Self-circulating treatment casing of centrifugal compressor and centrifugal compressor

Abstract

The present application proposes a self-circulating treatment casing of a centrifugal compressor and a centrifugal compressor, comprising: a casing, the casing comprising an air inlet casing and an impeller casing, the air inlet casing enclosing an air inlet, the air inlet is gradually converging in the direction from upstream to downstream of the centrifugal compressor, and the air inlet casing is connected to the upstream side of the impeller casing; a plurality of impellers, the plurality of impellers are connected to the impeller hub at intervals along the circumference of the centrifugal compressor, the impeller hub can rotate relative to the casing, and the impeller casing surrounds the impellers; and a casing treatment groove, the casing treatment groove surrounds the casing, the casing treatment groove is connected to the casing, and the axial ends of the casing treatment groove respectively form openings on the air inlet casing and the impeller casing, so that the airflow in the casing can enter the casing treatment groove through the opening at one axial end of the casing treatment groove, and then return to the casing from the opening at the other axial end of the casing treatment groove.

Description

Technical Field

[0001] The present application relates to the field of compressors, and in particular to a self-circulating processing casing of a centrifugal compressor and a centrifugal compressor. Background Art

[0002] The compressor is a key component in the aero-engine field, urgently in need of technological breakthroughs. Centrifugal compressors occupy a crucial position in small and medium-sized aero-engines due to their advantages, including a high single-stage compression ratio, a wide stable operating range, a compact structure, and light weight. However, centrifugal compressors are technically challenging and require high investment. The internal flow of transonic centrifugal compressors is extremely complex, and the shock wave and vortex structures both lead to reduced stability margins and efficiency. The design requirements of high compression ratios, high loads, and high efficiency present numerous technical challenges for centrifugal compressor design.

[0003] Especially under the conditions of large flow (greater than 4kg / s) and high compression ratio (greater than or equal to 10), the blade load is higher than that in the environment of small flow and low compression ratio, resulting in complex interaction between shock waves and leakage vortices, making blockage and stall more likely to occur, so that the compressor can only support the aircraft engine to operate at full speed in the entire airspace within a narrow stable operating range.

[0004] Casing treatment, a simple, highly reliable compressor stabilization technology, has been widely used in axial and centrifugal compressor applications. Traditional casing treatment methods, such as casing vent holes and grooves, can generally increase the operating stability margin by approximately 10%.

[0005] At low flow rates and low compression ratios, centrifugal compressors have a high margin of stable operation, and generally do not require stabilization measures. However, as flow rates and compression ratios increase, the compressor gradually enters transonic operation, where the shock wave and head gap leakage vortex strength gradually increase, increasing compressor instability.

[0006] The self-circulating casing of a centrifugal compressor can effectively suppress unstable flow near the stall point, delay the occurrence of stall, and thus improve the stable operating margin of the compressor. However, for large flow rates and ultra-high compression ratios, there is still a lack of effective methods to further increase the margin on the basis of low efficiency loss.

[0007] The opening of a traditional centrifugal compressor's self-circulating casing is typically located after the impeller's throat. This is intended to draw airflow at both the blocked and stalled ends, thereby increasing the blocked flow rate and reducing the stall flow rate. However, for high-flow, ultra-high-compression-ratio centrifugal compressors, the impeller's work capacity is greater, and the pressure after the impeller's throat is higher than at the impeller's inlet, making traditional centrifugal compressor casings difficult to adapt to these high-flow, ultra-high-compression-ratio centrifugal compressors. Summary of the Invention

[0008] The present application aims to propose a self-circulating processing casing for a centrifugal compressor, which is suitable for centrifugal compressors with large flow and ultra-high compression ratio, and effectively expands the stable operating margin of the compressor.

[0009] The present application also proposes a centrifugal compressor comprising a self-circulating processing casing.

[0010] The embodiments of the present application provide a self-circulating processing casing for a centrifugal compressor, comprising:

[0011] A casing, the casing comprising an air inlet casing and an impeller casing, the air inlet casing enclosing an air inlet, the air inlet gradually converging in a direction from upstream to downstream of the centrifugal compressor, and the air inlet casing being connected to the upstream side of the impeller casing;

[0012] a plurality of impellers connected to an impeller hub at intervals along the circumference of the centrifugal compressor, wherein the impeller hub is rotatable relative to the casing, and the impeller casing surrounds the impellers; and

[0013] A casing processing groove surrounds the casing, the casing processing groove is connected to the casing, and the axial ends of the casing processing groove respectively form openings on the air inlet casing and the impeller casing, so that the airflow in the casing can enter the casing processing groove through the opening at one axial end of the casing processing groove, and then return to the casing from the opening at the other axial end of the casing processing groove.

