JP2008202415A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor in which surging is effectively suppressed since it has a structure capable of effectively suppressing the reverse flow of a gas which contributes to the peeling of the flow of the gas resulting in the surging. <P>SOLUTION: This centrifugal compressor 1 comprises an impeller rotor 14 having a hub 12 and blades 13 arranged at the outer peripheral part of the hub 12; and a shroud 11 forming a flow passage for the gas 17 sucked from the upstream side and so installed as to surround the impeller rotor 14. The centrifugal compressor 1 comprises an injection structure for injecting a clearance section blowing gas 16 toward the clearance section between the wall surface of the shroud 11 and the blades 13 along the wall surface of the shroud 11 from the upstream side of the blades 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor that compresses gas using centrifugal force. More specifically, the present invention relates to a centrifugal compressor that is used in an exhaust turbine supercharger (turbocharger) of an engine or a compressed air source facility in a general manufacturing factory.

  For example, an exhaust turbine supercharger (turbocharger) formed by coaxially connecting an exhaust turbine and a centrifugal compressor is frequently used in an automobile engine. Further, in various general factories, a centrifugal compressor may be used as a gas compressor for obtaining a compressed air source. When operating such a centrifugal compressor in a low flow rate region where the gas flow rate is low, if the gas pressure ratio is increased, the pressure fluctuation becomes severe at a certain pressure ratio, and the centrifugal compressor vibrates. As a result, driving becomes unstable (this phenomenon is called surging).

  This surging phenomenon will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the structure of a conventional general centrifugal compressor 50. FIG. 2 is a diagram for explaining the relationship between the surging area and the use area of the centrifugal compressor.

  As shown in FIG. 1A, the centrifugal compressor 50 includes an impeller rotor 51, and a shroud 53 that is provided so as to surround the impeller rotor 51 while forming a flow path of the sucked gas. A plurality of blades 52 are provided on the outer periphery of the impeller rotor 51. By rotating the impeller rotor 51 provided with the plurality of blades 52, gas is sucked into the centrifugal compressor 50 from the upstream side in the axial direction of the impeller rotor 51. The sucked gas is sent out in the centrifugal direction while being pressurized by the impeller rotor 51. The pressurized gas is used, for example, as a supercharging gas for an automobile engine, or as a compressed air source in a general manufacturing factory, or widely used in various applications.

  Next, as shown in FIG. 2, when the gas flow rate is gradually decreased from a state where the rotation speed of the impeller rotor 51 is constant and the gas flow rate is large, the pressure ratio gradually increases. On the contrary, the pressure ratio becomes smaller at the flow rate. That is, the pressure ratio has a maximum value. As one of the factors, when the gas flow rate is gradually decreased, the gas pressure at the gas outlet of the blade 52 becomes higher than the pressure at the gas inlet, and eventually from the gap between the blade 52 and the shroud 53. It is conceivable that the gas 54 leaks upstream and the gas is not sufficiently compressed. That is, it is considered that surging is likely to occur if the gas flow rate is reduced below this point where the pressure ratio has a maximum value.

  The surging line shown in FIG. 2 is a line that connects the maximum values of the pressure ratio at each rotation speed of the impeller rotor 51. That is, surging does not occur in the region right of the surging line, while surging occurs in the region left of the surging line. Usually, in order to avoid the use of the centrifugal compressor in the surging area, in FIG. 2, the area on the right side of the surging line is described as “use area”, and the area on the left side of the surging line is described as “surging area”.

  Many techniques have been developed and disclosed to narrow the surging area, in other words, to suppress surging, to avoid the use of centrifugal compressors in the surging area. For example, there is a technique for suppressing surging as disclosed in Patent Documents 1 to 3 below.

  Conventionally, a technology related to a centrifugal compressor in which a circulation channel is provided in a shroud wall that extends forward from an outer peripheral portion of an impeller to form a suction port has been disclosed (for example, see Patent Document 1). The centrifugal compressor communicates the first opening provided at the impeller installation position of the shroud wall, the second opening provided near the minimum diameter of the shroud wall, and the first opening and the second opening. And a circulation channel including the channel, and the second opening is formed in the “radial direction”. This configuration absorbs the gas vortex at the part where gas flow “peeling” (details will be described later) occurs, and statically returns the gas to the upstream inlet, thereby suppressing “peeling”. It says that surging can be suppressed.

