Centrifugal compressor closed radial flow impeller tip clearance flow loss suppression structure

Abstract

The application discloses a centrifugal compressor closed radial flow impeller tip clearance flow loss suppression structure, wherein a tip clearance and a wheel cover seal for reducing the air leakage amount of the tip clearance are arranged between the closed radial flow impeller of the centrifugal compressor and a shell; the closed radial flow impeller comprises a wheel cover, a wheel disc and a plurality of blades, the blades are arranged between the wheel cover and the wheel disc and are arranged in a circumferential direction; the centrifugal compressor further comprises a wheel cover seal; a geometric first groove is arranged on the inner wall of the wheel cover in the circumferential direction and between adjacent blades, and a first protrusion with the same shape as the first groove is arranged on the outer wall of the wheel cover corresponding to the first groove. The application can effectively reduce the airflow kinetic energy of the tip clearance flow and the air leakage amount, thereby effectively suppressing the tip clearance flow loss.

Description

Technical Field

[0001] This invention relates to the field of radial impeller technology, and more specifically, to a structure for suppressing flow loss in the tip gap of a closed radial impeller for a centrifugal compressor. Background Technology

[0002] In recent years, radial impellers have been widely used in low-power industrial production due to their simple structure and manufacturing process, convenient installation, and small size. Radial impellers typically come in three structures: closed, semi-open, and open. For example, closed radial impellers are used in centrifugal compressors. When a closed radial impeller is installed in the casing, there is relative movement, inevitably creating a gap between the moving and stationary parts. This gap causes flow losses in the working fluid within the centrifugal compressor due to the tip clearance, resulting in steam leakage and affecting unit efficiency.

[0003] Existing research on tip clearance leakage focuses on axial-flow impellers. However, the internal flow field structure of closed radial-flow impellers is relatively complex, and the impact of tip clearance leakage flow on impeller mechanical performance is more severe. Leakage loss control technologies for axial-flow impellers cannot be effectively applied to closed radial-flow impellers. Currently, the main technical means to reduce / suppress tip clearance flow losses include reducing the clearance size of moving and stationary components and installing seals. Considering the safety of the unit, the clearance size of moving and stationary components cannot be too small in practical applications. Common seals are divided into internal seals and external seals. The function of internal seals is to prevent gas backflow between stages, such as the impeller cover seal at the impeller cover; however, when the gas flows out of the impeller, it still has a high flow velocity. Using a separate seal structure still results in high tip clearance flow losses in actual use. Therefore, it is necessary to adopt a reasonable structure tailored to the structural characteristics of closed radial-flow impellers to reduce leakage losses and improve the safety and economy of the unit. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a centrifugal compressor closed radial impeller tip gap flow loss suppression structure that can achieve good sealing effect and reduce the flow velocity in the tip gap.

[0005] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0006] A centrifugal compressor closed-circuit impeller tip clearance flow loss suppression structure is disclosed. The centrifugal compressor has a closed-circuit impeller with a tip clearance and a wheel cover seal to reduce leakage at the tip clearance. The closed-circuit impeller includes a wheel cover, a wheel disc, and several blades. The blades are arranged between the wheel cover and the wheel disc and are spaced apart circumferentially. The centrifugal compressor also includes a wheel cover seal. The inner wall of the wheel cover has a first groove of geometric shape circumferentially between adjacent blades, and a first protrusion of the same shape as the first groove is provided on the outer wall of the wheel cover corresponding to the first groove.

[0007] The first groove is multiple in the axial direction, and correspondingly, the first protrusion is multiple in the axial direction.

[0008] The first groove is a regular hexagonal shape, and correspondingly, the first protrusion is also a regular hexagonal shape.

[0009] The wheel cover and the wheel cover seal are connected at one end, which is a stepped structure that gradually rises from left to right in the axial direction. Corresponding to each step, the wheel cover seal is provided with a sealing tooth that matches it.

[0010] The wheel cover seal has multiple second protrusions arranged circumferentially and at intervals on one side corresponding to the flow in direction of the blade tip gap, and a second groove is formed between adjacent second protrusions.

