JP2007205268A - Centrifugal fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce blast noise as much as possible in a centrifugal fan provided with a fan rotor 1 having aerofoil shape blades 14 built between outer circumference parts of a hub 12 and a shroud 13 oppositely arranged and having a stepped surface 14a formed on a leading edge of the blade 14. <P>SOLUTION: Deviation of the leading edge of the blade 14 at a position of the stepped surface 14a is set to 0.04-0.18 times the aerofoil chord length of the stepped surface 14a at a position corresponding to the leading edge in an aerofoil width direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to a technical field related to a centrifugal fan used in a blower or the like of an air conditioner.

  Generally, a ceiling-embedded air conditioner is provided with a centrifugal fan (turbo fan) as a blower. The centrifugal fan sucks air in the air-conditioned room, and the air is placed around the centrifugal fan. After being blown onto a heat exchanger arranged in a substantially annular shape, it is blown into the air-conditioned room. Such a centrifugal fan is provided with a fan rotor in which airfoil blades are installed between the outer peripheral portions of a hub and a shroud arranged opposite to each other, and a hub rotor disposed on the opposite side of the hub to the shroud. And a fan motor for rotationally driving around the central axis.

The centrifugal fan is required to reduce blowing noise, and various proposals have been made to satisfy this requirement. For example, in Patent Document 1 and Patent Document 2, a step surface is formed on the leading edge of the blade, the chord length of the blade is changed discontinuously in the blade width direction, and more than the step surface on the leading edge of the blade. The hub side edge located on the hub side is displaced to the front side in the direction of the center line of the blade from the shroud side edge located closer to the shroud than the stepped surface. By doing so, the air flow flowing into the leading edge of the blade is disturbed by the collision with the discontinuity at the leading edge of the blade, and gradually grows on the surface of the blade from the leading edge side to the trailing edge side. A vertical vortex is generated, and the energy of this vertical vortex is supplied to the boundary layer of the air on the blade surface to suppress the growth of the boundary layer, so that the separation phenomenon of the air on the blade surface is minimized. As a result, the blowing noise is reduced and the blowing efficiency of the entire blade is increased, and a low-noise and high-efficiency centrifugal fan can be provided.
Japanese Patent No. 3391319 Japanese Patent Laid-Open No. 2002-364591

  As described above, in the centrifugal fan in which the step surface is formed on the blade leading edge, the inventor has intensively studied to further reduce the blowing sound, and as a result, the amount of deviation of the blade leading edge at the position of the step surface. Has been found to be able to reduce the blowing noise compared to conventional blades.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a centrifugal fan in which a step surface is formed on the blade leading edge as described above, and the front of the blade at the position of the step surface. The object is to reduce the blowing sound as much as possible by appropriately setting the deviation amount of the edge.

  In order to achieve the above object, according to the first aspect of the present invention, a fan rotor (11) in which an airfoil blade (14) is installed between the outer peripheral portions of a hub (12) and a shroud (13) arranged to face each other. And at least one step surface (14a) is formed at the front edge of the blade (14), and is positioned closer to the hub (12) than the step surface (14a) at the front edge of the blade (14). The hub side edge (14b) that is to be displaced is more biased to the front side in the center line direction of the blade (14) than the shroud side edge (14c) located on the shroud (13) side than the stepped surface (14a) For the centrifugal fan positioned, the amount of deviation of the leading edge at the position of the step surface (14a) is 0 of the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. .04 to 0.18 times.

  With the above configuration, the air flow flowing into the front edge of the blade (14) is disturbed by the collision with the discontinuous portion due to the formation of the step surface (14a) at the front edge of the blade (14), and the blade A vertical vortex is generated on the surface of (14), and separation of the air flow is suppressed by the vertical vortex, thereby reducing blowing noise. Then, the deviation amount of the leading edge of the blade (14) at the position of the step surface (14a) is 0.04 to 0 of the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. .. By setting the ratio to 18 times, a longitudinal vortex having an appropriate size is generated, whereby the separation of the air flow is satisfactorily suppressed, and the blowing sound can be effectively reduced.

