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 centrifugal impeller, extra shaft power consumption can be reduced, the influence on the efficiency of the centrifugal impeller is reduced, energy loss and shaft power output are reduced, back fluid static pressure is reduced more efficiently, and the effect of balancing axial force is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of radial impeller machinery, and in particular to a back blade structure of a radial impeller machinery. Background Art

[0002] A centrifugal compressor is a machine that converts the mechanical energy of blades into the energy of a fluid. During operation, the axial forces acting on the impeller include: fluid pressure within the blade passages, inlet fluid pressure on the guide cap, and fluid pressure on the impeller cover and back. The pressure differential between the impeller inlet and outlet creates an imbalance in the impeller's axial forces. This axial force can cause the entire shaft to move, leading to impeller misalignment, reduced compressor efficiency, and poor sealing. In severe cases, the impeller, bearings, and seals may even be damaged, compromising compressor safety.

[0003] Existing axial force balancing technologies include balancing holes, double-suction impellers, thrust bearings, balancing discs, and back vanes. The balancing hole method creates symmetrical holes near the hub to return the outlet fluid to the inlet. While simple and easy to implement, it can increase internal leakage and circulation, reducing compressor efficiency and making it unsuitable for high-pressure applications. Double-suction impellers utilize a back-to-back symmetrical design, allowing fluid to enter from both sides, counteracting axial forces. Theoretically, this completely balances axial forces and is suitable for high-flow applications. However, in practice, due to manufacturing process and flow differences between the two sides, complete balancing cannot be achieved. Furthermore, the structure is complex and requires a large installation space. Thrust bearings are typically used in conjunction with other methods for small impellers with low axial forces and require maintenance and lubrication. Balancing discs can automatically balance axial forces under various operating conditions, but they require additional mechanical structure, occupy a certain amount of axial space, and place high demands on sealing. Back vanes are located on the back of the centrifugal impeller. The rotation of the blades at the back of the impeller drives fluid motion, converting pressure energy into kinetic energy, reducing the static pressure within the seal chamber, and thus alleviating axial forces in the impeller back area. Relatively speaking, the back blade has a simple structure and does not cause additional leakage. The low-pressure area formed by the rotation of the blade can also 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 back of the impeller, one end abutting the shaft end, and the other abutting the outer edge of the impeller. This structure causes significant energy loss, resulting in excessive shaft power output, and creates a smaller low-pressure area, resulting in poor axial force balance.

[0005] Therefore, a back blade structure of a radial impeller machine is proposed. Summary of the Invention

[0006] An object of the present invention is to provide a back blade structure of a radial impeller machine, aiming to solve or improve at least one of the above-mentioned technical problems.

[0007] To achieve the above-mentioned object, the present invention provides the following solution: The present invention provides a back blade structure of a radial impeller machine, comprising a plurality of streamlined back blades, wherein the plurality of streamlined back blades are installed at equal intervals on the back of the centrifugal impeller, and gaps are provided between the tops of the streamlined back blades, the side walls of the streamlined back blades, and the inner wall of the casing;

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

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

[0010] According to the back blade structure of a radial impeller machine provided by the present invention, the thickness of the cross section of the streamlined back blade is 1.5 mm to 10 mm.

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

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

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

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

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

[0016] The present invention comprises a plurality of streamlined back blades mounted at equal intervals on the back of the centrifugal impeller, and gaps are provided between the tops of the streamlined back blades, the sidewalls of the streamlined back blades, and the inner wall of the casing. The working surface performs work on the fluid behind the blades, converting pressure energy into fluid kinetic energy. Furthermore, due to the centrifugal force, the fluid is accelerated and the static pressure of the fluid is reduced, thereby achieving the effect of balancing the axial force.

[0017] When the present invention is in use, the back blades of the centrifugal impeller rotate clockwise or counterclockwise, and the working surface of the back blade drives the fluid to move, causing the fluid to flow from the inside to the outer edge of the centrifugal impeller, thereby reducing the fluid pressure and forming a low-pressure area inside. Moreover, the fluid near the outer edge has a certain speed, so the pressure also drops to some extent. After the fluid flows out from the working blades of the centrifugal impeller, it leaks to the back of the centrifugal impeller through the gap between the centrifugal impeller and the volute casing, and leaks to the back of the centrifugal impeller through the gap between the top of the streamlined back blade and the casing surface, toward the shaft end (the center area of the back). 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 amount of leakage from the shaft seal.

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

[0019] The present invention adopts streamlined back blades to overcome the shortcomings of the existing rectangular back blade structure, such as the small low-pressure area and poor axial force balancing effect. 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 balancing effect. It is suitable for the axial force balance of centrifugal impellers or centripetal impellers, and adjusts the low-pressure area and axial force. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 It is a structural schematic diagram of the present invention;

[0022] Figure 2 for Figure 1 Cross-sectional view of AA;

[0023] Figure 3 This is a schematic structural diagram of the streamlined back blade of the present invention;

[0024] Figure 4 Schematic diagram of the installation of an impeller of a multi-stage centrifugal compressor according to the present invention;

