JP6920852B2 - Centrifugal compressor impeller and electric centrifugal compressor - Google Patents

Description

The present disclosure relates to an impeller for a centrifugal compressor and an electric centrifugal compressor.

Conventionally, a centrifugal compressor having a rotatable impeller inside a casing is known. The impeller includes a rotating shaft, a hub mounted on the rotating shaft, and a plurality of wings provided on the outer peripheral surface of the hub.

Patent Document 1 describes a centrifugal compressor provided with a through hole penetrating from the back surface of the hub to the front end surface of the hub in order to prevent contact between the impeller and the casing.

Japanese Unexamined Patent Publication No. 2010-1868

By the way, in a centrifugal compressor, the pressure of air is increased by a rotating impeller, and as a result of applying pressure to the outer peripheral surface and the back surface of the hub, an axial thrust load acts on the impeller. In general, the air that applies pressure to the back surface of the hub is the air after boosting, so the average value of the pressure applied to the back surface of the hub is higher than the average value of the pressure applied to the front surface of the hub. Therefore, the thrust load acting on the impeller in the front direction (suction side) in the axial direction tends to be larger than the thrust load in the rear direction (back surface side) in the axial direction.

In this regard, when a rotating device for canceling the thrust load in the axial direction is provided on the opposite side of the centrifugal compressor, such as a centrifugal compressor of an exhaust turbocharger, the impeller moves forward in the axial direction. The balance between the thrust load and the thrust load in the rearward direction in the axial direction (hereinafter referred to as "thrust balance") is less likely to be a problem.

On the other hand, when a rotating device such as an electric centrifugal compressor that cancels the thrust load in the axial direction is not provided, the thrust load in the axial direction always acts in one direction when the centrifugal compressor is operated. Become. Therefore, it is necessary to absorb the load with the thrust bearing, and mechanical loss occurs in the thrust bearing.

At least one embodiment of the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is an impeller for a centrifugal compressor capable of optimizing the thrust balance and an electric motor provided with the impeller. The purpose is to provide a centrifugal compressor.

(1) The impeller for a centrifugal compressor according to at least one embodiment of the present invention includes a rotating shaft, a hub mounted on the rotating shaft, a plurality of blades provided on the outer peripheral surface of the hub, and the hub. A sleeve mounted on the rotating shaft so as to abut on the back surface is provided, the distance between the outer peripheral end of the front end surface of the hub and the rotating axis of the hub is Rf, and the sleeve abuts on the back surface of the hub. Assuming that the distance between the outer peripheral edge of the surface and the rotation axis is Rb, the above Rf <Rb is satisfied.

According to the centrifugal compressor impeller described in (1) above, the portion of the back surface of the hub that receives pressure in the forward direction (suction side) in the axial direction is the rotation axis of the hub as compared with the case where Rf ≧ Rb is satisfied. The area projected on the plane orthogonal to is small. Therefore, it is possible to reduce the forward thrust load acting on the impeller in the axial direction and optimize the thrust balance. As a result, the mechanical loss in the thrust bearing can be reduced.

(2) In some embodiments, in the centrifugal compressor impeller according to (1) above, the area obtained by projecting the outer peripheral surface of the hub onto a plane orthogonal to the rotation axis is Af, and of the back surface of the hub. Assuming that the area of the portion outside the contact surface in the radial direction of the hub projected onto the plane orthogonal to the rotation axis is Ab, 0.8Af <Ab <1.0Af is satisfied.

The larger the area where the back surface of the impeller and the contact surface of the sleeve abut, the smaller the forward thrust load acting on the impeller in the axial direction can be reduced, but the distance between the outer peripheral end of the sleeve and the rotation axis increases. The more the impeller is, the heavier the weight of the impeller. In this respect, by configuring the impeller so as to satisfy 0.8Af <Ab <1.0Af like the impeller for a centrifugal compressor described in (2) above, the weight increase of the impeller is suppressed and the thrust balance is optimized. Can be compatible with.

