Underground axial-flow type gas compressor

Abstract

The invention belongs to the technical field of natural gas extraction, and particularly relates to an underground axial-flow type gas compressor. The underground axial-flow type gas compressor comprises multiple stages of stators which are coaxially fixed side by side in the axial direction, and an inlet and an outlet are formed in the two axial ends of each stator; the main shaft is coaxially and rotatably arranged in the stator; the rotors are coaxially and fixedly arranged on the main shaft in the axial direction, and the rotors correspond to the stators in a one-to-one mode. The device can be placed underground, and the productivity of a gas well is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas exploitation, and in particular, relates to an underground axial flow compressor. Background Art

[0002] In natural gas extraction, as the extraction time increases, the pressure of the gas reservoir at the bottom of the well gradually decreases, eventually leading to the cessation of production and abandonment of the gas well.

[0003] At present, in order to reduce the abandonment pressure of gas wells and improve the production capacity and recovery rate of natural gas wells, ground pressurization technology is mainly used for production.

[0004] However, there are still some shortcomings in the surface boosting technology. First, the surface boosting causes the loss of oil pipe pressure, which makes the remaining nearly 1 / 3 of the original natural gas in the reservoir unexploitable. Second, the surface boosting technology requires large-scale capital investment, and the production and operation costs are high. If the boosting system is placed at the bottom of the well, it can effectively reduce the oil pipe pressure loss, increase the production pressure difference, and further improve the gas well recovery rate.

[0005] The compressor used for ground pressure boosting is a centrifugal compressor, which is large in size and cannot meet the production conditions underground. In order to place the pressure boosting system at the bottom of the well, the compressor needs to be redesigned. The present invention proposes a downhole axial flow compressor to achieve downhole pressure boosting, further reduce the waste pressure of the gas well, and improve the gas well production capacity. Summary of the invention

[0006] In view of the technical problems mentioned above, the present invention aims to provide a downhole axial flow compressor, which can be placed underground to improve the productivity of the gas well.

[0007] According to the present invention, there is provided a downhole axial flow compressor, comprising:

[0008] A multi-stage stator is coaxially fixed side by side in the axial direction, and an inlet and an outlet are arranged at two axial ends of the stator;

[0009] A main shaft coaxially rotatably disposed within the stator;

[0010] And a multi-stage rotor is coaxially fixedly arranged on the main shaft along the axial direction, and each stage of the rotor corresponds to each stage of the stator.

[0011] In a preferred embodiment, the rotors at each stage and the main shaft are configured as an integrated structure, the stators at each stage are configured as an integrated structure, and both the rotors and the stators are configured as five stages.

[0012] In a preferred embodiment, the rotor includes a rotor hub and rotor blades, the rotor hub is connected to the main shaft, and the rotor blades are located on the outside of the rotor hub; the stator includes a stator hub and stator blades, the stator blades are located on the inside of the stator hub, and the stator blades are adapted to the rotor blades.

[0013] In a preferred embodiment, in a direction from the inlet to the outlet, the distance from the rotor hub to the stator hub of each stage gradually decreases.

[0014] In a preferred embodiment, in the direction from the inlet to the outlet, the inner diameter of the stator hub of each stage remains unchanged, and the outer diameter of the rotor hub of each stage increases gradually.

[0015] In a preferred embodiment, a first end cover and a second end cover are coaxially fixed at two ends of the stator, and the main shaft is coaxially rotatably connected with the first end cover and the second end cover via a bearing.

[0016] In a preferred embodiment, an inlet and an outlet are respectively arranged at positions of the first end cover and the second end cover corresponding to the rotor.

[0017] In a preferred embodiment, sealing elements are provided between the main shaft and both the first end cover and the second end cover.

[0018] In a preferred embodiment, a guide cone is coaxially fixedly provided on a side of the first end cover away from the rotor, the outer diameter of the guide cone gradually increases, and the inlet is located outside the range of the guide cone.

[0019] In a preferred embodiment, a cylinder is coaxially fixedly disposed on a side of the second end cover away from the rotor, and the outlet is located within the range of the cylinder.

[0020] Compared with the prior art, the advantages of the present application are as follows.

