CENTRIFUGAL FAN
A centrifugal fan includes a hub, a plurality of blades, and a shroud. The blades each have a curved part that is curved to incline toward a side on which air impinges when a connected end connected to an inwardly protruding portion of the shroud moves in a rotating direction of the centrifugal fan. The hub includes a hub-side diffuser ring that protrudes radially outward of the blades. The shroud includes a shroud-side diffuser ring that protrudes radially outward of the blades.
The present invention relates to a centrifugal fan.
BACKGROUND ARTCentrifugal fans such as turbo fans have conventionally been used to supply air at high pressure in air handling units and other air conditioning apparatuses for large-scale air conditioning of the interior of a building. A turbo fan is a fan that has backward-inclined blades, and configured to blow out air radially outward. The turbo fan thus has the advantage of being simply configured since it does not require a scroll casing such as that of a sirocco fan. However, one problem is that the flow of air, immediately after being expelled by the blades, impinges on objects around the blades and is disturbed, which leads to increased noise and reduced efficiency.
For this reason, conventionally, in a configuration that includes a hub, a plurality of blades arranged in a circumferential direction of the hub, and a shroud arranged on the opposite side of the blades from the hub, diffuser rings are provided radially on the outer side of the blades, as in the turbo fans described in Patent Literature 1 and 2. In the turbo fans described in Patent Literature 1 and 2, the shroud and the hub have larger outer diameters than the outer diameter of the blades. Parts of the shroud and hub that are positioned on the outer side of the blades form the respective diffuser rings.
This provides the so-called diffuser effect, whereby the speed of the air expelled by the blades is reduced as the air passes through between the diffuser rings, i.e., the effect that effectively converts the kinetic energy of the air to pressure. This enables an improvement in the fan efficiency.
The blades in such a turbo fan are usually two-dimensional blades that have uniform cross sections orthogonal to the axial direction of the rotating shaft of the turbo fan at positions displaced along the axial direction. The two-dimensional blades are each connected to an inwardly protruding portion of the shroud at an acute angle.
In the configuration of the turbo fan having diffuser rings such as those described in Patent Literature 1 and 2, as shown in
Patent Literature 1: Japanese Unexamined Patent Publication No. H11-108403
Patent Literature 2: U.S. Patent Publication No. 2006/0228212
SUMMARY OF INVENTIONIn view of the circumstances described above, an object of the present invention is to provide a centrifugal fan that can improve the diffuser effect of diffuser rings that converts kinetic energy of the air to pressure.
A centrifugal fan of the present invention is characterized to include: a hub; a plurality of blades arranged along a circumferential direction of the hub; and a shroud arranged on an opposite side of the blades from the hub, the blades each having a curved part that is curved to incline toward a side on which air impinges when a connected end connected to an inwardly protruding portion of the shroud moves in a rotating direction of the centrifugal fan, the hub having a hub-side diffuser ring that protrudes radially outward of the blades, and the shroud having a shroud-side diffuser ring that protrudes radially outward of the blades.
Hereinafter, an indoor unit of an air conditioner according to embodiments of the present invention will be described in detail with reference to the drawings.
The indoor unit 31 shown in
The indoor unit 31 includes a blower 51 equipped with a centrifugal fan 23, a fan motor 11 that drives the centrifugal fan 23 to rotate, a heat exchanger 43 surrounding the outer side of the centrifugal fan 23, a drain pan 45, and an air filter 41.
The blower 51 includes the centrifugal fan 23 that is a turbo fan, and a bell mouth 25.
The centrifugal fan 23 includes, as shown in
The hub 15 is secured to the rotating shaft 13 of the fan motor 11 that is fixed to the top plate of the housing 33.
The hub 15 has a hub-side diffuser ring 27 that protrudes radially outward of the blades 21. More specifically, the hub-side diffuser ring 27 has a ring-like shape and is formed to extend outward beyond the rear edges 21b of respective blades 21.
The shroud 19 is arranged opposite the hub 15 on the front side F in the axial direction A of the rotating shaft 13 (see
The shroud 19 has a shroud-side diffuser ring 26 that protrudes radially outward of the blades 21. The shroud-side diffuser ring 26 is formed to extend outward beyond the rear edges 21b of respective blades 21 and arranged opposite the hub-side diffuser ring 27.
The mutually opposing faces of the hub-side diffuser ring 27 and shroud-side diffuser ring 26 are smoothly continuous with the mutually opposing faces of the hub 15 and shroud 19, respectively.
