Propeller Fan and Air Conditioner Equipped with the Same
In order to suppress that a velocity in the vicinity of a bell mouth is lowered to induce non-uniformity in velocity at an outlet of a blade and an outlet of the bell mouth caused by adoption of a forward-swept blade which makes a tip vortex small as means for noise reduction, in a blade of a propeller fan, a trailing edge portion which has been rotationally projected on a plane passing through a rotational axis is formed from the rotational axis toward a blade tip portion so as to bend from the suction side to the discharge side with a first curvature, and is further formed so as to bend with a second curvature which is smaller than the aforementioned first curvature with an inflection point interposed.
The present invention relates to a propeller fan and an air conditioner equipped with same.
BACKGROUND ARTThe propeller fan is applied to the air conditioner and so forth in many cases.
As the background art of the present technical field, there is Japanese Examined Patent Publication No. Hei2-2000 (Patent Literature 1). In Patent Literature 1, it is described that air flow rate enlargement, static pressure heightening and noise reduction can be made by numerically limiting shape parameters such as a degree of sweep of the blade and an inclination of the blade, a camber of the blade section and so forth of the above-mentioned forward-swept blade.
In addition, there is Japanese Patent No. 3744489 (Patent Literature 2). In Patent Literature 2, it is described that the noise can be reduced by making the tip vortex small by curling an outer peripheral end part of the blade toward the suction side. Further, it is also described that the noise can be reduced by suppressing interaction between an air flow and the bell mouth by defining a positional relation between such blade and bell mouth.
Further, there is Japanese Patent No. 4818184 (Patent Literature 3). In Patent Literature 3, it is described that the tip vortex is migrated into a blade tip part by warping the blade toward the suction side by a definition method different from that in Patent Literature 2 so as to prevent interaction between the tip vortex and the bell mouth and thereby noise reduction surd efficiency heightening can be made.
CITATION LIST Patent LiteraturePTL 1: Japanese Examined Patent Application Publication No. Hei2-2000
PTL 2: Japanese Patent No. 3744489
PTL 3: Japanese Patent No. 4818184
SUMMARY OF INVENTION Technical ProblemIn an embodiment, force that a blade acts on a flow will be referred to as “blade force”. The blade force that the blade acts on the flow is shown by an arrow A′ in
A schematic diagram of a velocity vector which has been projected on a section passing through a rotational axis 6 in the conventional propeller fan is shown in
Accordingly, the present invention aims to promote heightening of the efficiency of the propeller fan.
Solution to ProblemIn order to solve the above-mentioned problem, configurations, for example, described in Claims are adopted.
Although the present application includes a plurality of means for solving the above-mentioned problem, when one example thereof is given, a propeller fan includes a rotational axis serving as a center of rotation and a plurality of blades provided around the rotational axis, a bell mouth being arranged outside in an outer radial direction of the plurality of blades, wherein each of the plurality of blades is formed by a trailing edge portion formed on the rear relative to a rotation direction, a leading edge portion formed on the front relative to the rotation direction, a blade tip portion formed from a tip portion in an outer radial direction of the trailing edge portion toward a tip portion in an outer radial direction of the leading edge portion, the aforementioned trailing edge portion which has been rotationally projected on a plane passing through the aforementioned rotational axis is formed from the aforementioned rotational axis toward the aforementioned blade tip portion so as to bend from the suction side to the discharge side with a first curvature, and is further formed so as to bend with a second curvature which is smaller than the aforementioned first curvature with an inflection point interposed.
In addition, in the above-mentioned configuration, it is desirable that on end face of the aforementioned bell mouth which is closest to the aforementioned blade, a position which is an end portion in a discharge direction and where an angle is changed in an outer radial direction almost match a position of the aforementioned inflection point, viewing from above a rotation plane.
In addition, in the above-mentioned configuration, it is desirable that the aforementioned trailing edge portion which has been rotationally projected on a plane vertical to the aforementioned rotational axis be formed to be convex in a reverse rotation direction from the aforementioned rotational axis toward the aforementioned blade tip portion, and be formed linearly or to be convex in the rotation direction with the inflection point interposed.