[0011] Compared with the prior art, the beneficial effects of the present invention are:

[0012] 1. The inner wall of the impeller cover of the present invention has a first hexagonal groove between adjacent blades; that is, corresponding to the air passage, multiple first hexagonal grooves are evenly spaced along the flow direction and circumferentially on the inner wall of the impeller cover. By setting this first groove structure, the vortex structure of the impeller endwall region is changed, the lateral pressure gradient of the inner wall region of the impeller cover is reduced, the intensity of the lateral secondary flow is weakened, and the secondary flow loss is reduced. Due to the pressure difference on both sides of the impeller cover, the tip gap will cause a backflow from the outlet. Leakage of this gap flow will increase the unit's steam leakage loss and reduce the unit's efficiency. Corresponding to the first groove, a first hexagonal protrusion with the same shape as the first groove is provided on the outer wall of the impeller cover; when the airflow passes through the first hexagonal protrusion, the lateral velocity of the fluid increases, thereby reducing the kinetic energy of the airflow; when the airflow flows through the impeller cover seal, the flow velocity of the tip gap is further slowed down. By adopting this technical measure, the kinetic energy of the tip gap flow can be effectively reduced, the amount of steam leakage can be reduced, and the tip gap flow loss can be effectively suppressed.

[0013] 2. The first groove of the present invention has multiple axial grooves, and correspondingly, the first protrusion has multiple axial protrusions. Having two or more first grooves and first protrusions in the axial direction can further reduce the flow velocity of the blade tip gap flow.

[0014] 3. In this invention, the end of the wheel cover that seals with the wheel cover has a stepped structure that gradually rises axially from left to right. Corresponding to each step, the wheel cover seal is provided with a sealing tooth that mates with it. This technical measure can effectively improve the sealing effect and effectively suppress flow loss in the blade tip gap.

[0015] 4. The wheel cover seal of the present invention has multiple second protrusions spaced at intervals around the circumference on one side corresponding to the flow ingress direction in the blade tip gap, with a second groove formed between adjacent second protrusions. When the flow in the blade tip gap flows into the second groove between two adjacent second protrusions, a vortex is formed, reducing the fluid kinetic energy and thus effectively reducing steam leakage. This technical measure can further effectively suppress flow losses in the blade tip gap. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] Figure 2 for Figure 1 Enlarged schematic diagram of the middle wheel cover seal 3;

[0018] Figure 3 for Figure 2 View A of the middle wheel cover seal 3;

[0019] Reference numerals: 1—shell; 11—blade tip clearance; 2—closed radial impeller; 21—wheel cover; 211—first groove; 212—first protrusion; 22—wheel disc; 23—blade; 3—wheel cover seal; 31—sealing tooth; 32—second protrusion; 33—second groove. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] In the description of the embodiments of the present invention, it should be noted that "multiple" means two or more; the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present 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, and therefore should not be construed as a limitation of the present invention.

[0024] like Figure 1 — Figure 3 As shown, a centrifugal compressor closed radial impeller tip gap flow loss suppression structure is provided. The centrifugal compressor closed radial impeller 2 and housing 1 are provided with a tip gap 11 and a wheel cover seal 3 to reduce the leakage of the tip gap 11. The closed radial impeller 2 includes a wheel cover 21, a wheel disk 22 and a plurality of blades 23. The blades 23 are arranged between the wheel cover 21 and the wheel disk 22 and are spaced apart circumferentially. The inner wall of the wheel cover 21 is provided with a first groove 211 of geometric shape in the circumferential direction between adjacent blades 23. Corresponding to the first groove 211, a first protrusion 212 of the same shape as the first groove 211 is provided on the outer wall of the wheel cover 21.

[0025] Specifically, an air passage is formed between adjacent blades 23. The mainstream flow from the inlet to the outlet generates a transverse secondary flow in the inner wall region of the impeller cover 21, typically manifesting as various vortex structures. These vortex structures reduce unit efficiency. A regular hexagonal first groove 211 is provided on the inner wall of the impeller cover 21 between adjacent blades 23. Corresponding to the air passage, multiple regular hexagonal first grooves 211 are evenly spaced along the flow direction and circumferentially on the inner wall of the impeller cover 21. By setting this first groove 211 structure, the vortex structure in the impeller endwall region is altered, the transverse pressure gradient in the inner wall region of the impeller cover 21 is reduced, the intensity of the transverse secondary flow is weakened, and secondary flow losses are reduced. Due to the pressure difference on both sides of the impeller cover 21, a gap flow reversing from the outlet occurs in the blade tip clearance 11. Leakage of this gap flow increases the unit's steam leakage losses and reduces unit efficiency. Corresponding to the first groove 211, a first hexagonal protrusion 212 with the same shape as the first groove 211 is provided on the outer wall of the impeller cover 21. When the airflow passes through the hexagonal first protrusion 212, the lateral velocity of the fluid increases, thereby reducing the kinetic energy of the flow in the tip gap 11. When the airflow passes through the impeller cover seal 3, the flow velocity in the tip gap is further reduced. In actual use, the depth and other dimensions of the first groove 211 and the first protrusion 212 are kept consistent, without changing the original strength of the impeller cover 21. At the same time, the number, depth / height, and length of the first groove 211 and the first protrusion 212 are determined according to the specific geometric dimensions and operating parameters of the radial impeller. In actual use, the shape of the first groove 211 and the first protrusion 212 can be a circle, square, triangle, etc. This technical measure can effectively reduce the kinetic energy of the flow in the tip gap, reduce the amount of steam leakage, and thus effectively suppress the loss of the flow in the tip gap.

