JP2776146B2 - Axial fan - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial fan frequently used as a blower for an air conditioner.

[0002]

2. Description of the Related Art In general, an axial fan frequently used as a blower for an air conditioner is provided with a plurality of blades on an outer periphery of a hub serving as a center of rotation.

When the axial fan having such a configuration is rotated, as shown in FIG. 6, a boundary layer develops in the air flow F flowing on the suction surface 2a 'of the blade 2', and the separation flow E is generated. As a result, the aerodynamic performance is reduced and the driving noise is increased.

[0004] In view of the above, there has already been proposed an arrangement in which the development of the boundary layer is suppressed by forming a large number of dimples on the negative pressure surface of the blade of the axial flow fan (for example,
JP-A-60-35119).

[0005]

However, the reason for forming dimples on the negative pressure surface of the blade as in the above-mentioned known example is to suppress the development of the boundary layer by causing a secondary flow of air in the dimples. However, depending on the shape or size of the dimple, the effect may not be sufficient. The above-mentioned known example does not disclose that point.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and by appropriately defining the shape or size of dimples formed on a suction surface of a blade, the development of a boundary layer in the airflow flowing on the suction surface is improved. Is intended to be able to be effectively suppressed.

[0007]

According to the first aspect of the present invention, as shown in the drawings, a plurality of blades 2, 2 are provided on the outer periphery of a hub 1 serving as a center of rotation, as shown in the drawings.
In the axial flow fan provided with a plurality of dimples 3, 3,... Formed on the negative pressure surface 2a of each of the blades 2, the depth of the dimples 3 is set to d, and the hole diameter of the dimples 3 is set to φ. 0.15 ≦ d / φ ≦ 0.3, and R is the average radius of curvature of the blade 2 on the same circumference 0.005 ≦ φ / R ≦ 0.020 It is set to be.

[0008]

According to the first aspect of the present invention, the following effects can be obtained by the above means.

That is, the shape and size of the dimple 3 are in the optimum range (ie, 0.1
Since 5 ≦ d / φ ≦ 0.3, the development of the boundary layer on the blade negative pressure surface 2a is effectively suppressed. In the case of 0.15> d / φ, the depth d is too small as compared with the hole diameter φ of the dimple 3, so that secondary flow in the dimple 3 cannot be expected, and d / φ> 0 In the case of 0.3, the depth d is too large compared to the hole diameter φ of the dimple 3, and it is difficult to flow air into the dimple 3, so that a secondary flow cannot be expected.

In addition, the ratio of the hole diameter φ of the dimple 3 to the average radius of curvature R on the same circumference of the blade is within an optimal range (ie, the optimum range).
0.005 ≦ φ / R ≦ 0.020),
The boundary layer development on the blade negative pressure surface 2a is further suppressed. In the case of φ / R <0.005, the dimple hole diameter φ becomes too small to function as the dimple 3, and in the case of φ / R> 0.020, the dimple hole diameter φ Becomes too large, and it is difficult to generate a secondary flow in the dimple 3.

[0011]

According to the first aspect of the present invention, in the axial flow fan having a plurality of blades 2, 2,... On the outer periphery of the hub 1 serving as the center of rotation, the negative pressure surface 2a of each of the blades 2 Are formed so that 0.15 ≦ d / φ ≦ 0.3 when the depth of the dimple 3 is d and the hole diameter of the dimple 3 is φ. Therefore, the development of the boundary layer on the blade suction surface 2a can be effectively suppressed.
Separation of the flow on the a side is suppressed, and there is an excellent effect that the operating noise of the fan can be reduced and the aerodynamic performance can be improved.

Further, when the average radius of curvature of the blade 2 on the same circumference is R, the boundary layer development on the blade negative pressure surface 2a is set so that 0.005 ≦ φ / R ≦ 0.020. Because the pressure can be further suppressed, the blade negative pressure surface 2a
Separation of the flow on the side is further suppressed, and there is also an excellent effect that it is possible to further reduce the operating noise of the fan and further improve the aerodynamic performance.

