JPH06108996A - Fan - Google Patents

Abstract

PURPOSE:To prevent the generation of separating flow positively without generating air swishing sound or the like by providing the negative pressure side face of a blade with plural L-shape recessed parts in a fan provided with plural blades around a hub. CONSTITUTION:In a fan 1, plural blades 3 are provided around a hub 2 formed into approximately cylindrical shape, and L-shape recessed parts 6 serving as a separating flow preventing part 5 are formed at the surface of the negative pressure side face 4 of the blade 3. This separating flow preventing part 5 is disposed in the grated state over the whole upper face of the negative pressure side face 4 in relation to the flowing direction A of an air current. The longitudinal pitch P1 and lateral pitch P2 of this separating flow preventing part 5 is set to satisfy tantheta0=P1/P2, where theta0 is the angle of the air current to the rotary shaft of the fan. The air current flowing in at the angle theta0 to the rotary shaft of the fan therefore passes the separation flow preventing part 5 without fail, so that the development of a boundary layer caused by separation at the negative pressure side face of the blade is prevented, and as a result, noise is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan, and more particularly to a fan with reduced noise.

[0002]

2. Description of the Related Art Conventionally, a fan blade 10 is generally shown in FIG.
Was formed by a substantially smooth surface.

When a fan using such a blade 10 is operated, the airflow flowing on the suction side 11 of the blade 10 is separated into the boundary layer of the airflow in the vicinity of the surface of the downstream side thereof.
2 had occurred. Then, due to the generation of the separated flow 12 as described above, the operation efficiency of the fan itself is reduced and the noise is also increased.

Therefore, for example, Japanese Utility Model Laid-Open No. 63-160399.
The fan 10 having the structure shown in Japanese Patent Publication No.
The generation of the separated flow 12 on the negative pressure side surface 11 is performed.

That is, as shown in FIG. 5, the fan blades 13
A pair of recesses (or protrusions) are formed as the separation flow prevention portion 15 on the upstream side of the suction side surface 14 of the suction pressure side surface 14 in the axial direction, and the separation flow prevention portion 15 is formed.
The transition of the boundary layer to the turbulent boundary layer in the upstream part of the air flow improves the operation efficiency of the fan body and reduces noise.

[0006]

However, in the above-described case where the uneven flow preventing portion is formed on the upstream side portion of the suction side surface of the blade, the separate flow preventing portion is formed only on the upstream side portion. Therefore, the boundary layer in the upstream part of the airflow can be transited to the turbulent boundary layer, but the airflow passing through this separation flow prevention part grows in the latter half of the blade, resulting in In particular, there is a problem that a relatively large separated flow is generated near the surface of the downstream side portion.

Further, the convex shape itself causes wind noise, and the concave shape reduces the strength of the upstream side portion.

Therefore, considering the strength of the fan blade as shown in FIG. 6 (a), the separation flow prevention portion 16 is formed into a substantially circular shape to increase the mutual pitches P ₁ and P ₂ and decrease the diameter l. However, there is an air flow that does not pass through the separation flow prevention unit, and thus the generation of the separation flow cannot be reliably prevented.

Further, as shown in FIG. 6 (b), it is conceivable to increase the diameter l'of the separation flow prevention part 17 so that all the airflow passes through the separation flow prevention part. The larger the diameter of the part, the lower the turbulence effect and the thicker the boundary layer, so that it is impossible to effectively prevent the generation of the separated flow.

The present invention solves the above problems and maintains the strength of the wing without generating wind noise or the like.
An object of the present invention is to provide a fan capable of improving the operation efficiency of the fan body and reducing noise by surely preventing the generation of a separated flow.

[0011]

In order to solve the above-mentioned problems, the first invention of the present application is a fan in which a plurality of blades are provided around a hub formed in a substantially cylindrical shape. It is configured by providing a plurality of L-shaped recesses on the side surface.

The second aspect of the present invention is configured so that the corners of the L-shaped recess provided on the suction side surface of the blade are opposed to each other in the air flow inflow direction.

[0013]

According to this structure, since the recess serving as the separation flow prevention portion is not enlarged, the strength of the blade does not decrease and the turbulent flow effect does not decrease. Moreover, since all the airflows effectively pass through the concave portion as the separation flow prevention portion,
It is possible to reliably prevent the generation of a separated flow.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the fan 1 comprises a plurality of blades 3 provided around a hub 2 formed in a substantially cylindrical shape.
An L-shaped concave portion 6 is provided as a separation flow prevention portion 5 on the surface of the negative pressure side surface 4. The separation flow prevention unit 5 is arranged in a lattice shape over the entire suction side surface 4 of the blade in the flow direction A of the air flow. The vertical pitch P of the separation flow prevention unit 5
₁ and the lateral pitch P ₂ are set as follows, where θ ₀ is the angle of the airflow with respect to the rotation axis of the fan.

[0016]

## EQU1 ## tan θ ₀ = P ₁ / P ₂

Then, the L-shaped corner portion 7 is arranged corresponding to this pitch, and with this corner portion 7 as a reference point B, the L-shaped longitudinal piece 8 is angle θ _{1 with} respect to the air flow direction A, Lateral piece 9
At an angle θ ₂ to form an L-shaped recess (here, θ ₀
= Θ ₁ ).

At this time, if the ratio of the air flow passing through the separation flow prevention portion 5 is Ψ, the respective values of the vertical piece length L ₁ and the horizontal piece length L ₂ are as follows so that 0.9> Ψ. It is determined based on the formula.

[0019]

2>0.9> Ψ = (L ₁ sin θ ₁ + L ₂ sin θ ₂ ) / P ₁ sin θ ₀

Further, if the depth t of the recess 6 is formed so as to satisfy 5% <t / T <50% with respect to the thickness T of the blade, the reliability can be ensured in terms of strength. .

In this way, the airflow flowing in at an angle of θ ₀ with respect to the rotation axis of the fan always passes through the separation flow prevention unit 5, and the boundary layer of the boundary layer due to separation on the suction side of the blade is formed. Development is prevented, as shown in Figure 2, 1500 m ³ /
1.0dB for h without hose
A, 0.5 for those with a circular separation flow prevention part
The dBA noise will be reduced.

[0022]

As described above, according to the present invention, in a fan in which a plurality of blades are provided around a hub formed into a substantially cylindrical shape, a plurality of L-shaped recesses are formed on the suction side surface of the blade. By providing the blades, it is possible to reliably prevent the generation of separated flow without generating wind noise while maintaining the strength of the blades, thereby improving the operating efficiency of the fan body and reducing noise.

[Brief description of drawings]

FIG. 1 is a diagram showing a fan according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a noise characteristic diagram of the present invention.

FIG. 4 is a blade cross-sectional view of a conventional fan.

FIG. 5 is a view showing a separation flow prevention unit of a conventional fan.

FIG. 6 is a diagram showing another separation flow prevention unit of a conventional fan.

[Explanation of symbols]

1 ... Fan, 2 ... Hub, 3 ... Wing, 4 ... Suction side, 6 ... L
-Shaped recess, 7 ... Corner

Claims (2)

[Claims] 1. A fan comprising a plurality of blades provided around a substantially cylindrical hub, wherein a plurality of L-shaped recesses are provided on the suction side surface of the blade. 2. The fan according to claim 1, wherein the corners of the L-shaped concave portion provided on the suction side surface of the blade are opposed to each other in the air flow inflow direction.