JP3729693B2 - Centrifugal blower impeller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a configuration of an impeller for the purpose of improving the performance of a centrifugal blower used in a rotating electric machine, an air conditioner, or the like.
[0002]
[Prior art]
Impellers such as axial flow, centrifugal flow, and diagonal flow are used according to the required air blowing characteristics (pressure, air volume, noise, efficiency, etc.). Centrifugal impellers are characterized by high radial pressure and high static pressure, and are widely used for cooling fans, air conditioners, and equipment. However, in order to improve the performance of these devices, a larger air volume is required, and high efficiency and a large air volume in a centrifugal impeller are required. In order to increase the air volume, it is necessary to increase the impeller size or increase the rotational speed, but these go against product miniaturization, energy saving, and noise reduction. Several methods for improving performance such as blowing and noise due to the impeller shape have already been proposed. As an example, a sectional view of a conventional centrifugal impeller disclosed in Japanese Patent Laid-Open No. 11-82382 is shown in FIG. In the figure, 101a is a shroud, 101b is a main blade, and 101c is a main plate. FIG. 15 is a cross-sectional view of the main blade 101b viewed from a cross section of the cylindrical surface EE having a radius r in the vicinity of the impeller entrance in FIG. 14, and uses a substantially constant inclination angle αe with respect to the rotation axis. In the above conventional example, the blade inclination angle is set by the angle of the combined vector of the axial flow and the impeller rotational speed at the blade inlet radius, and the cross-sectional shape perpendicular to the rotating shaft is made the same, thereby separating on the shroud 101a side. Is to improve the performance of the impeller by making the inlet velocity distribution uniform.
[0003]
[Problems to be solved by the invention]
However, since the impeller as seen in the conventional example has a very strong shape with three-dimensionality, there is a drawback that a high-cost slide mold is used and the number of blades is limited. It was.
[0004]
The present invention has been made to solve the above problems, and provides an inexpensive impeller having a simple blade shape, a large air volume and a low noise level.
[0005]
[Means for Solving the Problems]
The centrifugal blower according to the present invention impeller of the main plate and the blade and the locus center of the circle is drawn inscribed continuous with the tip, the locus drawn by the inscribed circle center definitive the intersection between the edge of the blade The trailing edge angle formed between the tangent and the normal of the trailing edge of the blade is in the range of about 20 ° to about 60 °.
[0006]
Further, a shroud is provided at the blade tip of the blade.
[0007]
A casing is provided outside the blade.
[0008]
Further, a casing is provided outside the shroud.
[0009]
Further, the outer diameter of the shroud is 1.1 times or more than the maximum blade diameter.
[0010]
Further, a casing is provided outside the shroud, and the outer diameter of the shroud is 1.1 times or more than the maximum blade diameter.
[0011]
Further, the shroud outer diameter is 1.1 times or more with respect to the blade maximum diameter, and the outer periphery of the shroud extending outward from the blade maximum diameter faces the radial direction.
[0012]
Also, a casing is provided outside the shroud, and the outer diameter of the shroud is 1.1 times or more than the maximum blade diameter, and the outer periphery of the shroud extends outward from the maximum blade diameter and faces the radial direction. It is.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
A first embodiment of the present invention will be described below with reference to FIG. In the figure, 1 is a centrifugal impeller, 1a is a shroud, 1b is a blade, 1c is a main plate, 1d is a blade tip, 2 is a trajectory (streamline), 3 is a shroud side casing, and 3a is a casing inner diameter portion. Reference numeral 5 denotes a gap between the casing inner diameter portion 3a and the shroud 1a. In the meridional section of the impeller 1, a plurality of circles inscribed between the main plate 1 c and the shroud 1 a are drawn, and the locus 2 drawn by the center of the circle is substantially equal to the streamline 2 of the airflow. The point of intersection between this path and the blade trailing edge and the blade effective outer diameter D _2. The angle formed between the tangent of the locus drawn by the center of the inscribed circle at the intersection and the normal of the trailing edge of the blade is defined as θ.
