催化裂解反应器是重油深度利用生产轻质烯烃的重要工具，而反应器内部气固两相流动和混合特性对反应效果具有重要影响。为了获得变径快速流化床催化裂解反应器中复杂的相间、相内相互作用及流动行为，采用双流体模拟方法对流化床内气固流动行为进行模拟，以探究其内部气固流动特性。通过与现有实验数据进行对比，验证了模拟方法的可行性/准确性。并进一步研究了喷嘴气体流量和床层结构参数对颗粒流动的影响。结果表明，增加气体流量在一定程度上可以缓解颗粒在突扩段的聚集，使颗粒在反应器内分布更加均匀。而气体流量对上部区域的颗粒浓度分布影响不大。反应器结构参数优化的结果显示，流化床整体结构中渐扩段上部直径和底部直径呈现一定倾角更有利于颗粒在反应器内的均匀分布，使气固混合得到改善，有利于催化裂化过程的进行。

Catalytic cracking reactors serve as crucial facilities for enhancing heavy oil utilization through light olefin production, where gas-solid hydrodynamics significantly influence reaction efficiency. This study investigated complex inter-phase and intra-phase interactions and flow behaviors in a diameter-transformed fast fluidized bed catalytic cracking reactor using a two-fluid model approach. The numerical model was validated against experimental measurements, confirming its accuracy in capturing gas-solid flow characteristics. Systematic analyses were conducted to examine the effects of nozzle gas velocity and structural parameters on particle dynamics. Results demonstrate that the increased gas velocity effectively mitigates particle accumulation in the sudden expansion zone, promoting more uniform solid distribution within the reactor. However, gas velocity variations showed negligible impact on particle concentration profiles in upper regions. Structural optimization revealed that implementing a conical transition with specific inclination angles between the upper and lower sections of the gradual expansion zone enhanced particle distribution uniformity and gas-solid mixing efficiency. These improvements were particularly conducive to optimizing catalytic cracking processes. These findings provided theoretical guidance for reactor design aiming at enhancing fluidization quality and process performance.