JPH08159090A - Axial fan - Google Patents

Abstract

(57) [Summary] [Purpose] A low-noise axial fan is realized by suppressing the generation of turbulence between fan blades and reducing the rotational noise. An axial fan used by mounting a shaft fixing portion 12 provided on an axial center of a fan boss 1 on a rotary shaft 41 of a fan motor 4, and having a plurality of different diameters around the fan boss 1. A plurality of fans for concentrically arranging the thin plate cylinders and for feeding air to the leeward side during rotation between the fan boss 1 and the cylinders 2 having the smallest diameter, and between each adjacent cylinders 2. Due to the presence of each of the cylinders 2, the ventilation cross section is narrowed by the presence of each of the cylinders 2, the separation of the air flow at the negative pressure surface of the fan blades is suppressed, and the development of the boundary layer is restricted. The one that makes the distribution uniform and suppresses the generation of turbulence that causes noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel axial fan used as a blower or the like installed in an outdoor unit of an air conditioner.

[0002]

2. Description of the Related Art Conventionally, a blower of this type is shown in FIG.
A propeller fan type axial fan as shown in Fig. 2 is generally widely used. As is well known, the axial fan F includes a cylindrical fan boss 5 having a shaft fixing portion 51 mounted on a rotary shaft of a driving means such as a motor and having an axial center, and the outer periphery of the fan boss 5 is provided. The required number of fan blades 6 are radially mounted in the radial direction.

By the way, in recent years, with the widespread use of air conditioners, noise damage particularly from the outdoor unit has become a problem.
The fan noise used for ventilation of the heat exchanger is as dominant as the compressor noise. Therefore, in order to reduce the noise of the outdoor unit, it is essential to take measures to reduce the fan noise.

The noise emitted from this axial fan is divided into broad band noise and discrete frequency noise. It is known that the former wide band noise is dominant in a low pressure fan used in an air conditioner. There is. Broadband noise is induced by upstream turbulence, boundary layers on the blade surface, pressure fluctuations on the blade surface due to flow after separation of the boundary layer, or by vortices emitted from the blade trailing edge. Above all,
It is considered that the noise generation due to the flow separated on the entire surface of the blade is a dominant factor in the low flow rate region, and that the vortex discharge from the trailing edge of the blade is the most important factor.

From the above point of view, various researches have been conventionally conducted on the shapes of the fan blades 6 and the fan bosses 5, and the noise reduction measures are taken together with the improvement of the blowing performance.

[0006]

FIG. 11 schematically shows the measurement result of the turbulent energy in the surface air flow of the fan blade 6 in the axial flow fan F having the above-mentioned conventional structure. As shown in this figure, in the case of the conventional axial fan,
The air flow direction in the vicinity of the fan boss 5 is considerably in the radial direction, and the turbulent energy is large. Therefore, on the negative pressure surface of the fan blade 6, a vortex is generated due to separation of the air flow, and turbulent noise is increased. In addition, there is a problem that the noise level due to the fan is increased due to the generation of a rotating sound, which is one of the noises, due to the pressure fluctuation caused by the rotational driving of the fan F, and the blowing characteristic is deteriorated.

The present invention is intended to solve the above-mentioned conventional problems, and suppresses the generation of turbulence between fan blades and reduces the rotation noise, thereby reducing the noise level of the fan. It is an object of the present invention to provide an axial fan capable of reducing the air flow and improving the air blowing characteristics.

[0008]

In order to achieve the above object, an axial fan according to the present invention has a plurality of cylindrical bodies having different diameters arranged concentrically with the fan boss around the fan boss, and Formed in a space between the fan boss and the cylinder having the smallest diameter, and in a space between the adjacent cylinders so that the fan boss and the cylinders are driven to rotate integrally with each other, and air can be pumped to the leeward side during the rotation. With multiple fan blades,
The fan boss, the cylindrical body, and the adjacent cylindrical bodies are integrally connected and fixed via these fan blades.

The axial fan having the above construction is used by mounting the shaft fixing portion provided on the axial center of the cylindrical portion of the fan boss on the rotary shaft of the driving means, and each cylindrical body suppresses the occurrence of turbulent flow. It is provided for this purpose and is made of a thin plate. The distance between the fan boss and the cylinder with the smallest diameter and the distance between adjacent cylinders are limited to the Reynolds number so that the air flow through the gap where the fan blades are arranged becomes laminar when the fan rotates. Is set to be done.

