Daikin Industries, Ltd.

Suguru Nakagawa

Zhiming Zheng

Jirou Yamamoto

A propeller fan includes a huband a plurality of blades, which are radially arranged on the outer circumference of the hub. A plurality of bent surface-shaped recessestoare formed on the positive pressure surface at a trailing edgeof each blade. The recessestoextend in the rotation direction of the fan and are arranged in a radial direction. Protrusionsare each formed between adjacent pair of the recessesto. The bent surfaces of the recessestoand the protrusionsreduces air flow caused by centrifugal force. This allows the air flow on the positive pressure surface of the bladeto easily flow along the recessesto. As a result, air flow does not concentrate on the outer periphery of the blade, which reduces the differences in the velocity and volume of air flow between the outer tipof the bladeand the hub. Accordingly, the bladefunctions as a whole. Therefore, the air blowing performance (efficiency and air blowing noise) of the propeller fan is improved.

Propeller fan

A propeller fan has a gap between a bellmouth and each blade tip. A leakage flow is thus produced from a positive pressure surface of a blade toward a negative pressure surface of the blade via the gap. The leakage flow develops while flowing from the leading edge of each blade toward the trailing edge, thus forming a blade tip vortex. This increases blowing noise and raises the input of the fan motor. In order to suppress the blade tip vortex caused by the leakage flow, the present invention includes recessed portions and projected portions, which are alternately formed in a portion of a blade surface of each blade corresponding to the blade tip.

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Sakai, Japan

Suguru Nakagawa