(3) In some embodiments, the centrifugal compressor impeller according to (1) or (2) is further provided with a seal member held on the outer peripheral surface of the sleeve, and the seal member and the rotation axis are further provided. If the distance from and is Rs, then Rf <Rs is satisfied.

According to the centrifugal compressor impeller described in (3) above, the gap between the outer peripheral surface of the sleeve and the casing is sealed by the sealing member, and the axial forward thrust load acting on the impeller is effectively reduced. be able to.

(4) In some embodiments, in the centrifugal compressor impeller according to any one of (1) to (3) above, the hub is at least one penetrating from the back surface of the hub to the outer peripheral surface of the hub. Includes two through holes.

According to the centrifugal compressor impeller described in (4) above, the air in the gap between the back surface of the hub and the casing is supplied to the flow path between the outer peripheral surface of the hub and the casing through the through hole. The pressure acting on the outer peripheral surface of the hub can be increased while reducing the pressure acting on the back surface of the hub to optimize the thrust balance of the impeller. As a result, the mechanical loss in the thrust bearing can be reduced.

(5) In some embodiments, in the centrifugal compressor impeller according to (4) above, the through hole is such that the opening end of the through hole on the outer peripheral surface side of the hub is the through hole. It extends in a direction inclined in the radial direction with respect to the rotation axis so as to be located outside the opening end on the back surface side of the hub in the radial direction of the hub.

According to the centrifugal compressor impeller described in (5) above, the flow of air through the through hole is along the flow direction of the main flow flowing through the flow path between the outer peripheral surface of the hub and the casing. Therefore, it is possible to suppress an increase in loss due to the merging of the air flow through the through hole and the mainstream.

(6) In some embodiments, in the centrifugal compressor impeller according to (4) or (5) above, the through hole is such that the opening end of the through hole on the outer peripheral surface side of the hub is the penetration. The hole is extended in a direction inclined in the circumferential direction of the hub with respect to the rotation axis so as to be located upstream of the opening end on the back surface side of the hub in the rotation direction of the rotation axis.

According to the centrifugal compressor impeller described in (6) above, the air supplied to the flow path between the outer peripheral surface of the hub and the casing through the through hole has the diameter of the hub along the pressure surface of the blade. Since the air flows smoothly outward in the direction, it is possible to suppress an increase in loss due to the merging of the air flow through the through hole and the mainstream.

(7) In some embodiments, in the centrifugal compressor impeller according to any one of (4) to (6) above, a blade adjacent to the through hole on the upstream side in the rotation direction of the rotation axis. If the distance between the and the through hole is d1, and the distance between the blade adjacent to the through hole on the downstream side in the rotation direction and the through hole is d2, d1 <d2 is satisfied.

According to the centrifugal compressor impeller described in (7) above, the air supplied to the flow path between the outer peripheral surface of the hub and the casing through the through hole has the diameter of the hub along the pressure surface of the blade. Since the air flows smoothly outward in the direction, it is possible to suppress an increase in loss due to the merging of the air flow through the through hole and the mainstream.

(8) The electric centrifugal compressor according to at least one embodiment of the present invention is for driving the centrifugal compressor impeller according to any one of (1) to (7) above and the centrifugal compressor impeller. It is equipped with a motor.

In general, unlike the exhaust turbine type supercharger, the electric centrifugal compressor is not provided with a rotating device that cancels the forward thrust load in the axial direction acting on the impeller, so that the forward thrust load in the axial direction is increased. It tends to be particularly larger than the backward thrust load in the axial direction.

In this regard, by applying the centrifugal compressor impeller according to any one of (1) to (7) above to an electric centrifugal compressor, the forward thrust load acting on the impeller in the axial direction is reduced. The thrust balance can be optimized. Therefore, the mechanical loss in the thrust bearing can be reduced.

