JP6404082B2 - Centrifugal compressor and supercharger provided with the same - Google Patents

Description

  The present invention relates to a centrifugal compressor and a supercharger including the same.

  Conventionally, a centrifugal compressor is known as a compressor of a supercharger that raises air supplied to an internal combustion engine used in a ship or the like to an atmospheric pressure or higher (see, for example, Patent Document 1). The centrifugal compressor includes an impeller attached to the rotor shaft, a guide tube that houses the impeller, and a scroll unit into which compressed air discharged from the guide tube flows. The centrifugal compressor compresses air flowing in from the intake port in the axial direction, guides it in a direction inclined from the axial direction, and discharges compressed air from the discharge port.

  In the centrifugal compressor, there is a possibility that the impeller may be broken or dropped due to the centrifugal force due to the high speed rotation. Patent Document 2 protects a tank that contains lubricating oil so that the lubricating oil does not leak out due to the scattered impeller even when all or part of the impeller (compressor impeller) is scattered outward by centrifugal force. A centrifugal compressor provided with a shock absorbing partition wall is disclosed.

JP 2011-117417 A JP 2001-132465 A

In the centrifugal compressor disclosed in Patent Document 2, the tank that stores the lubricating oil is protected when a failure occurs in which all or part of the impeller is broken or dropped due to the centrifugal force due to the high-speed rotation.
However, when all or part of the impeller breaks or falls off and scatters in the radial direction perpendicular to the axial direction of the rotor shaft, all or part of the impeller that is broken or dropped (hereinafter referred to as a breaking member). There is a possibility that the guide tube located outside is damaged and scattered outside. Further, when the breaking member collides with the guide tube, a gap (opening) is generated in a part of the centrifugal compressor, and the breaking member may be scattered outside from the gap.

  A scroll portion is arranged on the outer side of the guide cylinder in the radial direction, but when a breaking member collides with the diffuser portion that guides compressed air from the discharge port to the scroll portion, the vicinity of the diffuser portion expands in the axial direction of the rotor shaft. Deform. When this deformation is large, a crack is generated on the inner peripheral side of the scroll portion disposed in the vicinity of the diffuser portion. When the crack on the inner peripheral side of the scroll portion propagates to the outer peripheral side of the scroll portion, a gap (opening) is generated in a part of the outer periphery of the centrifugal compressor, and the breaking member may be scattered outside from the gap. .

  The present invention has been made in view of such circumstances. When all or part of the impeller is broken or dropped and scattered in a radial direction perpendicular to the axial direction of the rotor shaft, the breaking member is externally provided. An object of the present invention is to provide a centrifugal compressor and a supercharger equipped with the centrifugal compressor capable of suppressing the problem of being scattered.

In order to achieve the above object, the present invention employs the following means.
A centrifugal compressor according to an aspect of the present invention includes an impeller that is attached to a rotor shaft and that compresses fluid flowing from a take-in port and discharges the fluid from the discharge port, and accommodates the impeller and an axis of the rotor shaft A guide tube extending in the direction, and a scroll portion that is disposed on the outer peripheral side in the radial direction perpendicular to the axial direction with respect to the guide tube and forms a spiral chamber into which the compressed fluid discharged from the discharge port flows And a crack propagation preventing portion that is provided on the scroll portion and extends around the axis, the scroll portion including an inner scroll casing disposed on the radially inner peripheral side, and the radial direction An outer scroll casing disposed on the outer peripheral side, the inner scroll casing and the outer scroll casing are integrally formed, and the crack propagation preventing portion is Provided on the inner scroll casing.

  According to the centrifugal compressor according to one aspect of the present invention, when all or a part of the impeller is broken or dropped and scattered in the radial direction perpendicular to the axial direction of the rotor shaft, the compressed fluid is discharged from the discharge port to the scroll portion. When the fracture member collides with a portion (for example, a diffuser portion) that guides, the vicinity of that portion is deformed so as to expand in the axial direction of the rotor shaft. The inner scroll casing of the scroll portion is deformed at the end in the axial direction on the radially inner peripheral side of the scroll portion. When this deformation is large, a crack occurs in the inner scroll casing.

