WO2016059866A1

WO2016059866A1 - Labyrinth seal, centrifugal compressor, and supercharger

Info

Publication number: WO2016059866A1
Application number: PCT/JP2015/073128
Authority: WO
Inventors: 平野　雄一郎
Original assignee: 三菱重工業株式会社
Priority date: 2014-10-17
Filing date: 2015-08-18
Publication date: 2016-04-21
Also published as: KR20160147916A; KR101855610B1; CN108026938A; CN108026938B; JP6225092B2; JP2016079904A

Abstract

A labyrinth seal used in a centrifugal compressor is provided with: an impeller along which fluid flows radially; and a stationary member provided on the rear surface side of the impeller. The labyrinth seal is further provided with: a plurality of first protrusions individually circumferentially arranged at a plurality of radial positions on the rear surface of the impeller; and second protrusions circumferentially arranged on the stationary member so that the front end of each of the protrusions is located between adjacent first protrusions. A labyrinth-shaped flow passage including a plurality of minimum clearance sections formed between the first protrusions and the second protrusions is formed radially between the rear surface of the impeller and the stationary member. With respect to the direction of flow of leakage passing through the minimum clearance sections formed between the first protrusions and the second protrusions, the stationary member is located upstream of the minimum clearance sections, and the rear surface of the impeller is located downstream of the minimum clearance sections.

Description

Labyrinth seal, centrifugal compressor and supercharger

The present disclosure relates to a radially extending labyrinth seal of a centrifugal compressor, and a centrifugal compressor and a turbocharger provided with the same.

Generally, a centrifugal compressor of a supercharger is configured to pressurize air flowing into the centrifugal compressor by an impeller. The air pressurized by the centrifugal compressor is led to the engine cylinder and burns, and the high-temperature, high-pressure combustion gas generated by the combustion passes through the turbine of the turbocharger to rotate the shaft connected to the turbine, The centrifugal compressor provided on the other end side of is driven.

In such a centrifugal compressor, a labyrinth seal may be provided between a rotating member including an impeller and a stationary member including a bearing casing. For example, Patent Document 1 describes a labyrinth seal disposed on an impeller back wall of a centrifugal compressor of an exhaust gas turbine supercharger. In this configuration, the leakage flow of the compressed fluid compressed when passing through the impeller via the rear side of the impeller is suppressed.

Usually, the labyrinth seal has a configuration in which narrow areas and fluid expansion areas are alternately provided. Thereby, the amount of fluid leakage from the centrifugal compressor can be suppressed. In addition, since the fluid leaking out of the labyrinth seal is gradually reduced in pressure, the pressure on the back of the impeller can be reduced. In a supercharger equipped with a centrifugal compressor, the fluid force acting on the turbine of the supercharger may exert a thrust from the turbine side to the compressor side, and in this case, it is necessary to reduce the pressure on the back of the impeller It is desirable from the viewpoint of maintaining the thrust balance properly.

JP-A-11-247618

However, in the labyrinth seal as described above, the temperature of the leak flow rises due to fluid friction in the narrow flow passage, and the amount of heat transfer to the impeller increases. The impeller is a component on which high centrifugal stress acts by rotation, and when the temperature is increased by the amount of heat transfer, the possibility of breakage due to creep increases. Therefore, there is a demand for a labyrinth seal having high sealing performance and small heat transfer to the impeller.

In this point, in the labyrinth seal of Patent Document 1, a vortex chamber is provided on the downstream side of the throttling point (narrow area), and a part of the fluid passing through the throttling point is vortexed in the vortex chamber and the remaining fluid is It is supposed to join the Thereby, the heat input to the impeller side is suppressed to a certain extent.

However, since the pressure ratio tends to increase from the viewpoint of improving the efficiency of the centrifugal compressor, it is desired to further suppress the heat input to the impeller side.

In view of the above-described circumstances, at least one embodiment of the present invention provides a labyrinth seal capable of reducing the amount of heat input from the fluid passing through the labyrinth seal to the impeller, and a centrifugal compressor and a turbocharger provided with the same. The purpose is to

(1) The labyrinth seal according to at least one embodiment of the present invention,
A labyrinth seal for use in a centrifugal compressor comprising: an impeller through which fluid flows in a radial direction; and a stationary member provided on the rear side of the impeller,
A plurality of first convex portions respectively provided along the circumferential direction at a plurality of radial positions on the rear surface of the impeller;
And a plurality of second convex portions provided along the circumferential direction on the stationary member such that a tip end portion intrudes between the adjacent first convex portions.
Between the rear surface of the impeller and the stationary member, a labyrinth-like flow path including a plurality of minimum clearances formed between the first projection and the second projection is in the radial direction. Formed along the
The stationary member is positioned upstream of the minimum clearance portion in the flow direction of the leak flow passing through the minimum clearance portion formed between the first convex portion and the second convex portion, and the minimum clearance portion The back side of the impeller is located on the downstream side of the wheel.