[0014]
The experiment was performed by changing the blade trailing edge angle θ so that the blade inlet shape and the blade effective outer diameter D ₂ were equal. The resulting static pressure increase value and shaft power characteristics under the same air volume and the same rotation speed conditions are shown in FIG. In this case air blowing performance, no difference in the shaft power, the substantial impeller 1 work it is clear that due to the blade effective diameter D _2. FIG. 3 shows the relationship between the blade trailing edge angle θ and the specific noise level. The specific noise level Ks is defined as noise level NL, air volume Q, and static pressure Ps. From FIG. 3, it can be seen that the noise decreases by about 5 dBA or more when the trailing edge angle θ is between about 20 and about 60 °.
[0015]
This is due to the effect of uniforming the velocity distribution of the discharged airflow and the sound source characteristics of aerodynamic noise. In the centrifugal fan, the airflow sucked in the axial direction is bent by about 90 ° and discharged in the radial direction. For this reason, the blade outlet on the main plate 1c side has a large velocity distribution. By providing the blade trailing edge angle θ, the speed distribution at the exit of the impeller 1 is made uniform, and aerodynamic noise proportional to the 6-8th power of the airflow speed can be reduced. Moreover, when the angle between the normal of the main flow and the trailing edge of the blade is 20 ° or more, the noise level is proportional to the sixth power of the wind speed due to the interference between the wake vortex layer and the trailing edge of the blade, and the dipole has high acoustic radiation efficiency. The noise level from the sound source is proportional to the eighth power of the wind speed, and the sound is reduced to a quadrupole sound source with low acoustic radiation efficiency, and the generated noise is reduced.
[0016]
The air volume of the centrifugal impeller is almost proportional to the rotational speed. On the other hand, in this experiment, noise rotation speed dependency (air volume dependency) is as follows. As shown in FIG. 4, the noise is increased from 6.5 to 7th power in the case of θ = 0 ° and θ = 50 °. It turns out that the rotation speed dependency of the change shifts, and supports the above-mentioned physical phenomenon. Further, when θ exceeds 60 °, the outer diameter of the blade on the shroud side, that is, the maximum blade diameter is significantly increased. Therefore, the increase in noise accompanying the increase in the peripheral speed becomes more dominant than the noise reduction effect by the quadrupole of the sound source. . As a result, the noise level of the impeller 1 increases. Here, as a desirable angle of the trailing edge angle θ, about 20 ° to about 40 ° is appropriate depending on the type and size of the device to which the impeller 1 is applied.
In FIG. 1 shown in the first embodiment, the main plate 1c and the shroud 1a have a linear shape, but they may not necessarily have a linear shape but may have a curved shape. In that case, the locus 2 of the inscribed circle is not necessarily a straight line as shown in FIG.
[0017]
Embodiment 2. FIG.
In the first embodiment, the shroud 1a and the casing 3 outside the shroud 1a are provided on the blade tip 1d of the blade 1b. However, as shown in FIG. 5, the blade tip 1d provided on the main plate 1c is used. Even if it is the centrifugal impeller 1 comprised with the blade | wing 1b which has, the same effect can be acquired.
[0018]
Embodiment 3 FIG.
Furthermore, as shown in FIG. 6, the same effect can be obtained even with the centrifugal impeller 1 having a configuration in which the shroud 1a is provided on the blade 1b having the blade tip 1d provided on the main plate 1c.
[0019]
Embodiment 4 FIG.
Moreover, as shown in FIG. 7, even if it is the centrifugal impeller 1 of the structure which provided the casing 3 in the outer side of the blade | wing 1b, the same effect can be acquired.
[0020]
Embodiment 5 FIG.
Furthermore, as shown in FIG. 1 or FIG. 7, the centrifugal impeller 1 is set such that the gap 5 between the casing inner diameter portion 3a and the shroud 1a or the gap 5 between the casing inner diameter portion 3a and the blade 1b is about 1 to 3 mm. The effect can be further enhanced.
The gap 5 varies depending on the type and size of the equipment to which the centrifugal impeller is applied, and is preferably as small as possible, but is determined by various factors such as equipment assembly accuracy, productivity, cost, and lifetime. Is.
[0021]
Embodiment 6 FIG.
