Spiral axial flow type gas-liquid multiphase pump

Abstract

The invention provides a spiral axial flow type gas-liquid multiphase pump which comprises a rotatable impeller, a plurality of impeller blades are arranged on the outer ring of a hub of the impeller, and the spiral axial flow type gas-liquid multiphase pump is characterized in that at least one telescopic blade is further arranged on the outer ring of the hub of the impeller, a first straight moving mechanism is arranged on a hub web, and a second straight moving mechanism is arranged on the hub web. A telescopic rod of the first straight moving mechanism is connected with the telescopic blades and used for driving the telescopic blades to move in the radial direction. A groove matched with the telescopic blade in outline is formed in the outer ring of the hub, and a sealing structure is installed on the periphery of the groove. When the first straight moving mechanism is at the initial position, the upper surfaces of the telescopic blades are flush with the surface of the outer ring of the hub. Gas and liquid can be uniformly mixed, and the performance of the pump is improved.

Description

Technical Field

[0001] The present invention relates to the field of gas-liquid mixed transportation pumps, and particularly to a spiral axial-flow gas-liquid mixed transportation pump. Background Art

[0002] In today's energy field, oil-gas mixed transportation pumps play a crucial role in the process of oil and gas extraction and transportation. With the in-depth development of offshore and onshore oilfields, the fluids produced by many oil wells are mixtures of oil, gas, water and other impurities. As a key transportation device, the performance of the mixed transportation pump directly affects the economic benefits and efficiency of oilfield production. However, the incoming flow conditions faced by oil-gas mixed transportation pumps are extremely complex, that is, there is a pure liquid incoming flow with a very low gas content or even a gas content of zero, and there is also a gas-liquid mixture with a very high gas content (greater than 50%). Therefore, for such a situation with complex working conditions and unstable medium properties, more stringent requirements are put forward for the working condition adaptability of the mixed transportation pump.

[0003] Currently, axial-flow mixed transportation pumps face many problems that need to be solved urgently in actual operation. On the one hand, during the transportation of gas-liquid two-phase with a high gas content, due to the significant differences in density and velocity between the gas-liquid two-phase media in the impeller, the high-speed rotation of the impeller will cause different centrifugal forces for the two phases. The liquid phase accumulates in the upper-middle part of the impeller, while the gas phase accumulates in the hub area of the impeller, thereby further triggering the gas-liquid separation phenomenon. When the gas-liquid separation phenomenon is serious, it will not only lead to a decrease in the pressurization ability of the pump, but even cause the failure of the pump, greatly affecting the normal operation and service life of the pump. Inside the guide vane, the gas-liquid distribution is also uneven. The gas phase tends to be distributed in the rear section of the suction surface of the guide vane, and the liquid is distributed on the pressure surface, resulting in gas-liquid separation at a high gas content, causing a decrease in the working efficiency of the mixed transportation pump and even seriously deteriorating the overall hydraulic performance of the pump.

[0004] To sum up, the existing axial-flow mixed transportation pump technology has deficiencies in solving the gas-liquid separation problem and improving the transportation efficiency. There is an urgent need for an innovative design to optimize the impeller and guide vane structures, effectively improve the gas-liquid separation phenomenon, and then significantly improve the transportation efficiency of the axial-flow mixed transportation pump to meet the growing energy transportation needs. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a spiral axial-flow gas-liquid mixed transportation pump. By installing telescopic blades on the impeller, the blades retract during the transportation of low gas content working conditions to ensure the pressurization performance and transportation efficiency of the pump; during the transportation of high gas content working conditions, the telescopic blades extend to improve the gas-liquid separation phenomenon and increase the transportation efficiency, thereby improving the transportation performance of the pump under high gas content. By providing rotatable guide vanes on the guide vane, gaps are generated before and after the guide vane blades, so as to guide the liquid jet to impact the gas phase aggregation area in the rear section, realize uniform gas-liquid mixing, and improve the performance of the pump.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A screw axial-flow gas-liquid mixed transportation pump includes a rotatable impeller. A plurality of impeller blades are provided on the outer ring of the hub of the impeller. At least one telescopic blade is further provided on the outer ring of the hub of the impeller. A first linear mechanism is provided on the hub web. The telescopic rod of the first linear mechanism is connected to the telescopic blade for driving the telescopic blade to move radially.

