Patent ID: 9206813
Filing Date: 2015-12-08
Classification: F04D

Abstract:
1. A centrifugal fan, comprising: an impeller having a hub and a plurality of blades; and a casing comprising: an upper casing; a lower casing disposed opposite to the upper casing and connected to the upper casing to form an accommodation room for receiving the impeller; a plurality of protrusions all disposed on the upper casing or the lower casing inside the casing and immediately surrounding the blades; and a first inlet opening defined on the upper casing and comprising a primary inlet opening augmented by a secondary inlet opening; a second inlet opening defined on the lower casing; wherein the primary inlet opening is circular and centered on a rotation axis of the impeller and the protrusion surrounds the first inlet opening or the second inlet opening, wherein a gap exists between the blades and the upper casing or the lower casing, wherein a height of the protrusion is greater than a quarter of a height of the gap, and the height of the protrusion is less than the height of the gap.