[0014] In at least one possible embodiment, the casing processing groove is tapered in a direction from the impeller casing to the air inlet casing.

[0015] In at least one possible embodiment, the cross-section of the air inlet is annular, and when viewed from a meridian plane of the centrifugal compressor, the inner circumference and / or outer circumference of the air inlet includes a Bezier curve.

[0016] In at least one possible embodiment, an opening of the casing processing slot on the air inlet casing is located in an airflow stagnation area of ​​the air inlet.

[0017] In at least one possible embodiment, an opening of the casing processing groove on the impeller casing is located between two axial ends of the throat of the impeller.

[0018] In at least one possible embodiment, the casing processing groove includes an arc segment and a connecting segment, the arc segment is connected to the casing via the connecting segment, and the connecting segment is perpendicular to a connection position between the casing and the connecting segment.

[0019] In at least one possible embodiment, the connecting section extends along a straight line.

[0020] In at least one possible embodiment, the casing processing tank includes an inner wall and an outer wall, and the inner wall and the outer wall are connected by a rigid support structure.

[0021] An embodiment of the present application further provides a centrifugal compressor, which includes the self-circulating processing casing of the centrifugal compressor described in any one of the above technical solutions.

[0022] In at least one possible embodiment, the centrifugal compressor is used in an environment with a flow rate greater than 4 kilograms per second and a compression ratio greater than or equal to 10.

[0023] By adopting the above technical solution, the casing of the present application enables the centrifugal compressor to be suitable for large flow and ultra-high compression ratio, maintaining a relatively high stable operating margin. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a meridian flow passage of a centrifugal compressor according to an embodiment of the present application is shown.

[0025] Figure 2 Shown Figure 1 A partial enlarged view of .

[0026] Figure 3 A structural schematic diagram of a centrifugal compressor according to an embodiment of the present application is shown.

[0027] Figure 4 A schematic diagram of the internal structure of a centrifugal compressor according to an embodiment of the present application is shown.

[0028] Figure 5 A flow-efficiency curve of a centrifugal compressor according to an embodiment of the present application is shown.

[0029] Figure 6 A flow rate-compression ratio curve of a centrifugal compressor according to an embodiment of the present application is shown.

[0030] Description of Reference Numerals

[0031] 1 Intake

[0032] 2 Main blade 21 Main blade leading edge

[0033] 3 First splitter blade 31 First splitter blade leading edge

[0034] 4 Second splitter blade 41 Second splitter blade leading edge

[0035] 5. First diffuser

[0036] 6 Second diffuser

[0037] 7 Air outlet

[0038] 8 Casing 81 Inlet Casing 82 Impeller Casing

[0039] 9 Casing processing groove 91 arc segment 92 connecting segment

[0040] 10 Impeller hub

[0041] A Axial C Circumferential DETAILED DESCRIPTION

[0042] In order to more clearly illustrate the above-mentioned purposes, features and advantages of the present application, this section describes in detail the specific embodiments of the present application in conjunction with the accompanying drawings. In addition to the various embodiments described in this section, the present application can also be implemented in other different ways. Without violating the spirit of the present application, those skilled in the art can make corresponding improvements, deformations and substitutions. Therefore, the present application is not limited to the specific embodiments disclosed in this section. The scope of protection of this application shall be based on the claims.

[0043] like Figures 1 to 4 As shown, an embodiment of the present application proposes a centrifugal compressor, which includes an air inlet 1, an impeller, a first diffuser 5, a second diffuser 6, an air outlet 7 and a casing 8.

[0044] Figure 1 The left side is the upstream of the centrifugal compressor, and the right side is the downstream of the centrifugal compressor. The airflow flows from the upstream side to the downstream side.

[0045] The impeller includes main blades 2, first splitter blades 3, and second splitter blades 4. The main blades 2, first splitter blades 3, and second splitter blades 4 are connected to an impeller hub 10, which is rotatable relative to the casing 8. The main blades 2, first splitter blades 3, and second splitter blades 4 are all rotatably disposed within the casing 8.

