JPS62206296A - Axial blower - Google Patents

Abstract

PURPOSE:To reduce noises by defining a space between shell and a fan casing with a partition plate to fill each defined chamber with a sound absorbing material. CONSTITUTION:A fan casing 20 is formed with through holes 21 and a space 25 between said casing and a shell 23 is divided by partition plates 27 into defined chambers 28 having about equal volume. The resonance frequencies of respective defined chambers 28 are set to the low frequency region of noise generated by a blower while these defined chambers 28 are filled with sound absorbing materials 29. While noises are absorbed by the absorbing effect of the sound absorbing material 29 mainly in the high frequency region, noises in the low frequency region can be attenuated by the resonance frequency effect.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an axial flow blower, more specifically, a cylindrical fan casing, which is equipped with an electric motor and a fan rotor driven by the electric motor, and which is mainly used for large discharge capacity. relates to an axial blower for use.

(Conventional technology) Generally, an axial flow blower has a structure shown in FIG.

That is, a plurality of guide vanes 2 (for example, 13 guide vanes) are fixedly mounted on a cylindrical fan casing 1 at equal intervals in the circumferential direction, and the ring-shaped attachment of the guide vanes 2 is such that the induction electric motor Ia4 is connected to the cylindrical fan casing 1 through a plate 3. installed. A fan rotor 7 having blades 5 and a hub 6 is connected to the induction motor 4 upstream of the induction motor 4 (on the opposite side from the arrow a). A conduit tube 8 is installed on the top of the induction motor 4.
A terminal box 9 is connected to the upper end of the conduit tube 8 . A nose piece 11 is fixed to the hub 6 on the upstream side of the fan rotor 7. A suction bell mouth 13 is connected to the upstream side of the fan casing 1 for smoothing the flow of incoming air, and a wire mesh 14 is attached to the suction bell mouth 133. Further, a pair of legs 16 are fixed to the lower part of the fan casing 1.

(Problems with the Prior Art) In the structure of the axial blower described above, as the fan rotor 7 rotates and the induction motor 4 rotates, noise at a high sound pressure level is generated over a wide frequency range as shown by the solid line in FIG. 5, for example. Due to the wide frequency range, it has been difficult to take measures to prevent blindness.

(Means for Solving the Problems) The present invention provides an axial flow blower equipped with an electric motor and a fan rotor driven by the electric motor in a cylindrical fan casing, in which a large number of through holes are formed in the rough casing described in U and ii. An outer body 111 is arranged at a predetermined distance on the outer periphery of the fan casing in which these through holes are formed, and the space formed between the outer body and the fan casing is a compartment having approximately the same volume. , about 181 in the axial direction of the fan rotor
The resonant frequency of each of these compartments is set in the low frequency range of the noise emitted by the Fufu-nada, and each of these compartments is filled with sound-absorbing material. Features and 1-piece axial flow J! There are 41 aircraft.

(Embodiment) An embodiment of the present invention is not shown in FIG. 1, and the same reference numerals as in FIG. 4 indicate corresponding parts, and only the differences will be explained below.

In FIG. 1, 20 is a fan casing, and this fan casing 20 has a large number of through holes 21 formed therein. The formation of the through hole 21 is performed as shown in FIG. 2, and the circular through hole 21 is formed having each vertex of an equilateral triangle with one side p as its center. Since the fil holes formed by the transparent holes 21 affect the performance as a blower, it is not desirable to set the pore ratio to a very large value, and the sound absorption effect is 1! It is desirable to set the value near the lowest value of the range.

In this embodiment, for example, when p is 11 m, the diameter d of the through hole 21 is set to 6 meters, and the aperture ratio is 5%.

On the outer circumferential side of the fan casing 20, an outer Fk 423 is arranged at a predetermined distance m (for example, 200 meters) apart, and ring-shaped side walls 24 are fixed at both ends of this outer 1M23. A space 25 is formed by the l1l123 and the ring-shaped side wall 24. this space 2
Ring-shaped partition plates 27 are disposed within the space 5 at equal intervals, and the partition plates 27 divide the space 25 into a plurality of compartments 28 having equal volumes.

This compartment 28 is filled with a sound absorbing material 29, and this sound absorbing material 29 is made of glass wool, for example. This sound absorbing material 29 is filled with a bulk specific gravity of, for example, 32#/m3, and has a structure in which the sound absorbing effect on the high frequency side is sufficiently improved by this sound absorbing material 29.

