JPH08247090A - Centrifugal blower - Google Patents

Abstract

PURPOSE: To provide a centrifugal blower to be used for an air conditioner to improve deterioration of air blowing performance and an increasing phenomenon of turbulent noise caused by turbulence of an air current of a side plate part of an impeller. CONSTITUTION: An outlet head end part of a suction ring 8 is inserted in the neighbourhood of a suction port 4a of a side plate 4 of an impeller 1, small projections 9 are provided in a ring cocentrically with the center of the suction ring 8 on an inflow part surface of the suction ring 8, and height (h) of the projections 9 is set smaller than thickness of a laminar boundary layer formed on a suction ring surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of the blowing performance and noise reduction of a centrifugal blower used in an air conditioner or the like.

[0002]

2. Description of the Related Art Conventionally, centrifugal blowers have been widely used as blowers for air conditioners and the like, and in recent years, there has been a particularly strong demand for noise reduction.

Below, with reference to the drawings,
A conventional centrifugal blower proposed in Japanese Patent No. 81800 will be described.

FIG. 8 shows the structure of a conventional centrifugal blower. In FIG. 8, reference numeral 1 denotes an impeller, which is composed of a plurality of vane plates 2, a main plate 3 to which the vane plate 2 is fixed, and a side plate 4 fixed to an end face of the vane plate 2 on the side opposite to the main plate and having a suction port 4a. . A motor 5 is directly connected to the impeller 1, and is fixed to a casing 6 that houses the impeller 1 and the motor 5. Reference numeral 7 is a suction ring that is curved from the inlet end 7a to the outlet end 7b and has an inner diameter of the outlet end 7b larger than the minimum diameter of the suction portion, and is fixed to the casing 6. The outlet end 7b of the suction ring 7 is inserted in the vicinity of the suction port 4a of the side plate 4 of the impeller 1.

The operation of the centrifugal blower configured as described above will be described below.

First, the impeller 1 is driven by the driving force of the motor 5.
When is rotated, air is introduced into the impeller 1 through the suction ring 7, static pressure and dynamic pressure are added when passing between the plurality of blade plates 2, and the air is discharged from the impeller 1 into the casing 6. . After that, a part of the dynamic pressure in the casing 6 is converted into static pressure and is discharged to the outside of the casing 6 to perform an air blowing action. Figure 9
[Fig. 3] is a schematic view showing a state of an air flow around a suction ring. Normally, the impeller 1 is installed along the suction ring 7 as shown in FIG.
The airflow E flowing into the inside of the impeller 1 from its outlet end 7b.
When it flows in, it flows along the wall surface of the side plate 4 because it once adheres to the suction port 4a of the side plate 4 and flows in, and the flow in the impeller 1 flows without being greatly disturbed.

[0007]

However, in the above-described structure, the airflow G flowing along the surface of the suction ring 7 as shown in FIG. Since a thick laminar boundary layer is formed on the suction ring 7 and a large difference occurs between the airflow at the bottom of the laminar boundary layer on the surface of the suction ring 7 and the velocity of the main flow outside the laminar boundary layer, the airflow separates near the tip 7b of the suction ring 7. When flowing out, a strong shear stress acts between the airflows due to this large velocity difference, and the airflows are greatly disturbed by the action of the shear stress. In addition,
The airflow H flowing back from the inside of the shing 6 into the impeller 1 through the inner surface of the suction ring once adheres to the wall surface of the side plate 4 and then joins with the airflow in the impeller 1 which is greatly disturbed at a low speed from the surface of the suction ring tip 7b. Therefore, there is a problem that the turbulence of the air flow is amplified in the process of separating from the wall surface and flowing toward the outlet of the impeller 1 to form a turbulent flow region near the side plate, which lowers the blowing performance and increases turbulent noise.

In view of the above problems, the present invention provides a method for controlling the magnitude of turbulence of the air flow separated from the tip of the suction ring even when the operating point air volume of the centrifugal blower is large and a thick laminar boundary layer is formed on the surface of the suction ring. (EN) Provided is a centrifugal blower capable of suppressing the turbulence of the flow near the wall surface of a side plate and the deterioration of the blowing performance and the increase of noise due to separation in the wake, while keeping the size small.

