JP3391199B2 - Centrifugal fan - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal fan capable of reducing noise.

[0002]

2. Description of the Related Art In a centrifugal fan, air is given energy by a centrifugal force, and the energy increases toward the outer peripheral direction. Therefore, if the ratio of the relative velocity of the air flow, which will be described later, in the centrifugal fan and the peripheral velocity is made constant and the relative velocity increases toward the outer periphery, the air flow in the centrifugal fan can be made smooth. .

[0003]

In the conventional centrifugal fan, the relative speed and the peripheral speed are not equal to each other, which causes turbulence in the flow in the blade and causes noise. An object of the present invention is to smooth the air flow in the blades and reduce noise by equalizing the ratio of the relative speed and the peripheral speed in the centrifugal fan.

[0004]

The above object is to define the area consisting of the product of the blade spacing and the blade height of the inlet and outlet of each blade as S ₁ and S ₂ , respectively, and to determine the diameter of the inlet of each blade and When the diameters of the outlets are D ₁ and D ₂ , respectively, S ₁ × D ₁ = (1 ± 0.
3) It is achieved by setting the blade height and the blade interval so as to satisfy the relational expression of × S ₂ × D ₂ . Also, by making the product of the space between the blades at the radial position of the centrifugal fan and the product of the blade height and the radius equal at all radial positions, the air flow inside the blades becomes smoother. Achieved by

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment of the present invention is shown in FIGS.
Will be described. The centrifugal fan of the present invention includes a disk-shaped fan main body 1, a plurality of blades 2 extending from a predetermined radial position of the fan main body 1 to an outer peripheral end, and formed at a predetermined pitch along the circumferential direction of the fan main body 1, the fan main body 1. Is provided in the center of
It is composed of a hub 3 and the like attached to a rotating shaft (not shown). As shown in FIG. 1, the blade 2 is formed so that its height changes at a radial position. When the centrifugal fan is rotated, energy is given to the air by the centrifugal action. By attaching the fan guide 4 to the side portion of the centrifugal fan, the air flowing along the axial direction passes through the inlet portion which is the inner peripheral end of the blade 2 and is discharged outward in the radial direction from the outlet portion which is the outer peripheral end. To be done.

The diameter of the outlet of the blade 2 (hereinafter simply referred to as the outer diameter)
The distance between the blades ₂ in D ₂ and the height of each blade 2 are L ₂ and b, respectively, the diameter of the inlet portion of the blade 2 (hereinafter simply referred to as the inner diameter), the distance between the blades 2 in D _1, and the blade 2 When the heights are L ₁ and h, respectively, the inlet area S ₁ between the blades 2 is
The outlet area S ₂ can be expressed by the following equation. S ₁ = L ₁ × h S ₂ = L ₂ × b As shown in FIG. 2, when the centrifugal fan rotates, the velocity component of the air at the inlet of the centrifugal fan is equal to the peripheral velocity U ₁ and each blade 2. Relative velocity W ₁ and the velocity components at the outlet are peripheral velocity U ₂ and relative velocity W ₂ . Note that C ₁ and C _{2 in the} figure are velocities obtained by combining the peripheral velocity and the relative velocity, and this is called the absolute velocity. The ratio between the inlet relative speed W ₁ and the inlet peripheral speed U ₁ is λ ₁ , and the ratio between the outlet relative speed W ₂ and the outlet peripheral speed U ₂ is λ _2.
Then, since the inlet air volume Q ₁ and the outlet air volume Q ₂ are products of their respective areas and relative velocities, they can be expressed by the following equations. Q ₁ = S ₁ × W ₁ = S ₁ × λ ₁ × U ₁ Q ₂ = S ₂ × W ₂ = S ₂ × λ ₂ × U _{2 If} the angular velocity of the centrifugal fan is ω, the above formula becomes Q ₁ = S _{1 × λ 1 × ω × D} 1/2 Q 2 = the _{S 2 × λ 2 × ω ×} D 2/2. Since the air volume in the blade 2 is the Q ₁ = Q _2, the _{S 1 × λ 1 × ω ×} D 1/2 = S 2 × λ 2 × ω × D 2/2. At this time, if λ ₁ = λ ₂ , the ratio between the relative velocity and the peripheral velocity U becomes equal, and the air flow can be made smooth. For that purpose, S ₁ × D ₁ = S ₂ × D ₂ may be set. These relationships are true for both the radial fan shown in FIG. 2 and the turbo fan shown in FIG. 3. In the turbo fan shown in FIG. 3, the intervals L ₁ and L ₂ between the blades 2 are the distances perpendicular to the blades 2. And

