JP2003343486A - Centrifugal compressor equipped with long-and-short impeller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor equipped with a long-and-short impeller capable of reducing blade passing frequency noise by long vanes and maintaining high compression performance. <P>SOLUTION: The centrifugal compressor is equipped with a long-and-short impeller 3 which has long vanes 1 having long blade length extending to the delivery side from the suction side, and short vanes 2 having short blade length provided at the center part between long vanes and extending from the center part to the delivery side. A communicating passage 6 (a plow tooth-shaped groove 6A, a circumference groove 6B and clearance 6C) is provided on a shroud 4 surrounding the outer peripheral part of the long vanes 1 or the impeller of the inducer part introducing air along the rotation direction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a centrifugal compressor provided with an impeller having long and short blades.

[0002]

2. Description of the Related Art As an impeller of a centrifugal compressor used for a supercharger or the like, an impeller having long and short blades shown in FIG. 3 (hereinafter referred to as "long and short impeller") is widely used. This long / short impeller has a long blade 1 having a long blade length extending from the suction side to the discharge side of the impeller, and a short blade 2 having a short blade length provided in the middle of the long blades and extending from the intermediate position to the discharge side. Consists of. Generally, the higher the number of blades in the impeller, the higher the pressure ratio can be obtained. However, if only the long blades 1 are increased, the blade spacing on the suction side becomes narrower, and the air suction (swallow) becomes worse. Therefore, the long and short impellers have a wider blade interval on the suction side than the impellers with only the long blades, and thus swallow well, and the centrifugal part that contributes to compression has a large number of blades, which results in a high pressure ratio. Can be obtained.

FIG. 4 is a distribution diagram of static pressure on the blade surface of the shroud portion. As shown in this figure, a positive pressure is generated on the ventral side and a negative pressure is generated on the back side on the blade surface of the rotating long blade 1, and the pressure difference between the positive and negative pressure surfaces of the blade becomes large. Therefore, by the rotation of the long blade 1,
Positive pressure and negative pressure rotate with the blade, and noise is generated due to this pressure change.

FIG. 5 is a diagram showing the relationship between noise frequency and sound pressure level in a centrifugal compressor equipped with a long and short impeller. As shown in this figure, in the centrifugal compressor equipped with the long and short impellers, peaks of the sound pressure level are observed at two locations, that is, the number of long blades × the frequency of rotation and the number of all blades × the number of rotations. This frequency is taken as the blade passing frequency (BPF: Blade Passing Fr).
This is called "equency". Further, noise at this frequency is abbreviated as BPF sound.

[0005]

As described above, the centrifugal compressor equipped with the long and short impellers has high performance, but has a problem of large noise. Among these noises, the BPF noise of the long blades was particularly large, and the pressure difference between the positive and negative pressure surfaces of the long blades was the main cause of the noise. Therefore, it is possible to reduce the BPF sound of the long blades by reducing the pressure difference in the inducer portion, but it is difficult to reduce only the pressure difference in the relevant portion with the conventional design, and it is difficult to reduce the fluid performance. There was a problem that the impact would be large.

The present invention was devised to solve such problems. That is, an object of the present invention is to provide a centrifugal compressor equipped with a long / short impeller that can reduce BPF noise (blade passing frequency sound) due to long blades and can maintain high compression performance.

[0007]

According to the present invention, a long blade (1) having a long blade length extending from the suction side to the discharge side,
In a centrifugal compressor provided with a long and short impeller (3) having a short blade (2) having a short blade length that is provided in the middle of the long blade and extends from the intermediate position to the discharge side, in an inducer section for introducing air. A centrifugal compressor provided with a long and short impeller, characterized in that a shroud (4) surrounding the outer periphery of the long blade (1) or an impeller is provided with a communication passage (6) along the rotational direction.