[0009]

In order to solve the above-mentioned problems, a centrifugal fan according to the present invention comprises an impeller including a main plate, a plurality of vanes and a side plate having a suction port, and a suction ring inserted into the suction port of the side plate. And a minute projection concentric with the center of the suction ring and having a height smaller than the thickness of the laminar boundary layer is provided on the surface of the inflow portion of the suction ring.

In another centrifugal blower, a plurality of minute projecting plates whose height is smaller than the thickness of the laminar boundary layer concentrically with the center of the suction ring are provided on the surface of the inflow part of the suction ring, and the projecting plates are used as blades. It is provided with a configuration installed so as to be inclined in the rotation direction of the vehicle.

Still another centrifugal blower has a structure in which a plurality of communication hole holes are provided in the inflow portion of the suction ring concentrically with the center of the suction ring.

[0012]

According to the present invention, a laminar flow formed on the surface of the suction ring is provided by providing minute projections concentrically with the center of the suction ring and having a height smaller than the thickness of the laminar boundary layer on the surface of the suction ring. When the flow in the boundary layer flows over the minute protrusions, minute separation occurs, and a turbulent boundary layer is formed on the suction ring surface after the protrusions. The turbulent boundary layer has the property that the difference between the flow velocity near the wall surface and the flow velocity of the main flow outside the boundary layer is smaller than that of the laminar flow boundary layer.Therefore, when the air flow near the tip of the suction ring flows out from the wall surface of the suction ring, Shear stress due to the difference in velocity is suppressed to be small, and turbulence of the air flow due to shear stress is suppressed. Further, since the turbulence of the airflow flowing out from the surface of the suction ring is small, the airflow once adhering to the wall surface of the side plate is separated even when the airflow flowing back from the inside of the casing into the impeller through the inner surface of the suction ring merges. Without letting it out to the outlet of the impeller.

Further, a plurality of minute projecting plates concentrically with the center of the suction ring and having a height smaller than the thickness of the laminar boundary layer are provided on the surface of the inflow portion of the suction ring, and the projecting plates are inclined in the rotating direction of the impeller. By installing the turbulent boundary layer on the surface of the suction ring after the projection, minute separation occurs when the air flow in the laminar boundary layer formed on the surface of the suction ring flows over the projection plate and flows. The turbulence of the air flow that is formed and flows out from the tip of the suction ring is suppressed, and the inclination of the projection plate adds an air flow component to the air flow passing through the projection plate in the impeller rotation direction, increasing the total pressure at the impeller exit. To do.

Further, by providing a plurality of through hole holes concentrically with the center of the suction ring at the inflow portion of the suction ring, when the flow in the laminar boundary layer formed on the surface of the suction ring passes through these minute holes. In addition, due to the pressure difference between the suction ring surface and the inside of the casing, the air flow is ejected from the minute holes,
This jet separates the laminar boundary layer on the surface of the suction ring, forms a turbulent boundary layer on the surface of the suction ring after the minute holes, and suppresses the occurrence of turbulence of the air flow flowing out from the tip of the suction ring.

[0015]

EXAMPLE A first example according to the present invention will be described below.
This will be described with reference to the drawings. In order to avoid duplication, the same parts as those of the conventional example will be denoted by the same reference numerals and the description thereof will be omitted.

1 and 2 show the structure of a centrifugal fan according to an embodiment of the present invention.

In the figure, reference numeral 8 is a suction ring, and a minute projection 9 is provided in a ring shape on the surface of the inflow portion of the suction ring 8 concentrically with the center of the suction ring 8. The height h of the protrusion 9 is set smaller than the thickness of the laminar boundary layer formed on the surface of the suction ring.

The operation of the centrifugal blower configured as above will be described below.

First, the impeller 1 is driven by the driving force of the motor 5.
When is rotated, air is introduced into the impeller 1 via the suction ring 8 and static pressure and dynamic pressure are added when passing between the impeller plates 2 and discharged from the impeller 1 into the casing 6. After that, a part of the dynamic pressure in the casing 6 is converted into static pressure and is discharged to the outside of the casing 6 to perform an air blowing action.

