CN116104776A - Diffuser for centrifugal compressor - Google Patents

Abstract

A diffuser for a centrifugal compressor includes at least one diffuser passage. The at least one diffusion passage outputs fluid along a radial direction of the centrifugal compressor and is configured to diffuse fluid entering the diffuser, each of the at least one diffusion passages being defined by upstream and downstream wall surfaces disposed opposite each other perpendicular to an axis of the centrifugal compressor. Wherein, be equipped with at least two rings of first concave parts on the upstream wall, every round first concave part is formed from the surface depression of upstream wall to around centrifugal compressor's axis setting. Wherein, be equipped with at least two rings of second concave parts on the downstream wall, every circle the second concave part is formed from the surface depression of downstream wall to around centrifugal compressor's axis setting. The diffuser in the present application has the advantage of suppressing the occurrence of surge when the flow rate of the centrifugal compressor is small.

Description

Diffuser for centrifugal compressor

Technical Field

The present application relates to the field of centrifugal compressors, and in particular to diffusers for centrifugal compressors.

Background

In the prior art, when the flow rate of a centrifugal compressor is reduced, the compressor is prone to surge.

Disclosure of Invention

The present application provides a diffuser for a centrifugal compressor that includes at least one diffuser passage. The at least one diffusion passage outputs fluid along a radial direction of the centrifugal compressor and is configured to diffuse fluid entering the diffuser, each of the at least one diffusion passages being defined by upstream and downstream wall surfaces disposed opposite each other perpendicular to an axis of the centrifugal compressor. Wherein, be equipped with at least two rings of first concave parts on the upstream wall, every round first concave part is formed from the surface depression of upstream wall to around centrifugal compressor's axis setting. Wherein, be equipped with at least two rings of second concave parts on the downstream wall, every circle the second concave part is formed from the surface depression of downstream wall to around centrifugal compressor's axis setting.

According to the above-described diffuser for a centrifugal compressor, the first recess and the second recess are disposed offset with respect to each other in a radial direction of the centrifugal compressor.

According to the diffuser for the centrifugal compressor, the at least two circles of first concave portions and the at least two circles of second concave portions are arranged in a staggered manner in the radial direction of the centrifugal compressor.

The diffuser for a centrifugal compressor as described above, each of the at least two circles of first concave portions and each of the at least two circles of first concave portions includes a curved portion and a straight portion, the curved portion and the straight portion being connected, the curved portion being closer to an axis of the centrifugal compressor than the straight portion. On the radial section of the centrifugal compressor, the curved part is arc-shaped, and the straight section part is straight line.

The diffuser for a centrifugal compressor according to the above, each of the at least two circles of first concave portions and each of the at least two circles of first concave portions further includes an additional straight section portion, and the curved portion is disposed between and connected to the straight section portion and the additional straight section portion. The additional straight section is straight in a radial section of the centrifugal compressor.

According to the above-described diffuser for a centrifugal compressor, the inlet of each of the diffuser passages is located at the center of the upstream wall surface, and the outlet of each of the diffuser passages is located at the position where the diameters of the upstream wall surface and the downstream wall surface are the largest.

The diffuser for a centrifugal compressor according to the above, wherein the at least one diffuser passage is one diffuser passage. The diffuser further includes oppositely disposed first and second diffuser plates, the first diffuser plate forming the upstream wall and the second diffuser plate forming the downstream wall.

The diffuser for a centrifugal compressor according to the above, wherein the at least one diffuser passage is at least two diffuser passages. The diffuser further comprises a first diffuser plate, a second diffuser plate and at least one partition plate, wherein the first diffuser plate and the second diffuser plate are oppositely arranged, the first diffuser plate forms the upstream wall surface, and the second diffuser plate forms the downstream wall surface. The at least one baffle is disposed between the first diffuser plate and the second diffuser plate to form the at least two diffuser passages.

