Axial flow pump double-layer flow channel structure capable of resisting blade top leakage

Abstract

The invention discloses an axial flow pump double-layer flow channel structure capable of resisting blade top leakage. The axial flow pump double-layer flow channel structure comprises an inlet outer cylinder, an outlet outer cylinder and an impeller. An inlet inner cylinder is arranged on the inner side of the inlet outer cylinder, a circulation channel A is formed between the inlet outer cylinder and the inlet inner cylinder, a double-layer flow channel partition plate is arranged on the inner side of the outlet outer cylinder, and a circulation channel B is formed between the double-layer flow channel partition plate and the outlet outer cylinder; front guide vanes are evenly arranged on the outer wall of the inlet inner cylinder in the circumferential direction, and rear guide vanes are evenly arranged on the outer wall of the double-layer flow channel partition plate in the circumferential direction. A double-inlet structure is innovatively designed, during double inlets, leakage flow is restrained, most of the leakage flow acts on main flow in a gap between the inner cylinder and the outer cylinder, the flowing direction of the main flow in the inner cylinder is basically consistent with the axis, and the main flow in the inner cylinder is distributed uniformly; therefore, the double-inlet structural form can restrain the main reason of the unstable characteristic of flow and lift of the axial flow pump, and the flow field distribution on the upstream of the blade inlet edge is protected.

Description

Technical Field

[0001] The invention relates to the technical field of axial flow pumps, and in particular to a double-layer flow channel structure of an axial flow pump that resists blade tip leakage. Background Art

[0002] Axial flow pump is a main product of axial flow fluid machinery, with the characteristics of simple structure and light weight. It has a wide range of applications, especially suitable for large flow and low head occasions. One-third of the total electricity consumption in the society is used to drive water pumps, fans and compressors, and axial flow pumps occupy an important share in this.

[0003] The tip clearance is located between the blades of the working components and the leading edge end face of the impeller. There is a pressure difference between the pressure surface and the suction surface of the blade. The relative movement between the rotor blades and the leading edge end wall will produce tip leakage flow in the clearance area under the joint action of the two. The stable operation of the spiral mixed flow pump is deeply affected by the tip leakage vortex structure, which is formed by the mixing of the tip leakage flow and the mainstream in the flow channel. Under the action of the blade pressure difference, the gap leakage flow flows from the higher pressure side flow channel to the lower pressure side flow channel through the tip clearance area. When the central pressure of the leakage vortex reaches the saturated vaporization pressure, leakage vortex cavitation occurs inside the impeller.

[0004] Leakage vortex cavitation will not only cause the external characteristics of the pump to drop sharply, but also lead to the aggravation of cavitation inside the pump, causing cavitation erosion on the impeller blades and serious damage to the flow-through components, resulting in a series of safety problems. Summary of the invention

[0005] In view of the shortcomings of the existing axial flow pump impeller components, the purpose of the present invention is to provide a double-layer flow channel structure of an axial flow pump that is resistant to blade tip leakage, so as to effectively suppress the intensity and size of the vortex formed by the leakage flow at the front end of the blade inlet edge, reduce the impact of leakage on the mainstream, thereby effectively improving the flow field at the front end of the blade inlet edge, increasing the head under small flow rates and reducing the positive slope of the head curve in the unstable zone, expanding the flow range, and controlling the vortex size in the impeller, suppressing pressure pulsation, improving the anti-cavitation performance of the centrifugal pump, and increasing the life of the pump.

[0006] The technical solution of the present invention is as follows:

[0007] A double-layer flow channel structure of an axial flow pump with an anti-blade tip leakage function, comprising an inlet outer cylinder, an outlet outer cylinder and an impeller; an inlet inner cylinder is provided on the inner side of the inlet outer cylinder, and a flow channel A is provided between the inlet outer cylinder and the inlet inner cylinder; a double-layer flow channel baffle is provided on the inner side of the outlet outer cylinder, and a flow channel B is provided between the double-layer flow channel baffle and the outlet outer cylinder; leading guide vane blades are evenly arranged on the outer wall of the inlet inner cylinder in the circumferential direction, and trailing guide vane blades are evenly arranged on the outer wall of the double-layer flow channel baffle in the circumferential direction.

[0008] Furthermore, the impeller includes a guide cone and impeller blades, and the impeller blades are evenly arranged around the guide cone. The guide cone is streamlined and has a conical shape, similar to a bullet head.

