JP2003278696A - Propeller fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce separation of flow on a blade surface without greatly increasing production cost for improving performance and lowering noise of a propeller fan. <P>SOLUTION: In this propeller fan having a plurality of blades 2 in the outer circumference of a hub 1, a serrate small wing 4 is arranged as a boundary layer controlling means preventing separation of the flow in the front edge in the rotation direction of each blade, and a triangular pyramid projection part 5 swelling on the face (negative pressure face side) of the small wing is formed. In this way, a vertical swirl produced from the tip of the small wing is spread over the blade surface to reduce thickness of the boundary layer of the blade surface (negative pressure face) when the fan is operated. Consequently, an influence due to fluctuation of main flow entering to the fan and an influence of separation of the laminar flow boundary layer on the blade surface are effectively reduced, and pressure resistance and noise can be reduced. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a propeller fan applied to a blower fan such as an air conditioner, and more particularly to a blade structure.

[0002]

2. Description of the Related Art The propeller fan described above is required to have a low noise level in order to improve the fan performance and to maintain quietness. Next, FIGS. 2 and 3 show examples of measures for preventing flow separation and reducing noise, which are adopted in a conventional propeller fan. In the figure, 1 is a hub connected to a drive motor (not shown), and 2 is a blade (three blades) protruding from the outer periphery of the hub 1.

First, in the propeller fan illustrated in FIG. 2, the blade 2 has a chord length increasing from the root portion on the hub side toward the outer peripheral portion, and the tip 2a of the outer peripheral portion is sharpened in the rotational direction A. It has a shape. Due to this blade shape, a longitudinal vortex generated at the sharp front edge of the outer peripheral end 2a of the blade 2 during operation of the fan causes the vortex surface of the blade 2 (negative pressure surface).
It is considered that the noise of the fan is reduced by suppressing the separation of the surface laminar boundary layer in the blade and suppressing the concentration of the vorticity of the tip vortex generated at the blade tip.

Further, in the example of FIG. 3, fin-shaped projections (or grooves) are formed on the entire blade surface (negative pressure surface side) of the blade 2.
3 are dispersedly formed, and the fin-shaped projections (or grooves) 3 disturb the flow to promote the turbulent transition, and the mixing action of the turbulent flow forms a turbulent boundary layer on the blade surface to prevent separation. I try to prevent it. In addition, JP-A-8-17
As disclosed in Japanese Patent No. 7792, a triangular pyramid-shaped convex guide or depression is provided on the trailing edge side with respect to the rotation direction A of the blade, and a large vortex (separation point) due to separation of the flow generated on the blade surface (negative pressure surface). There is also known a low noise countermeasure in which a backflow is generated on the downstream side to generate a large vortex, which causes noise (air vibration) to be small) to reduce the noise.

[0005]

The propeller fan having the above-mentioned conventional structure has the following problems.
That is, in the blade shape of the propeller fan shown in FIG. 2, the range in which the vertical vortex generated from the sharp tip of the blade spreads is limited to the outer peripheral portion of the blade, and especially in an environment where a static pressure increase of the fan is required, Separation of the flow easily occurs in the root side region of the blade that is separated in the direction, and it is difficult to secure the separation preventing function on the entire blade surface.

In the configuration shown in FIG. 3, the separation prevention and the low noise function cannot be sufficiently ensured in an environment where the flow of air flowing into the fan fluctuates greatly, and the fan is manufactured to form fin-shaped projections or grooves. Expense becomes high cost. The present invention has been made in view of the above points, and effectively suppresses the separation on the blade blade surface without significantly increasing the manufacturing cost and even in an environment where the fluctuation of the flow flowing into the fan is large. It is an object of the present invention to provide an improved propeller fan capable of improving fan performance and reducing noise.

[0007]

In order to achieve the above object, according to the present invention, in a propeller fan having a plurality of blades on the outer circumference of a hub, the flow of the flow at the front edge of each blade in the rotation direction is reduced. As a boundary layer control means for preventing peeling, a serrated small wing in which a triangular pyramid-shaped convex portion is raised is provided on the suction surface side (claim 1). Specifically, it is configured in the following manner. .