According to the above-mentioned structure of the present invention, the communication passage (6) is provided along the rotation direction in the shroud (4) surrounding the outer peripheral portion of the long blade (1) of the inducer section for introducing air or the impeller.
Is provided, the positive pressure side and the negative pressure side of the outer peripheral portion of the long blade (1) are communicated with each other through the communication passage (6) to reduce the pressure difference and reduce the pressure difference in the inducer section. This can reduce the BPF sound of the long blades. Moreover, since the communication passage (6) is provided only in the inducer section, the centrifugal section that contributes to compression is less affected, and high compression performance can be maintained.

According to a preferred embodiment of the present invention, the communication passages (6) are formed from the leading edge of the long blade (1) to the short blade (2).
Is a veil-shaped groove (6A) which is provided on the outer peripheral portion of the long blade up to the front edge of and is axially spaced. With this configuration, since the positive pressure side and the negative pressure side of the outer peripheral portion of the long blade (1) are directly communicated with each other via the vase-shaped groove (6A) provided on the outer peripheral portion of the long blade, other than the outer peripheral portion of the long blade. Can be less affected.

Further, according to another preferred embodiment, the communication passage (6) is provided on the inner peripheral surface of the shroud (4), and comprises a plurality of circumferential grooves (6B) axially spaced from each other. is there. With this configuration, the positive pressure side and the negative pressure side of the outer peripheral portion of the long blade (1) communicate with each other via the plurality of circumferential grooves (6B) provided on the inner peripheral surface of the inducer portion, so that the structure of the long and short impeller is provided. Can be left as is.

Further, according to another preferred embodiment, the communication passage (6) is a gap (6C) between the long blade (1) and the shroud surrounding the long blade (1), and the gap (6C) is the short blade. It is set larger than the gap (2C) between (2) and the shroud surrounding it. With this configuration, simply changing the gap (6C, 2C) between the long and short impellers and the shroud,
The BPF sound of the long blades can be reduced, and the long and short impellers and the shroud can be easily manufactured.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. In each drawing, common portions are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a side view showing a long and short impeller of a centrifugal compressor according to the present invention. In this figure, (A) shows the first embodiment, (B) shows the second embodiment, and (C) shows the third embodiment. In each figure, the centrifugal compressor of the present invention is
Long blade 1 with a long blade length that extends from the suction side to the discharge side
And a short / short impeller 3 having a short blade 2 provided in the middle of the long blade 1 and extending from the intermediate position to the discharge side. The long / short impeller 3 rotates about the axis Z-Z, sucks air in the axial direction as indicated by an arrow in the figure, centrifugally compresses the long blade 1 and the short blade 2, and compresses compressed air in the radial direction. Discharge.

In the centrifugal compressor of the present invention, a communication passage 6 is provided in the shroud 4 surrounding the outer peripheral portion of the long blade 1 of the inducer section for introducing air or the impeller.
Equipped with.

In FIG. 1 (A), the communication passage 6 of the first embodiment is a veneer-shaped groove 6 A provided on the outer peripheral portion of the long blade 1.
Is. The veil-shaped groove 6A is composed of three notches in this example, and is provided between the leading edge of the long blade 1 and the leading edge of the short blade 2 at an axial interval.

In FIG. 1B, the communication passage 6 of the second embodiment is a plurality of (three in this example) circumferential grooves 6B provided on the inner circumferential surface of the shroud 4, and each circumferential groove is formed. 6B are provided at intervals in the axial direction.

In FIG. 1C, the communication passage 6 of the third embodiment has a gap 6 between the long blade 1 and the shroud 4 surrounding the long blade 1.
It is C. The gap 6C is set larger than the gap 2C between the short blade 2 and the shroud 4 surrounding the short blade 2.

The above-mentioned communication passage 6, that is, the groove 6 in the shape of a vomer tooth.
The size and number of A, the circumferential groove 6B, and the gap 6C alleviate the pressure difference in the corresponding part so as to reduce the BPF sound of the long blades,
In addition, it is preferable to make an experiment or the like so as to minimize the adverse effect of the leakage loss on the fluid performance. In addition, FIG.
The communication passages 6 of (B) and (C) may be used alone or in combination.