[0046] like Figures 1 to 4 As shown, a plurality of main blades 2, first splitter blades 3, and second splitter blades 4 are provided at intervals along the circumferential direction C of the centrifugal compressor. In the circumferential direction C of the centrifugal compressor, the first splitter blade 3 can be provided between two adjacent main blades 2, and the second splitter blade 4 can be provided between adjacent first splitter blades 3 and main blades 2. Along the circumferential direction C of the centrifugal compressor, the main blades 2, the second splitter blades 4, the first splitter blades 3, and the second splitter blades 4 can be periodically arranged in this order.

[0047] The upstream end of the main blade 2 is the main blade leading edge 21, the upstream end of the first splitter blade 3 is the first splitter blade leading edge 31, and the upstream end of the second splitter blade 4 is the second splitter blade leading edge 41. The main blade leading edge 21 is located forward of the first splitter blade leading edge 31, and the first splitter blade leading edge 31 is located forward of the second splitter blade leading edge 41.

[0048] It can be understood that the specific blade profiles of the main blade 2, the first splitter blade 3 and the second splitter blade 4 can be designed based on the basic theory of turbomachinery so as to meet the performance requirements of the centrifugal compressor.

[0049] The first splitter blades 3 and the second splitter blades 4 rotate together with the main blades 2 to perform work, which can improve the work capacity of the centrifugal compressor and reduce the possibility of compressor blockage.

[0050] The casing 8 includes an air inlet casing 81 and an impeller casing 82. The leading edge 21 of the main blades and the upstream side of the impeller casing 82 can be flush. The impeller casing 82 can surround the main blades 2, the first splitter blades 3 and the second splitter blades 4. The air inlet casing 81 is connected to the upstream side of the impeller casing 82. The air inlet casing 81 can form an air inlet 1 extending along the axial direction A of the centrifugal compressor. In the direction from the upstream to the downstream of the centrifugal compressor, the air inlet 1 is gradually converging. Such an air inlet 1 can form an airflow stagnation zone in the area of ​​the air inlet 1 near the air inlet casing 81 to increase the static pressure of the airflow, balance the airflow in the casing treatment tank 9, and avoid excessive flow loss near the blockage end.

[0051] Furthermore, the cross section of the air intake duct 1 may be annular, the inner circumferential surface of the air intake duct 1 is the outer circumferential surface of the impeller hub 10 , and the outer circumferential surface of the air intake duct 1 is the inner circumferential surface of the air intake duct casing 81 .

[0052] Observed from a meridian plane of the centrifugal compressor, the profile slopes of the inlet casing 81 and the impeller hub 10 may both increase and then decrease, and the inner and / or outer circumferential surfaces of the inlet 1 may comprise a Bezier curve. In the direction from upstream to downstream of the centrifugal compressor, the portion of the impeller hub 10 upstream of the main blades 2 may have a diverging conical shape, while the inlet casing 81 may have a converging conical shape.

[0053] The profile slope of the air intake casing 81 can smoothly transition from 0 degrees to 55 degrees, and then to 0 degrees. The profile slope of the impeller hub 10 can smoothly transition from 0 degrees to 22 degrees, and then to 0 degrees. The radial dimension of the air intake 1 gradually decreases in the axial direction to the same radial dimension as the impeller leading edge 21.

[0054] The casing 8 is provided with a casing processing groove 9, which can surround the radial outer side of the casing 8. The axial ends of the casing processing groove 9 can form an annular opening around the entire circumference of the casing 8, so that the casing processing groove 9 is connected to the interior of the casing 8 to realize gas reflux.

[0055] The casing processing tank 9 includes an inner wall and an outer wall, wherein the inner wall is located radially inward of the outer wall, and the inner wall and the outer wall can form a channel. Figure 1 and Figure 2 As shown, when observing from the meridian plane of the centrifugal compressor, the inner wall and the outer wall are both arc-shaped, and the casing processing groove 9 can be an arc-shaped channel.

[0056] In the axial direction A of the centrifugal compressor, the two openings of the casing treatment groove 9 on the casing 8 are respectively located at the air inlet casing 81 and the impeller casing 82. The casing treatment groove 9 can form a gas reflux groove.

