Extremely-low-specific-speed centrifugal hydrogen compressor closed impeller and design method thereof

Abstract

The invention provides a closed impeller of an extremely-low-specific-speed centrifugal hydrogen compressor and a design method of the closed impeller. The impeller comprises a hub and a wheel cover which are mechanically connected after being machined in a split mode. The wheel cover is provided with a runner, the wheel cover surface is a curved surface, a non-runner area is provided with a weight reduction structure, and reinforcing ribs are reserved; the hub is provided with a segmented annular spigot which is matched with the weight reducing part of the wheel cover to achieve torque transmission and positioning, and the hub and the weight reducing part are provided with protruding sections for sealing. According to the design method, the flow channels are designed by amplifying flow, the number of the flow channels is reduced according to the same multiple, and split machining and assembling are combined. The flow channel height is increased, the machining difficulty and deviation are reduced, the dynamic characteristics and structural rigidity of the rotor are optimized, the operation stability is improved, manufacturing feasibility and flowing performance are both considered, and the rotor is suitable for an extremely-low-specific-speed hydrogen compression scene.

Description

Technical Field

[0001] This invention relates to the field of centrifugal compressor technology, and in particular to a closed impeller for an ultra-low specific speed centrifugal hydrogen compressor and its design method. Background Technology

[0002] Hydrogen, as an important industrial raw material and clean energy source, is widely used in chemical, new energy, and other fields. Centrifugal compressors, due to their compact structure, excellent continuous flow characteristics, and high operational reliability, have become an important choice for hydrogen compression equipment. Compared with conventional gases, hydrogen has a low molecular weight and low density, making it difficult to compress. In some chemical processes, hydrogen recirculation compressors exhibit extremely low specific speed (Ns) characteristics due to the high inlet pressure and low flow rate. When using conventional centrifugal compressor aerodynamic design methods, the resulting impeller flow channel height is extremely small (less than 4 mm). To avoid tip leakage losses and achieve the required pressure ratio, a closed impeller is usually required.

[0003] However, conventional manufacturing methods struggle to meet the geometric tolerance requirements of such impellers: CNC machining centers cannot machine extremely narrow flow channels, while integral casting creates casting fillets at the blade root and tip, resulting in significant dimensional deviations. Currently, for closed impellers with excessively small flow channel heights, although some technologies propose modular machining followed by assembly, these methods are primarily applicable to centrifugal liquid pumps and involve machining conventional blades, failing to address the impeller structure issues of centrifugal compressors with even smaller flow rates and extremely low specific speeds. Therefore, balancing manufacturing feasibility with flow performance while meeting the pressure ratio and flow rate requirements of hydrogen-related processes has become a key challenge in the design of current hydrogen centrifugal compressors. Summary of the Invention

[0004] The purpose of this invention is to provide a closed impeller for an ultra-low specific speed centrifugal hydrogen compressor and its design method, aiming to solve the problem that the existing ultra-low specific speed centrifugal hydrogen compressors have high manufacturing difficulty and significant geometric deviations due to the small impeller flow channel height, which in turn affects the compressor performance.

[0005] According to one objective of the present invention, a closed impeller for an ultra-low specific speed centrifugal hydrogen compressor is provided, comprising a hub and a cover, wherein the hub and the cover are separately machined and then mechanically connected to form a closed impeller; the cover has a flow channel, and the cover surface of the cover is curved; the non-flow channel area of ​​the cover has a weight-reducing structure and retains reinforcing ribs; the hub has a segmented annular stop, and the weight-reducing structure of the cover cooperates with the segmented annular stop to realize torque transmission and center positioning between the hub and the cover; both the hub and the cover have protruding sections for installing a sealing mechanism.

[0006] Furthermore, the mechanical connection between the wheel hub and the wheel cover is a bolt connection. The wheel cover is provided with a screw hole, and the wheel hub is provided with a countersunk hole. The bolt passes through the countersunk hole and is threadedly connected to the screw hole.

[0007] Furthermore, the weight-reducing structure is a cavity or lightweight hole formed by milling, and the reinforcing rib is a straight structure.

[0008] Furthermore, the hub is provided with a shaft hole, a tie rod hole, and a tie rod nut mounting hole, which are used to install the motor shaft, tie rod, and tie rod nut, respectively.

[0009] Furthermore, a fairing is provided on the hub, the fairing is connected to the hub by threads, and the fairing is used to cover the tie rod nut.

[0010] Furthermore, the number of flow channels is 2-6.