According to at least one embodiment of the present invention, there is provided an impeller for a centrifugal compressor capable of optimizing the thrust balance and an electric centrifugal compressor including the impeller.

It is sectional drawing which shows typically a part of the centrifugal compressor 2 (2A) which concerns on one Embodiment. It is sectional drawing which shows typically a part of the centrifugal compressor which concerns on a comparative example. It is sectional drawing which shows typically a part of the centrifugal compressor 2 (2B) which concerns on one Embodiment. It is sectional drawing which shows typically the air flow in a centrifugal compressor 2 (2B). It is sectional drawing which shows typically a part of the centrifugal compressor 2 (2C) which concerns on one Embodiment. It is sectional drawing which shows typically the air flow in a centrifugal compressor 2 (2C). It is an axial view which shows the structural example of the through hole 36 in a centrifugal compressor 2 (2B, 2C). It is an axial view which shows the structural example of the through hole 36 in a centrifugal compressor 2 (2B, 2C). It is an axial view which shows the structural example of the through hole 36 in a centrifugal compressor 2 (2B, 2C). It is a schematic diagram which shows the electric supercharger to which a centrifugal compressor 2 (2A-2C) is applied.

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 embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, and are merely explanatory examples. No.
For example, expressions that represent relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a state of relative displacement with tolerances or angles and distances to the extent that the same function can be obtained.
For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, an expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or chamfering within a range in which the same effect can be obtained. The shape including the part and the like shall also be represented.
On the other hand, the expressions "equipped", "equipped", "equipped", "included", or "have" one component are not exclusive expressions that exclude the existence of other components.

FIG. 1 is a cross-sectional view schematically showing a part of a centrifugal compressor 2 (2A) according to an embodiment.
As shown in FIG. 1, the centrifugal compressor 2 includes an impeller 4 (impeller for a centrifugal compressor), a casing 6 for accommodating the impeller 4, and a casing 20 configured for accommodating the sleeve 18 of the impeller 4. include.

The impeller 4 is attached to the rotating shaft 8 so as to be in contact with the rotating shaft 8, the hub 10 mounted on the rotating shaft 8, the plurality of wings 14 provided on the outer peripheral surface 12 of the hub 10, and the back surface 16 of the hub 10. The attached sleeve 18 and the sleeve 18 are provided. The casing 20 is configured to face the back surface 16 of the hub 10 and surround the sleeve 18.

The front end surface 22 of the hub 10 (the end surface of the hub 10 on the suction side in the axial direction) is formed along a direction orthogonal to the rotation axis O of the hub 10. The outer peripheral surface 12 of the hub 10 has a concave surface shape that is smoothly curved so that the distance from the rotation axis O increases toward the downstream side of the air flow. The back surface 16 of the hub 10 is formed along a direction orthogonal to the rotation axis O and is adjacent to a flat surface portion 17 that abuts on the contact surface 26 of the sleeve 18 and the outside of the flat surface portion 17 in the radial direction of the hub 10. 19 is included, and a flat surface portion 21 formed along the direction orthogonal to the rotation axis O and adjacent to the outside of the recess 19 in the radial direction of the hub 10.

Here, the distance between the outer peripheral end 24 (front end of the outer peripheral surface 12) of the front end surface 22 of the hub 10 and the rotation axis O of the hub 10 is Rf, and the contact surface 26 in contact with the back surface 16 of the hub 10 of the sleeve 18. The impeller 4 is configured to satisfy Rf <Rb, where Rb is the distance between the outer peripheral end 28 and the rotation axis O (outer diameter of the sleeve 18).

Further, the area obtained by projecting the outer peripheral surface 12 of the hub 10 onto a plane orthogonal to the rotation axis O is Af, and the portion 30 of the back surface 16 of the hub 10 outside the contact surface 26 in the radial direction of the hub 10 (in the illustrated embodiment). Assuming that the area obtained by projecting the recess 19 and the flat surface portion 21 onto a plane orthogonal to the rotation axis O is Ab, Ab <Af is satisfied by satisfying Rf <Rb as described above.