  Moreover, the technique regarding the centrifugal compressor provided with the gas blowing part which blows off gas in the outer peripheral part vicinity of a blade | wing is disclosed (for example, refer patent document 2). This centrifugal compressor is provided on the upstream side of the shroud wall that extends from the outer periphery of the inducer portion in the axial direction to form the suction port and is opposed to the blades, and blows out gas in the vicinity of the outer peripheral portion of the blades. A gas outlet is provided. It is said that this configuration can increase the “volume flow rate” of the gas flow in the vicinity of the shroud wall of the blade to adjust the flow direction and suppress surging.

  The present invention also relates to a compressor having a downstream opening that connects a surface of a housing through which an impeller blade passes in the vicinity and a downstream portion of an annular gas flow path (a flow path formed between an inner tubular wall and an outer tubular wall). A technique is disclosed (for example, see Patent Document 3). The compressor extends in an upstream direction away from the impeller wheel and forms an inlet gas suction portion, and extends in an upstream direction in the outer tubular wall and away from the impeller wheel. The inner tubular wall that forms the inducer part of the intake port, the surface of the housing through which the impeller blades pass nearby, and the downstream of the annular gas flow path (the flow path formed between the inner tubular wall and the outer tubular wall) And a downstream opening that connects the two. In addition, a guide vane is provided downstream of the intake port and is configured to induce a leading spiral.

  With this configuration, when the flow rate of air passing through the compressor is small (operating conditions in which surging is a problem), the air passes from the impeller wheel through the downstream opening to the air suction port through the upstream annular gas passage. It is said that surging can be suppressed by the preceding spiral flow induced by the guide vanes after being "reintroduced" and recirculated through the compressor.

JP-A-5-60097 JP 2003-65298 A JP 2004-332733 A

  One of the causes of surging is that the gas leaking from the gap between the blade and the shroud flows backward in the upstream direction and the compression efficiency of the gas is reduced. This phenomenon will be described.

  In FIG. 1A, when the centrifugal compressor 50 is operated in a low flow rate region where the gas flow rate is small, the gas inlet portion of the blade 52 and the gas outlet portion of the blade 52 are increased when the gas pressure ratio is increased. The pressure difference of the gas increases, and the gas pressure at the gas outlet of the blade 52 becomes higher than the pressure at the gas inlet.

  As a result, the flow of the gas 55 sucked into the centrifugal compressor 50 and reaching the vicinity of the gas inlet of the blade 52 is disturbed (flowed toward the axial center of the impeller rotor 51). This phenomenon is commonly referred to as flow “peeling”.

  When this “separation” occurs and the pressure of the gas at the gas outlet of the blade 52 becomes higher than the pressure of the gas inlet, a part of the gas in the gap between the blade 52 and the shroud 53 moves upstream. It becomes the flow of the gas 54 which flows backward. In other words, gas leaks upstream from the gap between the blade 52 and the shroud 53 (see FIGS. 1A and 1B).

  The flow of the gas 54 that is going to flow backward in the upstream direction increases the separation of the flow of the gas 55, and surging occurs when the separation proceeds over the entire circumference of the gas inlet portion of the blade 52. This reverse gas flow in the upstream direction is one of the factors that cause surging.

  However, in the technique described in Patent Document 1, the gas to be circulated is injected into the gas suction side flow path in a “radial direction” (in other words, in a direction perpendicular to the axial direction of the centrifugal compressor). However, only the gas is circulated on the upstream side of the impeller, and the structure does not intentionally flow the gas between the impeller blades and the shroud wall to suppress the backflow of the gas.

  Patent Document 2 merely discloses a technique in which gas is injected near the outer periphery of a blade (blade). In addition, as an effect, the “volume flow rate” of the gas flow can be increased to adjust the flow direction, which is simply referred to in Patent Document 2.

  However, since the gas sent from the gas jetting part joins with the gas from the upstream side and is supplied to the vicinity of the outer peripheral part of the blade (blade), how efficiently the gas from the gas jetting part has the blade ( It is unclear whether it is injected into the gap between the blade) and the shroud wall. Further, since the gas flowing direction from the gas ejection portion is parallel to the direction in which the gas 55 is peeled in FIG. 1A (the axial center direction of the impeller rotor 51), the gas flowing from the gas ejection portion is the gas It is considered that the separation of 55 is rather promoted, and it cannot be said that the structure effectively suppresses the backflow of gas.

  Further, in Patent Document 3, the surging of the compressor is suppressed, but it cannot be said that the flow of the backflowing gas 54 in FIG. 1 (a) is effectively suppressed, and is caused by the preceding spiral flow in the impeller. It is only a structure that moderately adjusts the degree of swirling flow.