The present application also provides a diffuser for a centrifugal compressor that includes a first diffuser plate, a second diffuser plate, and at least three vanes. The second diffuser plate is disposed on one side of the first diffuser plate at a distance from the first diffuser plate. The at least three vanes are disposed between and in abutment with the first and second diffuser plates. Wherein adjacent two vanes, the first diffuser plate, and the second diffuser plate define diffuser passages, each having an inlet proximate to an axis of the centrifugal compressor and an outlet distal from the axis of the centrifugal compressor. At least two first concave parts and at least two second concave parts are respectively arranged on two opposite wall surfaces of the diffusion channel, the at least two first concave parts are arranged along the direction from the inlet to the outlet, and the at least two second concave parts are arranged along the direction from the inlet to the outlet.

According to the above-described diffuser for a centrifugal compressor, the at least three blades are uniformly disposed in the circumferential direction of the centrifugal compressor, and the direction in which each of the at least three blades is disposed is inclined to the radial direction of the centrifugal compressor.

According to the above-mentioned diffuser for a centrifugal compressor, the at least two first concave portions and the at least two second concave portions are provided on the first diffuser plate and the second diffuser plate, respectively, which form the diffuser passage, and the at least two first concave portions and the at least two second concave portions are formed extending in the circumferential direction of the centrifugal compressor. Each of the first recess and the second recess includes a curved portion and a straight portion, the curved portion and the straight portion being connected, the curved portion being closer to an axis of the diffuser than the straight portion. On the radial section of the diffuser, the curved part is arc-shaped, and the straight section part is straight line.

The diffuser for a centrifugal compressor according to the above, each of the first recess and the second recess further includes an additional straight section portion, the curved portion being disposed between and connected to the straight section portion and the additional straight section portion. The additional straight section is straight in a radial cross section of the diffuser.

According to the diffuser for a centrifugal compressor described above, the at least two first concave portions and the at least two second concave portions are provided on the opposite two wall surfaces of the adjacent two blades, respectively. Each of the first recess and the second recess includes a curved portion and a straight portion, the curved portion and the straight portion being connected, the curved portion being closer to an axis of the centrifugal compressor than the straight portion. On the axial section of the centrifugal compressor, the curved part is arc-shaped, and the straight section part is straight line.

The diffuser for a centrifugal compressor according to the above, each of the first recess and the second recess further includes an additional straight section portion, the curved portion being disposed between and connected to the straight section portion and the additional straight section portion. The additional straight section is straight in an axial section of the centrifugal compressor.

The diffuser can inhibit the occurrence of surge when the flow rate of the centrifugal compressor is small.

Drawings

The features and advantages of the present application may be better understood by reading the following detailed description taken in conjunction with the drawings in which like reference designators refer to like elements throughout, and in which:

FIG. 1A is a perspective view of a centrifugal compressor of the present application;

FIG. 1B is a partial cross-sectional view of the centrifugal compressor shown in FIG. 1A, illustrating a first embodiment of a diffuser;

FIG. 1C is a schematic cross-sectional view of the diffuser 126;

FIG. 2 is an enlarged view of the circle in FIG. 1B, which is a schematic cross-sectional view of the diffuser;

FIG. 3A is a schematic view of a first embodiment of a recess;

FIG. 3B is a schematic illustration of the flow of fluid when the flow rate of the centrifugal compressor is small;

FIG. 3C is a schematic view of a second embodiment of a recess;

FIG. 4A is a perspective view of a portion of a second embodiment of a diffuser;

FIG. 4B is a partial cross-sectional view of a portion of a second embodiment of a diffuser;

FIG. 5A is a perspective view of a portion of a third embodiment of a diffuser;

FIG. 5B is a partial front view of a portion of a third embodiment of a diffuser;

FIG. 6A is a third embodiment of a recess of the present application;

FIG. 6B is a fourth embodiment of a recess of the present application;

FIG. 7A is a perspective view of a portion of a fourth embodiment of a diffuser of the present application;

fig. 7B is a partial cross-sectional view of a portion of a fourth embodiment of a diffuser.

