AXIAL BLOWER
An axial blower includes a rotating blade assembly including a plurality of blades, a motor that rotates the rotating blade assembly to generate an airflow, and a bell mouth that is a frame surrounding the rotating blade assembly from a direction perpendicular to the rotation axis of the rotating blade assembly, wherein the bell mouth has an inlet curved surface on an upstream side of the airflow, the inlet curved surface becomes narrower toward a downstream side of the airflow in the axial direction of the rotation axis, and R1/D≤0.05 is satisfied where D represents the outer diameter of the rotating blade assembly, and R1 represents the radius of curvature of the inlet curved surface.
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The present invention relates to an axial blower that generates an airflow that flows in the axial direction of a rotation axis.
BACKGROUNDAxial blowers are often installed at places close to living spaces, and there have thus been demands for lowering noise thereof. For achieving lower noise of an axial blower, inclining blades of a rotating blade assembly toward the upstream side of an airflow, and bending outer peripheries of blades of a rotating blade assembly toward the upstream side of an airflow have been proposed.
Bell mouths are formed around rotating blade assemblies of axial blowers, so that air is smoothly sucked into the rotating blade assemblies. The shape of the bell mouths affects the air blowing performance and the noise characteristics of the axial blowers. Thus, as described in Patent Literature 1, there have been attempts to enhance the air blowing performance and the quietness of axial blowers by devising the shapes of bell mouths.
CITATION LIST Patent LiteraturePatent Literature 1: Japanese Patent Application Laid-open No. 2002-257096
SUMMARY Technical ProblemThe air blowing performance and the noise characteristics of an axial blower are significantly affected not only by the shape of a rotating blade assembly but also the shape of a bell mouth, and the shape of the rotating blade assembly and the shape of the bell mouth are therefore designed to satisfy a required air blowing performance and required noise characteristics. When the rotating blade assembly and the bell mouth are individually designed, however, the shapes thereof may not be necessarily ideal for the air blowing performance and the noise characteristics owing to dimensional constraints.
The present invention has been made in view of the above, and an object thereof is to provide an axial blower with improved air blowing performance and noise characteristics based on the shape of a bell mouth and the shape of a rotating blade assembly.
Solution to ProblemTo solve the above problems and achieve the object, an axial blower according to the present invention includes: a rotating blade assembly including a plurality of blades; a motor to rotate the rotating blade assembly to generate an airflow; and a bell mouth being a frame surrounding the rotating blade assembly from a direction perpendicular to a rotation axis of the rotating blade assembly. The bell mouth has an inlet curved surface on an upstream side of the airflow, the inlet curved surface becoming narrower toward a downstream side of the airflow in an axial direction of the rotation axis, and R1/D≤0.05 is satisfied where D represents an outer diameter of the rotating blade assembly, and R1 represents a radius of curvature of the inlet curved surface.
Advantageous Effects of InventionAn axial blower according to the present invention produces effects of improving air blowing performance and noise characteristics based on the shape of a bell mouth and the shape of a rotating blade assembly.
An axial blower according to an embodiment of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiment.
EmbodimentA blade 1a has a three-dimensional shape. The blade 1a is radially attached to the outer circumference of the boss 2. The boss 2 is driven to rotate about a rotation axis AX by a motor 3. The blade 1a rotates with the boss 2 in the direction of an arrow S, to generate an airflow flowing in the direction of an arrow A.
The rotating blade assembly 1 is positioned at the center of a blower main unit 6 that includes the bell mouth 5. The blower main unit 6 is a frame having a square outer shape in front view. The motor 3 is positioned downstream of the bell mouth 5 in the airflow direction. Alternatively, the motor 3 may be positioned upstream of the bell mouth 5 in the airflow direction.
When the length of a side of the outer shape of the blower main unit 6 in front view is represented by L, the outer diameter of the rotating blade assembly 1 is represented by D, and the outer diameter of the inlet curved surface 51 of the bell mouth 5 is represented by DR1, the axial blower 10 is designed to satisfy DR1<L in view of easiness of installation and manufacturing cost. The inlet curved surface 51 is formed to be as large as possible within the length L of one side of the outer shape of the blower main unit 6 in front view, so that the airflow is smoothly guided into the rotating blade assembly 1.
The rotating blade assembly 1 of the axial blower 10 according to the embodiment has an outer diameter D of 260 mm. An outer trailing edge I of the rotating blade assembly 1 is located near the boundary between the straight portion 53 and the outlet curved surface 52 of the bell mouth 5. In addition, a blade leading edge 1b and a blade outer edge 1d of the rotating blade assembly 1 project toward the upstream side of the airflow relative to the inlet curved surface 51 of the bell mouth 5.