  In addition, a separate intake port guide vane must be provided in order to generate a leading spiral flow. To that end, it is necessary to secure a space for providing the guide vane, and further, the guide vane is provided at the intake port. Therefore, the flow path of the gas passing through the intake port of the guide blade is narrowed (or prevented).

  The present invention has been made in view of the above circumstances, and its purpose is to provide a structure that can more effectively suppress the backflow of gas that promotes gas flow separation, which is one of the causes of surging. As a result, there is provided a centrifugal compressor that can suppress surging more effectively with a simple structure.

Means and effects for solving the problems

  The centrifugal compressor which concerns on this invention is related with the centrifugal compressor which compresses gas using a centrifugal force. And the centrifugal compressor based on this invention has the following some features in order to achieve the said objective. That is, the centrifugal compressor of the present invention includes the following features alone or in combination as appropriate.

  In order to achieve the above object, the first feature of the centrifugal compressor according to the present invention is that an impeller rotor that sucks gas from the upstream side in the axial direction and pumps the gas in the centrifugal direction while increasing the pressure, and is sucked from the upstream side And a shroud provided so as to surround the impeller rotor, and the impeller rotor includes a hub and a plurality of blades provided on an outer peripheral portion of the hub, It is provided with an injection structure for injecting a clearance portion blowing gas along the wall surface of the shroud from the upstream side of the blade toward the clearance portion between the wall surface and the blade.

  According to this configuration, the clearance portion blowing gas is directly injected into the gap between the wall surface and the blade along the shroud wall surface, and most of the injected clearance portion blowing gas flows back through the gap between the shroud wall surface and the blade. It works to suppress the flow of gas. This action makes it difficult for gas flow separation caused by gas backflow to occur. As a result, since the surging line moves to the high pressure ratio side, surging of the gas can be effectively suppressed as compared with the conventional centrifugal compressor with casing treatment.

  Moreover, since the clearance section blowing gas is injected along the wall surface of the shroud, there is almost no disturbance in the flow of gas sucked in the axial direction of the impeller rotor toward the impeller rotor, and the gas suction performance of the centrifugal compressor Will not be affected.

  A second feature of the centrifugal compressor according to the present invention is that the injection structure has a thin plate-like gas injection wall provided along the wall surface, and the gas injection wall is located upstream of the blade. And provided inside the wall surface and over the entire circumference of the wall surface.

  According to this configuration, the clearance portion blowing gas is injected over the entire circumference of the blade suction portion toward the gap between the wall surface of the shroud and the blade. Thereby, the flow of the gas which tries to flow backward through the gap between the wall surface of the shroud and the blade can be suppressed over the entire circumference of the blade suction portion. Further, since the clearance portion blowing gas is injected over the entire circumference of the blade suction portion, the flow of gas sucked in the axial direction of the impeller rotor toward the impeller rotor is made uniform over the entire cross section of the gas flow path. .

  A third feature of the centrifugal compressor according to the present invention is that the width of the gap between the gas injection wall and the wall surface is 1 to 3 times the clearance between the wall surface and the blade. is there.

  According to this configuration, the clearance injected from the wall of the gas injection wall and the shroud is made by setting the width of the gap between the gas injection wall and the wall of the shroud to be one or more times the width of the gap between the wall of the shroud and the blade. Almost all of the partial blowing gas is injected into the gap between the shroud wall and the blade. Thereby, almost all of the clearance portion blowing gas acts to suppress the flow of gas that attempts to flow backward through the gap between the shroud wall surface and the blade. Therefore, it is possible to effectively suppress the flow of gas that tends to flow backward through the gap between the wall surface of the shroud and the blade, which causes surging.

  In addition, by setting the width of the gap between the gas injection wall and the wall surface of the shroud to be not more than three times the width of the gap between the wall surface of the shroud and the blade, It is possible to sufficiently suppress the flow of gas that attempts to flow backward through the gap.

  The fourth feature of the centrifugal compressor according to the present invention is that the contact surface of the gas injection wall where the gas injection wall comes into contact with the sucked gas is curved toward the wall surface as it approaches the blade. Thus, the gas injection wall is formed thinner as it approaches the blade.

  According to this configuration, since the flow path of the gas sucked in the axial direction of the impeller rotor toward the impeller rotor is formed so as to approach the blade, the flow path of the sucked gas becomes wider as the blade approaches the blade. Secured. Thereby, the gas suction performance of the centrifugal compressor is improved.