[0008] Furthermore, a groove matching the contour of the telescopic blade is provided on the outer ring of the hub, and a sealing structure is installed around the groove; when the first linear mechanism is in the initial position, the upper surface of the telescopic blade is flush with the surface of the outer ring of the hub.

[0009] Furthermore, according to the gas content rate at the inlet of the gas-liquid mixed transportation pump, the first linear mechanism is controlled, thereby controlling the movement of the telescopic blade, and used to change the transportation performance under the gas-containing condition.

[0010] Furthermore, it further includes a guide vane. The guide vane includes a fixed guide vane hub outer ring, a rotating guide vane hub outer ring, a guide vane hub inner ring, and a guide vane web; the fixed guide vane hub outer ring is connected to the guide vane hub inner ring as a whole through the guide vane web, and a plurality of first blades are provided on the fixed guide vane hub outer ring; the rotating guide vane hub outer ring is installed on the outside of the fixed guide vane hub outer ring of the guide vane through a spigot, and a plurality of second blades are provided on the rotating guide vane hub outer ring; an adjusting device is installed on the guide vane web, and the rotating guide vane hub outer ring is driven to rotate through the adjusting device for changing the phase angle between the first blade and the second blade.

[0011] Furthermore, the adjusting device includes a second linear mechanism and a third linear mechanism. A forward wedge-shaped groove and a reverse wedge-shaped groove are respectively provided at different phase angles on the inner side of the rotating guide vane hub outer ring; the second linear mechanism and the third linear mechanism are respectively installed on the guide vane web at the phase angles corresponding to the forward wedge-shaped groove and the reverse wedge-shaped groove. A forward wedge block is installed on the stretching rod of the second linear mechanism, and the forward wedge block is inserted into the forward wedge-shaped groove through the second linear mechanism for making the rotating guide vane hub outer ring rotate forward; a reverse wedge block is installed on the stretching rod of the third linear mechanism, and the reverse wedge block is inserted into the reverse wedge-shaped groove through the third linear mechanism for making the rotating guide vane hub outer ring rotate backward.

[0012] Furthermore, only when the third linear mechanism makes the reverse wedge block insert into the reverse wedge-shaped groove, the blades of the rotating guide vane hub outer ring and the blades of the fixed guide vane hub outer ring form a complete guide vane shape;

[0013] Only when the second linear mechanism inserts the forward wedge block into the forward wedge-shaped groove, a gap is formed between the blades on the outer ring of the rotating guide vane hub and the blades on the outer ring of the fixed guide vane hub, so as to guide the liquid-phase jet to impact the gas-phase accumulation area in the rear section for uniform gas-liquid mixing.

[0014] Furthermore, a sensor is installed at the inlet of the gas-liquid mixed transportation pump to detect the gas content rate of the inlet medium; the controller controls the operation of the first linear mechanism, the second linear mechanism and the third linear mechanism according to the size of the gas content rate.

[0015] Furthermore, when the gas content rate of the inlet medium is less than 30%, the controller controls the third linear mechanism to insert the reverse wedge block into the reverse wedge-shaped groove, so that the blades on the outer ring of the rotating guide vane hub and the blades on the outer ring of the fixed guide vane hub form a complete guide vane shape;

[0016] When the gas content rate of the inlet medium is greater than or equal to 30%, the controller controls the first linear mechanism to radially extend the telescopic blades out of the outer ring of the hub, and controls the second linear mechanism to insert the forward wedge block into the forward wedge-shaped groove, so that the blades on the outer ring of the rotating guide vane hub and the blades on the outer ring of the fixed guide vane hub are staggered.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. For the screw axial flow gas-liquid mixed transportation pump described in the present invention, by installing telescopic blades on the impeller, the blades retract under the condition of transporting low gas content rate to ensure the boosting performance and transportation efficiency of the pump; when transporting high gas content rate, the telescopic blades extend to improve the gas-liquid separation phenomenon and increase the transportation efficiency, thereby improving the transportation performance of the pump under high gas content rate.