[0013]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

The axial fan according to the present embodiment is frequently used as a blower for an air conditioner. As shown in FIG. 1, four blades 2,
2, 2, and 2.

The negative pressure surface 2a of each blade 2 has
A large number of dimples 3, 3,... Are formed.

The formation of the dimples 3, 3,...
As shown in FIG. 3, the air flow F on the blade negative pressure surface 2a
As a result, a secondary flow is generated in each dimple 3, the boundary layer development is effectively suppressed, and the generation of the separation flow E is also largely suppressed.

With the depth of the dimple 3 as d, the hole diameter of the dimple 3 as φ, and the average radius of curvature of the blade 2 on the same circumference as R, the noise reduction effect S / d and φ / R are defined as S. When the change was examined, the results shown in FIGS. 4 and 5 were obtained. Here, the average radius of curvature R on the same circumference refers to the blade of the camber line (that is, the warpage line) C of the blade cross section in the curve A (see FIG. 1) in which the distance r from the center axis of the axial fan is constant. It is the average value of the radius of curvature from the leading edge to the trailing edge of the blade (see FIG. 3).

According to this, the sound reduction effect S is 0.15 ≦
d / φ ≦ 0.3 and 0.005 ≦ φ / R ≦ 0.020
The maximum value is shown in the range.

Therefore, the dimples 3, 3... Formed on the blade negative pressure surface 2a of the axial fan are such that 0.15 ≦ d / φ ≦ 0.3 0.005 ≦ φ / R ≦ 0.020. It is desirable to be set to.

In the case of 0.15> d / φ, the depth d is too small as compared with the hole diameter φ of the dimple 3, and
The secondary flow at dimple 3 cannot be expected and d / φ
In the case of> 0.30, the depth d is too large compared to the hole diameter φ of the dimple 3, and it becomes difficult to flow air into the dimple 3, so that a secondary flow cannot be expected. Also, φ
When /R<0.005, the dimple hole diameter φ becomes too small to function as the dimple 3, and when φ / R> 0.020, the dimple hole diameter φ becomes large. This makes it difficult to generate a secondary flow in the dimple 3.

In this embodiment, since the radius of curvature R of each blade 2 increases toward the outside in the radial direction, the hole diameter φ of the dimple 3, 3,... Also increases toward the outside in the radial direction. Have been.

The present invention is not limited to the configuration of the above-described embodiment, and it is needless to say that the design can be changed as appropriate without departing from the gist of the invention.

[Brief description of the drawings]

FIG. 1 is a front view of an axial fan according to an embodiment of the present invention as viewed from a negative pressure side.

FIG. 2 is a partially enlarged sectional view of a blade of the axial fan according to the embodiment of the present invention.

FIG. 3 is an enlarged sectional view taken along the line III-III of FIG. 1;

FIG. 4 shows an axial fan according to an embodiment of the present invention.
FIG. 9 is a characteristic diagram showing a change in a sound reduction effect with respect to d / φ.

FIG. 5 is a characteristic diagram showing a change in a noise reduction effect with respect to φ / R in the axial fan according to the embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 3 of a conventional axial fan.

[Explanation of symbols]

 1 is a hub, 2 is a blade, 2a is a suction surface, and 3 is a dimple.

Claims (1)

(57) [Claims] 1. An axial flow fan comprising a plurality of blades (2) on the outer periphery of a hub (1) serving as a center of rotation, wherein a negative pressure surface of each blade (2) is provided. 2a), a large number of dimples (3), (3),.
When the depth of (3) is d and the hole diameter of the dimple (3) is φ, it is set so that 0.15 ≦ d / φ ≦ 0.3, and on the same circumference of the blade (2). Wherein the average radius of curvature of R is 0.005 ≦ φ / R ≦ 0.020.