JP2008069709A - Impeller for centrifugal fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impeller for a centrifugal fan capable of equalizing the wind speed distribution in the blow-out side by suppressing air drift and realizing air capacity increase and low noise. <P>SOLUTION: In an impeller 1 for a centrifugal fan comprising a main plate 2 directly connected to a drive source, a side plate 3 arranged oppositely to the main plate 2 and a plurality of blades 4 arranged circumferentially between these main plate 2 and side plate 3, a plurality of projections 7 of a regular tetrahedron are arranged with a suitable pitch in the width direction near the blow-out side of each blade 4. Also, the projections 7 are arranged respectively on the top surface and the under surface of each blade 4. Further, the layouts of the projections 7 on the top surface and the under surface of each blade 4 are shifted with each other in the blade width direction, the projections 7 of the top surface and the under surface being alternately arranged in the blade width direction, and the number of the projections 7 arranged on the under surface is less than the number of the projections 7 arranged on the top surface by one. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an impeller for a centrifugal fan, in which a plurality of blades are arranged in a circumferential direction between a main plate and a side plate disposed opposite thereto.

  The centrifugal fan is used to blow air to a heat exchanger such as a condenser or an evaporator in an air conditioning facility, for example, and performs a necessary blowing action by rotating the impeller (impeller) in the casing. Is.

  Here, an example of the conventional impeller used for such a centrifugal fan is shown in FIG.

  FIG. 7 is a partial cross-sectional view of a conventional impeller 101. The illustrated impeller 101 includes a flat disc main plate 102 and a short nozzle disc-like side plate disposed opposite to the main plate 102 at a predetermined distance. A shroud) 103 and a plurality of blades 104 (only one is shown in FIG. 7) arranged in the circumferential direction between the main plate 102 and the side plates 103. Although not shown, a boss is provided upright at the center of the shaft of the main plate 102, and an output shaft (motor shaft) of a motor as a driving source is inserted and fixed to the boss. Accordingly, the impeller 101 is directly connected to the motor via the boss.

  In FIG. 7, reference numeral 106 denotes a bell mouth-like inlet fixed to a casing (not shown). The inlet 106 has an outlet end 106 a inserted into the suction port 103 a of the side plate 103 of the impeller 101 and opened. Thus, the air introduced from the air inlet of the casing into the casing is smoothly guided without resistance to the suction port 103a of the side plate 103 of the impeller 101.

  Thus, when a motor (not shown) is started, the impeller 101 directly connected to the motor is driven to rotate at a predetermined speed in a casing (not shown). Then, air is guided to the inlet 106 and introduced into the impeller 101 from the opening 103 a of the side plate 103 of the impeller 101 in the axial direction (horizontal direction in FIG. 7). When passing between the blades 104, a static pressure and a dynamic pressure are applied from the blades 104, and the centrifugal force is applied to move radially outward (upward in FIG. 7) as indicated by an arrow in FIG. The flow direction is changed and the air is discharged from the blower outlet of the impeller 101 into a casing (not shown), thereby performing a required air blowing action by the centrifugal fan.

  By the way, in the air flow in the impeller 101, the air flowing in the axial direction from the suction port 103 a of the side plate 103 is radially outward (upward in FIG. 7) by centrifugal force when passing between the plurality of blades 104. ), The curvature of the air flow increases and the flow velocity decreases as the distance from the side plate 103 increases, and an air vortex is generated in the vicinity of the side plate 103 as shown in the figure.

  Accordingly, since the flow velocity of air flowing into the blades 104 is low in the vicinity of the side plate 103, the wind speed at the blowout port of the impeller 101 is also low, and the flow velocity distribution of air at the blowout port of the impeller 101 is indicated by a broken line in FIG. As shown, the flow rate on the side plate 103 side is significantly lower than the flow rate on the main plate 102 side, leading to a reduction in the blowing performance and efficiency of the centrifugal fan, and a decrease in the flow rate in the vicinity of the side plate 103 There is a problem that the flow separation and turbulence are induced to increase the turbulent noise. In FIG. 6, the horizontal axis represents the air outlet position (mm), and the vertical axis represents the wind speed (m / sec) at the air outlet of the impeller at a rotational speed of 500 rpm.