FIG. 8 is a block diagram showing the sixth embodiment. In the figure, 4 is a circulation loss, 5 is a gap between the casing inner diameter portion 3a and the shroud 1a, Ds is an outer diameter of the shroud, and Dbs is an outer diameter of the shroud side blade, that is, a blade maximum diameter. FIG. 9 shows the experimental values of the static pressure increase value and the specific noise level Ks under the same rotational speed and the same air flow condition when the shroud outer diameter Ds is changed in the same impeller-shaped centrifugal impeller. In the figure, the horizontal axis is a value obtained by making the shroud outer diameter Ds dimensionless by the blade maximum outer diameter Dbs. From the figure, it can be seen that the ratio of Ds / Dbs is 1.1 or more, and high static pressure and low noise are obtained. In this experiment, it was confirmed that the shaft power did not change depending on the shroud outer diameter Dbs. The gap 5 between the casing inner diameter portion 3a and the shroud 1a is preferably about 1 to 3 mm as described above.
[0022]
On the other hand, in a centrifugal impeller having a wide gap 5 between the shroud-side casing inner diameter portion 3a and the shroud 1a with improved productivity, the airflow immediately after discharge is bent toward the shroud 3 due to the static pressure distribution at the impeller exit. In addition, a part of it circulates again to the impeller suction port on the low pressure side. For this reason, the increase in static pressure is significantly reduced by short-circuiting at the inlet and outlet. According to the sixth embodiment, by increasing the shroud outer diameter Ds, it is possible to reduce the circulation loss 4 that occurs when the discharge flow of the impeller circulates toward the suction side. Since the amount of work from the blade 1b received when the flow passes between the blades does not change, the performance as a fan can be improved with the same load. However, it goes without saying that this effect is further enhanced when the gap 5 is narrow.
[0023]
Embodiment 7 FIG.
In the sixth embodiment, the structure in which the casing 3 is provided outside the shroud 1a is shown. However, the present invention is not limited to the casing and may be accompanied by a peripheral structure that brings about the same effect. As shown in FIG. 10, the same effect can be obtained even with an impeller without a casing.
[0024]
Embodiment 8 FIG.
FIG. 11 is a block diagram showing the eighth embodiment. In the figure, 2 is a streamline of the discharge flow when the enlarged portion 1a 'of the shroud 1a is not present, and is a line substantially equal to the locus drawn by the center of the circle inscribed between the main plate 1 and the shroud 1a. Reference numeral 2 'denotes a streamline of the discharge flow when the shroud radial direction enlarged portion 1a' is obtained by enlarging the shroud 1a in a substantially radial direction, and θ and θe are rear edge angles of the respective blades. According to the eighth embodiment, by setting the shroud outer diameter Ds to 1.1 times or more of the shroud-side blade outer diameter Dbs, there is no leakage, and the reduction in the circulation loss 4 shown in FIG. Air volume is possible. Furthermore, the Coanda effect is provided to the discharge flow by the shroud 1a having the radially enlarged shroud radial direction enlarged portion 1a ', and the substantial discharge angle can be controlled. As a result, the substantial trailing edge angle of the blade is changed from θ to θe, and the trailing edge angle defined geometrically can be reduced in a wide range of angles from 10 ° to 60 ° with respect to the main stream.
[0025]
FIG. 12 is a block diagram showing a case where the impeller according to the present invention is applied to a rotating electrical machine. In the figure, 6 is an outer fan cover, 7 is a cooling fin, 8 is a frame, 9 is a bracket, and 10 is a shaft. When the centrifugal impeller according to the present invention is applied, a centrifugal fan used for cooling a rotary electric machine or the like can be reduced in noise and increased in air volume without increasing power. In a rotating electrical machine, a radial fan having a blade mounting angle in the radial direction is often used in order to cope with both rotational directions. In this case, the same effect can be obtained.
[0026]
FIG. 13 is a block diagram showing a case where the impeller according to the present invention is applied to an air conditioner. In the figure, 11 is a heat exchanger, 12 is a heat exchanger holder, 13 is a motor, and 14 is a streamline in the unit. When the impeller according to the present invention is applied, the impeller used in the ceiling-embedded air conditioner has the same outermost diameter (shroud outer diameter) and the actual blade size (effective blade outer diameter) The power of the impeller itself can be reduced while maintaining the blowing performance, and the noise can be reduced.
