Back blade structure of radial turbomachinery

Abstract

The back blade structure of the radial impeller machine comprises a plurality of streamline back blades, the streamline back blades are installed on the back face of a centrifugal impeller at equal intervals, and gaps are formed in the tops of the streamline back blades, the side walls of the streamline back blades and the inner wall of a case. The front edge points of the streamline back blades are arranged close to an impeller shaft of the centrifugal impeller, and the tail edge points of the streamline back blades are arranged close to the outer edge of the centrifugal impeller. The working face of the streamline back blade is a convex face, and the width of the middle section of the streamline back blade is larger than that of the two ends of the streamline back blade. According to the utility model, the extra shaft power consumption can be reduced, the influence on the efficiency of the centrifugal impeller is reduced, the energy loss and the shaft power output are reduced, the back fluid static pressure is reduced more efficiently, and the effect of balancing the axial force is achieved.

Description

Technical Field

[0001] This utility model relates to the field of radial impeller machinery technology, and in particular to a back blade structure for radial impeller machinery. Background Technology

[0002] Centrifugal compressors are machines that convert the mechanical energy of blades into the energy of a fluid working medium. During operation, the axial force on the centrifugal impeller includes: the fluid pressure within the blade passages, the inlet fluid pressure on the guide cap, and the fluid pressure on the impeller cover and back. The pressure difference between the impeller inlet and outlet causes an imbalance in the axial forces on the impeller. This axial force causes the entire shaft to shift, leading to impeller misalignment, decreased compressor efficiency, and poor sealing. In severe cases, it can even damage the impeller, bearings, and seals, affecting the compressor's operational safety.

[0003] Existing axial force balancing technologies include: balancing holes, double-suction impellers, thrust bearings, balancing discs, and back blades. The balancing hole method involves symmetrical openings near the hub to return the outlet fluid to the inlet. While simple and easy to implement, it increases internal leakage and reduces compressor efficiency, making it unsuitable for high-pressure applications. The double-suction impeller, with its back-to-back symmetrical design, allows fluid to enter from both sides, theoretically achieving complete axial force balance by canceling each other out, making it suitable for high-flow-rate applications. However, in practice, due to manufacturing processes and differences in flow on both sides, complete balance cannot be achieved, and its complex structure requires significant installation space. Thrust bearings are used for small impellers with low axial forces and are typically used in conjunction with other methods, requiring maintenance and lubrication. Balancing discs can automatically balance axial forces under different operating conditions, but they add mechanical components, occupy axial space, and require high sealing performance. Back blades are located on the back of the centrifugal impeller. The rotation of these blades on the impeller's back drives fluid movement, converting pressure energy into fluid kinetic energy, reducing the static pressure within the sealed cavity, and thus reducing the axial force in the impeller's back area. In contrast, the back blade has a simple structure, does not cause additional leakage, and the low-pressure area formed by the rotation of the blade can reduce leakage and prevent impurities from entering the shaft seal area.

[0004] Currently, the impeller back blade structure is typically a set of straight blades with a rectangular cross-section, with the working surface and back surface perpendicular to the impeller back surface, one end attached to the shaft end, and the other end attached to the outer edge of the impeller. This structure results in significant energy loss, leading to additional shaft power output, and also creates a small low-pressure area with poor axial force balance.

[0005] To address this, a back blade structure for radial impeller machinery is proposed. Utility Model Content

[0006] The purpose of this invention is to provide a back blade structure for a radial impeller machine, which aims to solve or improve at least one of the above-mentioned technical problems.

[0007] To achieve the above objectives, the present invention provides the following solution: The present invention provides a back blade structure for a radial impeller, comprising a plurality of streamlined back blades, wherein the plurality of streamlined back blades are equally spaced and installed on the back of a centrifugal impeller, and gaps are provided between the top of the streamlined back blades, the sidewalls of the streamlined back blades and the inner wall of the casing.

