Patent Application
20200132078
The present invention relates to a centrifugal compressor and a seal unit.
Priority is claimed on Japanese Patent Application No. 2018-202008, filed on Oct. 26, 2018, the content of which is incorporated herein by reference.
A gas-compressing centrifugal compressor is widely known as a rotary machine. In this centrifugal compressor, a working fluid such as the gas that has flowed in from a suction port is compressed by the rotation of an impeller provided in a housing and discharged from a discharge port.
In such a centrifugal compressor, the working fluid in the gap between a rotating body such as the impeller and a stationary body such as the housing around the rotating body is circumferentially moved so as to follow the surface of the rotating body as the rotating body rotates. A swirling flow (swirl) is generated as a result. This swirling flow may result in vibration excitation in the rotary shaft to which the impeller is fixed.
Japanese Unexamined Patent Application, First Publication No. 2007-177737 discloses a configuration including a communication hole connecting an inlet hole and an outlet hole in order to suppress the impact of a swirling flow. The inlet hole is provided on a radially outer side with respect to an impeller and the outlet hole is provided directly behind a labyrinth seal on the inlet side of the impeller (rotating body). The outlet hole is provided at an angle in the direction opposite to the direction of rotation of the impeller. In such a configuration, a high-pressure working fluid compressed through the impeller is ejected from the outlet hole toward the outer peripheral surface of the impeller in the direction opposite to the direction of rotation of the impeller. A swirling flow generated with the rotation of the impeller is mitigated as a result.
It is necessary to increase the differential pressure between the inlet hole and the outlet hole and the ejection pressure of the working fluid in order to sufficiently obtain the effect of mitigating the swirling flow attributable to the working fluid ejected from the outlet hole. Accordingly, in the configuration disclosed in Japanese Unexamined Patent Application, First Publication No. 2007-177737, the inlet hole is open on a side surface of a flow path formed in a housing on the radially outer side with respect to the impeller such that the high-pressure working fluid compressed through the impeller is taken in. However, the communication hole becomes long when the inlet hole is provided at a position away from the outlet hole, and then a large space becomes necessary for communication hole formation and a reduction in rotary machine size is hindered.
The present invention provides a centrifugal compressor and a seal unit capable of reducing a necessary space while reducing a swirling flow generated with impeller rotation.
A centrifugal compressor according to a first aspect of the present invention includes a rotary shaft which is configured to rotate around an axis, an impeller having a disk fixed to the rotary shaft, a plurality of blades provided on a surface of the disk facing a first side in an axial direction and provided at intervals in a circumferential direction around the axis, and a cover provided on the first side in the axial direction with respect to the disk and the blade and having an outer peripheral surface extending outward in a radial direction toward a second side in the axial direction, a housing covering the rotary shaft and the impeller and having a facing surface formed on the first side in the axial direction with respect to the outer peripheral surface and facing the outer peripheral surface, a seal member forming a clearance with the outer peripheral surface inward of the facing surface in the radial direction in the housing, a plurality of inclined holes formed at intervals in the circumferential direction with respect to the seal member, respectively extending at an angle to a side opposite to a direction of rotation of the rotary shaft toward an inner side in the radial direction, and having an opening portion opening at a position facing the outer peripheral surface, a first fin disposed on the seal member on the second side in the axial direction with respect to the opening portion and protruding from the seal member toward the outer peripheral surface, and a communication flow path portion formed in the housing, having an introduction port opening at a position facing the outer peripheral surface inward in the radial direction of an outer peripheral end on an outermost side in the radial direction in the cover, and communicating with the plurality of inclined holes.
By such a configuration being adopted, part of a working fluid increased in pressure flows into the gap between the outer peripheral surface of the cover and the facing surface of the housing and reaches the second side in the axial direction with respect to the first fin. In contrast, the pressure of the working fluid is low on the first side in the axial direction with respect to the first fin. Accordingly, the pressure of the introduction port of the communication flow path portion becomes higher than the pressure of the opening portion of the inclined hole. Due to the differential pressure between the introduction port and the opening portion generated in this manner, part of the working fluid is ejected from the opening portion through the inclined hole from the communication flow path portion. It is possible to suppress the working fluid between the seal member and the outer peripheral surface of the cover swirling with the rotation of the impeller by the working fluid ejected in the direction opposite to the direction of rotation of the rotary shaft from the opening portions of the plurality of inclined holes. The introduction port of the communication flow path portion is open radially inward of the outer peripheral portion of the cover of the impeller. Accordingly, the introduction port does not have to be provided on the radially outer side of the impeller. Accordingly, no large space is required for the communication flow path portion to be formed and the centrifugal compressor can be reduced in size.