In addition, as mentioned above, although the rotary electric machine and the air conditioner were mentioned as an application example of this invention, it cannot be overemphasized that it can apply to the apparatus which requires cooling besides this.
[0027]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0028]
Eggplant and trajectory centered draw the circle, the tangent of the locus drawn by the said inscribed circle centered at the point intersects the blade trailing edge, the normal to the blade trailing edge inscribed continuous with the tip of the main plate and the blade Since the trailing edge angle is in the range of about 20 ° to about 60 °, noise can be greatly reduced with a simple and inexpensive impeller structure without impairing the air blowing performance and shaft power.
[0029]
Further, since the outer diameter of the shroud is 1.1 times or more with respect to the maximum blade diameter, a high static pressure and low noise impeller can be obtained without impairing the shaft power.
[0030]
Furthermore, since the outer periphery of the shroud extending outward from the blade maximum diameter is provided in the radial direction, an impeller capable of large air volume with reduced circulation loss at a wider range of trailing edge angles can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a characteristic diagram according to the first embodiment of the present invention.
FIG. 3 is a characteristic diagram according to the first embodiment of the present invention.
FIG. 4 is a characteristic diagram according to the first embodiment of the present invention.
FIG. 5 is a block diagram showing Embodiment 2 of the present invention.
FIG. 6 is a block diagram showing Embodiment 3 of the present invention.
FIG. 7 is a configuration diagram showing a fourth embodiment of the present invention.
FIG. 8 is a block diagram showing Embodiment 6 of the present invention.
FIG. 9 is a characteristic diagram of Embodiment 6 of the present invention.
FIG. 10 is a block diagram showing Embodiment 7 of the present invention.
FIG. 11 is a block diagram showing Embodiment 8 of the present invention.
FIG. 12 is a cross-sectional view of a rotating electrical machine that is an application example of an impeller according to the present invention.
FIG. 13 is a cross-sectional view of an air conditioner that is an application example of an impeller according to the present invention.
FIG. 14 is a sectional view of a conventional impeller.
FIG. 15 is a cross-sectional view of a conventional impeller.
[Explanation of symbols]
1 Centrifugal impeller, 1a, 101a shroud,
1a 'shroud radial expansion part, 1b, 101b blade,
1c, 101c main plate, 1d wing tip,
2 locus (streamline of discharge flow when there is no shroud expansion),
2 ′ Streamline of discharge flow when the shroud is enlarged,
3 shroud side casing, 3a casing inner diameter, 4 circulation loss flow,
5 Clearance between casing and impeller inlet, 6 Outer fan cover, 7 Cooling fin,
8 frames, 9 brackets, 10 shafts, 11 heat exchangers,
12 heat exchanger holder, 13 motor, 14 streamlines in the unit,
D ₂ blade effective outer diameter, Ds shroud outer diameter, Dbs blade maximum diameter,
θ trailing edge angle, θe trailing edge angle.

Claims (6)

A point where a trajectory drawn by the center of an inscribed circle connected to the main plate and the blade tip of the blade includes a main plate attached to the rotation shaft and a blade provided on the main plate, and the trailing edge of the blade wherein the tangent of the trajectory drawn by the inscribed circle center, the impeller of the centrifugal blower, wherein the edge angle after formed between the normal line of the blade trailing edge is in the range of about 20 ° to about 60 ° to definitive on. The impeller of the centrifugal blower according to claim 1, wherein a shroud is provided at a blade tip of the blade. The impeller of the centrifugal blower according to claim 1, wherein a casing is provided outside the blade. The impeller of the centrifugal blower according to claim 2, wherein a casing is provided outside the shroud. The impeller of the centrifugal fan according to claim 2 or 4, wherein the outer diameter of the shroud is 1.1 times or more with respect to the maximum blade diameter. 6. The impeller of a centrifugal blower according to claim 5, wherein an outer peripheral portion of the shroud extending outward from the blade maximum diameter is provided in a radial direction.

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