FIG. 3 is a schematic diagram showing the flow around the suction ring 8 when the operating point air volume of the centrifugal blower is large. The airflow I flowing into the impeller 1 via the suction ring 8 forms a thick laminar boundary layer on the surface of the suction ring 8, but when the airflow in the laminar boundary layer flows over the projections 9, the suction ring 8
Peel off minutely from the surface. The flow once separated from the suction ring surface forms a turbulent boundary layer on the surface of the suction ring 8 after the projection 9. The turbulent boundary layer has a property that the difference between the flow velocity near the wall surface and the flow velocity of the main flow outside the boundary layer is smaller than that of the laminar boundary layer. Therefore, when the air flow near the tip of the suction ring 8 Moreover, the shear stress due to the velocity difference of the air flow is suppressed to a small level, and the turbulence of the air flow due to the shear stress is suppressed. Further, since the turbulence of the air flow flowing out from the tip of the suction ring 8 is small, when it joins the air flow J flowing back from the inside of the casing 6 into the impeller 1 through the inner surface of the suction ring 8,
The airflow J once attached to the wall surface of the side plate 4 is allowed to flow out to the outlet of the impeller 1 without being separated. Moreover, since the height h of the protrusion 9 is set to be smaller than the thickness of the laminar boundary layer formed on the surface of the suction ring 8, the main flow portion of the air flow flowing from the suction ring 8 into the impeller 1 flows. Not a resistance,
Even if the air volume is small, the efficiency of the air flow into the impeller 1 is not impaired. Therefore, the turbulence of the flow in the vicinity of the side plate 4 of the impeller 1 is reduced without impairing the blowing performance, and the turbulent noise can be reduced.

As described above, the centrifugal blower of this embodiment is
On the surface of the inflow portion of the suction ring 8, a minute projection 9 is provided in a ring shape concentrically with the center of the suction ring 8, and the height h of the projection 9 is smaller than the thickness of the laminar boundary layer formed on the surface of the suction ring. By setting, when the flow in the laminar flow boundary layer formed on the surface of the suction ring 8 passes over the projection 9 and passes through, the laminar flow boundary layer on the surface of the suction ring 8 is separated, and the suction ring after the projection 9 is separated. By forming a turbulent boundary layer on the surface of the suction ring 8 and reducing the difference in the velocity distribution of the airflow flowing out from the tip of the suction ring 8, the shear stress acting on the airflow can be suppressed to a low level and the occurrence of airflow turbulence can be suppressed. The turbulence of the flow near the side plate 4 of No. 1 can be reduced, and since the efficiency of the inflow of the air flow into the impeller 1 is not impaired, the turbulent noise can be reduced without impairing the blowing performance.

Next, a second embodiment of the centrifugal blower according to the present invention will be described with reference to the drawings.

FIG. 4 shows the structure of a centrifugal fan according to the second embodiment of the present invention. The difference from the first embodiment is that a plurality of minute projection plates 11 having a height smaller than the thickness of the laminar boundary layer are provided concentrically with the center of the suction ring 10 on the surface of the inflow portion of the suction ring 10. 11 is installed at a predetermined angle θ with respect to the rotation direction of the impeller.

The operation of the centrifugal blower configured as described above will be described below. The airflow K flowing into the impeller 1 via the suction ring 10 forms a laminar boundary layer on the surface of the suction ring 10. When the airflow in the formed laminar boundary layer passes over the projection plate 11, a slight separation is generated from the surface of the suction ring 10, and the suction ring 10 after the projection plate 11 is generated.
A turbulent boundary layer is formed on the surface to reduce the velocity difference of the airflow that has flowed out from the vicinity of the suction ring tip 10b.
Therefore, the shear stress due to the velocity difference of the airflow is suppressed to be small, and the turbulence of the airflow due to the shear stress is suppressed. Further, since the turbulence of the airflow flowing out from the suction ring tip 10b is suppressed to a small level, even when the airflow L recirculating from the inside of the casing 6 into the impeller 1 through the inner surface of the suction ring 10 is joined, the side plate is once provided. 4 The airflow L adhering to the wall surface is discharged to the outlet of the impeller 1 without being separated. Moreover, the suction ring 1
When the air flow on the 0 surface flows over the projection plate 11, the projection plate 11 is inclined in the rotation direction of the impeller 1, so that the air flow component in the rotation direction of the impeller 1 is added to the air flow L.
Therefore, since the airflow component in the rotational direction has already been added to the airflow flowing into the impeller 1, the total pressure at the outlet of the impeller 1 is increased and the air blowing performance is improved.