According to the above configuration, as compared with the case where Rf ≧ Rb is satisfied (see FIG. 2), the portion 30 of the back surface 16 of the hub 10 that receives pressure forward (suction side) in the axial direction is orthogonal to the rotation axis O. The area Ab projected on can be reduced. Therefore, the forward thrust load acting on the impeller 4 in the axial direction can be reduced to optimize the thrust balance, and the mechanical loss in the thrust bearing (not shown) can be reduced.

In the exemplary embodiment shown in FIG. 1, a piston ring 34 (seal member) made of an annular elastic body is held in an annular groove 32 formed on the outer peripheral surface of the sleeve 18, and the piston ring 34 is attached to the casing 20. The contact between the sleeve 18 and the casing 20 seals the sleeve 18. Here, assuming that the distance between the piston ring 34 and the rotation axis O is Rs, the piston ring 34 is arranged so as to satisfy Rf <Rs in order to reduce the forward thrust load in the axial direction acting on the impeller 4. There is. In another embodiment, the seal member may be held in a groove or the like provided in the casing 20.

In some embodiments, in the centrifugal compressor 2 shown in FIG. 1, the impeller 4 is configured to satisfy 0.8Af <Ab <1.0Af.

The larger the area where the back surface 16 of the impeller 4 and the contact surface 26 of the sleeve 18 come into contact with each other, the more the thrust load acting on the impeller 4 in the axial direction can be reduced. As the distance Rb from the rotation axis O increases, the weight of the impeller 4 increases. In this respect, by configuring the impeller 4 so as to satisfy 0.8Af <Ab <1.0Af as described above, it is possible to suppress the weight increase of the impeller 4 and optimize the thrust balance at the same time.

Next, a modified example of the centrifugal compressor 2 will be described with reference to FIGS. 3 to 9. The centrifugal compressor 2 (2B, 2C) described below has the same basic configuration as the centrifugal compressor 2 (2A) described above, but the specific configuration of the impeller 4 is different. In the following modified examples, the configurations including the same functions as the respective configurations of the centrifugal compressor 2 (2A) are designated by the same reference numerals and the description thereof will be omitted, and the characteristic configurations of the modified examples will be mainly described.

FIG. 3 is a cross-sectional view schematically showing a part of the centrifugal compressor 2 (2B) according to the embodiment. FIG. 4 is a cross-sectional view schematically showing the air flow in the centrifugal compressor 2 (2B). FIG. 5 is a cross-sectional view schematically showing a part of the centrifugal compressor 2 (2C) according to the embodiment. FIG. 6 is a cross-sectional view schematically showing the air flow in the centrifugal compressor 2 (2C).

In some embodiments, the hub 10 includes at least one through hole 36 that penetrates from the back surface 16 of the hub 10 to the outer peripheral surface 12 of the hub 10, as shown, for example, in FIGS. 3 and 5.

According to such a configuration, for example, as shown in FIGS. 4 and 6, air in the gap 35 between the back surface 16 of the hub 10 and the casing 20 passes through the through hole 36 and is between the outer peripheral surface 12 of the hub 10 and the casing 6. Since it is supplied to the flow path 42 of the hub 10, the pressure acting on the outer peripheral surface 12 of the hub 10 can be increased while reducing the pressure acting on the back surface 16 of the hub 10, and the thrust balance of the impeller 4 can be optimized. .. Thereby, the mechanical loss in the thrust bearing (not shown) can be reduced.

In some embodiments, for example, as shown in FIG. 4, the through hole 36 extends in a direction parallel to the rotation axis O. According to such a configuration, it is possible to increase the pressure acting on the outer peripheral surface 12 of the hub 10 while reducing the pressure acting on the back surface 16 of the hub 10 with a simple structure. As a result, the thrust balance of the impeller 4 can be optimized with a simple configuration.

