Centrifugal pump impeller structure capable of changing net positive suction head

Abstract

The utility model discloses a centrifugal pump impeller structure capable of changing the net positive suction head, which comprises a middle shaft, an inner impeller and an outer impeller, the middle shaft is arranged at an inlet of a pump shell, a power shaft penetrates through an assembly hole in the middle shaft, the inner end face of the middle shaft abuts against the inner impeller, and a fixing nut is arranged at the outer end of the middle shaft and is positioned with the outer end of the power shaft; the spiral blades are evenly distributed on the surface of the middle shaft, the inner end face and the outer end face of each spiral blade are provided with a first wedge-shaped arc face and a second wedge-shaped arc face respectively, and gaps are reserved between the inlets and the spiral blades. The centrifugal pump can solve the problems that when an existing centrifugal pump is used, the cavitation phenomenon is prone to being generated, the operation performance of the pump is reduced, and the service life is shortened.

Description

TECHNICAL FIELD

[0001] The utility model relates to centrifugal pump technical field, concretely is a centrifugal pump impeller structure of changing residual steam quantity. BACKGROUND

[0002] When the inlet pressure of centrifugal pump is equal to or less than the saturated vapor pressure of liquid under ambient temperature, steam will escape from the liquid in large quantities to form many small bubbles of steam and gas mixture, when these small bubbles flow to the high pressure area with liquid, the pressure around the bubble is greater than the saturated vapor pressure in the bubble, thereby generating pressure difference, the bubble is broken under pressure and recondenses, during the condensation process, liquid particles accelerate from all around to the center of the bubble, at the moment of condensation, particles collide with each other, generate great local pressure, cause pipeline system vibration; at the same time, these bubbles will hit the blades of the pump at high speed, cause damage to the blades, this phenomenon is called cavitation phenomenon. Pump causes cavitation during operation, energy exchange in the impeller is disturbed and destroyed, can lead to pump body vibration and noise increase, influence the working environment of workshop, also can lead to unstable pump output flow and pressure, thereby make performance parameters such as flow, lift, efficiency and power decline, influence work efficiency and benefit. Long-term work under cavitation condition can cause corrosion and damage to the overcurrent components of the pump such as pump body, blade, influence the service life of the pump. CONTENT

[0003] The utility model discloses a centrifugal pump impeller structure of changing residual steam quantity, which can effectively solve the problems of cavitation phenomenon, reduced operation performance and service life attenuation of the existing centrifugal pump in use.

[0004] In order to achieve the above object, the utility model adopts the following technical scheme: a centrifugal pump impeller structure of changing residual steam quantity, comprising:

[0005] A middle shaft is arranged at the inlet of the pump shell, a power shaft is arranged on the assembly hole in the middle shaft, the inner end surface of the middle shaft abuts on the inner impeller, and a fixed nut is arranged on the outer end of the middle shaft, and the fixed nut is positioned with the outer end of the power shaft.

[0006] A plurality of spiral blades are arranged on the surface of the middle shaft, a first wedge-shaped curved surface and a second wedge-shaped curved surface are arranged on the inner end surface and the outer end surface of the spiral blades respectively, and a gap is reserved between the inlet and the spiral blades.

[0007] Further description of the above technical scheme:

[0008] The inner end surface of the middle shaft is provided with a stepped clamping block, and the stepped clamping block is embedded in the positioning flange on the inner side of the end surface of the inner impeller.

[0009] Further description of the above technical scheme:

[0010] The stepped block is provided with a sealing ring between the positioning concave flange, the outer end of the central shaft and the fixing nut.

[0011] As a further description of the above technical solution:

[0012] The spiral blade is provided with four.

[0013] As a further description of the above technical solution:

[0014] The included angle of the spiral blade on the outer side is 1°.

[0015] As a further description of the above technical solution:

[0016] The included angle of the spiral blade from the inlet edge to the outlet edge is 3°±1°.

[0017] As a further description of the above technical solution:

[0018] The cross section of the first wedge-shaped camber and the second wedge-shaped camber gradually decreases from inside to outside, and the included angle between the two is 5°.

[0019] As a further description of the above technical solution:

[0020] The inner wall of the inlet is a tapered surface with gradually decreasing size from outside to inside.

