JPH07279893A - Fan - Google Patents

Abstract

PURPOSE:To lower high dimensional noise with a minimum cost-up without increasing the weight of a fan and deteriorating compactness. CONSTITUTION:Several ridge-like protrusions 3 are formed on a negative pressure surface of a blade 2 constituting a fan 1a such as a propeller fan, a turbofan, a sirocco fan and a tangential fan, and on a part or the entire area of one of the inner surface of a casing, a shroud surface and a bellmouth surface. With this arrangement, turbulent in flow on the wall surface of the blade can be reduced with a simple construction in which the ridge-like protrusions 3 are provided, thereby it is possible to reduce pressure variation on the wall surface, which causes generation of noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a fan such as a propeller fan, a turbo fan, a sirocco fan and a tangential fan used in an air conditioner and general industrial products.

[0002]

2. Description of the Related Art A propeller fan is often used as a cooling device in an outdoor unit of an air conditioner and also in general industrial products. Generally, FIG. 17 (a),
As shown in (b), a propeller fan a is connected to an output shaft (not shown) of a motor or the like, and the propeller fan a is provided in a bell mouth (or orifice) casing b so that the suction side and the discharge side are provided. It is arranged to be separated from the side.

When the propeller fan a is rotated by the driving force of the motor, the blade c of the propeller fan a sucks in air as a blowing fluid from the suction side and blows it out from the discharge side.

By the way, since this type of fan is often used in an outdoor unit of an air conditioner, a ventilation fan, etc., it is required to be lightweight and compact. Therefore, the propeller fan is usually made of a plastic thin plate.
The blade c has a circular arc shape and has a substantially uniform plate thickness. In addition, the blade c does not overlap with the adjacent blade c.
It has a highly productive structure.

In addition to the above requirements, fans are required to reduce noise. In terms of this noise, the noise generated by the propeller fan is broadly classified into wide band noise and discrete frequency noise. Broadband noise is dominant in low-voltage fans such as those for air conditioning.

This broadband noise is generated by the upstream flow, the pressure fluctuation on the blade surface and the vortex emitted from the trailing edge of the blade. Conventionally, in order to reduce this broadband noise, the chord length is made as long as possible to reduce and disperse the blade load, and the forward inclination is made to reduce the accumulation of the boundary layer at the trailing edge. There is.

[0007]

However, the required level for noise reduction is insufficient only by the above measures, and further noise reduction is required. Therefore,
As a measure, make the blade cross section an airfoil and control the boundary layer on the blade surface to reduce separation or turbulence on the blade surface,
As a result, it has been proposed to reduce the discharge vortex from the trailing edge of the blade to reduce noise.

However, in the case of forming an airfoil, the blade cross section must be thickened. This leads to an increase in fan weight and an increase in cost. Also, considering resin molding, the above problem is unavoidable because there is a molding limit wall thickness that can be mass-produced in consideration of sink marks.

Therefore, it is difficult to put this airfoil fan into practical use, and there is a limit to noise reduction. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fan that can realize high-dimensional noise reduction without impairing weight reduction and size reduction.

[0010]

In order to solve the above-mentioned problems, the fan according to claim 1 is a negative pressure surface of a blade constituting a fan such as a propeller fan, a turbo fan, a sirocco fan and a tangential fan. Similarly, a large number of streak projections are provided along the flow direction of the blowing fluid on one part or the entire area of the inner surface of the casing, the shroud surface, and the bellmouth surface.

In addition to the above-mentioned object, in the fan described in claim 2, the direction of the streak according to claim 1 is ± 30 ° with respect to the flow direction of the blast fluid in order to obtain higher noise.
It has been set within.

In addition to the above object, in order to obtain a higher noise level, the fan according to claim 3 has the streak height according to claim 1 or 2 from 0.1 to 1. It has been set to 0 mm.

[0013]

According to the fan of the first aspect, the presence of a large number of streak-like protrusions suppresses the turbulence of the wall surface.
At this time, the wall turbulence is correlated with the wall pressure fluctuation,
The smaller turbulence on the wall means that the pressure fluctuation on the wall is also smaller.

Since the sound pressure generated from the wall surface of the blade is caused by the pressure fluctuation of the wall surface, the reduction of the turbulence of the wall surface leads to the reduction of the generated sound. Further, since only a large number of streak projections are provided on the load surface of the blade, it is easy to put into practical use, and the increase in fan weight and cost is suppressed.

According to the fan of the second aspect, when the direction of the streak is within ± 30 ° with respect to the flow direction of the blowing fluid, it is confirmed by experiments that a high noise reduction effect can be obtained. Brings higher noise reduction.