[0021] The present invention proposes a downhole axial flow compressor, which achieves the effect of placing the compressor at the bottom of the well, effectively reduces the pressure loss of the transmission pipeline, further increases the production pressure difference, and is beneficial to improving the production capacity and recovery rate of the gas well.

[0022] The present invention adopts an axial flow design structure, which can effectively reduce the outer diameter of the compressor while ensuring the natural gas compression ratio, and can be used in actual working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be described below with reference to the accompanying drawings.

[0024] Figure 1 A schematic diagram showing an embodiment of a downhole axial flow compressor according to the present invention is shown;

[0025] Figure 2 A schematic diagram of another embodiment of a downhole axial flow compressor according to the present invention is shown.

[0026] In the figure: 1. stator;

[0027] 11. stator hub; 111. stator hub inner ring; 112. stator hub outer ring;

[0028] 12. Stator blades; 13. Stator bolts;

[0029] 101. Entrance; 102. Exit;

[0030] 2. Spindle; 21. Shoulder; 22. Locking ring;

[0031] 3. Rotor;

[0032] 31. rotor hub; 311. rotor hub inner ring; 312. rotor hub outer ring;

[0033] 32. Rotor blades;

[0034] 4. first end cover; 41. guide cone;

[0035] 5. second end cover; 51. cylinder; 52. conical step;

[0036] 6. Sealing element; 61. Sealing mounting ring;

[0037] 7. Bearings;

[0038] 8. Shaft end cover; 81. Shaft end bolt;

[0039] 100. Downhole axial flow compressor.

[0040] In the present application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn according to the actual scale. DETAILED DESCRIPTION

[0041] The present invention will be described below with reference to the accompanying drawings.

[0042] It should be noted that the directional terms or qualifiers "left", "right", etc. used in this application are all relative to the referenced Figure 1 They are not intended to define the absolute positions of the components involved, but may vary depending on the specific circumstances.

[0043] Figure 1 The structure of the downhole axial flow compressor 100 according to the present invention is shown. Figure 1 As shown, the downhole axial flow compressor 100 includes a multi-stage stator 1 and a multi-stage rotor 3.

[0044] Embodiment 1:

[0045] like Figure 1 As shown, the multi-stage stator 1 is coaxially fixed in parallel in the axial direction, and an inlet 101 and an outlet 102 are arranged at both axial ends of the stator 1. The main shaft 2 is coaxially rotatably arranged in the stator 1, and the multi-stage rotor 3 is coaxially fixedly arranged on the main shaft 2 along the axial direction. Each stage of the rotor 3 corresponds to each stage of the stator 1 one by one, and the positions of the inlet 101 and the outlet 102 correspond to the position of the rotor 3.

[0046] In a preferred embodiment, the rotors 3 of each stage and the main shaft 2 are configured as an integrated structure, and the stators 1 of each stage are configured as an integrated structure. Figure 2 As shown. Through this arrangement, the thickness of the stator hub 11 of the stator 1 can be further reduced, so that the outer diameter of the rotor 3 can be made larger, the linear speed of the single-stage rotor is higher, the working capacity is stronger, and the single-stage compression ratio is higher, so that the rotor 3 and the stator 1 of the present invention can meet the use requirements when only five stages are set. There are many advantages to setting the rotor 3 and the stator 1 of the present invention in five stages, such as reducing the difficulty of matching each stage of the rotor 3 and each stage of the stator 1; reducing the difficulty of matching each stage with the next stage; reducing the manufacturing cost of the axial flow compressor; and the dynamics of the rotor 3 are easier to achieve.

[0047] When the rotors 3 at each level and the stators 1 at each level are respectively set as an integrated structure, in order to facilitate installation, the integrated structure formed by the stators 1 at each level is cut into two parts along the plane passing through the central axis thereof. During the installation process, the two parts can be interlocked with each other, so that the rotor 3 is set inside the stator 1.

[0048] In a specific embodiment, the rotor 3 includes a rotor hub 31 and rotor blades 32. Specifically, the rotor hub 31 is connected to the main shaft 2, and each stage of the rotor hub 31 is sequentially and axially fixedly sleeved on the main shaft 2. The rotor blades 32 are located outside the rotor hub 31.