Detailed Description

Various embodiments of the present invention are described below with reference to the accompanying drawings, which form a part hereof. It is to be understood that, although directional terms, such as "front", "rear", "upper", "lower", "left", "right", etc., may be used in describing various exemplary structural portions and elements of the present invention, these terms are used herein for convenience of description only and are determined based on the exemplary orientations shown in the drawings. Since the disclosed embodiments of the invention may be arranged in a variety of orientations, these directional terms are used by way of illustration only and are in no way limiting. In the following drawings, like parts are given like reference numerals.

Fig. 1A is a perspective view of a centrifugal compressor of the present application. FIG. 1B is a partial cross-sectional view of the centrifugal compressor shown in FIG. 1A, illustrating a first embodiment of a diffuser 126. As shown in fig. 1A-1B, the centrifugal compressor includes a housing 112, a baffle 114, an impeller 115, and a diffuser 126. The housing 112 defines a housing cavity and an annular cavity located therein. The housing 112 has an inlet 102 in communication with the housing cavity and an outlet 104 in communication with the annular cavity. A baffle 114 and impeller 115 are disposed in the housing volume. The baffle 114 is used to baffle fluid entering from the inlet 102. Impeller 115 has an impeller axis X (i.e., axis X of the centrifugal compressor). The inlet 102 is generally circular with its center located on the axis X of the centrifugal compressor. The impeller 115 is rotatable about the impeller axis X to accelerate fluid through the inlet 102 and the baffle 114. A diffuser 126 is disposed in the housing volume and downstream of the impeller 115. The diffuser 126 is capable of diffusing fluid entering the diffuser 126 (i.e., fluid exiting the impeller 115). The annular volume is disposed substantially about the axis X of the centrifugal compressor. The outlet of the diffuser 126 communicates with the annular volume such that the diffused fluid can enter the annular volume and exit the outlet 104.

FIG. 1C is a schematic cross-sectional view of the diffuser 126. As shown in fig. 1C, the diffuser 126 includes a diffuser passage 132. The diffuser passage 132 is defined by the first diffuser plate 116 and the second diffuser plate 118. The first diffuser plate 116 and the second diffuser plate 118 are oppositely disposed perpendicular to the axis X of the centrifugal compressor. The first diffuser plate 116 is generally annular. The inlet 122 of the diffuser passage 132 is centered on the first diffuser plate 116 and the inlet 102 is centered on the axis X of the centrifugal compressor. The second diffuser plate 118 is generally disc-shaped. The outlet 124 of the diffuser passage 132 is located where the diameters of the first and second diffuser plates 116, 118 are greatest. The diffuser passage 132 outputs fluid in the radial direction of the centrifugal compressor.

Fig. 2 is an enlarged view of the circle in fig. 1B, which is a schematic cross-sectional view of the diffuser 126. In fig. 2, the inlet 122 of the diffuser passage 132 is located below and the outlet 124 of the diffuser passage 132 is located above. As shown in fig. 2, the first diffuser plate 116 forms an upstream wall 201. The second diffuser plate 118 forms a downstream wall 203. The specific structure on the upstream wall 201 and the downstream wall 203 will be described below:

four turns of the first concave portion 212 are provided on the upstream wall surface 201. Each turn of the first concave portion 212 is concavely formed from the surface of the upstream wall surface 201 and is disposed around the axis X of the centrifugal compressor. In other words, the center of each turn of the first recess 212 is located on the axis X of the centrifugal compressor. Five turns of the second concave portion 214 are provided on the downstream wall surface 203. Each turn of the second recess 214 is concavely formed from the surface of the downstream wall surface 203 and is disposed around the axis X of the centrifugal compressor. In other words, the center of each turn of the second recess 214 is located on the axis X of the centrifugal compressor. The four circles of first concave portions 212 and the five circles of second concave portions 214 are arranged alternately with each other in the radial direction of the centrifugal compressor. In other words, in the radial direction of the centrifugal compressor, four turns of the first concave portions 212 and five turns of the second concave portions 214 are arranged at intervals. Wherein each turn of the second recesses 214 and each turn of the second recesses 214 are arranged offset with respect to each other in the radial direction of the centrifugal compressor. In other words, the second recess 214 and the projection of the second recess 214 along the axis X of the centrifugal compressor do not coincide.

