JP2008051074A - Propeller fan - Google Patents

Abstract

A propeller fan capable of suppressing noise by suppressing growth of a blade tip vortex and a boundary layer.
In a propeller fan in which at least one blade (12) curved so as to protrude toward the negative pressure side is provided on a hub, the blade (12) excludes a trailing edge (12B) in the rotational direction of the blade (12). A curved surface portion 13 that is convex toward the positive pressure side is formed in the portion, and the curved surface portion 13 is configured to be positioned on the negative pressure side of the chord C of the blade 12.
[Selection] Figure 2

Description

  The present invention relates to a propeller fan that sends a fluid such as air from a negative pressure side to a positive pressure side by rotating a hub provided with a blade curved so as to protrude toward the negative pressure side.

  The aforementioned propeller fan is used, for example, in an outdoor unit of an air conditioner. A conventional general propeller fan includes a blade that is curved to be convex toward the negative pressure side. The pressure is changed from the front side to the rear side in the direction of rotation of the blade to efficiently create a pressure difference between the negative pressure side and the positive pressure side, and the flow of air from the negative pressure side to the positive pressure side is increased. Has been.

However, in the conventional blade, it is known that a so-called blade tip vortex is generated at the outer peripheral end (blade tip) of the blade due to the pressure difference between the positive pressure side and the negative pressure side. Noise is generated when the blade tip vortex collides with a bell mouth that separates the suction side and the blow-out side of other blades and propeller fans.
In addition, a boundary layer is generated between the blade surface and the flow, and this boundary layer gradually develops toward the rear side in the blade rotation direction and peels off from the blade surface. When the boundary layer peels, broadband noise is generated.

As a countermeasure against these noises, a blade with a changed shape has been proposed (for example, Patent Documents 1 to 3).
JP 2003-184792 A Japanese Unexamined Patent Publication No. 7-77198 JP 2004-124748 A

By the way, in the conventional propeller fan, the thing which suppressed the wing tip vortex (patent document 1) or the thing which suppressed the growth of the boundary layer (patent documents 2, 3) is proposed, respectively. No blade shape has been proposed that effectively suppresses both the growth and boundary layer growth simultaneously.
Further, in Patent Documents 2 and 3, since the leading edge of the blade in the rotational direction largely protrudes toward the positive pressure side, the flow of fluid from the front side in the rotational direction is hindered and the fan efficiency decreases. The fan efficiency is the ratio between the amount of fluid transferred by the fan (for example, the air volume) and the power of a motor or the like that rotates the fan. If the rotational speed is increased to ensure the amount of fluid transfer, the noise will be further increased.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a propeller fan capable of suppressing noise by suppressing growth of a blade tip vortex and a boundary layer.

  In order to solve this problem, the propeller fan according to the present invention is a propeller fan in which at least one blade curved so as to be convex toward the negative pressure side is provided in a hub. A deformed surface portion that protrudes toward the pressure side is formed on a portion excluding the trailing edge portion in the rotation direction of the blade, and the deformed surface portion is configured to be positioned on the suction side with respect to the blade chord of the blade. It is characterized by being.

  In the propeller fan having this configuration, the flow of the blade surface (negative pressure surface) on the negative pressure side changes so as to vortex at the curved surface portion. Further, since the blade surface (positive pressure surface) on the positive pressure side flows so as to get over the curved surface portion, the flow velocity increases and the pressure decreases. Thereby, in the curved surface part, the pressure difference between the negative pressure side and the positive pressure side becomes small. Since the blade tip vortex is generated due to a pressure difference between the suction side and the pressure side, the growth of the blade tip vortex is hindered in the curved surface portion.

  Further, on the suction surface, the boundary layer gradually grows from the front side in the rotation direction, but the flow changes at the curved surface portion that protrudes toward the pressure side, so the growth of the boundary layer is interrupted. And a boundary layer grows anew from the rotation direction back of a curved surface part. Further, the boundary layer grows by flowing along the pressure surface from the rear side in the rotation direction of the deformable surface portion also on the pressure surface.