As a result of intensive studies by the present inventors, one of the causes of heat input to the impeller in the conventional labyrinth seal is that the fluid having a high flow velocity that has passed through the minimum clearance portion collides with the wall surface of the stationary member and It has been found that when flowing, fluid in the vicinity of the wall surface of the stationary member, which has a high relative temperature as viewed from the impeller side, is transported to the impeller side.
The configuration of the above (1) is conceived based on this finding by the present inventors, and the stationary member is located upstream of the minimum clearance portion in the flow direction of the leakage flow passing through the minimum clearance portion. And, the back of the impeller is positioned downstream of the minimum clearance portion. For this reason, the fluid accelerated when passing through the minimum clearance portion flows along the back of the impeller after colliding with the back of the impeller instead of the stationary member side. Therefore, it is possible to suppress a situation in which the fluid near the wall surface of the stationary member having a high relative total temperature as viewed from the impeller side is accompanied by the fluid having the high flow velocity which has passed through the minimum clearance portion and transported to the impeller side. Therefore, the amount of heat input from the fluid passing through the labyrinth seal to the impeller can be reduced, and the temperature rise of the impeller can be suppressed.

(2) In some embodiments, in the configuration of the above (1), the labyrinth seal seals the leakage flow directed radially inward between the rear surface of the impeller and the stationary member. The minimum clearance portion is formed between the tip of the first convex portion or the radially inner surface of the first convex portion and the second convex portion.
According to the configuration of the above (2), in the labyrinth seal that seals the leak flow directed inward in the radial direction, it is possible to realize the flow of the fluid toward the back surface of the impeller downstream of the minimum clearance portion. Thus, the amount of heat input from the fluid passing through the labyrinth seal to the impeller can be reduced, and the temperature rise of the impeller can be suppressed.

(3) In one embodiment, in the configuration of the above (2), a seal sword tip is provided at the tip of the second convex portion, and the minimum clearance portion is an inner side in the radial direction of the first convex portion. And the seal tip of the second protrusion.
According to the configuration of the above (3), since the seal blade tip is provided on the second convex portion on the stationary member side, the wall surface of the stationary member from the flow of fluid passing through the minimal clearance portion on the downstream side of the minimal clearance portion 2) The wall surface of the convex part is moving away. For this reason, it is possible to effectively suppress a situation in which the flow velocity passing through the minimum clearance portion is accompanied by the high fluid and transferred to the impeller side. Therefore, the amount of heat input from the fluid passing through the labyrinth seal to the impeller can be effectively reduced, and the temperature rise of the impeller can be further suppressed.

(4) In one embodiment, in the configuration of the above (3), the radially inner surface of the first convex portion forms a sealing surface extending along the axial direction of the centrifugal compressor. The second convex portion is provided so as to project from the stationary member toward the rear surface side of the impeller and the outer side in the radial direction.
According to the configuration of the above (4), since the clearance width direction of the minimum clearance portion is along the radial direction, the clearance width of the minimum clearance portion is hardly affected even if the impeller is shifted in the axial direction. Therefore, the seal performance deterioration due to the displacement of the axial direction of the impeller can be suppressed.

(5) In another embodiment, in the configuration of the above (2), a seal sword tip is provided at the tip of the first convex portion, and the minimum clearance portion is the seal sword tip of the first convex portion. And the radial outer surface of the second projection.
According to the configuration of (5), the fluid that has passed through the minimum clearance formed between the seal tip of the first projection on the impeller side and the radially outer surface of the second projection of the stationary member Can be directed to the back of the impeller. Thus, the amount of heat input from the fluid passing through the labyrinth seal to the impeller can be reduced, and the temperature rise of the impeller can be suppressed.

(6) In one embodiment, in the configuration of the above (5), a seal sword tip is provided at the tip of the first convex portion, the minimum clearance portion is the seal sword tip of the first convex portion, It is formed between the radially outer surface of the second convex portion.
According to the configuration of the above (6), since the clearance width direction of the minimum clearance portion is along the radial direction, the clearance width of the minimum clearance portion is hardly influenced even if the impeller is shifted in the axial direction. Therefore, the seal performance deterioration due to the displacement of the axial direction of the impeller can be suppressed.

(7) A centrifugal compressor according to at least one embodiment of the present invention,
An impeller through which fluid flows in a radial direction;
A stationary member provided on the back side of the impeller;
The labyrinth seal according to any one of the above (1) to (6) may be provided between the rear surface of the impeller and the stationary member.
According to the structure of said (7), the heat gain to the impeller from the fluid which passes a labyrinth seal can be reduced, and the temperature rise of an impeller can be suppressed. Therefore, it is possible to suppress a decrease in creep life caused by the high temperature of the impeller, and to realize a high pressure ratio of the centrifugal compressor.