  According to the centrifugal compressor according to one aspect of the present invention, the crack propagation preventing portion extending around the axis is provided in the inner scroll casing. Therefore, propagation of a crack generated in the inner scroll casing to the outer scroll casing formed integrally with the inner scroll casing is suppressed or prevented. Therefore, a gap (opening) is generated in a part of the outer scroll casing disposed on the outer periphery of the centrifugal compressor, and the breakage member is prevented or prevented from scattering from the gap.

In the centrifugal compressor according to one aspect of the present invention, the crack propagation preventing portion may be provided at an end portion in the axial direction of the inner scroll casing.
By doing in this way, it can suppress or prevent that the crack which arose in the inner side scroll casing propagates to the outer side scroll casing in the edge part of the inner side scroll casing supported by a diffuser part.

In the centrifugal compressor according to one aspect of the present invention, the crack propagation preventing portion may be provided on the radially inner peripheral side of the inner scroll casing.
By doing in this way, it can suppress or prevent that the crack which arose on the inner peripheral side of the radial direction of an inner side scroll casing propagates to an outer side scroll casing.

In the centrifugal compressor according to the reference example of the present invention, the crack propagation preventing portion may be a groove portion extending over the entire circumference around the axis.
In this way, when a crack generated on the inner peripheral side in the radial direction of the scroll portion propagates to the crack propagation preventing portion, the crack propagation is such that the crack propagates around the axis along the groove portion. The direction can be changed. Thereby, it is suppressed or prevented that the crack which arose on the inner peripheral side of the radial direction of the scroll part propagates to the outer peripheral side of the radial direction of the scroll part.

In the centrifugal compressor according to one aspect of the present invention, the crack propagation preventing portion may be a protrusion extending around the axis.
By doing so, when a crack generated on the inner peripheral side in the radial direction of the scroll portion propagates to the crack propagation preventing portion, the crack propagation preventing portion is changed depending on the thickness of the protrusion of the crack propagation preventing portion. It is possible to suppress or prevent the crack from getting over to the outer peripheral side in the radial direction.

A turbocharger according to the present invention includes the centrifugal compressor according to any one of the above, and a turbine that rotates around the axis line by exhaust gas discharged from an internal combustion engine and is connected to the rotor shaft.
According to the supercharger according to the present invention, when all or part of the impeller near the center of gravity is broken or dropped and scattered in the radial direction perpendicular to the axial direction of the rotor shaft, all or one of the impellers. It is possible to suppress a problem that the part is scattered outside.

  ADVANTAGE OF THE INVENTION According to this invention, when all or one part of an impeller fractures | ruptures or drops | omits and it scatters in the radial direction orthogonal to the axial direction of a rotor axis | shaft, it can suppress the malfunction that a fracture | rupture member scatters outside. A centrifugal compressor and a supercharger including the centrifugal compressor can be provided.

It is a longitudinal cross-sectional view which shows the supercharger of 1st Embodiment. It is a principal part enlarged view of the centrifugal compressor shown in FIG. It is a principal part enlarged view of the centrifugal compressor of 2nd Embodiment. It is a principal part enlarged view of the centrifugal compressor of 3rd Embodiment.

[First Embodiment]
Hereinafter, the supercharger of 1st Embodiment of this invention is demonstrated with reference to drawings.
The supercharger 100 of the present embodiment is a device that raises the air (gas) supplied to a marine diesel engine (internal combustion engine) used in a marine vessel to an atmospheric pressure or higher and increases the combustion efficiency of the marine diesel engine.
As shown in FIG. 1, the supercharger 100 of this embodiment includes a centrifugal compressor 10, a turbine 20, and a silencer 16. The centrifugal compressor 10 and the turbine 20 are each connected to a rotor shaft 30.

  The turbine 20 includes a turbine housing 21, turbine blades 22, a turbine disk 23, and a turbine nozzle 24. The turbine housing 21 is a hollow cylindrical member disposed around the axis X, and accommodates a turbine blade 22, a turbine disk 23, and a turbine nozzle 24 therein. Exhaust gas discharged from the marine diesel engine flows into the turbine housing 21 along the arrow shown on the right side of FIG.

  The exhaust gas guided to the turbine housing 21 is statically expanded when passing through the turbine nozzle 24 and is guided to the turbine blade 22. The turbine blades 22 are attached to the outer peripheral surface of a substantially disc-shaped turbine disk 23 fixed to the rotor shaft 30 at regular intervals around the axis. The turbine disk 23 is given a rotational force around the axis X by the exhaust gas having undergone static pressure expansion passing through the turbine blades 22. This rotational force becomes power for rotating the rotor shaft 30 and rotates the impeller 11 connected to the rotor shaft 30 about the axis X.