Furthermore, since the deformed surface portion is configured to be positioned on the negative pressure side of the blade chord, the fluid flow from the front in the rotation direction of the blade is not hindered.
In addition, since the curved surface portion is provided in a portion excluding the trailing edge portion in the rotation direction of the blade, the shape of the trailing edge portion in the rotation direction of the blade is designed so as to efficiently generate a pressure difference, thereby improving fan efficiency. Can be maintained.

  ADVANTAGE OF THE INVENTION According to this invention, the growth of a blade tip vortex can be prevented in a curved surface part, and development of a boundary layer can be suppressed, and generation | occurrence | production of a noise can be prevented. Further, since the flow of the blade from the front in the rotational direction is not hindered by the curved surface portion, it is possible to suppress a decrease in fan efficiency and to suppress noise without increasing the rotational speed more than necessary.

The propeller fan according to the first embodiment of the present invention will be described below with reference to the accompanying drawings. This propeller fan constitutes a blower provided in an outdoor unit of the air conditioner.
The propeller fan 10 includes a cylindrical hub 11 that is rotated about a rotation axis L in the rotation direction T, and a plurality (three) of blades 12 provided on the outer periphery of the hub 11. Yes.

As shown in FIG. 1, the outer peripheral end 12 </ b> A (blade tip) of the blade 12 is configured to have an arc shape centered on the rotational axis L as seen from the direction of the rotational axis L.
Further, the rear edge portion 12B of the blade 12 in the rotational direction T is curved so that the central portion in the radial direction protrudes rearward in the rotational direction T when viewed from the direction of the rotational axis L. It is comprised so that it may go to the rotation direction front side, and it is comprised so that the outer peripheral end 12A (blade end) of the braid | blade 12 and an obtuse angle may be crossed.
Further, the front edge portion 12C in the rotational direction T of the blade 12 is curved so that the central portion in the radial direction is recessed toward the rear side in the rotational direction T when viewed from the rotational axis L direction, and rotates as it goes radially outward. It is configured to protrude forward in the direction, and is configured to intersect the outer peripheral end 12A (blade end) of the blade 12 at an acute angle.

  As shown in FIG. 2 when viewed from the outer peripheral side, the blade 12 is curved so as to be convex toward one side (lower side in FIG. 2) as a whole. Thereby, the angle formed between the virtual plane orthogonal to the rotation axis L and the leading edge 12C in the rotational direction T of the blade 12 is smaller than the angle formed between the virtual plane and the trailing edge 12B in the rotational direction T of the blade 12, In FIG. 2, the upper side of the blade 12 is the positive pressure side, and the lower surface of the blade 12 is the negative pressure side. That is, the blade 12 is curved so as to be convex toward the negative pressure side as a whole.

  A curved surface portion 13 that is convex toward the positive pressure side is formed in the central portion of the rotation direction T of the blade 12. The apex of the deformed curved surface portion 13 is configured so as to be positioned on the negative pressure side with respect to a line connecting the rotation direction T front edge portion 12C and the rotation direction T rear edge portion 12B of the blade 12, that is, the so-called chord C.

  The propeller fan 10 configured as described above is rotated in the rotation direction T about the rotation axis L, and a negative pressure difference is generated between the upper side (positive pressure side) and the lower side (negative pressure side) of the blade 12. Air is transferred from the pressure side toward the positive pressure side.

The air flowing in from the front side in the rotation direction T flows along the surface of the blade 12 on the negative pressure side (negative pressure surface 12E) and changes so as to vortex at the curved surface portion 13. In addition, on the surface of the blade 12 on the positive pressure side (positive pressure surface 12F), the flow flows so as to get over the deformed surface portion 13, so that the flow velocity increases and the pressure decreases. As a result, the pressure difference between the negative pressure side and the positive pressure side is reduced in the curved surface portion 13.
The blade tip vortex generated by the pressure difference between the negative pressure side and the positive pressure side is inhibited from growing because the pressure difference becomes smaller at the curved surface portion 13. Further, the blade tip vortex is divided into two in the rotation direction T front side and the rotation direction T rear side of the curved surface portion 13, and the blade tip vortex on the rotation direction T rear side is released in the blowing direction.

