JPH09228995A - Axial fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength of blades themselves and suppress the peeling of an air stream so as to improve aerodynamic characteristic and noise characteristics by specifying an installation position of a rib for suppressing peeling of air stream in an axial fan in which a plurality of blades are provided around the center of rotation and the rib for suppressing peeling of air stream on a surface of the blade on a negative pressure side. SOLUTION: In an axial fan constituted by arranging a plurality of blades 1 around the center 3 of rotation, a rib 2 for suppressing peeling of air stream is provided at a position l of 0 to 10% of chord length L from a front fringe 1a in the direction of rotation and at a position of 25 to 75% of blade length r on a surface on a negative pressure side of the blade 1, and the blade 1 is reinforced by the rib 2 without increasing its wall thickness. Moreover, the rib 2 is formed in column shape, and its thickness is 1.0 to 1.5 times the thickness t of the blade. Consequently, since eddy current along face which adheres on the surface on the negative pressure side of the blade 1 is generated in more a region on the back side in the direction of rotation than the rib 2 due to the rotation of the blade 1, air stream F is not peeled easily, and aerodynamic characteristics and noise characteristics of the axial fan can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial fan used for an air conditioner, a ventilation fan and the like.

[0002]

2. Description of the Related Art In an axial fan having a plurality of blades arranged around a rotation center, it is effective to increase the thickness of the entire blades uniformly in order to improve the strength of the blades themselves. FIG. 4 is a view showing the end face of the blade 1 whose overall thickness is increased uniformly. In FIG. 4, a broken line a is a contour portion showing the negative pressure side surface of the thin blade.

On the other hand, in JP-A-2-119699 and Japanese Utility Model Laid-Open No. 5-69400, a blade having a predetermined shape is provided at a predetermined position on the negative pressure side surface of the blade so that the blade itself does not increase in thickness. It is described that, in addition to improving the strength of the blade, air flow separation on the negative pressure side surface of the blade is further suppressed to improve aerodynamic characteristics and noise characteristics.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
If the wall thickness is increased to improve the strength, the weight of the blade increases and the material cost also increases. Further, as shown in FIG. 5, since the contour shape of the negative pressure side surface of the blade 1 itself is the same as that of the thin-walled case, the state of air flow separation during rotation is almost the same as that of the thin-walled case. . In FIG.
A is the rotation direction, F is the air flow, and F1 is the eddy current generation region.

Further, in the case of improving the strength by providing ribs on the blade, according to the above-mentioned Japanese Patent Laid-Open No. 2-119699, at the position of 0 to 5% of the chord length from the front edge in the rotational direction on the negative pressure side surface of the blade. It is described that air flow separation is suppressed when a rib having a circular shape in cross section whose radius of curvature is set to 1 to 5% of the chord length is provided. Further, according to Japanese Utility Model Laid-Open No. 5-69400, as shown in FIGS. 6 and 7, the curvature at the position 1 of 10% to 20% of the chord length L from the front edge 1a in the rotational direction on the negative pressure side surface of the blade 1. It is described that airflow separation is suppressed when the rib 2 having a semicircular cross-sectional shape in which the radius R is set to 1.5 to 3 times the blade thickness t is provided. 6 is a front view of the axial fan according to the publication, and FIG. 7 is an end view of the blade shown in FIG. 6 taken along the cutting line in the circumferential direction. In FIG. 6, A indicates the rotation direction.

However, the above-mentioned actual Kaihei 5-69400
In the axial flow fan of the publication, since the ribs 2 are provided in a strip shape over the entire blade length, the noise characteristic of the entire blade 1 is deteriorated.

More specifically, the airflow near the center of the blade 1 is likely to generate vortices, and most of the airflow near the outer periphery of the blade 1 flows to the outside of the blade 1. In addition, even if the ribs 2 are provided at these portions, an effective air flow separation suppressing action cannot be obtained, and conversely, the generation of vortices and the large amount of air flow flowing outside deteriorate the noise characteristics of the entire blade 1. Was there.

In view of the above problems, the present invention is basically designed to improve the strength of the blade itself by providing a rib on the blade, and the airflow separation is suppressed by devising the location of the rib and the shape of the rib. However, it is an object of the present invention to provide an axial fan that can improve aerodynamic characteristics and noise characteristics.

[0009]

In the axial fan according to claim 1 of the present invention, a plurality of blades are provided around the center of rotation, and air flow separation suppressing ribs are provided on the negative pressure side surface of the blade. In the axial flow fan configured as described above, the air flow separation suppressing rib is provided with a blade length of 25 to 7 on the negative pressure side surface of the blade.
It is characterized in that it is provided at a position of 5%.

The axial fan according to a second aspect of the present invention is characterized in that the air flow separation suppressing rib is provided at a position less than 10% of the chord length from the front edge with respect to the rotation direction of the blade. It is a thing.