[0019] 2. For the screw axial flow gas-liquid mixed transportation pump described in the present invention, by providing rotatable guide vanes on the guide vanes, gaps are generated before and after the guide vane blades, so as to guide the liquid-phase jet to impact the gas-phase accumulation area in the rear section, realizing uniform gas-liquid mixing and improving the performance of the pump.

[0020] 3. The screw axial flow gas-liquid mixed transportation pump described in the present invention is applicable to transporting gas-liquid two-phase flows under different gas content rate conditions, and is free from disassembly. The linear mechanism can be controlled by the controller to realize the adjustment of the impeller and the guide vane. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. The following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained obviously without creative work based on these drawings.

[0022] Figure 1 It is the front view of the impeller described in the present invention.

[0023] Figure 2 This is the three-dimensional view of the impeller according to the present invention, where a is the three-dimensional view with the telescopic blade extended, and b is the three-dimensional view with the telescopic blade not extended.

[0024] Figure 3 This is the three-dimensional axonometric view of the impeller according to the present invention, where a is the three-dimensional axonometric view with the telescopic blade extended, and b is the three-dimensional axonometric view with the telescopic blade not extended.

[0025] Figure 4 This is the front view of the guide vane according to the present invention.

[0026] Figure 5 This is the three-dimensional view of the guide vane according to the present invention, where a is the three-dimensional view with the outer ring of the rotating guide vane hub not rotated, and b is the three-dimensional view after the outer ring of the rotating guide vane hub is rotated.

[0027] Figure 6 This is the sectional view of the outer ring of the rotating guide vane hub of the present invention when it is misaligned.

[0028] Figure 7 This is the structural schematic diagram of the impeller and the guide vane according to the present invention.

[0029] In the figure:

[0030] 1 - impeller; 1 - 1 - outer ring of the impeller hub; 1 - 2 - inner ring of the impeller hub; 1 - 3 - web of the impeller hub; 1 - 4 - impeller blade; 1 - 5 - telescopic blade; 1 - 6 - first telescopic rod; 1 - 7 - first electric device; 3 - guide vane; 3 - 1 - outer ring of the fixed guide vane hub; 3 - 2 - outer ring of the rotating guide vane hub; 3 - 3 - inner ring of the guide vane hub; 3 - 4 - web of the guide vane hub; 3 - 5 - second telescopic rod; 3 - 6 - second electric device; 3 - 7 - third telescopic rod; 3 - 8 - third electric device; 3 - 9 - forward wedge groove; 3 - 10 - reverse wedge groove. Detailed implementation manners

[0031] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation to the present invention.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0033] 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.

[0034] like Figure 1 and Figure 2 As shown, the spiral axial flow gas-liquid mixed delivery pump of the present invention comprises a rotatable impeller 1, the cross section of the impeller 1 is an I-shaped impeller, comprising an impeller hub outer ring 1-1, an impeller hub inner ring 1-2 and an impeller hub web 1-3; the impeller hub outer ring 1-1 and the impeller hub inner ring 1-2 are connected through the impeller hub web 1-3, and the impeller hub inner ring 1-2 is provided with a keyway, which is connected to the rotating shaft through a key connection. The impeller hub outer ring 1-1 is provided with a plurality of impeller blades 1-4, and the impeller hub outer ring 1-1 is also provided with at least one telescopic blade 1-5, and a first electric device 1-7 is provided on the impeller hub web 1-3, and a first telescopic rod 1-6 of the first electric device 1-7 is connected to the telescopic blade 1-5, and is used to drive the telescopic blade 1-5 to move radially.