[0008] The leading edge of the streamlined back blade is located close to the impeller shaft of the centrifugal impeller, and the trailing edge of the streamlined back blade is located close to the outer edge of the centrifugal impeller; the working surface of the streamlined back blade is a convex surface, and the width of the middle section of the streamlined back blade is greater than the width of the two ends of the streamlined back blade.

[0009] According to the present invention, the number of streamlined back blades in a radial impeller machine is at least three.

[0010] According to the present invention, the back blade structure of a radial impeller machine has a cross-sectional thickness of 1.5 mm to 10 mm.

[0011] According to the present invention, the back blade structure of a radial impeller machine has a chord length c of 30mm to 90mm.

[0012] According to the present invention, the back blade structure of a radial impeller machine has a leading edge angle α of 15° to 35°.

[0013] According to the present invention, the back blade structure of a radial impeller machine has a trailing edge angle β of 15° to 40°.

[0014] According to the present invention, the back blade structure of a radial impeller machine has a streamlined back blade with an installation angle θ of 35° to 85°.

[0015] The present invention discloses the following technical effects:

[0016] The present invention has several streamlined back blades installed at equal intervals on the back of the centrifugal impeller, and gaps are provided at the top of the streamlined back blades, the side wall of the streamlined back blades and the inner wall of the casing. The working surface does work on the fluid on the back of the blades, converting pressure energy into fluid kinetic energy. Furthermore, due to the centrifugal force, the fluid is accelerated and the fluid static pressure is reduced, thereby achieving the effect of balancing the axial force.

[0017] In use, the back blades of this invention rotate clockwise or counterclockwise, and the working surface of the back blades drives the fluid movement, causing the fluid to flow from the inside to the outer edge of the centrifugal impeller. This reduces the fluid pressure, creating a low-pressure zone inside. Furthermore, the fluid near the outer edge, due to its velocity, also experiences a pressure drop. After flowing out from the working blades, the fluid leaks through the gap between the impeller and the volute casing to the back of the impeller, and through the gap between the top of the streamlined back blades and the casing surface to the shaft end (the central area of ​​the back). The streamlined back blades flow to replenish the low-pressure area fluid carried away by the centrifugal force of the rotating blades. Part of the fluid in the low-pressure area flows from the center of the back of the centrifugal impeller to the outer edge of the impeller under the action of the streamlined back blades, merging with the leakage flow of the impeller and flowing back into the low-pressure area through the gap. The other part of the fluid leaks backward through the shaft seal. Therefore, the streamlined back blades increase the area of ​​the low-pressure region and reduce the static pressure. In addition, the low-pressure region formed by the rotation of the streamlined back blades reduces the pressure difference before and after the shaft seal, thereby reducing the external leakage of the shaft seal.

[0018] This invention employs streamlined back blades, which can significantly reduce fluid resistance during rotation and create a larger low-pressure area inside, allowing the back blades to balance a greater axial force. Compared to simple rectangular cross-section blades, streamlined back blades can reduce additional shaft power consumption, thereby reducing the impact on centrifugal impeller efficiency. By reducing energy loss and shaft power output through streamlined back blades, the static pressure of the back fluid can be reduced more efficiently.

[0019] This invention uses streamlined back blades, which overcomes the shortcomings of existing rectangular back blade structures, such as a small low-pressure area and poor axial force balance. By adjusting the installation angle and position of several streamlined back blades, the low-pressure area can be adjusted to increase the low-pressure area and enhance the balance effect. It is suitable for axial force balance of centrifugal impellers or centripetal impellers, and for adjusting the low-pressure area and axial force. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of this utility model;

[0022] Figure 2 for Figure 1 Sectional view of AA;

[0023] Figure 3This is a schematic diagram of the streamlined back blade structure in this utility model;

[0024] Figure 4 This is a schematic diagram of the installation of the impeller of the present invention applied to a multi-stage centrifugal compressor;

[0025] Figure 5 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0026] Figure 6 This is a structural schematic diagram of Embodiment 3 of the present invention.