As described above, in the centrifugal blower of the present embodiment, a plurality of minute projection plates 11 which are concentric with the center of the suction ring 10 and have a height smaller than the thickness of the laminar boundary layer on the surface of the suction ring 10 are provided. By installing the projection plate 11 at a predetermined angle θ with respect to the rotation direction of the impeller,
When the air flow in the laminar flow boundary layer formed on the surface of the suction ring crosses the projection plate 11, a slight separation is generated from the surface of the suction ring 10, and a turbulent boundary layer is formed on the surface of the suction ring 10 after the projection plate 11. However, it is possible to suppress the velocity difference of the airflows flowing out from the vicinity of the suction ring tip 10b to suppress the occurrence of the airflow turbulence due to the shear stress due to the velocity difference, and reduce the turbulence of the flow near the side plate 4 of the impeller 1. It is possible to reduce the generation of turbulent noise due to the turbulence of the air flow. Moreover, since the airflow component in the rotating direction of the impeller 1 is added to the inflow airflow to the impeller 1, the total pressure at the exit of the impeller 1 is increased, and the air blowing performance can be improved.

Next, a third embodiment of the centrifugal blower according to the present invention will be described with reference to the drawings.

FIG. 4 shows the structure of a centrifugal fan according to the third embodiment of the present invention. The difference from the first and second embodiments is that the suction ring 1 is provided at the inflow portion of the suction ring 12.
The point is that a plurality of communication holes 13 are provided concentrically with the center of 2.

The operation of the centrifugal blower configured as described above will be described below. The airflow M flowing into the impeller 1 via the suction ring 12 forms a laminar boundary layer on the surface of the suction ring 12 and flows toward the tip 12b of the suction ring 12. In addition, the communication hole 1 provided in the suction ring 12
In the vicinity of 3, the air flow N is ejected from the communication hole 13 due to the pressure difference between the surface of the suction ring 12 and the inside of the casing 6, so this jet flow separates the laminar boundary layer on the surface of the suction ring 12,
A turbulent flow boundary layer is formed on the surface of the suction ring 12 after the communication hole 13 to reduce the velocity difference of the airflow flowing out from the vicinity of the suction ring tip 12b. Therefore, the shear stress due to the velocity difference of the airflow is suppressed to be small, and the turbulence of the airflow due to the shear stress is suppressed. Further, since the turbulence of the air flow that flows out from the suction ring tip 12b is suppressed to a small level, even when the air flow O that flows back from the inside of the casing 6 into the impeller 1 through the inner surface of the suction ring 12 is joined, the side plate is once provided. 4 The airflow O attached to the wall surface is allowed to flow to the outlet of the impeller 1 without being separated.
Moreover, the communication hole 13 may have a minute diameter enough to generate a jet flow to the extent that the flow in the laminar boundary layer on the surface of the suction ring 12 is once separated, and the amount of air flow flowing from the communication hole 13 is very small. It does not deteriorate the blowing performance.

As described above, in the centrifugal blower of this embodiment, a layer formed on the surface of the suction ring 12 is formed by providing a plurality of communication holes 13 concentrically with the center of the suction ring 12 at the inflow portion of the suction ring 12. The air flow in the flow boundary layer
Of the suction ring 12 due to the action of the air flow ejected from the communication hole 13 to form a turbulent boundary layer on the surface of the suction ring 12 after the communication hole 13 from the vicinity of the suction ring tip 12b. It is possible to suppress the velocity difference of the outflowing airflows to a small extent to suppress the occurrence of airflow turbulence due to shear stress due to the velocity difference, reduce the turbulence of the flow in the vicinity of the side plate 4 of the impeller 1, and reduce the turbulence of the airflows. Generation of flow noise can be reduced. Moreover, since the amount of the air flow that flows back from the communication hole 13 is very small, there is no fear of degrading the blowing performance.

