JP2006017028A - Blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly efficient and low-noise blower without enlarging a propeller fan. <P>SOLUTION: In a plurality of blades extending from a hub part of the propeller fan to an outer peripheral side, a distance between an outer peripheral edge C on a downstream side in a rotation direction of the propeller fan and a rotation center O of the propeller fan is set to be longer than a distance between an outer peripheral edge B on an upstream side in the rotation direction of the propeller fan and the rotation center O of the propeller fan. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an axial-flow type air blower provided in, for example, an air blowing portion of an outdoor unit of an air conditioner. In particular, the present invention relates to measures for reducing noise generated by the blower.

  Conventionally, for example, as disclosed in Patent Document 1 and Patent Document 2 below, a blower is provided in an air blowing portion of an outdoor unit of an air conditioner. FIG. 12 is a perspective view of a blower provided in a general outdoor unit as viewed from the inside of the outdoor unit. As shown in this figure, the blower includes a propeller fan (blower fan) b provided in an air discharge port a formed in the outdoor unit casing, and a cylinder extending from the opening edge of the air discharge port a toward the exhaust side. And a shroud c having a shape. That is, the shroud c is configured to surround the outer peripheral portion with a slight tip clearance (gap between the inner surface of the shroud c and the outer edge of the propeller fan b) with respect to the outer edge of the propeller fan b. .

When the air conditioner is in operation, the propeller fan b rotates as the fan motor (not shown) is driven (in FIG. 12, the direction of rotation is indicated by an arrow A), and extends from the air inlet to the air outlet a in the outdoor unit. An air flow is generated (in FIG. 12, an air flow is generated from the front side of the paper toward the back side). Then, heat is exchanged between the air introduced into the outdoor unit and the refrigerant flowing through the heat exchanger, so that the refrigerant condensing operation (during cooling operation) is performed.
JP-A-8-189671 Japanese Patent Laid-Open No. 10-238825

  By the way, this type of blower is required to have low noise, space saving, and high efficiency. A propeller fan with a relatively large diameter has been adopted as a means to achieve high efficiency while being low noise (allowing to obtain a large air volume). Can not be planned.

  Fan noise can be broadly classified into broadband noise and narrow-band pitch noise. Broadband noise is dominant in propeller fans of relatively low speed for air conditioners and ventilation fans. The origin of this broadband noise is the turbulence of air, and the sound source is the fluctuation of pressure on the blade surface of the propeller fan and the vortex created by the air flow away from the blade trailing edge (upstream side edge in the rotation direction). ing.

  In order to reduce such fan noise, measures have been taken such as stabilizing the flow by making the blade shape a forward blade, and setting the blade cord length longer to reduce and equalize the lift distribution. Yes.

  However, these means are close to the limit due to the strength and manufacturing convenience of the propeller fan. For this reason, it is required to reduce fan noise by other methods.

  In order to reduce the noise of the propeller fan, the distance between the tip of the blade and the tip of the shroud and the tip clearance are reduced. However, in this case, when subjected to thermal expansion / contraction or an unexpected mechanical load, the blade may come into contact with the shroud, which is not practical.

  This invention is made | formed in view of this point, The place made into the objective is providing the highly efficient and low noise air blower, without enlarging a propeller fan.

  Specifically, the solution provided by the present invention is premised on an air blower including a propeller fan having a plurality of blades. For this blower, the distance from the outer peripheral edge of the propeller fan in the rotation direction upstream to the rotation center of the propeller fan in each blade, and the outer peripheral edge of the propeller fan in the rotation direction downstream to the rotation center of the propeller fan. The distance is different from each other.

  More specifically, the distance from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan to the rotation center of the propeller fan in each blade is determined from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan to the rotation center of the propeller fan. It is set longer than the distance.

  Furthermore, in this case, as the shape of the outer peripheral edge of each blade, the distance from the rotation center of the propeller fan from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan to the outer peripheral edge on the downstream side in the rotation direction of the propeller fan is The shape changes continuously.