According to the fan of claim 3, when the height of the streak is 0.1 to 1.0 mm, the wall friction on the load surface, which is considered to increase the frictional force with the wall, is experimentally determined. , It was confirmed that the reduction.

That is, on the loading surface of the blade, the flow velocity is extremely low in the valley between the streak and the streak,
Furthermore, the shear stress is also very small. Further, it can be seen that the shear stress becomes very large at the tip of the crest of the streak, which reduces the wall friction force.

This reduction of the wall friction force not only improves the performance (efficiency) but also reduces noise, and in combination with the suppression of turbulence, it results in higher noise reduction. In particular, when combined with the action due to the direction of the streak, a higher noise level can be obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the first embodiment shown in FIGS. FIG. 1 is a front view and a bottom view of a fan to which the present invention is applied, for example, a propeller fan 1a, in which 1 is a short columnar boss portion and 2 is an outer peripheral surface of the boss portion 1 provided at a predetermined interval. A plurality of blades (only one is shown).

A large number of streaky protrusions 3 are provided on the entire area (entire) of the load surface 2a of each blade 2 along the flow direction of the blast fluid. For example, as shown in FIG. 2, the streak projection 3 has a streak shape having a triangular mountain-shaped cross section.
A large number of the streak projections 3 are arranged side by side through the valley.

The direction (angle) of these streak projections 3 is set within ± 30 ° with respect to the flow direction of the blowing fluid. The height dimension δ of these streak projections 3 (shown in FIG. 2)
Is set to 0.1 to 1.0 mm.

The streaky projections 3 provide the propeller fan 1a with higher performance (performance) and high-dimensional low-noise performance while ensuring weight reduction and compactness.

That is, when the propeller fan 1a is rotated by receiving a driving force of a motor (not shown),
The blade 2 rotating around the boss portion 1 sucks in air as a blowing fluid from the suction side and blows it out from the discharge side.

At this time, looking at the load surface 2a of each blade 2, in the valley between the streak 3 and the streak 3, the flow velocity is very low and the shear stress is also very small. . At the tip of the crest of the streak 3, there is a behavior that the shear stress becomes extremely large.

The wall surface disturbance on the load surface 2a is suppressed by the large number of streak projections 3 exhibiting such behavior. Here, since the wall turbulence is correlated with the wall pressure fluctuation, the reduction of the wall turbulence means that the wall pressure fluctuation is also reduced.

That is, the sound pressure generated from the wall surface of the blade is caused by the pressure fluctuation of the wall surface. Therefore, when the turbulence of the wall surface is reduced, the generated sound is reduced. This means that many streak 3
It is possible to provide the propeller fan 1a which is excellent in low noise by a simple structure such as the provision of a fan and a structure in which the increase in fan weight and cost is suppressed to a minimum.

Moreover, a high noise reduction effect can be obtained by setting the direction of the linear projections 3 within an angle of "± 30 °" with respect to the flow direction of the blowing fluid. That is, as a result of investigating the influence of the flow direction on the wall surface and the direction of the streak projections 3 on noise in the blade element test (when δ = 0.25 mm), as shown in FIG. It was confirmed that when the angle θ with the direction is up to about 30 °, it has a noise reduction effect.

It can also be said that this is convenient for the change of the flow pattern on the blade surface when the operating point of the propeller fan 1a is variously changed. This means that the direction of the streak 3 should be aligned with the flow pattern at the most frequently used fan operating point (for example, the highest efficiency point) (allowance depending on the angle range).

In addition, the height dimension δ of the streak 3 is set to "0.
High performance (efficiency) by setting 1 to 1.0 mm "
It is possible to obtain a high noise reduction effect while obtaining the above. That is, as a result of investigating the influence of the height dimension δ of the streak 3 on the fan performance and noise by the test, as shown in FIG. 3, when the height dimension δ of the streak 3 is 0.05 mm, the blade surface Since it is very small compared to the boundary layer, there is almost no difference in performance from a smooth surface propeller fan (having a smooth blade surface without streaks 3) and the height dimension δ is 1 At 0.0 mm, since it is generally the same as the so-called blade surface having a large surface roughness, it can be seen that the wall friction increases and the fan performance (efficiency) decreases.

On the other hand, when the height dimension δ of the streak projections 3 is "0.1 mm <δ <1.0 mm", there is no performance deterioration, but rather the wall frictional force is reduced by about 5-8%, which is slightly The performance improvement was confirmed.

This decrease in the wall friction force not only improves the fan performance (efficiency) but also reduces noise.
In combination with the suppression of turbulence, it brings about higher noise reduction.
Especially when combined with the action of the direction of the streak,
High noise reduction is obtained.

