循环流化床锅炉二次送风结构影响的数值模拟

Effect of Secondary Air Injecting Design on Hydrodynamics of Circulating Fluidized Bed Boiler

利用CFD软件Fluent,基于颗粒动力学理论的双流体模型对循环流化床锅炉的3种二次风送风结构对炉膛内气-固两相流宏观流动特性的影响进行数值模拟,将3种结构下的计算结果进行对比分析。结果表明:二次风通常采用90°垂直入射的情况下,炉膛内颗粒的环-核分布结构及上稀下浓的分布不均匀性达到最大;二次风进口入射角为与轴向方向成60°向上入射情况下,炉膛内颗粒主要分布在炉膛中上部区域,不均匀程度减小,最有利于炉膛内的燃烧和提高传热效率,同时得到二次风的射流深度最大;二次风送入结构为渐缩型入射口的情况时,二次风射流深度最小,炉膛内偏流现象明显,在本文的操作条件下,并没有达到喷射的设计效果,还有待于进一步的研究。

Using the two-fluid model combining with the kinetic theory of granular flow, the numerical simulation of effect of secondary air injecting design on gas-solid two-phase flow field was performed for a circulating fluidized bed boiler. The results showed that when the air injecting design was perpendicular to the wall of furnace along the radial direction. The solid phase concentration distribution in the radial direction showed a annular-core flow flame and the solid concentration was low in the upward region and high in the bottom region along axial direction. The gradation of non-uniform was the greatest. While the angle between the injecting and axial direction was 60° , the solids mainly distributed in the upper-and-middle region of furnace and the gradation of non-uniform decreased, which was beneficial to the combustion and heat transfer efficiency. Moreover, the jet＇s length was the largest. If the secondary air injecting section was designed the type of gradually reduction, the jet＇ s length was the smallest and there was serious bias flow and operating on this condition, the optimum design goal of spurting didn＇t reach.