[0049] It should be noted that the “outer side” in this article refers to the radial direction away from the central axis of the main shaft 2 , and correspondingly, the “inner side” refers to the radial direction close to the central axis of the main shaft 2 .

[0050] In a specific embodiment, the stator 1 includes a stator hub 11 and stator blades 12. The stator hubs 11 of each stage are arranged in sequence along the axial direction, and the stator blades 12 are located inside the stator hub 11, and the stator blades 12 are matched with the rotor blades 32.

[0051] During operation, the main shaft 2 is driven by a driver (not shown in the figure). The main shaft 2 drives the rotor 3 to rotate relative to the stator 1 during the rotation. The rotor blades 32 promote the flow of fluid during the rotation, thereby converting the kinetic energy of the rotor blades 32 into fluid kinetic energy. The fluid then enters the stator blades 12, and the kinetic energy of the fluid is converted into pressure potential energy, thereby achieving gas pressurization.

[0052] In a preferred embodiment, the combination Figure 1 As shown, from the inlet 101 to the outlet 102 , the distance from the rotor hub 31 of each stage to the stator hub 11 gradually decreases.

[0053] Specifically, from the inlet 101 to the outlet 102, the inner diameter of each stage of the stator hub 11 and the outer diameter of each stage of the rotor blades 32 remain unchanged, and the inner diameter of each stage of the rotor blades 32 and the outer diameter of the rotor hub 31 gradually increase, so that the distance from each stage of the rotor hub 31 to the stator hub 11 is gradually reduced, and gas compression is further achieved. This design of equal outer diameters of the rotor blades 32 is suitable for situations where the outer diameter size is limited, and can further reduce the overall diameter of the downhole axial flow compressor. In this embodiment, the inner diameter of the rotor blades 32 is 25.4mm to 27.2mm, that is, the outer diameter of the rotor hub 31 is 25.4mm to 27.2mm. The outer diameter of the rotor blades 32 at each stage does not exceed 35mm.

[0054] In addition to the above-mentioned equal outer diameter design of the rotor blades 32, the rotor blades 32 can also adopt an equal inner diameter design and an equal mid-diameter design, which can also gradually reduce the distance from the rotor hub 31 to the stator hub 11 at each stage, further realizing gas compression. Among them, the equal inner diameter setting means that the inner diameters of the rotor blades 32 at each stage are equal, and the outer diameters of the rotor blades 32 at each stage are gradually reduced; the equal mid-diameter setting means that the mid-diameters of the rotor blades 32 at each stage are equal, and the inner diameters of the rotor blades 32 at each stage are gradually increased, while the outer diameters of the rotor blades 32 at each stage are gradually reduced.

[0055] According to the present invention, on the basis of satisfying the use conditions, in order to further reduce the volume of the underground axial flow compressor 100, the blade inlet angle of the rotor blade 32 and the stator blade 12 is set to a range of -85° to -89°, and the blade outlet angle is set to a range of 85° to 89°. The blade inlet angle and the blade outlet angle are special terms in the field of axial flow compressor design, and are the angles between the leading edge tangent and the trailing edge tangent of the mid-arc line and the compressor axis. From the inlet 101 to the outlet 102, the rotors 3 and stators 1 are named as the first stage to the fifth stage in sequence. The installation angle of the rotor blades 32 of the first stage rotor 3 is 35° to 47°, and the installation angle of the stator blades 12 of the first stage stator 1 is 40° to 45°; the installation angle of the rotor blades 32 of the second stage rotor 3 is 35° to 47°, and the installation angle of the stator blades 12 of the second stage stator 1 is 38° to 43°; the installation angle of the rotor blades 32 of the second stage rotor 3 is 35° to 47°, and the installation angle of the stator blades 12 of the second stage stator 1 is 38° to 43°; the installation angle of the rotor blades 32 of the third stage rotor 3 is 35° to 47°, and the installation angle of the stator blades 12 of the second stage stator 1 is 38° to 43°; the installation angle of the rotor blades 32 of the second ... The installation angle of the rotor blades 32 is 35°~47°, and the installation angle of the stator blades 12 of the third-stage stator 1 is 35°~42°; the installation angle of the rotor blades 32 of the fourth-stage rotor 3 is 35°~47°, and the installation angle of the stator blades 12 of the fourth-stage stator 1 is 30°~38°; the installation angle of the rotor blades 32 of the fifth-stage rotor 3 is 35°~47°, and the installation angle of the stator blades 12 of the fifth-stage stator 1 is 25°~35°.

