JP2014077380A - Sirocco fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Sirocco fan capable of achieving both of prevention of leak flow to a suction side of a fan rotor and prevention of degradation of fan performance.SOLUTION: A Sirocco fan 1 includes a fan rotor 3, a housing 2 and a backflow preventing plate 10. The backflow preventing plate 10 prevents air of an outer periphery of the fan rotor 3 from flowing back to a suction side of the fan rotor 3 through a clearance gap 21 between an end ring 17 disposed at an outer periphery of a blade 18 of the fan rotor 3, and an inner wall 20 of a housing body 2a. A length of the backflow preventing plate 10 is determined to a first length H1 which is a length equal to a length from the inner wall 20 of the housing body 2a to a far end 17a far from a suction opening 7 of the end ring 17 in a range excluding a prescribed range near a tongue portion 14 of the housing 2, and determined to a second length H2 longer than the first length H1 in the prescribed range near the tongue portion 14.

Description

  The present invention relates to a sirocco fan.

  In a sirocco fan used for an air conditioner or the like, various sirocco fans have been proposed in the past in order to prevent a leakage flow from the outer periphery side of the fan rotor to the suction side. For example, like a sirocco fan described in Patent Document 1, a sirocco fan in which a fan rotor is rotatably accommodated inside a housing and a cylindrical backflow prevention plate that covers the upper part of the fan rotor from the outer periphery is formed on the housing side. There is. This backflow prevention plate covers the fan rotor end ring and part of the blades below the fan rotor from the outer periphery so that the air around the fan rotor leaks through the gap between the upper end of the fan rotor and the inner wall of the housing. Air is prevented from flowing back to the suction side of the rotor. If the length of the backflow prevention plate is shorter than the length from the suction port side of the inner wall of the housing to the lower end of the end ring, it is not sufficient to prevent leakage flow from the gap between the upper end of the fan rotor and the inner wall of the housing. On the other hand, when the length is longer than the length to the lower end of the end ring, the leakage flow can be prevented, but the fan performance may be deteriorated.

Japanese Patent No. 3649815

  However, in the structure in which the backflow prevention plate is uniformly long over the entire circumference of the fan rotor as in the sirocco fan described in Patent Document 1, the leakage flow between the end ring and the inner wall of the housing is prevented. Then, since it covers to the blade | wing part, there exists a possibility that the performance of a fan may deteriorate.

  The present invention has been made in view of the circumstances as described above, and provides a sirocco fan capable of achieving both prevention of leakage to the suction side of the fan rotor and prevention of deterioration of fan performance. Objective.

  The inventors of the present invention found that the phenomenon in which air flows backward to the suction side of the fan rotor (3) in the portion of the blade (18) below the end ring of the fan rotor (3) is the tongue (14 In the section near the tongue (14), the portion of the blade (18) below the end ring of the fan rotor (3) is covered with the backflow prevention plate (10), If the blade (18) is not covered in the area other than the vicinity of the tongue (14), it is possible to prevent leakage of the fan rotor (3) to the suction side while suppressing deterioration of the fan performance. I found out.

  That is, the sirocco fan of the present invention is a fan rotor (3) rotatable around a rotation axis, and a plurality of blades (18) arranged on the circumference around the rotation shaft, and the blades (18 ) Of the fan rotor (3) having an annular ring portion (17) for connecting the respective suction side ends of each, a housing portion (2a) for housing the fan rotor (3), and the blade (18). A suction port (7) that opens to the end on the suction side and sucks air into the interior of the housing portion (2a) from the outside, is connected to the housing portion (2a), and is connected to the outside from the housing portion (2a). A housing (2) having a discharge pipe part (2b) having an outlet (8) for blowing out air and a tongue part (14) which is a boundary part between the housing part (2a) and the discharge pipe part (2b) And projecting in the direction in which the rotary shaft extends from the inner wall (20) of the portion of the housing (2) where the suction port (7) is formed in the accommodating portion (2a), (17) is disposed so as to surround the outer periphery of the fan rotor (3), the air on the outer periphery of the fan rotor (3) passes through the gap (21) between the ring portion (17) and the inner wall (20) of the housing portion (2a). A backflow prevention plate (10) that prevents backflow of air to the suction side of the fan rotor (3), and the length of the backflow prevention plate (10) in the direction in which the rotating shaft extends is The suction port in the ring portion (17) from the inner wall (20) of the portion where the suction port (7) in the housing portion (2a) is formed within a range other than the predetermined range in the vicinity of the tongue (14) ( 7) is set to a first length (H1) equal to the length from the distal end (17a), which is the far end, and within a predetermined range in the vicinity of the tongue (14). Is set to have a second length (H2) longer than the first length (H1).