In addition, in the above-mentioned configuration, it is desirable that, each of the aforementioned plurality of blades is, a blade force act on a portion formed with the aforementioned first curvature in the aforementioned trailing edge portion so as to direct in an outer radial direction relative to a direction of the aforementioned rotational axis and a blade force act on a portion formed with the aforementioned second curvature in the aforementioned trailing edge portion so as to direct in an inner radial direction relative to the direction of the aforementioned rotational axis.
In addition, in the above-mentioned configuration, it is desirable to include a guard which lets air pass toward the discharge side of the aforementioned blade, prevents mixing of a foreign material which exceeds a predetermined size and is apart from the propeller with a distance exceeding a predetermined length.
Further, it is desirable that, in an air conditioner which includes a housing having a suction port and a discharge port of air, a heat exchanger arranged in the housing and a fan which is arranged upstream or downstream of the heat exchanger and sucks air on the outside of the housing through the aforementioned suction port and discharges it through the aforementioned discharge port, the propeller fan described in any of the above-mentioned configurations be used as the fan.
Advantageous Effects of InventionAccording to the present invention, efficiency heightening of the propeller fan can be implemented.
In the following, embodiments of the present invention will be described using the drawings.
Embodiment 1An embodiment 1 of the present invention will be described using
In
Since the blade 1 of the propeller fan of the present embodiment is of the above-mentioned configuration, the blade force A acts so as to direct in an outer radial direction relative to a direction of the rotational axis 6. Therefore, a flow in the vicinity of the trailing edge portion 3b comes to obtain a momentum which would partially direct in the outer radial direction relative to the direction of the rotational axis 6. On the other hand, the blade force A′ of the conventional propeller fan acts so as to direct in an inner radial direction relative to the direction of the rotational axis 6. Therefore, a flow between blades obtains a momentum which world direct in the inner radial direction relative to the direction of the rotational axis 6.
A schematic diagram of the velocity vector which has been projected on the section passing through the rotational axis in a conventional propeller fan is shown in
A schematic diagram of a velocity vector which has been projected on a section passing through the rotational axis in the propeller fan of the embodiment 1 is shown in
Consequently, while, conventionally, the flow has stagnated just like the flow U not being supplied to the vicinity of the bell mouth as shown in
In the present embodiment, an embodiment which can make the embodiment 1 more highly efficient will be described using
That is, on an end face of the bell mouth 8 which is closest to the blade 1, it is made such that the position which is the end portion 10 in a discharge direction and where the angle is changed to the outer radial direction almost matches the position of the inflection point 7, viewing from above the rotation plane. Thereby, on the end face of the bell mouth 8 which is closest to the blade 1, the position which is the end portion 10 in the discharge direction and where the angle is changed to the outer radial direction almost matches a position serving as a boundary between a portion to which the outward blade force A acts and a portion to which the outward blade force A does not act, viewing from above the rotation plane.
A schematic diagram of a velocity vector which has been projected on a section passing through the rotational axis in the propeller fan of the embodiment 2 is shown in
A result of comparison in shaft power of the propeller fan in the embodiment 2 with the conventional propeller fan is shown in
In the present embodiment, an embodiment which can make the embodiment 1 or the embodiment 2 more highly efficient will be described using
Since the curvature of the trailing edge portion 3t has been changed with the inflection point 18 set as a boundary, the orientation of the blade force C is changed to the outer radial direction relative to the direction of the rotational axis 6 in comparison with the blade force B. Owing to this change in orientation of the blade force, the flow in the vicinity of the trailing edge portion 3t obtains a momentum which directs in the outer radial direction and the flow in the vicinity of the blade tip portion 5 is directed in the outer radial direction. Consequently, the velocity in the vicinity of the blade outlet is made uniform. Since the mixing loss of the blade wake is reduced by velocity uniformity, the efficiency is increased.
Incidentally, although in
In the present embodiment, an embodiment that the effect of noise reduction can be also obtained in addition to efficiency heightening in the embodiments 1 to 3 will be described using
One example of comparison in noise of the propeller fan in the embodiment 3 with the conventional propeller fan is shown in
Incidentally, it is necessary to form the gap in the frame or the net of this guard 11 to be less than a predetermined size such that a finger of an adult does not enter it. Further, it is necessary to make it not to touch a propeller 12 even in a case where a finger of a child has entered the gap in the guard 11. Therefore, further safety can be ensured by setting a distance L from an end portion of the frame or the net of the guard 11 to a position 19 where the trailing edge 3 is closest to the guard 11 so as to exceed a predetermined length. Since it is assumed that the length of the finger of the child is approximately 50 mm, it is desirable to ensure 50 mm or more as the distance L.
