JPH0143520Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a noise muffling device for a centrifugal compressor.

A centrifugal compressor generates a unique high-frequency noise due to the number of rotations of the impeller and the number of blades. Conventionally, in order to deal with such noise, it has been common practice to provide a discharge muffler. However, this conventional method not only requires a special muffler on the discharge side, but also requires space in the piping for installing the muffler, which makes it difficult to downsize, especially in compressors where downsizing is required. Along with becoming a netsuku,
There were problems such as the entire device being expensive.

The present invention solves the problems of the conventional method described above, and at the same time effectively muffles noise on the suction side of the centrifugal compressor, and also enables noise muffling that can respond to changes in the rotational speed of the centrifugal compressor. An inner chamber is formed by the blower inner member forming a part of the volute chamber, the diffuser, the suction side wall, and the fan wheel cover, and the inner chamber is located at the suction side of the compressor. A resonant type muffler is created by communicating with the muffler through the resonant hole. This allows effective noise reduction on the suction side without any special equipment. Furthermore, since the temperature in the inner chamber increases as the rotational speed increases, it is also possible to muffle noise in response to changes in the rotational speed.

Embodiments of the present invention will be described below based on the drawings.

Generally, when the discharge/suction noise of a centrifugal compressor is frequency-analyzed, as shown in FIG. 1, the high-frequency component A becomes large depending on the rotation speed of the impeller and the number of blades. Therefore, it is a very effective means to perform a resonant silencing action tailored to this frequency _f1 .

FIG. 2 shows an example of a centrifugal compressor to which the present invention is applied. In the figure, 1 is a vortex chamber, and the vortex chamber 1 is formed between an outer wall 3 of a blower outer member 2 and a blower inner member 4. It is formed by an inner wall portion 5 and a diff user 6. Further, further inside the blower inner member 4, an inner wall portion 5 and a suction side wall portion 7 of the blower inner member 4, and a fan wheel cover 8,
An inner chamber 9 surrounded by a diffuser 6 is formed. Further, 10 is a partition wall, 11 is a rotating shaft, 1
2 is an impeller, 13 is an inducer, and 14 is an air suction part.

In the above configuration, if it is confirmed that the noise of the compressor is largely caused by the suction side, and if the noise on the suction side can be reduced, the overall noise level of the compressor can be significantly reduced. , this problem was achieved by utilizing the inner chamber 9.

That is, resonance holes 18 and 1 are provided on the suction side of the compressor, such as the suction side wall portion 7 and the fan wheel cover 8 in the blower inner member 4, for communicating the air suction portion 14 with the inner chamber 9.
9 is opened to form a resonance type muffler that reduces noise on the suction side.

As mentioned above, by making the inner chamber 9 communicate with the suction side of the compressor to form a resonance type muffler, the structure of the centrifugal compressor can be used to eliminate the noise from the source without providing a special muffler. noise can be effectively silenced. Further, when the resonance holes 19 are used to resonancely muffle the noise on the suction side, the resonance holes 19 can be placed close to the blades that are the noise source, so that the noise of the entire compressor can be significantly reduced.

Generally, the efficiency of a centrifugal compressor increases when the blade inlet of the differential user 6 is brought closer to the outer diameter of the impeller, but there is a certain limit due to the increase in noise. According to the present invention, it is possible to further expand this limit and improve efficiency.

Moreover, when the rotation speed of the centrifugal compressor changes,
Generally, the frequency of the noise will also change. At this time, as shown in Fig. 3, even if the rotation speed of the compressor increases, the air temperature on the suction section 14 side remains constant and does not change, but the air temperature on the discharge side is approximately proportional to the square of the rotation speed. There will be major changes, and for this reason,
The temperature of the air in the inner chamber 9 which is in contact with the discharge side via the inner wall portion 5 of the diffuser 6 and the blower inner member 4 changes due to the heat transfer effect. Therefore, the resonant frequency also changes as V ₀ ′−V ₀ ″, and since the change in the resonant frequency and the change in the frequency of the noise are in the same direction, a certain amount of rotation occurs. It becomes possible to mute the sound in response to a change in the number.

It should be noted that the present invention is not limited to the above-described embodiments, and that the shape, position, etc. of the resonance hole that communicates between the inner chamber and the external noise generating part can be changed in various ways, and other gist of the present invention. Of course, various changes may be made within the scope of the invention.

According to the noise reduction device for a centrifugal compressor of the present invention described above, the following excellent effects can be achieved.

(i) Noise can be reduced without installing a special muffler outside the pipes, etc.

(ii) Since the structure is extremely simple using the configuration of a compressor, it can be implemented at a very low cost.

(iii) The silencer does not become an obstacle to downsizing the compressor.

(iv) Since noise is immediately silenced at the noise generating part on the suction side, effective noise reduction is possible, and it is therefore possible to increase the efficiency of the compressor by bringing the impeller inlet of the diffuser closer to the outer diameter of the impeller. becomes.

(v) Since the inner chamber is in contact with the blower inner member and the diff user, and the internal temperature changes according to changes in the rotation speed, the resonant frequency also changes, and therefore, due to changes in the rotation speed to a certain extent. You can also mute the sound.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between frequency and noise level, Fig. 2 is a cross-sectional view showing an embodiment of the present invention,
FIG. 3 is a diagram showing the relationship between rotational speed, air temperature at various parts, and resonance frequency. 1 is a swirl chamber, 4 is a blower inner member, 5 is an inner wall, 6 is a diffuser, 7 is a suction side wall, 8 is a fan cover, 9 is an inner chamber, and 18 and 19 are resonance holes.

Claims (1)

[Scope of utility model registration request] An inner chamber is formed by a blower inner member forming a part of the swirl chamber, a diffuser, a suction side wall portion, and a fan wheel cover, and the inner chamber is communicated with the suction side position of the compressor via a resonance hole. A noise muffling device for a centrifugal compressor, characterized in that it is a resonance type muffling device.