  According to a second invention, in the first invention, the amount of deviation of the leading edge at the position of the step surface (14a) is a position corresponding to the front end of the step surface (14a) in the blade width direction. It is assumed that the chord length is set to 0.06 to 0.14 times the chord length. As a result, the blowing sound can be further effectively reduced.

  According to a third aspect, in the second aspect, the amount of deviation of the leading edge at the position of the step surface (14a) is a position corresponding to the front end of the step surface (14a) in the blade width direction. It is assumed that the chord length is set to 0.07 to 0.10 times. As a result, the blowing sound can be reduced to the maximum.

  According to a fourth aspect, in the third aspect, the amount of deviation of the leading edge at the position of the step surface (14a) is a position corresponding to the front end of the step surface (14a) in the blade width direction. It is assumed that the chord length is set to 0.07 to 0.09 times the chord length.

  This makes it possible to reduce the blowing noise to the maximum and to reduce the maximum chord length as much as possible.As a result, the mold for manufacturing the blade (14) with resin or the like can be downsized. Manufacturing costs can be reduced.

  In a fifth aspect according to the first aspect, the amount of deviation of the leading edge at the position of the step surface (14a) is a position corresponding to the front end of the step surface (14a) in the blade width direction. It is assumed that the chord length is set to 0.04 to 0.09 times the chord length.

  By doing so, it is possible to reduce the manufacturing cost of the blade (14) as much as possible while satisfactorily reducing the blowing sound.

  As described above, according to the present invention, the deviation amount of the leading edge of the blade (14) at the position of the step surface (14a) is determined at the position corresponding to the front end of the step surface (14a) in the blade width direction. By setting the chord length to 0.04 to 0.18 times the chord length, a vertical vortex of an appropriate size is generated on the surface of the blade (14) to effectively suppress the separation of the air flow and to effect the blowing sound. Can be reduced.

  In particular, in the second invention, the displacement amount of the leading edge of the blade (14) at the position of the step surface (14a) is determined by the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. By setting it to 0.06 to 0.14 times, it is possible to more effectively reduce the blowing sound.

  Furthermore, in the third aspect of the invention, the amount of deviation of the leading edge of the blade (14) at the position of the step surface (14a) is calculated as the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. By setting the value to 0.07 to 0.10 times, the blowing sound can be reduced to the maximum.

  In the fourth aspect of the invention, the amount of deviation of the leading edge of the blade (14) at the position of the step surface (14a) is calculated as the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. By setting it to 0.07 to 0.09 times, the blowing sound can be reduced to the maximum, and the manufacturing cost of the blade (14) can be reduced.

  Furthermore, in the fifth invention, the amount of deviation of the leading edge of the blade (14) at the position of the step surface (14a) is determined by the chord at the position corresponding to the front end of the step surface (14a) in the blade width direction. By setting it to 0.04 to 0.09 times the length, it is possible to reduce the manufacturing cost of the blade (14) as much as possible while satisfactorily reducing the blowing sound.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a ceiling-embedded air conditioner equipped with a centrifugal fan (F) according to an embodiment of the present invention. This air conditioner includes a casing (1) that houses various components therein. ing. The casing (1) includes a casing body (1a) and a decorative panel (1b) disposed on the lower side of the casing body (1a).

  The casing body (1a) has a substantially rectangular shape when viewed from below (four corners are chamfered, and can be said to be an approximately octagonal shape in which long and short sides are alternately formed). A box-shaped body that is opened to the ceiling wall (C) via a fixing bracket (not shown) so that the opening faces the opening formed in the ceiling wall (C) of the air conditioning room. ing.

  The decorative panel (1b) is fixed to the lower end of the casing body (1a) so as to cover the opening of the casing body (1a) and the opening of the ceiling wall (C). The decorative panel (1b) is a substantially rectangular plate-like body as viewed from below, and is provided at the substantially central portion of the decorative panel (1b) and sucks air in the air-conditioned room, and the decorative panel (1b) ) And four outlets (3) for blowing air from the inside of the casing body (1a) into the air-conditioned room. The suction port (2) is a substantially square-shaped opening, and each air outlet (3) is a substantially rectangular-shaped opening that extends along each side.