[0027] Among them, 1. Streamlined back blades; 2. Centrifugal impeller; 3. Casing; 4. Gap; 5. Impeller shaft; 6. Main blades; 7. Low-pressure zone. Detailed Implementation

[0028] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0029] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] Reference Figures 1-4 This utility model provides a back blade structure for a radial impeller machine, including a plurality of streamlined back blades 1, which are installed at equal intervals on the back of a centrifugal impeller 2. The top of the streamlined back blades 1, the side wall of the streamlined back blades 1 and the inner wall of the casing 3 are all provided with gaps 4.

[0032] The leading edge of the streamlined back blade 1 is located close to the impeller shaft 5 of the centrifugal impeller 2, and the trailing edge of the streamlined back blade 1 is located close to the outer edge of the centrifugal impeller 2; the working surface of the streamlined back blade 1 is a convex surface, and the width of the middle section of the streamlined back blade 1 is greater than the width of the two ends of the streamlined back blade 1.

[0033] With this configuration, several streamlined back blades 1 of this utility model are installed at equal intervals on the back of the centrifugal impeller 2, and gaps 4 are provided on the top of the streamlined back blades 1, the side wall of the streamlined back blades 1 and the inner wall of the casing 3. The working surface does work on the fluid on the back of the blades, converting pressure energy into fluid kinetic energy. Furthermore, due to the centrifugal force, the fluid is accelerated and the fluid static pressure is reduced, thus achieving the effect of balancing the axial force.

[0034] In use, the streamlined back blades 1 of the centrifugal impeller 2 rotate clockwise or counterclockwise. The working surface of the streamlined back blades 1 drives the fluid movement, causing the fluid to flow from the inside to the outer edge of the centrifugal impeller 2. The fluid pressure decreases, forming a low-pressure zone 7 inside. Furthermore, the fluid near the outer edge has a certain velocity, resulting in a further decrease in pressure. After flowing out from the working blades of the centrifugal impeller 2, the fluid leaks through the gap between the centrifugal impeller 2 and the volute casing 3 to the back of the centrifugal impeller 2. It also leaks through the gap 4 between the top of the streamlined back blades 1 and the surface of the casing 3 to the shaft end (back side). The fluid in the central region (the area of ​​the centrifugal impeller 2) flows to replenish the fluid in the low-pressure region carried away by the centrifugal force of the streamlined back blades 1. Part of the fluid in the low-pressure region 7 flows from the center of the back of the centrifugal impeller 2 to the outer edge of the centrifugal impeller 2 under the action of the streamlined back blades 1, where it merges with the leakage flow of the centrifugal impeller 2 and flows back to the low-pressure region 7 through the gap 4. The other part of the fluid leaks backward through the shaft seal. Therefore, the streamlined back blades 1 increase the area of ​​the low-pressure region and reduce the static pressure. In addition, the low-pressure region 7 formed by the rotation of the streamlined back blades 1 reduces the pressure difference before and after the shaft seal, thereby reducing the external leakage of the shaft seal.

[0035] This invention employs a streamlined back blade 1, which can significantly reduce fluid resistance during rotation and form a larger low-pressure area inside, allowing the back blade to balance a larger axial force. Compared to a simple rectangular cross-section blade, the streamlined back blade 1 can reduce additional shaft power consumption, thereby reducing the impact on the efficiency of the centrifugal impeller 2. By reducing energy loss and shaft power output through the streamlined back blade 1, the static pressure of the back fluid can be reduced more efficiently.

[0036] This utility model adopts a streamlined back blade 1, which overcomes the shortcomings of the existing rectangular back blade structure, which has a small low-pressure area and poor axial force balance effect. By adjusting the installation angle and position of several streamlined back blades 1, the low-pressure area can be adjusted to increase the low-pressure area and enhance the balance effect. It is suitable for axial force balance of centrifugal impeller 2 or centripetal impeller, and for adjusting the low-pressure area and axial force.

[0037] In a further optimized design, the number of streamlined back blades 1 is at least three; in this embodiment, it is preferably 4 to 6.

[0038] Further optimization of the design resulted in a maximum thickness of 1.5mm to 10mm for the cross-section of the streamlined back blade 1.