The shape of each of the cylinders and the fan boss cylinder is equal to each other in the axial direction, or is a shape that gradually expands from the suction side to the discharge side in order to reduce the flow around each peripheral surface. To form. Further, the mounting position and the number of fan blades are set for each of the gaps in order to reduce the rotation noise. Furthermore, the positional relationship between the front and rear edges of each of the cylinders is set so as to be located axially forward or rearward of the front and rear edges of the fan blade.

[0011]

According to the axial fan having the above-mentioned structure, since the ventilation passage is restricted by the presence of each cylinder, the flow velocity distribution between the fan blades when the fan is rotated by being driven by the driving means. Will be uniform. In addition, by narrowing the air gap between the fan boss and the cylinder and between adjacent cylinders, that is, the ventilation cross section, it is possible to suppress air flow separation on the fan blade negative pressure surface and to limit the development of the boundary layer. Therefore, it is possible to reduce turbulent noise.

In the case where each of the cylinders has a shape which is gradually expanded from the center side to the outer circumference side, it is possible to suppress the generation of turbulent noise around each cylinder and to blow air by the centrifugal force generated by the rotation of each cylinder. It is possible to obtain the effect. Further, by appropriately selecting the mounting position and the number of fan blades installed between the cylindrical bodies, it is possible to reduce the rotation noise, so-called Nz noise. Furthermore, by setting the front and rear edge positions of each of the cylinders and the fan blade as described above, it becomes possible to suppress the inflow airflow to the fan blade front edge and the backflow behind the fan blade by the cylinder body. It is possible to reduce noise.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an axial flow fan according to a first embodiment of the present invention, FIG. 1 is a front view thereof, FIG. 2 is a cross section taken along a cutting line AA in FIG. 1, and FIG. FIG. 4 shows the appearance of the portion B, and various modes of the positional relationship between the fan blade and the cylindrical body. 1 to 3,
The axial flow fan F1 of this embodiment includes a fan boss 1, a plurality of cylindrical bodies 2 having different diameters, and a plurality of fan blades 3.

The fan boss 1 is provided with a cylindrical portion 11 formed to have an equal diameter in the axial direction, and the axial center of the cylindrical portion 11 is
A support plate for arranging a short tubular shaft fixing part 12 having a hole-shaped cross section, and connecting the front end of the shaft fixing part 12 and the inner peripheral surface of the cylindrical part 11 to connect the two 11, 12 together. The part 13 is integrally formed. Each cylinder 2 is
For example, a plastic thin plate is formed in a cylindrical shape having an equal diameter in the axial direction, and is arranged around the fan boss cylindrical portion 11 concentrically with the fan boss 1.

Each fan blade 3 has a space g between the fan boss 1 and the cylindrical body 2 having the smallest diameter, and between each adjacent cylindrical body 2.
Attached to the fan boss 1 and the cylindrical body 2 and adjacent cylindrical bodies 2 via the fan blades 3.
They are connected and fixed together. Further, each fan blade 3 is rotationally driven integrally with the fan boss 1 and each cylindrical body 2, and is formed in a blade shape capable of pumping air to the leeward side when rotating.

The axial-flow fan F of this embodiment having the above structure
1, the shaft hole of the shaft fixing portion 12 is mounted on the rotating shaft 41 of the fan motor 4 as a driving means.
Is driven to rotate.

In the present embodiment, six fan blades 3 are mounted between each cylindrical body 2, but in the present invention, the number and shape of the fan blades 3 are not particularly limited. It may be formed with an optimum number of sheets corresponding to the peripheral speed and the air volume, a curved surface shape, and an attachment angle.

By the way, the distance between the fan boss cylindrical portion 11 and the cylindrical body 2 having the minimum diameter, and the distance between adjacent cylindrical bodies 2 are determined by the air flow passing through the gap g in which the fan blades 3 are arranged when the fan is rotated. It is set to be limited to the Reynolds number such that is a laminar flow. That is, in order to limit the Reynolds number such that the air flow between the fan blades 3 becomes a laminar flow, the distance between the fan boss cylindrical portion 11 and the cylindrical body 2 having the smallest diameter, and the distance between each adjacent cylindrical body 2 are set. The value represented by the following formula 1 was used.

Re = ωδ / ν <2320 ... Formula 1 where Re: Reynolds number ω: Relative velocity between fluid and fan blade δ: Distance between cylinders ν: Coefficient of kinematic viscosity of fluid

With this structure, the airflow between the fan blades 3 can flow in the circumferential direction. In addition, since the ventilation path is limited due to the presence of the cylindrical body 2 on the ventilation path, the generation of turbulence is suppressed, and the improvement of the ventilation performance and the reduction of noise can be realized as compared with the conventional case. it can.