  The suction port (2) is provided with a suction grill (4) and a filter (5) for removing dust in the air sucked from the suction port (2). Each of the air outlets (3) is provided with a flap (6) that is swung around an axis extending in the longitudinal direction of the air outlet (3) by a motor (not shown). ) Can be varied to change the air direction of the air blown from the air outlet (3) into the air-conditioned room.

  In the inside of the casing body (1a), mainly, a centrifugal fan (F) that functions as a blower that sucks air in the air-conditioned room into the casing body (1a) through the suction port (2) and blows it in the outer peripheral direction, A substantially annular heat exchanger (8) is provided so as to surround the outer periphery of the centrifugal fan (F).

  The centrifugal fan (F) is a turbo fan, and as shown in FIG. 2, a plurality of (the main fans) are disposed between the outer peripheral portions of a circular hub (12) and a shroud (13) that are opposed to each other in the vertical direction. In the embodiment, the fan rotor (11) having seven blades (14) having a cross-section airfoil mounted at equal intervals in the circumferential direction and the shroud (13) of the hub (12) are arranged on the opposite side. And a fan motor (15) for rotationally driving the fan rotor (11) around a central axis of the hub (12) (also a central axis of the shroud (13) and a central axis of the fan rotor (11)). ). The hub (12), shroud (13) and blade (14) are all made of resin.

  A projecting portion (12a) projecting in a substantially conical shape to the opposite side (lower side) of the fan motor (15) is formed at the center of the hub (12). Due to the formation of the projecting portion (12a), the surface (upper surface) on the fan motor (15) side of the central portion of the hub (12) is recessed in a substantially conical shape, and the recessed upper surface and the casing body (1a A space for accommodating the fan motor (15) is formed between the upper surface in the bracket). A cylindrical boss portion (12b) is integrally formed at the tip (lower end) of the protruding portion (12a), and the center of the boss portion (12b) (corresponding to the center of the hub (12)). The drive shaft of the fan motor (15) is connected. As a result, the fan rotor (11) is driven to rotate counterclockwise in FIG. 2 around the central axis of the hub (12) by the fan motor (15).

  The shroud (13) has an air introduction opening (13a) at the center, and air sucked from the suction opening (2) between the air introduction opening (13a) and the hub (12). An air passage (18) that guides toward the outer peripheral side of the fan rotor (11), that is, toward the heat exchanger (8) is formed. A bell for guiding the air sucked from the suction port (2) to the air introduction opening (13a) is located below the air introduction opening (13a) of the shroud (13) (on the suction port (2) side). A mouse (20) is placed.

  The heat exchanger (8) is a cross fin tube type heat exchanger panel formed by being bent so as to surround the outer periphery of the centrifugal fan (F), and is attached to an outdoor unit (not shown) installed outdoors. It is connected via refrigerant piping. The heat exchanger (8) can function as a refrigerant evaporator flowing inside during the cooling operation and as a refrigerant condenser flowing inside during the heating operation. Thereby, the heat exchanger (8) exchanges heat with the air sucked into the casing body (1a) through the suction port (2) and blown out from the fan rotor (11) of the centrifugal fan (F), Air can be cooled during cooling operation, and air can be heated during heating operation. A drain pan (22) for receiving drain water generated by condensation of moisture in the air in the heat exchanger (8) is disposed below the heat exchanger (8).

  When the operation of the air conditioner is started, the fan motor (15) of the centrifugal fan (F) is driven, and the fan rotor (11) rotates around the central axis of the hub (12). In addition, refrigerant is supplied from the outdoor unit into the heat exchanger (8), and the heat exchanger (8) functions as an evaporator during the cooling operation and as a condenser during the heating operation. As the fan rotor (11) rotates, the air in the air-conditioned room passes through the air inlet opening (13a) of the filter (5), the bell mouth (20), and the shroud (13) from the suction port (2). It is sucked into the air passage (18) of (15). The sucked air flows in the air passage (18) outward in the hub radial direction. The air flowing in the air passage (18) is blown out to the outer peripheral side of the fan rotor (15) by the blades (14) and reaches the heat exchanger (8), and is cooled or heated in the heat exchanger (8). After that, the air is blown out from the air outlet (3) toward the air-conditioned room. In this way, cooling or heating in the air-conditioned room is performed.

