The present invention relates to a structure of an axial flow fan such as a propeller fan or the like.
This kind of axial flow fan is used as an air blower of an outdoor unit for an air conditioner. As shown in
The air blowing unit 3 is provided with a propeller fan 4 serving as an axial flow fan. As shown in
As a problem of the outdoor unit mentioned above, there are a noise generated from the propeller fan 4, and a noise generated by a collision of the air blown off the propeller fan 4 with the fan guard 6 or the like. In order to reduce the noises, for example, there have been conventionally carried out an optimization of a shape of the impeller blade 13 of the propeller fan 4, an employment of an air foil type vane having an excellent aerodynamic performance, and the like.
However, even in the case of employing these means, when the propeller fan 4 is rotated, an air flow (A1) heading for a negative pressure surface 13e having a low pressure from a pressure surface 13d having a high pressure is generated near an outer peripheral edge of each of the impeller blades 13 as shown in
In particular, if the eddy current (A2) interferes with the subsequent impeller blade 13 after separating from the negative pressure surface 13e of each of the impeller blades 13, the turbulence of the air flow becomes further large, which can further increase the noise of the blower.
For example, if the chord length of each of the impeller blades 13 is shortened for weight saving (cost reduction), a blade lattice performance generated by each of the impeller blades 13 is lowered. Accordingly, the eddy current (A2) tends to separate from the negative pressure surface 13e of each of the impeller blades 13. As shown in
In order to cope with the problem mentioned above, as shown in
In accordance with this structure, as shown in
Further, as shown in
Accordingly, even if the chord length of each of the impeller blades 13 is shortened for weight saving, the eddy currents (A2) do not interfere with each other between adjacent impeller blades 13, and the turbulence of the air flow is reduced in the downstream side of the blower. In other words, the noise of the blower can be effectively reduced by incorporating the propeller fan in the outdoor unit for the air conditioner.
However, in the case that the bent portion 13c is provided in the outer peripheral edge of each of the impeller blades 13, there is a problem that a warp of the vane contributing to a pressure rising work of the propeller fan 4 becomes small, and the blowing performance of the blower is lowered.
Accordingly, it is necessary to prevent the width d of the bent portion 13c from becoming too large. Conventionally, the maximum value of the width d of the bent portion 13c is preferably set to be equal to or less than 15% of the length from the center of rotation of each of the impeller blades 13 to the outer peripheral end. However, even if the width d of the bent portion 13c is optimized, a certain degree of reduction of the amount of rise in pressure is unavoidable.
As shown in
However, in each of the impeller blades 13, a portion in which a blowing wind speed becomes highest is a region shown by line F-F7′ in
Accordingly, even if the rear edge portion 13b of each of the impeller blades 13 is protruded as shown in
An objective of the present invention is to provide an axial flow fan which effectively compensates for shortage of the amount of rise in static pressure which is lowered by bending the outer peripheral edge of an impeller blade.
In order to achieve the foregoing objective and in accordance with a first aspect of the present invention, an axial flow fan is provided that includes a plurality of impeller blades (13) provided on a hub (14), and a plurality of bent portions (13c) each formed by bending an outer peripheral edge of each of the impeller blades (13) toward a negative pressure surface (13e) of the impeller blade (13). A protruding portion (13f) is provided in a portion in which a blowing wind speed is high and a pressure rising work is most effectively carried out in a rear edge portion (13b) of each of the impeller blades (13). Each of the protruding portions (13f) protrudes to an inverse direction to a rotating direction of the impeller blade (13) with respect to a straight line L connecting a proximal end and an outer peripheral end in the rear edge portion (13b) of each of the impeller blades (13).
In accordance with the structure mentioned above, an air flow (A1) in the pressure surface 13d of each of the impeller blades 13 smoothly goes around to the negative pressure surface 13e from the outer peripheral edge of each of the impeller blades 13. As a result, an eddy current (A2) having a small diameter is formed near the outer peripheral edge of each of the impellers 13. Accordingly, it is possible to suppress an interference between an air flow (A3) of the negative pressure surface 13e of each of the impeller blades 13 and the eddy current (A2).