In the centrifugal compressor according to a second aspect of the present invention, the housing may have a housing main body, and a seal holder detachably provided from the housing main body and holding the seal member and the communication flow path portion may be formed in the seal holder.
Since the communication flow path portion is formed in the seal holder as described above, machining for forming the communication flow path portion does not have to be performed on the housing main body. By attaching the seal member and the seal holder where the communication flow path portion is formed to the housing main body, it is possible to realize the centrifugal compressor that is capable of reducing a necessary space while reducing the swirling flow that is generated as the impeller rotates.
In the centrifugal compressor according to a third aspect of the present invention, the communication flow path portion may have a circumferential flow path continuous in the circumferential direction and communicating with the plurality of inclined holes, and a plurality of introduction flow paths connecting the introduction port and the circumferential flow path.
By such a configuration being adopted, part of the working fluid sent radially outward through the impeller can be merged into the circumferential flow path from the introduction flow path and sent into the plurality of inclined holes. Accordingly, the working fluid can be supplied to the plurality of inclined holes under the same conditions regardless of the position in the circumferential direction.
The centrifugal compressor according to a fourth aspect of the present invention may further include a second fin provided on the seal member on the first side in the axial direction with respect to the opening portion and protruding from the seal member toward the outer peripheral surface.
By such a configuration being adopted, direct merging between the working fluid that is ejected from the opening portion of the inclined hole and the pre-compression working fluid is suppressed by the second fin. Accordingly, it is possible to reliably exhibit the effect of suppressing the swirling flow that is attributable to the working fluid ejected from the inclined hole.
A seal unit according to a fifth aspect of the present invention is a seal unit to be mounted onto a centrifugal compressor including a rotary shaft rotating around an axis, an impeller having a disk fixed to the rotary shaft, a plurality of blades provided on a surface of the disk facing a first side in an axial direction and provided at intervals in a circumferential direction around the axis, and a cover provided on the first side in the axial direction with respect to the disk and the blade and having an outer peripheral surface extending outward in a radial direction toward a second side in the axial direction, and a housing covering the rotary shaft and the impeller and having a facing surface formed on the first side in the axial direction with respect to the outer peripheral surface and facing the outer peripheral surface. The seal unit includes an annular seal member allowed to be disposed so as to form a clearance with the outer peripheral surface inward of the facing surface in the radial direction in the housing, a plurality of inclined holes formed at intervals in the circumferential direction with respect to the seal member, respectively extending at an angle in the circumferential direction toward an inner side in the radial direction, and having an opening portion opening on an inner peripheral surface of the seal member, and a first fin disposed on the seal member on the second side in the axial direction with respect to the opening portion and protruding from the seal member. The plurality of inclined hole are communicable with a side inward in the radial direction of an outer peripheral end on an outermost side in the radial direction in the cover.
By attaching the seal unit to the housing main body of the centrifugal compressor, it is possible to realize the centrifugal compressor that is capable of reducing the necessary space while reducing the swirling flow that is generated as the impeller rotates.
According to the present invention, it is possible to reduce the necessary space while reducing the swirling flow generated with impeller rotation.
Hereinafter, a mode for carrying out a centrifugal compressor and a seal unit according to the present invention will be described with reference to the accompanying drawings. The present invention is not limited to these embodiments.
As shown in
The housing 20 has a housing main body 21 and a seal holder 60 (described later). The housing main body 21 forms the outer shell of the geared centrifugal compressor 1.
