JPH0544686A - Cross current fan - Google Patents

Abstract

PURPOSE:To provide a cross current fan having the low noise level and high efficiency. CONSTITUTION:The outer peripheral side of an impeller B of a blade 11 of the impeller B and the rear side of the blade 11 is formed from each plane 12, so as to be thinner on the outer edge side of the blade 11. Accordingly, the outer edge side of the blade 11 is formed to a wedge shape by cutting the outer edge side and rear side of the arcuate blade 11 by the plane 12. Accordingly, on the outlet side of a cross current fan, the width of an alterating current separated from the blade 11 of the flow which flows along the blade 11 is reduced. Accordingly, the noise level is reduced, and efficiency is improved.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a cross-flow fan is provided with an impeller A having a plurality of arcuate blades 1 curved forward (arrow X direction) and a casing 3 having a tongue 2. . As shown in FIG. 1 (a), the blade 1 of the impeller A is formed by an arcuate surface having the same curvature R on the front side and the rear side, and the blade 1 has the same thickness over the whole. There is. The inclination β _{1 of the} blade 1 with respect to the inscribed circle of the impeller A
= 90 °, inclination of blade 1 with respect to circumscribed circle of impeller A β ₂ = 2
5 °, radius of curvature of wing 1 R = 14.9 mm, chord l = 17.7 m
m, blade thickness t = 2 mm.

In FIG. 5, the impeller A has an arrow X.
When rotating in the direction shown by (6), the air flows through the impeller A as shown by the streamline F and is discharged from the outlet 6.

[0004]

By the way, in the above-mentioned conventional cross-flow fan, since the thickness of the arc blade 1 is the same on the outer peripheral side and the inner peripheral side of the impeller A, the blade 1 on the outlet 6 side has the same thickness. There is a problem in that the width of the wake, that is, the width of the wing 1 in the thickness direction of the wake increases, and noise increases.

Therefore, an object of the present invention is to provide a cross-flow fan capable of reducing noise.

[0006]

In order to achieve the above object, the present invention relates to a cross-flow fan comprising an impeller having a plurality of forwardly curved arcuate blades and a casing, wherein the blades are on the outer peripheral side of the impeller. It is characterized in that the outer peripheral side of the impeller and the rear side of the blade are formed to be flat so as to be thinner.

[0007]

The blade of the impeller of the cross-flow fan has a wedge shape in which the outer peripheral side of the impeller and the rear side of the blade are cut off with a plane, so that the blade is It gradually becomes thinner after the flow. Therefore, on the outlet side of the cross-flow fan, the width of the air flowing along the blades in the thickness direction of the blades gradually narrows, and the air flow does not suddenly separate from the blades. The width of the direction becomes thin. Therefore, noise is reduced and the efficiency of the cross flow fan is improved.

[0008]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. In the cross flow fan of this embodiment, the casing has exactly the same structure as the conventional casing 3 shown in FIG. 5, and only the structure of the impeller is different from the conventional one. Therefore, FIGS. 1 (a) and 1 (b) show the conventional impeller A and the impeller B of this embodiment for comparison.

As shown in FIG. 1 (b), an impeller B of this embodiment has the blade 1 of the impeller A shown in FIG. 1 (a) on the outer peripheral side of the impeller A and on the rear side of the blade 1. Is cut away by the plane 12 shown in FIG. 1 (b), and the outer end side of the blade 11 has a wedge shape, and the other portions have the same structure as the blade shown in FIG. 1 (a). ing. That is, the radius of curvature R of the blade 11 of this embodiment is R = 14.9 mm as in the conventional case, and the chord l is 1 = 17.7 mm as in the conventional case. However, the length l ′ of the flat surface 12 obtained by cutting the outer side and the rear side of the blade 11 is 7 mm, and the wall thickness t ′ of the tip on the outer end side of the blade 11 is 0.5 mm.
The wall thickness t of the blade not cut is t = 2 mm, which is the same as the conventional one.

Next, the experimental data conducted to compare the characteristics of the cross flow fan of the embodiment shown in FIG. 1 (b) and the cross flow fan shown in FIG. 5 and FIG. 1 (a) are shown below. The experiment was conducted at a rotation speed of the impellers A and B of 1,000 rpm.