  If there is a possibility that the stay for supporting the fan motor that rotates the propeller fan may interfere with the blade due to these specific matters, the outer diameter of the portion that may cause the interference (distance from the rotation center of the propeller fan) ) Can be reduced to avoid this interference. In particular, the propeller fan is installed in the same installation area (the opening area necessary for installing the propeller fan) by increasing the distance from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan to the rotation center of the propeller fan. In this case, compared with the conventional one, the present solution can achieve the same or better effect and increase the air flow rate. Or if it is the same air volume, a noise reduction effect can be show | played compared with a conventional thing. Furthermore, the tip clearance can be enlarged over most of the outer peripheral edge of the propeller fan with respect to the existing shroud, and the blade can be reliably prevented from coming into contact with the shroud.

  Specifically, as the ratio of the distances described above, “from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan” of “the distance from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan to the rotation center of the propeller fan: Dle” As a ratio (Dle / Dte) to the distance to the rotation center of the propeller fan: Dte, a range of 0.8 to 1.20 (excluding 1.0) is listed. Preferably, the range of Dle / Dte = 1.02-1.20 is listed. More preferably, the range of Dle / Dte = 1.05 to 1.10.

  The ratio (tc / D) of the tip clearance tc to the propeller fan diameter D is preferably in the range of 0.01 to 0.04. More preferably, the range of tc / D = 0.02 to 0.03 is listed. The chip clearance tc has an appropriate value depending on the operating condition of the fan. Generally, the smaller the tip clearance tc, the higher the performance. However, the inventors of the present invention indicate that it is better to set the tip clearance tc larger under low pressure and high air flow conditions. I found it. The solid line in FIG. 6 shows an example of the relationship between the ratio (tc / D) and the specific noise when the static pressure is low and the air flow is large. The ratio tc / D between the tip clearance tc and the fan diameter D is a good value in the range of 0.02 to 0.04. On the other hand, the broken line in FIG. 6 is a result when the static pressure is high and the air flow is used with a small air volume, and a good value is obtained in the range of tc / D = 0.01 to 0.02. Noise is reduced when the tip clearance is large under low static pressure conditions. The pressure difference before and after the shroud is small, the air blown back from the blade pressure surface to the suction surface is small, and air is blown by the dynamic pressure effect. The reason is that the flow rate does not decrease or increases. The second reason is that by increasing the tip clearance, noise generation due to pressure interference generated between the blade and the shroud is also reduced. Under the condition of high static pressure, it can be seen that the chip clearance is better when the tip clearance is somewhat narrow as in the prior art.

  Further, the ratio (Sl / D) of the length dimension Sl of the shroud blowing direction (extension direction of the rotation axis of the propeller fan) to the diameter D of the propeller fan is preferably in the range of 0.03 to 0.20. More preferably, the range of Sl / D = 0.10-0.15 is mentioned. FIG. 8 shows the relationship between the ratio (Sl / D) and the specific noise. In the prior art, there is a case where Sl / D is extremely long, but in this solution, the range of Sl / D = 0.03 to 0.20 is appropriate. The effect of the shroud is to ensure a pressure difference before and after the fan, and in that sense, the larger the Sl / D, the better. However, in reality, the shroud itself is a kind of resistor, and if S1 is too long, the smooth flow of fluid (air) is hindered. In particular, this tendency is remarkable under conditions where the static pressure is low. Further, since the blade interferes with the shroud, noise increases under the condition that Sl is too long. For this reason, Sl / D within the above range is appropriate.

  As another solution for achieving the above object, there is provided a blower device including a propeller fan having a plurality of blades and a shroud formed in a cylindrical shape so as to surround the outer peripheral edge of the propeller fan. Assumption. In the air blower, the shroud is provided with an enlarged diameter portion that gradually increases the opening area toward the downstream side in the air blowing direction accompanying the rotation of the propeller fan.

  The shape of the shroud is made up of a plane parallel to the axial direction so that it can be easily punched if production is prioritized on the premise that the shroud is made of a polymer material. However, in order to obtain the effect of recovering the dynamic pressure component due to the acceleration of the fluid (air) by the blade, that is, the pressure recovery effect (diffuser effect), the shape may be widened downstream. This angle needs to be within a range where flow separation does not occur on the shroud surface, and an appropriate range is 30 ° or less.