As shown in
As shown in
The rotary shaft 13 is provided with a pinion gear 15 between the pair of radial bearings 12. A large-diameter gear 16 meshes with the pinion gear 15. The large-diameter gear 16 is driven to rotate by an external drive source. The large-diameter gear 16 is set so as to be larger in outer diameter dimension than the pinion gear 15. Accordingly, the rotational speed of the rotary shaft 13 having the pinion gear 15 exceeds the rotational speed of the large-diameter gear 16.
The pinion gear 15 and the large-diameter gear 16 constitute a speed-increasing transmission unit 11. The speed-increasing transmission unit 11 increases the speed of rotation of the large-diameter gear 16 by the external drive source via the pinion gear 15 and transmits the speed to the rotary shaft 13.
The rotary shaft 13 is provided with a thrust bearing 17 at a position separated from the pinion gear 15 in the axis O direction. The thrust bearing 17 restrains the rotary shaft 13 from moving in the axis O direction.
The impellers 14 are respectively provided in a first end portion 13a and a second end portion 13b of the rotary shaft 13 in the axis O direction. As shown in
The disk 41 has a disk shape and is fixed to the rotary shaft 13. The disk 41 is formed as a concave curved surface and the outer diameter of the disk 41 gradually increases along the axis O direction from a first surface 41a side on a first side of the disk 41 in the axis O direction toward a second surface 41b side on a second side in the axis O direction.
As shown in
As shown in
The cover 43 is provided on the upstream side in the axis O direction with respect to the disk 41 and the plurality of blades 42. The cover 43 has a disk shape and is provided so as to cover the plurality of blades 42. The side of the cover 43 that faces the disk 41 in the axis O direction is formed as a convex surface 43f facing the disk 41 at a certain interval. The cover 43 has a cover outer peripheral surface 43g on the upstream side in the axis O direction. The cover outer peripheral surface 43g extends radially outward and toward the downstream end in the axis O direction from the upstream side in the axis O direction. The cover outer peripheral surface 43g has a tubular outer peripheral surface 43h, which extends in the axis O direction, in the end portion of the cover 43 that is on the upstream side in the axis O direction.
In each impeller 14, an impeller flow path 45 is formed between the disk 41 and the cover 43. The impeller flow path 45 has an inflow port 45i opening along the axis O direction on the radially inner side of the disk 41 on the first surface 41a side and an outflow port 45o opening toward the radially outer side of the impeller 14.
As shown in
As shown in
A seal attachment portion 24 to which the seal holder 60 is attached is formed on the facing surface 22f of the housing main body 21. The seal attachment portion 24 is a groove recessed from the facing surface 22f. The seal attachment portion 24 has a tubular curved surface 24a and an attachment end surface 24b. The tubular curved surface 24a extends from the inner peripheral edge of the facing surface 22f to the upstream side in the axis O direction. The tubular curved surface 24a is curved radially inward so as to form a cylindrical shape. The attachment end surface 24b extends orthogonally to the radially inner side from the end portion of the tubular curved surface 24a that is on the upstream side in the axis O direction. In the attachment end surface 24b, a plurality of female screw holes 24h are formed at intervals in the circumferential direction around the axis O.
The seal holder 60 is provided so as to be detachable with respect to the seal attachment portion 24 of the housing main body 21. The seal holder 60 holds a seal member 50 (described later). The seal holder 60 has an annular shape as a whole. The seal holder 60 has a holder outer peripheral surface 60f, a tip surface 60g, a holder facing surface 60h, a seal holding surface 60i, and a front end facing surface 60j.
The holder outer peripheral surface 60f is a curved surface extending in the axis O direction and facing the radially outer side. The holder outer peripheral surface 60f has a cylindrical shape. The holder outer peripheral surface 60f radially faces the tubular curved surface 24a. The tip surface 60g extends orthogonally to the radially inner side from the end portion of the holder outer peripheral surface 60f that is on the upstream side in the axis O direction. The tip surface 60g is formed so as to face and abut against the attachment end surface 24b in the axis O direction.
The holder facing surface 60h is a surface facing the downstream side in the axis O direction. The holder facing surface 60h is formed so as to be continuous on the radially inner side with respect to the facing surface 22f in a state where the seal holder 60 is attached to the housing main body 21. The holder facing surface 60h faces the cover outer peripheral surface 43g at an interval in the axis O direction radially inward of the facing surface 22f.
