CN112739913A - Centrifugal fan - Google Patents

Abstract

A centrifugal fan (1) is provided with: an annular side plate (2), the side plate (2) having an air intake (5); the main plate (3), the main plate (3) and the side plate (2) are arranged oppositely; and a plurality of blades (4), wherein the plurality of blades (4) are arranged at a predetermined interval in the rotation direction between the side plate (2) and the main plate (3). The blade (4) has a through hole (10) that penetrates the negative pressure surface (8) and the positive pressure surface (9) and does not open to the trailing edge (7).

Description

Centrifugal fan

Cross reference to related applications

The present application is based on japanese patent application No. 2018-212396, filed on 12/11/2018, the contents of which are incorporated herein by reference.

Technical Field

The present invention relates to a centrifugal fan for a centrifugal blower.

Background

Conventionally, a centrifugal fan for a centrifugal blower is known.

The centrifugal fan described in patent document 1 has a plurality of concave-convex shapes (hereinafter, referred to as "serrations") at the trailing edge of the blade. This centrifugal fan reduces the difference in pressure between the boundary between the air blown out from the positive pressure surface side of the trailing edge of the blade and the air blown out from the negative pressure surface side of the trailing edge of the blade at the outlet of the flow path formed between the blades (hereinafter referred to as an inter-blade flow path), thereby reducing noise.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 4432474

However, the centrifugal fan described in patent document 1 reduces the area for performing work for blowing air in the vicinity of the trailing edge of the blade by providing the serrations on the trailing edge of the blade. Therefore, there is a problem that the air blowing efficiency of the centrifugal fan is reduced. The air blowing efficiency is the amount of air blown by the fan with respect to the energy required for the rotation of the fan.

Disclosure of Invention

The invention aims to provide a centrifugal fan which can reduce noise, restrain the reduction of air supply efficiency along with the reduction of the area of a blade, or improve the air supply efficiency.

In accordance with one aspect of the present invention,

a centrifugal fan for a centrifugal blower is provided with:

an annular side plate having an air suction port;

the main plate is arranged opposite to the side plate; and

a plurality of blades arranged at a predetermined interval in a rotation direction between the side plate and the main plate,

the blade has a through hole that penetrates the negative pressure surface and the positive pressure surface and does not open at the trailing edge.

Thus, in the predetermined inter-blade flow path formed between the blades, the air flowing in the vicinity of the positive pressure surface flows through the through hole to another inter-blade flow path located on the rear side in the rotation direction than the predetermined inter-blade flow path. Therefore, in the other inter-blade flow paths, the air flow having a high flow velocity flowing in the vicinity of the negative pressure surface is pushed out to the rear side in the rotational direction by the air flowing in from the through hole, and is diffused to the positive pressure surface side having a low flow velocity, so that the flow velocity variation at the outlet of the inter-blade flow path is made nearly uniform. Therefore, since the vortex formed in the vicinity of the trailing edge of the blade becomes small, noise can be reduced. The flow rate deviation refers to non-uniformity of the flow rate at the outlet of the inter-blade flow path.

However, if the area of the blade is reduced by the through hole, the air blowing efficiency may be reduced. In contrast, in an aspect of the present invention, since the through hole is not open at the trailing edge, work for pushing air out to the outside of the outlet of the inter-blade flow path can be performed by the wall surface between the through hole and the trailing edge in the blade. Therefore, the centrifugal fan has the wall surface between the through hole and the trailing edge of the blade, and thus the reduction of the air blowing efficiency due to the reduction of the area of the blade by the through hole can be suppressed, or the air blowing efficiency can be improved.

In addition, the parenthesized reference numerals attached to the respective components and the like indicate examples of the correspondence between the components and the like and the specific components and the like described in the embodiments described later.

Drawings

Fig. 1 is a perspective view of a centrifugal fan according to a first embodiment.

Fig. 2 is a side view showing a part of the centrifugal fan according to the first embodiment.

Fig. 3 is an explanatory diagram for explaining a hole width of the blade in a cross section perpendicular to the rotation axis of the centrifugal fan.

Fig. 4 is a side view showing a part of a centrifugal fan according to a second embodiment.

Fig. 5 is a side view showing a part of a centrifugal fan according to a third embodiment.

Fig. 6 is a side view showing a part of a centrifugal fan according to a fourth embodiment.

Fig. 7 is a side view showing a part of a centrifugal fan according to a fifth embodiment.

Fig. 8 is a side view showing a part of a centrifugal fan according to a sixth embodiment.

Fig. 9 is a side view showing a part of a centrifugal fan according to a seventh embodiment.

FIG. 10 is a cross-sectional view near the trailing edge of the blade at line X-X of FIG. 9.

Fig. 11 is an explanatory diagram for explaining the vortex sound theory of Powell.

Fig. 12 is an analysis diagram showing a flow velocity distribution of an inter-blade flow path in a case where serrations are provided at the trailing edge of a blade as a comparative example.

Fig. 13 is a schematic view of a case where serrations are provided at the trailing edge of the blade as a first comparative example.

Fig. 14 is a schematic view of a case where serrations are provided at the trailing edge of a blade as a second comparative example.

Fig. 15 is a schematic view of a case where serrations are provided at the trailing edge of a blade as a third comparative example.

Fig. 16 is a schematic view of a case where serrations are provided at the trailing edge of a blade as a fourth comparative example.

Fig. 17 is a schematic diagram showing an example of the shape of the through-hole.

