A centrifugal impeller with high cavitation resistance and jet vanes

Abstract

The application discloses a centrifugal impeller with high cavitation resistance and jet blades, wherein a rough band is arranged at the head area of the centrifugal blade close to the inlet edge of the centrifugal impeller, and the rough band is arranged on the pressure surface of the centrifugal blade and the suction surface of the centrifugal blade; the rough band on the pressure surface of the centrifugal blade is in a convex rib shape, and the rough band on the suction surface of the centrifugal blade is in a groove shape; the convex rib and the groove are both composed of multiple rows arranged at intervals, and the convex rib and the groove are both arranged along the vertical direction of the centrifugal blade; the centrifugal impeller further comprises jet blades, the jet blades are in a spiral straight blade shape and the length of the jet blades is less than two-thirds of the length of the centrifugal blade, the number of the jet blades corresponds to the number of the centrifugal blades one by one; the jet blades are arranged close to the suction surface of the centrifugal blade, and the jet blades and the centrifugal blades have the same spiral bending direction; the inlet edge of the jet blade is close to the suction surface of the centrifugal blade and gradually decreases the distance from the suction surface with the increase of the radial radius, and the outlet edge of the jet blade and the outlet edge of the centrifugal blade are at the same radius at the edge of the centrifugal impeller.

Description

Technical Field

[0001] This invention belongs to the field of water pump technology, specifically relating to a centrifugal impeller with high cavitation resistance and jet blades. Background Technology

[0002] During the operation of a centrifugal impeller, when the impeller inlet pressure drops to near the local vaporization pressure, cavitation occurs in the vicinity of the impeller inlet. As the impeller inlet pressure continues to decrease, the cavitation phenomenon gradually intensifies, leading to a gradual decrease in impeller head and efficiency. With further development of cavitation, the centrifugal impeller flow channel becomes blocked by cavitation bubbles, causing fluid interruption. At this point, the centrifugal impeller can no longer function normally, and vibration and noise will be generated. Severe cavitation can cause blade breakage or puncture of the impeller's front and rear cover plates, resulting in serious accidents.

[0003] The liquid flow pattern within a centrifugal impeller is a complex flow within a three-dimensional channel in a rotating coordinate system, exhibiting complex and variable flow patterns influenced by numerous factors. In practical design, the limited number of blades leads to boundary layer separation near the blade suction surface at the blade outlet under adverse pressure gradients, resulting in flow separation, backflow, and the generation of numerous vortices within the channel. Simultaneously, within the boundary layer, the unbalanced forces acting on liquid particles cause uneven energy and pressure distribution among different regions of the flow channel, generating secondary flows from the impeller's rear cover to the front cover and from the pressure surface to the suction surface. This creates low-energy fluid accumulation regions in the impeller outlet front cover region and on the blade suction surface, thus forming a jet-wake structure.

[0004] The jet-wake structure of a centrifugal impeller severely affects the smoothness of impeller flow, leading to a decrease in the impeller's head and efficiency. Furthermore, since the impeller outlet is connected to the condenser chamber, the jet-wake structure causes the fluid at the impeller outlet to have strong circulation, resulting in significant frictional losses with the condenser chamber, generating heat, and causing unstable fluid delivery, thereby reducing the pump's operating efficiency. Summary of the Invention

[0005] This invention provides a centrifugal impeller with high cavitation resistance and jet blades, aiming to solve the problem of severe cavitation in existing impellers and reduced pump operating efficiency.

[0006] Therefore, the present invention adopts the following technical solution:

[0007] A centrifugal impeller with high cavitation resistance and jet blades is provided. The centrifugal blades have a rough band in the head region near the inlet edge of the centrifugal impeller. The rough band is located on the pressure surface and suction surface of the centrifugal blades. The rough band on the pressure surface of the centrifugal blades is convex, and the rough band on the suction surface of the centrifugal blades is grooved. Both the convex and grooves include multiple channels arranged at intervals, and both the convex and grooves are arranged along the vertical direction of the centrifugal blades.

[0008] It also includes jet blades, which are helical straight blades with a length less than two-thirds that of centrifugal blades. The number of jet blades corresponds one-to-one with the number of centrifugal blades. The jet blades are arranged close to the suction surface of the centrifugal blades, and the helical bending direction of the jet blades and centrifugal blades is the same. The inlet edge of the jet blade is close to the suction surface of the centrifugal blade, and the distance between it and the suction surface gradually decreases as the radial radius increases. The outlet edge of the jet blade and the outlet edge of the centrifugal impeller blade are at the same radius as the outlet edge of the centrifugal impeller.