The seal holding surface 60i is a surface facing the radially inner side radially inward of the holder facing surface 60h. The seal holding surface 60i is formed so as to face the tubular outer peripheral surface 43h on the upstream side in the axis O direction at an interval in the radial direction. A seal mounting groove 61 into which the seal member 50 is fitted is formed in the seal holding surface 60i. The seal mounting groove 61 is recessed radially outward from the seal holding surface 60i and is continuously formed in the circumferential direction around the axis O.
The front end facing surface 60j is a surface facing the downstream side in the axis O direction radially inward of the holder facing surface 60h. The front end facing surface 60j extends orthogonally to the radially inner side from the end portion of the seal holding surface 60i that is on the upstream side in the axis O direction. The front end facing surface 60j is formed so as to face a cover front end surface 43s, which is formed in the end portion of the cover 43 that is on the upstream side in the axis O direction, at an interval in the axis O direction.
In the seal holder 60, a bolt insertion hole 62 is formed at a plurality of circumferentially spaced locations. Each bolt insertion hole 62 extends in the axis O direction so as to penetrate the seal holder 60 from the holder facing surface 60h to the tip surface 60g. The bolt insertion hole 62 is formed so as to be at the same position as the female screw hole 24h when viewed from the axis O direction in a state where the seal holder 60 is attached to the housing main body 21. In a state where the seal holder 60 is accommodated in the seal attachment portion 24, a bolt 63 is inserted through each bolt insertion hole 62 from the holder facing surface 60h side and fastened to the female screw hole 24h formed in the attachment end surface 24b. As a result, the seal holder 60 is fixed to the housing main body 2L An accommodating recessed portion 62a accommodating a head portion 63a of the bolt 63 is formed in each bolt insertion hole 62.
Further, the seal holder 60 is provided with a communication flow path portion 64. As shown in
The introduction flow path 66 is formed at a plurality of locations spaced in the circumferential direction around the axis O. In the present embodiment, the introduction flow path 66 is provided at, for example, six locations at regular intervals in the circumferential direction. Each introduction flow path 66 is formed so as to be positionally shifted in the circumferential direction so as not to interfere with the bolt insertion hole 62. Each introduction flow path 66 extends to the upstream side in the axis O direction from the holder facing surface 60h. Each introduction flow path 66 is formed in a groove shape recessed radially inward from the holder outer peripheral surface 60f. As shown in
As shown in
The seal member 50 has an annular shape as a whole. The outer peripheral portion of the seal member 50 is fitted in the seal mounting groove 61 of the seal holder 60. As a result, the seal member 50 is provided radially inward of the facing surface 22f and upstream of the facing surface 22f in the axis O direction.
An outer peripheral surface 50f of the seal member 50 is in close contact with the bottom surface of the seal mounting groove 61. An inner peripheral surface 50g of the seal member 50 is provided so as to face the tubular outer peripheral surface 43h of the cover outer peripheral surface 43g with a clearance having a predetermined radial dimension.
As shown in
As shown in
The inclined hole 55 extends at an angle in the circumferential direction so as to be directed to the side opposite to the direction of rotation of the rotary shaft 13 radially inward from the outer peripheral surface 50f side. Preferably, the inclined hole 55 is formed such that an inclination angle Θ with respect to the radial direction about the axis O is, for example, approximately 40° to 50° when the inclined hole 55 is viewed from the axis O direction. The plurality of inclined holes 55 may have the same inclination angle Θ in the circumferential direction or the inclination angles Θ of the plurality of inclined holes 55 may vary with the circumferential positions of the plurality of inclined holes 55.
As shown in
The working fluid is taken into the impeller flow path 45 from the intake flow path 18 through the inflow port 45i by the impeller 14 rotating integrally with the rotary shaft 13. The working fluid is caused to flow from the inflow port 45i of the impeller flow path 45 toward the outflow port 45o by the centrifugal force that is generated by the impeller 14 rotating integrally with the rotary shaft 13. The working fluid is compressed while flowing from the inflow port 45i toward the outflow port 45o. The compressed working fluid flows radially outward from the outflow port 45o and is sent into the exhaust flow path 19. The working fluid is further compressed while swirling around the axis O along the exhaust flow path 19.