Because the blade leading edge 1b and the blade outer edge 1d of the rotating blade assembly 1 project toward the upstream side of the airflow relative to the inlet curved surface 51 of the bell mouth 5, air flows into the rotating blade assembly 1 not only via the blade leading edge 1b but also via the blade outer edge 1d. This increases the cross-sectional area of the flow passage of air flowing into the rotating blade assembly 1, and thus lowers the velocity of the airflow into the rotating blade assembly 1. The decrease in the velocity of the airflow reduces turbulence of the airflow and achieves lower noise.
The straight portion 53 prevents air from flowing backward when static pressure is applied.
The outlet curved surface 52 allows a flow in the centrifugal direction included in the airflow flowing out from the rotating blade assembly 1 to smoothly flow out of the rotating blade assembly 1. In addition, the outlet curved surface 52 also serves as a diffuser that increases the static pressure.
In the axial blower 10 according to the embodiment, the outer diameter D of the rotating blade assembly 1 and the radius of curvature R1 of the inlet curved surface 51 of the bell mouth 5 satisfy the following relation: R1/D≤0.05. In addition, when a difference between the outer diameter DR1′ of the inlet curved surface 51 of the bell mouth 5 when the inlet curved surface 51 is extended so that a tangential line TL at an upstream end 51a of the inlet curved surface 51 of the bell mouth 5 is perpendicular to the rotation axis AX and the outer diameter DR1 of the inlet curved surface 51 of the bell mouth 5 is represented by R1′, the following relation is satisfied: 0<R1′/R1≤0.505.
The inlet curved surface 51 of the bell mouth 5 of the axial blower 10 according to the embodiment can be assumed to have such a shape that a part corresponding to a length R1′ is removed from the outer circumference of the inlet curved surface 51′ having the outer diameter DR1′, and to have the outer diameter DR1. In other words, in the axial blower 10 according to the embodiment, it can be assumed that the part having the length R1′ is removed from the outer circumference of the inlet curved surface 51′ having the outer diameter DR1′, so that the inlet curved surface 51 of the bell mouth 5 has the outer diameter DR1. Hereinafter, the part assumed to be removed from the inlet curved surface 51′ having the outer diameter DR1′ will be referred to as a cut part. In addition, the length of the cut part will be referred to as a cut length. Thus, in the embodiment, the cut length is R1′.
When the cut part includes a portion ΔL sticking out from one side of the outer shape of the blower main unit 6 in front view, the outer diameter DR1 of the inlet curved surface 51 of the bell mouth 5 is smaller than the length L of one side of the blower main unit 6. When 0<R1′/R1≤0.505 is satisfied as described above, the radius of curvature R1 of the inlet curved surface 51 of the bell mouth 5 is increased, and the bell mouth 5 can be made smaller than the outer shape of the blower main unit 6 in front view.
As illustrated in
When the rotating blade assembly 1 rotates, a blade tip vortex 7 is generated by a pressure difference between the pressure surface and the negative pressure surface of the blade 1a. When the blade tip vortex 7 interferes with: the negative pressure surface of the blade 1a; another adjacent blade 1a; or the bell mouth 5, the noise characteristics of the axial blower 10 lower. Because the blade 1a has an S-shaped blade cross section convex to the upstream side of the airflow on the inner side and convex to the downstream side of the airflow on the outer side, generation of the blade tip vortex 7 is reduced, and the flow with an increased pressure is prevented from leaking out of the rotating blade assembly 1.
It can be seen in
It can be seen in
In the axial blower 10 according to the embodiment, the ratio of the radius of curvature R1 of the inlet curved surface 51 of the bell mouth 5 to the outer diameter D of the rotating blade assembly 1 satisfies R1/D≤0.05, which controls increase of noise by turbulence of the airflow generated by the inlet curved surface 51 of the bell mouth 5 and sucked into rotating blade assembly 1. In addition, the outer diameter of the inlet curved surface 51 of the bell mouth 5 is equal to or smaller than the length of a side of the blower main unit 6, which prevents the equipment size from increasing. In addition, because the outer diameter of the inlet curved surface 51 of the bell mouth 5 is equal to or smaller than the length of a side of the blower main unit 6, the need for mounting a bell mouth 5 that is a component separate from a blower main unit 6 onto the blower main unit 6 is eliminated, and an increase in man-hours is thus prevented.
The configurations presented in the embodiment above are examples of the present invention, and can be combined with other known technologies or can be partly omitted or modified without departing from the scope of the present invention.
REFERENCE SIGNS LIST1 rotating blade assembly; 1a blade; 1b blade leading edge; 1c blade tailing edge; 1d blade outer edge; 1e blade inner edge; 2 boss; 3 motor; 5 bell mouth; 6 blower main unit; 7 blade tip vortex; 9 lateral flow; 10 axial blower; 51, 51′ inlet curved surface; 51a upstream end; 52 outlet curved surface.