In this case, in the rear edge portion 13b of each of the impeller blades 13, the protruding portion 13f is provided in the portion in which the blowing wind speed is high and the pressure rising work is most effectively carried out. Further, the protruding portion 13f is protruded in the inverse direction to the rotating direction of each of the impeller blades 13 with respect to the straight line L connecting the proximal end and the outer peripheral end in the rear edge portion of each of the impellers 13. If the vane area of each of the impeller blades 13 is enlarged as mentioned above, it is possible to effectively compensate for the shortage of the amount of rise in static pressure which is lowered by bending the outer peripheral edge of each of the impeller blades 13 to the negative pressure surface 13e. Accordingly, it is possible to achieve a reduction of a blowing noise and a high efficiency of the blowing performance.
In the axial flow fan mentioned above, each of the bent portions (13c) is provided over the entirety of each of the impeller blades (13) from the front edge portion (13a) to the rear edge portion (13b). In this case, the air flow (A1) of the pressure surface 13d of each of the impeller blades 13 smoothly goes around to the negative pressure surface 13e from the outer peripheral edge of each of the impeller blades 13, the eddy current (A2) having the small diameter is formed near the outer peripheral edge of each of the impeller blades 13, and it is possible to suppress the interference between the air flow (A3) of the negative pressure surface 13e of each of the impeller blades 13 and the eddy current (A2).
In the axial flow fan mentioned above, each of the bent portions (13c) is provided in the portion from the position between the front edge portion (13a) and the rear edge portion (13b) in each of the impeller blades (13) to the rear edge portion (13b). In this case, the air flow (A1) of the pressure surface 13d of each of the impeller blades 13 smoothly goes around to the negative pressure surface 13e from the outer peripheral edge of each of the impeller blades 13, the eddy current (A2) having the small diameter is formed near the outer peripheral edge of each of the impeller blades 13, and it is possible to suppress the interference between the air flow (A3) of the negative pressure surface 13e in each of the impeller blades 13 and the eddy current (A2).
In the axial flow fan mentioned above, the width of each of the bent portions (13c) is formed so as to become gradually larger toward the rear edge portion (13b) from the front edge portion (13a) of each of the impeller blades (13).
In this case, in correspondence to the eddy current (A2), the diameter of which becomes larger toward the rear edge portion 13b from the front edge portion 13a of each of the impeller blades 13, it is possible to effectively make the eddy current (A2) small from the front edge portion 13a to the rear edge portion 13b, and it is possible to make it hard for the eddy current (A2) to separate from the negative pressure surface 13e of each of the impeller blades 13.
Accordingly, even if the chord length of each of the impeller blades 13 is made short for the weight saving, the eddy currents (A2) do not interfere with each other between adjacent impeller blades 13, and the turbulence of the air flow generated downstream of the blower is reduced. Accordingly, it is possible to effectively suppress the noise on the basis of a synergistic effect of the operations mentioned above.
In the axial flow fan mentioned above, in each of the protruding portions (13f), the portion protruding most largely in the inverse direction to the rotating direction with respect to the straight line L is set in a region in which a value of an expression (R−Rh)/(Rt−Rh) is between 0.65 and 0.85, in which the radius of the axial flow fan is represented by Rt, the radius of the hub (14) is represented by Rh, and the distance in a radial direction from the center O of rotation of the axial flow fan is represented by R.
On the basis of results of measurement obtained by the inventors et al. of the present invention, the portion in which the blowing wind speed is highest and the pressure rising work is most effectively carried out is a region in which a value of the expression (R−Rh)/(Rt−Rh) is between 0.65 and 0.85 in which the radius of the axial flow fan is represented by Rt, the radius of the hub 14 is represented by Rh, and the distance in a radial direction from the center O of rotation of the axial flow fan is represented by R.