(8) A turbocharger according to at least one embodiment of the present invention,
A compressor configured to include the centrifugal compressor according to the configuration of the above (7), for compressing intake air to an internal combustion engine;
And a turbine configured to be driven by the exhaust gas of an internal combustion engine to drive the compressor.
According to the configuration of the above (8), by reducing the amount of heat input from the fluid passing through the labyrinth seal to the impeller, it is possible to realize high pressure ratio of the centrifugal compressor and improve the performance of the turbocharger. be able to.

According to at least one embodiment of the present invention, the amount of heat input from the fluid passing through the labyrinth seal to the impeller can be reduced, and the temperature rise of the impeller can be suppressed. Therefore, the fall of the creep life resulting from temperature rising of an impeller can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the whole structure of the turbocharger which concerns on one Embodiment. It is a figure which shows the labyrinth seal which concerns on one Embodiment, and is a longitudinal cross-sectional view of the back surface periphery periphery of an impeller. It is the top view which looked the impeller shown to FIG. 2A from the back surface (A direction). It is a figure showing a labyrinth seal concerning one embodiment, and is an outline sectional view of an impeller and a stationary member. It is an expanded sectional view of the labyrinth seal shown in FIG. It is an expanded sectional view of the labyrinth seal concerning other embodiments. It is a figure which shows the flow velocity distribution in a meridional plane among the flow analysis results in a labyrinth seal. It is a figure which shows relative whole temperature distribution among the flow analysis results in a labyrinth seal.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, but are merely illustrative. Absent.

First, with reference to FIG. 1, a supercharger 1 to which a labyrinth seal 10 according to the present embodiment is applied will be described. In the figure, the labyrinth seal 10 is specifically applied to the centrifugal compressor 3 of the supercharger 1. The application destination of the labyrinth seal 10 is not limited to the illustrated centrifugal compressor 3 and may be used for other types of centrifugal compressors.

FIG. 1 is a cross-sectional view (longitudinal cross-sectional view) showing an entire configuration of a turbocharger 1 according to an embodiment, and shows an exhaust turbine turbocharger for marine use as an example.
As shown in the figure, a turbocharger 1 according to an embodiment is an axial flow turbine (hereinafter referred to as a turbine) 2 configured to be driven by exhaust gas from an internal combustion engine (for example, a marine diesel engine). And a centrifugal compressor 3 driven by the turbine 2 and configured to compress intake air supplied to the internal combustion engine.

As a specific configuration example, a bearing stand 4 is provided between the turbine 2 and the centrifugal compressor 3. The turbine casing 21 of the turbine 2, the bearing stand 4, and the compressor casing 31 of the centrifugal compressor 3 are integrally configured by connection means such as a fastening member (for example, a bolt). A thrust bearing 41 and

radial bearings

42 and 43 are accommodated in the bearing stand 4. The rotor 5 is rotatably supported by the thrust bearing 41 and the

radial bearings

42 and 43. The moving blade 24 of the turbine 2 is connected to one end side of the rotor 5, and the impeller 32 of the centrifugal compressor 3 is connected to the other end side.

The turbine 2 is configured to be driven by the exhaust gas of an internal combustion engine (not shown) to drive the centrifugal compressor 3. Specifically, the turbine 2 is provided on the outer peripheral side of the rotor 5 (actually, one end side of the rotor 5), a plurality of moving blades 24 implanted on the outer periphery of the rotor 5, the rotor 5 and the moving blades 24. And a turbine casing 21. An inlet passage 27 through which exhaust gas flows, an axial passage 28 and an outlet passage 29 are sequentially formed in the flow direction of the exhaust gas by the stationary system member including the turbine casing 21. An axial passage 28 is located between the inlet passage 27 and the outlet passage 29 and extends along the rotational axis O of the rotor 5. A moving blade 24 is provided in the axial passage. Further, a turbine nozzle (static blade) 25 is provided on the inlet side of the moving blade 24.
In the turbine 2, exhaust gas from the internal combustion engine is introduced from the inlet passage 27, and the rotor 5 coupled to the moving blades 24 is rotated by the exhaust gas flowing through the axial passage 28. Exhaust gas having passed through the moving blades 24 is discharged through the outlet passage 29.

