JP2000265997A - Vane type propeller fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the noise, the weight, and materials without impairing aerodynamic characteristics of a vane type propeller fan by providing slits at least in a partial zone of a vane pressure surface in the vane type propeller fan. SOLUTION: This vane type propeller fan 10A is molded of plastic, etc., has a plurality of vanes 11, and has a rotary drive source such as a motor connected to a boss 13. In this case, a lot of slits 12 are formed in a vane face of small curvature side in its cross sectional shape, namely a vane pressure face (venter face) 11a in each vane 11. For example, 11, narrow, long, recessed groove slits 12 are provided along the vane face flow direction in a partial zone of the vane pressure face 11a, however, the slits 12 are preferably to be concentric relative to the rotary shaft 15 in designing. The angle formed between the slits 12 and the flow direction is formed within 20 deg. and the widths of the respective slits 12 are preferably set to 7 mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airfoil propeller fan for use in an outdoor unit of an air conditioner, a ventilation fan, and the like, and more particularly to a fan capable of reducing weight without impairing aerodynamic performance. Related to wing shape.

[0002]

2. Description of the Related Art Conventionally, a blower that rotates a propeller fan at a relatively low speed to blow air has been used as a heat exchanger blower fan, a ventilation fan, or the like in an outdoor unit of an air conditioner. As the propeller fan, a fan manufactured by molding a plastic material is widely used. The shape of the blade used in such a propeller fan is generally made of a thin plate in order to cope with mass production at low cost.

FIG. 7 shows an outdoor unit of an air conditioner, where (a) is a plan view and (b) is a front view. The outdoor unit shown in FIG. 7 is an outdoor unit of a residential air conditioner. The outdoor unit functions as a radiator during the cooling operation, and functions as a heat absorber during the heating operation. In either operation, basically, heat is exchanged between the air and the refrigerant system. In this outdoor unit, a blower fan 1, a heat exchanger 2, and a compressor 3 are mounted as main components, and the blower fan 1 and the heat exchanger 2 form a heat exchange system. It functions as a refrigerant circulation pump. Further, a partition plate 4 forming a compressor chamber is provided for sound insulation of the compressor 3 and formation of a flow path.

[0004] The main sound sources of this outdoor unit are the operating sound of the compressor 3 and the operating sound of the blower fan 1, and the sound of the blower fan 1 (hereinafter referred to as fan sound) is generally the loudest. This is because the operation sound of the compressor 3, which is a mechanical sound, is not preferable in terms of feeling when compared with the fan sound, so that the masking is performed by the fan sound.

[0005] In recent years, energy saving of air conditioners has been called for, and high COP (Coefficient of Performance) of refrigerant systems has been studied. To achieve this, high-efficiency heat exchangers and compressors are being developed. In cooling operation, the compressor input that contributes the most is reduced by lowering the high pressure. In order to improve the operating point of the compressor, it is necessary to improve the performance of the outdoor heat exchanger 2. At this time, since the difference between the refrigerant temperature and the suction air temperature becomes small, a large amount of air needs to be passed through the outdoor heat exchanger 2. Furthermore, the pressure loss (hereinafter, pressure loss) of the air-side fins having a contribution rate of half or more of the performance of the outdoor heat exchanger 2 tends to increase for higher performance.

The ventilation fan 1 is responsible for ventilation of the outdoor heat exchanger 2, and its fan power is (air volume) × (system pressure loss) and its noise is log (air volume × (system pressure loss)).
² ), the high-pressure loss of the heat exchanger 2 occupying more than half of the air volume and the air pressure loss of the outdoor unit makes the blower fan 1 very difficult not only in power but also in noise. For this reason, the blowing fan 1 is required to have high static pressure, high efficiency, and low noise. As one of the powerful methods for increasing the static pressure, increasing the efficiency, and reducing the noise of the blower fan 1, there is a propeller fan that employs a thicker blade section with a thicker blade. A propeller fan employing such a thick wing cross-sectional shape will be referred to as a thick propeller fan.

FIGS. 8 (a) and 8 (b) show the cross-sectional shape of a blade used in a conventional propeller fan, where (a) is a front view of the propeller fan, and (b) is (a). D
It is sectional drawing which follows the -D line. In the figure, reference numeral 10 denotes a propeller fan, which is constituted by three blades 11. The cross-sectional shape of the wing 11 is constituted by curved surfaces each having a different radius of curvature such that the radius of curvature of the upper (front) surface 11b is smaller than the radius of curvature of the antinode (rear) surface 11a. The abdominal surface 11a is called a wing pressure surface. In such a blade shape, when the airfoil propeller fan 10 is rotated in the rotation direction of the arrow 4, the air is blown in the airflow direction of the white arrow 5 intersecting with the rotation surface of the airfoil propeller fan 10. become.