[0019]

EXAMPLE FIG. 2 (A) is a blade load distribution diagram of the centrifugal compressor of the present invention. In this figure, the horizontal axis is dimensionless with the meridional length m2 of the shroud shown in FIG. 2 (B). The vertical axis represents the pressure difference between the positive pressure surface side pressure P (P / S) and the negative pressure positive pressure surface side pressure P (S / S) divided by the atmospheric pressure P0.

The solid line in the figure is a conventional blade load distribution chart, and the broken line is a blade load distribution chart according to the first embodiment (FIG. 1A) of the present invention. In the downstream side of the leading edge of the short blade, the blade load distribution maps of the conventional and the present invention are the same.

From this figure, from the leading edge (inlet) of the long blade 1 to the leading edge of the short blade 2, the pressure P side pressure P (P
/ S) and the pressure difference between the negative pressure and the positive pressure side P (S / S) are low as shown by the broken line, and the BPF sound of the long blade shown in FIG. It can be seen that the number of frequency sounds) can be reduced. Further, on the downstream side of the front edge of the short blade 2, since the blade load distribution maps of the conventional and the present invention are the same, it can be seen that the same high compression performance as the conventional can be maintained.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that the present invention can be freely modified without departing from the gist of the present invention.

[0023]

According to the above-described configuration of the present invention, the communication passage 6 is provided along the rotational direction in the shroud 4 surrounding the outer peripheral portion of the long blade 1 of the inducer portion for introducing air or the impeller. Therefore, the positive pressure side and the negative pressure side of the outer peripheral portion of the long blade 1 are communicated with each other through the communication passage 6, the pressure difference between them is reduced, and the pressure difference in the inducer portion is reduced, so that the BP of the long blade
The F sound can be reduced. Further, since the communication passage 6 is provided only in the inducer portion, the centrifugal portion that contributes to compression is less affected, and high compression performance can be maintained.

Therefore, it is possible to reduce the pressure difference between the positive and negative pressure surfaces of the long blades of the inducer portion, reduce the BPF noise due to the long blades, suppress leakage loss, and maintain high fluid performance.

[Brief description of drawings]

FIG. 1 is a side view showing a long and short impeller of a centrifugal compressor according to the present invention.

FIG. 2 is a blade load distribution diagram of the centrifugal compressor of the present invention.

FIG. 3 is a schematic view of a conventional long / short impeller.

FIG. 4 is a blade surface static pressure distribution map of a shroud portion of a conventional long / short impeller.

FIG. 5 is a conventional relationship diagram between noise frequency and sound pressure level.

[Explanation of reference numerals] 1 long blade, 2 short blade, 3 long and short impeller, 4 shroud, 6 communicating passages, 6A vomer-shaped groove, 6B circumferential groove,
6C gap,

Claims (4)

[Claims] 1. A long blade (1) having a long blade length extending from the suction side to the discharge side, and a short blade (2) provided in the middle of the long blade and having a short blade length extending from the intermediate position to the discharge side. In a centrifugal compressor provided with a long and short impeller (3) having an air passage, a communication passage (in a rotational direction) is provided to a shroud (4) surrounding the outer periphery of the long blade (1) of the inducer section for introducing air or the impeller. 6) The centrifugal compressor provided with a long and short impeller characterized by being provided. 2. The communication passages (6) are provided on an outer peripheral portion of the long blade between a front edge of the long blade (1) and a front edge of the short blade (2), and are axially spaced from each other. The centrifugal compressor with long and short impellers according to claim 1, wherein the centrifugal compressor is a groove (6A) in the shape of a tooth. 3. The shroud (4) is provided with the communication passage (6).
The centrifugal compressor with long and short impellers according to claim 1, wherein there are a plurality of circumferential grooves (6B) provided on the inner peripheral surface of the and spaced apart in the axial direction. 4. The communication passage (6) is a gap (6C) between the long blade (1) and a shroud surrounding the long blade (1), and the gap (6C) is formed between the short blade (2) and the shroud surrounding the short blade (2). The centrifugal compressor provided with the long and short impeller according to claim 1, wherein the centrifugal compressor is set to be larger than the gap (2C).