In some embodiments, for example, as shown in FIG. 5, the through hole 36 has an opening end 38 on the outer peripheral surface 12 side of the hub 10 of the through hole 36 on the back surface 16 side of the hub 10 of the through hole 36. It extends in a direction inclined in the radial direction with respect to the rotation axis O so as to be located outside the opening end 40 of the hub 10 in the radial direction.

According to this configuration, for example, as shown in FIG. 6, the air flow Fh through the through hole 36 is in the flow direction of the mainstream Fm flowing through the flow path 42 between the outer peripheral surface 12 of the hub 10 and the casing 6. Since it flows into the flow path 42 along the flow path 42, it is possible to suppress an increase in loss due to the merging of the air flow Fh through the through hole 36 and the mainstream Fm.

In some embodiments, for example, as shown in FIG. 7, in the centrifugal compressor 2 (2B) or the centrifugal compressor 2 (2C), the through hole 36 is located on the outer peripheral surface 12 side of the hub 10 of the through hole 36. The opening end 38 of the through hole 36 is located upstream of the opening end 40 on the back surface 16 side of the hub 10 in the rotation direction of the rotation axis 8 in the circumferential direction of the hub 10 with respect to the rotation axis O. It is formed at an angle.

According to this configuration, the air supplied to the flow path 42 through the through hole 36 smoothly flows outward in the radial direction of the hub 10 along the pressure surface 46 of the blade 14, as shown in FIG. It is possible to suppress an increase in loss due to the merging of the air flow Fh through the through hole 36 and the mainstream Fm.

In some embodiments, for example, as shown in FIG. 9, the distance between the blade 14 adjacent to the through hole 36 on the upstream side in the rotation direction of the rotation shaft 8 and the through hole 36 is d1, and the rotation shaft 8 has a distance of d1. Assuming that the distance between the blade 14 adjacent to the through hole 36 on the downstream side and the through hole 36 in the rotation direction is d2, each through hole 36 is arranged so as to satisfy d1 <d2.

According to this configuration, as shown in FIG. 8, the air supplied to the flow path 42 through the through hole 36 smoothly flows outward along the pressure surface 46 of the blade 14, so that the through hole 36 It is possible to suppress an increase in loss due to the confluence of the air flow Fh and the mainstream f through the air flow.

In one embodiment, as shown in FIG. 10, the centrifugal compressor 2 (2A to 2C) may be an electric centrifugal compressor further including a motor 44 for driving the impeller 4.

In general, unlike the exhaust turbine type supercharger, the electric centrifugal compressor is not provided with a rotating device that cancels the forward thrust load in the axial direction acting on the impeller 4, so that the forward thrust load in the axial direction is applied. , Especially tends to be larger than the backward thrust load in the axial direction.

In this regard, by applying the impeller 4 of the centrifugal compressor 2 (2A to 2C) to the electric centrifugal compressor, the thrust load acting on the impeller 4 in the axial direction is reduced and the thrust balance is optimized. Therefore, it is possible to reduce the mechanical loss in the thrust bearing (not shown).

The present invention is not limited to the above-described embodiment, and includes a modified form of the above-described embodiment and a combination of these embodiments as appropriate.

For example, in some of the above-described embodiments, the cross-sectional shape of the through hole 36 is circular, but the cross-sectional shape of the through hole 36 may be an ellipse, a rectangle, or the like, and is not particularly limited.

Further, for example, the through hole 36 in the embodiment shown in FIGS. 3 to 9 described above may be formed in the impeller 4 which does not satisfy the relationship of Rf <Rb as shown in FIG.

