream, it is found that the radiation parameters of the smog affects a lot, the calculation volume is important when simulating the radiation heat transfer between particle’s cluster and gas. The radiation heat transfer characteristics of particle cluster are affected by some factors as following: The total surface radiation heat transfer coefficient increase with the increase of velocity of the smog and the growth of cluster’s porosity, but the increase speed slow down. And the Total surface radiation heat transfer coefficient has an accelerate increase with the growth of smog temperature, and it decrease as the particle number increase in one cluster, it has an approximate linear growth with the increase of particle’s emission rate. The total surface radiation heat transfer coefficient increase as the smog’s absorption coefficient increases.更多还原