  According to such a configuration, since the backflow prevention plate (10) is disposed so as to surround the outer periphery of the ring portion (17) of the fan rotor (3), the backflow prevention plate (10) is provided on the fan rotor (3). The outer periphery of the ring part (17) is covered over the entire periphery. Further, the length of the backflow prevention plate (10) is at least from the inner wall (20) of the portion where the suction port (7) is formed in the housing portion (2a) of the housing (2) when viewed from the direction in which the rotating shaft extends. Since it has the 1st length (H1) which is the length equal to the length from the suction port (7) in the ring part (17) to the distal end (17a) which is a far end, a fan rotor Over the entire circumference of (3), the air on the outer periphery of the fan rotor (3) leaks through the gap (21) between the ring part (17) and the inner wall (20) of the housing (2), and the fan rotor (3) It is possible to prevent air from flowing backward to the suction side. Moreover, the length of the backflow prevention plate (10) is set to be a second length (H2) that is longer than the first length (H1) within a predetermined range near the tongue (14). Therefore, within a predetermined range in the vicinity of the tongue (14), not only the backflow of air through the gap (21) between the ring (17) and the inner wall (20) of the housing (2), but also the ring ( It is possible to effectively prevent the backflow of air generated between the blades (18) at a position farther from the suction port (7) than 17). In addition, within the range other than the predetermined range in the vicinity of the tongue (14), the length of the backflow prevention plate (10) is the ring portion from the suction port (7) side of the inner wall (20) of the housing portion (2a). Since the first length (H1) is set equal to the length to the distal end (17a) of (17), the fan rotor (3 ) It is possible to prevent the backflow prevention plate (10) from obstructing the air flow blown to the outside, and it is possible to suppress a decrease in fan efficiency. As a result, it is possible to achieve both prevention of the fan rotor (3) from leaking to the suction side and prevention of deterioration of the fan performance.

  In addition, the length of the backflow prevention plate (10) is set so as to gradually change in a transition section between the first length (H1) and the second length (H2). preferable.

  According to such a configuration, since the length of the backflow prevention plate (10) is set so as to gradually change in the circumferential direction of the fan rotor (3), there is no portion in which the length suddenly changes. It is possible to suppress the disturbance of the fan, and it is possible to further suppress the decrease in fan efficiency.

  Further, the predetermined range is a range of ± 20 degrees with respect to a circumferential direction of the fan rotor (3) with respect to a direction facing the tongue (14) from the rotating shaft, and within the range of ± 20 degrees The length of the backflow prevention plate (10) is preferably set to be the second length (H2).

  In the range of ± 20 degrees with respect to the circumferential direction of the fan rotor (3) from the rotation axis to the tongue (14), the blade (18) is positioned farther from the suction port (7) than the ring (17). There is a possibility that the backflow of air generated between the two may occur, but according to the above configuration, the backflow prevention plate (10) is within this range up to the second length (H2) longer than the first length (H1). Since it extends, the backflow of air generated between the blades (18) at a position farther from the suction port (7) than the ring portion (17) within a range of ± 20 degrees in the vicinity of the tongue (14) is more effective. It is possible to prevent. On the other hand, it is possible to effectively prevent the backflow prevention plate from obstructing the blowing of air from the fan rotor (3) in other ranges.

  As described above, according to the present invention, it is possible to achieve both prevention of leakage flow to the suction side of the fan rotor and prevention of deterioration of fan performance.

It is a top view which shows the propeller fan concerning embodiment of this invention. It is the II-II sectional view taken on the line of FIG. It is sectional drawing to which the part and the periphery which are separated from the tongue part in the backflow prevention board of FIG. 2 were expanded. It is sectional drawing to which the part of the tongue part vicinity in the backflow prevention board of FIG. 2 and its periphery were expanded. It is a graph which shows the relationship between the length of the backflow prevention board of FIG. 2, and the angle around a rotating shaft.

  Hereinafter, a sirocco fan according to an embodiment of the present invention will be described in detail with reference to the drawings.