[0057] The opening width b of the casing processing groove 9 on the impeller casing 82 is o Greater than the opening width b of the casing processing slot 9 on the air inlet casing 81 i , so that the casing treatment groove 9 is tapered in the direction from the impeller casing 82 to the inlet casing 81. This allows gas to flow more easily from the impeller side to the inlet duct 1, thereby reducing the flow rate at the stall end, suppressing unstable flow near the stall point, delaying the onset of stall, and thus improving the stable operating margin of the compressor.

[0058] Furthermore, the upstream end of the casing treatment slot 9 opens on the intake duct casing 81 in the airflow stagnation area of ​​the intake duct 1. The downstream end of the casing treatment slot 9 opens on the impeller casing 82 between the two axial ends of the impeller throat. The impeller throat refers to the location of the smallest cross-section among multiple cross-sections between two adjacent main blades 21 and passing through the leading edge 21 of one of the main blades.

[0059] The opening of the casing processing groove 9 on the impeller casing 82 is located at the throat of the impeller. Under the conditions of large flow rate and high compression ratio, when the blade load is high, it can prevent excessive gas from flowing out through the casing processing groove 9, thereby reducing the flow loss near the blockage end.

[0060] Specifically, the opening of the casing treatment slot 9 on the air intake casing 81 is located at the 60% position on both the front and rear sides of the air intake casing 81. The position at the front side of the air intake casing 81 is 0%, and the position at the rear side of the air intake casing 81 is 100%. The opening of the casing treatment slot 9 on the impeller casing 82 is located 7.5% forward of the distance between the main blade leading edge 21 and the main blade trailing edge. The position at the main blade leading edge 21 is 0%, and the position at the main blade trailing edge is 100%. Of course, there may be slight positional differences, for example, the error amount is plus or minus 3%.

[0061] The inner wall and outer wall of the casing processing tank 9 can be connected by a rigid support structure. The rigid support structure can include a support rod. The support rod can be nested in the outer wall. The support rod can be arranged between the inner wall and the outer wall to support and fix the inner wall.

[0062] like Figure 1 and Figure 2 As shown, the casing processing groove 9 includes an arc segment 91 and a connecting segment 92 . The connecting segment 92 can be located at both ends of the arc segment 91 , and the connecting segment 92 is connected to the casing 8 .

[0063] The connection position of the connecting section 92 and the casing 8 is perpendicular. The gas flow near the casing is relatively complex. Under different working conditions, such as different speeds and flow rates, it is difficult to determine the direction of the gas flow near the casing. The gas may flow downstream or upstream. Making the connection position of the connecting section 92 and the casing 8 perpendicular can ensure that the opening of the casing treatment tank 9 is neither facing nor facing the air flow under different working conditions.

[0064] The connecting section of the casing treatment tank 9 can be a straight segment. This allows the connecting section 92 to intersect the casing 8 perpendicularly, regardless of the outer shape of the casing 8. This ensures a smooth transition between the arc section 91 of the casing treatment tank 9 and the casing 8. The length of the straight segment can be selected based on the specific shape of the casing, minimizing the length of the self-circulating treatment tank 9 along the axial direction A of the centrifugal compressor.

[0065] The first diffuser 5, the second diffuser 6 and the air outlet 7 can be sequentially arranged on the downstream side of the second splitter blade 4, with the second diffuser 6 being located radially outward of the first diffuser 5. The first diffuser 5 can be a tapered bladeless diffuser. The second diffuser 6 can be a wedge-shaped diffuser. Since the gas flow rate and pressure on the downstream side of the blade 4 are high, the use of a tapered bladeless diffuser contributes to the stable flow of the gas. Using a wedge-shaped diffuser on the downstream side of the tapered bladeless diffuser can further decelerate and diffuse the gas, giving the diffuser better diffusion capacity.

[0066] The gas outlet 7 can be bent 90 degrees as a whole, the upstream section of the gas outlet 7 can extend along the radial direction R, and the downstream section of the gas outlet 7 can extend along the axial direction A, so that the gas is discharged from the casing 8 along the axial direction A.