On the upstream wall surface 201, the distance between the inner edge of the first recess 212 of the innermost ring of the four circles of first recesses 212 (i.e., closest to the axis X of the centrifugal compressor) and the outer edge of the first recess 212 of the outermost ring of the four circles of first recesses 212 (i.e., furthest from the axis X of the centrifugal compressor) is the first distance D1. On the downstream wall surface 203, a distance between an inner edge of the second recess 214 of the innermost ring of the five rings of second recesses 214 (i.e., closest to the axis X of the centrifugal compressor) and an outer edge of the second recess 214 of the outermost ring of the five rings of second recesses 214 (i.e., furthest from the axis X of the centrifugal compressor) is a second distance D2. Referring to fig. 1C, the distance between the inlet 122 and the outlet 124 is a radial length L. As an embodiment, the first distance D1 and the radial length L satisfy: D1/L is more than or equal to 0.5. The second distance D2 and the radial length L satisfy: D2/L is more than or equal to 0.5.

Fig. 3A is a first embodiment of the recesses (i.e., first recess 212 and second recess 214) of the present application. As shown in fig. 3A, each of the four turns of the first concave portion 212 and each of the five turns of the second concave portion 214 include a curved portion 302 and a straight portion 304. The curved portion 302 and the straight portion 304 are connected, and the curved portion 302 is closer to the axis X of the centrifugal compressor than the straight portion 304. In a radial cross section of the centrifugal compressor, the curved portion 302 is arc-shaped and the straight portion 304 is straight.

After fluid enters the diffuser passage 132 from the diffuser inlet 122. The fluid will move along the diffuser passage 132 generally in the radial direction of the centrifugal compressor. A portion of the fluid located at the center (i.e., the main flow) continues to flow generally radially outward of the centrifugal compressor, and a portion of the fluid proximate the upstream wall 201 and the downstream wall 203 flows from the end of the curved portion 302 proximate the axis X of the centrifugal compressor (i.e., point B as shown in fig. 3A), then flows through the curved portion 302 and the straight portion 304, and finally reaches the end of the straight portion 304 distal from the axis X of the centrifugal compressor (i.e., point a as shown in fig. 3A) and flows into the main flow.

Fig. 3B is a schematic flow diagram of the fluid at a smaller flow rate of the centrifugal compressor. As shown in FIG. 3B, when the centrifugal compressor flow is low, stall pockets are created in the diffuser passage 132. The stall bolus may be a bolus of fluid that flows at a lower velocity than the bulk fluid, or may be a rotating vortex. When a stall bolus is created in the diffuser passage 132, it affects the proximity of the upstream and downstream walls 201, 203 such that fluid proximate the upstream and downstream walls 201, 203 enters the adjacent first and/or second recesses 212, 214 before passing through the end of the straight section 304 that is distal from the axis X of the centrifugal compressor (i.e., point A in FIG. 3A), and after passing through the straight sections 304 and Qu Bu 302, reaches the end of the curved section 302 that is proximal to the axis X of the centrifugal compressor (i.e., point B in FIG. 3A). The counter-flowing fluid may impinge on the stall bolus in the main flow, thereby breaking up the stall bolus to inhibit surge from occurring.

Fig. 3C is a second embodiment of the recesses (i.e., first recess 212 and second recess 214) of the present application. Compared to the first embodiment of fig. 3A, the second embodiment of the recess shown in fig. 3C (i.e., the first recess 212 and the second recess 214) further comprises an additional straight section 306. The curved portion 302 is disposed between the straight portion 304 and the additional straight portion 306, and is connected to the straight portion 304 and the additional straight portion 306. The additional straight section 306 is a straight line in the radial section of the centrifugal compressor.