  Further, on the suction surface 12E, the boundary layer gradually grows from the front side in the rotation direction T, but the boundary layer growth is interrupted by the flow changing at the curved surface portion 13. Then, the boundary layer grows again from behind the rotation direction T of the curved surface portion 13. Further, the boundary layer grows by flowing along the pressure surface 12F from the rear side in the rotation direction T of the deformable surface portion 13 on the pressure surface 12F.

Furthermore, since the curved surface portion 13 is configured to be located on the negative pressure side of the chord C of the blade 12, the flow of air from the front side in the rotational direction T of the blade 12 is inhibited by the curved surface portion 13. There is nothing to do.
Further, since the curved surface portion 13 is formed at the central portion in the rotational direction T of the blade 12, the blade rotational direction T is formed so that the trailing edge of the blade warps to the positive pressure side so as to efficiently generate a pressure difference. Yes.

In the propeller fan 10 configured as described above, since the growth of the blade tip vortex is inhibited by the curved surface portion 13, noise due to the blade tip vortex can be suppressed.
Further, since the growth of the boundary layer is interrupted by the flow changing at the curved surface portion 13, the boundary layer does not grow greatly, and peeling can be suppressed. In addition, since the boundary layer itself does not grow greatly, the energy at the time of separation is small. Therefore, noise due to separation of the boundary layer can be suppressed.

Furthermore, since the inflow of air from the front side in the rotational direction T of the blade 12 is not hindered by the curved surface portion 13, it is necessary to increase the rotational speed in order to secure the air flow without reducing the fan efficiency. Absent.
Further, the blade tip vortex is divided into two in the rotational direction T front side and the rotational direction T rear side of the curved surface portion 13, and the blade tip vortex on the rear side in the rotational direction T is released in the blowing direction, improving fan efficiency. Can be made.

  Here, the calculation result of the pressure distribution on the suction surface 12E is shown in FIG. Moreover, the calculation result of the pressure distribution in the positive pressure surface 12F is shown in FIG. In the negative pressure surface 12E, it turns out that the space | interval of an isobaric line is not large, and the pressure is not changing in the variable surface part 13. FIG. In the positive pressure surface 12F, the isobaric line 13 is positioned so as to form two peaks with the deformed surface portion 13 as a boundary, and the pressure of the deformable surface portion 13 is lower than the surroundings. Thereby, in the deformed surface part 13, it is confirmed that the pressure difference of the positive pressure surface 12F and the negative pressure surface 12E is small.

Next, the propeller fan 10 which is the 2nd Embodiment of this invention is demonstrated. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and detailed description is abbreviate | omitted.
As in the first embodiment, the propeller fan 10 includes a cylindrical hub 11 that is rotated about the rotation axis L in the rotation direction T, and a plurality (3) provided on the outer peripheral portion of the hub 11. ) Blade 12.

  The blade 12 is curved so as to be convex downward as a whole when viewed from the outer peripheral side, and a deformed curved surface portion 13 that is convex toward the positive pressure side is formed at the central portion in the rotation direction T of the blade 12. ing. As shown in FIG. 6, a flat plate portion 14 having a flat plate shape extending to the outer peripheral end 12 </ b> A (blade tip) of the blade 12 is formed on the front side in the rotational direction T from the curved surface portion 13. The flat plate portion 14 is configured to slightly incline toward the negative pressure side with respect to the chord C. Further, the trailing edge 12B in the rotational direction T of the blade 12 is configured to largely warp.

  As shown in FIG. 6, the curved surface portion 13 is located at the center portion in the rotational direction T of the blade 12 on the outer peripheral side of the blade 12, but as the blade 12 moves toward the inner peripheral side of the blade 12. Twelve rotational directions T are configured to approach the leading edge 12C. Thereby, the rotation direction T length of the flat plate portion 14 provided on the front side in the rotation direction T of the curved surface portion 13 is gradually shortened, and the flat plate portion is formed at the inner peripheral end 12D of the blade 12 as shown in FIG. 14 and the deformed surface portion 13 are not formed, and the airfoil is curved to the negative pressure side.