[0056] According to the present invention, a first end cover 4 and a second end cover 5 are coaxially fixed to both ends of the stator 1, and the main shaft 2 is coaxially rotatably connected to the first end cover 4 and the second end cover 5 via a bearing.

[0057] An inlet 101 and an outlet 102 are respectively arranged at the positions of the first end cover 4 and the second end cover 5 corresponding to the rotor 3. Preferably, a plurality of inlets 101 are evenly distributed along the circumferential direction of the first end cover 4, and a plurality of outlets 102 are evenly distributed along the circumferential direction of the second end cover 5. The positions where the inlets 101 and the outlets 102 are distributed correspond to the positions of the rotor blades 32 of the rotor 3, that is, the radius of the circle enclosed by each inlet 101 and each outlet 102 is within the distance range from the rotor blade 32 to the central axis of the main shaft 2, or in other words, the axial projection of each inlet 101 and each outlet 102 is within the range of the axial projection of the rotor blade 32.

[0058] A guide cone 41 is coaxially fixedly disposed on one side of the first end cover 4 away from the rotor 3. In this embodiment, the guide cone 41 is configured to be conical, and the outer diameter of the guide cone 41 gradually decreases along the direction of fluid flow. Figure 1 As shown, the outer diameter of the guide cone 41 increases gradually from left to right. The inlet 101 is located outside the range of the guide cone 41, that is, the outer diameter of the left end of the guide cone 41 is smaller than the size of the circle where each inlet 101 is located.

[0059] In another embodiment, Figure 2As shown, the guide cone 41 is set to be a semi-ellipsoidal shape, and the outer diameter of the guide cone 41 gradually increases along the direction of fluid flow. Figure 2 In the figure, the outer diameter of the guide cone 41 gradually decreases from left to right. Similarly, the inlet 101 is located outside the range of the guide cone 41, that is, the outer diameter of the left end of the guide cone 41 is smaller than the size of the circle where each inlet 101 is located.

[0060] The guide cone 41 can provide guidance for the gas flow and straighten the gas flow.

[0061] A cylinder 51 is coaxially fixedly arranged on one side of the second end cover 5 away from the rotor 3, and the outlet 102 is located within the range of the cylinder 51. The outer diameter of the cylinder 51 is equal to the outer diameter of the stator 1, and a conical step 52 is arranged on the inner wall of the cylinder 51. The arrangement of the conical step 52 makes the inner diameter of the left part of the cylinder 51 smaller than the inner diameter of the right part of the cylinder 51.

[0062] Seals 6 are provided between the main shaft 2 and the first end cover 4 and the second end cover 5 .

[0063] Embodiment 2:

[0064] In this embodiment, each stator 1 and each rotor 3 are designed as split type. Figure 1 The remaining structures are the same as those in the above embodiment.

[0065] The rightmost end of the main shaft 2 is connected to a coupling (not shown in the figure), and the coupling is driven by a driver to transmit the rotational power to the main shaft 2.

[0066] The rotor 3 can select different stages according to the needs. The rotor 3 is composed of a rotor blade 32 and a rotor hub 31, and is formed by an integrated process. A split design is adopted between each stage of the rotor 3, and the multi-stage rotor 3 is sequentially inserted into the main shaft 2 and fixed by the shoulder 21 and the locking ring 22 of the main shaft 2. In this embodiment, the multi-stage rotor 3 is sequentially inserted into the main shaft 2 from left to right until the rotor 3 at the rightmost end abuts the shoulder 21. After all the rotors 3 are inserted into the main shaft 2, the locking ring 22 is inserted into the main shaft 2 so that the locking ring 22 abuts against the rotor 3 at the leftmost end.