[0009] Furthermore, the inlet inner cylinder is located in front of the impeller blades, and the double-layer flow channel baffle is located behind the impeller blades. Preferably, the position of the inlet inner cylinder starts at 0.05L1 in front of the projection of the impeller blade inlet side axial surface, and the position of the double-layer flow channel baffle starts at 0.02L3 behind the projection of the blade outlet side axial surface, wherein L1 is the inlet flow channel length, and L3 is the outlet flow channel length.

[0010] Furthermore, the front guide vane blade is arranged perpendicular to the cross section of the flow channel A, and the angle between the projection of the front line of the rear guide vane blade cascade on the plane passing through the axis center and the axis is:

[0011]

[0012] Among them, c 2u is the impeller blade outlet rotation speed, c 3u is the outlet swirl speed of the trailing guide vane, c a is the axial component of the absolute airflow velocity.

[0013] Furthermore, the number of the front guide vane blades and the number of the rear guide vane blades is not a common multiple of the number of the impeller blades.

[0014] Furthermore, the inner side of the double-layer flow channel partition is evenly provided with a pit structure A near the impeller blade side, and the inner side of the inlet inner tube is evenly provided with a pit structure B near the impeller blade side.

[0015] Furthermore, the pit structure A and the pit structure B are the same in structure, and a convex hull structure is provided in the middle of the pit structure A and the pit structure B respectively.

[0016] Furthermore, the width of the front guide vane is equal to the width of the circulation channel A, and the width of the rear guide vane is equal to the width of the circulation channel B.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention innovatively designs a double inlet structure. When there are double inlets, the leakage flow is constrained, and most of it acts on the mainstream in the gap between the inner and outer cylinders, while the mainstream flow direction in the inner cylinder is basically consistent with the axis, and the distribution is relatively uniform. Therefore, the main reason why the double inlet structure can suppress the unstable characteristics of the flow-head of the axial flow pump is that it protects the flow field distribution upstream of the blade inlet edge;

[0019] 2. The present invention aims at the "Y" type flow channel, and adds a double-layer flow channel baffle at the rear outlet of the impeller. The influence principle of the double-layer flow channel on the head is the same as that of the double inlet, and solves the flow optimization problem of different parts in the pump. For the submersible axial flow pump actually used in the project, the water inlet is usually directly installed in the water, and the gap between the double inlets is generally small, which can improve the performance of the pump under small flow non-design conditions;

[0020] 3. The guide cone structure designed in the present invention is streamlined, so that the flow cross-section increases evenly with the direction of water flow, eliminating the turbulence of water flow, and the uniformity of flow velocity distribution and the average angle of water flowing into the pump are high, which plays a rectifying role. The guide cone can also reduce hydraulic loss;

[0021] 4. The inlet inner cylinder and the partition of the present invention are evenly distributed with pits near the impeller, and a small convex hull structure is designed in the pit. When the fluid passes through, a vortex will appear on the wall of the pit, which will intensify the turbulence inside the boundary layer and not spread to the center; the "vortex cushion effect" generated between the vortex and the mainstream should be changed from sliding friction to similar rolling friction. The rolling friction resistance is smaller than the sliding friction resistance, which reduces the momentum required for the incoming flow to overcome the friction resistance. It improves its ability to resist adverse pressure gradients, delays flow separation, reduces the low-pressure area formed at this position, and thus reduces the pressure difference resistance. The convex height of the small convex hull causes the fluid to flow around the convexity, reduces the velocity gradient of the inlet and outlet, and reduces the turbulence intensity. At the same time, the generated vortex cushion is pushed to the center of the boundary layer, reducing the internal friction of the small vortex, stabilizing the larger vortex, and further reducing the flow resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a general schematic diagram of an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the interior of an embodiment of the present invention after removing the outer cylinder;

[0024] Figure 3 is a diagram showing the position relationship between the pit and the inner cylinder of an embodiment of the present invention;

[0025] Figure 4 is a diagram showing the relationship between the positions of the pits and the partitions in an embodiment of the present invention;

[0026] Figure 5 is a schematic diagram of the tail pit structure of an embodiment of the present invention;

[0027] Figure 6 1 is a comparison diagram of the effects of the embodiments of the present invention;

[0028] In the figure, 1-double-layer flow channel baffle, 2-rear guide vane blade, 3-inlet inner cylinder, 4-front guide vane blade, 5-guide cone, 6-impeller blade, 7-inlet outer cylinder, 8-outlet outer cylinder, 101-pit structure A, 301-pit structure B, 1011-convex hull structure. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings:

[0030] like Figure 1 As shown, the double-layer flow channel structure of the axial flow pump with anti-blade tip leakage includes a double-layer flow channel baffle 1, a rear guide vane blade 2, an inlet inner cylinder 3, a front guide vane blade 4, a guide cone 5, an impeller blade 6, an inlet outer cylinder 7, and an outlet outer cylinder 8;

[0031] The guide cone 5 and the impeller blades 6 constitute an impeller, wherein the impeller blades 6 are welded together with the guide cone 5. The guide cone is streamlined, with an axial length L4=0.5L0, and a length L0=K of the inlet inner cylinder 3. L0 ×L1.

