JP2009257177A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor capable of shortening processing time by providing an expanded part inside an air circulation passage in a shroud wall, and inhibiting occurrence of surging. <P>SOLUTION: This centrifugal compressor 10 includes a rotatably supported impeller 12, and a shroud wall 14 extended from a periphery of the impeller 12 to an upstream side and forming a suction port 13. The shroud wall 14 includes a first opening part 21 provided at a section facing the impeller 12, a second opening part 22 provided at an outer circumference of an upstream suction port 13 displaced from an installation position of the impeller 12, and an air circulation passage 20 comprising a communication channel 23 connecting the first opening part 21 with the second opening part 22. The expanded part 23a with a section area expanded is formed in the communication channel 23. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor used for compressing gas as an air source in a supercharger or other general production equipment for supplying pressurized air to an internal combustion engine.

In general, a supercharger that supplies pressurized air to supercharge an internal combustion engine, for example, rotates a turbine using the exhaust of the internal combustion engine and rotates an impeller of a compressor directly connected to the turbine. Thus, air is compressed and supplied to the intake side of the internal combustion engine. The impeller may be driven by a motor.
In the centrifugal compressor used for such a supercharger, when the amount of air flowing through the compressor decreases, the compressor characteristic curve exceeds the surge line and enters the surging region. Therefore, an attempt has been proposed to apply the compressor in a wider range with respect to the operating range of the internal combustion engine by moving the surge line in the compressor characteristic curve to a low flow rate as much as possible.

  FIG. 3 shows a conventional example of a structure for moving such a surging region to the small flow rate side. From the suction port 1 side to the shroud wall 3 from the suction port 1 to the outer peripheral portion of the impeller 2. A throttle portion 4 having a diameter reduced toward the impeller 2 is provided. An annular chamber 5 is provided inside the shroud wall 3 so as to straddle the throttle portion 4. A first opening 6 is formed between the chamber 5 and the impeller 2, and a second opening 7 is formed between the chamber 5 and the suction port 1. The first opening 6, the chamber 5, and the second opening 7 form an air circulation passage (air treatment mechanism).

In the case of the configuration described above, the intake air is contracted by the throttle portion 4, and the suction effect is given to the air circulation passage by the contracted flow effect to make negative pressure. In this way, a part of the air sucked into the impeller 2 during the operation of the compressor is circulated through the air circulation passage, and the flow capacity at which surging occurs can be reduced. Various proposals have been made to move the occurrence of surging to the small flow rate side with such a configuration (for example, Patent Documents 1 and 2).
JP-A-5-60097 JP 2004-27931 A

However, the chamber (air circulation passage) formed in the shroud wall of the conventional centrifugal compressor is a straight having a uniform cross-sectional shape from the inlet 1 direction toward the impeller 2 direction, as is apparent from FIG. Shape.
Further, the chamber 5 formed in the shroud wall must be formed across the throttle portion 4, and when the shroud wall is cast and the first opening 6 is cut using a cutting tool, the shroud wall is formed. Since the distance H from the surface 3 to the chamber 5 is longer than that of the second opening 7, there is a problem that the processing time becomes longer. Further, there has been a problem that the amount of overhang of the cutting tool increases during processing, and cutting may not be possible.

The present invention has been made in view of the above-described circumstances, and provides an enlarged portion inside the air circulation passage in the shroud wall, shortens the distance to the surface of the shroud wall, and shortens the processing time of the opening. It aims at providing the centrifugal compressor which can be performed.
Further, as another object, by providing an expanding portion in the air circulation passage, the flow once reduced in the flow velocity at the expanding portion is throttled toward the second opening portion, and the flow velocity is increased to obtain a rectifying action. It is what.

The centrifugal compressor according to the present invention employs the following means in order to solve the above problems.
The centrifugal compressor of the present invention is a centrifugal compressor having an impeller rotatably supported and a shroud wall extending upstream from the periphery of the impeller to form a suction port, the shroud wall Includes a first opening provided at a portion facing the impeller, a second opening provided on the outer periphery of the suction port upstream from the installation position of the impeller, and the first opening An air circulation path including a communication flow path communicating with the second opening is provided, and the communication flow path has an expanded portion with an expanded cross-sectional area.

  Moreover, the said expansion part is arrange | positioned in the formation position of the said 1st opening part, It is characterized by the above-mentioned.

  Moreover, the said expansion part expanded in the direction which adjoins the said impeller, It is characterized by the above-mentioned.

  Moreover, the said expansion part was formed in the back flow side rather than the throttle part which the said shroud wall diameter-reduces, It is characterized by the above-mentioned.

According to the present invention, the following effects can be obtained.
The generation of surging can be suppressed by increasing the flow rate of air flowing through the air circulation passage from the first opening to the second opening and flowing through the impeller.
Moreover, since the expansion part exists in the communication flow path of the air circulation passage, the time for cutting the first opening can be shortened. Furthermore, in the communication channel, the flow once expanded is throttled in the direction of the outlet (second opening), so that the rectifying action is performed.

  Moreover, since the said expansion part was arrange | positioned in the formation position of the said 1st opening part, when cutting a 1st opening part into the shroud wall manufactured by casting, while being able to shorten a cutting distance, a cutting bite The overhang can be reduced, and the work efficiency can be improved.

  Moreover, since the said expansion part expanded in the direction close | similar to the said impeller, a shroud wall becomes thin and the cutting distance at the time of cutting a 1st opening part in a shroud wall can be shortened.

  Moreover, since the said expansion part was formed in the back flow side rather than the constriction part to which the diameter of the said shroud wall shrinks | reduces, when cutting a 1st opening part in a shroud wall, a cutting distance can be shortened.