Embodiment 5In the present embodiment, an air conditioner using a propeller fan equipped with requirements of any of the embodiments 1 to 4 will be described.
This air conditioner is, after air has been sucked into and cooled or overheated by the heat exchanger 16 by rotating the propeller 12 by the motor 13, it is boosted by the propeller 12 and the bell mouth 8 and thereafter is discharged through the guard 11. Since the propeller fan described in any of the embodiments 1 to 4 is used as the propeller fan and the bell mouth, the noise-reduced and highly efficient air conditioner can be obtained.
Incidentally, although the outdoor unit has been described in the present embodiment, the present invention is a technology which can be commonly used in the ones using the propeller fan regardless of whether the air conditioner is of another type and an indoor unit.
REFERENCE SIGNS LIST1, 1′: blade
2, 2′: hub
3, 3′, 3t, 3h: trailing edge portion
4, 4′: leading edge portion
5, 5′: blade tip portion
6, 6′: center of rotation
7: inflection point
8: bell mouth
9: cylindrical portion
10, 10a, 10b: end portion
11: guard
12: propeller
13: motor
14: motor support table
15: unit
16: heat exchanger
17: compressor
18: inflection point
19: position where the trailing edge 3 is closest to the guard 11 from the end portion of the frame or the net of the guard 11
A, A′: blade force
B: blade force
C: blade force
L: distance
S: flow
T: flow
U: flow
X: air flowing direction
Y: rotation direction
A: first curvature
B: second curvature
Claims
1. A propeller fan, comprising:
- a rotational axis serving as a center of rotation; and
- a plurality of blades provided around the rotational axis,
- a bell mouth being arranged outside in an outer radial direction of the plurality of blades, wherein
- each of the plurality of blades is formed by
- a trailing edge portion formed on the rear relative to a rotation direction, a leading edge portion formed on the front relative to the rotation direction, a blade tip portion formed from a tip portion in an outer radial direction of the trailing edge portion toward a tip portion in an outer radial direction of the leading edge portion,
- the trailing edge portion which has been rotationally projected on a plane passing through the rotational axis is formed from the rotational axis toward the blade tip portion so as to bend from the suction side to the discharge side with a first curvature, and further is formed so as to bend with a second curvature which is smaller than the first curvature with an inflection point interposed.
2. The propeller fan according to claim 1, wherein
- on an end face of the bell mouth which is closest to the blade, a position which is an end portion in a discharge direction and where an angle is changed in an outer radial direction almost matches a position of the inflection point, viewing from above a rotation plane.
3. The propeller fan according to claim 1, wherein
- the trailing edge portion which has been rotationally projected on a plane vertical to the rotational axis is formed to be convex in a reverse rotation direction from the rotational axis toward the blade tip portion, and is formed linearly or to be convex in the rotation direction with the inflection point interposed.
4. The propeller fan according to claim 1, wherein
- each of the plurality of blades is,
- a blade force acts on a part formed with the first curvature in the trailing edge portion so as to direct in an outer radial direction relative to a direction of the rotational axis and a blade force acts on a part formed with the second curvature in the trailing edge portion so as to direct in an inner radial direction relative to the direction of the rotational axis.
5. The propeller fan according to claim 1, comprising:
- a guard which lets air pass toward the discharge side of the blade, prevents mixing of a foreign material which exceeds a predetermined size and is apart from the propeller with a distance exceeding a predetermined length.
6. An air conditioner, comprising:
- a housing having a suction port and a discharge port of air;
- a heat exchanger arranged in the housing; and
- a fan which is arranged upstream or downstream of the heat exchanger and sucks air on the outside of the housing through the suction port and discharges the air through the discharge port, wherein
- the propeller fan according to claim 1 has been used as the fan.
Type: Application
Filed: Feb 22, 2013
Publication Date: Jan 7, 2016
Inventors: Taku IWASE (Tokyo), Tetsushi KISHITANI (Tokyo), Atsuhiko FUKASAWA (Tokyo)
Application Number: 14/768,927