[0067] The centrifugal compressor of this application operates under conditions of high flow (greater than 4 kg / s) and high compression ratio (greater than or equal to 10), with a compression ratio far exceeding that of conventional compressors. The centrifugal compressor's stabilization effect is primarily reflected near the stall end, with a smaller impact near the blockage end. However, at speeds below the design, more low-speed fluid appears in the casing treatment tank, resulting in a loss of some flow near the blockage end.

[0068] During the operation of the centrifugal compressor, under conditions of low flow, i.e., near the stall end, the static pressure at the opening of the casing treatment tank 9 at the impeller casing 82 is higher than the static pressure at the opening of the casing treatment tank 9 at the inlet casing 81. The air flows from the impeller to the inlet 1 through the casing treatment tank 9, and after mixing with the intake air flow in the inlet 1, it is re-injected into the front opening of the impeller casing 82, making the flow at the compressor outlet smaller. In fact, the compressor can still operate stably at a smaller flow. Under operating conditions of large flow (greater than 4kg / s) and high compression ratio (greater than or equal to 10), i.e., near the blocked end, due to the high blade load, the static pressure at the opening of the impeller casing 82 is slightly greater than or equal to the static pressure at the opening of the inlet casing 81, and the air flow of the casing treatment tank 9 is lower, resulting in a smaller flow loss at the blocked end.

[0069] The aerodynamic performance of the centrifugal compressor of this application is analyzed using NUMECA software. First, NUMECA / Autogrid is used to divide the compressor, diffuser and self-circulating processing casing 8 into structured grids, and the wall grid satisfies Y+ less than 10. The SA turbulence model is used for calculation, and the fourth-order explicit Runge-Kutta time-marching method is used for time discretization, and the central difference format is used for spatial discretization. Given the total inlet temperature and total pressure under standard atmospheric conditions, the impeller wall is set as an adiabatic no-slip wall. In terms of outlet conditions, the small flow condition is the flow outlet, and the large flow condition is the pressure outlet. The multi-grid method and CPUbooster and other technologies are used to accelerate the calculation convergence.

[0070] ANSYS / Mechanical software was used to perform strength verification on the centrifugal impeller. TC11 titanium alloy for aviation was selected as the impeller material. Frictionless constraints were applied to both ends of the shaft, cylindrical constraints were applied to the inner surface of the shaft, and rotational angular velocity constraints were applied. The maximum stress was found to occur near the rim and blade tip, with a safety factor of 1.16.

[0071] Figure 5 The flow-efficiency curve of the centrifugal compressor of the present application is shown, wherein the horizontal axis represents the flow rate and the vertical axis represents the efficiency. Figure 6 The flow rate-compression ratio curve of the centrifugal compressor of the present application is shown, wherein the horizontal axis represents the flow rate and the vertical axis represents the compression ratio. Figure 5 and Figure 6 The n in represents the speed, Figure 5 and Figure 6 The working state of the centrifugal compressor under 5 kinds of speed (90%n to 110%n) is shown. The two ends of the curve represent the stall end and the blocked end. Figure 5 and Figure 6 100% n) compared to the original scheme without casing processing slot ( Figure 5 and Figure 6100% of the original design) has a wider operating range, that is, the speed range corresponding to the curve of this application on the horizontal axis is larger, supporting the full airspace and full speed operation of the aircraft engine. Especially at the stall end ( Figure 5 The centrifugal compressor of the present application has achieved a great improvement in surge margin, which can meet the requirements of modern aircraft engines for stable working margin and efficiency of the compressor.

[0072] Through performance comparison, it can be seen that the treatment casing of the centrifugal compressor using the present application is better than that without casing ( Figure 5 and Figure 6 In the original design), at the design speed ( Figure 5 and Figure 6 At 90% to 110% of the original speed (in the 90% to 110% range), the surge margin is significantly improved with minimal efficiency loss, meeting the stable operating margin and efficiency requirements of modern aircraft engines. Taking the highest efficiency point as the design point, the overall surge margin at various speeds is generally improved by more than 10% compared to the caseless design. Under certain operating conditions, the overall surge margin exceeds 15%, meeting practical engineering requirements.

[0073] It should be understood that at least some aspects or features of the above-mentioned embodiments, examples or examples may be appropriately combined.

[0074] It is understood that in this application, when the number of parts or components is not specifically limited, the number may be one or more, and the term "plurality" herein refers to two or more. Where the number of parts or components is shown in the drawings and / or described in the specification as a specific number, such as two, three, or four, the specific number is generally illustrative and not restrictive, and may be understood as a plurality, i.e., two or more. However, this does not mean that this application excludes the case of one.