[0009] Furthermore, the cross-section of the groove is semi-circular, and the cross-section of the ridge is also semi-circular, with the groove and the ridge positioned directly opposite each other.

[0010] Furthermore, the radii of the groove and the convex ridge are equal, and the radius is less than 1 / 2 of the thickness of the inlet edge of the centrifugal blade.

[0011] Furthermore, the grooves and protrusions each comprise 3 to 5 channels.

[0012] Furthermore, the inlet edge of the centrifugal blade is rounded.

[0013] The beneficial effects of this invention are as follows:

[0014] 1. This invention provides a concave semi-cylindrical streamlined roughening band on the suction surface near the inlet edge of the centrifugal impeller blade, and a convex semi-cylindrical streamlined roughening band on the pressure surface. This roughening band increases the roughness of the suction and pressure surfaces near the inlet of the centrifugal impeller blade, effectively reducing the turbulent kinetic energy in the near-avoidance zone of the centrifugal impeller flow channel, weakening the vortex intensity, making the flow channel relatively stable, reducing the cavitation volume, and effectively suppressing the initiation and development of cavitation. This also effectively reduces the generation of vibration and noise induced by cavitation.

[0015] 2. The roughening zone on the suction and pressure surfaces of the centrifugal blades of the present invention is semi-cylindrical, making its shape closer to a streamlined shape. This structure can ensure that the anti-cavitation performance of the centrifugal impeller is improved while effectively reducing the hydraulic loss of fluid passing through the roughening zone.

[0016] 3. This invention adds jet blades to the centrifugal impeller design. Since the flow channel area between the jet blades and the suction surfaces of adjacent centrifugal blades gradually decreases, according to the principle of fluid continuity, a smaller area results in a larger velocity. That is, by controlling the flow channel area between the jet blades and the suction surfaces of adjacent centrifugal impeller blades, the fluid jet velocity in this region can be controlled. Based on the momentum law, the required increase in fluid velocity in the low-energy region at the impeller outlet can be calculated. Through the reasonable addition of jet blades in this invention, vortex backflow and jet wake phenomena are appropriately weakened or even completely eliminated, making the fluid flow through the impeller channel smoother and improving the impeller head and efficiency. Simultaneously, the jet increases the radial velocity of the fluid, reduces the circulation time of the fluid in the accumulator chamber, reduces fluid hydraulic losses, and further improves the pump's efficiency and head. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the ideal velocity profile of the jet and its wake.

[0018] Figure 2 This is a schematic diagram of the actual velocity profile of the jet and its wake.

[0019] Figure 3 This is a front view of the centrifugal impeller of the present invention;

[0020] Figure 4 yes Figure 3 Cross-sectional view;

[0021] Figure 5 This is a schematic diagram of the test bench for a specific implementation method;

[0022] Figure 6 This is a comparison chart of external characteristic curves for specific implementation methods;

[0023] In the diagram: 1-Centrifugal impeller inlet side, 2-Centrifugal impeller outlet side, 3-Centrifugal blade, 4-Jet blade, 5-Pressure surface, 6-Protruding ridge, 7-Suction surface, 8-Groove, 9-Centrifugal impeller front cover plate, 10-Centrifugal impeller rear cover plate. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings:

[0025] like Figure 3 and 4As shown, a centrifugal impeller with high cavitation resistance and jet blades is provided. A rough band is provided at the head region of the centrifugal blade 3 near the inlet edge 1 of the centrifugal impeller. The rough band is located on the pressure surface 5 and suction surface 7 of the centrifugal blade 3. The rough band on the pressure surface 5 of the centrifugal blade 3 is convex, while the rough band on the suction surface 7 is grooved. The cross-section of the groove 8 is semi-circular, and the cross-section of the convex 6 is also semi-circular. The radii of the groove 8 and the convex 6 are equal and less than half the thickness of the inlet edge of the centrifugal blade 3. Both the convex 6 and the groove 8 include 3 to 5 grooves spaced apart. The grooves 8 and the convex 6 are positioned opposite each other, and both the convex 6 and the grooves 8 are arranged along the vertical direction of the centrifugal blade 3.

[0026] It also includes jet blades 4, which are helical straight blades with a length less than two-thirds of that of centrifugal blades 3. The number of jet blades 4 corresponds one-to-one with that of centrifugal blades 3. The jet blades 4 are arranged close to the suction surface 7 of centrifugal blades 3, and the helical bending direction of jet blades 4 and centrifugal blades 3 is the same. The inlet edge of jet blades 4 is close to the suction surface 7 of centrifugal blades 3 and the distance between it and the suction surface 7 gradually decreases as the radial radius increases. The outlet edge of jet blades 4 and the outlet edge of centrifugal impeller blades are at the same radius as the outlet edge 2 of centrifugal impeller.