[0008]

By the way, it has been found that the propeller fan having the above-mentioned thick-walled blade cross section has an advantage in terms of aerodynamic characteristics as compared with a propeller fan having a thin-walled blade. Here, comparing the aerodynamic performance and the noise performance of the thick-walled propeller fan shown by the one-dot chain line in FIG. 9 and the thin-walled propeller fan shown by the solid line, as shown in FIG. It can be seen that both aerodynamic performance (static pressure efficiency and static pressure coefficient) and noise performance (specific noise) are excellent. In FIG. 10, a curve that rises to the right and is indicated by a two-dot chain line is a load curve with respect to the air blowing characteristics, and changes as operating conditions or units change. The intersection of the load curve and the fan characteristic (static pressure coefficient) determined by the propeller fan is the operating point P, and the direction of the streamline (shape of the streamline) is uniquely determined by determining the operating point P. The "flow direction" means the streamline direction of the fluid flow along the blade surface of the propeller fan. Since these are dimensionless quantities, they do not change even if the rotational speed of the propeller fan changes, for example. However, for the operating point P, the outdoor heat exchanger 2
Changes when load characteristics change or the device changes due to frost. That is, for the same device, if the load changes as shown with respect to the load at the design point p,
It can be seen that the flow direction changes with respect to the flow direction at the design point p. Also, when the load changes due to a change in the device corresponding to the load at the design point p, this means that a change in the flow direction can be expected based on this concept.

In the blade cross-sectional shapes shown in FIGS. 9 and 10, the thickness of the thick propeller fan is about three times as large as that of the thin propeller fan. If the thickness of the wings is so thick,
The conventional general low-cost plastic molding method cannot be molded due to the problem of sink marks, and it is necessary to employ a special molding method. Therefore, the molding cost of the airfoil propeller fan becomes high. As a matter of course, the weight increases due to the increase in the thickness, which also causes vibration. In addition, material costs will increase.

As described above, the first problem of the conventional airfoil propeller fan is that, when the airfoil is formed of plastic, the airfoil is formed into a thick wall. In the low cost molding method described above, it is pointed out that there is a limit to the wall thickness that can be molded. Also, the second
The problem is that the thick wing shape increases the weight of the entire wing by the increased thickness, increases the cost due to the use of many plastic materials, and the third problem is that it causes vibration. It is.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce noise without impairing the aerodynamic characteristics of an airfoil propeller fan and to reduce its weight and material. is there.

[0012]

The present invention employs the following means to solve the above-mentioned problems. The airfoil propeller fan according to claim 1 is characterized in that a slit is provided in at least a part of a blade pressure surface of the airfoil propeller fan. In this case, the slit may be provided on the entire surface of the blade pressure surface.

With such an airfoil propeller fan,
The aerodynamic performance of the airfoil propeller fan can be maintained to reduce noise, and the amount of molding material can be reduced by the amount provided with the slits, so that the weight of the fan can be reduced.

In the above-mentioned bladed propeller fan, it is preferable that the slit is provided concentrically with respect to the rotation axis or in the blade surface flow direction. Preferably, the angle between the slit and the flow direction is set to 20 degrees or less. Good. The width of the slit is preferably 7 mm or less, and the end of the partition provided between the slits is preferably formed in an R shape. With such a shape and arrangement of the slits, the operating noise of the airfoil propeller fan can be reliably suppressed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an airfoil propeller fan according to the present invention will be described below with reference to the drawings. FIG.
1 is a front view showing a first embodiment of an airfoil propeller fan used for a blower operated at a relatively low speed, and reference numeral 1 is used.
0A is an airfoil propeller fan, 11 is a wing, 12 is a slit, and 13 is a boss. This airfoil propeller fan 10A
Is formed by molding a material such as plastic. In the example shown in the figure, a plurality of blades 11 are provided, and a boss 13 is connected to a rotation drive source such as an electric motor (not shown).

As shown in each sectional view of FIG. 2, each blade 11 is provided with a large number of slits 12 on the blade surface on the side having a smaller curvature in the sectional shape, that is, on the blade pressure surface (belt surface) 11a. In the illustrated example, a slit 12 having a long and narrow groove is formed in a partial area of the blade pressure surface 11a along the blade surface flow direction.
Although one slit is provided, in many cases, these slits 12 are concentric with the rotating shaft 15 at the design point. Even if the load changes and the flow direction changes, the noise characteristics do not change if θ 特性 30 degrees as shown in FIG. Further, the groove may be provided at an angle to the circumferential direction so that the change range of the flow direction falls within 30 degrees.

