【摘要】 考虑鼓泡流化床生物质气化过程多组分颗粒运动特点,建立多组分颗粒速度脉动二阶矩模型,结合化学反应动力学方法描述鼓泡流化床内生物质气化过程。模拟的气体组分结果与采用原始颗粒动理学模型的模拟结果进行了比较,并给出了两种粒径碳颗粒的浓度与温度瞬时分布。分析了两种碳颗粒的速度时均径向分布及速度脉动二阶矩时均径向分布,两种碳颗粒的速度分布一致,说明不同粒径碳颗粒混合充分。粒径较大的碳颗粒速度脉动二阶矩在轴向与径向上均较大,粒径的增加使得颗粒速度脉动增强。模拟统计了计算域内两种颗粒的速度脉动各向异性随颗粒浓度变化关系,各向异性随颗粒浓度的增加逐渐减弱,粒径较大的碳颗粒在计算域内的各向异性平均效果不如粒径较小的碳颗粒明显。更多还原

【Abstract】 Second-order moment(SOM) model considering anisotropic movements of multiphase particles was presented. Biomass gasification processes in bubbling fluidized beds were described combining with a chemical reaction kinetic method. The simulated gas molar fractions were compared with kinetic theory of granular flow(KTGF) model and SOM model. The instantaneous distribution of concentration and temperature of two char particles was given with their velocities analyzed. The results show that the velocity distribution was similar between these two particles, which indicate that the two char particles were well mixed. The second-order moment of the two char particles were analyzed, which is larger for the particle with diameter of 2.0 mm in axial and radial directions. Velocity fluctuation is enhanced with the increase of particle size. The anisotropy of velocity fluctuation for the two char particles was simulated as a function of char particle concentration, which is weakened with particle concentration increase. Moreover, the anisotropy of the char particle with smaller diameter is more obvious in the computational domain.更多还原