Moreover, the distance between the diffuser rings 27 and 26 is set such as to gradually increase radially outward of the centrifugal fan 23, as shown in
The plurality of blades 21 are aligned and spaced apart a certain distance along the circumferential direction of the air inlet 19a between the hub 15 and shroud 19. One end on the front side F (see
Each blade 21 shown in
Each blade 21 includes, as shown in
The connected end 21c leads to an inwardly protruding portion 19b of the shroud 19. The inwardly protruding portion 19b of the shroud 19, more specifically, is a curved portion protruding inward of the centrifugal fan 23 as shown in
The curved part 21d is curved to incline toward a side 21c1 on which air impinges when the connected end 21c moves in the rotating direction B of the centrifugal fan 23.
More specifically, the curved part 21d is formed by protruding a portion of the blade 21 on the side near the shroud 19 out, relative to the main part 21h, toward the side opposite from the side 21d1 which the air impinges on when that portion moves in the rotating direction B of the centrifugal fan 23. The connected end 21c is connected to the inwardly protruding portion 19b of the shroud 19 generally orthogonally to a tangential line C (see
Therefore, as shown in
As shown in
Since the hub-side end 21e at the rear edge 21b of the blade 21 is located on the front side in the rotating direction B, the air flows along the inclined front surface 21g of the blade 21 (i.e., forward side in the rotating direction B) as indicated by arrow F1 in
In order to ensure the diffuser effect, the outer diameter D2 of the hub-side diffuser ring 27 and the outer diameter D3 of the shroud-side diffuser ring 26 are each set to be 1.1 times or more larger than the diameter D1 of the circumscribed circle of the plurality of blades 21, as shown in
Moreover, as shown in
The centrifugal fan 23 configured as described above, with the shroud-side diffuser ring 26 and hub-side diffuser ring 27, can have significantly higher static efficiency as compared to a centrifugal fan without these diffuser rings.
For example, as shown in the graph of
The static efficiency η in the case with only the hub-side diffuser ring tends to be higher in the range of φ<about 0.23 of the flow coefficient φ, but not in the range of φ>about 0.23, as indicated by curve II. On the other hand, the static efficiency η in the case with only the shroud-side diffuser ring tends to be higher in the range of φ>about 0.15 of the flow coefficient φ, but not in the range of φ<about 0.15, as indicated by curve III.
It can be seen from the graph of
The centrifugal fan 23 of this embodiment has 3D shape blades 21 (so-called 3D blades) as mentioned above, as well as the pair of diffuser rings 26 and 27. In this 3D blade 21, the connected end 21c on the side of the shroud 19 has the curved part 21d (see
As can be see from the bar II in the chart of
On the other hand, as indicated by bar I in the chart of
From these results, it is understood that, in a centrifugal fan, the effect of providing diffuser rings to improve the maximum static efficiency (%) is higher in a configuration with 3D blades 21 combined with the diffuser rings 26 and 27 as in this embodiment than in a configuration with two-dimensional blades combined with diffuser rings as in the comparative example.
Such a difference in the effect is evident from a comparison of flow velocity distribution of the air blown out from the respective centrifugal fans of this embodiment and comparative example, as shown in
In the flow velocity distribution shown in
On the other hand, in the flow velocity distribution of the centrifugal fan 23 of this embodiment shown in
More specifically, the air flows on the shroud 19 side through the extension recess 29 (see
Therefore, the flow velocity distribution at the outlet 28 is substantially uniform. Namely, the air blown out from the outlet 28 flows not only near the diffuser ring 27 on the hub 15 side, but also near the diffuser ring 26 on the shroud 19 side. Since the flow velocity distribution at the outlet 28 is uniform, kinetic pressure is collected favorably, so that there is a lower ratio of kinetic energy of the air that is not converted to pressure energy, whereby the static efficiency of the centrifugal fan 123 can be improved.
From the results of experiments shown in
Other configurations of the indoor unit 31 are the same as those of a conventional cassette type indoor unit embedded in the ceiling. More specifically, it is configured as follows:
As shown in
As shown in
In the indoor unit 31 configured as described above, flow of the air F0 shown in
When the indoor unit 31 is operating as described above, as shown in
As described above, in the indoor unit 31 of this embodiment, in a configuration equipped with the blower 51 including the centrifugal fan 23 having the diffuser rings, the blades 21 each have a curved part 21d that is curved to incline toward the side 21c1 on which the air impinges when a connected end 21c connected to an inwardly protruding portion of the shroud 19 moves in the rotating direction B of the centrifugal fan 23, as shown in
In the indoor unit 31 of this embodiment, as shown in
In the indoor unit 31 of this embodiment, as shown in
While the shroud-side diffuser ring 26 and hub-side diffuser ring 27 are arranged to incline away from each other toward the respective distal ends in the embodiment described above, the present invention is not limited to this. As a variation example of the present invention, as shown in
The planar hub 15 such as the one described above is secured to the rotating shaft 13 of the motor 11 with a boss 30, which is a component separate from the hub 15. The boss 30 may be fixed to the hub 15, or not fixed to the hub.