Further, in the thick propeller fan 10B of the second embodiment shown in FIG.
Many are provided on the entire surface of a. In the illustrated example, twelve slits 12 are provided along the blade surface flow direction, and these slits 12 are also often concentric with the rotating shaft 15 at the design point (the angle θ = 0 °). )
Becomes

As described above, in the airfoil propeller fan of the present invention, a large number of the elongated slits 12 are formed on the abdominal surface which is the pressure surface.
The area where the slit processing is performed is the entire area or a part of the blade pressure surface 11a. In FIG. 2, (a) is an airfoil cross-sectional shape cut along a cross section including the center line of the slit 12 (AA cross section in FIG. 1), and (b) is an airfoil cross-sectional shape of a portion where the slit 12 is not provided. (Cross section BB in FIG. 1) and (c) show an airfoil cross section shape in a section perpendicular to these sections (C section in FIG. 1). In these figures, the shape of the slit 12 is such that each part of the airfoil propeller fan has a thickness defined by a conventional thin-wall molding method, in other words, each part is formed by a conventional low-cost molding method. The thickness is determined so as to be within the range of the moldable thickness without sink marks.

The area in which the slit 12 is formed is a region where the conventional thin-wall molding method cannot be used with a thick airfoil, that is, a region which is thicker than a certain value. For this reason, in the shape of the airfoil propeller fans 10A and 10B, when the entire airfoil 11 is a thick airfoil such as an airfoil, a slit 12 is provided on the entire surface as shown in FIG. However, when only the boss 13 with a large wing load has thick wings, the slit 12 may be provided only near the boss 13 as shown in FIG.

FIG. 4 shows experimental results comparing the aerodynamic performance and the noise performance of the airfoil propeller fan according to the present invention provided with the slits 12 and the airfoil propeller fan without the slits 12. In FIG. 4, the solid line indicates an airfoil propeller fan without a slit, and the circle indicates an airfoil propeller fan with a slit, and there is almost no difference between the static pressure efficiency, the static pressure coefficient and the specific noise. I understand. That is, even if the slit 12 is provided on the blade pressure surface 11a of the thick propeller fan, there is no difference in aerodynamic performance and noise performance. Therefore, the wing pressure surface (wing surface) 1
If the shape of the slit 12 to be processed into 1a is determined so as to keep the maximum thickness that can be formed by the conventional low-cost molding method, and the molding die is manufactured, it can be easily formed by the low-cost conventional method. In addition, the airfoil propeller fan 10
A and 10B can be reduced in weight, and the cost of the material required for molding can be reduced to lower the cost.
In addition, the cause of vibration is reduced by weight reduction.

Subsequently, the graph of the experimental result shown in FIG.
It shows the relationship between the width of the slit 12 (slit width W) and noise. According to the experimental results, it is understood that when the slit width W exceeds 7 mm, the noise increase amount sharply increases and the noise performance deteriorates. Therefore, the slit 12
The width W of about 7 mm or less is considered appropriate from the viewpoint of noise reduction. This is because, when the slit width W is small, even if the slit 12 is provided, in an airfoil propeller fan operated at a relatively low speed, such as an outdoor unit in an air conditioner, the flow is reduced due to its own stagnation pressure. 12, the air flow is not formed in the slit 12, and as if an air wing was formed in the slit 12, the noise performance was almost the same as a solid airfoil. It is thought that it is.

The surface of the partition between the adjacent slits 12 has a basic airfoil shape. By providing the slit 12, the slit 12 is provided as described above.
Almost no air flow enters the inside, but the wing pressure surface 1
In the vicinity of the surface 1a, it is considered that the air flow enters the slit 12 or flows along the surface of the blade pressure surface 11a. For this reason, the end surface 14 of the partition 14
If there is an edge portion at a (see FIG. 2 (c)), when the operating point of the propeller fan changes, the flow has an angle of attack, and there is a possibility that airflow noise may be emitted from the end face 14a. For this reason, the tip of the partition part 14 (blade pressure surface 11a)
As shown in FIG. 2 (c), it is better to make the end face 14a round and round. Further, the thickness Ws of the partition portion 14 between the slits 12 is about 2 to 4 mm, which is the thickness of ordinary plastic molding, and does not cause any problem.

In the case where the center line L of the slit 12 and the flow direction indicated by the arrow R have an angle θ,
FIG. 6 shows an experimental result of the effect of the angle θ on noise. According to the experimental results, it is understood that the noise increase amount is substantially not substantially present and substantially constant in a region where the angle θ between the slit 12 and the flow is up to about 20 degrees. However, in a region where the angle θ exceeds 30 degrees, the noise increase amount tends to increase rapidly as the angle θ increases. Therefore, in order to maintain noise performance, the angle θ should be set to 30 degrees or less. preferable. Therefore, the thick propeller fan 10A,
When the slit 12 is added to 10B, if it is a design point, if it is provided concentrically with respect to the rotating shaft 15, -30 degrees ≦
This is effective for a load change in a flow change range of θ ≦ 30 degrees. Conversely, the angle of the groove may be provided so as to be inclined with respect to the circumferential direction so as to fall within this change range.