2 Centrifugal compressor 4 Impeller 6, 20 Casing 8 Rotating shaft 10 Hub 12 Outer peripheral surface 14 Wing 16 Back surface 17, 21 Flat surface 18 Sleeve 19 Recess 22 Front end surface 24, 28 Outer peripheral end 26 Contact surface 30 Part 32 Circular groove 34 Piston Ring 35 Gap 36 Through hole 38, 40 Open end 42 Flow path 42 Road 44 Motor 46 Pressure surface 47 Negative pressure surface

Claims (8)

Rotation axis and
The hub mounted on the rotating shaft and
A plurality of wings provided on the outer peripheral surface of the hub, and
A sleeve mounted on the rotating shaft so as to abut on the back surface of the hub,
With
If the distance between the outer peripheral end of the front end surface of the hub and the rotation axis of the hub is Rf, and the distance between the outer peripheral end of the contact surface of the sleeve with the back surface of the hub and the rotation axis is Rb, then Rf < Satisfy Rb
The hub includes at least one through hole that penetrates from the back surface of the hub to the outer peripheral surface of the hub.
The through hole is rotated so that the opening end of the through hole on the outer peripheral surface side of the hub is located outside the opening end of the through hole on the back surface side of the hub in the radial direction of the hub. It extends in the direction inclined in the radial direction with respect to the axis.
Impeller for centrifugal compressor. Rotation axis and
The hub mounted on the rotating shaft and
A plurality of wings provided on the outer peripheral surface of the hub, and
A sleeve mounted on the rotating shaft so as to abut on the back surface of the hub,
With
If the distance between the outer peripheral end of the front end surface of the hub and the rotation axis of the hub is Rf, and the distance between the outer peripheral end of the contact surface of the sleeve with the back surface of the hub and the rotation axis is Rb, then Rf < Satisfy Rb
The hub includes at least one through hole that penetrates from the back surface of the hub to the outer peripheral surface of the hub.
The through hole is such that the opening end of the through hole on the outer peripheral surface side of the hub is located upstream of the opening end of the through hole on the back surface side of the hub in the rotation direction of the rotation axis. It extends in a direction inclined in the circumferential direction of the hub with respect to the rotation axis.
Impeller for centrifugal compressor. The area obtained by projecting the outer peripheral surface of the hub onto a plane orthogonal to the rotation axis is Af, and the portion of the back surface of the hub outside the contact surface in the radial direction of the hub is projected onto a plane orthogonal to the rotation axis. The impeller for a centrifugal compressor according to claim 1 or 2, where 0.8Af <Ab <1.0Af is satisfied, where Ab is the area. Further provided with a sealing member held on the outer peripheral surface of the sleeve,
The impeller for a centrifugal compressor according to any one of claims 1 to 3, wherein the distance between the seal member and the rotation axis is Rs, and Rf <Rs is satisfied. The through hole is rotated so that the opening end of the through hole on the outer peripheral surface side of the hub is located outside the opening end of the through hole on the back surface side of the hub in the radial direction of the hub. The impeller for a centrifugal compressor according to claim 2, which is extended in a direction inclined in the radial direction with respect to the axis line. The through hole is such that the opening end of the through hole on the outer peripheral surface side of the hub is located upstream of the opening end of the through hole on the back surface side of the hub in the rotation direction of the rotation axis. The impeller for a centrifugal compressor according to claim 1, which extends in a direction inclined in the circumferential direction of the hub with respect to the rotation axis. The distance between the blade adjacent to the upstream side of the through hole in the rotation direction of the rotation axis and the opening end of the through hole on the outer peripheral surface side of the hub is d1, with respect to the through hole in the rotation direction. The centrifugal compression according to any one of claims 1 to 6, where d1 <d2 is satisfied, where d2 is the distance between the blade adjacent to the downstream side and the open end of the through hole on the outer peripheral surface side of the hub. Machine impeller. An electric centrifugal compressor comprising the centrifugal compressor impeller according to any one of claims 1 to 7 and a motor for driving the centrifugal compressor impeller.

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