Fig. 18 is a schematic view showing another example of the shape of the through-hole.

Fig. 19 is a schematic diagram showing another example of the shape of the through-hole.

Fig. 20 is a perspective view of the centrifugal fan showing an outlet of the inter-blade flow path.

Fig. 21 is an analysis diagram showing a flow velocity distribution in the case where the vanes are provided with serrations at the outlet of the inter-vane flow path shown in fig. 20.

Fig. 22 is an analysis diagram showing a flow velocity distribution in the case where the through-holes are provided in the vanes at the outlet of the inter-vane flow path shown in fig. 20.

Fig. 23 is a graph showing flow rate variations in the outlet of the flow path between vanes shown in fig. 20, in the case where the upper portion, the middle portion, and the lower portion of the vane have basic shapes, in the case where the vane is provided with serrations, and in the case where the vane is provided with through holes.

Fig. 24 is a graph showing flow rate variations in the case where the upper portion, the middle portion, and the lower portion of the vane have basic shapes and the hole diameters of the through holes are changed in the outlet of the inter-vane flow path shown in fig. 20.

Fig. 25 is a graph showing flow rate variations in the case where the upper portion, the middle portion, and the lower portion of the blade have basic shapes and the positions of the through holes are changed in the radial direction of the centrifugal fan in the outlet of the inter-blade flow path shown in fig. 20.

Fig. 26 is a graph showing the specific noise and the fan efficiency in the case of the basic shape, the case of the blade provided with the serrations, the case of the through hole of the first embodiment, and the case of the through hole of the second embodiment.

Fig. 27 is an analysis diagram showing a total pressure distribution of air flowing on the positive pressure surface of the vane in the case of the basic shape.

Fig. 28 is an analysis diagram showing the total pressure distribution of air flowing on the positive pressure surface of the vane when the vane is provided with the through hole of the second embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in the following embodiments, the same or equivalent portions are denoted by the same reference numerals in the drawings, and the description thereof is omitted.

(first embodiment)

The first embodiment will be explained with reference to the drawings. The centrifugal fan according to the present embodiment is used for a centrifugal blower included in an air conditioner, a ventilator, or the like.

As shown in fig. 1 and 2, the centrifugal fan 1 includes a side plate 2, a main plate 3, and a plurality of blades 4. The side plate 2 is formed in an annular shape and has a suction port 5 for sucking air at a central portion thereof. The side plate 2 has a bell-mouth shape approaching the main plate 3 side from the suction port 5 in the central portion toward the outer peripheral side. The outer peripheral portion of the side plate 2 may be annular and perpendicular to the rotation axis Ax of the centrifugal fan 1.

The main plate 3 is formed in a disk shape and is provided so as to face the side plate 2. The main plate 3 has a shape in which the central portion protrudes toward the suction port 5. The motor fastening portion 31 provided at the center of the main plate 3 is fixed to a shaft of a motor not shown.

The plurality of blades 4 are disposed at predetermined intervals in the rotational direction between the main plate 3 and the side plate 2. In the present embodiment, one side of the plurality of blades 4 in the direction of the rotation axis Ax is fixed to the main plate 3, and the other side of the plurality of blades 4 in the direction of the rotation axis Ax is fixed to the side plate 2. That is, the main plate 3, the side plate 2, and the plurality of blades 4 are integrally formed. The plurality of blades 4 extend rearward in the rotational direction from the leading edge 6 toward the trailing edge 7. Thus, the centrifugal fan 1 is a turbo fan. In the figure, an arrow R indicates a rotation direction of the centrifugal fan 1.

The centrifugal fan 1 rotates together with the shaft of the motor. When the centrifugal fan 1 rotates, air sucked from the suction port 5 flows through a flow path between the plurality of blades 4 (hereinafter, referred to as an inter-blade flow path) from the leading edge 6 side to the trailing edge 7 side of the blade 4. The air flowing through the inter-blade flow path is blown out radially outward from an air outlet formed between the trailing edge 7 of the blade 4, the side plate 2, and the main plate 3.

Each of the plurality of blades 4 has at least one through hole 10 penetrating the negative pressure surface 8 and the positive pressure surface 9. The negative pressure surface 8 is a surface on the rear side in the rotation direction of the blade 4. The positive pressure surface 9 is a surface on the front side in the rotation direction of the blade 4, and is also referred to as a pressure surface. In the present embodiment, each of the plurality of blades 4 has a plurality of through holes 10. In fig. 2, letters are marked at the ends of numerical characters in order to distinguish the through holes 10 from one another. In the following description, letters are given to the ends of the numerical characters of the through holes 10 as necessary.

The through-holes 10 of the blades 4 are provided so as to satisfy the following conditions (a), (B), and (C). At least a part of the plurality of through holes 10 may satisfy the conditions (a), (B), and (C).

(A) The plurality of through holes 10 are provided on the trailing edge 7 side of the maximum warping position of the blade 4.

In fig. 3, the maximum warping position formed between the leading edge 6 and the trailing edge 7 in the blade 4 is indicated by a one-dot chain line W. The plurality of through holes 10 are provided at a portion between the maximum warping position and the trailing edge 7 of the blade 4. The through-hole 10 is provided at a position away from the rear edge 7, and the through-hole 10 does not open at the rear edge 7. Therefore, the wall surface 41 of the blade 4 is present between the trailing edge 7 and the through hole 10.

(B) The hole width of a predetermined through hole 10 among the plurality of through holes 10 is the same as or larger than the hole width of another through hole 10 adjacent to the predetermined through hole 10 on the side plate 2 side.