Fig. 4A is a perspective view of a portion of a second embodiment of a diffuser 126 of the present application, and fig. 4B is a partial cross-sectional view of the second embodiment of the diffuser 126 of the present application. As shown in fig. 4A-4B, the second embodiment of the diffuser 126 differs from the first embodiment of the diffuser 126 primarily in that: two diffuser passages 132 are arranged in the second embodiment of the diffuser 126. Specifically, the second embodiment of the diffuser 126 further includes a baffle 402 and a mount 404. The spacer 402 is generally annular. The partition 402 is coupled to the second diffuser plate 118 by fasteners 404 such that the partition 402 is disposed between the first diffuser plate 116 and the second diffuser plate 118 to form the two diffuser passages 132. For the diffuser passage 132 on the left side, the first diffuser plate 116 forms an upstream wall 201 and the left surface of the partition 402 forms a downstream wall 203. For the diffuser passage 132 on the right side, the right surface of the partition 402 forms an upstream wall 201 and the second diffuser plate 118 forms a downstream wall 203. Nine first concave portions 212 are provided on the upstream wall surface 201 of the diffuser passage 132 on the left side, and nine second concave portions 214 are provided on the downstream wall surface 203 of the diffuser passage 132 on the left side. The nine circles of first concave portions 212 and the nine circles of second concave portions 214 are arranged alternately with each other in the radial direction of the centrifugal compressor. In other words, nine circles of the first concave portions 212 and nine circles of the second concave portions 214 are arranged at intervals in the radial direction of the centrifugal compressor. Wherein each turn of the second recesses 214 and each turn of the second recesses 214 are arranged offset with respect to each other in the radial direction of the centrifugal compressor. In other words, the second recess 214 and the projection of the second recess 214 along the axis X of the centrifugal compressor do not coincide.

Eight circles of first concave portions 212 are provided on the upstream wall surface 201 of the right diffuser passage 132, and nine circles of second concave portions 214 are provided on the downstream wall surface 203 of the right diffuser passage 132. Eight circles of first concave portions 212 and nine circles of second concave portions 214 are arranged alternately with each other in the radial direction of the centrifugal compressor. In other words, in the radial direction of the centrifugal compressor, eight turns of the first concave portions 212 and nine turns of the second concave portions 214 are arranged at intervals. Wherein each turn of the second recesses 214 and each turn of the second recesses 214 are arranged offset with respect to each other in the radial direction of the centrifugal compressor. In other words, the second recess 214 and the projection of the second recess 214 along the axis X of the centrifugal compressor do not coincide.

For the first recess 212 and the second recess 214 on both sides of each diffuser passage 132, the first distance D1 and the radial length L thereof satisfy: D1/L is more than or equal to 0.5. The second distance D2 and the radial length L satisfy: D2/L is more than or equal to 0.5.

The structures of the at least two circles of the first concave portions 212 and the at least two circles of the second concave portions 214 in the second embodiment of the diffuser 126 are the same as those of the at least two circles of the first concave portions 212 and the at least two circles of the second concave portions 214 in the first embodiment of the diffuser 126, and will not be described here again.

It should be noted that, although a specific number of turns of the first concave portion 212 and the second concave portion 214 are illustrated in the first and second embodiments of the diffuser 126, at least two turns of the first concave portion 212 and at least two turns of the second concave portion 214 are within the scope of the present application.