[0035] like Figure 2 and Figure 3As shown, a groove matching the contour of the telescopic blade 1-5 is provided on the outer ring 1-1 of the impeller hub, and a sealing structure is installed around the groove; when the first electric device 1-7 is in the initial position, that is, the first telescopic rod 1-6 does not extend, the upper surface of the telescopic blade 1-5 is flush with the surface of the outer ring 1-1 of the impeller hub. According to the gas content rate at the inlet of the gas-liquid mixed transport pump, the first electric device 1-7 is controlled, thereby controlling the radial movement of the telescopic blade 1-5, which is used to change the transport performance under gas-containing conditions. When transporting under low gas content rate conditions, the telescopic blade 1-5 retracts to ensure the boosting performance and transport efficiency of the pump; when transporting under high gas content rate conditions, the telescopic blade 1-5 extends to improve the gas-liquid separation phenomenon and increase the transport efficiency, thereby improving the transport performance of the pump under high gas content rate.

[0036] As Figure 4 and Figure 5 As shown, the screw axial flow gas-liquid mixed transport pump further includes a guide vane 3. The cross-section of the guide vane 3 is also in an I shape. The guide vane 3 includes a fixed guide vane hub outer ring 3-1, a rotating guide vane hub outer ring 3-2, a guide vane hub inner ring 3-3, and a guide vane web 3-4; the fixed guide vane hub outer ring 3-1 is connected to the guide vane hub inner ring 3-3 through the guide vane web 3-4, and a number of first blades are provided on the fixed guide vane hub outer ring 3-1; the rotating guide vane hub outer ring 3-2 is installed on the outside of the fixed guide vane hub outer ring 3-1 of the guide vane 3 through a spigot, and a number of second blades are provided on the rotating guide vane hub outer ring 3-2; an adjusting device is installed on the guide vane web 3-4, and the rotating guide vane hub outer ring 3-2 is driven to rotate through the adjusting device, which is used to change the phase angle between the first blade and the second blade.

[0037] As Figure 5 and Figure 6 As shown, the adjusting device includes a second electric device 3-6 and a third electric device 3-8. Positive wedge-shaped grooves 3-9 and reverse wedge-shaped grooves 3-10 are respectively provided at different phase angles on the inner side of the rotating guide vane hub outer ring 3-2; the second electric device 3-6 and the third electric device 3-8 are respectively installed on the guide vane web 3-4 at the phase angles corresponding to the positive wedge-shaped grooves 3-9 and the reverse wedge-shaped grooves 3-10. A positive wedge block 3-9 is installed on the second telescopic rod 3-5 of the second electric device 3-6. The positive wedge block is inserted into the positive wedge-shaped groove 3-9 through the second electric device 3-6, which is used to make the rotating guide vane hub outer ring 3-2 rotate forward; a reverse wedge block is installed on the third telescopic rod 3-7 of the third electric device 3-8. The reverse wedge block is inserted into the reverse wedge-shaped groove 3-10 through the third electric device 3-8, which is used to make the rotating guide vane hub outer ring 3-2 rotate backward. Both the positive wedge block and the reverse wedge block are in a right triangle shape, but the installation directions are opposite.

[0038] As Figure 5As shown, only when the third electric device 3-8 inserts the reverse wedge block into the reverse wedge-shaped groove 3-10, the blades of the outer ring 3-2 of the rotating guide vane hub and the blades of the outer ring 3-1 of the fixed guide vane form a complete guide vane shape; only when the second electric device 3-6 inserts the forward wedge block into the forward wedge-shaped groove 3-9, a gap is formed between the blades of the outer ring 3-2 of the rotating guide vane hub and the blades of the outer ring 3-1 of the fixed guide vane hub, so as to guide the liquid-phase jet to impact the gas-phase accumulation area in the rear section, realizing uniform gas-liquid mixing and improving the performance of the pump.