The centrifugal compressor 3 is configured to compress intake air to an internal combustion engine (not shown), and the rotor 5 (actually, the other end side of the rotor 5) and an impeller 32 provided on the outer periphery of the rotor 5 , And a compressor casing 31 provided on the outer peripheral side of the rotor 5 and the impeller 32. An air inlet 37 and an outlet scroll 38 are formed by a stationary system member including the compressor casing 31. Between the air inlet 37 and the outlet scroll 38, an impeller 32 and a diffuser 36 are disposed in order in the air flow direction (radial direction of the centrifugal compressor 3). The impeller 32 has a disk-like hub 33 fixed to the outer periphery of the rotor 5 and a plurality of vanes 34 fixed to the hub 33 and arranged radially with respect to the hub 33. In the impeller 32, fluid (here, air) flows in the radial direction. In addition, although illustrated about the single stage centrifugal compressor in FIG. 1, a multistage centrifugal compressor may be sufficient.

In the centrifugal compressor 3, the air introduced from the air inlet 37 is pressurized when passing through the impeller 32, the diffuser 36 and the outlet scroll 38. Most of the air compressed by the centrifugal compressor 3 is led to the engine cylinder of the internal combustion engine and performs the work of pushing down the piston in the combustion / expansion stroke. The high-temperature and high-pressure combustion gas generated here is sent to the turbine 2, and the turbine 2 drives the centrifugal compressor 3 coaxially.

A lubricating oil supply passage 44 is formed in the bearing stand 4. One end of the lubricating oil supply passage 44 is connected to a lubricating oil supply unit (for example, an oil tank and an oil pump). The other end of the lubricating oil supply passage 44 is branched into a plurality of branches, and the branched ends are connected to the thrust bearing 41 and the

radial bearings

42 and 43, respectively. The lubricating oil is supplied to the thrust bearing 41 and the

radial bearings

42 and 43 through the lubricating oil supply passage 44, respectively.

In the turbocharger 1 having the configuration as described above, a labyrinth seal 10 is provided between the centrifugal compressor 3 and the bearing stand 4. Specifically, the labyrinth seal 10 is configured to seal between the impeller 32 and the stationary member 46 of the bearing stand 4 facing the impeller 32.
The labyrinth seal 10 mainly prevents air containing lubricating oil in the bearing stand 4 from mixing in with the compressed air of the centrifugal compressor 3. The internal space of the bearing stand 4 may be filled with mist in which the lubricating oil is scattered. In order to prevent this mist from being mixed with the compressed air of the centrifugal compressor 3, part of the high pressure compressed air that has passed through the impeller 32 is caused to flow to the back of the impeller 32 through the labyrinth seal 10. Between the flow path of the compressed air of the centrifugal compressor 3 and the internal space of the bearing stand 4.

Further, in the turbocharger 1, a part of the air discharged from the impeller 32 may go around to the back and leak into the internal space of the bearing stand 4. In this case, the back surface of the impeller 32 has a high pressure, and in the direction of the rotation axis O of the rotor 5, a high thrust force acting on the impeller 32 from the back surface side to the inlet side of the impeller 32 acts. This high thrust force may lead to an increase in the size of the thrust bearing 41 and high friction loss. Therefore, also from the viewpoint of thrust balance, it may be desirable to reduce the pressure on the rear surface of the impeller 32 by the labyrinth seal 10.

Here, the labyrinth seal 10 according to the present embodiment will be described in detail with reference to FIGS. 2A and 2B to 5. FIG. 2A is a view showing the labyrinth seal 10 according to one embodiment, and is a longitudinal cross-sectional view of the periphery of the back surface of the impeller 32. As shown in FIG. FIG. 2B is a plan view of the impeller 32 shown in FIG. 2A as viewed from the rear surface (direction A) 35 side. FIG. 3 is a view showing the labyrinth seal 10 according to one embodiment, and is a schematic cross-sectional view of the impeller 32 and the stationary member 46. As shown in FIG. FIG.4 and FIG.5 is an expanded sectional view of the labyrinth seal 10 in each embodiment.

As shown in FIGS. 2A and 2B to 5, the labyrinth seal 10 according to this embodiment includes an impeller 32 through which fluid (for example, air) flows in a radial direction, and a stationary member provided on the back surface 35 of the impeller 32. And 46 are used in a centrifugal compressor. The labyrinth seal 10 seals between the rear surface 35 of the impeller 32 and the stationary member 46 in the radial direction of the centrifugal compressor.

