Impeller and centrifugal compressor

Abstract

To provide an impeller and a centrifugal compressor where an operable rotating speed region can be enlarged by a reduction in stress with a simpler construction.SOLUTION: The impeller includes a disc rotatable around the axis line and having an outer peripheral face extending to the radial outside as heading to one axial side, a plurality of blades arranged on the outer peripheral face of the disc at peripheral intervals, and a cover arranged opposed to the outer peripheral face of the disc to cover the plurality of blades. The front edge of the blade has a straight part extending to one axial side as heading from the cover side to the disc side and a protruded part provided in an area including the end on the disc side and protruded from the front edge.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an impeller and a centrifugal compressor. [Background technology]

[0002] A type of impeller known as a cover type impeller is used in centrifugal compressors. As an example, as described in Patent Document 1 below, this type of impeller has a disk, blades, and a cover. The outer peripheral surface of the disk extends radially outward as it moves toward one axial direction. A plurality of blades are provided on this outer peripheral surface and arranged at intervals in the circumferential direction. A cover covers these blades from the radial outside.

[0003] During operation of a centrifugal compressor, centrifugal force is generated in the impeller as it rotates. This centrifugal force generates high stress on both edge portions of the blades (i.e., the edge on the disk side and the edge on the cover). If such stress is constantly applied to the blades, it may interfere with stable operation of the centrifugal compressor. In other words, the operable rotation speed range of a centrifugal compressor is determined using this stress distribution as an index. Therefore, measures are sometimes taken to increase the thickness of the blades to increase their rigidity and widen the operable rotation speed range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-234803 Summary of the Invention [Problem to be solved by the invention]

[0005] However, simply increasing the blade thickness as described above may result in a decrease in the performance of the centrifugal compressor, which may require a complete review of the shape and dimensions of each part to compensate for this decrease in performance.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an impeller and a centrifugal compressor in which stress is reduced through a simpler configuration, thereby expanding the operable rotation speed range. [Means for solving the problem]

[0007] In order to solve the above problems, the impeller according to the present disclosure comprises a disk that is rotatable about an axis and has an outer peripheral surface that extends radially outward as it moves toward one side in the axial direction, a plurality of blades that are arranged at intervals in the circumferential direction on the outer peripheral surface of the disk, and a cover that is arranged opposite the outer peripheral surface of the disk so as to cover the plurality of blades, and the leading edges of the blades are connected to the cover, It has a straight portion that extends toward one side in the axial direction as it moves from the cover side toward the disk side, and a protruding portion that extends toward the other side in the axial direction as it moves radially inward from the disk-side end of the straight portion and is connected to the outer peripheral surface of the disk.

[0008] The centrifugal compressor according to the present disclosure includes a rotating shaft extending along the axis, the impeller fixed to the rotating shaft, and a casing covering the rotating shaft and the impeller from the outer circumferential side. [Effects of the Invention]

[0009] According to the impeller and centrifugal compressor of the present disclosure, stress is reduced through a simpler configuration, and the operable rotation speed range can be expanded. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing a configuration of a centrifugal compressor according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a view of the impeller according to the first embodiment of the present disclosure as viewed from the circumferential direction. [Figure 3] FIG. 10 is a view of an impeller according to a second embodiment of the present disclosure as viewed from the circumferential direction. [Figure 4] FIG. 10 is a view of an impeller according to a modified example of the present disclosure, viewed from the circumferential direction DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment (Configuration of centrifugal compressor) A centrifugal compressor 1 according to a first embodiment of the present disclosure will be described below with reference to Fig. 1 and Fig. 2. As shown in Fig. 1, the centrifugal compressor 1 includes a rotating shaft 2, a journal bearing 5, a thrust bearing 6, an impeller 20, and a casing 10. The centrifugal compressor 1 of this embodiment is a so-called single-shaft multi-stage centrifugal compressor including multiple stages of impellers 20.