[0067] In a preferred embodiment, the rotor hub 31 includes a rotor hub inner ring 311 and a rotor hub outer ring 312, which are staggered in the axial direction, and the rotor hub outer ring 312 is located outside the rotor hub inner ring 311. At the same time, the rotor hub inner rings 311 of adjacent rotor hubs 31 are axially abutted, the rotor hub outer rings 312 of adjacent rotor hubs 31 are axially abutted, and the rotor hub inner rings 311 and the rotor hub outer rings 312 of adjacent rotor hubs 31 are partially in radial contact. The rotor hub outer rings 312 of the rotor hubs 31 at the left and right ends are in radial contact with the lock ring 22 and the shaft shoulder 21 respectively.

[0068] The structure of the stator hub 11 is similar to that of the rotor hub 31 , and each stator hub 11 also includes two parts that are axially offset from each other.

[0069] Specifically, the stator hub 11 includes a stator hub inner ring 111 and a stator hub outer ring 112. The stator hub outer ring 112 is located outside the stator hub inner ring 111, and the stator hub inner ring 111 and the stator hub outer ring 112 are axially staggered. The stator hub inner rings 111 of two adjacent stator hubs 11 are axially abutted against each other, the stator hub outer rings 112 of two adjacent stator hubs 11 are axially abutted against each other, and the stator hub inner rings 111 and the stator hub outer rings 112 of two adjacent stator hubs 11 are radially in contact with each other. The stator hub inner rings 111 or the stator hub outer rings 112 of the two stator hubs 11 located at the left and right ends are in radial contact with the first end cover 4 and the second end cover 5, respectively.

[0070] The stator 1 can also be selected in different stages according to the needs. The stator 1 is composed of stator blades 12 and stator hub 11, and is formed by one-piece processing. A split structure is adopted between each stage of the stator 1, and the multi-stage stator 1 is axially connected in sequence. The second end cover 5 and the first end cover 4 are fixedly arranged at the left and right ends of the stator 1, respectively. The stator bolts 13 penetrate the first end cover 4, each stage of the stator 1 and the second end cover 5 from the right end to the left in sequence, so that the multi-stage stator 1 is fixed to the first end cover 4 and the second end cover 5. The stator hub 11 is used to support the stator blades 12 and fix them relative to the first end cover 4 and the second end cover 5.

[0071] The multi-stage rotor 3 rotates together with the main shaft 2. The rotor hub 31 of the rotor 3 is used to support the rotor blades 32 and connect them to the main shaft 2. Starting from the rightmost rotor 3 to the left, the outer diameter of the rotor hub 31 of each stage of the rotor 3 increases successively to achieve gas compression. The rotor blades 32 of the rotor 3 adopt a three-dimensional curved surface structure. Through the rotation of the rotor blades 32, the kinetic energy is converted into pressure potential energy to achieve gas supercharging.

[0072] It is easy to understand that the three-dimensional curved surface structure of the rotor blade 32 is a prior art, and the specific parameters of the three-dimensional curved surface are not the technical points of the present invention and will not be described in detail here.

[0073] The rotor 3 and the stator 1 are both installed in stages, which is convenient for processing, assembly, later maintenance and replacement, and achieves better economic benefits.

[0074] A sealing member 6 is provided between the shaft shoulder 21 and the first end cover 4 , and between the locking ring 22 and the second end cover 5 .

[0075] Specifically, the first end cover 4 and the second end cover 5 have the same structure for setting the seal 6, and the first end cover 4 is taken as an example for description. A seal mounting ring 61 is coaxially arranged on the left side of the first end cover 4, and the inner diameter of the seal mounting ring 61 is greater than the outer diameter of the shaft shoulder 21, and the inner diameter of the seal mounting ring 61 is equal to the outer diameter of the seal 6. The axial ends of the seal 6 are respectively in contact with the shaft shoulder 21 and the first end cover 4.

[0076] A bearing 7 is arranged between the main shaft 2 and the first end cover 4, and the bearing 7 is connected to the seal 6, which can isolate the bearing 7 from the shaft shoulder 21. A sealing medium (such as sealing grease) is added into the gap between the sealing mounting ring 61 and the shaft shoulder 21 to achieve dynamic sealing, prevent impurities in the gas from entering the bearing 7, and ensure the normal operation of the bearing 7.

[0077] According to the present invention, the seal 6 can be configured as a variety of dynamic sealing structures, and can be configured as a labyrinth seal.