Here, as shown in fig. 3, in the present specification, a difference Δ D between a distance D1 from the inner wall on the leading edge 6 side to the leading edge 6 in the through-hole 10 and a distance D2 from the inner wall on the trailing edge 7 side to the leading edge 6 in the through-hole 10 is defined as a hole width. The hole width of the through hole 10 is the smaller of the difference measured on the positive pressure surface 9 and the difference measured on the negative pressure surface 8. Since the smaller orifice width becomes the rate-limiting of the air flow.

As shown in fig. 2, in the first embodiment, the plurality of through holes 10a to 10g arranged from a portion (hereinafter, referred to as an upper portion) on the side plate 2 side to an intermediate portion (hereinafter, referred to as an intermediate portion) of the blade 4 have the same hole width. The through-hole 10h has an aspect ratio larger than that of the through-hole 10g adjacent to the through-hole 10h on the side plate 2 side. The plurality of through holes 10h to 10j disposed in the blade 4 at a portion on the main plate 3 side (hereinafter referred to as a lower portion) have the same hole width.

In the first embodiment, the plurality of through holes 10 are circular in shape. Therefore, in the first embodiment, the plurality of through holes 10 can be said to have the same diameter as the predetermined through hole 10 and the other through holes 10 adjacent to the predetermined through hole 10 on the side plate 2 side or larger than the other through holes 10. The shape of the through-hole 10 is not limited to a circular shape, and may be arbitrarily set to, for example, a long hole, a polygonal shape, a D-shape, or the like.

(C) A predetermined through hole 10 of the plurality of through holes 10 is provided parallel to the rotation axis Ax of the centrifugal fan 1 or on the front edge 6 side with respect to the other through holes 10 adjacent to the predetermined through hole 10 on the side plate 2 side.

As shown in fig. 2, in the first embodiment, the plurality of through holes 10a to 10j are provided so that the center positions of the through holes 10 are aligned in parallel with the rotation axis Ax of the centrifugal fan 1.

After the structures of the second to seventh embodiments described below are described, the technical significance of the through-hole 10 of the first embodiment described above will be described.

(second to seventh embodiments)

The second to seventh embodiments will be explained. The second to seventh embodiments are modifications of the structure of the through hole 10 of the first embodiment, and other portions are the same as those of the first embodiment, and therefore only portions different from the first embodiment will be described. The through-holes 10 of the second to seventh embodiments are also provided so that at least some of them satisfy the conditions (a), (B), and (C) described in the first embodiment.

(second embodiment)

As shown in fig. 4, in the second embodiment, the through holes 10a to 10e disposed in the middle of the blade 4 have the same hole width. The through hole 10f has a larger hole width than the through hole 10e adjacent to the side plate 2. The through holes 10f to 10h disposed in the lower portion of the blade 4 have the same hole width.

In the second embodiment, the through holes 10a to 10e disposed in the middle of the blade 4 are provided so that the center positions of the through holes 10 are aligned parallel to the rotation axis Ax of the centrifugal fan 1. The through holes 10g and 10h disposed in the lower portion of the blade 4 are provided such that a predetermined through hole 10 is positioned on the front edge 6 side with respect to the other through holes 10a to 10f adjacent to the predetermined through hole 10 on the side plate 2 side.

In the second embodiment, the through-hole 10 is not provided in the upper portion of the blade 4 (i.e., the portion of the blade 4 on the side plate 2 side of the through-hole 10 a). This is based on experiments and simulations (hereinafter, referred to as experiments and the like) described later, and is for preventing a noise reduction effect due to the through-holes 10 from occurring in a predetermined region of the blade 4 on the side of the side plate 2. The predetermined region is set appropriately by an experiment or the like according to the shape of the centrifugal fan 1.

(third embodiment)

As shown in fig. 5, in the third embodiment, the through holes 10a to 10e disposed in the middle of the blade 4 have the same hole width. The through hole 10f has a larger hole width than the through hole 10e adjacent to the side plate 2. The through holes 10f to 10h disposed in the lower portion of the blade 4 have the same hole width.

In the third embodiment, the through holes 10a to 10h arranged from the middle portion to the lower portion of the blade 4 are arranged such that the center positions of the through holes 10 are aligned in parallel with the rotation axis Ax of the centrifugal fan 1.

In the third embodiment, the through-hole 10 is not provided in the upper portion of the blade 4.

(fourth embodiment)

As shown in fig. 6, in the fourth embodiment, the hole width of each of the through holes 10b to 10j arranged from the upper portion to the lower portion of the blade 4 is larger in the predetermined through hole 10 than in the through hole 10 adjacent to the side plate 2.

In the fourth embodiment, the through holes 10a to 10j are provided so that the center positions of the through holes 10 are aligned in parallel with the rotation axis Ax of the centrifugal fan 1.

(fifth embodiment)

As shown in fig. 7, in the fifth embodiment, the through holes 10a and 10b are long holes. In this case, the predetermined through-hole 10b has a larger hole width than the through-hole 10a adjacent to the side plate 2.

In the fifth embodiment, the through holes 10a and 10b are provided so that the center positions of the through holes 10 are aligned parallel to the rotation axis Ax of the centrifugal fan 1.

(sixth embodiment)

As shown in fig. 8, in the sixth embodiment, the through holes 10a and 10b are also long holes. In this case, the hole width of the predetermined through hole 10b is larger than the hole width of the through hole 10a adjacent to the side plate 2.