In some embodiments, the labyrinth seal 10 includes a plurality of first projections 11 provided on the back surface 35 of the impeller 32 and a plurality of second projections 12 provided on the stationary member 46. There is. A labyrinth flow passage 15 is formed between the first convex portion 11 and the second convex portion 12 in the radial direction.
The plurality of first protrusions 11 are provided along the circumferential direction at a plurality of radial positions on the back surface 35 of the impeller 32. For example, as shown in FIG. 2B, a plurality of first convex portions 11 are provided in a ring shape around the rotation axis O of the rotor 5. That is, the plurality of first convex portions 11 are formed concentrically.
The plurality of second convex portions 12 are provided along the circumferential direction on the stationary member 46 such that the tip end portion enters between the adjacent first convex portions 11. For example, the plurality of second convex portions 12 are annularly provided around the rotation axis O of the rotor 5 so as to correspond to the plurality of first convex portions 11 shown in FIG. 2B. That is, the plurality of second convex portions 12 are formed concentrically.

In FIGS. 2A and 2B to 5, one second protrusion 12 is disposed between two adjacent first protrusions 11 in the radial direction, ie, the first protrusion 11 and the first protrusion 11 in the radial direction. The configuration in which the two convex portions 12 are alternately arranged one by one is illustrated. However, at least one second convex portion 12 may be disposed between two adjacent first convex portions 11, and, for example, between two adjacent first convex portions 11 in the radial direction, Two second projections 12 may be disposed.
Further, in FIGS. 2A and 2B to 5, the back surface 35 of the impeller 32 is formed to be orthogonal to the rotation axis O of the rotor 5. In this case, the arrangement direction of the plurality of first protrusions 11 in the radial direction and the arrangement direction of the plurality of second protrusions 12 in the radial direction are both orthogonal to the rotation axis O of the rotor 5 . However, the arrangement direction of the plurality of first convex portions 11 or the plurality of second convex portions 12 may be a direction inclined with respect to a plane orthogonal to the rotation axis O. For example, the plurality of first protrusions 11 or the plurality of second protrusions are arranged along a direction inclined away from the inlet side of the impeller 32 in the axial direction as going from the radially outer side to the inner side It is also good.

In the labyrinth seal 10 having the above-described configuration, as a result of intensive studies by the present inventors for the purpose of reducing the amount of heat input from the fluid passing through the flow path 15 to the impeller 32, the following findings were obtained.
The present inventors conducted flow analysis using the labyrinth seal 50 as a comparative example, and calculated the flow velocity distribution and temperature distribution in the flow path 51 of the labyrinth seal 50.
FIG. 6 is a diagram showing a flow velocity distribution in the meridional plane among the flow analysis results in the labyrinth seal 50. FIG. 7 is a diagram showing the relative total temperature distribution among the flow analysis results in the labyrinth seal 50. As shown in FIG. In the labyrinth seal 50 of the comparative example, as shown in FIGS. 6 and 7, the first convex portion 52 on the back side of the impeller 32 and the second convex portion 53 of the stationary member 46 are alternately arranged in the radial direction. It is arranged. Further, the flow path 51 between the first convex portion 52 and the second convex portion 53 has a minimum clearance between the radial outer surface of the first convex portion 52 and the tip portion of the second convex portion 53. The portion 54 is formed.

As shown in FIG. 6, the flow velocity distribution in the flow passage 51 has the highest flow velocity at the minimum clearance portion 54. On the downstream side of the minimum clearance portion 54, an expansion area 55 formed between adjacent second convex portions 53 and the tip end portion of the first convex portion 52 is located. In general, the fluid having a high flow velocity in the minimum clearance portion 54 decelerates rapidly in the expansion region 55. By repeating this, it is known that the pressure of the fluid gradually decreases. However, as shown in FIG. 6, the fluid having a high flow velocity that has actually passed through the minimum clearance portion 54 collides with the wall surface 56 on the stationary member 46 side, and the flow velocity is partial in the flow path returning to the impeller 32 side. It remains relatively high.
On the other hand, as shown in FIG. 7, in the flow path 51, a region where the relative total temperature is relatively high exists on the stationary member 46 side. The reason is that the fluid in the vicinity of the stationary member 46 has a low flow velocity in the absolute system, and the flow velocity in the rotary coordinate system rotating with the impeller 32 is large. This is because the relative total temperature becomes higher with respect to the fluid on the back side).
Here, returning to FIG. 6, in the labyrinth seal 50 in the comparative example, in the flow path 51, the fluid having a high flow velocity, which has passed through the minimum clearance portion 54, collides with the wall surface 56 on the stationary member 46 side, There is a relatively high flow rate flow path back. Therefore, when the fluid having a high flow velocity that has passed through the minimum clearance portion 54 collides with the wall surface 56 on the stationary member 46 side and flows to this wall surface 56, the vicinity of the wall surface 56 of the stationary member 46 is high when viewed from the impeller 32 It is conceivable that the fluid of the above is transported and transferred to the impeller 32 side. The present inventors have found that this is one of the causes of increased heat input to the impeller 32 in the labyrinth seal 50.