In order to confirm the effect of the present invention, FIG. 5 shows the results of measuring the noise and the air volume while changing the ratio of the inlet area S ₁ to the outlet area S ₂ . The outer diameter D ₂ was φ68 mm, the inner diameter D ₁ was φ43 mm, and the height h at the entrance of the blade 2 was 9 mm.
The conventional centrifugal radial fan was used and the measurement was performed by changing the height b of the outlet and changing the ratio of the area S ₁ of the inlet and the area S ₂ of the outlet. The rotation speed of the centrifugal fan is 10
000 rpm was kept constant. The centrifugal fan used in the experiment is D
₁ / D ₂ = 0.63. From the experimental results, the conventional centrifugal fan shown by the black circles in FIG. 5 has S ₂ / S ₁ = 1.13, and therefore S ₁ × D ₁ = 0.56 × S ₂ × D ₂ . As the outlet area S ₂ is reduced, the noise level becomes lower. This is because the outlet area S ₂ is reduced by S ₂
This is because the value of × D ₂ approaches the value of S ₁ × D ₁ . The outlet / inlet area ratio is 0.9, which is 3 (≒
62-59) dB lower, and the effect of the present invention can be seen. At this time, the inlet area S ₁ , the inner diameter D ₁ and the outlet area S _1
2 , the relationship between the outer diameter D ₂ is S ₁ × D ₁ = 0.7 × S ₂ × D ₂ . Noise level becomes the lowest in S ₂ / S ₁ = 0.55, which is the time _{S 1 × D 1 = 1.15 ×} S 2 × D 2. As described above, when the product of the inlet area and the inner diameter and the product of the outlet area and the outer diameter are made substantially equal, that is, when the ratio of the inlet area S ₁ and the outlet area S ₂ is S ₂ / S ₁ = 0.63. The noise level should be minimal, but the experimental results shown in Figure 5 do not. This is because the above formula is obtained by using an ideal model. From the experimental results shown in FIG. 5, it can be seen that when S ₁ × D ₁ = ( 1 ± 0.3 ) × S ₂ × D ₂ is satisfied, the noise level becomes low and the air volume becomes almost the same. That is, it is not necessary to make the products exactly equal, and a 30% margin can be provided.

It is most effective to form the product of the area and the diameter of the flow passage from the inner diameter to the outer diameter as shown in FIG. 4, but the product of the inlet area S ₁ and the inner diameter D ₁ and the outlet area are most effective. Even if the shape shown in FIG. 1 in which the product of S ₂ and the outer diameter D ₂ is made substantially equal and the height of the blade 2 is changed linearly from the inlet height h to the outlet height b is obtained as described above. You can

If the side plate 5 is attached to a part of the blade 2 of the centrifugal fan as shown in FIG. 6, the same effect can be obtained without using the fan guide 4.

[0010]

According to the present invention, the noise level can be reduced without degrading the performance of the centrifugal fan.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a centrifugal fan of the present invention.

FIG. 2 is a front view of a radial fan.

FIG. 3 is a front view of a turbo fan.

FIG. 4 is a sectional view showing another embodiment of the centrifugal fan of the present invention.

FIG. 5 is an experimental measurement diagram showing the effect of the present invention.

FIG. 6 is a sectional view showing still another embodiment of the centrifugal fan of the present invention.

[Explanation of symbols]

1 is a fan body, 2 is a blade, 3 is a hub, 4 is a fan guide, and 5 is a side plate.

Claims (2)

(57) [Claims] 1. A disk-shaped fan body is formed with blades extending from a predetermined radial position to an outer peripheral end and having heights varying depending on the radial position at a predetermined pitch along the circumferential direction of the fan main body.
A centrifugal fan in which air along the axial direction is allowed to flow outward in the radial direction, and the areas formed by the product of the blade spacing and the blade height at the inlet and outlet of each blade are S ₁ and S ₂ , respectively. , When the diameter of the inlet and the diameter of the outlet of each blade are D ₁ and D ₂ , respectively, the relational expression of S ₁ × D ₁ = (1 ± 0.3) × S ₂ × D ₂ is satisfied. The centrifugal fan is characterized in that the blade height and the blade interval are set. 2. A disk-shaped fan body is formed with blades extending from a predetermined radial position to an outer peripheral end, the height of which is different depending on the radial position, at a predetermined pitch along the circumferential direction of the fan main body.
A centrifugal fan in which air along the axial direction is allowed to flow outward in the radial direction, and the product of the area and the radius, which is the product of the blade spacing and blade height, reaches all the outlets from the inlet to the outlet. A centrifugal fan characterized in that the radial positions are equal.