  The sirocco fan 1 shown in FIGS. 1 and 2 includes a housing (specifically, a scroll housing) 2 and a fan rotor 3 accommodated in the housing 2. The housing 2 has a bell mouth 4 that forms a suction port 7 described later.

  The fan rotor 3 is connected to the drive shaft S of the motor M, and rotates in the rotation direction D around the rotation axis A in the housing 2 by driving the motor M.

  The housing 2 includes a housing main body 2a and a discharge pipe portion 2b protruding from the side surface of the housing main body 2a. The housing main body 2a and the discharge pipe portion 2b are integrally formed.

  That is, the housing main body 2a and the discharge pipe portion 2b include a front plate 11 provided on the front side F in the axial direction of the rotation axis A of the fan rotor 3, a back plate 12 provided on the back side R, A side plate (body plate) 13 disposed between the face plate 11 and the back plate 12 is joined to form a single body. The housing 2 constitutes a hollow case by these plates 11, 12, and 13.

  The housing body 2a has a housing space 6 in which the fan rotor 3 is housed, and is included in the concept of the housing portion of the present invention. Furthermore, an opening 15 communicating with the accommodation space 6 is formed in a portion of the front plate 11 constituting the housing body 2a. A bell mouth 4 is attached to the opening 15. The bell mouth 4 forms a suction port 7 for allowing air to flow into the accommodation space 6. A specific configuration of the bell mouth 4 will be described in detail in connection with the ring member 5 in a later stage.

  The discharge pipe portion 2b is a portion that is formed in a substantially quadrangular cylindrical shape and projects in the tangential direction of the outer peripheral surface of the housing body 2a from the side surface of the housing body 2a.

  At the boundary portion between the discharge pipe portion 2b and the housing main body 2a, a tongue portion 14 protruding inside the housing 2 is formed. As shown in FIG. 1, the tongue portion 14 is formed by connecting the side surface of the discharge pipe portion 2b and the side surface of the housing body 2a so as to form an acute angle in plan view. The distance between the inner surface of the side plate 13 in the housing 2 and the radially outer end of the fan rotor 3 gradually increases along the rotational direction D from the tongue 14.

  An outlet 8 is formed on the distal end side of the discharge pipe portion 2b to blow out air in the housing space 6 of the housing body 2a to the outside. The blower outlet 8 communicates with the housing space 6 through the internal space of the discharge pipe portion 2b.

  In the housing 2, parts other than the suction port 7 and the air outlet 8 are closed by the front plate 11, the back plate 12, the side plate 13, and the motor M that is fitted to the back plate 12.

  The fan rotor 3 includes a disk-shaped main plate 16 disposed to face the back plate 12 of the housing 2 and a plurality of forward-facing blades (hereinafter referred to as “circular rotation direction D” around the rotation axis A). 18) and an end ring 17 as an annular ring portion that connects the suction side ends of the blades 18 to each other.

  The main plate 16 is connected to the drive shaft S of the motor M via a connecting member 19 and can rotate around the rotation axis A together with the drive shaft S. An end portion on the back side R of each blade 18 is connected to the main plate 16. The length (blade chord length) from the leading edge to the trailing edge of each blade 18 is substantially constant in the axial direction of the rotation axis A. The chord length may gradually increase from the front side F to the back side R.

  The end ring 17 is connected to a portion located on the suction side of the plurality of blades 18 (that is, the front side F in FIG. 2) and located on the outer peripheral side of the blade 18. By connecting the end portions on the front side F of the blades 18 via the end ring 17, the blades 18 are reinforced. The end ring 17 is an annular member having a rectangular cross-sectional shape, and is provided on the outer peripheral edge of the fan rotor 3. In the present embodiment, the fan rotor 3 and the end ring 17 are integrally formed by resin molding. The end ring 17 is included in the concept of the ring portion of the present invention.

  As shown in FIG. 3, the bell mouth 4 includes a cylindrical air guide portion 9, a backflow prevention plate 10 disposed on the outer peripheral side of the air guide portion 9, and the air guide portion 9 and the backflow prevention plate. 10 is provided.

  The air guide portion 9 is a cylindrical portion that is disposed inside the opening 15 of the housing body 2a and has an inner diameter that decreases from the front side F to the back side R of the housing 2. Specifically, the inner peripheral surface 9a of the air guide portion 9 has a curved shape whose inner diameter decreases from the front side F toward the back side R. The air guide portion 25 forms the suction port 7 of the housing 2. The suction port 7 is opened facing the end portion on the suction side (front side F in FIG. 2) of the blade 18 of the fan rotor 3.