In the sixth embodiment, the center position of a predetermined through hole 10b of the through holes 10a and 10b is set on the front edge 6 side with respect to the center position of another through hole 10a adjacent to the predetermined through hole 10b on the side plate 2 side. Specifically, the through hole 10b disposed in the lower portion of the blade 4 is inclined so as to approach the rotation axis Ax of the centrifugal fan 1 from the side plate 2 side toward the main plate 3 side.

In the sixth embodiment, the through-hole 10 is not provided in the upper portion of the blade 4.

(seventh embodiment)

As shown in fig. 9 and 10, in the seventh embodiment, the through-hole 10 has a shape in which the opening area S2 at the positive pressure surface 9 of the blade 4 is larger than the opening area S1 at the negative pressure surface 8 of the blade 4. Even with such a shape, the through-hole 10 can obtain the same effects as those of the first to sixth embodiments.

Specifically, in the seventh embodiment, the shape of the wall 11 on the trailing edge 7 side out of the inner walls of the through-holes 10 of the blade 4 corresponds to the negative pressure surface 8 of the blade 4 positioned on the front side in the rotation direction of the blade 4. Thus, when the plurality of blades 4 are injection molded, the mold release direction of the mold disposed between the blades 4 can be made the same as the direction of the inner wall of the through-hole 10. As indicated by arrow M in fig. 10, the mold release direction of the mold disposed in the flow path between the blades during injection molding is a direction along the negative pressure surface 8 of the blade 4. Therefore, in the seventh embodiment, the blade 4 and the through hole 10 can be formed by one mold, and the manufacturing cost can be reduced.

(technical significance of through-holes)

Next, the technical significance of the through-hole 10 will be explained.

The through-holes 10 of the first to seventh embodiments reduce noise generated by rotation of the centrifugal fan 1. The through-holes 10 of the first to seventh embodiments suppress a reduction in air blowing efficiency due to a reduction in the area of the blades 4 caused by the through-holes 10, or improve air blowing efficiency.

First, the reason why noise is generated by the rotation of the centrifugal fan 1 will be described with reference to fig. 11.

In fig. 11, the velocity of the main flow flowing through the outlet of the inter-blade flow path is indicated by an arrow v, and the axis of the vortex as a noise source is indicated by an arrow ω.

Here, according to the vortex sound theory of Powell, the sound source term is represented by div (v × ω), and a larger value indicates a larger noise. div represents a divergence, and the gush and the inhale in a minute voxel become large. In addition, v represents the main flow velocity, and ω represents the vorticity. That is, the noise is the outer product of the main flow velocity v and the vorticity ω. Therefore, the large vortex is orthogonal to the main flow, and a sound is emitted from a portion where the vortex is generated or disappears. Therefore, noise can be reduced by reducing the vortex generated at the outlet of the inter-blade flow path. In order to reduce the vortex generated at the outlet of the inter-blade flow path, the fluctuation of the flow velocity at the outlet of the inter-blade flow path (i.e., the flow velocity deviation) may be reduced.

Fig. 12 shows the variation in the flow velocity of the flow path between the blades in the case where the serrations are provided on the trailing edge 7 of the blade 4. In the inter-blade flow path, the flow velocity near the negative pressure surface 8 is high, and the flow velocity near the positive pressure surface 9 is low. Therefore, when the serrations are provided on the trailing edge 7 of the blade 4, the air flowing near the positive pressure surface 9 in the predetermined inter-blade flow path passes through the notches of the serrations and flows to another inter-blade flow path located on the rear side in the rotation direction from the predetermined inter-blade flow path, as indicated by the arrow F. Therefore, in the other inter-blade flow paths, the air having a high flow velocity flowing in the vicinity of the negative pressure surface 8 is pushed out to the rear side in the rotation direction, and the flow velocity at the outlet of the inter-blade flow path is nearly uniform. Therefore, the vortex formed in the vicinity of the trailing edge 7 of the blade 4 becomes small, and the noise is reduced. Furthermore, this was found by the inventors' study.

Fig. 13 to 16 are schematic views showing a case where serrations are provided at the trailing edge 7 of the blade 4 as comparative examples of the present invention.

Fig. 13 shows a general shape of the serration 20. Fig. 14 shows a shape in which the notch of the saw tooth 20 is cut deeply toward the front edge 6. Fig. 15 shows a shape in which the flow velocity is locally reduced by making the concave and convex portions of the serrations 20 rectangular. Fig. 16 shows a shape in which the serrations 20 are enlarged in the direction of the rotation axis Ax of the centrifugal fan 1. When the serrations 20 are formed in such a shape, the flow rate of air flowing from the inter-blade flow path on the front side in the rotation direction into the inter-blade flow path on the rear side in the rotation direction can be increased. However, the saw teeth 20 shown in fig. 13 to 16 have a problem that the air blowing efficiency is reduced due to the reduction in the area of the blade 4. In addition, since the serrations 20 shown in fig. 13 to 16 cause the air flowing into the inter-blade flow path from the cutout portion to be immediately blown out to the outside of the inter-blade flow path, it is considered that the effect of pushing out the air flowing in the vicinity of the negative pressure surface 8 in the inter-blade flow path at a high flow velocity toward the positive pressure surface 9 side is weak.