  A fifth feature of the centrifugal compressor according to the present invention is that the downstream end of the gas injection wall is provided close to the upstream end of the blade.

  According to this configuration, the clearance portion blowing gas injected from the gas injection wall and the wall surface of the shroud is hardly affected by the flow of the gas sucked in the axial direction of the impeller rotor toward the impeller rotor, and is adjacent to the shroud. It is injected into the gap between the wall surface and the blade. Therefore, almost all of the injected clearance section blowing gas is directly injected into the gap between the shroud wall and the blade, and almost all of the clearance section blowing gas flows through the gap between the shroud wall and the blade. It acts to suppress the flow. Accordingly, it is possible to effectively suppress the flow of gas that tends to flow backward through the gap between the wall surface of the shroud and the blade, which causes surging.

  A sixth feature of the centrifugal compressor according to the present invention is that the clearance portion blowing gas is the gas pressurized by the impeller rotor.

  According to this structure, the gas sucked in the axial direction of the impeller rotor toward the impeller rotor can be circulated and used. Therefore, for example, it is not necessary to provide an attached gas compressor as the clearance portion blowing gas source, and the space can be made compact and the space can be effectively used.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The centrifugal compressor according to the present invention is used in many applications such as a centrifugal compressor used in an engine exhaust turbine supercharger (turbocharger), a centrifugal compressor used as a compressed air source facility in a general manufacturing factory, and the like. It is a centrifugal compressor that can be used.

  First, based on FIG. 3, the centrifugal compressor 1 which concerns on one Embodiment of this invention is demonstrated in detail. FIG. 3 is a schematic diagram showing the structure of the centrifugal compressor 1 according to one embodiment of the present invention.

  As shown in FIG. 3, the centrifugal compressor 1 according to an embodiment of the present invention includes an impeller rotor 14 that sucks a gas 17 from an upstream side in the axial direction and sends the gas 17 in a centrifugal direction while increasing the pressure, and is sucked from the upstream side. And a shroud 11 provided so as to surround the impeller rotor 14 and a center housing 15.

  The impeller rotor 14 includes a hub 12 and a plurality of blades 13 provided on the outer periphery of the hub 12. An injection structure for injecting the clearance portion blowing gas 16 from the upstream side of the blade 13 along the wall surface of the shroud 11 toward the gap between the wall surface and the blade 13 (the gas flow path 18, the chamber 20, the gas injection) Wall 19). In the present embodiment, the clearance blowing gas 16 is injected in parallel with the axial direction of the impeller rotor 14 (or in parallel with the wall surface of the shroud 11) by the injection structure.

  Here, the gas injection wall 19 that forms a part of the injection structure for injecting the clearance portion blowing gas 16 is a thin plate-like wall provided along the wall surface of the shroud 11 and provided upstream of the blade 13. And it is provided inside the wall surface of the shroud 11 and over the entire circumference of the wall surface. The gas injection wall 19 also has an annular shape. It is not always necessary to provide the gas injection wall 19 over the entire circumference of the wall surface of the shroud 11.

  Further, the downstream end of the gas injection wall 19 is provided close to the upstream end of the blade 13. Further, in the present embodiment, the gas injection wall 19 is provided so as to extend in the direction in which the gas 17 flows from the shroud 11 as a part of the shroud 11 so as to add a so-called slit-like gap to the wall surface of the shroud 11. . The gas injection wall 19 may be provided as an independent part instead of being provided as a part of the shroud 11.

  Next, the clearance portion blowing gas 16 is a gas injected along the wall surface of the shroud 11 and toward the gap between the wall surface and the blade 13 as described above. Moreover, in this embodiment, the clearance part blowing gas 16 circulates and uses the gas 17 pressurized by the impeller rotor 14 of the centrifugal compressor 1.

  Next, the gas flow path 18 forming a part of the injection structure is a gas communicating with the chamber 20 from the housing of the centrifugal compressor 1 downstream of the impeller rotor 14 where the gas 17 pressurized by the impeller rotor 14 is present. This is a distribution path, and includes a pipe material, a hole-shaped path provided in the shroud 11, and the like.

  Next, the chamber 20 is an annular gas retention portion (gas retention space) provided in the vicinity of the wall surface of the shroud 11 and around the entire circumference of the shroud 11. Since the clearance portion blowing gas 16 from the gas flow path 18 is injected into the gap between the wall surface of the shroud 11 and the blade 13 via the chamber 20, it is uniform over the entire circumference of the gap between the wall surface of the shroud 11 and the blade 13. This is effective for injecting the clearance portion blowing gas 16. Note that the chamber 20 is not necessarily provided.