Claims
1. An axial blower comprising:
- a rotating blade assembly including a plurality of blades;
- a motor to rotate the rotating blade assembly to generate an airflow; and
- a bell mouth being a frame surrounding the rotating blade assembly from a direction perpendicular to a rotation axis of the rotating blade assembly, wherein
- the bell mouth has an inlet curved surface on an upstream side of the airflow, the inlet curved surface becoming narrower toward a downstream side of the airflow in an axial direction of the rotation axis, and
- 0<R1′/R1≤0.505 is satisfied where R1 represents a radius of curvature of the inlet curved surface and R1′ represents a difference between an outer diameter of the inlet curved surface and a length obtained by doubling a distance between a position at which a tangential line at an upstream end of the inlet curved surface is perpendicular to the rotation axis and to which the inlet curved surface is extended and the rotation axis.
2. The axial blower according to claim 1, wherein R1/D≤0.05 is satisfied where D represents an outer diameter of the rotating blade assembly.
3. The axial blower according to claim 1, wherein a blade cross section of each blade at a plane along a radial direction including the rotation axis is inclined toward an upstream side of the airflow at a blade leading edge located at a front position in a rotating direction, and an inclination angle continuously changes in such a manner that the blade cross section is more inclined toward a downstream side of the airflow as the blade is closer to a blade tailing edge located at a back position in the rotating direction.
4. The axial blower according to claim 1, wherein
- each blade has an inflection point located between an outer side and an inner side, the inflection point being a point at which a direction to which a blade cross section is convex changes, and
- the blade cross section of the blade is convex to an upstream side of the airflow on an inner side of the inflection point, and convex to a downstream side of the airflow on an outer side of the inflection point.
5. The axial blower according to claim 4, wherein
- a radius of curvature of the blade on the outer side of the inflection point gradually decreases from a blade leading edge toward a blade tailing edge, reaches a minimum value, and then gradually increases, and
- a radius of curvature of the blade on the inner side of the inflection point gradually decreases from the blade leading edge toward the blade tailing edge.
6. The axial blower according to claim 2, wherein a blade cross section of each blade at a plane along a radial direction including the rotation axis is inclined toward an upstream side of the airflow at a blade leading edge located at a front position in a rotating direction, and an inclination angle continuously changes in such a manner that the blade cross section is more inclined toward a downstream side of the airflow as the blade is closer to a blade tailing edge located at a back position in the rotating direction.
7. The axial blower according to claim 2, wherein
- each blade has an inflection point located between an outer side and an inner side, the inflection point being a point at which a direction to which a blade cross section is convex changes, and
- the blade cross section of the blade is convex to an upstream side of the airflow on an inner side of the inflection point, and convex to a downstream side of the airflow on an outer side of the inflection point.
8. The axial blower according to claim 3, wherein
- each blade has an inflection point located between an outer side and an inner side, the inflection point being a point at which a direction to which a blade cross section is convex changes, and
- the blade cross section of the blade is convex to an upstream side of the airflow on an inner side of the inflection point, and convex to a downstream side of the airflow on an outer side of the inflection point.
9. The axial blower according to claim 6, wherein
- each blade has an inflection point located between an outer side and an inner side, the inflection point being a point at which a direction to which a blade cross section is convex changes, and
- the blade cross section of the blade is convex to an upstream side of the airflow on an inner side of the inflection point, and convex to a downstream side of the airflow on an outer side of the inflection point.
10. The axial blower according to claim 7, wherein
- a radius of curvature of the blade on the outer side of the inflection point gradually decreases from a blade leading edge toward a blade tailing edge, reaches a minimum value, and then gradually increases, and
- a radius of curvature of the blade on the inner side of the inflection point gradually decreases from the blade leading edge toward the blade tailing edge.
11. The axial blower according to claim 8, wherein
- a radius of curvature of the blade on the outer side of the inflection point gradually decreases from a blade leading edge toward a blade tailing edge, reaches a minimum value, and then gradually increases, and
- a radius of curvature of the blade on the inner side of the inflection point gradually decreases from the blade leading edge toward the blade tailing edge.
12. The axial blower according to claim 9, wherein
- a radius of curvature of the blade on the outer side of the inflection point gradually decreases from a blade leading edge toward a blade tailing edge, reaches a minimum value, and then gradually increases, and
- a radius of curvature of the blade on the inner side of the inflection point gradually decreases from the blade leading edge toward the blade tailing edge.
Type: Application
Filed: Feb 2, 2018
Publication Date: Dec 31, 2020
Applicant: Mitsubishi Electric Corporation (Chiyoda-ku, Tokyo)
Inventors: Toshikatsu ARAI (Tokyo), Hitoshi KIKUCHI (Tokyo), Chikage KADOI (Tokyo)
Application Number: 16/962,594