  According to the second embodiment, since the flat plate portion 14 is formed on the outer peripheral side of the blade 12 where the blade tip vortex is generated, in front of the deformable surface portion 13 in the rotational direction T, the flat plate portion 14 is also provided. The pressure difference between the negative pressure side and the positive pressure side is small, and the growth of the tip vortex is suppressed. Further, since the flow on the surface of the blade 12 does not change in the flat plate portion 14, separation of the boundary layer can be suppressed. Therefore, it is possible to suppress noise due to impingement of the blade tip vortex and separation of the boundary layer. The trailing edge 12B in the rotational direction T of the blade 12 is configured to largely warp, and the pressure difference in this portion is large, leading to a blade tip vortex, or a sudden change in flow that causes separation of the boundary layer. However, since the tip vortex and the boundary layer do not grow greatly, noise due to separation of the tip vortex and the boundary layer can be suppressed.

Further, since the flat plate portion 14 is formed in a flat plate shape extending to the outer peripheral end 12A (blade end) of the blade 12, air can easily flow from not only from the front in the rotation direction T of the blade 12, but also from the outer peripheral side. Efficiency can be greatly improved.
Further, since the trailing edge portion 12B in the rotational direction T of the blade 12 is configured to largely warp, sufficient fan efficiency can be ensured.

  Further, since the position of the curved surface portion 13 gradually changes from the outer peripheral side toward the inner peripheral side, the size of the separation of the boundary layer on the surface of the blade 12 is different, and the separated flow is the rotation of the blade 12. Even when it collides with an obstacle (for example, another blade 12) on the rear side in the direction T, the periodic noise can be reduced.

  In addition, in the inner peripheral portion where the flow rate flowing on the surface of the blade 12 is small, even if the boundary layer grows and peels, the energy is small and noise can be suppressed. Fan efficiency can be improved as an airfoil to be generated.

  Here, the calculation result of the pressure distribution on the suction surface 12E is shown in FIG. Moreover, the calculation result of the pressure distribution in the positive pressure surface 12F is shown in FIG. In the negative pressure surface 12E, the pressure on the outer peripheral side portion of the deformed surface portion 13 is high. Further, on the positive pressure surface 12F, the pressure on the outer peripheral side portion of the deformed surface portion 13 is low. Therefore, in the deformed surface portion 13, it is confirmed that the pressure difference between the positive pressure surface 12F and the negative pressure surface 12E is small particularly on the outer peripheral side.

As mentioned above, although the propeller fan which is embodiment of this invention was demonstrated, this invention is not limited to this, In the range which does not deviate from the technical idea of the invention, it can change suitably.
The device including the propeller fan is not limited to the outdoor unit of the air conditioner, and may be other industrial equipment such as a ventilation fan or a consumer product.

  Furthermore, although the number of blades has been described as three, it is not limited to this, and it is preferable to determine the number and arrangement of blades in consideration of the size of the propeller fan, the set air volume, and the like.

It is a front view of the propeller fan which is the 1st embodiment of the present invention. It is AA sectional drawing in FIG. FIG. 2 is a pressure distribution diagram of a suction surface of the propeller fan shown in FIG. 1. FIG. 2 is a pressure distribution diagram of a pressure surface of the propeller fan shown in FIG. 1. It is a front view of the propeller fan which is the 2nd Embodiment of this invention. It is AA sectional drawing in FIG. It is BB sectional drawing in FIG. It is CC sectional drawing in FIG. It is DD sectional drawing in FIG. FIG. 6 is a pressure distribution diagram of a suction surface of the propeller fan shown in FIG. 5. FIG. 6 is a pressure distribution diagram of a positive pressure surface of the propeller fan shown in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Propeller fan 11 Hub 12 Blade 12E Negative pressure surface 12F Positive pressure surface 13 Curved surface part 14 Flat plate part

Claims (3)

In the propeller fan in which at least one blade curved so as to be convex toward the negative pressure side is provided in the hub,
The blade is formed with a curved surface portion that is convex toward the positive pressure side in a portion excluding the trailing edge portion in the rotational direction of the blade,
The propeller fan, wherein the deformed curved surface portion is configured to be positioned on a negative pressure side of the blade chord of the blade.   2. The propeller fan according to claim 1, wherein a front portion in a rotational direction of the deformed curved surface portion is formed in a flat plate shape.   3. The propeller fan according to claim 1, wherein the deformed curved surface portion is formed so as to gradually approach the front edge portion in the rotational direction as it goes from the outer peripheral side to the inner peripheral side of the blade. .

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