Therefore, as shown in fig. 17 to 19, the inventors have created a structure in which the blade 4 is provided with the through-hole 10. This can improve the effect of the air flowing from the upstream side of the trailing edge 7 of the blade 4 to the inter-blade flow path on the rear side in the rotation direction through the through hole 10 to push out the air flowing near the negative pressure surface 8 in the inter-blade flow path at a high flow velocity toward the positive pressure surface 9. The shape of the through-hole 10 may be any shape such as a triangle, a quadrangle, or a circle, but if it is a circle, the reduction in the area of the blade 4 can be minimized.

Fig. 20 to 22 show flow velocity distributions at the outlet of the inter-blade flow path in the case where the blade 4 is provided with the serrations 20 and in the case where the blade 4 is provided with the through-hole 10. Fig. 20 shows the positions of the outlets of the inter-blade flow paths shown in fig. 21 and 22. That is, fig. 21 and 22 are numerical analysis diagrams showing the CFD (computational fluid dynamics) of the flow velocity distribution from the trailing edge 7 of the blade 4 on the front side in the rotation direction to the trailing edge 7 of the blade 4 on the rear side in the rotation direction at the outlet of the predetermined inter-blade flow path. Specifically, fig. 21 shows the velocity distribution at the outlet of the inter-blade flow path in the case where the serrations 20 are provided to the blade 4. Fig. 22 shows a velocity distribution at the outlet of the inter-blade flow path in the case where the through-hole 10 is provided in the blade 4.

The velocity distribution (see fig. 22) at the outlet of the inter-blade flow path in the case where the through-holes 10 are provided in the blade 4 has a smaller fluctuation in flow velocity as a whole than the velocity distribution (see fig. 21) at the outlet of the inter-blade flow path in the case where the serrations 20 are provided in the blade 4. In particular, when comparing the lower right portion of fig. 21 and 22 (i.e., the portion near the suction surface 8 of the blade 4 and near the main plate 3), the following can be observed. That is, when the serrations 20 are provided in the vane 4, the flow velocity is high in the vicinity of the negative pressure surface 8 of the vane 4 and in the vicinity of the main plate 3, but when the through-hole 10 is provided in the vane 4, the flow velocity is low in the region and uniform in other regions.

In this way, when the through-holes 10 are provided in the vane 4, the flow velocity is made uniform as a whole, as compared with the case where the serrations 20 are provided in the vane 4. This is considered to be because, when the through-holes 10 are provided in the blade 4, air flows into the inter-blade flow path from the upstream side of the trailing edge 7 of the blade 4 through the through-holes 10, and therefore the effect of pushing out air flowing in the vicinity of the negative pressure surface 8 in the inter-blade flow path at a high flow velocity toward the positive pressure surface 9 is enhanced.

Next, fig. 23 shows flow rate variations at the outlet of the inter-blade flow path in the case where the blade 4 is not provided with the serrations 20 or the through holes 10 (hereinafter, referred to as a basic shape), in the case where the blade 4 is provided with the serrations 20, and in the case where the blade 4 is provided with the through holes 10. The flow velocity variation at the outlet of the inter-blade flow path means the non-uniformity of the flow velocity when the flow velocity at the outlet of the inter-blade flow path is viewed in the circumferential direction.

As shown in fig. 23, in the case where the serrations 20 and the through holes 10 are provided in the blade 4 at the upper portion of the blade 4, the flow velocity deviation becomes larger than the basic shape. However, since the flow rate of the main flow flowing through the outlet of the inter-blade flow path is small above the blades 4, the influence on the noise is small. However, as shown in the second, third, and sixth embodiments shown in fig. 4, 5, and 8, it is preferable that the through-hole 10 is not provided in the upper portion of the blade 4.

On the other hand, in the middle and lower portions of the blade 4, the flow rate deviation becomes smaller in the case where the serrations 20 are provided in the blade 4 than in the case of the basic shape. Further, the flow rate variation becomes smaller in the case where the blade 4 is provided with the through hole 10. Accordingly, it can be said that the noise can be further reduced by providing the through-holes 10 in the blade 4 than by providing the serrations 20 in the blade 4.

Next, fig. 24 shows the flow velocity variation at the outlet of the flow path between the vanes in the case of the basic shape and in the case where the vanes 4 are provided with the through holes 10 having different inner diameters. Specifically, in the case where the plurality of through holes 10 are arranged in parallel with the rotation axis Ax of the centrifugal fan 1, the plurality of through holes 10 are each examined to have an inner diameter of 1mm, an inner diameter of 2mm, and an inner diameter of 2.5 mm.

In the upper portion of the blade 4, the flow velocity deviation becomes larger in the case where the through hole 10 is provided in the blade 4 than in the basic shape. However, since the flow rate of the main flow flowing through the outlet of the inter-blade flow path is small at the upper portion of the blade 4, the influence on the noise is small. However, as shown in the second, third, and sixth embodiments shown in fig. 4, 5, and 8, it is preferable that the through-hole 10 is not provided in the upper portion of the blade 4.

On the other hand, in the middle and lower portions of the vane 4, the flow rate deviation becomes smaller in the case where the through hole 10 having a large inner diameter is provided in the vane 4 than in the case where the through hole 10 having a small inner diameter is provided in the vane 4. Thus, by providing the through-hole 10 having a large inner diameter in the blade 4, noise can be further reduced.