[0021] As described above, compared with the prior art, the utility model has the following

[0022] Beneficial effects:

[0023] The liquid suction performance and anti-cavitation performance of the impeller structure of the utility model are significantly improved after being assembled with the centrifugal pump, the vibration noise of the centrifugal pump is reduced, the operation is stable, the probability of cavitation phenomenon of the centrifugal pump is effectively reduced, the net positive suction head of the water pump can be reduced through the spiral flow of the device, the inlet pressure of the water pump is improved, and the anti-cavitation performance of the water pump is improved; meanwhile, the capacity of the water pump for conveying viscous materials can be improved, and the service life of the impeller, the pump body and the cover plate and other flow components can be prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical scheme of the embodiments of the utility model, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the utility model, and should not be regarded as a limitation to the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of the drawings.

[0025] Fig. 1It is a partial sectional view of a centrifugal pump impeller structure for changing a cavitation margin.

[0026] Fig. 2 It is an assembly structure sectional view of a centrifugal pump impeller structure for changing a cavitation margin.

[0027] Legend:

[0028] 1, central shaft; 2, assembly hole; 3, spiral blade; 4, first wedge-shaped camber; 5, second wedge-shaped camber; 6, stepped clamping block; 10, pump shell; 11, inlet; 12, power shaft; 13, inner impeller; 14, fixed nut. DETAILED DESCRIPTION

[0029] The technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0031] Please refer to Figs. 1-2 The present application provides a technical scheme: a centrifugal pump impeller structure for changing a cavitation margin, comprising:

[0032] The central shaft 1 is arranged at the inlet 11 of the pump shell 10, the assembly hole 2 in the central shaft 1 is provided with the power shaft 12, the inner end surface of the central shaft 1 abuts against the inner impeller 13, and the outer end of the central shaft 1 is provided with the fixed nut 14, and the fixed nut 14 is positioned with the outer end of the power shaft 12.

[0033] The plurality of spiral blades 3 are uniformly distributed on the surface of the central shaft 1, the first wedge-shaped camber 4 and the second wedge-shaped camber 5 are respectively arranged on the inner end surface and the outer end surface of the spiral blade 3, and a gap is left between the inlet 11 and the spiral blade 3.

[0034] The inner end surface of the central shaft 1 is provided with the stepped clamping block 6, the stepped clamping block 6 is embedded in the positioning flange on the inner side of the end surface of the inner impeller 13, and the assembly strength of the spiral blade 3 and the centrifugal pump is improved.

[0035] The stepped block 6 is provided with a sealing ring between the positioning flange, the outer end of the central shaft 1 and the fixing nut 14.

[0036] The four spiral vanes 3 are evenly distributed, and the index error is not greater than ±15'.

[0037] The included angle of the outer spiral vane 3 is 1°.

[0038] The included angle of the inlet edge to the outlet edge of the spiral vane 3 is 3°±1°.

[0039] The cross section of the first wedge-shaped camber 4 and the second wedge-shaped camber 5 gradually decreases from inside to outside, and the included angle between them is 5°.

[0040] The inner wall of the inlet 11 is a tapered surface with gradually decreasing size from outside to inside.

[0041] The working principle of the centrifugal pump impeller structure of the embodiment for adjusting the net positive suction head includes: the spiral impeller structure is arranged at the inlet of the centrifugal pump and the liquid inlet end of the inner impeller 13, so that the generated head of the spiral impeller structure pressurizes the following centrifugal inner impeller 13. The spiral impeller structure only needs a low suction head, and then the fluid can be pumped in, which improves the fluid suction performance of the entire pump. When the conventional centrifugal pump impeller is used, when the cavitation develops to a certain extent, it will obviously affect the liquid pumping performance of the centrifugal pump. This is because the liquid in the flow passage of the centrifugal impeller flows from the axial direction to the radial direction (mainly in the radial direction). Because the density of the liquid is greater than that of the gas, under the action of the centrifugal force, the cavitation in the liquid flow is easily separated out and rapidly expanded to block the flow passage, so that the suction performance of the pump is rapidly deteriorated. The flow passage between the spiral impeller structure is relatively long, and mainly provides an axial guiding effect on the liquid. The relative flow rate is the largest at the outer edge of the impeller, so cavitation first occurs at the outer edge of the impeller. The liquid near the hub center is compressed by the centrifugal force, which compresses the cavitation at the outer edge, so that it can only move axially along the outer edge and collapse after entering the high-pressure area. This greatly limits the development of cavitation, thereby adjusting the net positive suction head at the inlet end of the centrifugal pump and improving the anti-cavitation performance of the centrifugal pump. Only when all the flow passages of the device are filled with cavitation (at this time, the centrifugal impeller also occurs cavitation and flow is interrupted), the working state of the pump is destroyed.