  Incidentally, in Patent Document 1, in order to achieve uniform wind speed distribution and low noise in the impeller, the thickness of the blades is gradually increased from the side plate toward the main plate, and Proposals have been made to gradually reduce the adjacent distance from the side plate toward the main plate.

Further, in Patent Document 2, by arranging parallel protrusions or V-shaped protrusions on the pressure surface side near the inlet side of the blade, a large number of minute separation vortices are generated behind the protrusions to generate a large vortex flow. Proposals have been made to prevent and suppress broadband noise.
JP 2001-132687 A JP 2001-263295 A

  However, the configuration proposed in Patent Document 1 has a problem that the maximum airflow is reduced because the space on the main plate side with a large flow rate is narrowed.

  Further, in the configuration proposed in Patent Document 2, interference between the flow on the upper surface (positive pressure surface) and the flow on the lower surface (negative pressure surface) of the blade is suppressed, and the above effect is achieved. It is impossible to expect the effect of increased air volume.

  The present invention has been made in view of the above problems, and its objective is to provide a centrifugal fan that can suppress air drift and uniformize the wind speed distribution on the outlet side, thereby increasing the air volume and reducing noise. It is to provide an impeller.

  In order to achieve the above-mentioned object, the invention described in claim 1 includes a main plate directly connected to a drive source, a side plate disposed opposite to the main plate, and a plurality of plates arranged in the circumferential direction between the main plate and the side plate. A centrifugal fan impeller having a single blade is characterized in that a plurality of regular tetrahedron projections are arranged at an appropriate pitch in the width direction in the vicinity of the blowing side of each blade.

  According to a second aspect of the present invention, in the first aspect of the present invention, the protrusions are arranged on the upper surface and the lower surface of each wing.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the arrangement positions of the protrusions are shifted in the wing width direction on the upper surface and the lower surface of each wing, and the protrusions are alternately shifted in the wing width direction on the upper surface and the lower surface. The number of protrusions disposed on the lower surface is one less than the number of protrusions disposed on the upper surface.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the length a of one side of the regular tetrahedron of each projection is a = (1.5 -3.0%) C.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the arrangement pitch P of the protrusions is P = (11.0 to 18.0%) H with respect to the blade width H. It is characterized by being set to.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the arrangement position D of the protrusion from the trailing edge of the blade is set to D = (5.0 to 15.0%) C.

  According to the first aspect of the present invention, the air flowing in the axial direction from the suction port of the side plate of the impeller is given a static pressure and a dynamic pressure from the blades when passing between the plurality of blades, and is centrifuged. In response to the force, it changes the flow outward in the radial direction and is discharged from the blower outlet of the impeller, but the flow of air by the rectifying action of a plurality of projections made of tetrahedrons arranged in the vicinity of the blowout side of each blade Is rectified, the vortex generated on the side plate side disappears, the air drift is suppressed, the wind speed distribution on the blowing side is made uniform, and the air volume is increased and the noise is reduced.

  According to the second aspect of the present invention, since the protrusions are arranged on the upper and lower surfaces of each wing, the air flow along the upper and lower surfaces of each wing is rectified by the rectifying action of the protrusions, and along the upper and lower surfaces of each wing. The uneven flow of air is suppressed, and the wind speed distribution on the outlet side is made uniform.

  According to the third aspect of the present invention, the protrusions are displaced in the blade width direction on the upper and lower surfaces of each blade, and the protrusions are alternately disposed in the blade width direction on the upper and lower surfaces. Disturbances due to interference when the airflows flowing along the airflow merge at the air outlets of the blades are prevented, and an increase in noise associated with the disturbances is prevented.

According to the third to fifth aspects of the present invention, the length a of one side of the regular tetrahedron of the protrusion, the pitch P of the protrusion, and the position D of the protrusion from the trailing edge of the blade are determined by the experiment. For H
a = (1.5-3.0%) C
P = (11.0-18.0%) H
D = (5.0-15.0%) C
By setting each of the above, a high rectification effect by the protrusion can be obtained, and the above-described effect according to the first to third aspects can be obtained.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 is a perspective view of an impeller for a centrifugal fan according to the present invention, FIG. 2 is a partial sectional view of the impeller, FIG. 3 is a view in the direction of arrow A in FIG. 2, and FIG. 5 is a partial sectional view showing the air flow state in the impeller according to the present invention, and FIG. 6 shows the wind speed distribution at the outlet of the impeller according to the present invention in comparison with that in the conventional impeller. FIG.