Specifically, the flow velocity variation is smaller in the lower portion of the vane 4 than in the middle portion of the vane 4 by increasing the inner diameter of the through hole 10. Accordingly, it can be said that the noise can be further reduced by increasing the inner diameter of the through hole 10 disposed at the lower portion of the blade 4 as compared with the inner diameter of the through hole 10 disposed at the middle portion of the blade 4. Therefore, as shown in the above condition (B), the width of a predetermined through hole 10 among the plurality of through holes 10 is equal to or larger than the width of another through hole 10 adjacent to the predetermined through hole 10 on the side of the side plate 2, and noise can be further reduced.

Next, fig. 25 shows the flow velocity variation at the outlet of the inter-blade flow path in the case of the basic shape and in the case of changing the position of the through hole 10 in the radial direction of the centrifugal fan 1. Specifically, when the plurality of through holes 10 are arranged in parallel with the rotation axis Ax of the centrifugal fan 1, it is considered that the distance between the center position of the plurality of through holes 10 and the rear edge 7 of the blade 4 is 4mm and the distance is 14 mm.

In the upper portion of the blade 4, the flow velocity deviation becomes larger in the case where the through hole 10 is provided in the blade 4 than in the basic shape. However, since the flow rate of the main flow flowing through the inter-blade flow path outlet at the upper portion of the blade 4 is small, the influence on the noise is small. However, as in the second, third, and sixth embodiments shown in fig. 4, 5, and 8, it is preferable that the through-hole 10 is not provided in the upper portion of the blade 4.

In the case where the through-hole 10 is provided in the center of the blade 4 at a position close to the trailing edge 7 of the blade 4, the flow velocity deviation is smaller than that in the basic shape. On the other hand, the flow velocity deviation becomes larger in the case where the through holes 10 are provided at a position distant from the trailing edge 7 of the blade 4 than in the case where the through holes 10 are provided at a position close to the trailing edge 7 of the blade 4.

On the other hand, in the lower portion of the blade 4, the flow velocity deviation is smaller than that in the basic shape in the case where the through hole 10 is provided at a position close to the trailing edge 7 of the blade 4. Further, the flow velocity deviation is smaller in the case where the through-hole 10 is provided at a position distant from the trailing edge 7 of the blade 4 than in the case where the through-hole 10 is provided at a position close to the trailing edge 7 of the blade 4.

Accordingly, it can be said that the noise can be further reduced by providing the through-hole 10 in the middle of the blade 4 at a position close to the trailing edge 7 of the blade 4. On the other hand, it can be said that the noise can be further reduced by providing the through-hole 10 at a position away from the trailing edge 7 of the blade 4 in the lower portion of the blade 4. Therefore, as shown in the above condition (C), a predetermined through hole 10 of the plurality of through holes 10 is disposed in parallel with the rotation axis Ax of the centrifugal fan 1 or in the front edge 6 side with respect to the other through holes 10 adjacent to the predetermined through hole 10 on the side plate 2 side, whereby noise can be further reduced.

Next, fig. 26 shows the specific noise and the fan efficiency of the centrifugal fan 1 in the case of the basic shape, the case of the blade 4 provided with the serrations 20, and the case of the blade 4 provided with the through-holes 10 as in the first and second embodiments shown in fig. 2 and 4. In fig. 26, the specific noise and the air blowing efficiency of the centrifugal fan 1 having the basic shape are set to reference values 0, respectively, and the difference between the respective modes with respect to the reference values is shown. The fan efficiency and the air blowing efficiency are the same.

In view of the noise of the centrifugal fan 1, the case where the serrations 20 are provided to the blades 4 becomes smaller than the basic shape. In addition, when the through-hole 10 is provided as in the first embodiment, noise is reduced as compared with when the serrations 20 are provided to the blade 4. In addition, the case where the through-holes 10 are provided as in the second embodiment is smaller in noise than the case where the through-holes 10 are provided as in the first embodiment.

Therefore, as in the first embodiment, by providing the blade 4 with the through hole 10, noise can be reduced as compared with the case where the serration 20 is provided. Further, as in the second embodiment, the through-holes 10 are not provided in the upper portion of the blade 4, and the through-holes 10 in the lower portion of the blade 4 are disposed on the front edge 6 side, whereby noise can be further reduced.

In the case where the serrations 20 are provided to the blades 4, the air blowing efficiency of the centrifugal fan 1 is lower than that of the basic shape. In contrast, when the through-holes 10 are provided as in the first embodiment, the reduction in air blowing efficiency is suppressed as compared with the case where the serrations 20 are provided in the blades 4. In addition, when the through-holes 10 are provided as in the second embodiment, the air blowing efficiency is improved as compared with the basic shape.

Therefore, as in the first embodiment, by providing the through holes 10 in the blade 4, it is possible to suppress a decrease in air blowing efficiency as compared with the serrations 20. Further, as in the second embodiment, the through hole 10 is not provided in the upper portion of the blade 4, and the through hole 10 in the lower portion of the blade 4 is disposed on the front edge 6 side, whereby the air blowing efficiency can be improved as compared with the basic shape.

Next, the reason why the air blowing efficiency is improved as compared with the basic shape when the through-hole 10 is provided as in the second embodiment will be described.

Fig. 27 shows the total pressure distribution of the air flowing on the positive pressure surface 9 of the vane 4 in the basic shape. On the other hand, fig. 28 shows the total pressure distribution of the air flowing on the positive pressure surface 9 of the vane 4 when the through-hole 10 is provided as in the second embodiment.