[0011] Furthermore, the protruding section on the wheel hub is the wheel hub protruding section, and the protruding section on the wheel cover is the wheel cover protruding section.

[0012] Furthermore, the wheel cover surface is curved, and the flow channel is opened on the side of the wheel cover facing the wheel hub.

[0013] According to another objective of the present invention, the present invention provides a design method for the closed impeller of the above-mentioned ultra-low specific speed centrifugal hydrogen compressor, comprising the following steps: S1. Adopt the conventional centrifugal compressor pneumatic design method, design according to the multiplied flow rate, determine the flow channel shape, and ensure the flow channel height; S2. Reduce the number of flow channels by the same factor as the flow amplification factor to meet the actual flow requirements; S3. The flow channel is designed on the wheel cover, and the wheel cover surface is designed as a curved surface; the non-flow channel area of ​​the wheel cover is designed to reduce weight while retaining the reinforcing ribs; a segmented annular stop is set on the wheel hub to cooperate with the weight-reducing part of the wheel cover to achieve torque transmission and center positioning. S4. After the hub and wheel cover are processed separately, they are assembled by mechanical connection to form a closed impeller.

[0014] Furthermore, the flow rate amplification factor is 2-5 times, and the designed flow channel height is not less than 4mm; the mechanical connection is a bolt connection.

[0015] This invention solves the manufacturing challenges of centrifugal hydrogen compressors with extremely low specific speeds due to the insufficient height of the impeller flow channels. By separately machining and reassembling the hub and cover, manufacturing difficulty and geometric deviations are reduced. The design employs a "reduced flow channel number after increasing flow rate" approach to achieve high and low flow channel characteristics, increasing the flow channel height for easier machining. The weight-reducing structure and reinforcing ribs synergistically optimize rotor dynamics and structural rigidity, while the annular stop ensures accurate torque transmission and positioning, improving operational stability. Balancing manufacturing feasibility and flow performance, this invention has practical engineering applications. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall structure of the closed impeller in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the wheel hub and wheel cover in an embodiment of the present invention; Figure 3 This is another structural schematic diagram of the wheel hub and wheel cover in an embodiment of the present invention; Figure 4 This is a schematic diagram of the impeller cover structure in an embodiment of the present invention; Figure 5 This is a schematic diagram of the wheel hub in an embodiment of the present invention.

[0018] In the diagram: 1. Weight reduction structure; 2. Screw hole; 3. Bolt; 4. Internal thread; 5. Fairing; 6. Tie rod nut mounting hole; 7. Tie rod hole; 8. Shaft hole; 9. Reinforcing rib; 10. Hub; 11. Flow channel; 12. Hub protrusion section; 13. Segmented annular stop; 14. Wheel cover; 15. Wheel cover protrusion section. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Example 1 like Figures 1-5 As shown, a closed impeller for an ultra-low specific speed centrifugal hydrogen compressor includes a hub 10 and a cover 14. The hub 10 and the cover 14 are machined separately and then mechanically connected to form a closed impeller. The wheel cover 14 is provided with flow channels, and the wheel cover surface of the wheel cover 14 is curved; the non-flow channel area of ​​the wheel cover 14 is provided with a weight reduction structure 1 and retains a reinforcing rib 9; The wheel hub 10 is provided with a segmented annular stop 13, and the weight reduction part of the wheel cover 14 cooperates with the segmented annular stop 13 to realize the torque transmission and center positioning between the wheel hub 10 and the wheel cover 14. Both the hub 10 and the cover 14 have protruding sections for installing sealing mechanisms.

[0023] This invention also provides a design method for the closed impeller of the above-mentioned ultra-low specific speed centrifugal hydrogen compressor, comprising the following steps: The conventional centrifugal compressor pneumatic design method is adopted, and the flow channel shape is determined according to the multiplied flow rate to ensure the flow channel height; The number of flow channels is reduced by the same factor as the flow amplification factor to meet the actual flow requirements and achieve high and low flow channel characteristics. The flow channel is designed on the wheel cover, and the surface of the wheel cover is designed as a curved surface; The non-flow channel area of ​​the wheel cover is designed to reduce weight, while retaining reinforcing ribs; An annular stop is set on the wheel hub, which cooperates with the weight reduction part of the wheel cover to achieve torque transmission and center positioning; The hub and cover are machined separately and then assembled by mechanical connection to form a closed impeller.