  In this case, the shroud is provided with a reduced diameter portion which is located upstream of the enlarged diameter portion in the air blowing direction and gradually decreases the opening area toward the downstream side of the air blowing direction, and the reduced diameter portion and the enlarged diameter portion. And forming a bulging portion that bulges toward the center side of the propeller fan. As described above, the boundary portion between the reduced diameter portion and the enlarged diameter portion is formed by a curved surface, and a so-called streamline shape can be used to further increase the pressure recovery effect.

  As a positional relationship between the propeller fan and the shroud, a ratio (Pl / D) of the propeller fan protrusion amount Pl from the shroud blowing side edge to the propeller fan diameter D is in the range of -0.08 to +0.08. Is set.

  As described above, according to the present invention, the shape of each blade constituting the propeller fan is improved, and the shape of the shroud is improved, so that the propeller fan is not increased in size and is highly efficient and low noise. It becomes possible to provide a blower. Thereby, both quietness and high performance of the blower can be achieved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This form demonstrates the case where this invention is applied to the ventilation unit (air blower) with which the air blowing part of the outdoor unit of GHP (gas heat pump) was equipped.

-Overall configuration of GHP outdoor unit-
FIG. 1 is a perspective view showing an internal configuration of a GHP outdoor unit according to this embodiment, FIG. 2 is a front view thereof, and FIG. 3 is a plan view thereof.

  As shown in these drawings, the package 4 of the GHP outdoor unit is composed of two apparatus chambers 1 and 2 that are divided into upper and lower parts, the upper side being the heat exchange chamber 1, and the lower side being the engine room 2. . Here, the heat exchange chamber 1 is a space through which outside air can be ventilated for heat exchange described later, and the engine room 2 is in a substantially sealed state connected to the outside only through the intake pipe and the exhaust pipe. The heat exchange chamber 1 accommodates an outdoor heat exchanger (not shown) for the refrigerant circuit of the GHP and a radiator (not shown) for the engine coolant circuit, and is introduced into the heat exchange chamber 1. The air exchanges heat with the refrigerant flowing in the outdoor heat exchanger and the cooling water flowing in the radiator.

  An engine 31, a refrigerant compressor 21, an accumulator 27, and the like are installed in the engine room 2, and an intake silencer 8, an exhaust silencer 9, and the like are attached to the engine 31. Further, an oil pan 5 for storing lubricating oil of the engine 31 and an auxiliary oil pan 6 communicating with the oil pan 5 are disposed near the bottom of the engine 31. The engine room 2 is provided with an electrical box 11 in which electrical components such as a control device are housed, piping and the like constituting the refrigerant circuit 20, and provided separately from the oil pan 5 for lubricating oil. A stored oil tank 10 is arranged.

  The oil tank 10 and the auxiliary oil pan 6 are connected to each other so that the lubricating oil stored in the oil tank 10 is replenished to the auxiliary oil pan 6 by a lubricating oil pump 18 interposed in the middle of the connection. It is configured.

  In addition, on the ceiling surface of the heat exchange chamber 1 provided on the upper side of the engine room 2, a blower unit 50 including heat radiating fans (propeller fans) 15 and 15 is provided. On the other hand, an introduction opening for introducing outside air into the heat exchange chamber 1 is formed on the side surface of the heat exchange chamber 1. And the said outdoor heat exchanger and a radiator are arrange | positioned in the position which faces this introduction opening. As a result, when the heat dissipating fans 15 and 15 are rotationally driven, an air flow from the introduction opening to the discharge opening of the blower unit 50 is generated, and the refrigerant flowing in the outdoor heat exchanger and the cooling water flowing in the radiator The heat exchange with the outside air introduced into the heat exchange chamber 1 is performed. That is, by the heat exchange between the refrigerant flowing in the outdoor heat exchanger and the outside air, the refrigerant condensing operation is performed during the cooling operation, and the refrigerant evaporating operation is performed during the heating operation. Further, the temperature of the cooling water flowing in the water jacket of the engine is lowered by heat exchange between the cooling water flowing in the radiator and the outside air, thereby preventing the engine from overheating. A fan guard 51 for protecting the fan 15 is disposed on the blowing side of the heat dissipation fan 15.