Embodiments of a centrifugal compressor according to the present invention will be described below with reference to the drawings.
FIG. 1 is a main part explanatory view showing an embodiment of a centrifugal compressor according to the present invention, and FIG. 2 is a schematic explanatory view of the centrifugal compressor of the present invention.
In the centrifugal compressor 10, an impeller 12 is rotatably supported in a housing 11, and the air sucked from the suction port 13 by the rotation of the impeller 12 is compressed along the shroud wall 14 by centrifugal force. Compressed by being guided to, and supplied to the manifold of the internal combustion engine.

  The impeller 12 has a hub portion 18 and a shroud portion 19 fixed to the rotary shaft 17 with nuts or the like, and the shroud portion 19 has a plurality of blades 12 a disposed on the outer periphery of the hub portion 18. In addition, the shroud wall 14 extends from the periphery of the impeller 12 to the upstream side to form the suction port 13.

The shroud wall 14 has a first opening 21 at a portion facing the blade 12 a of the impeller 12, and a second opening 22 on the outer periphery of the upstream inlet 13 that is out of the installation position of the impeller 12. Is formed. Further, the shroud wall 14 has an air circulation passage 20 including a communication channel 23 communicating the first opening 21 and the second opening 22 therein. The communication passage 23 of the air circulation passage 20 is formed with an expanded portion 23a having an expanded cross-sectional area.
Since the expanded portion 23a expands in the direction in which the shroud wall becomes thinner (the direction closer to the impeller), the distance h to the surface of the shroud wall is reduced. The expanding portion 23 a is formed on the downstream side of the throttle portion 26, and the second opening portion 22 is formed on the upstream side of the throttle portion 26.

The communication flow path 23 of the air circulation passage 20 is formed when the shroud wall 14 is cast, and an expanded portion 23a is also formed at the same time.
The widening portion 23a is slightly narrow at the back end and widens with a gradient in the direction of the suction port 13. Moreover, the communication flow path 23 continuing to the expanding portion 23a is slightly narrowed toward the suction port 13 direction. With this configuration, the air flow that flows in from the first opening portion 21 once decreases in flow velocity at the expanding portion 23a, and then contracts toward the second opening portion 22 to increase the speed. Thus, the flow capacity at which surging occurs can be reduced.

After the housing 11 is cast, the first opening 21 is formed by cutting the entire circumference toward the communication channel 23 formed in advance at the time of casting. Since ribs (not shown) are provided at a plurality of locations, the inner peripheral wall of the shroud wall 14 does not fall off with the processing of the first opening 21.
Therefore, the shorter the cutting distance h, the shorter the machining time and the easier the machining operation. In addition, when the cutting distance h is long, the amount of overhang of the cutting bite becomes large, and processing may be difficult.
In the present embodiment, since the expanded portion 23a that is expanded in the direction in which the shroud wall 14 becomes thinner is formed in the communication flow path 23 of the air circulation passage 20, the cutting distance h is short and the cutting time can be shortened.

  The second opening 22 is formed by fixing the insert ring 24 with a bolt 25 in a recess that is continuous with the communication channel 23 formed in advance when the housing 11 is cast.

In the centrifugal compressor 10 configured as described above, the impeller 12 rotates with the rotation of the rotary shaft 17 directly connected to a turbine (not shown), and air is sucked from the suction port 13.
The sucked air is compressed by the blades 12a through the shroud portion 19, guided to the compression flow path 16, and supplied to the intake pipe side of the engine. Further, during low flow rate operation, the pressure in all regions of the impeller 12 is higher than the pressure in the air circulation passage 20, and a part of the air passing through the blade 12 a passes from the first opening 21 to the air circulation passage 20. The air flow A becomes inward.
On the other hand, the air B that enters from the suction port 13 merges with the air flow A to become an air flow that flows in the direction of the first opening 21. Therefore, a circulation flow indicated by an arrow A is generated in the air circulation passage 20. With this circulating flow A, it is possible not to enter the surging region even in an operation state with a low flow capacity that enters the surging region of the compressor.

  Note that the operation procedure shown in the above-described embodiment, or the shapes and combinations of the constituent members are examples, and can be variously changed based on various conditions and design requirements without departing from the gist of the present invention. is there.

It is principal part explanatory drawing which shows one Embodiment of the centrifugal compressor which concerns on this invention. It is a schematic explanatory drawing of the centrifugal compressor. It is a figure which shows an example of the conventional centrifugal compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Centrifugal compressor 11 ... Housing 12 ... Impeller 12a ... Blade 13 ... Inlet 14 ... Shroud wall 16 ... Compression flow path 17 ... Rotating shaft 19 ... Shroud part 20 ... Air circulation passage 21 ... 1st opening part 22 ... 2nd opening part 23 ... Communication passage 23a ... Expanding part 24 ... Insert ring 26 ... Restriction part

Claims (4)

A centrifugal compressor having an impeller rotatably supported, and a shroud wall extending upstream from the periphery of the impeller to form a suction port,
The shroud wall has a first opening provided at a portion facing the impeller,
An air circulation passage comprising a second opening provided on the outer periphery of the suction port upstream from the position where the impeller is installed, and a communication channel communicating the first opening and the second opening. Have
The centrifugal compressor is characterized in that the air circulation passage has an expanded portion with an expanded cross-sectional area.   The centrifugal compressor according to claim 1, wherein the expanding portion is disposed at a position where the first opening is formed.   The centrifugal compressor according to claim 1, wherein the expansion portion is expanded in a direction close to the impeller.   The centrifugal compressor according to any one of claims 1 to 3, wherein the widened portion is formed on a downstream side of a throttle portion where the diameter of the shroud wall is reduced.

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