[0075] In this application, unless otherwise clearly stated or limited, terms such as "install", "assemble", "connect", "connect", "couple", "link", "abut", "connect", "interconnect", "communicate", "conduct", "fix", "fasten", etc. should be understood in a broad sense, for example, they can be direct or indirect. For example, with respect to connection, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly stated or limited. For example, with respect to connectivity / conduction, it can be direct connectivity / conduction or indirect connectivity / conduction through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0076] In the present application, unless otherwise clearly stated or limited, a component provided on / installed on / located on / accommodated on / placed in, within, inside, etc. another component may be any of the following two situations: a part or most of the one component is located in the other component; and the one component is completely accommodated in the other component.

[0077] While the present application has been described in detail using the above-described embodiments, it will be apparent to those skilled in the art that the present application is not limited to the embodiments described in this specification. The present application can be modified and implemented as modified embodiments without departing from the subject matter and scope of the present application as defined by the claims. Therefore, the descriptions in this specification are for illustrative purposes only and do not have any limiting meaning with respect to the present application.

Claims

1. A self-circulating treatment casing for a centrifugal compressor, characterized in that: include: A casing (8), the casing (8) comprising an air inlet casing (81) and an impeller casing (82), the air inlet casing (81) enclosing an air inlet (1), the air inlet (1) being gradually convergent in a direction from upstream to downstream of the centrifugal compressor, the air inlet casing (81) being connected to the upstream side of the impeller casing (82); An impeller, wherein the plurality of blades of the impeller are connected to an impeller hub (10) at intervals along the circumferential direction (C) of the centrifugal compressor, the impeller hub (10) being rotatable relative to the casing (8), and the impeller casing (82) surrounding the impeller; as well as A casing processing groove (9), the casing processing groove (9) surrounds the casing (8), the casing processing groove (9) is connected to the casing (8), and the axial ends of the casing processing groove (9) respectively form openings on the air inlet casing (81) and the impeller casing (82), so that the airflow in the casing (8) can enter the casing processing groove (9) through the opening at one axial end of the casing processing groove (9), and then return to the casing (8) from the opening at the other axial end of the casing processing groove (9). In the direction from the impeller casing (82) to the air inlet casing (81), the casing processing groove (9) is tapered. The casing processing groove (9) comprises an arc segment (91) and a connecting segment (92), both ends of the arc segment (91) are connected to the casing (8) through the connecting segment (92), and the connecting segment (92) is perpendicular to the connection position between the casing (8) and the connecting segment (92). The connecting section (92) extends along a straight line.

2. The self-circulating treatment casing of a centrifugal compressor according to claim 1, characterized in that: The cross section of the air inlet (1) is annular, and when viewed from the meridian plane of the centrifugal compressor, the inner circumference and / or outer circumference of the air inlet (1) includes a Bezier curve.

3. The self-circulating treatment casing of a centrifugal compressor according to claim 1, characterized in that: The opening of the casing processing groove (9) on the air inlet casing (81) is located in the air flow stagnation area of ​​the air inlet (1).

4. The self-circulating treatment casing of a centrifugal compressor according to claim 1, characterized in that: The opening of the casing processing groove (9) on the impeller casing (82) is located between the two axial ends of the throat of the impeller, and the impeller includes a plurality of main blades (2) arranged at intervals along the circumferential direction (C), and the upstream end of the main blade (2) is the main blade leading edge (21). The throat of the impeller refers to the location of a cross section with the smallest area among multiple cross sections between two adjacent main blades (2) and passing through one of the leading edges (21) of the main blades.

5. The self-circulating treatment casing of a centrifugal compressor according to claim 1, characterized in that: The casing processing tank (9) comprises an inner wall and an outer wall, and the inner wall and the outer wall are connected by a rigid support structure.

6. A centrifugal compressor, characterized in that: The centrifugal compressor comprises the self-circulating processing casing of the centrifugal compressor according to any one of claims 1 to 5.

7. The centrifugal compressor according to claim 6, characterized in that: The centrifugal compressor is used in an environment where the flow rate is greater than 4 kilograms per second and the compression ratio is greater than or equal to 10.

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