[0012] The rotating shaft 2 has a cylindrical shape extending in the direction of an axis O that is horizontal. The rotating shaft 2 is supported by journal bearings 5 ​​at a first end 3 side (the other side in the direction of axis O) and a second end 4 side (one side in the direction of axis O) in the direction of axis O so as to be rotatable around the axis O. The first end 3 of the rotating shaft 2 is supported by a thrust bearing 6.

[0013] The impellers 20 are fitted onto the outer peripheral surface of the rotary shaft 2, and are provided in multiple stages spaced apart in the direction of the axis O. These impellers 20 rotate together with the rotary shaft 2 about the axis O, thereby compressing and feeding the gas (fluid) flowing in from the direction of the axis O radially outward. The detailed configuration of the impellers 20 will be described later.

[0014] The casing 10 is a cylindrical member that houses the rotating shaft 2, the impeller 20, the journal bearing 5, etc. The casing 10 rotatably supports the rotating shaft 2 via the journal bearing 5. This allows the impeller 20 attached to the rotating shaft 2 to rotate relative to the casing 10. The casing 10 has an inlet flow path 11, a connecting flow path 13, and a discharge flow path 16.

[0015] The introduction flow passage 11 introduces gas from outside the casing 10 to the front-stage impeller 20, which is located furthest in the direction of the axis O, among the multiple impellers 20. The introduction flow passage 11 opens to the outer peripheral surface of the casing 10, and this opening serves as a gas inlet 12. The introduction flow passage 11 is connected at its radially inner portion to the other side in the direction of the axis O of the front-stage impeller 20.

[0016] The connection flow passage 13 is a flow passage that connects a pair of impellers 20 adjacent to each other in the direction of the axis O. The connection flow passage 13 introduces gas that is discharged radially outward from the impeller 20 on the front stage side to the impeller 20 on the rear stage side from the other side in the direction of the axis O. The connection flow passage 13 has a diffuser flow passage 14 and a return flow passage 15. The diffuser passage 14 is connected to the radially outer side of the impeller 20, and converts velocity energy into pressure energy while guiding the gas discharged radially outward from the impeller 20 radially outward. The return passage 15 is connected to the radially outer side of the diffuser passage 14, and turns the gas heading radially outward to the radially inner side, guiding it to the impeller 20 on the subsequent stage.

[0017] The exhaust flow passage 16 exhausts gas that is exhausted radially outward from the last-stage impeller 20, which is located furthest on the other side in the direction of the axis O, out of the casing 10. The exhaust flow passage 16 opens to the outer peripheral surface of the casing 10, and this opening serves as a gas exhaust port 17. A radially inner portion of the exhaust flow passage 16 is connected to the radially outer side of the last-stage impeller 20.

[0018] (Impeller configuration) Next, the detailed configuration of the impeller 20 will be described with reference to Figures 2 and 3. The impeller 20 has a disk 30, blades 40, and a cover . The disk 30 is formed in a disk shape centered on the axis O. A through hole 31 is formed in the disk 30, which has a circular shape centered on the axis O and penetrates in the direction of the axis O. The inner surface of the through hole 31 fits into the outer peripheral surface of the rotating shaft 2, thereby fixing the impeller 20 integrally to the rotating shaft 2.

[0019] The surface of the disk 30 facing the other side in the direction of the axis O is a disk back surface 32 that is flat and perpendicular to the axis O. A disk main surface 33 is formed from the end of the through hole 31 in the disk 30 on the other side in the direction of the axis O to the radially outer end of the disk back surface 32. The disk main surface 33 extends gradually radially outward from the other axial side to one side. The portion of the disk main surface 33 on the other side in the direction of the axis O faces radially outward, and gradually curves toward the other side in the direction of the axis O as it faces one side in the direction of the axis O. In other words, the diameter of the disk main surface 33 gradually increases from the other side in the direction of the axis O to one side. The disk main surface 33 is concavely curved.

[0020] In this embodiment, a disk front end surface 34 having a planar shape perpendicular to the axis O is formed between the end of the disk main surface 33 on the other side in the direction of the axis O and the end of the through-hole 31 on one side in the direction of the axis O. A disk outer end surface 35 extending in the direction of the axis O and forming the outer circumferential edge of the disk 30 is provided between the end of the disk main surface 33 on one side in the direction of the axis O and the end of the disk back surface 32 on the radially outer side.