The wing profile of the wing type propeller fan of the present invention has been described above with reference to the drawings. However, the specific configuration is not limited to the present embodiment, and does not depart from the gist of the present invention. The design can be changed as needed. For example, the number of blades of the airfoil propeller fan may be three or four or more, and the number of slits 12 may be appropriately changed according to the shape and dimensions of the blades 11.

[0025]

According to the blower of the present invention described above, the weight can be reduced without impairing the aerodynamic performance and the noise performance by forming the slit on the blade pressure surface of the thick propeller fan. In addition, since the thick portion is eliminated by providing the slit and the problem of sink at the time of molding is eliminated, it is possible to adopt a low-cost thin-wall molding method that is conventionally used.
The material required for molding can also be reduced. For this reason, it is effective not only in improving performance and reducing running costs due to weight reduction of the airfoil propeller fan, but also in reducing manufacturing costs.

Furthermore, the cause of vibration is reduced by the weight reduction. This is because the exciting force f that causes vibration is f = (W
is clear from the fact described by e / g) rω ^2. Here, We: weight of the rotating body, g: gravitational acceleration, r: eccentricity, and ω: rotational angular velocity.

In particular, the slit width W should be 7 mm or less, and the slit should be concentric with the axis of rotation or along the flow direction of the blade surface, preferably the angle θ between the slit and the flow direction.
Is set at 20 degrees or less, and the end of the partition is
By adopting the shape, almost the same noise performance as a solid airfoil propeller fan without a slit can be obtained, and an increase in operating noise due to the slit can be prevented.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of an airfoil propeller fan according to the present invention, and is a front view of a blade shape in which a slit is provided in a partial region of a blade pressure surface.

FIGS. 2A and 2B are cross-sectional views showing the airfoil shape of FIG. 1, wherein FIG. 2A is a cross-sectional view taken along line AA of FIG. 1, FIG. 2B is a cross-sectional view taken along line BB of FIG. 2) is a sectional view taken along line CC of FIG.

FIG. 3 is a front view of a blade-shaped propeller fan according to a second embodiment of the present invention, in which a slit is provided in an entire region of a blade pressure surface.

FIG. 4 is a diagram showing aerodynamic characteristics and noise characteristics of a thick-walled bladed propeller fan provided with a slit and a solid-walled bladed propeller fan without a slit.

FIG. 5 is a graph of an experimental result showing a relationship between a slit width W of the airfoil propeller fan according to the present invention and a noise increase amount.

FIG. 6 is a graph of an experimental result showing a relationship between an angle θ between a slit and a flow of the airfoil propeller fan in the present invention and an amount of noise increase.

FIG. 7 is a schematic configuration diagram showing an outdoor unit of a residential air conditioner, where (a) is a plan view and (b) is a front view.

8A and 8B are diagrams showing a conventional (solid) airfoil propeller fan, wherein FIG. 8A is a front view, and FIG. 8B is a cross-sectional view taken along line DD of FIG.

FIG. 9 is a cross-sectional view showing thin and thick propeller fan airfoil cross-sectional shapes in an overlapping manner.

10 is a diagram showing aerodynamic characteristics and noise characteristics of the thin propeller fan and the thick propeller fan having the airfoil cross-sectional shape shown in FIG.

[Explanation of symbols]

10A, 10B Airfoil propeller fan 11 Blade 11a Blade pressure surface 12 Slit 13 Boss 14 Partition 15 Rotation axis W Slit width θ Angle between slit and flow (direction)

Continuation of front page (72) Inventor Kei Matsuda 3-1-1 Asahicho, Nishibiwajima-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Mitsubishi Heavy Industries, Ltd. Air Conditioning Works

Claims (6)

[Claims] An airfoil propeller fan characterized in that a slit is provided in at least a part of a blade pressure surface. 2. The airfoil propeller fan according to claim 1, wherein the slit is provided on the entire surface of the blade pressure surface. 3. The slit according to claim 1, wherein the slit is provided concentrically with respect to a rotation axis or in a blade surface flow direction.
Or the airfoil propeller fan according to 2. 4. An airfoil propeller fan according to claim 3, wherein the angle between the slit and the flow direction is set to 20 degrees or less. 5. The airfoil propeller fan according to claim 1, wherein the width of the slit is set to 7 mm or less. 6. An end portion of a partition provided between the slits is formed in an R-shape.
The propeller fan according to any one of the above.