According to the experiment, the noise reduction of 2 dB (A) or more due to the reduction of the wall disturbance is obtained. It should be noted that, instead of the streak-like projections shown in the first embodiment, a large number of streak-like projections 3 having triangular cross sections with different pitches as shown in FIG. 5A, as shown in FIG. 5B. Numerous streak projections 3 having an arcuate valley, many streak projections 3 having an arc-shaped tip as shown in FIG. 5 (c), as shown in FIG. 5 (d). It is also possible to use a large number of streak protrusions 3 having a triangular cross section in which the angle α on one side of the apex angle and the angle β on the other side are different.

Of course, at this time, the streak-like projections 3 are attached to the load surface 2a.
Even if it sticks out from the surface or is flush with the surface, the same effect can be obtained. Further, in the first embodiment, the streaky protrusions 3 are provided on the entire load surface 2a of the blade 2, but the present invention is not limited to this and, for example, FIG.
It may be provided on a part of the load surface 2a as shown in FIG.

That is, these are made to correspond to the case where the noise generated in the tip portion contributes greatly. FIG. 6 shows an example in which the streak projections 3 are provided on the outer peripheral side, and FIG. FIG. 8 shows an example in which the linear protrusions 3 are provided, and FIG. 8 shows an example in which the linear protrusions 3 are provided near the boss portion 1.

Even in this case, the same effect as that of the first embodiment can be obtained. 9 and 10 show a second embodiment of the present invention.
An example of is shown. This embodiment is an example applied to a turbo fan (centrifugal fan) 10, and among the boss portion 11, the impeller 12 and the shroud 13 that constitute the turbo fan 10, the above-mentioned streak projection 3 is formed on the inner surface of the shroud 13. Is provided. In addition, 14 shows a suction bell mouth.

On the inner surface of the shroud of the turbo fan 10, the flow of the blowing fluid is greatly disturbed due to the sharp bend from the bell mouth 14, which causes noise. Therefore, a large number of streak-like projections 3 are provided on the inner surface of the shroud along the air blowing direction to reduce noise due to the reduction in the turbulence of the air blowing fluid, as in the case of the first embodiment.

Of course, like the third embodiment shown in FIG. 11, the stripe-shaped projections 3 are formed on the entire area (or part) of the negative pressure surface 12b of the blade 12a constituting the impeller 12 along the flow direction of the blowing fluid. May be provided. By doing so, the same operational effects as the propeller fan described in the first embodiment can be obtained.

12 and 13 show the fourth embodiment of the present invention.
An example of is shown. This embodiment is a modification of the second embodiment, and is the outlet portion 15a of the casing 15 of the turbo fan 10.
The streaky protrusions 3 are provided on the inner surface of the casing constituting the above, along the flow direction of the blowing fluid.

The casing 15 has a role of collecting the flow from the impeller 12, recovering the static pressure, and blowing out in a fixed direction.
Here, the flow in the casing 15 is greatly disturbed near the wall surface near the outlet where the static pressure is recovered, and noise is generated.

Therefore, as shown in FIG. 13, a large number of streak-like projections 3 are provided on the inner surface of the casing along the air blowing direction, and the flow in the vicinity of the wall surface is the same as that described in the first embodiment. The turbulence is reduced to reduce the generated noise.

The nose 1 where the casing 15 and the impeller 12 are closest to each other where the pressure fluctuation is large
Even if it is provided in 5d, the same effect can be obtained. Of course, although not shown, the streak projections 3 may be provided on the entire inner surface of the casing.

FIG. 14 shows a fifth embodiment of the present invention.
In this embodiment, streak-like protrusions are provided along the flow direction on the suction bell mouth which constitutes the fan.

Specifically, in the fifth embodiment, a large number of streaky protrusions 3 are provided along the flow direction on the surface of the suction bell mouth 20 arranged around the blades 2 constituting the propeller fan 1a.

That is, the noise of the fan becomes extremely large when there is turbulence upstream. The suction bell mouth 20 becomes one of the occurrences of turbulence on the upstream side. Therefore, the streak 3 is provided on the surface of the suction bell mouth 20 to reduce the disturbance on the bell mouth and reduce the noise.

FIG. 15 shows a modification of the sixth embodiment, which is a case of a turbo fan (centrifugal fan) instead of a propeller fan.
The suction bell mouth 14 provided on the sing 15 is provided with a large number of streak projections 3 along the flow direction on the surface thereof. Even in this case, a similar noise reduction effect can be obtained.