[0021] A plurality of blades 40 are provided on the disk main surface 33 of the disk 30 at intervals in the circumferential direction of the axis O. Each blade 40 is curved toward the rear side (one circumferential side) in the rotation direction R of the impeller 20 as it moves from the radially inner side to the radially outer side. Each blade 40 extends while forming a convex curved surface that is convex toward the front side in the rotation direction R. Between a pair of adjacent blades 40, a flow path is formed that communicates with the introduction flow path 11 and the connection flow path 13 described above.

[0022] The leading edge 51 of the blade 40 is located close to the end of the cover 36 on the other side in the direction of the axis O. The leading edge 51 is composed of a straight portion S and a notch C. The straight portion S extends toward one side in the direction of the axis O as it moves from the cover 36 side toward the disk 30 side. The notch C is set back from a midpoint of the straight portion S. The notch C has an arc shape when viewed in the circumferential direction. The end of the notch C on the disk 30 side is located away from the outer circumferential surface (disk main surface 33) of the disk 30 toward the cover 36.

[0023] The cutout C is divided into a first portion C1 located on the cover 36 side and a second portion C2 located on the disc 30 side, based on a line L that passes through the center point of the cutout C and is perpendicular to the front edge 51. In this embodiment, the first portion C1 and the second portion C2 form an arc shape that is continuous with each other. Of these, the first portion C1 may have a shape other than an arc shape (for example, a rectangular shape). On the other hand, the second portion C2 is formed in an arc shape regardless of the shape of the first portion C1.

[0024] Furthermore, the extension dimension D of the cutout C (i.e., the dimension from the cover-side end of the cutout C to the disk-side end: the diameter of the arc) is set to 50% or less when the overall dimension of the leading edge 51 is taken as 100%. More preferably, this dimension D is set to 40% or less of the overall leading edge 51. Most preferably, the dimension D is set to 30% or less of the overall leading edge 51.

[0025] The cover 36 covers the multiple blades 40 from the outer periphery. The cover 36 is disposed facing the disk 30 so that the blades 40 are sandwiched between the cover 36 and the disk 30. The inner circumferential surface 37 of the cover 36 is formed so that its diameter gradually increases from the other side toward one side in the direction of the axis O. The inner circumferential surface 37 of the cover 36 is curved in the same manner as the disk main surface 33 so as to correspond to the disk main surface 33. Ends of the blades 40 on the side opposite the disk main surface 33 are fixed to the inner circumferential surface 37 of the cover 36.

[0026] The inner circumferential surface 37 of the cover 36, the disk main surface 33, and the blades 40 define a flow path extending from one side in the direction of the axis O to the other side, curving rearward in the direction of rotation R.

[0027] (Action and effect) Next, the operation of the centrifugal compressor 1 will be described. To drive the centrifugal compressor 1, first, the rotating shaft 2 is rotated by an external power source. As the rotating shaft 2 rotates, the impeller 20 rotates integrally. As a result, an external fluid is taken into the centrifugal compressor 1 through the inlet flow path 11 described above. The fluid is compressed as it flows through the flow path between the blades 40 of the impeller 20, and flows into the connecting flow path 13 as a high-pressure fluid. The fluid that has flowed into the connecting flow path 13 is further compressed by the impeller 20 of the subsequent stage. This cycle is repeated up to the final impeller 20, and finally, the fluid at the target pressure is discharged from the outlet flow path 16.

[0028] Incidentally, during operation of the centrifugal compressor 1, centrifugal force is generated in the impeller 20 as it rotates. This centrifugal force generates high stress on both end edges of the blades 40 (i.e., the edge on the disk 30 side and the edge on the cover 36 side). If such stress is constantly applied to the blades 40, it may hinder stable operation of the centrifugal compressor 1. In other words, the operable rotation speed range of the centrifugal compressor 1 is determined using this stress distribution as an index. Therefore, in this embodiment, a straight portion S and a notched portion C are formed on the leading edge 51 of the blade 40.