[0032] A conical shell component is provided in the middle of the conical space of the double-layer flow channel partition 1, and a motor is arranged inside to drive the impeller to rotate. At the same time, the outer wall and the outlet outer cylinder 8 form a flow channel, which is separated by the double-layer flow channel partition 1.

[0033] like Figure 1 As shown, when the axial flow pump is running, the fluid flows in from the inlet outer cylinder 7. At this time, the motor converts electrical energy into mechanical energy and drives the impeller to rotate, using centrifugal force to accelerate the fluid, so that the fluid flows out of the impeller from the flow channel between the outlet outer cylinder 8, completing the fluid transportation.

[0034] like Figure 2 As shown, the inlet inner cylinder 3 is located in front of the impeller blades 6, starting from 0.05L1 in front of the axial projection of the blade inlet edge, and the leading guide vanes 4 are evenly arranged on the outer wall of the inlet inner cylinder 3, and the leading guide vanes 4 are arranged perpendicular to the flow channel cross section; the inlet inner cylinder 3, the leading guide vanes 4 and the inlet outer cylinder are welded together.

[0035] The length of the inlet inner tube 3 is L0 = K L0 × L1, thickness of inlet inner tube 3 B0 = K B0 ×B1; where L1 is the inlet flow channel length, K L0 is the inner tube length coefficient, K L0 Take 0.75~0.8, B1 is the thickness of the imported outer cylinder, K B0 is the inner tube thickness coefficient, K B0 Take 0.095~0.105;

[0036] The double-layer flow channel baffle 1 is located at the rear side of the impeller blade 6, starting from 0.02L3 behind the axial projection of the blade outlet edge, and the rear guide vanes 2 are evenly arranged on the outer wall of the double-layer flow channel baffle 1. The double-layer flow channel baffle 1, the rear guide vanes 2 and the outlet outer tube 8 are welded together.

[0037] The angle between the projection of the front line of the trailing guide vane cascade on the plane passing through the axis center and the axis is Among them, c 2u is the swirl velocity at the impeller blade outlet (rear guide vane inlet), c 3u is the outlet swirl speed of the trailing guide vane, c a is the axial component of the absolute velocity of the airflow;

[0038] The length of the double-layer flow channel baffle 1 is L2 = K L2 × L3, the thickness of the partition B2 = B0, where L3 is the outlet flow length, K L2 is the inner tube length coefficient, K L2 Take 0.85~0.9.

[0039] like Figure 2 As shown, the width of the flow channel between the inlet inner tube 3 and the inlet outer tube 7 is the front guide vane width b, and the width of the flow channel between the double-layer flow channel baffle 1 and the outlet outer tube 8 is the rear guide vane width b. The front and rear guide vane widths b = K b D, where D is the outer diameter of the impeller, k b is the guide vane width coefficient, k b Take 0.0175~0.025. The thickness of the front and rear guide vanes B3=0.1B0; the number of the front and rear guide vanes should avoid being a common multiple of the number of the impeller blades.

[0040] like Figure 2 As shown, the double-layer flow channel structure of the axial flow pump with anti-blade tip leakage is characterized in that: when the fluid flows to the impeller blades 6, due to the presence of the inlet inner tube 3, the intensity and size of the vortex formed at the front end of the impeller blade inlet edge due to the blade tip leakage are effectively suppressed, and the influence of the leakage on the mainstream is reduced, thereby effectively improving the flow field at the front end of the blade inlet edge, increasing the head under small flow and reducing the positive slope of the head curve in the unstable area, thereby expanding the flow range.

[0041] like Figure 3 , Figure 4 and Figure 5 As shown, a pit structure A101 and a pit structure B301 are arranged on the inner side of the double-layer flow channel baffle 1 and the inlet inner tube 3 near the impeller blade 6; a convex hull structure 1011 is arranged between the pit structure A101 and the pit structure B301, the pit diameter d=0.06B0, the pit depth h=0.02B0, and the convex hull structure radius r=0.01B0.