[0042] When the conventional centrifugal impeller is used, the liquid rapidly turns the direction when entering the blade head, the flow rate increases, and thus the pressure decreases, which easily causes cavitation, separates the gas from the liquid, and after the cavitation is generated, the centrifugal impeller cannot limit the development thereof, because the flow direction of the liquid in the impeller is along the direction of the centrifugal force, the liquid is thrown outward at high speed under the action of the centrifugal force, and the bubbles move inward, thereby accelerating the separation of the gas from the liquid.

[0043] In summary, due to the adoption of the technical scheme, the centrifugal pump impeller structure for changing the cavitation margin has the following beneficial effects compared with the prior art:

[0044] After the impeller structure is assembled with the centrifugal pump, the liquid suction performance and cavitation resistance are significantly improved, the vibration noise of the centrifugal pump is reduced, the operation is stable, the probability of cavitation phenomenon of the centrifugal pump is effectively reduced, the spiral flow flowing out of the device can reduce the net positive suction head of the water pump, improve the inlet pressure of the water pump, and thus improve the cavitation resistance of the water pump; meanwhile, the capacity of the water pump for conveying viscous materials can be improved, and the service life of the flow parts such as the impeller, the pump body and the cover plate is prolonged.

[0045] The above is only a preferred specific implementation manner of the utility model, but the protection scope of the utility model is not limited to this, any skilled person in the art can make equivalent replacement or change according to the technical scheme and the utility model concept of the utility model within the technical range disclosed by the utility model, which should be covered in the protection scope of the utility model.

Claims

1. A centrifugal pump impeller structure with altered net positive suction head (NPSH), characterized in that, include: The central shaft is located at the inlet of the pump casing. A power shaft passes through the mounting hole inside the central shaft. Its inner end face abuts against the inner impeller. A fixing nut is provided at its outer end, and the fixing nut is positioned with the outer end of the power shaft. Several helical blades are evenly distributed on the surface of the central shaft. A first wedge-shaped arc surface and a second wedge-shaped arc surface are respectively provided on the inner end face and the outer end face. A gap is left between the inlet and the helical blades.

2. The centrifugal pump impeller structure with altered net positive suction head (NPSH) according to claim 1, characterized in that, The inner end face of the central shaft is provided with a stepped locking block, which is embedded in the positioning recess on the inner side of the inner impeller end face.

3. The centrifugal pump impeller structure with altered net positive suction head (NPSH) according to claim 2, characterized in that, A sealing ring is provided between the stepped locking block and the positioning recess, and between the outer end of the central shaft and the fixing nut.

4. The centrifugal pump impeller structure for changing net positive suction head (NPSH) according to claim 1, characterized in that, The spiral blades are configured with 4.

5. The centrifugal pump impeller structure for changing net positive suction head (NPSH) according to claim 1, characterized in that, The outer spiral blade has a wrap angle of 1°.

6. The centrifugal pump impeller structure with altered net positive suction head (NPSH) according to claim 1, characterized in that, The wrap angle between the inlet and outlet sides of the spiral blade is 3°±1°.

7. The centrifugal pump impeller structure with altered net positive suction head (NPSH) according to claim 1, characterized in that, The distance between the cross sections of the first and second wedge-shaped arc surfaces gradually decreases from the inside to the outside, and the included angle between them is 5°.

8. The centrifugal pump impeller structure for changing net positive suction head (NPSH) according to claim 1, characterized in that, The inner wall of the inlet is a tapered surface whose dimensions gradually decrease from the outside to the inside.

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