Abstract: Due to its unique circulation characteristics and high mass transfer efficiency, the loop reactor has shown great application potential in the fields of bioengineering, environmental engineering, and chemical engineering. The research on it focuses on macroscopic fluid dynamic behavior, and the study of bubble diameter distribution has proven significance for the design optimization and scale-up of reactors. This paper utilizes computational fluid dynamics (CFD) and population balance model (PBM) to deeply investigate the bubble diameter distribution inside a staged multistage internal airlift loop reactor. The research found that there is a significant difference in gas holdup between the rising and falling zones; the gas holdup in each stage of the rising zone shows different changing trends along the axis; for the falling zone, the gas holdup increases along the axial height. Large bubbles (with a diameter of 11.56 - 14.98 mm) in the reactor are mainly concentrated in the rising zones of the second and third stages, while smaller bubbles with a diameter of 0.67 - 1.13 mm mainly exist at the bottom of the falling zones of the first and third stages.

Key words: font-family:-apple-system, blinkmacsystemfont, ", font-size:14px, background-color:#FFFFFF, ">staggered, multistage, internal airlift loop reactor, bubble distribution, gas holdup, bubble diameter, computational fluid dynamics, population balance model

摘要： 环流反应器因其独特的循环特性和高效的传质效率，在生物工程、环境工程和化学工程等领域具有巨大的应用潜力。由于对其的研究聚焦于宏观流体力学行为上，针对气泡直径分布的研究对于反应器的设计优化与规模化放大具有深远意义。借助计算流体力学（CFD）与群体平衡模型（PBM），深入探究交错多级内环流反应器内气泡直径分布。研究发现：上升区和下降区存在明显的气含率差异；各级上升区气含率沿轴向表现出不同变化趋势；对于下降区，气含率沿着轴向高度的增加而增加；反应器内大气泡（直径11.56～14.98mm）主要集中在第二级和第三级上升区，较小尺寸的气泡（直径0.67～1.13mm）主要存在于第一级和第三级下降区的底部。

关键词: font-family:-apple-system, blinkmacsystemfont, ", font-size:14px, background-color:#FFFFFF, ">交错, 多级, 内环流反应器, 气泡分布, 气含率, 气泡直径, 流体动力学, 群体平衡模型