[0030]

As described above, the present invention has the impeller including the main plate, the plurality of vanes, and the side plate having the suction port, and the suction ring inserted into the suction port of the side plate. Minimize the difference in the velocity distribution of the airflow flowing out from the tip of the suction ring by providing a minute projection that is concentric with the center of the suction ring and has a height smaller than the thickness of the laminar boundary layer. The shear stress acting on the air flow can be suppressed to a small level, the occurrence of air flow turbulence can be suppressed, the flow turbulence near the side plate of the impeller can be reduced, and the inflow efficiency of the air flow to the impeller is not impaired. Therefore, turbulent noise can be reduced without impairing the blowing performance.

Further, a plurality of minute projecting plates concentric with the center of the suction ring and having a height smaller than the thickness of the laminar boundary layer are provided on the surface of the inflow portion of the suction ring, and the projecting plates are arranged in the rotating direction of the impeller. By providing the configuration installed at an angle, it is possible to reduce the velocity difference of the air flow flowing out from the vicinity of the suction ring tip, suppress the occurrence of air flow turbulence due to shear stress due to the velocity difference, and close the side plate of the impeller. The turbulence of the flow can be reduced, and the generation of turbulent noise caused by the turbulence of the airflow can be reduced. Moreover, since the airflow component in the rotating direction of the impeller is added to the inflow airflow to the impeller, the total pressure at the impeller exit can be increased, and the air blowing performance can be improved.

Further, by providing a plurality of communication hole holes concentrically with the center of the suction ring at the inflow portion of the suction ring, the velocity difference of the airflow flowing out from the vicinity of the tip of the suction ring can be suppressed and the shear stress caused by the velocity difference can be reduced. It is possible to suppress the occurrence of airflow turbulence due to the above, reduce the flow turbulence near the side plate, and reduce the occurrence of turbulent noise due to the airflow turbulence. Moreover, since the amount of the air flow that flows back from the communication hole is very small, there is no concern that the blowing performance will be deteriorated.

[Brief description of drawings]

FIG. 1 is a sectional view of a centrifugal fan according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the centrifugal fan according to the embodiment.

FIG. 3 is a schematic diagram showing a flow in the vicinity of a side plate of the centrifugal blower of the embodiment.

FIG. 4 is a perspective view of a main part of a centrifugal fan according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram showing a flow in the vicinity of a side plate of the centrifugal blower of the embodiment.

FIG. 6 is a perspective view of a main part of a centrifugal blower according to a third embodiment of the present invention.

FIG. 7 is a schematic diagram showing a flow near a side plate of the centrifugal blower of the embodiment.

FIG. 8 is a cross-sectional view of a conventional centrifugal blower.

FIG. 9 is a schematic diagram showing a flow in the vicinity of a side plate of a conventional centrifugal blower under a small air volume condition.

FIG. 10 is a schematic diagram showing a flow near a side plate under a large air volume condition of a conventional centrifugal blower.

[Explanation of symbols]

 1 Impeller 2 Blade Plate 3 Main Plate 4 Side Plate 8 Suction Ring 9 Protrusion 10 Suction Ring 11 Protrusion Plate 12 Suction Ring 13 Communication Hole

Claims (3)

[Claims] 1. An impeller having a main plate, a plurality of vanes, and a side plate having a suction port, and a suction ring inserted into the suction port of the side plate, and a concentric circle with the center of the suction ring on the inflow surface of the suction ring. Centrifugal blower with a small protrusion whose height is smaller than the thickness of the laminar boundary layer. 2. An impeller comprising a main plate, a plurality of vanes, and a side plate having a suction port, and a suction ring inserted into the suction port of the side plate, and a concentric circle with the center of the suction ring on the inflow surface of the suction ring. A centrifugal blower in which a plurality of minute projecting plates having a height smaller than that of a laminar flow boundary layer are provided, and the projecting plates are installed to be inclined with respect to the rotation direction of the impeller. 3. An impeller having a main plate, a plurality of vanes, and a side plate having a suction port, and a suction ring inserted into the suction port of the side plate, and concentric with the center of the suction ring at the inflow portion of the suction ring. Centrifugal blower with multiple communication holes.