FIG. 9 shows the measurement result of the velocity vector of the blade surface flow of the conventional axial flow fan F. As shown in this figure, in the case of an ordinary propeller fan, the fan blade 6
The flow velocity of is fast in the outer circumference.

In the present embodiment, if the distance between the cylinders 2 is set to the maximum value that satisfies the above formula 1 in order to reduce the pressure loss between the fan blades 3, the flow velocity between the fan blades 3 will be the conventional value shown in FIG. As in the example, because it is fast around the fan,
The distance between the cylinders 2 gradually decreases from the center side of the fan to the outer peripheral side. However, in the present invention, the distance between the cylinders 2 is not particularly limited to the maximum value that satisfies the above formula 1, and the distance between the cylinders 2 can be arbitrarily set within the range of the above formula 1. .

For example, in the case of an axial fan having a fan outer diameter of φ250 mm and a fan boss diameter of φ100 mm, if the number of revolutions is 500 rpm, the air volume is 15.0 m ³ , the flow velocity distribution in the axial direction is uniform, and the fluid is air at 20 ° C. , The relative velocity between the fluid and the fan blade 3 can be derived by the following equation (2).

[0024] _{U l = V / {60 ×} π × (r t 2 -r b 2)} U t = n × 2 × π × r t / 60 U b = n × 2 × π × r b / 60 ω ^{_{t = (U l 2 + U}} t 2) 1/2 ω b = (U l 2 + U b 2) 1/2 or more, equation 2 where, U _l: fluid axial direction velocity V: flow rate n: rotational speed r _t : fan periphery radius r _b: fan boss radius U _t: circumferential speed of the fan outer peripheral U _b: peripheral speed of the fan boss omega _t: fan periphery relative velocity omega _b: fan boss relative velocity

By deriving the distance between the cylinders 2 from the relative velocity derived from the above equation 2 and the above equation 1, the result of the following equation 3 is obtained.

Δ _t <2320 × ν / ω _t δ _b <2320 × ν / ω _b or more, Formula 3 where δ _t : Distance between cylinders of fan outer peripheral portion δ _b : Distance between cylinders of fan boss portion

Calculating by substituting specific numerical values in the above formula 3, δ _t <3.93 (mm) δ _b <5.32 (mm), and the maximum value of the distance between the cylinders 2 is the center side of the fan. To the outer circumference side. According to this calculation, the number of the cylinder bodies 2 is 17 or more, but in the present embodiment and the second to fourth embodiments described later, the drawings are simplified to avoid complexity, and the cylinder body 2 is set to six bodies. There is.

FIG. 4 is a development view of a cross section in the circumferential direction showing various aspects of the positional relationship between the cylindrical body 2 and the fan blade 3 in the cross section in the circumferential direction of the axial fan of this embodiment. FIG.
In (a) to (d), the arrow x indicates the blowing direction, and the arrow y indicates the rotating direction of the fan. In the embodiment shown in FIG. 4A, the suction side edge 2a of the cylindrical body 2 coincides with the suction side edge 3a of the fan blade 3, and the blowout side edge 2b coincides with the blowout side edge 3b of the fan blade 3 in the axial direction. It is composed.

In the embodiment shown in FIG. 4 (b), a space t (1) is provided between the suction side edge 2a of the cylindrical body 2 and the suction side edge 3a of the fan blade 3 in the axial direction, and the blowing side edge 2b of the cylindrical body 2 is provided. Coincides with the outlet side edge 3b of the fan blade 3. On the contrary, in the mode shown in FIG. 4 (c), the suction side edge 2a of the cylindrical body 2 in the axial direction is the fan blade 3
Corresponding to the suction side edge 3a of the fan blade 3 and the blow side edge 3b of the fan blade 3 at a distance t.
(2) is set.

Further, the embodiment shown in FIG. 4 (d) has a cylindrical body 2
The suction side edge 2a of the fan blade 3 and the suction side edge 3a of the fan blade 3 with a space t (1), and the outlet side edge 2b of the cylindrical body 2.
And the interval t (2) between the outlet side edge 3b of the fan blade 3 is set. Thus, the cylindrical body 2 and the fan blade 3
By arbitrarily setting the edge distance between the suction side and the blow side of the fan blades, the airflow flowing into the fan blades 3 and the wake of the fan blades 3 can be suppressed, and the blowing performance can be improved and the noise can be reduced. .