The centrifugal compressor 10 compresses air flowing from the outside of the supercharger 100 and compresses the compressed air into a scavenging trunk (not shown) that communicates with the inside of a cylinder liner (not shown) that constitutes a marine diesel engine (hereinafter, referred to as “cylinder liner”). This is a device that supplies compressed air (compressed fluid).
The centrifugal compressor 10 includes an impeller 11, an air guide tube 12, a diffuser portion 13, a first containment ring 14 (annular member), a second containment ring 15 (cylindrical member), and a silencer 16. The scroll unit 17 is provided.

  As shown in FIG. 2, the impeller 11 is attached to a rotor shaft 30 that extends along the axis X, and rotates about the axis X as the rotor shaft 30 rotates about the axis X. The impeller 11 rotates around the axis X, thereby compressing the air flowing from the intake port 11a and discharging it to the discharge port 11b.

  As shown in FIG. 2, the impeller 11 includes a hub 11c attached to the rotor shaft 30, a blade 11d attached on the outer peripheral surface of the hub 11c, and a flow path 11e. In the impeller 11, a space is formed by the outer peripheral surface of the hub 11c and the inner peripheral surface of the air guide cylinder 12, and a plurality of spaces are formed by the plurality of blades 11d. The impeller 11 applies a centrifugal force in the radial direction to the air flowing in from the intake port 11a along the axis X direction and discharges the air in a direction orthogonal to the axis X direction (radial direction of the impeller 11). The compressed air discharged from the outlet 11b is caused to flow into the diffuser part 13.

  The air guide cylinder 12 accommodates the impeller 11 and extends along the axis X direction of the rotor shaft 30. The air guide cylinder 12 and the impeller 11 form a flow path 11e that guides air flowing from the intake port 11a along the axis X in the radial direction perpendicular to the axis X to the discharge port 11b.

The diffuser unit 13 is a member that guides compressed air (compressed fluid) discharged from the discharge port 11b to the spiral chamber 17c. The diffuser unit 13 includes a diffuser blade 13a and a diffuser disk 13b.
The diffuser blade 13a is an airfoil member disposed on the downstream side of the discharge port 11b of the impeller 11, and forms a flow path that guides compressed air from the discharge port 11b to the vortex chamber 17c.
As shown in FIG. 2, the position in the axis X direction where the diffuser portion 13 is disposed is the gravity center position P <b> 1 of the impeller 11.

The diffuser blades 13 a are provided at a plurality of locations along the circumferential direction of an annular diffuser disk 13 b disposed coaxially with the rotor shaft 30. The diffuser blade 13 a is provided so as to surround a compressed air discharge port 11 b provided on the entire circumference of the impeller 11.
As shown in FIG. 2, the diffuser disk 13 b is connected to the inner peripheral end 17 e of the inner scroll casing 17 a by fastening bolts 44.

  The diffuser unit 13 converts kinetic energy (dynamic pressure) applied to the compressed air into pressure energy (static pressure) by decelerating the flow rate of the compressed air discharged from the discharge port 11b of the impeller 11. The compressed air whose flow velocity has been reduced when passing through the diffuser part 13 flows into a spiral chamber 17 c that communicates with the diffuser part 13. The working fluid that has flowed into the vortex chamber 17c is discharged to a discharge pipe (not shown).

  The first containment ring 14 is an annular member attached to the connection position between the discharge port 11b side of the air guide tube 12 and the inner scroll casing 17a so as to surround the impeller 11 around the axis X. As shown in FIG. 1, the first containment ring 14 is disposed coaxially with the rotor shaft 30. As shown in FIG. 2, the first containment ring 14 is connected to the air guide tube 12 by a fastening bolt 41.

  The second containment ring 15 is a cylindrical member disposed on the outer peripheral side in the radial direction with respect to the air guide cylinder 12 and on the inner peripheral side in the radial direction with respect to the scroll portion 17. As shown in FIG. 1, the second containment ring 15 is arranged coaxially with the rotor shaft 30. As shown in FIG. 2, the second containment ring 15 is connected to the air guide tube 12 by a fastening bolt 42.