FIG. 16 shows the seventh embodiment of the present invention, in which the outlet portion 21a of the impeller 20, casing 21, and stabilizer 22 constituting the tangential fan (throughflow fan) 20a is constituted. -A large number of streak-like projections 3 are provided on the inner surface of the sing 21 in the flow direction, and the same noise reduction effect can be obtained in this way as well.

Also in the sirocco fan having the same structure as the tangential fan 20a, a large number of streak projections 3 are formed along the flow direction on the inner surface of the casing forming the outlet.
By providing, the same noise reduction effect is achieved.

However, regarding the structure of the sirocco fan,
Since it is almost the same as the tangential fan, the diagram showing the configuration is omitted. In addition, in the above-described embodiment, an example in which the streak projection is provided in one of the portions where the turbulence of the flow of the fan greatly appears has been described, but the present invention is not limited to this, and it is provided in two or more portions where the turbulence of the flow appears. Alternatively, it is only necessary to provide streak-like projections on the surface of the component where the flow disturbance is generated.

[0049]

As described above, according to the invention described in claim 1, the turbulence of the flow on the wall surface of the blade can be reduced. As a result, it is possible to reduce the pressure fluctuation on the wall surface, which is a cause of noise generation, and to increase the fan weight, with a simple configuration in which a large number of streak projections are provided on the load surface of the blade.
High-dimensional noise reduction can be realized without impairing the compactness and suppressing the cost increase to the minimum.

According to the invention described in claim 2, it has been confirmed that a high noise reduction effect can be obtained in addition to the above effects.
Brings higher noise reduction. According to the invention as set forth in claim 3, in addition to the above effect, it is possible to reduce the wall friction on the load surface which is considered to increase the frictional force with the wall surface, and the reduction of the wall friction improves the performance (efficiency) and noise. Bring about a reduction.

[Brief description of drawings]

FIG. 1A is a front view of a propeller fan that is a main part of a first embodiment of the present invention. (B) is a bottom view showing the streak-like protrusions on the load surface of the propeller fan.

FIG. 2 is a cross-sectional view showing streaky protrusions of a blade along line AA in FIG. 1 (b).

FIG. 3 is a diagram showing a correlation between a protrusion height of a streak on a load surface of a blade, a relative sound pressure level, and a relative fan static pressure efficiency obtained by a test.

FIG. 4 is a diagram showing the correlation between the angle of the streak and the relative sound pressure level with respect to the flow direction of the blowing fluid.

FIG. 5 is a cross-sectional view showing an example of another streak.

FIG. 6 is a front view showing an example in which streak projections are provided on the outer peripheral side of the blade.

FIG. 7 is a front view showing an example in which streak projections are provided on the trailing edge side.

FIG. 8 is a front view showing an example in which streaky protrusions are provided around the boss portion.

FIG. 9 is a sectional view showing a turbo fan which is a main part of a second embodiment of the present invention.

FIG. 10 is a cross-sectional view showing the inner surface of the shroud taken along the line BB in FIG.

FIG. 11 is a perspective view showing a turbo fan which is a main part of a third embodiment of the present invention.

FIG. 12 (a) is a front view of a turbo fan which is a main part of a fourth embodiment of the present invention. (B) is sectional drawing of the turbo fan.

FIG. 13 is a sectional view of the casing exit side taken along the line CC in FIG.

FIG. 14A is a front view of a fan showing a bell mouth surface with streaky protrusions, which constitutes a fan that is an essential part of a fifth embodiment of the present invention. (B) is sectional drawing of the same fan.

FIG. 15 is a front view showing a bell mouth surface with streaky protrusions, which constitutes a turbofan, which is a main part of a sixth embodiment of the present invention.

FIG. 16 is a perspective view showing an inner surface of a casing with streaky protrusions, which constitutes a tangential fan, which is a main part of a seventh embodiment of the present invention.

FIG. 17 (a) is a front view showing a conventional propeller fan. (B) is sectional drawing of the same propeller fan.

[Explanation of symbols]

1a ... Propeller fan 1 ... Boss part
2 ... blade 2a ... load surface 3 ... streak 1
0 ... Tarbo fan 20a ... Tangential fan

Claims (3)

[Claims] 1. A part of one of a suction surface of a blade, a inner surface of a casing, a shroud surface, and a bellmouth surface of a blade constituting a fan such as a propeller fan, a turbo fan, a sirocco fan, and a tangential fan. Alternatively, the fan is characterized in that a large number of streak-like projections are provided in the entire area along the flow direction of the blowing fluid. 2. The fan according to claim 1, wherein the direction of the streak is within ± 30 ° with respect to the flow direction of the blowing fluid. 3. The height of the streak is 0.1 to 1.0 mm.
The fan according to claim 1 or 2, wherein