  An exhaust port 14 is opened on the ceiling surface of the heat exchange chamber 1, and exhaust from the engine 31 after passing through the exhaust silencer 9 is discharged from the exhaust port 14 to the outside.

-Blower unit configuration-
The feature of this embodiment resides in the blower unit 50 for introducing outside air into the heat exchange chamber 1 for heat exchange with the refrigerant flowing through the outdoor heat exchanger and the cooling water flowing through the radiator. The blower unit 50 has the propeller fan 15 provided in the air discharge port formed on the ceiling surface of the heat exchange chamber 1 and the opening edge of the air discharge port toward the exhaust side (the upper side in the present embodiment). An extending cylindrical shroud 52 is provided. That is, the shroud 52 is configured to surround the outer peripheral portion with a slight tip clearance with respect to the outer edge of the propeller fan 15. Hereinafter, several embodiment about this ventilation unit 50 is described.

(First embodiment)
As shown in FIG. 4 (a plan view of the propeller fan 15 and the direction of rotation is an arrow A), the propeller fan 15 according to the present embodiment includes a plurality of propeller fans 15 extending from the hub portion 15a to the outer peripheral side (four in this embodiment). ) Blades 15b, 15b,... And in these blades 15b, 15b,..., A distance Dte from the outer peripheral edge (point B in FIG. 4) on the upstream side in the rotation direction of the propeller fan 15 to the rotation center (point O in FIG. 4) of the propeller fan 15; The distance Dle from the outer peripheral edge (point C in FIG. 4) on the downstream side in the rotation direction of the propeller fan 15 to the rotation center (point O in FIG. 4) of the propeller fan 15 is different from each other. More specifically, the distance Dle from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan 15 to the rotation center of the propeller fan 15 is the rotation center of the propeller fan from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan. Is set to be longer than the distance Dte. The blades 15b, 15b,... Have the same shape, and the outer peripheral edge of the blade 15b is the outer peripheral edge B on the downstream side in the rotational direction of the propeller fan 15 from the outer peripheral edge B on the upstream side in the rotational direction of the propeller fan 15. A distance from the rotation center O of the propeller fan 15 continuously changes (continuously increases) over the edge C.

  Specifically, “the distance Dle from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan 15 to the rotation center of the propeller fan 15” “the rotation of the propeller fan 15 from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan 15”. As a ratio (Dle / Dte) to the distance Dte to the center, a range of 1.02 to 1.20 is listed. Preferably, the range of Dle / Dte = 1.05 to 1.10. More specifically, the distance Dle from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan 15 to the rotation center of the propeller fan 15 is set to 300 mm, and from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan 15. For example, the distance Dte to the center of rotation is set to 270 mm. Note that the dimensions are not limited to this.

  According to the present embodiment, when there is a possibility that a stay or the like for supporting a fan motor that rotationally drives the propeller fan 15 interferes with the blade 15b, the outer diameter of the portion that is likely to interfere (the propeller fan 15 This interference can be avoided by reducing the distance from the center of rotation. In particular, by increasing the distance Dle from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan 15 to the rotation center of the propeller fan, the propeller fan has the same installation area (the opening area necessary for installing the propeller fan 15). In the case of installing 15, compared to the conventional one, the present embodiment can achieve an effect equal to or greater than that, and can increase the amount of air blown. Or if it is the same air volume, a noise reduction effect can be show | played compared with a conventional thing. Furthermore, the tip clearance can be increased with respect to the existing shroud 52, and the blade 15b can be reliably prevented from coming into contact with the shroud 52.

  In this embodiment, the outer peripheral edge of the blade 15b extends from the outer peripheral edge B on the upstream side in the rotation direction of the propeller fan 15 to the outer peripheral edge C on the downstream side in the rotation direction of the propeller fan 15. Although the shape in which the distance from O changes continuously, it is not always necessary to change it continuously. For example, considering the contact between the outer peripheral edge of the propeller fan 15 and the shroud 52, the shape of the outer peripheral end surface of the propeller fan 15 extends from the outer peripheral edge B on the upstream side in the rotational direction to the outer peripheral edge C on the downstream side in the rotational direction. It may be an S-shaped curve.