[0039] Further optimization of the design: the chord length c of the streamlined back blade 1 is 30mm to 90mm, and the thickness of the cross section of the streamlined back blade 1 is the straight-line distance between the leading edge and trailing edge of the blade.

[0040] Further optimization of the scheme: the leading edge angle α of the streamlined back blade 1 is 15° to 35°. The leading edge angle α of the streamlined back blade 1 is the angle between the tangent at the leading edge of the blade and the chord length direction.

[0041] Further optimization of the scheme: the trailing edge angle β of the streamlined back blade 1 is 15° to 40°. The trailing edge angle β of the streamlined back blade 1 is the angle between the tangent at the trailing edge of the blade and the chord direction.

[0042] Further optimization of the scheme: the installation angle θ of the streamlined back blade 1 is 35° to 85°. The installation angle θ of the streamlined back blade 1 is the angle between the blade chord length of the streamlined back blade 1 and the impeller radial direction (affecting the fluid injection direction).

[0043] Further optimization of the design: the blade bend angle of the streamlined back blade 1 is 15° to 50°. The blade bend angle is the angle between the tangents of the middle arc line of the streamlined back blade 1 at the leading edge and trailing edge (i.e., the degree of blade bending).

[0044] In this invention, the parameters of the streamlined back blade 1, such as chord length, maximum deflection, maximum thickness, leading edge angle, trailing edge angle, blade bend angle, installation angle, blade height, and number of blades, can all be adjusted according to the actual axial force, which is used to adjust the low-pressure area and axial force.

[0045] Further optimization of the scheme: for low-speed impellers, the streamlined back blade 1 can be machined separately and then connected and installed on the back of the centrifugal impeller 2 by welding or threading, which is suitable for situations where the strength requirement is not high.

[0046] Further optimization of the scheme: the blade shape of the streamlined back blade 1 can be stacked according to a certain height distribution superposition rule in the blade height direction of the streamlined back blade 1 to form a three-dimensional blade.

[0047] Example 2

[0048] Reference Figure 5 The difference between this embodiment and embodiment 1 is that the streamlined back blade 1 is teardrop-shaped.

[0049] Example 3

[0050] Reference Figure 6 The difference between this embodiment and embodiment 1 is that the streamlined back blade 1 is wedge-shaped.

[0051] In the description of this utility model, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model 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 limitations on this utility model.

[0052] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A back blade structure for a radial impeller machine, characterized in that: It includes several streamlined back blades (1), and several of the streamlined back blades (1) are installed at equal intervals on the back of the centrifugal impeller (2). The top of the streamlined back blades (1), the side wall of the streamlined back blades (1) and the inner wall of the casing (3) are all provided with gaps (4). The leading edge of the streamlined back blade (1) is located close to the impeller shaft (5) of the centrifugal impeller (2), and the trailing edge of the streamlined back blade (1) is located close to the outer edge of the centrifugal impeller (2); the working surface of the streamlined back blade (1) is a convex surface, and the width of the middle section of the streamlined back blade (1) is greater than the width of both ends of the streamlined back blade (1).

2. The back blade structure of the radial impeller machinery according to claim 1, characterized in that: The number of the streamlined back blades (1) is at least three.

3. The back blade structure of the radial impeller machinery according to claim 1, characterized in that: The thickness of the cross section of the streamlined back blade (1) is 1.5 mm to 10 mm.

4. The back blade structure of the radial impeller machinery according to claim 1, characterized in that: The chord length c of the streamlined back blade (1) is 30mm to 90mm.

5. The back blade structure of the radial impeller machinery according to claim 1, characterized in that: The leading edge angle α of the streamlined back blade (1) is 15° to 35°.

6. The back blade structure of the radial impeller machinery according to claim 1, characterized in that: The trailing edge angle β of the streamlined back blade (1) is 15° to 40°.

7. The back blade structure of the radial impeller machinery according to claim 1, characterized in that: The installation angle θ of the streamlined back blade (1) is 35° to 85°.

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