[0024] Example 2 like Figure 1-5 As shown, the structure of this embodiment is basically the same as that of Embodiment 1. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor in this embodiment includes a hub 10 and a cover 14. The hub 10 and the cover 14 are processed separately and then mechanically connected to form a closed impeller. Specifically, the mechanical connection between the hub 10 and the cover 14 is achieved by using several bolts 3. The edge of the cover 14 is provided with several screw holes 2, and several countersunk holes are correspondingly provided on the hub 10. The bolts 3 pass through the countersunk holes and are threaded into the screw holes 2 to achieve mechanical fixation of the hub 10 and the cover 14.

[0025] The wheel cover 14 has a curved surface. The wheel cover 14 has 2-6 flow channels 11. The non-flow channel areas of the wheel cover 14 have a weight-reducing structure 1, which is a milled cavity or lightweight hole. The wheel cover 14 retains reinforcing ribs 9, which are straight lines.

[0026] The wheel hub 10 is provided with a segmented annular stop 13. The weight reduction structure 1 of the wheel cover 14 cooperates with the segmented annular stop 13 to realize the torque transmission and center positioning between the wheel hub 10 and the wheel cover 14.

[0027] The hub 10 is also provided with a hub protrusion section 12, and the wheel cover 14 is provided with a wheel cover protrusion section 15. The hub protrusion section 12 and the wheel cover protrusion section 15 are used to install a sealing mechanism.

[0028] The hub 10 has a shaft hole 8 for mounting the motor shaft.

[0029] The hub 10 is provided with a tie rod hole 7 and a tie rod nut mounting hole 6, which are used to install the tie rod and the tie rod nut, respectively.

[0030] The hub 10 is provided with a fairing 5, which is used to cover the tie rod nut. The fairing 5 has an internal thread 4 on its inner side, and the fairing 5 is connected to the hub 10 by the thread.

[0031] The design method for the closed impeller of the ultra-low specific speed centrifugal hydrogen compressor mentioned above includes the following steps: Step (1): Using conventional centrifugal compressor pneumatic design methods, design according to the multiplied flow rate, determine the flow channel shape, and ensure the flow channel height; Step (2): Reduce the number of flow channels by the same factor as the flow amplification factor to meet the actual flow requirements; Step (3): Design the flow channel on the wheel cover, and the wheel cover surface of the wheel cover is curved; Step (4): After processing the hub and the cover separately, they are assembled by mechanical connection to form a closed impeller.

[0032] Specifically, step (3) also includes weight reduction design for the non-flow channel area of ​​the wheel cover 14, while retaining reinforcing ribs. Step (3) also includes setting a segmented annular stop 13 on the wheel hub 10. The weight reduction structure 1 of the wheel cover 14 cooperates with the segmented annular stop 13 to achieve torque transmission and center positioning.

[0033] The flow rate amplification factor in step (1) is 2-5 times. The flow channel height designed in step (1) is not less than 4mm.

[0034] In step (4), the mechanical connection is a bolted connection.

[0035] Example 3 like Figure 1-5 As shown, the structure of this embodiment is basically the same as that of the above embodiments. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor in this embodiment includes a hub 10 and a cover 14. The two are processed separately and then connected by several bolts 3 to form a closed impeller.

[0036] The impeller cover 14 has a flow channel 11, which is clearly visible from the side. The impeller cover surface of the impeller cover 14 is designed as a curved surface. The non-flow channel area of ​​the impeller cover 14 has a weight reduction structure 1, which reduces weight and retains reinforcing ribs 9 in appropriate positions to enhance impeller rigidity. The impeller cover 14 has a protruding section 15 for installing a sealing mechanism.

[0037] The hub 10 is provided with a shaft hole 8 for mounting the motor shaft; The wheel hub 10 has a tie rod hole 7 for mounting a tie rod; the wheel hub 10 has The wheel hub 10 is provided with a tie rod nut mounting hole 6 for mounting a tie rod nut; The hub 10 is also equipped with a fairing 5, which is connected to the hub 10 via an internal thread 4 to cover the tie rod nut and to rectify the flow.

[0038] The hub 10 is provided with a segmented annular stop 13, which cooperates with the weight reduction part of the wheel cover 14 to achieve center positioning and torque transmission between the two.

[0039] The hub 10 is also provided with a hub protrusion section 12 for installing a sealing mechanism.