  In the centrifugal fan (F), two step surfaces (14a) are formed on the front edge of the blade (14) on the hub (12) side as shown in an enlarged view in FIG. As a result, the hub side edge (14b) located on the hub (12) side of each step surface (14a) at the front edge of the blade (14) is closer to the shroud (13) side than the step surface (14a). The shroud side edge (14c) located at the center is displaced to the front side in the center line direction of the blade (14). The portion located between the two step surfaces (14a) on the front edge of the blade (14) is the hub side edge (14b) with respect to the step surface (14a) on the shroud (13) side, The stepped surface (14a) on the hub (12) side is a shroud side edge (14c).

  The deviation d of the leading edge at the position of the step surface (14a) is a chord length L at a position corresponding to the front end of the step surface (14a) in the blade width direction (H direction shown in FIG. 3). Is set to 0.04 to 0.18 times. That is, in the case of the stepped surface (14a) on the shroud (13) side, as shown in FIG. 3, d = d1, L = L1, and d1 / L1 = 0.04 to 0.18. In the case of the step surface (14a) on the hub (12) side, d = d2, L = L2, and d2 / L2 = 0.04 to 0.18. In the present embodiment, d1 / L1 = d2 / L2, but d1 / L1 and d2 / L2 may be different from each other.

  The value of d / L is set to 0.04 to 0.18 for the following reason. That is, the air flow flowing into the front edge of the blade (14) is disturbed by the collision with the discontinuous portion due to the formation of the step surface (14a) at the front edge of the blade (14), and the blade (14) Longitudinal vortices are generated on the surface of the airflow, and separation of the air flow is suppressed by the longitudinal vortices, so that blowing noise is reduced. At this time, if the value of d / L is 0.04 to 0.18, a longitudinal vortex of an appropriate size is generated, and thereby air flow separation is suppressed satisfactorily, and the blowing sound is effective. Can be reduced.

  Here, FIG. 4 shows the measurement result of the blowing sound when the value of d / L (= d1 / L1 = d2 / L2) of the blade (14) is changed. There are four values of d / L of the blade (14) used for this measurement: 0.03846, 0.07956, 0.09790, and 0.17618. Then, the centrifugal fan (F) incorporating these blades (14) was mounted on the air conditioner, and the blowing sound was measured at a position 1.5 m below the decorative panel (1b). Similarly, a centrifugal fan incorporating a blade (d / L = 0) having no step surface (14a) is mounted on the air conditioner, and 1.5 m below the decorative panel (1b). The blowing sound was measured at a remote position. FIG. 4 shows how much the blowing sound of the blade (14) having two step surfaces (14a) is reduced compared to the blade having no step surface (14a). From this measurement result, it is understood that if the value of d / L is 0.04 to 0.18, a good sound reduction effect can be obtained for a blade having no step surface (14a).

  When the blades having one and three step surfaces (14a) were also measured in the same manner, the sound reduction amount for the blades having no step surface (14a) was reduced to the blades having two step surfaces (14a) (14 However, if the d / L value is 0.04 to 0.18, the blowing sound can be effectively reduced.

  From the viewpoint of reducing the blowing sound, a more preferable range of the d / L value is 0.06 to 0.14, and a further preferable range is 0.07 to 0.10.

  Moreover, when the value of d / L is about 0.09, the effect of reducing the blowing sound is maximized, and the value of d / L is 0.04 to 0.09, and the value of d / L In the case of 0.09 to 0.18, the effect of reducing the blowing sound is substantially the same. Here, if the effect of reducing the blowing sound is substantially the same, the value of d / L is 0.04 to 0.00 in terms of reducing the maximum chord length as much as possible to reduce the manufacturing cost of the blade (14). 09 is preferable. Similarly, the most preferable value of d / L is 0.07 to 0.09 from the viewpoint of reducing blowing noise and manufacturing cost.