In FIG. 2 (a), the horizontal axis is the flow coefficient φ, and the vertical axis is the total pressure efficiency η. The data of the cross flow fan using the impeller B of this embodiment shown in FIG. 1 (b) is marked with a circle. The data of a cross-flow fan using the conventional impeller A shown in FIG. This is the same for all figures below. Figure 2
In Fig. 2 (c), the horizontal axis shows the flow coefficient φ, the vertical axis shows the total pressure coefficient ψ.
Is the flow coefficient φ on the horizontal axis and the power coefficient on the vertical axis. Figure 2 (a)
As can be seen from the above, it was found that the total pressure efficiency η of the present embodiment is improved by about 10% as compared with the conventional one at the highest point. The reason for this is that, as shown in FIG. 2 (b), the total pressure coefficient ψ is almost unchanged with respect to most of the flow coefficient φ, but as shown in FIG. This is because the power coefficient is improved. It is considered that the improvement of the total pressure efficiency η is due to the fact that the blade 11 has a wedge shape on the outlet 6 side, and no vortex can be formed at a position where the flow along the blade 11 separates from the blade.

Next, FIGS. 3 and 4 show comparison of experimental data of noise between the present embodiment and the conventional example. FIG. 3 (a) shows the sound pressure level of the first-order blade passing frequency for the flow coefficient φ. That is, N (rotational speed of the impeller / second) and z (number of blades), and when Nz = 450, 450 Hz (first order)
The sound pressure level of is shown for each flow coefficient φ.
FIG. 3B shows the secondary (900 Hz) sound pressure level.
As can be seen from Fig. 3 (a), the impeller B of this embodiment has a higher primary sound pressure level than the conventional impeller A. However, as can be seen from Fig. 2 (b), 2
The next sound pressure level is significantly lower in the present embodiment than in the conventional example. As described above, in the present embodiment, the sound pressure level of the first order is higher than that of the conventional example, but the sound pressure level of the second order is lower, so that as shown in FIG.
The noise level is lower for each flow coefficient φ than the conventional one.

As described above, according to this embodiment, the noise level is lowered. The reason is that on the outlet 6 side of the cross-flow fan, the rear side of the flow of the blade 11 is gradually thinned in a wedge shape, so that the flow of the blade 11 along the blade 11 is reduced.
It is thought that this is because the width of the wake becomes narrower after leaving the area.

It should be noted that the sound pressure level did not change much in comparison with the conventional one in most flow coefficient as shown in FIG. 4 (b). In the above embodiment, in order to compare with the conventional example, the chord l, the radius of curvature R of the blade, and the inclination β ₁ on the inner diameter side of the blade
The inclination β _{2 on the} outer diameter side is the same as that of the conventional example, but the present invention is not limited to such numerical values and can be applied to various numerical values.

However, the ratio t '/ t between the thickness t'of the tip on the outer peripheral side of the blade and the thickness t of the blade is 0.2 to 0.3, and the length l'of the cut surface and the chord It was found that the ratio l '/ l with l is effective when it is 0.3 to 0.5.

[0016]

As is apparent from the above, in the cross-flow fan of the present invention, the outer peripheral side of the impeller of the arc blade and the rear side of the arc blade are cut off with a flat surface so that the outer edge side of the arc blade becomes thinner. Since it has a wedge shape, the width of the wake separating from the blade on the outlet side of the cross flow fan is narrowed, so that noise can be reduced and efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a view showing a conventional impeller of a cross-flow fan and an impeller of a cross-flow fan of an embodiment of the present invention in comparison.

FIG. 2 shows the relationship between the flow coefficient and the total pressure efficiency of the impeller of this embodiment and the conventional impeller, the relationship between the flow coefficient and the total pressure coefficient,
It is a figure which respectively shows the relationship between a flow coefficient and a power coefficient.

FIG. 3 is a diagram showing a relationship between a flow coefficient and a primary blade passing frequency sound pressure level, and a relationship between a flow coefficient and a secondary blade passing frequency sound pressure level.

FIG. 4 is a diagram showing a relationship between a flow coefficient and a noise level, and a relationship between a flow coefficient and a sound pressure level, respectively.

FIG. 5 is a diagram showing a conventional cross-flow fan.

[Explanation of symbols]

A, B ... Impeller, 1, 11 ... Wing, 2 ... Tongue, 3 ... Casing, 6 ... Exit, 12 ... Plane.

Claims (1)

[Claims] 1. A cross-flow fan including an impeller having a plurality of forward-curved arcuate blades and a casing, wherein the blades are formed on the outer peripheral side of the impeller and on the outer peripheral side of the impeller so that the outer peripheral side of the impeller becomes thinner. A cross-flow fan characterized in that the rear side of the blade is formed as a flat surface.