Further, in the axial fan according to a third aspect of the present invention, the air flow separation suppressing rib is formed of a columnar shape, and the thickness thereof is set to 1.0 to 1.5 times the blade thickness. It is characterized by.

According to the above structure, in the axial fan according to the first aspect of the present invention, the air flow separation suppressing rib is provided at a position of 25 to 75% of the blade length on the negative pressure side surface of the blade. The airflow separation suppressing ribs increase the strength of the blades, and creeping overflow generated behind the airflow separation suppressing ribs during rotation easily adheres to the negative pressure side surface of the blades, so that airflow separation hardly occurs. Moreover, since the air flow separation suppressing rib is provided at a position of 25 to 75% of the blade length, it is possible to prevent eddies from being generated at a position of less than 25% of the blade length, and at the same time, 75% of the blade length. It is possible to prevent an increase in the amount of airflow flowing outside at a position that exceeds.

Further, in the axial fan according to the second aspect of the present invention, the air flow separation suppressing rib is provided at a position less than 10% of the chord length from the front edge with respect to the rotating direction of the blade, so that the air flow separation suppressing function is suppressed. The effect can be remarkably obtained.

Further, in the axial flow fan according to a third aspect of the present invention, the air flow separation suppressing ribs are columnar, and the thickness thereof is set to 1.0 to 1.5 times the blade thickness. Further, the effect of suppressing air flow separation can be remarkably obtained, and the blade provided with the rib for suppressing air flow separation can be easily manufactured.

[0015]

1 is a front view of an axial flow fan according to an embodiment of the present invention, and FIG. 2 is an end view of the axial flow fan taken along the cutting line in the circumferential direction, Figure 1
The arrow A indicates the direction of rotation.

In an axial flow fan in which a plurality of blades 1 are arranged around the center of rotation 3, the blade 1 is formed on the negative pressure side surface of the blade 1 along the front edge 1a in the rotation direction of the blade 1.
0 to 10% of the chord length L of the blade 1 from the front edge 1a in the rotation direction of
At a position 1 of (0L to 0.1L) and a blade length r of 25 to
Airflow separation suppressing ribs (hereinafter, simply referred to as “ribs”) 2 are provided at 75% (0.25r to 0.75r) positions, and the ribs 1 thicken the blades 1. It is reinforced without.

The reason why the position of the rib 2 is limited to the position 10% of the chord length L of the blade 1 from the front edge 1a in the rotational direction of the blade 1 is that the position 1 of the rib 2 is in front of the blade 1 in the rotational direction. This is because when the length exceeds 10% of the chord length L of the blade 1 from the edge 1a, the airflow separation suppressing effect is reduced, and the airflow separation suppressing effect cannot be remarkably obtained.

According to Japanese Utility Model Laid-Open No. 5-69400, when the position 1 of the rib 2 is smaller than 10% of the chord length L of the blade 1, the rib 2 is too close to the front edge 1a to produce the blade 1. Although it is described that there is a technical difficulty in doing so, it is because the above-mentioned position is almost the same as the conventional technique for manufacturing the blade 1, and the problem as described in the publication does not occur. is there.

Further, the position where the rib 2 is provided is set to 2 of the blade length r.
The reason for limiting the position to 5 to 75% is that the airflow passing therethrough has the greatest effect on the aerodynamic characteristics and noise characteristics, and suppressing airflow separation in this part is most effective in improving the aerodynamic characteristics and noise characteristics. It is due to.
In addition, vortices are likely to occur at positions less than 25% of the blade length,
At a position exceeding 75% of the blade length, a large amount of airflow will flow to the outside, and even if ribs are provided in these parts, it will be 25% to 75%.
This is because the effect of suppressing the separation of the airflow as in the area of No. 1 cannot be obtained, and conversely, the generation of vortices and the increase in the amount of airflow flowing outside deteriorate the noise characteristics of the entire blade.

The rib 2 will be specifically described.
Formed in a columnar shape by chamfering the corners of the side surface of the rectangular parallelepiped,
The upper surface of the rib 2 and the negative pressure side surface of the blade 1 are set parallel to each other. The thickness is 1.0 to 1.5 of the blade thickness t.
It is set to double (1.0t to 1.5t).

Here, the reason why the rib 2 has a columnar shape is that if the corners of the upper surface are chamfered into a semicircular shape,
The separation of the air flow is the same as when the rib 2 is not provided,
This is because the effect of suppressing air flow separation is weakened.

Further, the reason why the thickness of the rib is limited to the above range is that when the thickness of the rib 2 is smaller than the blade thickness t of 1.0, the step between the height of the rib 2 and the negative pressure side surface of the blade 1 is increased. This is because the effect of suppressing air flow separation is small, and if it exceeds 1.5 times, the level difference between the height of the rib 2 and the surface of the blade 1 on the negative pressure side is too large to improve the effect of air flow separation. This is because it is difficult to manufacture the blade 1 provided with the ribs 2 because only the portion provided with 2 becomes too thick.

