循环流化床锅炉炉膛内气固两相流的数值模拟

Numerical Simulation of the Gas-solid Flow in 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(CFBB)炉膛内气固两相流的宏观流动特性进行了数值模拟。将炉膛压降沿轴向的分布规律与理论值对比,验证了本次数值模拟计算的准确性。通过定性与定量分析,得到炉膛内颗粒固含率呈中心高,边壁低的"环-核"流动结构及颗粒轴向速度中心处向上,边壁处向下的内循环流动形式。另外,改变操作气速与质量循环流率,沿轴向炉膛中下部区域及沿径向边壁区颗粒固含率分布的影响比较显著。同时,操作条件对颗粒轴向速度的影响都表现为中心区域颗粒向上速度变化的效果要显著于边壁处向下运动速度的变化。边壁处的气固两相流动规律还有待于进一步研究。

Using the CFD software Fluent,based on the two-fluid model combining with the kinetic theory of granular flow,the numerical simulation of gas-solid two-phase flow field was performed for a circulating fluidized bed boiler.Comparison of the simulated pressure drop with the theoretical value tests the validation of this numerical simulation.Through the qualitative and quantitative analysis,it is analyzed that the particle concentration distribution shows a core-annular flow frame where the solid is denser in the annular region than core region and the particle axial velocity shows the internal circulation pattern that the particle movement is upward in the core zone and down in the annulus zone.In addition,under different operating condition,particle volume fraction distribution is affected prominently at the lower-middle zone along the axial direction and at the wall area along the radial direction.Furthermore,the effect of operating condition on the particle velocity reflects that the changing of upward particle velocity at the core area is more obvious than at the wall area.The gas-solid flow pattern at the wall area needs further investigation.