[0042] like Figure 3 , Figure 4 and Figure 5As shown, the pit structure A101 and the pit structure B301 are evenly distributed, and a convex hull structure 1011 is designed inside the pit structure. When the fluid passes through, a vortex will appear on the wall of the pit structure, which will intensify the turbulence inside the boundary layer and not spread to the center; the "vortex cushion effect" generated between the vortex and the mainstream should be changed from sliding friction to similar rolling friction. The rolling friction resistance is smaller than the sliding friction resistance, which reduces the momentum required for the incoming flow to overcome the friction resistance. It improves its ability to resist the adverse pressure gradient, delays flow separation, reduces the low pressure area formed at this position, and thus reduces the pressure difference resistance. The convex height of the convex hull structure 1011 causes the fluid to flow around the convexity, reduces the velocity gradient at the blade outlet, reduces the turbulence intensity, and at the same time, pushes the generated vortex cushion to the center of the boundary layer, reduces the internal friction of small vortices, stabilizes larger vortices, and can further reduce the flow resistance.

[0043] Comparison of the pressure cloud diagram at the guide vane outlet corner before and after the double-layer flow channel is installed. Figure 6 As shown; combined with the streamline diagram, it can be seen that the high-pressure area of ​​the double-layer flow channel pump is significantly reduced, indicating that the flow velocity is increased, the adverse pressure gradient is weakened, the conditions for flow separation are weakened, and the internal flow at large flow rates is utilized.

[0044] The above embodiments are only preferred embodiments of the present invention and are not limitations of the technical solutions of the present invention. Any technical solution that can be implemented on the basis of the above embodiments without creative work should be deemed to fall within the scope of protection of the patent of the present invention.

Claims

1. A double-layer flow channel structure of an axial flow pump for preventing tip leakage, comprising an inlet outer cylinder (7), an outlet outer cylinder (8) and an impeller; It is characterized in that An inlet inner cylinder (3) is arranged on the inner side of the inlet outer cylinder (7), and a circulation channel A is arranged between the inlet outer cylinder (7) and the inlet inner cylinder (3); a double-layer flow channel baffle (1) is arranged on the inner side of the outlet outer cylinder (8), and a circulation channel B is arranged between the double-layer flow channel baffle (1) and the outlet outer cylinder (8); front guide vane blades (4) are evenly arranged on the circumference of the outer wall of the inlet inner cylinder (3), and rear guide vane blades (2) are evenly arranged on the circumference of the outer wall of the double-layer flow channel baffle (1).

2. According to claim 1, a double-layer flow channel structure of an axial flow pump for preventing tip leakage, It is characterized in that The impeller comprises a guide cone (5) and impeller blades (6), and the impeller blades (6) are evenly arranged in the circumferential direction of the guide cone (5).

3. The double-layer flow channel structure of an axial flow pump for preventing tip leakage according to claim 1, It is characterized in that The inlet inner cylinder (3) is located in front of the impeller blades (6), and the double-layer flow channel partition (1) is located in the rear of the impeller blades (6).

4. The double-layer flow channel structure of an axial flow pump for preventing tip leakage according to claim 1, It is characterized in that The front guide vane blade (4) is arranged perpendicular to the cross section of the flow channel A, and the angle between the rear guide vane blade (2) and the generatrix is: Among them, c 2u is the impeller blade outlet rotation speed, c 3u is the outlet swirl speed of the trailing guide vane, c a is the axial component of the absolute airflow velocity.

5. The double-layer flow channel structure of an axial flow pump for preventing tip leakage according to claim 1, It is characterized in that The number of the front guide vane blades (4) and the number of the rear guide vane blades (2) are not common multiples of the number of the impeller blades (6).

6. The double-layer flow channel structure of an axial flow pump for preventing tip leakage according to claim 1, It is characterized in that The inner side of the double-layer flow channel partition (1) is evenly provided with a pit structure A (101) near the impeller blade (6), and the inner side of the inlet inner tube (3) is evenly provided with a pit structure B (301) near the impeller blade (6).

7. The double-layer flow channel structure of an axial flow pump for preventing tip leakage according to claim 6, It is characterized in that A convex hull structure (1011) is respectively disposed in the middle of the concave structure A (101) and the concave structure B (301).

8. The double-layer flow channel structure of an axial flow pump for preventing tip leakage according to claim 1, It is characterized in that The width of the front guide vane blade (4) is equal to the width of the circulation channel A, and the width of the rear guide vane blade (2) is equal to the width of the circulation channel B.

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