The resonant frequency fr of this compartment 28 is given by the following equation.

f = (C/2π) × (FσN//V”) where C
;Sound velocity, N: number of through holes, ■=volume of compartment, G: represents conductivity of through holes, G is also expressed as G-A/(t+ar), A: area of through holes, t: thickness of the fan casing, a: constant, r: radius of the through hole.

This resonance frequency fr is the low frequency region 1- shown in FIG.
is set to a certain value. The plate thickness t is approximately determined by the model of the blower, and the aperture ratio is regulated as described above in relation to the performance of the blower.The setting of the resonance frequency f is optimized mainly by adjusting the volume of the compartment. Value is set. In other words, the distance l111m and the partition plate 27
By adjusting the interval, the resonance frequency f is set to a desired value.

The dark part between the nosepiece 11 and the fan [1-7] has a double structure consisting of a cylindrical plate 31 and a cylindrical plate 32.
A space 33 formed by the cylindrical plate 31 and the cylinder &32 is filled with a sound absorbing material 29. A through hole 21 is formed in the cylindrical plate 31 on the outer peripheral side, similar to the fan casing 20.

Next, the operation will be explained. As the fan [1-7] rotates, air flows into the fan casing 20 from the suction bell mouth 13 side, and air flows out from the opposite side of the suction bell mouth 13. Noise is generated as a result of this air flow, but the generated noise is absorbed from the through hole 21 into the compartment chamber 28 located on the upstream and downstream sides in FIG. Therefore, this sound absorbing material 29 mainly absorbs yJ8 in the high frequency region H (FIG. 5), and the maximum noise generation region 111 is absorbed by the volume effect of the compartment 28.
1<near 500 Hz in FIG. 5) is alleviated, and the noise at the low frequency head ML is further attenuated by the effect of an appropriately set resonance frequency.

This effect also works in the space 33, and as a result, sound absorption and noise attenuation effects appear in a wide frequency range from the low frequency range to the high frequency range F1 (dotted line in Figure 5).

(Effects of the Invention) In the axial blower according to the present invention, a large number of through holes 21 are formed in the fan casing 20, and an external I.
N 23 is installed, and the outer shell 23 and the casing 2
A compartment 28 in which the space 25 formed between 0 and 0 has approximately the same volume
The resonant frequency f of each compartment 28 is divided by a partition plate 27.

But, send it! The sound absorbing material 29 is set in each of these compartments 28, so that the sound absorption effect of the sound absorbing material 29 mainly reduces noise in the high frequency region 1. In addition to absorbing
It is possible to attenuate the noise in the vicinity of the maximum noise generation region T1 by the volume effect of the compartment 28, and further to attenuate the noise in the low frequency region by the resonant frequency effect, and from the low frequency region to the high frequency region 1. A wide range of noise can be effectively reduced. Moreover, compartment 28
Since the capacity is set to the optimum capacity, a lot of space is not required for lA sound attenuation, and noise can be absorbed in a short width. Therefore, it is possible to provide an axial blower that generates extremely low noise.

[Brief explanation of drawings]

Fig. 1 is a longitudinal side view showing an embodiment of the present invention, Fig. 2 is a partially enlarged side view of fan gauging, Fig. 3 is a partially enlarged longitudinal side view of the compartment, and Fig. 4 is a polygonal longitudinal side view of the conventional example. figure,
FIG. 5 is a graph that does not show the noise generation situation. 4...
- Induction motor, 7... Fan rotor, 20... Fan casing, 21... Through hole, 23... Outer body, 25
... Space, 27 ... Partition plate, 28 ... Compartment room, 2
9...Sound absorbing material, r r-...Resonance frequency,...Low frequency range patent applicant N.G.I. Axibane Co., Ltd. Agent Patent attorney Tadataka Daigari ′,・11-′ 1□”− Figure 5B

Claims (2)

[Claims] (1) In an axial flow blower equipped with an electric motor and a fan rotor driven by the electric motor in a cylindrical fan casing, a large number of through holes are formed in the fan casing, and the fan casing in which these through holes are formed is An outer shell is arranged at a predetermined distance on the outer periphery, and a space formed between the outer shell and the fan casing is a compartment having approximately the same volume;
The fan rotor is divided by partition plates arranged at approximately equal intervals in the axial direction of the fan rotor, and the resonant frequency of each compartment is
An axial flow blower characterized by being set in a low frequency range of noise emitted by the blower, and each of these compartments being filled with a sound absorbing material. (2) The axial blower according to claim 1, wherein the divided chambers are formed at least one chamber upstream and a plurality of chambers downstream of the installation position of the fan rotor.