  The 1st containment ring 14 and the 2nd containment ring 15 consist of metal members manufactured by rolling. As this metal member, for example, a steel material that is an Fe—C-based alloy containing iron as a main component and containing a small amount of carbon (about 0.2%) is used. Various materials can be used as long as they are steel materials, but it is preferable to use a general structural rolled steel called JIS G 3101 (ASTM A283).

  A metal material obtained by rolling has a composition suitable for the rolling process, and retains ductility leading to fracture after a large plastic deformation. On the other hand, the metal material obtained by casting has a composition suitable for the casting process, and the elongation leading to fracture is smaller than that of the metal material obtained by rolling. As described above, the metal material obtained by rolling has a greater elongation to break than the metal material obtained by casting. That is, the ductility of the metal material by rolling is high. Therefore, the metal material obtained by rolling has a characteristic that the fracture strength against impact is higher than the metal material obtained by casting.

  The silencer 16 is a device that reduces the level of noise generated in the centrifugal compressor 10. As shown in FIG. 1, the silencer 16 forms a flow path that guides air that flows in from a direction orthogonal to the axis X to the suction port of the air guide cylinder 12. A silencer 16a is disposed around the flow path. A part of the noise generated in the centrifugal compressor 10 is absorbed by the silencer 16a, and the noise level is lowered.

  The scroll unit 17 is a device that converts the kinetic energy (dynamic pressure) imparted to the compressed air into pressure energy (static pressure) while the compressed air discharged from the discharge port 11b flows in. The scroll portion 17 is disposed on the outer peripheral side in the radial direction orthogonal to the axis X direction from the air guide tube 12.

As shown in FIGS. 1 and 2, the scroll portion 17 is connected to the inner scroll casing 17a, the outer scroll casing 17b, the outer peripheral end portion 17d (end portion), and the inner peripheral end portion 17e (end portion). A portion 17f (end portion) is provided. Each part which comprises the scroll part 17 is integrally formed by the metal member.
The inner scroll casing 17a and the outer scroll casing 17b form a spiral chamber 17c into which compressed air flows.
As shown in FIG. 2, the scroll portion 17 is connected to the air guide tube 12 by a fastening bolt 43.

An end portion in the axis X direction on the radially inner peripheral side of the scroll portion 17 is an outer peripheral end portion 17d and an inner peripheral end portion 17e of the inner scroll casing 17a and a connecting portion 17f that connects them. A through hole extending in the axial direction is formed in the inner peripheral end 17e. The diffuser disk 13b at a position corresponding to the through hole is formed with a fastening hole in which an internal thread is formed on the inner peripheral surface.
As shown in FIG. 2, a fastening bolt 44 is fastened to the through hole and the fastening hole. In this way, the outer peripheral end 17d and the outer peripheral end 17e are supported by the diffuser disk 13b of the diffuser section 13.

The outer peripheral side end portion 17 d and the inner peripheral side end portion 17 e are annular members that extend around the axis X of the rotor shaft 30. The outer peripheral side end portion 17d and the outer peripheral side end portion 17e are connected by a connecting portion 17f.
A crack propagation preventing groove 17h extending around the axis X is provided on the surface of the annular coupling portion 17f extending around the axis X of the rotor shaft 30 facing the diffuser disk 13b. As shown in FIG. 2, the crack propagation preventing groove 17 h is provided on the radially inner peripheral side of the scroll portion 17.
The crack propagation preventing groove 17h is formed, for example, by forming an annular protrusion centered on the axis X on a mold for casting the scroll portion 17 and using the mold. Therefore, the crack propagation preventing groove 17h has an advantage that it can be formed relatively easily.

The crack propagation preventing groove 17h is a groove that suppresses or prevents the propagation of cracks in the inner scroll casing 17a along the crack propagation direction (the direction indicated by the arrow A in FIG. 2).
The crack propagation preventing groove 17h is preferably provided endlessly around the entire circumference of the rotor shaft 30 around the axis X, but the crack propagation preventing groove 17h may not be provided in a part around the axis X. Good. For example, around the axis line X, a place where the crack propagation preventing groove 17h is provided and a place where the crack propagation preventing groove 17h is not provided may be provided intermittently.