The impeller 14, the intake flow path 18, and the exhaust flow path 19 constitute a centrifugal compression unit 30. As a result and as shown in
In the geared centrifugal compressor 1, a fluid compressed by the first-stage impeller 14A of the first-stage centrifugal compression unit 30A subsequently flows into the second-stage centrifugal compression unit 30B. In the process of flowing through the second-stage impeller 14B of the second-stage centrifugal compression unit 30B, the fluid is further compressed and becomes a high-pressure fluid.
Part of the working fluid that has increased in pressure by passing through the impeller flow path 45 and has flowed radially outward from the outflow port 45o flows into the gap between the cover outer peripheral surface 43g and the facing surface 22f at the outer peripheral end 43e of the cover 43 and reaches a downstream side space A3, which is on the downstream side in the axis O direction with respect to the first fin 52.
Between the inner peripheral surface 50g and the tubular outer peripheral surface 43h, the pressure of an upstream side space A1, which is upstream of the second fins 53 and 54 in the axis O direction, is a pressure before the working fluid flows into the impeller flow path 45 and is compressed. In other words, the upstream side space A1 upstream of the second fins 53 and 54 in the axis O direction is lower in pressure than the downstream side space A3 on the downstream side in the axis O direction with respect to the first fin 52. Then, an opening space A2, which is a space partitioned by the first fin 52 and the second fins 53 and 54, becomes higher in pressure than the upstream side space A1 and lower in pressure than the downstream side space A3. The opening space A2 corresponds to the position where the opening portion 57 of the inclined hole 55 is formed. The opening space A2 is on the upstream side in the axis O direction with respect to the first fin 52 and is on the downstream side in the axis O direction with respect to the second fins 53 and 54.
The introduction port 66i is formed so as to face the downstream side space A3. The opening portion 57 is formed so as to face the opening space A2. As a result, the pressure of the introduction port 66i becomes higher than the pressure of the opening portion 57. The differential pressure between the introduction port 66i and the opening portion 57 resulting from the difference in pressure causes the working fluid that has flowed into the gap between the cover outer peripheral surface 43g and the facing surface 22f to flow into the circumferential flow path 67 via a plurality of the introduction flow paths 66. The working fluid that has flowed into the circumferential flow path 67 flows into the plurality of inclined holes 55. The working fluid that has passed through the plurality of inclined holes 55 from the communication flow path portion 64 in this manner is ejected from the opening portion 57 to the opening space A2. The working fluid ejected from the opening portion 57 through the plurality of inclined holes 55 generates a flow in the direction opposite to the direction of rotation of the rotary shaft 13. Canceled as a result is the swirling flow that flows in the direction of rotation of the rotary shaft 13 with the rotation of the impeller 14 between the tip of the first fin 52 and the tubular outer peripheral surface 43h or between the tips of the second fins 53 and 54 and the tubular outer peripheral surface 43h. As a result, swirling flow generation is suppressed and excitation of the rotary shaft 13 is suppressed.
Further, the introduction port 66i is open at a position facing the cover outer peripheral surface 43g radially inward of the outer peripheral end 43e of the cover 43. Accordingly, the introduction port 66i does not have to be provided on the radially outer side of the impeller 14 whereas the exhaust flow path 19 needs to be provided on the radially outer side of the impeller 14. Accordingly, no large space is required for the communication flow path portion 64 to be formed and the geared centrifugal compressor 1 can be reduced in size.
Since the communication flow path portion 64 is formed in the seal holder 60, machining for forming the communication flow path portion 64 does not have to be performed on the housing main body 21. By attaching the seal member 50 and the seal holder 60 to the housing main body 21, it is possible to realize the geared centrifugal compressor 1 that is capable of reducing the necessary space while reducing the swirling flow that is generated as the impeller 14 rotates.
The communication flow path portion 64 has the introduction flow path 66 and the circumferential flow path 67. With such a configuration, part of the working fluid sent radially outward through the impeller 14 can be merged into the circumferential flow path 67 from the introduction flow path 66 and sent into the plurality of inclined holes 55. Accordingly, the working fluid can be supplied to the plurality of inclined holes 55 under the same conditions regardless of the position in the circumferential direction.