The total pressure distribution (see fig. 28) of the positive pressure surface 9 of the second embodiment is larger in the vicinity of the trailing edge 7 of the blade 4 in the vertical direction of the blade 4 (i.e., the direction of the rotation axis Ax) than the total pressure distribution (see fig. 27) of the positive pressure surface 9 of the basic shape. Further, the total pressure distribution of the positive pressure surface 9 (see fig. 28) of the second embodiment is larger in the vicinity of the main plate 3 at the trailing edge 7 of the blade 4 than the total pressure distribution of the positive pressure surface 9 of the basic shape (see fig. 27). This is because, when the through-holes 10 are provided in the blade 4, air flows into the inter-blade flow path from a position upstream of the trailing edge 7 of the blade 4 through the through-holes 10, and the air flow approaches the positive pressure surface 9 side in the inter-blade flow path, so that the pressure increases near the trailing edge 7 of the blade 4 and the main plate 3.

When the through-holes 10 are provided as in the second embodiment shown in fig. 4, the through- holes 10g and 10h disposed in the lower portion of the blade 4 are provided on the front edge 6 side with respect to the other through-holes 10a to 10f adjacent to the side plate 2 side. Therefore, the area of the wall surface 41 between the through holes 10g and 10h in the blade 4 and the trailing edge 7 is increased, and work for pushing air out of the outlet of the inter-blade flow path can be performed by the wall surface 41.

As described above, the air flows from the position on the upstream side of the trailing edge 7 of the blade 4 into the inter-blade flow path through the through hole 10, and the air flow approaches the positive pressure surface 9 side in the inter-blade flow path, so that the pressure in the trailing edge 7 of the blade 4 and in the vicinity of the main plate 3 increases. This increases the amount of work on the wall surface 41 between the through holes 10g and 10h and the trailing edge 7 of the blade 4. Therefore, the air blowing efficiency is improved compared to the basic shape when the through-hole 10 is provided as in the second embodiment. Also in the sixth embodiment and the seventh embodiment shown in fig. 8 and 9, similarly, the air blowing efficiency is improved as compared with the basic shape.

(other embodiments)

The present invention is not limited to the above-described embodiments, and can be modified as appropriate. The above embodiments can be appropriately combined, except for the case where they are not related to each other or the case where it is obviously impossible to combine them. It is needless to say that in each of the above embodiments, elements constituting the embodiments are not necessarily essential except for cases where they are specifically indicated to be essential and cases where they are apparently considered to be essential in principle. In the above embodiments, when numerical values such as the number, numerical value, amount, and range of the constituent elements of the embodiments are mentioned, the number is not limited to a specific number unless otherwise stated explicitly or clearly in principle. In the above embodiments, the shapes, positional relationships, and the like of the constituent elements are not limited to the shapes, positional relationships, and the like, unless otherwise stated explicitly or the principle is limited to a specific shape, positional relationship, and the like.

(1) In the above embodiments, the centrifugal fan 1 is exemplified by a turbo fan, but the present invention is not limited to this, and the centrifugal fan 1 may be a radial fan, a sirocco fan, or the like.

(2) Further, the plurality of through holes 10 of the blade 4 may have the same hole width.

(3) In addition, the plurality of through holes 10 of the blade 4 may be partially mixed with portions that do not satisfy the conditions (a), (B), and (C).

(4) Further, each of the plurality of blades 4 may have one through hole 10.

(5) In the above embodiments, the structure in which the main plate 3, the side plate 2, and the plurality of blades 4 rotate integrally has been described, but the present invention is not limited to this, and only the main plate 3 and the plurality of blades 4 may rotate, only the side plate 2 and the plurality of blades 4 may rotate, or only the plurality of blades 4 may rotate.

(conclusion)

According to a first aspect shown in part or all of the above embodiments, the centrifugal fan is used for the centrifugal blower. The centrifugal fan includes: an annular side plate having an air suction port; the main plate is arranged opposite to the side plate; and a plurality of blades arranged at a predetermined interval in the rotation direction between the side plate and the main plate. The blade has a through hole penetrating the negative pressure surface and the positive pressure surface. The through hole is not open at the rear edge.

According to a second aspect, the through hole is provided on the trailing edge side than a maximum warping position formed between the leading edge and the trailing edge of the blade.

Thus, the air in the predetermined inter-blade flow path flows into the other inter-blade flow path located on the rear side in the rotation direction through the through hole on the rear edge side of the maximum warping position of the blade. Therefore, the air flow having a high flow velocity flowing in the vicinity of the negative pressure surface in the other inter-blade flow path is pushed out to the rear side in the rotational direction by the air flowing in from the through hole, and spreads to the positive pressure surface side having a low flow velocity, so that the flow velocity variation at the outlet of the inter-blade flow path can be made nearly uniform. Therefore, since the vortex formed in the vicinity of the trailing edge of the blade becomes weak, noise can be reduced.

Further, the wall surface between the through hole and the trailing edge in the blade performs work for pushing air out to the outside of the outlet of the inter-blade flow path, and thus the reduction in air blowing efficiency can be suppressed or the air blowing efficiency can be improved.

According to a third aspect, each of the plurality of blades has a plurality of through holes.

This allows the position and opening area of the through hole to be arbitrarily adjusted while maintaining the rigidity of the blade.

According to the fourth aspect, the difference between the distance from the inner wall on the leading edge side in the through-hole to the leading edge and the distance from the inner wall on the trailing edge side in the through-hole to the leading edge is defined as the hole width. In this case, the width of a predetermined through hole among the plurality of through holes is equal to or larger than the width of another through hole adjacent to the predetermined through hole on the side plate side.