  The backflow prevention plate 10 is a direction in which the rotation axis A extends from the inner wall 20 of a portion of the housing body 2a where the suction port 7 is formed in the front plate 11 (specifically, a portion near the edge of the opening 15 of the front plate 11). The cylindrical member protrudes to the end ring 17 and is disposed so as to surround the outer periphery of the end ring 17. The backflow prevention plate 10 prevents the air on the outer periphery of the fan rotor 3 from flowing back to the suction side of the fan rotor 3 through the gap 21 (see FIG. 3) between the end ring 17 and the inner wall 20 of the housing body 2a. To prevent.

  The bell mouth 4 is attached to the opening 15 of the housing body 2a by fitting the cylindrical backflow prevention plate 10 into the opening 15 along the inner peripheral edge of the opening 15 of the housing body 2a. Further, since the bell mouth 4 has an annular flange portion 4a that protrudes radially outward from the outer peripheral surface thereof, the backflow prevention plate is brought into contact with the front plate 11 around the opening 15 by this flange portion 4a. 10 can be positioned so as to protrude into the housing 2 with a predetermined protrusion amount.

  The bell mouth 4 is integrally formed of resin so that the air guide portion 9, the backflow prevention plate 10, and the flange portion 4a are integrated.

  The length of the backflow prevention plate 10 in the direction in which the rotation axis A extends is within a range other than a predetermined range in the vicinity of the tongue portion 14 (particularly, a portion where the suction port 7 is formed in the housing body 2a (see FIG. 3). The first length which is equal to the length from the inner wall 20 of the front plate 11 shown in FIG. 2 to the distal end 17a which is the end far from the suction port 7 in the end ring 17. The height H1 is set to be a second length H2 longer than the first length H1 within a predetermined range near the tongue 14.

  Specifically, as a range other than a predetermined range in the vicinity of the tongue portion 14 shown in FIG. 1, for example, about 40 to 320 degrees with reference to a reference line P connecting the rotation axis A and the tip 14a of the tongue portion 14. In the range θ1 (see FIGS. 1 and 5), the length of the backflow prevention plate 10 is such that the suction port 7 in the housing body 2a is formed in the direction in which the rotation axis A extends, as shown in FIGS. The first length H1 is set to a length equal to the length from the inner wall 20 to the distal end 17a of the end ring 17. 2 to 3, the portion of the backflow prevention plate 10 within the above range θ <b> 1 is denoted by reference numeral 10 a. Thereby, as shown in FIG. 3, the air around the fan rotor 3 is prevented from backflow RF1 of the air generated through the gap 21 between the end ring 17 and the inner wall 20 of the housing body 2a. The first length H1 referred to here is the length from the inner wall 20 of the portion of the housing body 2a where the suction port 7 is formed to the distal end 17a of the end ring 17. In the present invention, the first length H1 It means a length including a position slightly further from or closer to the suction port 7 than the distal end 17a of the end ring 17 in the extending direction of A.

  As shown in FIGS. 1 and 5, the predetermined range in the vicinity of the tongue portion 14 is set to a range θ2 of ± 20 degrees with respect to the reference line P, for example. Within the range θ2 of ± 20 degrees, the length of the backflow prevention plate 10 is set to be a second length H2 that is longer than the first length H1. Specifically, as the range θ2 in the vicinity of the tongue portion 14, a range θ2 of ± 20 degrees is set with reference to the direction in which the reference line P extending from the rotation axis A toward the tongue portion 14 is within the range θ2. As shown in FIG. 4, the length of the backflow prevention plate 10 is set to the second length in order to prevent the backflow RF2 of air generated between the blades 18 at a position farther from the suction port 7 than the end ring 17. It is set to be H2. 2 and 4, the portion of the backflow prevention plate 10 within the range θ2 is indicated by reference numeral 10b. As described above, since the range θ2 set to the second length H2 is set to a range of ± 20 degrees, it is farther from the inlet 7 than the end ring 17 within the range of ± 20 degrees in the vicinity of the tongue portion 14. This prevents the backflow of air that occurs between the blades 18 at the position, and prevents the backflow prevention plate 10 from inhibiting the blowout of air from the fan rotor 3 in other ranges (for example, the range θ1 in FIG. 1). It is possible.