  The crack propagation preventing groove 17h may be provided at any location on the surface of the connecting portion 17f facing the diffuser disk 13b, but it is provided near the outer peripheral end portion 17d, which is the downstream side in the crack propagation direction. preferable. By providing the crack propagation preventing groove 17h in the vicinity of the outer peripheral end portion 17d, it is possible to suppress or prevent a crack generated in the vicinity of the outer peripheral end portion 17d from propagating in the inner scroll casing 17a.

  The air guide cylinder 12 and the scroll portion 17 described above are made of a metal member manufactured by casting in order to form a complicated shape. As this metal member, for example, cast iron which is an Fe—C alloy containing iron as a main component and containing 2% or more of carbon is used. Various materials such as gray cast iron can be used for cast iron, but it is preferable to use ductile cast iron (FCD) in which black smoke in the base structure is spheroidized.

A metal material obtained by casting tends to form a complicated shape by casting, but has brittle characteristics. Therefore, if a crack is generated in the air guide cylinder 12 and the scroll portion 17 due to the collision of the breaking member, the crack may propagate to the entire member.
The crack propagation preventing groove 17h described above suppresses or prevents a crack generated in the inner scroll casing 17a from propagating to the outer scroll casing 17b. The inner scroll casing 17a at the portion where the crack propagation preventing groove 17h is formed has a plate thickness thinner than the periphery of the portion. Therefore, the crack that has reached the crack propagation preventing groove 17h does not propagate in the direction indicated by the arrow A in FIG. 2, but propagates in the direction in which the crack propagation preventing groove 17h extends.

Next, the operation and effect produced by the supercharger 100 of this embodiment will be described.
The compressor included in the supercharger 100 of the present embodiment is a centrifugal compressor. Therefore, the impeller 11 has a larger blade outer diameter on the discharge port 11b side than on the intake port 11a side. Therefore, the center of gravity of the impeller 11 is the position P1 on the discharge port 11b side. The connection position between the discharge port 11 b side of the air guide tube 12 and the scroll portion 17 is the center of gravity of the impeller 11 on the axis X.
When all or part of the impeller breaks or falls off at the position of the center of gravity, the broken or dropped part has a large weight, and the impact force when scattered in the radial direction perpendicular to the axis X direction becomes large. .

  According to the centrifugal compressor 10 of the present embodiment, when all or part of the impeller 11 is broken or dropped and scattered in the radial direction perpendicular to the axis X direction of the rotor shaft 30, the scroll portion 17 is discharged from the discharge port 11b. When the breaking member collides with the diffuser portion that guides the compressed air, the vicinity of the diffuser portion 13 is deformed so as to expand in the axis X direction of the rotor shaft 30. Ends in the axis X direction (outer peripheral end 17d, inner peripheral end 17e) on the inner peripheral side in the radial direction of the scroll part 17 are supported by the diffuser part 13. Therefore, the inner scroll casing 17a of the scroll portion 17 is deformed along with the deformation of the diffuser portion 13. When this deformation is large, a crack is generated in the inner scroll casing 17a (particularly, in the vicinity of the through hole to which the fastening bolt 44 is fastened) disposed in the vicinity of the diffuser portion 13.

According to the centrifugal compressor 10 of this embodiment, the crack propagation preventing groove 17h extending around the axis X is provided in the inner scroll casing 17a. The inner scroll casing 17a at the portion where the crack propagation preventing groove 17h is formed has a plate thickness thinner than the periphery of the portion. Therefore, the crack propagated so that the crack generated in the inner scroll casing 17a does not propagate to the outer scroll casing 17b formed integrally with the inner scroll casing 17a but propagates around the axis along the crack propagation preventing groove 17h. The direction is changed. This suppresses or prevents a crack generated in the inner scroll casing 17a from propagating to the outer scroll casing 17b.
Therefore, a gap (opening) is generated in a part of the outer scroll casing 17b arranged on the outer periphery of the centrifugal compressor 10, and the breaking member is suppressed or prevented from scattering from the gap.

[Second Embodiment]
Hereinafter, a supercharger according to a second embodiment of the present invention will be described with reference to the drawings.
The second embodiment is a modification of the first embodiment, and is the same as the first embodiment except for a case described below, and the description thereof is omitted.
In the supercharger of the first embodiment, the connecting portion 17f of the scroll portion 17 of the centrifugal compressor includes a crack propagation preventing groove 17h. On the other hand, in the turbocharger of the second embodiment, the connecting portion 17f of the scroll portion 17 of the centrifugal compressor is provided with a crack propagation preventing projection 17i.