With reference to FIG. 4 and FIG. 5, the labyrinth seal 10 which concerns on this embodiment is conceived based on the above-mentioned knowledge by the present inventors, and is further provided with the following composition.
In some embodiments, a labyrinth comprising a plurality of minimum clearances 16 formed between the first projection 11 and the second projection 12 between the back surface 35 of the impeller 32 and the stationary member 46 A channel 15 is formed along the radial direction.
In addition, in the flow direction of the leak flow passing through the minimum clearance portion 16 formed between the first convex portion 11 and the second convex portion 12, the stationary member 46 is positioned upstream of the minimum clearance portion 16, and the minimum The back surface 35 of the impeller 32 is located downstream of the clearance portion 16.

In the above embodiment, the stationary member 46 is positioned upstream of the minimum clearance 16 in the flow direction of the leakage flow passing through the minimum clearance 16, and the back surface 35 of the impeller 32 downstream of the minimum clearance 16. Is supposed to be located. Therefore, the fluid accelerated when passing through the minimum clearance portion 16 flows along the back surface 35 of the impeller 32 after colliding with the back surface 35 of the impeller 32 instead of the stationary member 46 side. Therefore, the fluid near the wall surface of the stationary member 46 having a high relative total temperature as viewed from the impeller 32 side is prevented from being transferred to the impeller 32 side along with the fluid having a high flow velocity which has passed through the minimum clearance portion 16 it can. Therefore, the amount of heat input from the fluid passing through the labyrinth seal 10 to the impeller 32 can be reduced, and the temperature rise of the impeller 32 can be suppressed.

In one embodiment, the labyrinth seal 10 is configured to seal the radially inward leakage flow between the back surface 35 of the impeller 32 and the stationary member 46, and the minimum clearance 16 is a first protrusion It may be formed between the second protrusion 12 and the radially inner surface of the first end 11 or the first protrusion 11.
According to the above configuration, in the labyrinth seal 10 that seals the leak flow toward the radially inward, the flow of the fluid toward the back surface 35 of the impeller 32 can be realized on the downstream side of the minimum clearance portion 16. Thereby, the amount of heat input from the fluid passing through the labyrinth seal 10 to the impeller 32 can be reduced, and the temperature rise of the impeller 32 can be suppressed.

Specifically, as shown in FIG. 4 and FIG. 5, when the fluid flows from the radially outer side to the inner side in the flow passage 15, the radially inner surface of the first convex portion 11 or this surface side The minimum clearance portion 16 is formed by the tip (sword tip) of the second projection 12 and the radially outer surface of the second convex portion 12 or the tip (sword tip) on the surface side. When the fluid flows from the radially outer side to the inner side, the fluid flowing along the radially inner surface of the first protrusion 11 or the radially outer surface of the second protrusion 12 is the stationary member 46. It flows from the side toward the impeller 32 side. Therefore, by providing the minimum clearance portion 16 on the flow path flowing from the stationary member 46 toward the impeller 32, the fluid in the vicinity of the wall of the stationary member 46 having a high relative temperature as viewed from the impeller 32 is the minimum clearance. It is possible to suppress a situation in which the fluid with high flow velocity flowed through the portion 16 is transferred to the impeller 32 side.
The labyrinth seal 10 may be configured to allow the fluid to flow radially inward from the inside in the flow path 15. In that case, the surface on the outer side in the radial direction of the first convex portion 11 or the tip on the surface side (sword tip) and the surface on the inner side in the radial direction of the second protrusion 12 or the tip on the surface side (sword tip) A minimum clearance 16 is formed.

Next, specific configurations of the embodiments shown in FIGS. 4 and 5 will be described.
As shown in FIG. 4, in one embodiment, a seal tip 12 a is provided at the tip of the second convex portion 12 of the labyrinth seal 10. Further, the minimum clearance portion 16 is formed between the radial inner surface of the first convex portion 11 and the seal tip 12 a of the second convex portion 12.
As a specific configuration example, the radially inner surface of the first convex portion 11 is formed along the axial direction. Further, the radially outer surface of the first convex portion 11 is formed to be inclined with respect to the axial direction. At that time, the radially outer surface of the first convex portion 11 may be inclined in a direction away from the inlet side of the impeller 32 in the axial direction as it goes from the radially outer side to the inner side. The width of the first convex portion 11 in the radial direction is larger at the end on the stationary member 46 side than the base on the rear surface 35 side of the impeller 32. In addition, the first convex portion 11 may be rounded at corner portions in the radial direction, or the corner portions may be chamfered in a tapered shape. Thereby, when it forms with materials, such as an aluminum alloy, from a viewpoint of weight reduction, durability can be improved.
On the other hand, in the second convex portion 12, both the radially inner surface and the outer surface are formed to be inclined with respect to the axial direction, and these surfaces are parallel to each other. At this time, the radially inner surface and the outer surface of the second convex portion 12 may be inclined in a direction away from the inlet side of the impeller 32 in the axial direction as it goes from the radially outer side to the inner side. Moreover, R may be attached to the corner | angular part in radial direction as for the 2nd convex part 12, a corner may be chamfered by taper shape.