  The clearance portion blowing gas 16 flowing through the gas flow path 18 is directly injected into the gap between the wall surface of the shroud 11 and the blade 13 along the wall surface of the shroud 11 via the chamber 20. As a result, most of the injected clearance portion blowing gas 16 acts to suppress the flow 54 of the gas 54 that tends to flow backward through the gap between the wall surface of the shroud 11 and the blade 13. Thereby, it is possible to effectively suppress the flow of the gas 54 that tries to flow backward through the gap between the wall surface of the shroud 11 and the blade 13 that causes surging, and as a result, separation of the gas flow (FIG. 1A). Reference) is less likely to occur, and surging can be more effectively suppressed than in the past.

  Further, since the clearance portion blowing gas 16 is injected over the entire circumference of the blade 13 suction portion toward the gap between the wall surface of the shroud 11 and the blade 13, the gas 54 that tends to flow backward over the entire circumference of the blade 13 suction portion. Can be suppressed.

  Further, since the downstream end portion of the gas injection wall 19 is provided close to the upstream end portion of the blade 13, the clearance portion blowing gas 16 injected from the wall surface of the gas injection wall 19 and the shroud 11 is It is injected into the gap between the wall surface of the shroud 11 and the blade 13 with almost no influence of the flow of the gas 17 sucked by the impeller rotor 14. Thereby, almost all of the clearance portion blowing gas 16 acts to suppress the flow of the gas 54 that attempts to flow backward through the gap between the wall surface of the shroud 11 and the blade 13.

  The injection flow rate of the clearance portion blowing gas 16 is more than twice the flow rate of the main gas 17 in the operation near the surging line (see FIG. 2) where the pressure ratio during operation of the centrifugal compressor 1 has a maximum value. It is preferable that Moreover, it is preferable that the injection amount of the clearance part blowing gas 16 is less than 5% of the total gas flow rate in the entire operation region of the centrifugal compressor 1. Thereby, the fall of the efficiency of the centrifugal compressor 1 can be suppressed.

  Further, since the clearance portion blowing gas 16 is injected along the wall surface of the shroud 11 and over the entire circumference of the blade 13 suction portion, the flow of the gas 17 sucked in the axial direction toward the impeller rotor 14 is disturbed. And there is no influence on the gas suction performance of the centrifugal compressor 1.

  Moreover, since the clearance part blowing gas 16 circulates and uses the gas 17 pressurized by the impeller rotor 14 of the centrifugal compressor 1, for example, an attached gas compressor or the like is separately provided as the clearance part blowing gas source. The centrifugal compressor 1 can be made compact, the installation space for the centrifugal compressor 1 can be reduced, and the installation space can be effectively used. It is not always necessary to circulate and use the gas 17 pressurized by the impeller rotor 14 as the clearance portion blowing gas 16.

  Next, FIG. 4 is an enlarged view of the injection part A of the clearance part blowing gas 16 shown in FIG. In the description based on FIG. 4, the same components as those in FIG. 3 described above are denoted by the same reference numerals and the description thereof is omitted. FIG. 4A is an enlarged view of the injection part A of the clearance part blowing gas 16 according to the centrifugal compressor 1 of the present embodiment, and FIG. 4B is an injection part showing a modification of the gas injection wall 19. FIG.

  As shown in FIG. 4A, the width W2 of the gap between the gas injection wall 19 and the wall surface of the shroud 11 of the centrifugal compressor 1 according to this embodiment is the width W1 of the gap between the wall surface of the shroud 11 and the blade 13. The dimensions are the same. Here, the width W1 of the gap between the wall surface of the shroud 11 and the blade 13 is usually about 0.2 mm to about 3 mm. By setting the width W2 and the width W1 to the same width, the clearance portion blowing gas 16 injected from the wall surface of the gas injection wall 19 and the shroud 11 is injected over the entire width of the gap between the wall surface of the shroud 11 and the blade 13. As a result, almost all of the flow of gas 54 (see FIG. 3) to be reversed can be suppressed.