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

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

[0027] Among them, 1. Streamlined back blade; 2. Centrifugal impeller; 3. Casing; 4. Gap; 5. Impeller shaft; 6. Main blade; 7. Low pressure area. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] Reference Figures 1-4 The present invention provides a back blade structure of a radial impeller machine, comprising a plurality of streamlined back blades 1, which are evenly spaced and installed on the back of a centrifugal impeller 2, and a gap 4 is provided between the top of the streamlined back blade 1, the side wall of the streamlined back blade 1 and the inner wall of a casing 3;

[0032] The leading edge of the streamlined back blade 1 is arranged close to the impeller shaft 5 of the centrifugal impeller 2, and the trailing edge of the streamlined back blade 1 is arranged close to the outer edge of the centrifugal impeller 2; the working surface of the streamlined back blade 1 is set as 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] In this arrangement, the streamlined back blades 1 of the present invention are installed at equal intervals on the back of the centrifugal impeller 2, and gaps 4 are provided between the top of the streamlined back blade 1, the side wall of the streamlined back blade 1, and the inner wall of the casing 3. The working surface performs work on the fluid on the back of the blade, converting pressure energy into fluid kinetic energy. Due to the centrifugal force, the fluid is accelerated and the static pressure of the fluid is reduced, thereby achieving the effect of balancing the axial force.

[0034] When the present invention is in use, the streamlined back blade 1 of the centrifugal impeller 2 rotates clockwise or counterclockwise, and the working surface of the streamlined back blade 1 drives the fluid to move, causing the fluid to flow from the inside to the outer edge of the centrifugal impeller 2, thereby reducing the fluid pressure and forming a low-pressure area 7 inside. Moreover, the fluid near the outer edge has a certain speed, so the pressure also decreases. After the fluid flows out from the working blades of the centrifugal impeller 2, it leaks to the back of the centrifugal impeller 2 through the gap between the centrifugal impeller 2 and the volute casing 3, and leaks to the back of the centrifugal impeller 2 through the gap 4 between the top of the streamlined back blade 1 and the surface of the casing 3, toward the shaft end (the middle of the back). The fluid in the low-pressure area 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 blade 1, merges with the leakage flow of the centrifugal impeller 2, and flows back to the low-pressure area 7 through the gap 4; the other part of the fluid leaks backward through the shaft seal; therefore, the streamlined back blade 1 increases the area of the low-pressure area and reduces the static pressure. In addition, the low-pressure area 7 formed by the rotation of the streamlined back blade 1 reduces the pressure difference before and after the shaft seal, thereby reducing the external leakage of the shaft seal;

[0035] The present invention uses a streamlined back blade 1 to significantly reduce fluid resistance during rotation and form a larger low-pressure area inside, so that the back blade can balance a larger axial force. Compared with 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] The present invention adopts a streamlined back blade 1, which overcomes the shortcomings of the existing rectangular back blade structure, such as a small low-pressure area and poor axial force balancing 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 balancing effect. It is suitable for balancing the axial force of a centrifugal impeller 2 or a centripetal impeller, and adjusting the low-pressure area and axial force.

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

[0038] According to a further optimized solution, the maximum thickness of the cross section of the streamlined back blade 1 is 1.5 mm to 10 mm.

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

[0040] According to a further optimization scheme, the leading edge angle α of the streamlined back blade 1 is 15° to 35°, and the leading edge angle α of the streamlined back blade 1 is the angle between the tangent line at the leading edge of the blade and the chord length direction.

[0041] According to a further optimization scheme, the trailing edge angle β of the streamlined back blade 1 is 15° to 40°, and the trailing edge angle β of the streamlined back blade 1 is the angle between the tangent line at the trailing edge of the blade and the chord length direction.

[0042] According to a further optimization scheme, the installation angle θ of the streamlined back blade 1 is 35° to 85°, and 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 incident direction of the fluid).

[0043] According to a further optimization scheme, the blade bending angle of the streamlined back blade 1 is 15° to 50°, and the blade bending angle is the angle between the tangent lines of the middle arc line of the streamlined back blade 1 at the leading edge and the trailing edge (ie, the degree of blade curvature).

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

[0045] As a further optimization solution, for low-speed impellers, the streamlined back blade 1 can be processed separately first 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] According to a further optimization scheme, the blade shape of the streamlined back blade 1 can be stacked in the blade height direction of the streamlined back blade 1 according to a certain height distribution superposition rule 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 in the shape of a water drop.

[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 the present invention, it should be understood that the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, 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 a limitation on the present invention.

[0052] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art will be able to make other variations or modifications based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A back blade structure of a radial impeller machine, characterized by: The invention comprises a plurality of streamlined back blades (1), wherein the plurality of streamlined back blades (1) are installed at equal intervals on the back of a centrifugal impeller (2), and gaps (4) are provided between the top of the streamlined back blades (1), the side walls of the streamlined back blades (1) and the inner wall of a casing (3); The leading edge of the streamlined back blade (1) is arranged close to the impeller shaft (5) of the centrifugal impeller (2), and the trailing edge of the streamlined back blade (1) is arranged close to the outer edge of the centrifugal impeller (2); the working surface of the streamlined back blade (1) is arranged as 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 machine 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 machine 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 machine according to claim 1, characterized in that: The chord length c of the streamlined back blade (1) is 30 mm to 90 mm.

5. The back blade structure of the radial impeller machine 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 machine 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 machine 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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