[0078] The labyrinth seal is a seal in which a number of annular sealing teeth are arranged in sequence around the main shaft 2, and a series of intercepting gaps and expansion cavities are formed between the teeth. When the sealed medium passes through the gaps in the tortuous labyrinth, a throttling effect will be produced, thereby achieving the purpose of preventing leakage.

[0079] The seal in this embodiment can be set to a simple straight-through type, a stepped type, a staggered type, a mirror-image maze type, a compound straight-through type, a helical-tooth stepped type, a honeycomb maze type, a wear-bearing seal type, etc.

[0080] A shaft end cover 8 is fixedly arranged at a section of the bearing 7 away from the seal 6. That is, a shaft end cover 8 is respectively arranged at the left end of the second end cover 5 and the right end of the first end cover 4. The shaft end cover 8 is axially abutted against the bearing 7, and the two shaft end covers 8 are respectively fixedly connected to the first end cover 4 and the second end cover 5 by shaft end bolts 81.

[0081] It should be noted that the main difference between Example 1 and Example 2 is that the stators 1 at each level and the rotors 3 at each level in Example 1 respectively adopt an integrated structure, while the stators 1 at each level and the rotors 3 at each level in Example 2 respectively adopt a split structure, and the remaining technical features can be freely combined according to actual conditions.

[0082] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0083] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0084] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0085] Finally, it should be noted that the above is only a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A downhole axial flow compressor, comprising: A multi-stage stator (1) is coaxially fixed side by side in the axial direction, and an inlet (101) and an outlet (102) are provided at two axial ends of the stator (1); A main shaft (2) coaxially rotatably arranged inside the stator (1); And a multi-stage rotor (3) is coaxially fixedly arranged on the main shaft (2) along the axial direction, and each stage of the rotor (3) corresponds to each stage of the stator (1) one by one.

2. The downhole axial flow compressor according to claim 1, characterized in that: The rotors (3) at each stage and the main shaft (2) are arranged as an integrated structure, the stators (1) at each stage are arranged as an integrated structure, and both the rotors (3) and the stators (1) are arranged as five stages.

3. The downhole axial flow compressor according to claim 1 or 2, characterized in that: The rotor (3) comprises a rotor hub (31) and rotor blades (32), wherein the rotor hub (31) is connected to the main shaft (2), and the rotor blades (32) are located on the outside of the rotor hub (31); the stator (1) comprises a stator hub (11) and stator blades (12), wherein the stator blades (12) are located on the inside of the stator hub (11), and the stator blades (12) are matched with the rotor blades (32).

4. The downhole axial flow compressor according to claim 3, characterized in that: In the direction from the inlet (101) to the outlet (102), the distance from the rotor hub (31) to the stator hub (11) of each stage gradually decreases.

5. The downhole axial flow compressor according to claim 4, characterized in that: In the direction from the inlet (101) to the outlet (102), the inner diameter of each stage of the stator hub (11) remains unchanged, and the outer diameter of each stage of the rotor hub (31) gradually increases.

6. The downhole axial flow compressor according to claim 1 or 2, characterized in that: A first end cover (4) and a second end cover (5) are coaxially fixed at the two ends of the stator (1), and the main shaft (2) is coaxially rotatably connected to the first end cover (4) and the second end cover (5) via a bearing.

7. The downhole axial flow compressor according to claim 6, characterized in that: An inlet (101) and an outlet (102) are respectively arranged at positions of the first end cover (4) and the second end cover (5) corresponding to the rotor (3).

8. The downhole axial flow compressor according to claim 7, characterized in that: A sealing element (6) is provided between the main shaft (2) and the first end cover (4) and the second end cover (5).

9. The downhole axial flow compressor according to claim 7, characterized in that: A guide cone (41) is coaxially fixedly arranged on a side of the first end cover (4) away from the rotor (3), the outer diameter of the guide cone (41) gradually increases, and the inlet (101) is located outside the range of the guide cone (41).

10. The downhole axial flow compressor according to claim 7, characterized in that: A cylinder (51) is coaxially fixedly arranged on a side of the second end cover (5) away from the rotor (3), and the outlet (102) is located within the range of the cylinder (51).

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