[0029] According to the above configuration, the portion where the notch C is formed has lower rigidity than the other portion (straight portion S). Therefore, when centrifugal force accompanying the rotation of the impeller 20 is applied to the blade 40, most of the stress is concentrated in the portion where the notch C is formed. In other words, it is possible to reduce stress generated in the end of the leading edge 51 of the blade 40 on the disk 30 side and the end on the cover 36 side. As a result, it is possible to increase the durability of the impeller 20 against centrifugal force. As a result, it is possible to expand the range of rotational speeds at which the centrifugal compressor 1 can operate.

[0030] According to the above configuration, since the cutout C has an overall arc shape, local stress concentration can be suppressed compared to when the cutout C is formed in a rectangular shape, for example. In other words, the stress distribution in that portion can be made gentler. Therefore, while the stress is actively concentrated in the cutout C of the entire leading edge 51, the stress distribution within the cutout C can be made uniform.

[0031] According to the above configuration, the end of the cutout C on the disk 30 side is located away from the outer peripheral surface of the disk 30 toward the cover 36, so that stress can be concentrated at the cutout C while ensuring the rigidity of the blade 40.

[0032] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Fig. 3. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in Fig. 3, in this embodiment, the configuration of the impeller 20b is different from that in the first embodiment.

[0033] In the impeller 20b, the portion of the leading edge 51 on the cover 36 side is a straight portion S, and the portion on the disk 30 side of the straight portion S is a notched portion Cb. In other words, the radially inner end of this notched portion Cb (the end on the disk 30 side) is in contact with the outer peripheral surface of the disk 30 (the disk main surface 33).

[0034] The extension dimension D of the cutout Cb (i.e., the dimension from the cover-side end of the cutout Cb to the disk-side end: the diameter of the arc) is set to 10% or more and 40% or less when the overall dimension of the leading edge 51 is 100%. More preferably, this dimension D is set to 20% or more and 40% or less of the overall dimension of the leading edge 51. Most preferably, the dimension D is set to 40% of the overall dimension of the leading edge 51.

[0035] According to the above configuration, the end of the cutout Cb on the disk 30 side is in contact with the outer peripheral surface of the disk 30, so that the rigidity of the blade 40 can be ensured while further concentrating stress on the cutout Cb.

[0036] (Other embodiments) The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure. For example, as shown in FIG. 4, impeller 20c may have a protrusion P protruding from leading edge 51 at a portion of leading edge 51 that includes the end portion on the disk 30 side. This protrusion P extends radially inward toward the other side in the direction of axis O. The edge of protrusion P has a curved surface that is concave toward disk 30. With this configuration, most of the stress generated in blade 40 can be concentrated at protrusion P.

[0037] <Additional Notes> The impeller described in each embodiment can be understood, for example, as follows.

[0038] (1) The impeller of the first aspect comprises a disk rotatable about an axis and having an outer peripheral surface extending radially outward as it moves toward one side in the axial direction, a plurality of blades arranged at intervals circumferentially on the outer peripheral surface of the disk, and a cover arranged opposite the outer peripheral surface of the disk so as to cover the plurality of blades, wherein the leading edges of the blades have a straight portion extending toward one side in the axial direction as they move from the cover side to the disk side, and a notch that is set back from the straight portion and has at least the portion on the disk side formed in an arc shape when viewed circumferentially.

[0039] According to the above configuration, a notch C is formed in the leading edge 51 of the blade 40. As a result, the portion where the notch C is formed has lower rigidity than the other portion (straight portion S). Therefore, when centrifugal force caused by the rotation of the impeller 20 is applied to the blade 40, most of the stress is concentrated in the portion where the notch C is formed. In other words, it is possible to minimize stress generated in the end of the leading edge 51 of the blade 40 on the disk 30 side and the end on the cover 36 side. As a result, it is possible to increase the durability of the impeller 20 against centrifugal force.