Thus, it was found through experiments and the like by the inventors that the noise reduction effect by the through-hole is different at the position on the main plate side of the blade, the position near the middle between the main plate and the side plate of the blade, and the position on the side plate side of the blade. Specifically, it was found that the noise reduction effect by the through-holes is large at the main plate side portion of the blade, the noise reduction effect by the through-holes is small at the portion near the middle between the main plate and the side plate of the blade, and the noise reduction effect by the through-holes is almost no at the side plate side portion of the blade.

Therefore, in the fourth aspect, the hole width of a predetermined through hole among the plurality of through holes is equal to or larger than the hole width of another through hole adjacent to the predetermined through hole on the side plate side. This can suppress a reduction in the area of the blade due to the through-hole, and further improve the noise reduction effect. In addition, since the area of the blade is suppressed from being reduced by the through hole, a reduction in air blowing efficiency can be suppressed.

In accordance with a fifth aspect, a predetermined through hole of the plurality of through holes is provided in parallel with the rotation axis of the centrifugal fan or in the leading edge side with respect to another through hole adjacent to the predetermined through hole on the side plate side.

Thus, it has been found through experiments by the inventors that work for pushing air out of the outlet of the inter-blade flow path is performed through the wall surface between the through hole in the blade and the trailing edge. Further, it was found that the work amount is larger at the main plate side portion of the blade than at the side plate side portion of the blade.

In the fifth aspect, therefore, a predetermined through hole of the plurality of through holes is provided in parallel with the rotation axis of the centrifugal fan or in the leading edge side with respect to another through hole adjacent to the predetermined through hole on the side plate side. Accordingly, the amount of work for pushing air out of the outlet of the inter-blade flow path can be increased in the wall surface between the through hole in the blade and the trailing edge, particularly, by the wall surface located on the main plate side. Therefore, the centrifugal fan can further suppress a decrease in air blowing efficiency or can further improve air blowing efficiency.

In accordance with a sixth aspect, a predetermined through hole of the plurality of through holes is provided in parallel with the rotation axis of the centrifugal fan or in the leading edge side with respect to another through hole adjacent to the predetermined through hole on the side plate side. The hole width of the predetermined through hole is equal to or larger than the hole width of another through hole adjacent to the predetermined through hole on the side plate side.

Accordingly, the amount of work for pushing air out of the outlet of the inter-blade flow path can be increased in the wall surface between the through hole in the blade and the trailing edge, particularly, by the wall surface located on the main plate side. In addition, the noise reduction effect can be further improved while suppressing the reduction in the area of the blade due to the through hole. Therefore, the centrifugal fan can reduce noise, and can suppress a reduction in air blowing efficiency or can improve air blowing efficiency.

According to the seventh aspect, the opening area of the through hole at the positive pressure surface of the vane is larger than the opening area at the negative pressure surface of the vane.

Accordingly, even if the through-hole has such a shape, noise can be reduced as in the first to sixth aspects, and a reduction in air blowing efficiency can be suppressed or the air blowing efficiency can be improved.

Further, when the shape of the trailing edge side of the inner wall of the through hole of a predetermined blade is set to a shape corresponding to the negative pressure surface of the blade located on the front side in the rotation direction of the blade, the mold release direction of the mold disposed between the blades is the same as the direction of the inner wall of the through hole in the case of injection molding a plurality of blades. Further, the mold release direction of the mold disposed in the flow path between the blades at the time of injection molding is a radial direction outside along the negative pressure surface of the blade. Therefore, the blade and the through hole can be formed by one mold, and the manufacturing cost can be reduced.

Claims (7)

1. A centrifugal fan for a centrifugal blower is characterized by comprising:

an annular side plate (2) having an air intake port (5);

a main plate (3) arranged opposite to the side plate; and

a plurality of blades (4) arranged at a predetermined interval in the rotation direction between the side plate and the main plate,

the blade has a through hole (10) that penetrates the negative pressure surface (8) and the positive pressure surface (9) and does not open at the trailing edge (7).

2. The centrifugal fan of claim 1,

the through hole is provided on the trailing edge side than a maximum warping position (W) formed between a leading edge and the trailing edge in the blade.

3. The centrifugal fan according to claim 1 or 2,

the plurality of blades have a plurality of through holes, respectively.

4. The centrifugal fan according to any one of claims 1 to 3,

when a difference (Δ D) between a distance (D1) from a leading edge-side inner wall of the through-holes to the leading edge and a distance (D2) from a trailing edge-side inner wall of the through-holes to the leading edge is defined as a hole width,

the width of a predetermined through hole among the plurality of through holes is equal to or larger than the width of another through hole adjacent to the predetermined through hole on the side plate side.

5. The centrifugal fan according to any one of claims 1 to 4,

the predetermined through hole among the plurality of through holes is provided in parallel with a rotation axis (Ax) of the centrifugal fan or on a leading edge side with respect to the other through holes adjacent to the predetermined through hole on the side plate side.

6. The centrifugal fan according to claim 4 or 5,

a predetermined through hole of the plurality of through holes is provided in parallel with a rotation axis of the centrifugal fan or in the leading edge side with respect to another through hole adjacent to the predetermined through hole on the side plate side,

the hole width of the predetermined through hole is equal to or larger than the hole width of another through hole adjacent to the predetermined through hole on the side plate side.

7. The centrifugal fan according to any one of claims 1 to 6,

an opening area (S2) of the through hole at the positive pressure surface of the vane is larger than an opening area (S1) at the negative pressure surface of the vane.

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