As described above, when each is set in the above range and shape, as the blade 1 rotates, as shown in FIG. 3, it is indicated by the symbol F1 on the rear side of the rib 2 in the rotational direction. A creeping vortex attached to the negative pressure side surface of the blade 1 is generated in the region, and as a result, separation of the airflow F is less likely to occur, and aerodynamic characteristics and noise characteristics of the axial fan can be improved. FIG. 3 is a diagram showing an air flow state at the end surface of the blade 1 when the axial fan according to the present embodiment is rotating.

As described above, in the axial fan according to the present embodiment, the rib 2 is provided at the position of 25 to 75% of the blade length on the negative pressure side surface of the blade 1. The strength of the rib can be increased, and the rib 2 can be rotated.
The creeping turbulence that occurs in the rear of the blade easily adheres to the negative pressure side surface of the blade 1, so that air flow separation does not easily occur, and aerodynamic characteristics and noise characteristics are improved. Moreover, since the ribs 2 are provided at the positions of 25 to 75% of the blade length, it is possible to prevent the generation of vortices at the positions of less than 25% of the blade length, and at the positions exceeding 75% of the blade length. Therefore, it is possible to prevent the air flow flowing outside from increasing. Therefore, it is possible to prevent the generation of noise caused by the generation of vortices and the increase of the airflow flowing outside, and it is possible to further improve the noise characteristics.

Further, since the rib 2 is provided at a position which is less than 10% of the chord length from the front edge 1a with respect to the rotation direction of the blade 1, the air flow separation suppressing effect can be remarkably obtained.

Further, since the ribs 2 are columnar and the thickness thereof is set to 1.0 to 1.5 times the blade thickness, the air flow separation suppressing effect can be remarkably obtained and the ribs 2 can be obtained. The blade 1 provided with can be easily manufactured. Further, since the rib 2 is formed in a columnar shape, it is possible to obtain an effective air flow separation suppressing action even at a high rotation speed.

[0027]

According to the above construction, in the axial fan according to claim 1 of the present invention, the air flow separation suppressing rib is provided at a position of 25 to 75% of the blade length on the negative pressure side surface of the blade. Therefore, the strength of the blade can be increased by the airflow separation suppressing rib, and the creeping overflow generated behind the airflow separation suppressing rib during rotation easily adheres to the negative pressure side surface of the blade,
Therefore, air flow separation is less likely to occur. Moreover, since the airflow separation suppressing ribs are provided at the positions of 25 to 75% of the blade length, it is possible to prevent the generation of vortices at the positions of less than 25% of the blade length, and 75% of the blade length. It is possible to prevent an increase in the airflow flowing outside at the position where it exceeds.
Therefore, it is possible to prevent the generation of noise caused by the generation of vortices and the increase of the airflow flowing outside, and further improve the noise characteristics.

Further, in the axial fan according to the second aspect of the present invention, the air flow separation suppressing rib is provided at a position less than 10% of the chord length from the front edge with respect to the rotating direction of the blade, so that the air flow separation suppressing function is suppressed. The effect can be remarkably obtained.

Further, in the axial flow fan according to the third aspect of the present invention, the air flow separation suppressing ribs are columnar and the thickness thereof is set to 1.0 to 1.5 times the blade thickness. Further, the effect of suppressing air flow separation can be remarkably obtained, and the blade provided with the rib for suppressing air flow separation can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a front view of an axial fan according to an embodiment of the present invention.

FIG. 2 is an end view taken along a cutting line in a circumferential direction of blades in the axial fan shown in FIG.

FIG. 3 is a diagram illustrating the operation of the axial fan shown in FIG.

FIG. 4 is an end view taken along a circumferential cutting line of a blade in a conventional axial flow fan.

FIG. 5 is an operation explanatory view of an axial fan according to a conventional example.

FIG. 6 is a front view of another conventional axial flow fan.

FIG. 7 is an end view of the blade shown in FIG. 6 taken along a cutting line in a circumferential direction.

[Explanation of symbols]

 1 Blade 1a Rotation direction front edge 2 Rib 3 Rotation center L Chord length r Blade length t Blade thickness

Claims (3)

[Claims] 1. An axial flow fan comprising a plurality of blades arranged around a center of rotation, wherein airflow separation suppressing ribs are provided on a negative pressure side surface of said blades. An axial fan provided at a position of 25 to 75% of the blade length on the negative pressure side surface of the. 2. The axial fan according to claim 1, wherein the air flow separation suppressing rib is provided at a position less than 10% of a chord length from a front edge with respect to a rotation direction of the blade. 3. The axial flow according to claim 1 or 2, wherein the air flow separation suppressing rib has a columnar shape and the thickness thereof is set to 1.0 to 1.5 times the blade thickness. fan.