[0027] The jet blade 4 adopts a spiral straight blade, which is convenient for manufacturing; the inlet edge of the centrifugal blade 3 is rounded to reduce fluid hydraulic loss; the centrifugal blade 3 can be a three-dimensional twisted blade or a cylindrical blade. Similar to conventional centrifugal impellers, the centrifugal impeller is also equipped with a centrifugal impeller front cover plate 9 and a centrifugal impeller rear cover plate 10.

[0028] Experimental comparison:

[0029] To verify the effectiveness of this invention's impeller, an experimental platform (such as...) was built. Figure 5 External characteristic tests and cavitation performance tests were conducted on the original scheme and the structure of the present invention using a horizontal centrifugal pump of the same specification. When testing with the original scheme, the impeller was the factory-installed shape of the horizontal centrifugal pump; when testing with the present invention, the factory-installed impeller of the centrifugal pump was disassembled and replaced with the impeller of the present invention. The impeller of the present invention has the same diameter and the same number of centrifugal blades as the original impeller.

[0030] like Figure 5 As shown, the test bench system includes a centrifugal pump, cavitation tank, torque meter, inlet and outlet pressure gauges, etc., with the turbine flow meter having an accuracy of ±0.5% and the pressure gauges having an accuracy of ±0.1%. During the test, the water temperature was kept relatively stable, the pump head was measured by the inlet and outlet pressure gauges, and the flow rate was measured by the flow meter. Figure 3 This is a comparison chart of the external characteristic curves of the invented structure and the original design, by... Figure 3It can be seen that the head and efficiency values ​​of the structure of this invention and the original scheme change in the same trend under varying operating conditions. However, the head and efficiency values ​​of this invention are slightly higher than those of the original scheme, indicating that the jet structure of this invention can effectively improve the flow field structure inside the impeller compared to the conventional original scheme, thereby increasing the pump's head and efficiency. Next, cavitation performance tests were conducted on the original scheme and the structure of this invention. The tests revealed that the critical cavitation margin of the original scheme was 3.2 m, while the critical cavitation margin of this invention was 2.5 m, an improvement of 21.88% compared to the original scheme. This demonstrates that the jet structure of this invention has better anti-cavitation performance.

Claims

1. A centrifugal impeller with high cavitation resistance and jet blades, characterized in that, The centrifugal blade (3) has a rough band at the head area near the centrifugal impeller inlet edge (1). The rough band is located on the pressure surface (5) and suction surface (7) of the centrifugal blade (3). The rough band on the pressure surface (5) of the centrifugal blade (3) is convex, and the rough band on the suction surface (7) of the centrifugal blade (3) is grooved. The convex ridge (6) and the groove (8) both include multiple channels arranged at intervals, and the convex ridge (6) and the groove (8) are arranged along the vertical direction of the centrifugal blade (3). It also includes jet blades (4), which are spiral straight blades and less than two-thirds the length of centrifugal blades (3). The number of jet blades (4) corresponds one-to-one with the number of centrifugal blades (3). The jet blades (4) are arranged close to the suction surface (7) of the centrifugal blades (3), and the spiral bending direction of the jet blades (4) and the centrifugal blades (3) is the same. The inlet edge of the jet blades (4) is close to the suction surface (7) of the centrifugal blades (3) and the distance between it and the suction surface (7) gradually decreases as the radial radius increases. The outlet edge of the jet blades (4) and the outlet edge of the centrifugal impeller blades are at the same radius as the outlet edge (2) of the centrifugal impeller.

2. The centrifugal impeller with high cavitation resistance and jet blades according to claim 1, characterized in that, The cross-section of the groove (8) is semi-circular, and the cross-section of the ridge (6) is also semi-circular. The groove (8) and the ridge (6) are positioned directly opposite each other.

3. The centrifugal impeller with high cavitation resistance and jet blades according to claim 2, characterized in that, The radii of the groove (8) and the ridge (6) are equal, and the radius is less than 1 / 2 of the thickness of the inlet edge of the centrifugal blade (3).

4. The centrifugal impeller with high cavitation resistance and jet blades according to claim 2, characterized in that, The groove (8) and the ridge (6) each include 3 to 5 grooves.

5. The centrifugal impeller with high cavitation resistance and jet blades according to claim 1, characterized in that, The inlet edge of the centrifugal blade (3) is rounded.

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