The shape of the shroud-side diffuser ring 26 is not limited to a particular one in the present invention. For example, in another variation example of this embodiment, as shown in
The linearly extending portion 26a is continuous with the radially outer edge of the shroud 19, and extends linearly in the radial direction. The portion 26b extending in a circular arc form is continuous with the radially outer edge of the linearly extending portion 26a, and bends in a circular are form away from the hub-side diffuser ring 27 along the radial direction.
In the variation example shown in
While the shroud-side diffuser ring 26 shown in
Alternatively, the shroud-side diffuser ring 26 may be formed only by a linearly extending portion 26a, or only by a portion 26b that extends in a circular arc form.
In the embodiment described above, the connected end 21c of the blade 21 is orthogonal to the tangential line C of the inner face of the inwardly protruding portion 19b of the shroud 19, but the present invention is not limited to this. In the present invention, the connected end 21c may be connected to the inwardly protruding portion 19b of the shroud 19 at an angle that is not acute, and may be arranged, for example, orthogonal, or at an angle of 90° or more to the tangential line C of the inner face of the portion 19b.
The specific embodiments described above generally include the invention having the following configurations.
The centrifugal fan 23 of this embodiment is characterized to include a hub 15; a plurality of blades 21 arranged along a circumferential direction of the hub 15; and a shroud 19 arranged on an opposite side of the blades 21 from the hub 15, the blades 21 each having a curved part 21d that is curved to incline toward the side 21c1 on which the air impinges when a connected end 21c connected to an inwardly protruding portion of the shroud 19 moves in a rotating direction of the centrifugal fan 23, the hub 15 having a hub-side diffuser ring 27 that protrudes radially outward of the blades 21, and the shroud 19 having a shroud-side diffuser ring 26 that protrudes radially outward of the blades 21.
According to this configuration, the blades 21 each have a curved part 21d that is curved to incline toward the side 21c1 on which the air impinges when a connected end 21c connected to an inwardly protruding portion of the shroud 19 moves in a rotating direction of the centrifugal fan 23, so that there is no portion where the blade 21 is connected to the shroud 19 at an acute angle. As a result, in the portions where the blades 21 are connected to the shroud 19, the air is allowed to smoothly flow, so that there is less area where the air flow can be disturbed easily in these portions. This way, on the shroud 19 side, a drop in the flow velocity of the air due to a disturbance in the air can be prevented, as well as creation of an area where the air separates from the inner face of the shroud 19 can be prevented. Consequently, the diffuser effect of the hub 15 side and the shroud-side diffuser ring 26 that converts the kinetic energy of the air to pressure, in particular, the diffuser effect of the shroud-side diffuser ring 26, is improved.
The hub-side end 21e at the rear edge 21b of the blade 21 should preferably be positioned more forward in the rotating direction of the centrifugal fan 23 than the shroud-side end 21f of the rear edge 21b.
According to this configuration, the hub-side end 21e at the rear edge 21b of the blade 21 is positioned more forward in the rotating direction than the shroud-side end 21f, so that the air can flow easily toward the shroud 19 side because of the inclination of the blades 21 relative to the axial direction of the centrifugal fan 23, whereby the separation of air on the shroud 19 side can be prevented even more. This also makes the air flow uniform in the axial direction of the centrifugal fan 23, as a result of which the diffuser effect of the hub 15 side and the shroud-side diffuser ring 26 that converts the kinetic energy of the air to pressure, in particular, the diffuser effect of the shroud-side diffuser ring 26, is improved.
The hub-side diffuser ring 27 and the shroud-side diffuser ring 26 should preferably have outer diameters that are each 1.1 times or more larger than a diameter of a circumscribed circle of the plurality of blades 21.
According to this configuration, the diffuser effect of the hub-side diffuser ring 27 and shroud-side diffuser ring 26 that converts the kinetic energy of the air to pressure can be achieved reliably.
The shroud-side diffuser ring 26 should preferably include a portion 26a linearly extending in a radial direction of the centrifugal fan 23 continuously from an edge of the shroud 19.
According to this configuration, the air that flows along the inner wall of the shroud 19 can smoothly flow along the linearly extending portion 26a when the air reached the shroud-side diffuser ring 26. Therefore, separation of the air at the shroud-side diffuser ring 26 can be prevented.
The shroud-side diffuser ring 26 should preferably include a portion bent in an axial direction of the centrifugal fan 23 away from the hub-side diffuser ring 27, and the hub-side diffuser ring 27 should preferably extend in a radial direction of the centrifugal fan 23.