On the basis of the results mentioned above, the vane area of each of the impeller blades 13 is enlarged by setting the protruding portion 13f protruding in the opposite direction to the rotating direction of the axial flow fan with respect to the straight line L connecting the proximal end and the outer peripheral end of each of the impeller blades in the rear edge portion of each of the impeller blades. In accordance with the structure mentioned above, it is possible to further effectively compensate for the shortage of the amount of rise in static pressure which is lowered by bending the outer peripheral edge of each of the impeller blades to the negative pressure surface.
A propeller fan according to one embodiment of the present invention will now be described with reference to
As shown in
An outer peripheral end of a front edge portion 13a and an outer peripheral end of a rear edge portion 13b in each of the impeller blades 13 are arranged in an offset manner in a rotating direction of the impeller blade 13 in comparison with a proximal end of the impeller blade 13. The entire outer peripheral edge of each of the impeller blades 13 is bent toward a negative pressure surface 13e (a suction side) of the impeller blade 13 shown in
In the light of effectively suppressing the generation of the eddy current A2 without lowering the blowing performance of each of the impeller blades 13, it is desirable that the maximum value of the width d of the bent portion 13c be equal to or less than 15% of the length from the center of rotation of the propeller fan 4 (the center of the hub 14) to an outer peripheral end of each of the impeller blades 13.
A protruding portion 13f is provided in the rear edge portion 13b of each of the impeller blades 13. Each of the protruding portions 13f is provided in a portion in which a blowing wind speed is highest and a pressure rising work can be effectively carried out (a region shown by an outer peripheral line having a diameter φ1 to φ5 of the propeller fan 4 in
In each of the protruding portions 13f, a portion which most largely protrudes to the inverse direction to the rotating direction M of the impeller blade 13 is set to a maximum protruding portion T. In the case that the radius of the propeller fan 4 is represented by Rt, the radius of the hub 14 is represented by Rh, and the distance in a radial direction from the center O of rotation of the propeller fan 4 is represented by R, the maximum protruding portion T is set in a region in which a value (R−Rh)/(Rt−Rh) is between 0.65 and 0.85.
A blowing wind speed of the fan at a time of changing the value (R−Rh)/(Rt−Rh) between 0 and 1.0 is measured with respect to the impeller blade 13 of the propeller fan 4 which does not have the bent portion 13c shown in
On the basis of the results in
In the present embodiment, the bent portion 13c is provided in a region (between outer peripheral lines having diameters φ5 and φ6 of the propeller fan 4 in
It is preferable that the maximum protruding portion T of the protruding portion 13f is provided in a region in which the blowing wind speed becomes highest, in a region radially inside of the boundary (the outer peripheral line having the diameter φ5 of the propeller fan in
In contrast, in the case of the propeller fan 4 shown in
Next, a description will be given in detail of an operation of the propeller fan 4 mentioned above.
In the case of the propeller fan 4 in accordance with the present embodiment, the entire outer peripheral edge of each of the impeller blades 13 is bent toward the negative pressure surface 13e of the impeller blade 13 from the front edge portion 13a to the rear edge portion 13b. In this case, as shown in
Further, in the rear edge portion 13b of each of the impeller blades 13, the protruding portion 13f is provided in the portion in which the blowing wind speed is high, and the pressure rising work can be most effectively carried out. Each of the protruding portions 13f protrudes to the inverse direction to the rotating direction of each of the impeller blades 13 with respect to the straight line L connecting the base and the outer peripheral end of the rear edge portion 13b of each of the impeller blades 13. If the vane area of each of the impeller blades 13 is enlarged as mentioned above, it is possible to effectively compensate for the shortage of the amount of rise in static pressure which is lowered by bending the outer peripheral edge of each of the impeller blades 13. Accordingly, it is possible to achieve a reduction of a blowing noise and a high efficiency of the blowing performance.