(Second Embodiment)
In this embodiment, as shown in FIG. 5 (a plan view showing the propeller fan 15 and the shroud 52), the ratio (tc / D) of the tip clearance tc to the diameter D of the propeller fan is 0.01 to 0.04. Is set in the range. The range of tc / D = 0.02 to 0.03 is preferred. The tip clearance tc has an appropriate value depending on the operating conditions of the propeller fan 15.

  The reason why the tip clearance tc is set larger as in the present embodiment will be described with reference to FIG. The solid line in FIG. 6 shows an example of the relationship between the ratio (tc / D) and the specific noise when the static pressure is low and the air flow is used. The ratio tc / D between the tip clearance tc and the fan diameter D is a good value in the range of 0.02 to 0.04. In this way, when the tip clearance is large under low static pressure conditions, the noise is reduced because the pressure difference before and after the shroud is small, the air blown back from the blade pressure surface to the suction surface is small, and the air is blown by the dynamic pressure effect. The reason is that the flow rate does not decrease or increases. The second reason is that by increasing the tip clearance, noise generation due to pressure interference generated between the blade 15 and the shroud 52 is also reduced. In addition, the broken line of FIG. 6 is a result at the time of using a static pressure with high air volume, and has become a favorable value in the range of tc / D = 0.01-0.02.

(Third embodiment)
In the present embodiment, as shown in FIG. 7 (a cross-sectional view of the propeller fan 15 and the shroud 52 as viewed from the side), the length dimension S1 in the blowing direction of the shroud 52 (extension direction of the rotation axis of the propeller fan 15) The ratio (Sl / D) to the diameter D of the propeller fan is set in the range of 0.03 to 0.20. Preferably, the range of Sl / D = 0.10-0.15 is hung up. FIG. 8 shows the relationship between the ratio (Sl / D) and the specific noise. In the present embodiment, the range of Sl / D = 0.03 to 0.20 is appropriate. The effect of the shroud 52 is to ensure a pressure difference before and after the fan. In this sense, the larger the Sl / D, the better. However, in reality, the shroud itself is a kind of resistor, and if Sl is too long, the smooth flow of the fluid is hindered. In particular, this tendency is remarkable under conditions where the static pressure is low. Further, since the blade 15b interferes with the shroud 52, the noise increases when Sl is too long. For this reason, in this embodiment, the ratio Sl / D is set in the range of 0.03 to 0.20.

(Fourth embodiment)
In the present embodiment, as shown in FIG. 9, the shroud 52 is provided with a diameter-enlarged portion 53 that gradually increases the opening area toward the downstream side in the blowing direction accompanying the rotation of the propeller fan 15.

  The shape of the shroud 52 is formed on a surface parallel to the axial direction so that it can be easily punched if priority is given to the manufacturing convenience on the premise that the shroud 52 is manufactured from a polymer material. On the other hand, in order to obtain the effect of recovering the dynamic pressure component due to the fluid being accelerated by the blade 15b, that is, the pressure recovery effect (diffuser effect), the shape may be widened downstream. This angle α needs to be within a range where flow separation does not occur on the shroud surface, and an appropriate range is 30 ° or less.

(Fifth embodiment)
In the present embodiment, as shown in FIG. 10, the shroud 52 is positioned on the upstream side in the blowing direction with respect to the diameter-enlarged portion 53 and gradually reduces the opening area toward the downstream side in the blowing direction. And a bulging portion 55 that bulges toward the center of the propeller fan 15 is formed at the boundary between the reduced diameter portion 54 and the enlarged diameter portion 53. In this way, the boundary portion between the reduced diameter portion 54 and the enlarged diameter portion 53 is formed of a curved surface, and a so-called streamline shape can provide a greater pressure recovery effect.

(Sixth embodiment)
In the present embodiment, the positional relationship between the propeller fan 15 and the shroud 52 is specified. As shown in FIG. 7, the ratio (Pl / D) of the protrusion amount Pl of the propeller fan 15 from the blower side edge of the shroud 52 to the diameter D of the propeller fan 15 is set in the range of -0.08 to +0.08. is doing.

