Counter-rotating axial flow fan

摘要

A counter-rotating axial flow fan (1) in which the shape of stationary blades (17) of a middle stationary portion (19) is optimized to reduce noise is provided. Defining the maximum axial chord length of front blades (11) as Lf, the maximum axial chord length of rear blades (23) as Lr, and the maximum axial chord length of stationary blades (17) as Lm, a relationship of Lm/(Lf + Lr) < 0.14 is satisfied. Defining the maximum dimension between the blade chord (C) for lower surfaces (17B) of the stationary blades (17) and the lower surfaces (17B) as K1, the maximum axial chord length Lm of the stationary blades (17) satisfies a relationship of Lm/K1 > 5.8.