Fig. 5A is a perspective view of a portion of a third embodiment of a diffuser 126 of the present application, and fig. 5B is a partial front view of a portion of a third embodiment of a diffuser 126 shown in fig. 5A. The third embodiment of the diffuser 126 differs from the first embodiment of the diffuser 126 primarily in that: ten diffuser passages 132 are arranged in the third embodiment of the diffuser 126. Specifically, as shown in fig. 5A-5B, the diffuser 126 includes a first diffuser plate 116, a second diffuser plate 118, and ten vanes 502. The second diffuser plate 118 is disposed on the right side of the first diffuser plate 116 and is spaced apart from the first diffuser plate 116. Ten vanes 502 are disposed between the first and second diffuser plates 116, 118 and abut the first and second diffuser plates 116, 118 such that adjacent two vanes 502, the first and second diffuser plates 116, 118 define the diffuser passage 132. In other words, ten diffuser passages 132 can be formed between ten vanes 502. The diffuser passage 132 has an inlet 122 and an outlet 124. Inlet 122 is proximate to axis X of the centrifugal compressor and outlet 124 is distal to axis X of the centrifugal compressor. The ten blades 502 are uniformly disposed along the circumferential direction of the centrifugal compressor, and each blade 502 is disposed inclined to the radial direction of the centrifugal compressor such that the width of the inlet 122 of each diffuser passage 132 is smaller than the width of the outlet 124 in the circumferential direction of the centrifugal compressor.

The vanes 502 on both sides of each diffuser passage 132 form a first wall and a second wall, respectively. Two first recesses 512 are provided on the first wall surface, and two second recesses 514 are provided on the second wall surface and are arranged in a direction from the inlet 122 to the outlet 124, respectively.

Fig. 6A is a third embodiment of the recesses (i.e., first recess 512 and second recess 514) of the present application. As shown in fig. 6A, each of the first recess 512 and the second recess 514 includes a curved portion 302 and a straight portion 304. The curved portion 302 and the straight portion 304 are connected, and the curved portion 302 is closer to the axis X of the centrifugal compressor than the straight portion 304. In the axial section of the centrifugal compressor, the curved portion 302 is arc-shaped and the straight portion 304 is straight.

Fig. 6B is a fourth embodiment of the recesses (i.e., first recess 512 and second recess 514) of the present application. The fourth embodiment of the first recess 512 and the second recess 514 shown in fig. 6B further comprises an additional straight section 306 compared to the third embodiment of fig. 6A. The curved portion 302 is disposed between the straight portion 304 and the additional straight portion 306, and is connected to the straight portion 304 and the additional straight portion 306. The additional straight portion 306 is a straight line in the axial section of the centrifugal compressor.

In the third and fourth embodiments of the recess (i.e., the first recess 512 and the second recess 514), the first recess 512 and the second recess 514 are channel-like, respectively. The inlet and outlet of the passage are provided on the wall surfaces (i.e., the first wall surface and the second wall surface), and the passage is formed extending toward the inside of the vane. The vane 502 is integrally formed with the second diffuser plate 118. The first recess 512 and the second recess 514 are made by machining.

Fig. 7A is a perspective view of a portion of a fourth embodiment of a diffuser 126 of the present application, and fig. 7B is a partial cross-sectional view of a portion of a fourth embodiment of a diffuser 126 shown in fig. 7A. The fourth embodiment of the diffuser 126 shown in fig. 7A-7B differs from the third embodiment of the diffuser 126 shown in fig. 5A-5B primarily in that: in the third embodiment, the first and second recesses 512 and 514 are provided on the vane 502 on both sides of the diffuser passage 132, while in the fourth embodiment, the first and second recesses 512 and 514 are provided on the first and second diffuser plates 116 and 118 on both sides of the diffuser passage 132. Specifically, for each diffuser passage 132, a first recess 512 and a second recess 514 are formed extending in the circumferential direction of the centrifugal compressor, respectively, and extend to the side walls of the vanes 502 on both sides of the diffuser passage 132. The first recess 512 and the second recess 514 are offset relative to each other in the radial direction of the centrifugal compressor. The specific shape of the first recess 512 and the second recess 514 may be formed as recessed from the surface of the wall surface as described in fig. 3A-3B, or may be channel-like as described in fig. 6A-6B. Specifically, each of the first recess 512 and the second recess 514 includes a curved portion 302 and a straight portion 304. The curved portion 302 and the straight portion 304 are connected, and the curved portion 302 is closer to the axis X of the centrifugal compressor than the straight portion 304. In a radial cross section of the centrifugal compressor, the curved portion 302 is arc-shaped and the straight portion 304 is straight. In another embodiment, the first recess 512 and the second recess 514 further comprise additional straight sections 306. The curved portion 302 is disposed between the straight portion 304 and the additional straight portion 306, and is connected to the straight portion 304 and the additional straight portion 306. The additional straight section 306 is a straight line in the radial section of the centrifugal compressor.