Further, the width d of each of the bent portions 13c is formed to become larger toward the rear edge portion 13b from the front edge portion 13a of each of the impeller blades 13. Accordingly, it is possible to effectively make the eddy current (A2) small from the front edge portion 13a to the rear edge portion 13b in correspondence to the eddy current (A2) in which the diameter becomes larger toward the rear edge portion 13b from the front edge portion 13a of each of the impeller blades 13, and it is possible to make it hard for the eddy current (A2) to separate from the negative pressure surface 13e of each of the impeller blades 13.
Accordingly, even if the chord length of each of the impeller blades 13 is made short for the weight saving, the eddy currents (A2) do not interfere with each other between adjacent impeller blades 13, and the turbulence of the air flow generated in the downstream side of the blower is reduced. Accordingly, it is possible to effectively suppress the noise on the basis of a synergistic effect of the operations mentioned above.
Further, in the case that the radius of the propeller fan 4 is represented by Rt, the radius of the hub 14 is represented by Rh, and the distance in a radial direction from the center O of rotation of the propeller fan 4 is represented by R, the position of the maximum protruding portion T is set in the region in which the value of (R−Rh)/(Rt−Rh) is between 0.65 and 0.85.
As shown in
Accordingly, it is possible to stably generate the eddy current A2 having the small diameter near the outer peripheral edge of each of the impeller blades 13 by setting the bent portion 13c in the outer peripheral edge of the impeller blade 13, as in the propeller fan 4 in accordance with the present embodiment. Further, the vane area of each of the impeller blades 13 is enlarged by setting the protruding portion 13f in the region in which the blowing wind speed becomes maximum in the rear edge portion 13b of the impeller blade 13. In accordance with the structure mentioned above, it is possible to reduce the noise without lowering the amount of rise in static pressure, even if the bent portion 13c is provided in the outer peripheral edge of each of the impeller blades 13. Accordingly, it is possible to achieve both of the reduction of the blowing noise and the high efficiency of the bellowing performance. Further, since it is unnecessary to enlarge the vane area of each of the impeller blades 13 more than necessary, it is possible to suppress a generation of a material loss as much as possible, and it is possible to achieve a weight saving and a low cost of the propeller fan 4.
In the present embodiment, the bent portion 13c is provided over the entire outer peripheral edge of each impeller blade 13 from the front edge portion 13a to the rear edge portion 13b. However, the bent portion 13c may be provided in a portion from a position between the front edge portion 13a and the rear edge portion 13b to the rear edge portion 13b. In this case, the position between the front edge portion 13a and the rear edge portion 13b is preferably set to a position which is offset from the front edge portion 13a to the rear edge portion 13b at about 25% of the entire length of the outer peripheral edge of the impeller blade 13.
In this case, the air flow (A1) of the pressure surface 13d in each of the impeller blades 13 smoothly goes around to the negative pressure surface 13e from the outer peripheral edge of the impeller blade 13. As a result, the eddy current (A2) having a small diameter is formed near the outer peripheral edge of each of the impeller blades 13. Accordingly, the interference between the air flow (A3) of the negative pressure surface 13e in each of the impeller blades 13 and the eddy current (A2) is suppressed.
In this case, it is possible, in the rear edge portion 13b of the impeller 13, to effectively compensate for the shortage of the amount of rise in static pressure which is lowered by bending the outer peripheral edge of each of the impeller blades 13, by setting the protruding portion 13f in the portion in which the blowing wind speed is high and the pressure rising work can be most effectively carried out. Therefore, it is possible to achieve both of the reduction of the blowing noise and the high efficiency of the blowing performance.
In the embodiment and the modified embodiment mentioned above, the present invention is embodied in impeller blades having a thin vane structure.
However, the present invention is not limited to thin vane structures, but may be applied, for example, to a vane having a thick structure, various air foil vane and the like.
Number | Date | Country | Kind |
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2005-211542 | Jul 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2006/314259 | 7/19/2006 | WO | 00 | 6/16/2008 |