[0040] The design method for the closed impeller of the ultra-low specific speed centrifugal hydrogen compressor in this embodiment includes the following steps: Based on the actual flow requirements, the flow channel was designed using conventional centrifugal compressor pneumatic design methods at twice the flow rate to determine the flow channel shape and ensure that the flow channel height reaches more than 4mm. The number of flow channels is reduced by a factor of 2 to ensure that the number of flow channels meets the actual flow requirements. The flow channel is designed on the wheel cover 14, and the surface of the wheel cover is machined into a curved surface; The non-flow channel area of ​​wheel cover 14 is milled to reduce weight, while retaining the reinforcing rib 9; A segmented annular stop 13 is machined on the hub 10; The hub 10 and the cover 14 are machined separately, and then assembled together with bolts 3 to form a closed impeller.

[0041] The above-described structure and design methods effectively solve the machining and performance problems of impellers for centrifugal hydrogen compressors with extremely low specific speeds, thus meeting practical engineering requirements.

[0042] This invention employs a design method that first increases the flow rate and then reduces the number of flow channels, achieving high and rarefied flow channel characteristics for an impeller with extremely low specific speed, significantly increasing the flow channel height, and reducing the processing difficulty; it also adopts a method of separate processing and mechanical assembly of the hub and the cover, changing the traditional one-piece processing technology, further reducing the processing difficulty and minimizing geometric deviations; This invention integrates the flow channel design into the impeller cover, which has a curved surface. The weight reduction design in the non-flow channel area of ​​the impeller cover, combined with the reinforcing rib structure, achieves a synergistic effect of optimizing the rotor system's dynamic characteristics and maintaining structural stiffness. The annular stop on the hub, in conjunction with the impeller cover, ensures accurate torque transmission and center positioning, improving the impeller's operational stability. This invention effectively solves the manufacturing challenges of impellers for centrifugal hydrogen compressors with extremely low specific speeds, balancing aerodynamic performance and manufacturing feasibility, and possesses excellent engineering practicality and industrialization prospects.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A closed impeller for an ultra-low specific speed centrifugal hydrogen compressor, characterized in that, The impeller includes a hub and a cover, which are machined separately and then mechanically connected to form a closed impeller. The cover has a flow channel and its surface is curved. The non-flow channel area of ​​the cover has a weight-reducing structure and retains reinforcing ribs. The hub has a segmented annular stop, and the weight-reducing structure of the cover cooperates with the segmented annular stop to achieve torque transmission and center positioning between the hub and the cover. Both the hub and the cover have protruding sections for installing sealing mechanisms.

2. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to claim 1, characterized in that, The mechanical connection between the wheel hub and the wheel cover is a bolt connection. The wheel cover has a screw hole, and the wheel hub has a corresponding countersunk hole. The bolt passes through the countersunk hole and is threadedly connected to the screw hole.

3. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to claim 1, characterized in that, The weight-reducing structure is a cavity or lightweight hole formed by milling, and the reinforcing rib is a straight structure.

4. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to claim 1, characterized in that, The hub is provided with a shaft hole, a tie rod hole, and a tie rod nut mounting hole, which are used to install the motor shaft, tie rod, and tie rod nut, respectively.

5. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to claim 4, characterized in that, The hub is provided with a fairing, which is connected to the hub by threads and is used to cover the tie rod nut.

6. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to claim 1, characterized in that, The number of flow channels is 2-6.

7. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to claim 1, characterized in that, The protruding section on the wheel hub is the wheel hub protruding section, and the protruding section on the wheel cover is the wheel cover protruding section.

8. The closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to claim 1, characterized in that, The wheel cover has a curved surface, and the flow channel is located on the side of the wheel cover facing the wheel hub.

9. The design method for the closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Adopt the conventional centrifugal compressor pneumatic design method, design according to the multiplied flow rate, determine the flow channel shape, and ensure the flow channel height; S2. Reduce the number of flow channels by the same factor as the flow amplification factor to meet the actual flow requirements; S3. The flow channel is designed on the wheel cover, and the wheel cover surface is designed as a curved surface; the non-flow channel area of ​​the wheel cover is designed to reduce weight while retaining the reinforcing ribs; a segmented annular stop is set on the wheel hub to cooperate with the weight-reducing part of the wheel cover to achieve torque transmission and center positioning. S4. After the hub and wheel cover are processed separately, they are assembled by mechanical connection to form a closed impeller.

10. The design method for the closed impeller of the ultra-low specific speed centrifugal hydrogen compressor according to claim 9, characterized in that, The flow rate amplification factor is 2-5 times, and the designed flow channel height is not less than 4mm; the mechanical connection is a bolt connection.

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