(1) The blade is made of resin, and the small wings and triangular pyramid-shaped projections are integrally formed with the blade (claim 2). (2) The blade is made of a steel plate, and triangular pyramid-shaped convex portions are formed by pressing on the plate surface of the small wing (claim 3). As described above, by providing the front edge of the blade with a sawtooth-shaped small wing protruding in the direction of rotation and a triangular pyramid-shaped convex portion protruding on the surface of the small wing (on the suction side), At the same time that the small wings with convex parts function as a vortex generator, the vertical vortices generated from the tips of the small wings during fan operation spread over the blade surface along the sides of the triangular pyramidal convex parts. As a result, the influence of the fluctuation of the main flow and the influence of the separation of the laminar boundary layer on the blade surface are avoided, and the pressure resistance and noise due to the flow separation are reduced. Moreover, by providing triangular pyramid-shaped protrusions on the blade surface of the small wing, the strength and size of the vertical vortex generated from the tip of the small wing are promoted, and the collapse of the vertical vortex on the blade surface is delayed. Therefore, a stable laminar boundary layer separation prevention function can be secured even in an environment where the flow flowing into the fan fluctuates greatly.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
Description will be made based on the embodiments shown in (a) and (b). In the illustrated embodiment, as the boundary layer control means for the blades 2, small saw-like wings 4 protruding in the rotational direction along the front edge of each blade 2 are dispersedly formed, and on the blade surface of the small wings 4. The triangular pyramidal convex portion 5 is formed on the negative pressure surface side.

When the blade 2 is made of resin, the small wing 4 and the convex portion 5 are formed integrally with the blade 2. Further, when the blade 2 is made of a steel plate, the convex portion 5 is formed from the back side of the small wing 4 by pressing.
Are extruded. With the above configuration, when the fan is in operation, the small sawtooth wing 4 formed on the front edge of the blade 2 functions as a vortex generator, and at the same time, the vertical vortex generated from its sharp tip uses the triangular pyramid-shaped convex portion 5 as a guide. It is possible to reduce the thickness of the boundary layer of the blade blade surface (negative pressure surface) by spreading it downstream and creating a downward secondary flow on the blade surface. As a result, it is possible to effectively avoid the influence of the fluctuation of the main flow flowing into the fan and the influence of the separation of the laminar boundary layer on the blade surface.

In this case, by combining the sawtooth-shaped small wings 5 with the triangular pyramid-shaped convex portions 5 as in the illustrated example, a vertical vortex generated from the sharp tip of the small wings 4 is generated more stably,
It can be dispersed and exhibits a stable peeling prevention function even in an environment where the flow flowing into the fan fluctuates greatly. Moreover, since the small wings 4 and the triangular pyramid-shaped convex portions 5 only have to be provided on the front edge of the blade 2 and can be easily formed by resin molding and press working as described above, the manufacturing cost is not significantly increased. .

[0012]

As described above, according to the configuration of the present invention, in the propeller fan having a plurality of blades on the outer circumference of the hub, the front edge of each blade in the rotation direction is
As a boundary layer control means to prevent flow separation, a saw tooth-shaped small wing with raised triangular pyramid-shaped protrusions is provided on the suction side to improve fan performance and reduce noise with a simple configuration. In particular, as a blower fan for an air conditioner, it exerts an excellent effect in improving quietness.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a propeller fan according to an embodiment of the present invention, (a) is a front view of the entire fan, and (b) is an enlarged perspective view of a small wing portion in (a).

FIG. 2 is a front view of a propeller fan showing a blade shape of a conventional example.

FIG. 3 is a front view of a conventional propeller fan in which a convex portion (or groove) is formed on a blade surface of a blade.

[Explanation of symbols]

1 hub Two blades 4 small serrated wings 5 Triangular pyramidal protrusion

Claims (3)

[Claims] 1. A propeller fan having a plurality of blades on the outer circumference of a hub, wherein a triangular pyramid-shaped projection is formed on the suction surface side as a boundary layer control means for preventing flow separation at the leading edge of each blade in the rotational direction. A propeller fan characterized by having a serrated small wing with raised parts. 2. The propeller fan according to claim 1, wherein
A propeller fan characterized in that the blade is made of resin, and a small wing and a triangular pyramid-shaped convex portion are formed integrally with the blade. 3. The propeller fan according to claim 1, wherein
A propeller fan in which a blade is made of a steel plate and a triangular pyramid-shaped convex portion is press-formed on a plate surface of a small wing.