It should be noted that although a specific number of vanes are shown in the third and fourth embodiments of the diffuser 126, at least three vanes are within the scope of the present application.

While the present disclosure has been described in conjunction with the examples of embodiments outlined above, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or that are or may be presently or later be envisioned, may be apparent to those of ordinary skill in the art. Further, the technical effects and/or technical problems described in the present specification are exemplary rather than limiting; the disclosure in this specification may be used to solve other technical problems and to have other technical effects and/or may solve other technical problems. Accordingly, the examples of embodiments of the disclosure as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit or scope of the disclosure. Accordingly, the present disclosure is intended to embrace all known or earlier developed alternatives, modifications, variations, improvements and/or substantial equivalents.

Claims (14)

1. A diffuser for a centrifugal compressor, characterized by: the diffuser includes:

at least one diffusion passage (132), the at least one diffusion passage (132) outputting fluid along a radial direction of the centrifugal compressor and configured to diffuse fluid entering the diffuser, each of the at least one diffusion passages (132) being defined by an upstream wall (201) and a downstream wall (203) disposed opposite perpendicular to an axis of the centrifugal compressor;

wherein at least two circles of first concave parts (212) are arranged on the upstream wall surface (201), and each circle of first concave parts (212) is concavely formed from the surface of the upstream wall surface (201) and is arranged around the axis of the centrifugal compressor;

wherein, be equipped with at least two rings of second concave parts (214) on downstream wall (203), every round second concave part (214) are formed from the surface depression of downstream wall (203) to set up around the axis of centrifugal compressor.

2. The diffuser for a centrifugal compressor according to claim 1, wherein:

the first recess (212) and the second recess (214) are offset relative to each other in the radial direction of the centrifugal compressor.

3. The diffuser for a centrifugal compressor according to claim 1, wherein:

the at least two circles of first concave parts (212) and the at least two circles of second concave parts (214) are mutually staggered in the radial direction of the centrifugal compressor.

4. The diffuser for a centrifugal compressor according to claim 1, wherein:

each of the at least two turns of first recesses (212) and each of the at least two turns of first recesses (212) comprises a curved portion (302) and a straight portion (304), the curved portion (302) and the straight portion (304) being connected, the curved portion (302) being closer to the axis of the centrifugal compressor than the straight portion (304);

the radial section of the centrifugal compressor is provided with an arc-shaped curved part (302), and the straight section part (304) is a straight line.

5. The diffuser for centrifugal compressors according to claim 4, wherein:

each of the at least two circles of first recesses (212) and each of the at least two circles of first recesses (212) further comprises an additional straight section (306), the curved section (302) being arranged between the straight section (304) and the additional straight section (306) and being connected to the straight section (304) and the additional straight section (306);

the additional straight section (306) is straight in radial cross section of the centrifugal compressor.

6. The diffuser for a centrifugal compressor according to claim 1, wherein:

the inlet (122) of each diffusion passage (132) is positioned at the center of the upstream wall surface (201), and the outlet (124) of each diffusion passage (132) is positioned at the position where the diameters of the upstream wall surface (201) and the downstream wall surface (203) are the largest.

7. The diffuser for a centrifugal compressor according to claim 1, wherein:

the at least one diffuser passage (132) is a diffuser passage (132);

the diffuser further includes oppositely disposed first and second diffuser plates (116, 118), the first diffuser plate (116) forming the upstream wall (201) and the second diffuser plate (118) forming the downstream wall (203).