  Here, the range θ2 is arbitrarily set as long as it is within a range of ± 20 degrees with respect to the extending direction of the reference line P facing the tip 14a of the tongue portion 14 from the rotation axis A in the circumferential direction of the fan rotor 3. However, more preferably, it is set within a range of ± 10 degrees, which is the strongest range of backflow of air generated between the blades 18. By setting the range θ2 within the range of ± 10 degrees, it is possible to effectively prevent the backflow of air generated between the blades 18 in a narrower range.

  In the sirocco fan 1 of the present embodiment, the range θ3 sandwiched between the range θ1 and the range θ2 is such that the length of the backflow prevention plate 10 is between the first length H1 and the second length H2. It is set as a range that gradually shifts. In this range θ3, the length of the backflow prevention plate 10 is set so as to gradually change from the first length H1 to the second length H2 or vice versa. As a result, there is no portion where the length of the backflow prevention plate 10 changes suddenly, and the tip shape of the backflow prevention plate 10 continues smoothly, so that the turbulence of the airflow by the backflow prevention plate 10 can be suppressed.

  In the present embodiment, the range θ3 in which the length of the backflow prevention plate 10 changes may be set as appropriate in relation to the range θ2 set to the second length H2, for example, as shown in FIG. Are set in the range of 20 to 40 degrees and 320 to 340 degrees.

  In the sirocco fan 1 configured as described above, when the fan rotor 3 rotates by the driving force of the motor M, external air is sucked into the housing 2 through the bell mouth 4 as shown in the air flow SF of FIG. It is. The air sucked into the housing 2 flows into the fan rotor 3 from the front side F in the axial direction of the rotation axis A toward the rear side R along the direction in which the rotation axis A extends, and the gap 22 between the blades 18. Passes (see FIG. 1) and flows out of the fan rotor 3 radially outward. The outflowed air moves inside the housing main body 2a of the housing 2 along the rotation direction D and is discharged from the outlet 8 of the discharge pipe portion 2b.

  At this time, since the backflow prevention plate 10 covers the entire circumference of the fan rotor 3 with the length of the first length H, the air on the outer periphery of the fan rotor 3 is a gap 21 between the end ring 17 and the inner wall 20 of the housing 2. Air is prevented from leaking through the air and flowing back to the suction side of the fan rotor 3 (see air flow RF1 in FIG. 3).

  At the same time, the backflow prevention plate 10 is set to have a second length H2 that is longer than the first length H1 in a predetermined range in the vicinity of the tongue portion 14. In the range, not only the backflow of air through the gap 21 between the end ring 17 and the inner wall 20 of the housing 2 but also the backflow of air generated between the blades 18 at a position farther from the inlet 7 than the end ring 17 (see FIG. 4). Air flow (see RF2). On the other hand, in the range other than the predetermined range in the vicinity of the tongue portion 14, the backflow prevention plate 10 is set to the first length H <b> 1. This prevents the backflow prevention plate 10 from obstructing. In this way, it is possible to prevent leakage of the fan rotor 3 toward the suction side and to prevent deterioration of the fan performance.

(Feature)
(1)
In the sirocco fan 1 of the present embodiment, the backflow prevention plate 10 is disposed so as to surround the outer periphery of the end ring 17 of the fan rotor 3. It covers the outer periphery. The length of the backflow prevention plate 10 is at least from the inner wall 20 of the portion where the suction port 7 in the housing space 6 of the housing 2 is formed from the suction port 7 in the end ring 17 when viewed from the direction in which the rotation axis A extends. Since it has the first length H1 that is equal to the length to the distal end, which is the far end, air on the outer periphery of the fan rotor 3 is connected to the end ring 17 over the entire periphery of the fan rotor 3. It is possible to prevent air from leaking through the gap 21 with the inner wall 20 of the housing 2 and flowing back to the suction side (front side F in FIG. 2) of the fan rotor 3 (see the air flow RF1 in FIG. 3). It is. In addition, the length of the backflow prevention plate 10 is set to be a second length H2 that is longer than the first length H1 in a predetermined range in the vicinity of the tongue 14, so In a predetermined range, not only the backflow of air through the gap 21 between the end ring 17 and the inner wall 20 of the housing 2 but also the backflow of air generated between the blades 18 at a position farther from the suction port 7 than the end ring 17 (see FIG. 4 air flow RF2) can be effectively prevented. In addition, in a range other than the predetermined range in the vicinity of the tongue portion 14, the length of the backflow prevention plate 10 is from the inner wall 20 of the portion where the suction port 7 is formed in the housing body 2 a to the distal end of the end ring 17. Since the first length H1 is set equal to the length, it is avoided that the backflow prevention plate 10 inhibits the air flow that blows out between the blades 18 in this range and blows to the outside of the fan rotor 3. It is possible to suppress a decrease in fan efficiency. As a result, it is possible to achieve both prevention of leakage to the suction side of the fan rotor 3 and prevention of deterioration of fan performance.

