CENTRIFUGAL FAN AND METHOD OF REDUCING NOISE OF CENTRIFUGAL FAN

摘要

A centrifugal fan is, within an outer shell, provided with an electric motor to which an impeller is connected, a casing for surrounding the impeller and having formed in one face thereof a bell-mouth-shaped suction opening, a bell-mouth-shaped orifice concentric with the suction opening and provided with a suction opening having a diameter equivalent to that of the suction opening, projections arranged in a resonance space surrounded by the orifice, the casing, and the outer shell, and recesses formed between the projections. The construction reduces noise of a wide frequency range produced by the centrifugal fan.