[0040] (2) In the impeller 20 according to the second aspect, the portion of the cutout C on the cover 36 side is formed in an arc shape when viewed in the circumferential direction.

[0041] According to the above configuration, since the cutout C has an overall arc shape, local stress concentration can be suppressed compared to when the cutout C is formed in a rectangular shape, for example. In other words, the stress distribution in that portion can be made gentler. Therefore, while the stress is actively concentrated in the cutout C of the entire leading edge 51, the stress distribution within the cutout C can be made uniform.

[0042] (3) In the impeller 20 according to the third aspect, the end of the cutout C on the disk 30 side is located at a position spaced from the outer circumferential surface of the disk 30 toward the cover .

[0043] According to the above configuration, the end of the cutout C on the disk 30 side is located away from the outer peripheral surface of the disk 30 toward the cover 36, so that stress can be concentrated at the cutout C while ensuring the rigidity of the blade 40.

[0044] (4) In the impeller 20 according to the fourth aspect, the length from the end of the cutout C on the disk 30 side to the end on the cover 36 side is 30% or less of the length of the leading edge 51 .

[0045] According to the above configuration, stress can be concentrated at the notch C while ensuring the rigidity of the blade 40.

[0046] (5) In the impeller 20 b according to the fifth embodiment, the end of the cutout portion Cb on the disk 30 side is in contact with the outer circumferential surface of the disk 30 .

[0047] According to the above configuration, the end of the cutout Cb on the disk 30 side is in contact with the outer peripheral surface of the disk 30, so that the rigidity of the blade 40 can be ensured while stress is concentrated on the cutout Cb.

[0048] (6) In the impeller 20b according to the sixth aspect, the length from the end of the cutout portion Cb on the disk 30 side to the end on the cover 36 side is 20% to 40% of the length of the leading edge 51.

[0049] According to the above configuration, the rigidity of the blade 40 can be ensured while stress is concentrated at the notch Cb.

[0050] (7) A centrifugal compressor 1 according to a seventh aspect includes a rotating shaft 2 extending along the axis O, an impeller 20, 20b according to any one of the above aspects fixed to the rotating shaft 2, and a casing 10 covering the rotating shaft 2 and the impeller 20, 20b from the outer circumferential side.

[0051] According to the above configuration, the durability of the impellers 20, 20b against centrifugal force is increased, so that the range of rotational speeds at which the centrifugal compressor 1 can operate can be further expanded. [Explanation of symbols]

[0052] 1 Compressor 2 rotation axes 3 First end 4 Second end 5 Journal bearings 6 Thrust bearing 10 Casing 11 Inlet channel 12 Intake port 13 Connecting Channel 14 Diffuser passage 15 Return flow path 16 Discharge flow path 17 Outlet 20, 20b, 20c Impeller 30 discs 31 Through hole 32 Back of disc 33 Main surface of disk 34 Front end face of disc 35 Outer end face of disc 36 Cover 37 Inner surface 40 blades 51 leading edge 52 Trailing edge C, Cb Notch C1 first part C2 second part L equisector O axis P protrusion S Straight section

Claims

1. a disk rotatable about an axis and having an outer peripheral surface extending radially outward as it moves toward one side in the axial direction; a plurality of blades arranged at intervals in the circumferential direction on the outer peripheral surface of the disk; a cover disposed opposite to an outer peripheral surface of the disk so as to cover the plurality of blades; Equipped with The leading edge of the blade a linear portion connected to the cover and extending from the cover side toward the disk side toward one side in the axial direction; a protruding portion extending radially inward from an end of the straight portion on the disk side toward the other side in the axial direction and connected to an outer peripheral surface of the disk; An impeller having

2. The impeller according to claim 1 , wherein the protrusion extends radially inward from the outer side to the other side in the axial direction.

3. 3. The impeller according to claim 1, wherein an edge of the protrusion has a curved surface that is concave toward the disk.

4. a rotation shaft extending along the axis; The impeller according to claim 1 or 2 fixed to the rotary shaft; a casing that covers the rotary shaft and the impeller from the outer periphery side; A centrifugal compressor comprising:

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