8. The diffuser for a centrifugal compressor according to claim 1, wherein:

the at least one diffusion channel (132) is at least two diffusion channels (132);

the diffuser further comprises a first diffuser plate (116), a second diffuser plate (118) and at least one partition plate (402), wherein the first diffuser plate (116) and the second diffuser plate (118) are arranged oppositely, the first diffuser plate (116) forms the upstream wall surface (201), and the second diffuser plate (118) forms the downstream wall surface (203);

the at least one baffle (402) is disposed between the first diffuser plate (116) and the second diffuser plate (118) to form the at least two diffuser passages (132).

9. A diffuser for a centrifugal compressor, characterized by: the diffuser includes:

a first diffuser plate (116);

a second diffuser plate (118), the second diffuser plate (118) being disposed on one side of the first diffuser plate (116) at a distance from the first diffuser plate (116); and

at least three vanes (502), the at least three vanes (502) being disposed between the first diffuser plate (116) and the second diffuser plate (118) and abutting the first diffuser plate (116) and the second diffuser plate (118);

wherein adjacent two vanes (502), the first diffuser plate (116), and the second diffuser plate (118) define diffuser passages (132), each of the diffuser passages (132) having an inlet (122) proximate an axis of the centrifugal compressor and an outlet (124) distal the axis of the centrifugal compressor;

at least two first concave parts (512) and at least two second concave parts (514) are respectively arranged on two opposite wall surfaces of the diffusion passage (132), the at least two first concave parts (512) are arranged along the direction from the inlet (122) to the outlet (124), and the at least two second concave parts (514) are arranged along the direction from the inlet (122) to the outlet (124).

10. The diffuser for centrifugal compressors according to claim 9, wherein:

the at least three blades (502) are uniformly arranged along the circumferential direction of the centrifugal compressor, and the arrangement direction of each of the at least three blades (502) is inclined to the radial direction of the centrifugal compressor.

11. The diffuser for centrifugal compressors according to claim 9, wherein:

the at least two first recesses (512) and the at least two second recesses (514) are respectively provided on the first diffuser plate (116) and the second diffuser plate (118) forming the diffuser passage (132), and the at least two first recesses (512) and the at least two second recesses (514) are formed extending in the circumferential direction of the centrifugal compressor;

each of the first recess (512) and the second recess (514) comprises a curved portion (302) and a straight portion (304), the curved portion (302) and the straight portion (304) being connected, the curved portion (302) being closer to the diffuser axis than the straight portion (304);

in a radial section of the diffuser, the curved portion (302) is arc-shaped, and the straight portion (304) is straight.

12. The diffuser for centrifugal compressors according to claim 11, wherein:

each of the first recess (512) and the second recess (514) further comprises an additional straight section (306), the curved section (302) being arranged between the straight section (304) and the additional straight section (306) and being connected to the straight section (304) and the additional straight section (306);

the additional straight section (306) is straight in radial cross section of the diffuser.

13. The diffuser for centrifugal compressors according to claim 9, wherein:

the at least two first recesses (512) and the at least two second recesses (514) are respectively arranged on two opposite wall surfaces of the two adjacent blades (502);

each of the first recess (512) and the second recess (514) comprises a curved portion (302) and a straight portion (304), the curved portion (302) and the straight portion (304) being connected, the curved portion (302) being closer to the axis of the centrifugal compressor than the straight portion (304);

in the axial section of the centrifugal compressor, the curved part (302) is arc-shaped, and the straight section part (304) is straight.

14. The diffuser for centrifugal compressors according to claim 13, wherein:

each of the first recess (512) and the second recess (514) further comprises an additional straight section (306), the curved section (302) being arranged between the straight section (304) and the additional straight section (306) and being connected to the straight section (304) and the additional straight section (306);

the additional straight section (306) is straight in axial section of the centrifugal compressor.

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