According to the above configuration, since the seal tip 12a is provided on the second convex portion 12 on the stationary member 46 side, the wall surface of the stationary member 46 from the flow of fluid passing through the minimal clearance portion 16 on the downstream side of the minimal clearance portion 16 (The wall surface of the second convex portion 12) is far away. For this reason, it is possible to effectively suppress a situation in which the flow velocity passing through the minimum clearance portion 16 is accompanied by the high fluid and transferred to the impeller 32 side. Therefore, the amount of heat input from the fluid passing through the labyrinth seal 10 to the impeller 32 can be effectively reduced, and the temperature rise of the impeller 32 can be further suppressed.

In this case, the radially inner surface of the first convex portion 11 forms a seal surface extending along the axial direction of the centrifugal compressor (for example, the direction of the rotation axis O shown in FIG. 1). In addition, the second convex portion 12 is provided so as to protrude from the stationary member 46 toward the rear surface 35 side of the impeller 32 and the outer side in the radial direction.
According to the above configuration, since the clearance width direction of the minimum clearance portion 16 is in the radial direction, the clearance width of the minimum clearance portion 16 is not easily affected even if the impeller 32 is shifted in the axial direction. Therefore, the seal performance deterioration due to the displacement of the axial direction of the impeller 32 can be suppressed.

As shown in FIG. 7, in another embodiment, a seal point 11 a is provided at the tip of the first convex portion 11 of the labyrinth seal 10. Further, the minimum clearance portion 16 is formed between the seal tip 11 a of the first convex portion 11 and the outer surface of the second convex portion 12 in the radial direction.
As a specific configuration example, the radially inner surface of the first protrusion 11 and the radially outer surface of the first protrusion 11 are formed to be inclined with respect to the axial direction. At that time, the radially inner surface of the first convex portion 11 and the radially outer surface of the first convex portion 11 are in the axial direction on the inlet side of the impeller 32 as they go from the radially outer side to the inner side. It may be inclined in the direction away from. Further, the inclination angles of the radial inner surface of the first convex portion 11 and the radial outer surface of the first convex portion 11 may be different. In this case, the width of the first convex portion 11 in the radial direction is larger at the end on the stationary member 46 side than at the base on the rear surface 35 side of the impeller 32. In addition, the first convex portion 11 may be rounded at corner portions in the radial direction, or the corner portions may be chamfered in a tapered shape. Thereby, when it forms with materials, such as an aluminum alloy, from a viewpoint of weight reduction, durability can be improved.
On the other hand, in the second convex portion 12, both the radially inner surface and the outer surface are formed along the axial direction, and these surfaces are parallel to each other. Moreover, R may be attached to the corner | angular part in radial direction as for the 2nd convex part 12, a corner may be chamfered by taper shape.

According to the above configuration, the minimum clearance portion 16 formed between the seal tip 11a of the first convex portion 11 on the impeller 32 side and the radial outer surface of the second convex portion 12 of the stationary member 46 is passed. The fluid can be directed to the back 35 of the impeller 32. Thereby, the amount of heat input from the fluid passing through the labyrinth seal 10 to the impeller 32 can be reduced, and the temperature rise of the impeller 32 can be suppressed.

In this case, the seal nib 11 a is provided at the tip of the first convex portion 11, and the minimum clearance portion 16 is the outer surface of the seal convex 11 a of the first convex portion 11 and the second convex portion 12 in the radial direction. And between.
According to the above configuration, since the clearance width direction of the minimum clearance portion 16 is in the radial direction, the clearance width of the minimum clearance portion 16 is not easily affected even if the impeller 32 is shifted in the axial direction. Therefore, the seal performance deterioration due to the displacement of the axial direction of the impeller 32 can be suppressed.

As described above, according to the labyrinth seal 10 according to at least one embodiment of the present invention, the amount of heat input to the impeller 32 from the fluid passing through the labyrinth seal 10 is reduced, and the temperature rise of the impeller 32 is suppressed. Can. Therefore, the fall of the creep life resulting from high temperature formation of impeller 32 can be controlled.
Further, according to the centrifugal compressor according to at least one embodiment of the present invention, the amount of heat input from the fluid passing through the labyrinth seal 10 to the impeller 32 can be reduced, and the temperature rise of the impeller 32 can be suppressed. Therefore, it is possible to suppress a decrease in creep life caused by the high temperature of the impeller 32, and to realize a high pressure ratio of the centrifugal compressor.
Furthermore, according to the supercharger 1 according to at least one embodiment of the present invention, the increase in pressure ratio of the centrifugal compressor is realized by reducing the amount of heat input from the fluid passing through the labyrinth seal 10 to the impeller 32. As a result, the performance of the turbocharger 1 can be improved.