  As shown in FIG. 3, a crack propagation preventing projection 17i extending around the axis X is provided on the surface of the annular coupling portion 17f extending around the axis X of the rotor shaft 30 on the intake port 11a side. ing. As shown in FIG. 3, the crack propagation preventing projection 17 i is provided on the radially inner peripheral side of the scroll portion 17.

The crack propagation preventing protrusion 17i is a groove that suppresses or prevents propagation in the inner scroll casing 17a along the crack propagation direction (the arrow direction on the outer peripheral surface of the scroll portion 17 in FIG. 3).
The crack propagation preventing projection 17i is preferably provided endlessly around the entire circumference of the rotor shaft 30 around the axis X, but the crack propagation preventing projection 17i may not be provided at a part around the axis X. Good. For example, around the axis line X, a place where the crack propagation preventing projection 17i is provided and a place where the crack propagation preventing protrusion 17i is not provided may be provided intermittently.
The crack propagation preventing projection 17i may be provided at any location on the surface of the connecting portion 17f on the intake port 11a side, but is easier to manufacture if provided near the outer peripheral end portion 17e. Further, by providing the crack propagation preventing projection 17i in the vicinity of the outer peripheral side end portion 17e, the rigidity of the outer peripheral side end portion 17e can be increased so that the outer peripheral side end portion 17e does not easily crack.

According to the centrifugal compressor of this embodiment, the crack propagation preventing protrusion 17 i is provided on the radially inner peripheral side of the scroll portion 17. Therefore, when a crack generated on the inner peripheral side in the radial direction of the scroll portion 17 propagates to the crack propagation preventing projection 17i, the crack propagation preventing projection 17i is overcome by the thickness of the crack propagation preventing projection 17i. It is suppressed or prevented that a crack propagates to the outer peripheral side.
Therefore, a gap (opening) is generated in a part on the outer peripheral side in the radial direction of the scroll portion 17 disposed on the outer periphery of the centrifugal compressor 10, and the breakage member is prevented or prevented from scattering from the gap. .

[Third Embodiment]
Hereinafter, a supercharger according to a third embodiment of the present invention will be described with reference to the drawings.
The third embodiment is a modification of the first embodiment, and is the same as the first embodiment except for a case described below, and the description thereof is omitted.
In the supercharger of the first embodiment, the connecting portion 17f of the scroll portion 17 of the centrifugal compressor includes a crack propagation preventing groove 17h. On the other hand, in the supercharger of the third embodiment, the inner scroll casing 17a of the scroll portion 17 of the centrifugal compressor includes a crack propagation preventing projection 17j.

  As shown in FIG. 4, the outer peripheral surface of the inner scroll casing 17a disposed on the inner peripheral side in the radial direction of the scroll portion 17 (the surface facing the inner peripheral surface forming the spiral chamber 17c) Is provided with a crack propagation preventing projection 17j. As shown in FIG. 4, the crack propagation preventing projection 17 j is provided on the radially inner peripheral side of the scroll portion 17.

The crack propagation preventing projection 17j is a groove that suppresses or prevents propagation in the inner scroll casing 17a along the crack propagation direction (the arrow direction on the outer peripheral surface of the scroll portion 17 in FIG. 4).
The crack propagation preventing projection 17j is preferably provided endlessly around the entire circumference of the rotor shaft 30 around the axis X, but the crack propagation preventing projection 17j may not be provided at a part around the axis X. Good. For example, around the axis line X, a place where the crack propagation preventing projection 17j is provided and a place where the crack propagation preventing protrusion 17j is not provided may be provided intermittently.

  The crack propagation preventing protrusion 17j may be provided at any location on the outer peripheral surface of the inner scroll casing 17a, but is preferably provided downstream in the crack propagation direction. By providing the crack propagation preventing projection 17j on the downstream side in the crack propagation direction, a crack generated on the upstream side in the crack propagation direction on the outer peripheral surface of the inner scroll casing 17a is transferred from the inner scroll casing 17a to the outer scroll casing 17b. Propagation can be suppressed or prevented.