  As shown in FIG. 1, an impeller 1 for a centrifugal fan according to the present invention includes a flat disk main plate 2 and a short nozzle disk-shaped side plate (shroud) 3 disposed opposite to the main plate 2 at a predetermined distance. And a plurality of (seven in the illustrated example) blades 4 arranged in the circumferential direction between the main plate 2 and the side plates 3. A frustoconical boss 5 is erected at the center of the shaft of the main plate 2, and an output shaft (motor shaft) of a motor (not shown) as a drive source is inserted and fixed to the boss 5. Therefore, the impeller 1 is directly connected to a motor (not shown) that is a drive source via the boss 5.

  In FIG. 5, reference numeral 6 denotes a bell mouth-like inlet fixed to a casing (not shown). The inlet 6 has an outlet end 6 a inserted into a suction port 3 a of the side plate 3 of the impeller 1. Thus, the air introduced into the casing from the air inlet of the casing (not shown) is smoothly guided to the inlet 3a of the side plate 3 of the impeller 1 without resistance.

  Thus, in the impeller 1 according to the present embodiment, as shown in FIG. 2, a plurality of projections 7 made of a regular tetrahedron are provided in the blade width direction (in FIG. 2) in the vicinity of the blowing side of each blade 4. They are arranged at an appropriate pitch P in the vertical direction. As shown in FIG. 3, these protrusions 7 are arranged on the upper surface 4a and the lower surface 4b of each blade 4, and the positions of the protrusions 7 on the upper surface 4a and the lower surface 4b of each blade are in the blade width direction. The protrusions 7 are staggered in the blade width direction on the upper surface 4a and the lower surface 4b of each blade 4 and shifted by P / 2. Here, the number of projections 7 arranged on the lower surface 4b of each blade 4 is set to a value one less than the number of projections 7 arranged on the upper surface 4a.

That is, as shown in FIGS. 2 and 3, when the blade width is H, the number n _{1 of the} projections 7 arranged on the upper surface 4a of each blade 4 and the number n _{2 of the} projections 7 arranged on the lower surface 4b. In the meantime, the following relational expression holds.

n ₂ = H / P-1 <n ₁ = H / P (1)
In this embodiment, the numbers n ₁ = 7 and n ₂ = 6 are set (see FIG. 3).

2 to 4, when the length of one side of the regular tetrahedron of the projection 7 is a, the arrangement pitch of the projection 7 is P, and the arrangement position of the projection 7 from the rear edge of the blade 4 is D. By experiment, these values of a, P and D are relative to the blade length C or the blade width H.
a = (1.5-3.0%) C
P = (11.0-18.0%) H (2)
D = (5.0-15.0%) C
Is set to a value that satisfies the above range.

  The impeller 1 configured as described above is rotationally driven at a predetermined speed in the direction of arrow R in FIG. 1 in a casing (not shown) when a motor (not shown) is started. Then, air is guided to the inlet 6 and is introduced in the axial direction (horizontal direction in FIG. 5) from the opening 3 a of the side plate 3 of the impeller 1 into the impeller 1. When passing between the blades 4, static pressure and dynamic pressure are applied from the blades 4, and receive a centrifugal force and radially outward (upward in FIG. 5) as indicated by an arrow in FIG. 5. The flow is changed to a substantially right angle and discharged from a blower outlet of the impeller 1 into a casing (not shown), whereby a required air blowing action is performed by a centrifugal fan.

  Thus, in the impeller 1 according to the present invention, the air flow is indicated by arrows in FIG. 5 by the rectifying action of the plurality of projections 7 formed of a regular tetrahedron disposed in the vicinity of the blowing side of each blade 1. The vortex generated on the side plate 103 side of the conventional impeller 101 shown in FIG. 7 disappears, the air drift is suppressed, the wind speed distribution on the blowout side is made uniform, the air volume increases and the noise is reduced. Realized. Here, in FIG. 6, the wind speed distribution at the air outlet when the rotational speed of the impeller 1 according to the present invention is 500 rpm is shown by a solid line, but in the conventional impeller 101 shown in FIG. 7 that rotates at the same speed. As is clear from comparison with the speed distribution (shown by broken lines), according to the impeller 1 of the present invention, the drop in the wind speed on the side plate 3 side is recovered, and the wind speed distribution is spread over the entire blade width. It can be made substantially uniform. Specifically, the difference between the maximum and minimum wind speeds is ± 50% in the past, whereas the impeller 1 according to the present invention can reduce the wind speed difference to ± 25% that is 1/2 of the conventional speed. Moreover, the noise could be reduced by about 1 dB.