  In the present embodiment, each stepped surface (14a) approaches the hub (12) side from the inner peripheral surface side (negative pressure side) of the blade (14) toward the outer peripheral surface side (front side in FIG. 3). Inclined to do. That is, when the centrifugal fan (F) is operating at a large air volume (especially in the centrifugal fan of an air conditioner, the large air volume area is generally used as the actual air volume area), the outer peripheral surface side of the blade (14) A separation zone occurs in the surface, but due to the inclination of the stepped surface (14a), the vertical vortex can be intensively generated on the outer peripheral surface side of the blade (14), effectively reducing the blowing sound. become able to.

  Further, in the present embodiment, the hub side edge (14b) located on the hub (12) side with respect to each stepped surface (14a), the blade (14) as it goes from the shroud (13) side to the hub (12) side. ) Incline so as to move backward toward the center line direction. As a result, the corner between the step surface (14a) and the hub side edge (14b) is slightly sharpened, and the vertical vortex is likely to occur.

  Therefore, in the present embodiment, the deflection amount d of the leading edge of the blade (14) at the position of the step surface (14a) is a chord at a position corresponding to the front end of the step surface (14a) in the blade width direction. Since it is set to 0.04 to 0.18 times the length L, a vertical vortex of an appropriate size is generated on the surface of the blade (14) to effectively suppress the separation of the air flow and to effect the blowing sound. Can be reduced.

  In the above embodiment, the two step surfaces (14a) are formed on the front edge of the blade (14), but the number of the step surfaces (14a) may be one or three or more. .

  In the above embodiment, the step surface (14a) is inclined so as to approach the hub (12) side from the inner peripheral surface side to the outer peripheral surface side of the blade (14), and the hub side edge (14b). ) Is inclined so as to move backward from the shroud (13) side toward the hub (12) side toward the rear side in the center line direction of the blade (14). If the value is set to 0.04 to 0.18, the blowing sound can be effectively reduced.

  Furthermore, although the present invention has been shown as an example applied to a turbo fan used in a blower of an air conditioner, the present invention is applicable to any centrifugal fan such as a turbo fan or a sirocco fan. be able to.

  INDUSTRIAL APPLICABILITY The present invention is useful for a centrifugal fan such as a turbo fan used for an air conditioner blower or the like.

1 is a cross-sectional view showing a ceiling-embedded air conditioner equipped with a centrifugal fan according to an embodiment of the present invention. It is the figure seen from the shroud side which shows a centrifugal fan. It is the figure seen from the outer peripheral surface side of this blade | wing which shows the principal part of a blade | wing. It is a graph which shows the relationship between the value of d / L, and the sound reduction amount with respect to the blade | wing which does not have a level | step difference surface of the blade | wing which has two level | step difference surfaces.

Explanation of symbols

F Centrifugal fan 11 Fan rotor 12 Hub 12a Protruding part 12c Boss part 13 Shroud 14 Blade 14a Step surface 15 Fan motor

Claims (5)

There is provided a fan rotor (11) in which airfoil blades (14) are installed between the outer peripheral portions of a hub (12) and a shroud (13) arranged opposite to each other, and at least one of the front edges of the blades (14). A stepped surface (14a) is formed, and the hub side edge (14b) positioned on the hub (12) side of the stepped surface (14a) at the front edge of the blade (14) is formed on the stepped surface (14a). ) Than the shroud side edge (14c) located on the shroud (13) side than the centrifugal fan that is displaced to the front side in the direction of the center line of the blade (14),
The amount of deviation of the leading edge at the position of the step surface (14a) is 0.04 to 0.18 times the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. Centrifugal fan characterized by being set. The centrifugal fan according to claim 1, wherein
The amount of deviation of the leading edge at the position of the step surface (14a) is 0.06 to 0.14 times the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. Centrifugal fan characterized by being set. The centrifugal fan according to claim 2, wherein
The amount of deviation of the leading edge at the position of the step surface (14a) is 0.07 to 0.10 times the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. Centrifugal fan characterized by being set. The centrifugal fan according to claim 3,
The amount of deviation of the leading edge at the position of the step surface (14a) is 0.07 to 0.09 times the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. Centrifugal fan characterized by being set. The centrifugal fan according to claim 1, wherein
The amount of deviation of the leading edge at the position of the step surface (14a) is 0.04 to 0.09 times the chord length at the position corresponding to the front end of the step surface (14a) in the blade width direction. Centrifugal fan characterized by being set.

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