[0039] A sensor is installed at the inlet of the gas-liquid mixed transportation pump to detect the gas content rate of the inlet medium; the controller controls the operation of the first electric device 1-7, the second electric device 3-6 and the third electric device 3-8 according to the size of the gas content rate. When the gas content rate of the inlet medium is less than 30%, the controller controls the third electric device 3-8 to insert the reverse wedge block into the reverse wedge-shaped groove 3-10, so that the blades of the outer ring 3-2 of the rotating guide vane hub and the blades of the outer ring 3-1 of the fixed guide vane form a complete guide vane shape; when the gas content rate of the inlet medium is greater than or equal to 30%, the controller controls the first linear mechanism to radially extend the telescopic blade 1-5 out of the outer ring 1-1 of the hub, and controls the second linear mechanism to insert the forward wedge block into the forward wedge-shaped groove 3-9, so that the blades of the outer ring 3-2 of the rotating guide vane hub and the blades of the outer ring 3-1 of the fixed guide vane hub are staggered.

[0040] As Figure 7 As shown, the screw axial-flow gas-liquid mixed transportation pump of the present invention simultaneously includes a telescopic blade 1-5 and an outer ring 3-2 of a rotating guide vane. When transporting a gas-liquid two-phase flow with a gas content rate less than 30%, the blades of the outer ring 3-2 of the rotating guide vane hub and the blades of the outer ring 3-1 of the fixed guide vane hub form a complete guide vane shape, and the telescopic blade 1-5 retracts. The mainstream enters from the inlet of the impeller, and the small blades of the impeller remain retracted. At this time, the impeller is the same as a normal impeller; the blades in the front and rear sections of the guide vane are closely connected and are the same as the blades of a normal guide vane. When transporting a gas-liquid two-phase flow with a gas content rate greater than or equal to 30%, the blades of the outer ring 3-2 of the rotating guide vane hub and the blades of the outer ring 3-1 of the fixed guide vane hub are staggered, and the telescopic blade 1-5 extends. Due to the presence of the telescopic blade 1-5, the phenomenon of gas-phase accumulation in the hub area is improved, thus ensuring the boosting performance and transportation efficiency of the pump; due to the formation of a gap between the front and rear sections of the guide vane blades, the liquid-phase jet is guided to impact the gas-phase accumulation area in the rear section, realizing uniform gas-liquid mixing and improving the performance of the pump.

[0041] It should be understood that although this specification is described according to each embodiment, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0042] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included within the protection scope of the present invention.

Claims

1. A screw axial flow gas-liquid mixed transportation pump, comprising a rotatable impeller (1), and a plurality of impeller blades (1-4) are arranged on the outer ring (1-1) of the impeller hub of the impeller, and it is characterized in that, At least one telescopic blade (1-5) is further provided on the outer ring of the impeller hub (1-1). A first linear movement mechanism is provided on the impeller hub web (1-3). The telescopic rod of the first linear movement mechanism is connected to the telescopic blade (1-5) and is used to drive the telescopic blade (1-5) to move radially.

2. The screw axial flow gas-liquid mixed transportation pump according to claim 1, wherein A groove matching the contour of the telescopic blade (1-5) is provided on the outer ring of the impeller hub (1-1), and a sealing structure is installed around the groove. When the first linear movement mechanism is in the initial position, the upper surface of the telescopic blade (1-5) is flush with the surface of the outer ring of the impeller hub (1-1).

3. The axial-flow screw gas-liquid mixed transportation pump according to claim 1, wherein According to the gas content rate at the inlet of the gas-liquid mixed transport pump, the first linear movement mechanism is controlled, so as to control the movement of the telescopic blade (1-5) and change the transport performance under the gas-containing working condition.