5 and 6 show an axial flow fan according to a second embodiment of the present invention, FIG. 5 shows its front face, and FIG. 6 shows a cross section taken along the line C--C in FIG. . The axial fan F2 of this embodiment is similar to that of the first embodiment,
A plurality of thin-plate cylindrical bodies 2 having different diameters are arranged around the cylindrical portion 11 of the fan boss 1 concentrically with the fan boss 1, and between the fan boss cylindrical portion 11 and the cylindrical body 2 having the smallest diameter, and adjacent to each other. A plurality of fan blades 3 are arranged in the gaps g between the corresponding cylindrical bodies 2, and the fan boss 1 and the cylindrical body 2 and adjacent cylindrical bodies 2 are integrally connected and fixed via these fan blades 3. It is configured. And each cylindrical body 2
Also, the cylindrical portion 11 of the fan boss 1 is formed in a cone shape that gradually expands from the suction side to the blowout side.

In the present embodiment, as described above, the cylindrical body 2 and the cylindrical portion 11 of the fan boss 1 are formed in such a shape that they gradually expand from the suction side to the blowout side. While reducing turbulence generation,
The centrifugal force generated in the cylindrical body 2 when the fan rotates causes a blowing effect, so that the blowing performance of the axial fan can be improved.

FIG. 7 shows an axial flow fan according to the third embodiment of the present invention. In the axial fan F3 of this embodiment, as in the first and second embodiments, a plurality of thin plate cylindrical bodies 2 having different diameters are provided around the cylindrical portion 11 of the fan boss 1 in the fan boss 1. The fan blades 3 are arranged concentrically with each other, and a plurality of fan blades 3 are arranged between the fan boss cylindrical portion 11 and the cylindrical body 2 having the smallest diameter and in the gap g between the adjacent cylindrical bodies 2. Through fan boss 1 and cylindrical body 2
And adjacent cylindrical bodies 2 are integrally connected and fixed. Further, the mounting position of the fan blade 3 is configured to be displaced in the circumferential direction for each cylindrical body 2.

In the present embodiment, since the mounting position of the fan blade 3 is shifted in the circumferential direction for each cylindrical body 2 as described above, a phase difference in the pressure fluctuation at the edge of the fan blade 3 occurs. The rotating sound can be effectively reduced.

FIG. 8 shows an axial fan according to the fourth embodiment of the present invention. The axial flow fan F4 of the present embodiment has a plurality of thin plate cylindrical bodies 2 having different diameters around the cylindrical portion 11 of the fan boss 1 as in the first to third embodiments. Are arranged concentrically with each other, and between the fan boss cylindrical portion 11 and the cylindrical body 2 having the smallest diameter, and adjacent cylindrical bodies 2
A plurality of fan blades 3 are arranged in the space g between them, and the fan boss 1 and the cylindrical body 2 and adjacent cylindrical bodies 2 are integrally connected and fixed via the fan blades 3. Then, the fan blade 3 between each cylindrical body 2
The number of sheets is changed for each cylindrical body 2.

In this embodiment, the number of the fan blades 3 is reduced by 8 on the outer circumference of the fan boss 1 and by 1 for each cylindrical body 2 toward the outer circumference. The number of sheets is not particularly limited, and it is formed so as to be an optimum number depending on the fan size and the air blowing performance of the fan.

In this embodiment, since the number of fan blades 3 between the cylinders 2 is changed for each cylinder 2 as described above, a phase difference of pressure fluctuation is generated at the edge of each fan blade 3. The rotating noise can be effectively reduced.

As shown in FIG. 4, each cylindrical body 2
The configuration of setting the positional relationship between the front and rear edges of the fan blade 3 so as to be located in front of or behind the front and rear edges of the fan blade 3 is not limited to the axial fan F1 of the first embodiment.
In the axial flow fans F2 to F4 in the fourth embodiment, the airflow flowing into the fan blades 3 and the wake of the fan blades 3 are similarly suppressed, and the effects of improving the blowing performance and reducing noise are achieved.

[0039]

As described above, according to the present invention, the ventilation cross section is narrowed due to the relatively simple structure in which a plurality of cylindrical bodies are concentrically arranged around the fan boss at intervals. , It is possible to suppress the separation of the air flow on the fan blade negative pressure surface, and to restrict the development of the boundary layer, so that the flow velocity distribution between the fan blades is made uniform,
It is possible to effectively suppress the generation of turbulence that causes noise, and thereby improve the blowing performance and effectively reduce the noise level.