(2)
In the sirocco fan 1 of the present embodiment, the length of the backflow prevention plate 10 is a section θ3 shown in FIGS. 1 and 5, which is a section that transitions between the first length H1 and the second length H2. Is set to change gradually. Thus, since the length of the backflow prevention plate 10 is set so as to gradually change in the circumferential direction of the fan rotor 3, there is no portion where the length changes suddenly, so that the turbulence of the airflow can be suppressed. It is possible to further suppress a decrease in fan efficiency.

(3)
In the sirocco fan 1 of the present embodiment, the length of the backflow prevention plate 10 is within the range of ± 20 degrees with respect to the circumferential direction of the fan rotor 3 with respect to the direction from the rotation axis A toward the tongue portion 14. Since it is set to be H2, the backflow of air generated between the blades 18 at a position farther from the suction port 7 than the end ring 17 within the range of ± 20 degrees in the vicinity of the tongue 14 is more effectively achieved. It is possible to prevent. On the other hand, it is possible to effectively prevent the backflow prevention plate 10 from inhibiting air blowing from the fan rotor 3 in other ranges.

(Modification)
In the above embodiment, an example in which the end ring 17 is formed integrally with the blade 18 of the fan rotor 3 is shown, but the present invention is not limited to this, and the end ring 17 is separated from the blade 18. Then, the end ring 17 may be fixed to the outer periphery of the blade 18. Even in that case, it is possible to achieve the effects of the above-described embodiment.

1 Sirocco fan 2 Housing 2a Housing body (housing part)
2b Discharge pipe part 3 Fan rotor 4 Bell mouth 6 Accommodating space part 7 Suction port 8 Air outlet 10 Backflow prevention plate 17 End ring (ring part)
18 Feather 20 Inner wall

Claims (3)

A fan rotor (3) rotatable around a rotation axis, a plurality of blades (18) arranged on a circumference around the rotation shaft, and respective suction side ends of the blades (18) A fan rotor (3) having an annular ring portion (17) connecting the two to each other;
A housing part (2a) for housing the fan rotor (3), opening facing the suction side end of the blade (18), and a suction port for sucking air from the outside into the housing part (2a) ( 7) a discharge pipe part (2b) connected to the storage part (2a) and having an outlet (8) for blowing air from the storage part (2a) to the outside, and the storage part (2a) and the discharge pipe A housing (2) having a tongue (14) that is a boundary with the portion (2b);
The housing (2) protrudes in an extending direction of the rotary shaft from an inner wall (20) of the housing portion (2a) where the suction port (7) is formed so as to surround the outer periphery of the ring portion (17). The air around the fan rotor (3) is sucked into the fan rotor (3) through the gap (21) between the ring part (17) and the inner wall (20) of the housing part (2a). And a backflow prevention plate (10) that prevents air from flowing back to the side,
The length of the backflow prevention plate (10) in the direction in which the rotating shaft extends is within the range other than the predetermined range in the vicinity of the tongue (14), and the suction port (7) in the housing portion (2a) is formed. The first length (the length equal to the length from the inner wall (20) of the formed portion to the distal end (17a) which is the end of the ring portion (17) far from the suction port (7) ( H1), and within a predetermined range near the tongue (14), the second length (H2) is set to be longer than the first length (H1).
Sirocco fan characterized by that. The length of the backflow prevention plate (10) is set so as to gradually change in a section that transitions between the first length (H1) and the second length (H2).
The sirocco fan according to claim 1. The predetermined range is a range of ± 20 degrees with respect to a circumferential direction of the fan rotor (3) with respect to a direction from the rotary shaft toward the tongue (14), and within the range of ± 20 degrees, The length of the backflow prevention plate (10) is set to be the second length (H2).
The sirocco fan according to claim 1.

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