4. The axial helical gas-liquid mixed transportation pump according to claim 1, wherein It further includes a guide vane (3). The guide vane (3) includes a fixed guide vane hub outer ring (3-1), a rotating guide vane hub outer ring (3-2), a guide vane hub inner ring (3-3) and a guide vane web (3-4). The fixed guide vane hub outer ring (3-1) is connected to the guide vane inner ring (3-3) as a whole through the guide vane web (3-4). A number of first blades are provided on the fixed guide vane hub outer ring (3-1). The rotating guide vane hub outer ring (3-2) is installed on the outside of the fixed guide vane hub outer ring (3-1) of the guide vane (3) through a spigot. A number of second blades are provided on the rotating guide vane hub outer ring (3-2). An adjusting device is installed on the guide vane web (3-4). The rotating guide vane hub outer ring (3-2) is driven to rotate through the adjusting device to change the phase angle between the first blade and the second blade.

5. The screw axial flow gas-liquid mixed transportation pump according to claim 4, characterized in that, The adjusting device includes a second linear movement mechanism and a third linear movement mechanism. A forward wedge-shaped groove (3-9) and a reverse wedge-shaped groove (3-10) are respectively provided at different phase angles on the inner side of the rotating guide vane hub outer ring (3-2). The second linear movement mechanism and the third linear movement mechanism are respectively installed on the guide vane web (3-4) at the phase angles corresponding to the forward wedge-shaped groove (3-9) and the reverse wedge-shaped groove (3-10). A forward wedge block is installed on the telescopic rod of the second linear movement mechanism. The forward wedge block is inserted into the forward wedge-shaped groove (3-9) through the second linear movement mechanism to make the rotating guide vane hub outer ring (3-2) rotate forward. A reverse wedge block is installed on the telescopic rod of the third linear movement mechanism. The reverse wedge block is inserted into the reverse wedge-shaped groove (3-10) through the third linear movement mechanism to make the rotating guide vane hub outer ring (3-2) rotate reversely.

6. The screw axial-flow gas-liquid mixed transportation pump according to claim 5, characterized in that, Only when the third linear movement mechanism makes the reverse wedge block insert into the reverse wedge-shaped groove (3-10), the blades of the rotating guide vane hub outer ring (3-2) and the blades of the fixed guide vane outer ring (3-1) form a complete guide vane shape. Only when the second linear movement mechanism makes the forward wedge block insert into the forward wedge-shaped groove (3-9), a gap is formed between the blades of the rotating guide vane hub outer ring (3-2) and the blades of the fixed guide vane hub outer ring (3-1), so as to guide the liquid-phase jet to impact the gas-phase aggregation area in the rear section for uniform gas-liquid mixing.

7. The screw axial flow gas-liquid mixed transportation pump according to claim 5, characterized in that, Install a sensor at the inlet of the gas-liquid mixed transportation pump to detect the gas content rate of the inlet medium; the controller controls the operation of the first linear mechanism, the second linear mechanism, and the third linear mechanism according to the size of the gas content rate.

8. The screw axial flow gas-liquid mixed transportation pump according to claim 7, characterized in that When the gas content rate of the inlet medium is less than 30%, the controller controls the third linear mechanism to insert the reverse wedge block into the reverse wedge-shaped groove (3-10), so that the blades of the outer ring (3-2) of the rotating guide vane hub and the blades of the outer ring (3-1) of the fixed guide vane hub form a complete guide vane shape; When the gas content rate of the inlet medium is greater than or equal to 30%, the controller controls the first linear mechanism to radially extend the telescopic blade (1-5) out of the outer ring (1-1) of the hub, and controls the second linear mechanism to insert the forward wedge block into the forward wedge-shaped groove (3-9), so that the blades of the outer ring (3-2) of the rotating guide vane hub and the blades of the outer ring (3-1) of the fixed guide vane hub are staggered.

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