  FIG. 11 shows the relationship between the ratio (Pl / D) and the specific noise. As is apparent from this figure, the specific noise can be kept low by setting this ratio (Pl / D) in the range of -0.08 to +0.08.

-Other embodiments-
In the above-described embodiment, the case where the present invention is applied to the blower unit of the outdoor unit of the GHP has been described. The present invention is not limited to this, and can be applied to a blower unit provided in another device (such as an outdoor unit of EHP).

  In the first embodiment described above, the distance from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan to the rotation center of the propeller fan is from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan to the rotation center of the propeller fan. However, on the contrary, the distance from the outer peripheral edge on the upstream side of the propeller fan in the rotational direction to the rotational center of the propeller fan is the outer peripheral edge on the downstream side in the rotational direction of the propeller fan. It may be set longer than the distance from the rotation center of the propeller fan.

  Moreover, although each embodiment demonstrated propeller fan 15 provided with four blade 15b, 15b, ..., it is not restricted to this, The application to the propeller fan provided with three or less blades or five or more blades is also possible. Is possible.

  Moreover, although embodiment mentioned above demonstrated the ventilation unit 50 with which the ceiling surface of the heat exchange chamber 1 was equipped, this invention is applicable also to the ventilation unit with which a side surface is equipped.

It is a perspective view which shows the internal structure of the GHP outdoor unit which concerns on embodiment. It is a front view which shows the internal structure of the GHP outdoor unit which concerns on embodiment. It is a top view which shows the internal structure of the GHP outdoor unit which concerns on embodiment. It is a top view of the propeller fan concerning a 1st embodiment. It is a top view which shows the propeller fan and shroud which concern on 2nd Embodiment. It is a figure which shows the relationship between a tip clearance and a specific noise. It is sectional drawing which looked at the propeller fan and shroud which concern on 3rd Embodiment from the side. It is a figure which shows the relationship between shroud length and specific noise. It is sectional drawing which looked at the propeller fan and shroud which concern on 4th Embodiment from the side. It is sectional drawing which looked at the propeller fan and shroud which concern on 5th Embodiment from the side. It is a figure which shows the relationship between the protrusion amount of a shroud, and a specific noise. It is the perspective view which looked at the air blower in a prior art example from the inner side of the outdoor unit.

Explanation of symbols

15 Propeller fan 15b Blade 50 Blower unit (Blower)
52 shroud 53 enlarged diameter part 54 reduced diameter part 55 bulging part

Claims (5)

In the axial flow type air blower provided with a propeller fan having a plurality of blades,
Each of the blades has a distance from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan to the rotation center of the propeller fan, and a distance from the outer peripheral edge on the downstream side in the rotation direction of the propeller fan to the rotation center of the propeller fan. An air blower characterized by having a different shape. In the blower device according to claim 1,
In each blade, the distance from the outer peripheral edge of the propeller fan in the rotation direction downstream to the rotation center of the propeller fan is set longer than the distance from the outer peripheral edge of the propeller fan in the rotation direction upstream to the rotation center of the propeller fan. The air blower characterized by being made. In the air blower according to claim 1 or 2,
The outer peripheral edge of each blade has a shape in which the distance from the rotation center of the propeller fan continuously changes from the outer peripheral edge on the upstream side in the rotation direction of the propeller fan to the outer peripheral edge on the downstream side in the rotation direction of the propeller fan. The air blower characterized by becoming. In a blower provided with a propeller fan having a plurality of blades and a shroud formed in a cylindrical shape so as to surround the outer peripheral edge of the propeller fan,
The said shroud is equipped with the enlarged diameter part which enlarges an opening area gradually toward the downstream of the ventilation direction accompanying rotation of a propeller fan, The air blower characterized by the above-mentioned. In the air blower according to claim 4,
The shroud includes a reduced diameter portion that is located on the upstream side in the blowing direction from the enlarged diameter portion and gradually decreases the opening area toward the downstream side in the blowing direction. A blower characterized in that a bulging portion bulging toward the center side of the propeller fan is formed at the boundary portion.

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