The second fins 53 and 54 are provided on the upstream side in the axis O direction with respect to the first fin 52 and the opening portion 57. Suppressed as a result is direct merging between the working fluid that is ejected from the opening portion 57 of the inclined hole 55 and the pre-compression fluid that has flowed from the upstream side in the axis O direction with respect to the impeller 14. As a result, it is possible to reliably exhibit the effect of suppressing the swirling flow that is attributable to the working fluid ejected from the opening portion 57.
A seal unit 70 is provided with the seal member 50 having the inclined hole 55 and the seal holder 60 having the communication flow path portion 64. By attaching the seal unit 70 to the housing main body 21 of the geared centrifugal compressor 1, it is possible to realize the geared centrifugal compressor 1 that is capable of reducing the necessary space while reducing the swirling flow that is generated as the impeller 14 rotates. Accordingly, it is possible to enhance the effect of swirling flow reduction by adding the seal unit 70 to the existing geared centrifugal compressor 1.
The communication flow path portion 64 is not limited to the structure as in the above embodiment. For example, a seal holder 60B is provided with a communication flow path portion 64B as shown in
The introduction flow path 66B is formed at a plurality of locations spaced in the circumferential direction around the axis O. The introduction flow path 66B has an axial flow path portion 661 and a radial flow path portion 662. The axial flow path portion 661 extends to the upstream side in the axis O direction from an introduction port 66Bi formed in the holder facing surface 60h. The radial flow path portion 662 continuously extends radially inward from the end portion of the axial flow path portion 661 that is on the upstream side in the axis O direction. Preferably, the axial flow path portion 661 and the radial flow path portion 662 have the same flow path cross-sectional area in order to suppress a pressure loss in the introduction flow path 66B.
The circumferential flow path 67B is formed so as to be continuous in the circumferential direction in an inner peripheral surface 60k of the seal holder 60B. The circumferential flow path 67B is formed in a groove shape recessed radially outward from the inner peripheral surface 60k. The radial flow path portions 662 of a plurality of the introduction flow paths 66B communicate with the circumferential flow path 67B.
The outer peripheral portion of the seal member 50 is fitted in the circumferential flow path 67B of the seal holder 60B. The outer peripheral surface 50f of the seal member 50 is provided with a gap provided between the outer peripheral surface 50f of the seal member 50 and a bottom surface 671 of the circumferential flow path 67B. As a result, the circumferential flow path 67B continuous in the circumferential direction is formed between the outer peripheral surface 50f of the seal member 50 and the bottom surface 671.
In the seal holder 60B, the working fluid that has flowed into the axial flow path portion 661 from the introduction port 66Bi of each communication flow path portion 64B merges in the circumferential flow path 67B through the radial flow path portion 662. The working fluid that has flowed into the circumferential flow path 67B is ejected in the direction opposite to the direction of rotation of the rotary shaft 13 through the plurality of inclined holes 55 formed in the seal member 50. Suppressed as a result is swirling flow generation attributable to the working fluid between the seal member 50 and the cover outer peripheral surface 43g of the cover 43 swirling with the rotation of the impeller 14.
While preferred embodiments of the invention have been described and shown above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the gist or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.
For example, in the above-described embodiment, a so-called single-shaft two-stage configuration has been described as an example and as an aspect of the geared centrifugal compressor 1. However, the aspect of the geared centrifugal compressor 1 is not limited thereto and the geared centrifugal compressor 1 may be provided with two or more shafts and four or more stages depending on design and specifications. Regardless of the configuration, the same action and effect as described in the above embodiment can be obtained with the centrifugal compression unit 30 in each stage.
The present invention can be applied not only to the geared centrifugal compressor 1 but also to, for example, a single-shaft multi-stage centrifugal compressor in which the rotary shaft 13 is directly driven to rotate by an external drive source. In that case, it is preferable that the seal member 50 having the inclined hole 55 or the seal holder 60, 60B having the communication flow path portion 64, 64B is provided in the final-stage impeller where the excitation force attributable to the swirling flow is largest on the most downstream side in the flow direction of the working fluid.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-202008 | Oct 2018 | JP | national |