According to the centrifugal compressor of the present embodiment, the crack propagation preventing projection 17j is provided on the outer peripheral surface of the inner scroll casing 17a disposed on the radially inner peripheral side of the scroll portion 17. Therefore, when a crack generated on the inner peripheral side in the radial direction of the scroll portion 17 propagates to the crack propagation preventing projection 17j, the crack propagation preventing projection 17j is overcome by the thickness of the crack propagation preventing projection 17j. It is suppressed or prevented that a crack propagates to the outer peripheral side.
Therefore, a gap (opening) is generated in a part on the outer peripheral side in the radial direction of the scroll portion 17 disposed on the outer periphery of the centrifugal compressor 10, and the breakage member is prevented or prevented from scattering from the gap. .

[Other Embodiments]
In the above description, any one of the crack propagation preventing groove 17h (first embodiment), the crack propagation preventing projection 17i (second embodiment), and the crack propagation preventing projection 17j (third embodiment) is formed in the scroll portion 17. However, other embodiments may be used.
For example, the scroll portion 17 may be provided with all of the crack propagation preventing groove 17h, the crack propagation preventing projection 17i, and the crack propagation preventing projection 17j. Further, for example, any two of these may be provided.

  Further, for example, a protrusion may be provided in place of the groove at the position where the crack propagation preventing groove 17h is provided. Further, a groove may be provided in place of the protrusion at the position where the crack propagation preventing protrusion 17i is provided. Further, a groove may be provided in place of the protrusion at the position where the crack propagation preventing protrusion 17j is provided. Which of the crack propagation preventing groove and the crack propagation preventing projection is provided on the inner peripheral surface of the scroll portion 17 may be appropriately selected in consideration of the material and strength of the scroll portion 17.

  In the above description, the rotor shaft 30 to which the impeller 11 included in the centrifugal compressor 10 is connected is rotated around the axis X by the turbine 20 rotated by the exhaust gas discharged from the marine diesel engine. Other embodiments may be used. For example, the rotor shaft 30 may be rotated by another power source such as a motor connected to the rotor shaft 30.

  In the above description, the position P1 in the axis X direction where the diffuser portion 13 is disposed is a position that coincides with the position of the center of gravity of the impeller 11. In the above description, “match” does not mean that the position P1 and the gravity center position exactly match. Even if the position P1 is arranged in the vicinity of the center of gravity position, it is assumed that the position P1 coincides with the center of gravity position of the impeller 11.

DESCRIPTION OF SYMBOLS 10 Centrifugal compressor 11 Impeller 11a Intake port 11b Discharge port 11e Flow path 12 Air guide cylinder (guide cylinder)
13 Diffuser portion 13a Diffuser blade 13b Diffuser disc 14 First containment ring (annular member)
15 Second containment ring (cylindrical member)
17 Scroll part 17a Inner scroll casing (casing part)
17b Outer scroll casing 17c Vortex chamber 17d Outer peripheral side end (end)
17e Inner peripheral side end (end)
17f Connecting part (end part)
17g Silencer side end 17h Crack propagation prevention groove (crack propagation prevention part)
17i Crack propagation prevention protrusion (crack propagation prevention part)
17j Crack propagation prevention protrusion (crack propagation prevention part)
30 rotor shaft 100 turbocharger

Claims (4)

An impeller that is attached to the rotor shaft and compresses the fluid flowing from the intake port and discharges it from the discharge port;
A guide tube that houses the impeller and extends in the axial direction of the rotor shaft;
A scroll portion which is disposed on the outer peripheral side in the radial direction perpendicular to the axial direction from the guide tube and forms a spiral chamber into which the compressed fluid discharged to the discharge port flows;
A crack propagation preventing portion provided on the scroll portion and extending around the axis,
The scroll portion is an inner scroll casing disposed on the inner peripheral side in the radial direction;
An outer scroll casing disposed on the outer peripheral side in the radial direction,
The inner scroll casing and the outer scroll casing are integrally formed,
The said crack propagation prevention part is a centrifugal compressor which is a protrusion part provided in the said inner side scroll casing, and extending around the said axis line. The crack propagation preventing portion, the centrifugal compressor according to claim 1 provided at the end of the axial direction of the inner scroll casing. The crack propagation preventing portion, the centrifugal compressor according to claim 1 provided on the inner peripheral side in the radial direction of the inner scroll casing. The centrifugal compressor according to any one of claims 1 to 3 ,
A turbocharger comprising: a turbine that rotates around the axis by exhaust gas discharged from an internal combustion engine and is coupled to the rotor shaft.

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