  In particular, in the impeller 1 according to the present invention, since the projections 7 are arranged on the upper surface 4a and the lower surface 4b of each blade 4, the air flow along the upper surface 4a and the lower surface 4b of each blade 4 is caused by the rectifying action of the projection 7. The air flow is rectified, and the drift of air along the upper and lower surfaces 4a and 4b of each blade 4 is suppressed, so that the wind speed distribution on the blowing side is made more uniform.

  Furthermore, according to the impeller 1 according to the present invention, the position of the projection 7 is shifted in the blade width direction by P / 2 between the upper surface 4a and the lower surface 4b of each blade 4, and the upper surface 4a and the lower surface 4b of each blade 4 are shifted. Since the protrusions 7 are arranged alternately in the blade width direction (see FIG. 3), the air flow flowing along the upper and lower surfaces 4 a and 4 b of each blade 4 is disturbed by interference when the air flows merge at the air outlet of each blade 4. This prevents the increase in noise caused by disturbance.

  In addition, the length a of one side of the regular tetrahedron 4 of the projection 4, the arrangement pitch P of the projection 7, and the arrangement position D of the projection 7 from the trailing edge of the blade 4 are determined with respect to the blade length C and the blade width H. Since the setting is made as in the formula (2), a high rectification effect by the protrusions 7 can be obtained, the above-described effect can be stably obtained, and an effect that a rectification component is not required in an application product can be obtained.

  INDUSTRIAL APPLICABILITY The present invention is suitable for an air conditioner equipped with a heat exchanger or a filter on the outlet side of a centrifugal fan, a device that requires rectification such as an air cleaner, and the like.

It is a perspective view of the impeller for centrifugal fans concerning the present invention. It is a fragmentary sectional view of the impeller for centrifugal fans concerning the present invention. It is a figure of the arrow A direction of FIG. It is the B section enlarged detail drawing of FIG. It is a fragmentary sectional view which shows the flow state of the air in the impeller for centrifugal fans which concerns on this invention. It is a figure which shows the wind speed distribution in the blower outlet of the impeller which concerns on this invention in contrast with that of the conventional impeller. It is a fragmentary sectional view which shows the flow state of the air in the conventional impeller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal fan impeller 2 Main plate 3 Side plate 3a Side plate suction port 4 Wings 4a Top surface of blades 4b Bottom surface of blades 5 Boss 6 Inlet 6a Outlet end of inlet 7 Projection a Length of one side of tetrahedron of projection C Blade length D Projection position from the trailing edge of the blade H Blade width P Projection pitch

Claims (6)

In a centrifugal fan impeller comprising a main plate directly connected to a drive source, a side plate opposed to the main plate, and a plurality of blades arranged in the circumferential direction between the main plate and the side plate,
A centrifugal fan impeller comprising a plurality of regular tetrahedron protrusions arranged at an appropriate pitch in the width direction in the vicinity of the blowing side of each blade.   The impeller for a centrifugal fan according to claim 1, wherein the protrusions are arranged on the upper surface and the lower surface of each blade.   The positions of the protrusions are shifted in the wing width direction on the upper surface and the lower surface of each wing, the protrusions are alternately disposed in the wing width direction on the upper surface and the lower surface, and the number of protrusions disposed on the lower surface is disposed on the upper surface. The centrifugal fan impeller according to claim 1 or 2, wherein the number of protrusions is one less than the number of protrusions.   The length a of one side of the regular tetrahedron of each projection is set to a = (1.5 to 3.0%) C with respect to the blade length C. 4. An impeller for a centrifugal fan according to claim 1.   5. The centrifugal fan according to claim 1, wherein the pitch P of the protrusions is set to P = (11.0 to 18.0%) H with respect to the blade width H. 6. Impeller.   The arrangement position D from the trailing edge of the wing of the projection is set to D = (5.0 to 15.0%) C with respect to the wing length C. 6. The impeller for centrifugal fans described in 1.

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