  The width W2 of the gap between the gas injection wall 19 and the wall surface of the shroud 11 is preferably not less than 1 (equal times) and not more than 3 times the width W1 of the gap between the wall surface of the shroud 11 and the blade 13. By setting the width W2 to be not less than 1 time (equal times) and not more than 3 times the width W1, the clearance portion blowing gas 16 to be injected tries to reversely flow through the gap between the wall surface of the shroud 11 and the blade 13. The flow of the gas 54 can be sufficiently suppressed without leaking. Further, even if the width W2 is set to be larger than the width W1, the effect of suppressing the flow of the gas 54 to flow backward is not further improved, but the path of the gas 17 to be sucked is narrowed. .

  Next, as shown in FIG. 4B, the gas injection wall 21, which is a modification of the gas injection wall 19, has a contact surface of the gas injection wall 21 where the gas injection wall 21 contacts the sucked gas 17. By being formed so as to bend toward the wall surface side of the shroud 11 as the blade 13 is approached, the blade 13 is formed thinner as the blade 13 is approached.

  Accordingly, the flow path of the gas 17 sucked in the axial direction toward the impeller rotor 14 is formed so as to expand as it approaches the blade 13, so that the flow path of the sucked gas 17 becomes wider as the blade 13 is approached. Secured. Therefore, the gas suction performance of the centrifugal compressor is improved.

  Next, FIG. 5 is a diagram showing surging lines of the centrifugal compressor of the present invention and the conventional centrifugal compressor. As described above, the structure of the centrifugal compressor has an injection structure for injecting the clearance portion blowing gas 16 from the upstream side of the blade 13 along the wall surface of the shroud 11 toward the gap between the wall surface and the blade 13. By providing the gas flow, separation of the gas flow is less likely to occur, and as shown in FIG. 5, the surging line can be moved to the high pressure ratio side as compared with the conventional centrifugal compressor. . Thereby, the use area | region at the time of the low flow rate of a centrifugal compressor expands in all the pressure ratios.

  Further, the centrifugal compressor according to the present invention that directly injects gas (clearance portion blowing gas 16) toward the gap between the wall surface of the shroud 11 and the blade 13 is, for example, with a casing treatment described in Patent Document 1. Compared with a centrifugal compressor (a structure in which the gas in the vicinity of the peeling part is circulated and returned to the blade suction part (inlet part)), the amount of gas returned to the upstream side is small, so that the efficiency is not lowered.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

It is a schematic diagram which shows the structure of the conventional general centrifugal compressor. It is a figure for demonstrating the relationship between the surging area | region and use area | region of a centrifugal compressor. It is a schematic diagram which shows the structure of the centrifugal compressor which concerns on one Embodiment of this invention. It is an enlarged view of the injection part A of the clearance part blowing gas shown in FIG. It is a figure which shows the surging line of the centrifugal compressor of this invention, and the conventional centrifugal compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 11 Shroud 12 Hub 13 Blade 14 Impeller rotor 16 Clearance part blowing gas 19, 21 Gas injection wall 18 Supply port end part 20 Chamber

Claims (6)

A centrifugal compressor that compresses gas using centrifugal force,
An impeller rotor that sucks gas from the upstream side in the axial direction and sends it in the centrifugal direction while increasing the pressure;
Forming a flow path for the gas sucked from the upstream side, and a shroud provided so as to surround the impeller rotor,
The impeller rotor has a hub and a plurality of blades provided on the outer peripheral portion of the hub,
A centrifugal compressor comprising an injection structure for injecting a clearance portion blowing gas along the wall surface of the shroud from the upstream side of the blade toward the clearance portion between the wall surface and the blade. . The injection structure has a thin plate-shaped gas injection wall provided along the wall surface,
2. The centrifugal compressor according to claim 1, wherein the gas injection wall is provided on an upstream side of the blade and is provided on an inner side of the wall surface and over the entire circumference of the wall surface.   The centrifugal compressor according to claim 2, wherein a width of a gap between the gas injection wall and the wall surface is not less than 1 times and not more than 3 times a clearance between the wall surface and the blade.   The gas injection wall is formed on the blade by forming a contact surface of the gas injection wall where the gas injection wall comes into contact with the sucked gas so as to bend toward the wall surface as it approaches the blade. The centrifugal compressor according to claim 2 or 3, wherein the centrifugal compressor is formed thinner as it approaches.   The centrifugal compressor according to any one of claims 2 to 4, wherein a downstream end portion of the gas injection wall is provided in proximity to an upstream end portion of the blade. .   The centrifugal compressor according to any one of claims 1 to 5, wherein the clearance portion blowing gas is the gas pressurized by the impeller rotor.

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