聚风型风筒的聚风效率与装置尺寸密切相关。本文基于数值仿真方法，结合实验验证，对不同尺寸的聚风装置的速度分布、压力分布等流场特性进行了研究，表明聚风装置的尺寸在低于某临界值时，聚风效率会随着装置尺寸的减小急剧下降；而高于该值时聚风效率变化缓慢。 The efficiency of the converging duct is closely related to the size. In the paper, the numerical si-mulation is implemented to study the performance of the converging duct, combining with the experiment test. The flow characteristic, such as the velocity distribution and the pressure distri-bution, are investigated respectively. The results present that there is a critical size for the con-verging duct. When the duct size is lower than the critical size, the size effect is obvious, and the efficiency of the converging effect will decrease as the duct size decreases. When the duct size is higher than the critical size, the change of the converging efficiency slows down.