According to this configuration, the shroud-side diffuser ring 26 is formed to broaden in the axial direction of the centrifugal fan 23, so that the air can be made to flow more smoothly between the hub-side diffuser ring 27 and shroud-side diffuser ring 26. Moreover, since the hub-side diffuser ring 27 is not broadened in the axial direction but extends in the radial direction, it can form a plane coplanar with the portion of the hub 15 located inner than the hub-side diffuser ring 27, whereby an increase in the processing cost for the hub 15 can be suppressed. The shroud 19 is conventionally subjected to curved surface machining, so that the shroud-side diffuser ring 26 can be shaped to broaden in the axial direction without incurring an increase in the processing cost. Therefore, an increase in the processing cost of the entire centrifugal fan 23 can be suppressed.
Claims
1. A centrifugal fan comprising:
- a hub;
- a plurality of blades arranged along a circumferential direction of the hub; and
- a shroud arranged on an opposite side of the blades from the hub,
- each of the blades having a curved part that is curved to incline toward a side on which air impinges when a connected end connected to an inwardly protruding portion of the shroud moves in a rotating direction of the centrifugal fan,
- the hub having a hub-side diffuser ring that protrudes radially outward of the blades, and
- the shroud having a shroud-side diffuser ring that protrudes radially outward of the blades.
2. The centrifugal fan according to claim 1, wherein
- a hub-side end at a rear edge of each of the blades is positioned more forward in the rotating direction of the centrifugal fan than a shroud-side end of the rear edge.
3. The centrifugal fan according to claim 1, wherein
- the hub-side diffuser ring and the shroud-side diffuser ring have outer diameters that are each at least 1.1 times larger than a diameter of a circumscribed circle of the plurality of blades.
4. The centrifugal fan according to claim 1, wherein
- the shroud-side diffuser ring includes a portion linearly extending in a radial direction of the centrifugal fan continuously from an edge of the shroud.
5. The centrifugal fan according to claim 1, wherein
- the shroud-side diffuser ring includes a portion bent in an axial direction of the centrifugal fan away from the hub-side diffuser ring, and the hub-side diffuser ring extends in a radial direction of the centrifugal fan.
6. The centrifugal fan according to claim 2, wherein
- the hub-side diffuser ring and the shroud-side diffuser ring have outer diameters that are each at least 1.1 times larger than a diameter of a circumscribed circle of the plurality of blades.
7. The centrifugal fan according to claim 2, wherein
- the shroud-side diffuser ring includes a portion linearly extending in a radial direction of the centrifugal fan continuously from an edge of the shroud.
8. The centrifugal fan according to claim 3, wherein
- the shroud-side diffuser ring includes a portion linearly extending in a radial direction of the centrifugal fan continuously from an edge of the shroud.
9. The centrifugal fan according to claim 6, wherein
- the shroud-side diffuser ring includes a portion linearly extending in a radial direction of the centrifugal fan continuously from an edge of the shroud.
10. The centrifugal fan according to claim 2, wherein
- the shroud-side diffuser ring includes a portion bent in an axial direction of the centrifugal fan away from the hub-side diffuser ring, and the hub-side diffuser ring extends in a radial direction of the centrifugal fan.
11. The centrifugal fan according to claim 3, wherein
- the shroud-side diffuser ring includes a portion bent in an axial direction of the centrifugal fan away from the hub-side diffuser ring, and the hub-side diffuser ring extends in a radial direction of the centrifugal fan.
12. The centrifugal fan according to claim 4, wherein
- the shroud-side diffuser ring includes a portion bent in an axial direction of the centrifugal fan away from the hub-side diffuser ring, and the hub-side diffuser ring extends in a radial direction of the centrifugal fan.
13. The centrifugal fan according to claim 6, wherein
- the shroud-side diffuser ring includes a portion bent in an axial direction of the centrifugal fan away from the hub-side diffuser ring, and the hub-side diffuser ring extends in a radial direction of the centrifugal fan.
14. The centrifugal fan according to claim 7, wherein
- the shroud-side diffuser ring includes a portion bent in an axial direction of the centrifugal fan away from the hub-side diffuser ring, and the hub-side diffuser ring extends in a radial direction of the centrifugal fan.
15. The centrifugal fan according to claim 8, wherein
- the shroud-side diffuser ring includes a portion bent in an axial direction of the centrifugal fan away from the hub-side diffuser ring, and the hub-side diffuser ring extends in a radial direction of the centrifugal fan.
16. The centrifugal fan according to claim 9, wherein
- the shroud-side diffuser ring includes a portion bent in an axial direction of the centrifugal fan away from the hub-side diffuser ring, and the hub-side diffuser ring extends in a radial direction of the centrifugal fan.
Type: Application
Filed: Dec 18, 2013
Publication Date: Dec 10, 2015
Inventors: Tooru IWATA (Sakai-shi, Osaka), Kaname MARUYAMA (Sakai-shi, Osaka), Shimei TEI (Sakai-shi, Osaka)
Application Number: 14/654,391