Further, if the diameter of each cylinder is gradually increased from the suction side to the discharge side, turbulent flow around the cylinder can be suppressed, and at the same time, the centrifugal force generated by the rotation of the cylinder can provide a blowing effect. Therefore, it is possible to easily improve the blowing performance and reduce the noise level. Furthermore, if the mounting position of the fan blades is shifted in the circumferential direction, or if the number of fan blades is changed for each cylinder, a phase difference occurs in the pressure pulsation and it is possible to reduce the rotation noise. Becomes

Furthermore, if the suction side edge of the cylindrical body is provided in front of the fan blade suction side edge, the inflow air flow into the fan blade can be suppressed, and the blowout side edge of the cylindrical body can be made more than the fan blade blowout side edge. If it is provided at the rear side, the wake of the fan blade can be suppressed, and noise can be reduced in any case.

[Brief description of drawings]

FIG. 1 is a front view showing an axial flow fan according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the section line AA in FIG.

FIG. 3 is a perspective view of an essential part showing an enlarged part B in FIG.

FIG. 4 is a partial circumferential development view showing various aspects of the positional relationship between a fan blade and a cylindrical body.

FIG. 5 is a front view showing an axial fan according to a second embodiment of the present invention.

6 is a cross-sectional view taken along the section line CC in FIG.

FIG. 7 is a front view showing an axial fan according to a third embodiment of the present invention.

FIG. 8 is a front view showing an axial fan according to a fourth embodiment of the present invention.

FIG. 9 is a front view of relevant parts showing an airflow velocity vector on a fan blade of an axial flow fan of a conventional example.

FIG. 10 is a perspective view showing a conventional axial flow fan.

FIG. 11 is a front view of a main portion showing the turbulent energy distribution.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fan boss 11 Cylindrical part 12 Shaft fixing part 2 Cylindrical body 2a Suction side edge 2b Blowing side edge 3 Fan blade 3a Suction side edge 3b Blowing side edge 4 Fan motor 41 Rotating shaft

Claims (3)

[Claims] 1. A fan boss having a shaft fixing portion mounted on a rotary shaft of a drive means at its axis, and a plurality of cylindrical bodies having different diameters are arranged concentrically with the fan boss around the fan boss. Further, the fan boss and the cylinders are driven to rotate integrally with the fan boss and the cylinders in the space between the fan boss and the cylinders having the smallest diameter, and between the adjacent cylinders. A plurality of fan blades formed in various shapes are arranged, and the fan boss and the cylindrical body and adjacent cylindrical bodies are integrally connected and fixed through the fan blades. fan. 2. A fan boss having a shaft fixing portion mounted on a rotary shaft of a drive means at its center axis, and a plurality of cylindrical bodies having different diameters being concentric with the fan boss around the fan boss. The fan boss and each cylinder are integrally driven to rotate in the space between the fan boss and the cylinder having the smallest diameter and between the adjacent cylinders, and air is pumped to the leeward side during the rotation. A plurality of fan blades formed in a possible shape are arranged, and the fan boss and the cylinder body and adjacent cylinder bodies are integrally connected and fixed to each other via these fan blades. The distance between the cylinders having the smallest diameter and the distance between adjacent cylinders are set so as to be limited to the Reynolds number such that the air flow through the gap where the fan blades are arranged becomes a laminar flow when the fan rotates. Axial fan characterized by having done. 3. A fan boss having a shaft fixing portion mounted on a rotary shaft of a drive means at an axial center of a cylindrical portion,
A plurality of thin-plate cylinders having different diameters are arranged around the fan boss cylinder concentrically with the fan boss, and between the fan boss cylinder and the cylinder having the minimum diameter, and between adjacent cylinders. A plurality of fan blades, which are driven to rotate integrally with the fan boss and each cylindrical body and are formed in a shape capable of pumping air to the leeward side at the time of rotation, are arranged in the space of An axial flow fan in which the fan boss and the cylinder and the adjacent cylinders are integrally connected and fixed to each other, and the distance between the fan boss cylinder and the cylinder having the minimum diameter and the distance between the adjacent cylinders are While the fan is rotating, the Reynolds number is set so that the air flow through the air gap in which the fan blade is disposed becomes a laminar flow, and each cylinder and the fan boss cylinder are respectively set to have axes. The fan blades are formed to have a uniform diameter or a shape that gradually expands from the suction side to the discharge side, and the mounting position and number of fan blades are set for each of the gaps, and the front and rear edges of each of the cylindrical bodies are fan blades. An axial fan characterized in that the positional relationship between the two is set so as to be located axially forward or rearward of the front and rear edges.