The present invention is not limited to the above-described embodiments, and includes the embodiments in which the above-described embodiments are modified, and the embodiments in which these embodiments are appropriately combined.
Although the case where the labyrinth seal 10 was applied to the centrifugal compressor 3 in the supercharger 1 was demonstrated as an example in the said embodiment, the application destination of the labyrinth seal 10 is limited to the centrifugal compressor 3 of a supercharger. Instead, it may be used for other centrifugal compressors.
Moreover, although the supercharger 1 was demonstrated as an application destination of a centrifugal compressor as an example in the said embodiment, the application destination of the centrifugal compressor which concerns on this embodiment is not limited to this.

For example, relative or absolute arrangements such as “radial”, “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” The expression is not only to express such an arrangement strictly, but also to indicate a relative displacement or a relative displacement with an angle or distance that can obtain the same function.
For example, expressions that indicate that things such as "identical", "equal" and "homogeneous" are equal states not only represent strictly equal states, but also have tolerances or differences with which the same function can be obtained. It also represents the existing state.
For example, expressions representing shapes such as quadrilateral shapes and cylindrical shapes not only represent shapes such as rectangular shapes and cylindrical shapes in a geometrically strict sense, but also uneven portions and chamfers within the range where the same effect can be obtained. The shape including a part etc. shall also be expressed.
On the other hand, the expressions “comprising”, “including” or “having” one component are not exclusive expressions excluding the presence of other components.

DESCRIPTION OF SYMBOLS 1 Turbocharger 2 Turbine 3 Centrifugal compressor 4 Bearing base 5 Rotor 10 Labyrinth seal 11 1st

convex part

11a, 12a Sealed sword tip 12 2nd convex part 15 Flow path 16 Minimum clearance part 21 Turbine casing 24 Rotor blade 31 Compressor casing 32 impeller 33 hub 35 back surface 41 thrust bearing 42 radial bearing 43 radial bearing 44 lubricating oil supply passage 46 stationary member 50 labyrinth seal 51 flow path 52 first convex portion 53 second convex portion 54 minimum clearance portion 55 expansion area 56 wall surface O Axis of rotation

Claims

A labyrinth seal for use in a centrifugal compressor comprising: an impeller; and a stationary member provided on the back side of the impeller,
A plurality of first convex portions respectively provided along a circumferential direction on a back surface of the impeller;
And a plurality of second convex portions provided along the circumferential direction on the stationary member such that a tip end portion intrudes between the adjacent first convex portions.
A labyrinth-like flow path including a plurality of minimum clearances formed between the first projection and the second projection is formed between the rear surface of the impeller and the stationary member. ,
The stationary member is positioned on the upstream side of the minimum clearance portion in the flow direction of the flow passing through the minimum clearance portion formed between the first convex portion and the second convex portion. A labyrinth seal characterized in that the rear face of the impeller is located downstream.
The labyrinth seal is configured to seal the flow radially inward between the back surface of the impeller and the stationary member;
The minimum clearance portion is formed between the tip of the first convex portion and the second convex portion, or between the first convex portion and the tip of the second convex portion. The labyrinth seal according to Item 1.
A seal tip is provided at the tip of the second convex portion,
The labyrinth seal according to claim 2, wherein the minimum clearance portion is formed between the first convex portion and the seal tip of the second convex portion.
The first convex portion forms a sealing surface extending along the axial direction of the centrifugal compressor,
The labyrinth seal according to claim 3, wherein the second convex portion is provided so as to protrude from the stationary member toward the rear side of the impeller and the outer side in the radial direction.
A seal point is provided at the tip of the first convex portion,
The labyrinth seal according to claim 2, wherein the minimum clearance portion is formed between the seal tip of the first convex portion and the second convex portion.
The radially outer surface of the second projection forms a sealing surface extending along the axial direction of the centrifugal compressor,
The labyrinth seal according to claim 5, wherein said 1st convex part is projected and provided from said back of said impeller towards said stationary member side and the inner side of said radial direction.
An impeller through which fluid flows in a radial direction;
A stationary member provided on the back side of the impeller;
A centrifugal compressor comprising: a labyrinth seal according to any one of claims 1 to 6, provided between the rear surface of the impeller and the stationary member.
The centrifugal compressor according to claim 7;
A turbine driven by exhaust gas of an internal combustion engine and configured to drive the centrifugal compressor.