[0026] like Figure 1 As shown, there are multiple first grooves 211 in the axial direction, and correspondingly, there are multiple first protrusions 212 in the axial direction. In actual use, there are two or more first grooves 211 and first protrusions 212 in the axial direction, which can further reduce the flow velocity of the blade tip gap flow.

[0027] like Figure 1 — Figure 3As shown, the end of the wheel cover 21 that mates with the wheel cover seal 3 has a stepped structure that gradually rises axially from left to right. Corresponding to each step, the wheel cover seal 3 has a corresponding sealing tooth 31. In actual use, the wheel cover 21 and the sealing teeth 31 of the wheel cover seal 3 are in a clearance fit. The wheel cover seal 3 is a labyrinth seal. Labyrinth seals utilize the principle of throttling; as gas passes through each tooth, the pressure drops, resulting in a significant pressure drop after a certain number of teeth. Essentially, the labyrinth seal introduces pressure differential resistance to the gas flow, thereby reducing the gas throughput. Compared to traditional labyrinth seals, the stepped design further reduces the gas throughput. The wheel cover 21 has five steps at one end, and correspondingly, there are also five sealing teeth 31. This technique effectively improves the sealing effect and effectively suppresses flow losses in the blade tip gap.

[0028] like Figure 1 As shown, the wheel cover seal 3 has multiple second protrusions 32 spaced around its circumference on the side corresponding to the direction of flow in the blade tip gap. Adjacent second protrusions 32 form second grooves 33. In actual use, the second grooves 33 formed between two adjacent second protrusions 32 create vortices as the flow into the blade tip gap flows, reducing fluid kinetic energy and effectively minimizing steam leakage. This technique further effectively suppresses flow losses in the blade tip gap.

[0029] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A centrifugal compressor closed-circuit impeller tip clearance flow loss suppression structure, wherein a tip clearance (11) and a wheel cover seal (3) for reducing leakage of the tip clearance (11) are provided between the closed-circuit impeller (2) and the housing (1) of the centrifugal compressor; the closed-circuit impeller (2) includes a wheel cover (21), a wheel disc (22) and a plurality of blades (23), wherein the blades (23) are disposed between the wheel cover (21) and the wheel disc (22) and are spaced apart circumferentially; characterized in that: The inner wall of the wheel cover (21) is provided with a first groove (211) of geometric shape between adjacent blades (23) in the circumferential direction. Corresponding to the first groove (211), the outer wall of the wheel cover (21) is provided with a first protrusion (212) of the same shape as the first groove (211).

2. The centrifugal compressor closed-loop radial impeller tip clearance flow loss suppression structure according to claim 1, characterized in that: The first groove (211) is multiple in the axial direction, and correspondingly, the first protrusion (212) is multiple in the axial direction.

3. The centrifugal compressor closed-loop radial impeller tip clearance flow loss suppression structure according to claim 1 or 2, characterized in that: The first groove (211) is a regular hexagon, and correspondingly, the first protrusion (212) is a regular hexagon.

4. The centrifugal compressor closed-loop radial impeller tip clearance flow loss suppression structure according to claim 1, characterized in that: The wheel cover (21) and the wheel cover seal (3) have a stepped structure that gradually rises from left to right in the axial direction. For each step, the wheel cover seal (3) is provided with a sealing tooth (31) that matches it.

5. The centrifugal compressor closed-loop radial impeller tip clearance flow loss suppression structure according to claim 1, characterized in that: The wheel cover seal (3) is provided with multiple second protrusions (32) around the circumference of the side corresponding to the flow direction of the blade tip gap, and a second groove (33) is formed between adjacent second protrusions (32).

Images