CN116104764A

CN116104764A - Centrifugal pump

Info

Publication number: CN116104764A
Application number: CN202310203437.4A
Authority: CN
Inventors: 陈永生
Original assignee: Hunan Genda Fiber Science Machinery Manufacturing Co ltd
Current assignee: Hunan Genda Fiber Science Machinery Manufacturing Co ltd
Priority date: 2023-03-03
Filing date: 2023-03-03
Publication date: 2023-05-12

Abstract

The invention discloses a centrifugal pump, comprising: the impeller comprises n blades, an impeller runner is formed between every two adjacent blades, a volute runner with a rectangular cross section is arranged on the inner periphery of the impeller shell, a ring-shaped guide ring is arranged between the inner ring of the volute runner and the outer diameter of the impeller, the ring-shaped guide ring comprises m guide blades, and a guide runner is formed between every two adjacent guide blades; n and m are positive integers. The centrifugal pump has the advantages of compact structure, convenient installation, high reliability, low kinetic energy loss and the like, and can greatly reduce vortex formed in the flow passage of the pump, thereby greatly improving the overall efficiency of the pump.

Description

Centrifugal pump

Technical Field

The invention belongs to the technical field of centrifugal pump equipment for conveying liquid, and particularly relates to a centrifugal pump.

Background

Centrifugal pumps are very important in national economy development, and are indispensible in industrial and agricultural production or people's life. The variety and specification are very various due to different special purposes, but in the important equipment with long history, people hardly perceive that a plurality of high-energy consumption products exist, and some centrifugal pumps with low specific rotation speed have the operation efficiency of less than 75 percent, namely, the single-stage and single-suction centrifugal pump with the maximum consumption has the efficiency of only (60-80 percent), and even the centrifugal pump with the efficiency of less than 60 percent is produced in various large water pump factories. For China with a relatively short energy source, a great amount of resource waste is indeed caused, and unnecessary economic loss is brought to users in an intangible way.

The structure and water outlet principle of the existing centrifugal pump is shown in figures 1 and 2,

is tangent to point A, u ₂ Is the circumferential velocity, W ₂ Is the relative velocity of water flow at the blade outlet, and the included angle between the water flow and the tangent line of the blade is beta ₂ This speed is synthesized as absolute speed C ₂ ，C ₂ An included angle alpha with the tangent line ₂ . As can be seen in FIG. 1, the flow of water from the impeller outlet takes a particle A along the absolute velocity C ₂ During spraying, water sprayed by the blades is also moved forwards to the +.>

When the line is collided with the spiral case again, water impact, deflection and reflection are generated. The flow dynamics shows that the process of moving the high-speed fluid from the point A to the intersection point of the spiral case is called as a undercurrent, and the water sprayed from the circumference of the impeller looks like a round cake, and the radius is continuously increased in the spraying process, so that the round cake can form a dense round brush. After reaching the wall of the spiral case, the full circumferential water flow can generate strong water hammer, baffling and reflection and then is converged into low-speed fluid at two sides of the annular flow passage. And because the impeller rotating speed of the high-pressure pump is high, the speed of the impeller is 5 times or more of the flow speed in the annular flow passage. Because the high-pressure pump is thinner in water cake, the flow speed is high, and strong vortex can be generated. The most significant impact is water hammer and deflection, and the flow is first submerged and then severely water hammer, deflection and reflection before it is directed to the volute wall, which consumes significant kinetic energy of the fluid. The angle theta of the fluid striking the wall surface at the time of deflection is about 42 DEG, the resistance coefficient is 0.0726 when the included angle theta is 30 DEG, and the resistance coefficient is 0.1553 when the included angle theta is 42 DEG, namely about 15.5 percent of the total height of the pump lift is lost, so that the main reason for the inefficiency of the high-pressure pump is generated in the idle work, of courseThere is also a reflected energy consumption after deflection. As for how much water impact is lost during the moment that the water sprayed by the impeller is rushed to the wall of the volute, the "visbach" formula can be used, and when the angle θ is 90 °, i.e. the right-angle spraying, the resistance coefficient obtained by the formula is 0.9855, i.e. almost 100% of the kinetic energy of the fluid is consumed, which is the same as the energy loss that we observe that the water flow is perpendicularly directed to the plate surface. This is not an energy conversion, which is all energy loss. Because the fluid cannot do work after being directed to the vertical plate surface, all kinetic energy is consumed. The water hammer caused by the oblique jet is of course dependent on the water flow angle and the flow rate. The higher the head, the higher the pump flow rate Gao and the more the above losses. This is the biggest drawback of modern centrifugal pumps.

The impeller structure of the conventional centrifugal pump has a disadvantage that the diffusion angle between the blades is too large, because the fluid is acted by the centrifugal force in the impeller flow channel and the tangential force opposite to the rotation direction, and the fluid can flow closely to the working surface of the blades under the influence of the coriolis force, and a negative pressure cavity area is formed near the non-working surface. Because of the existence of this negative pressure cavitation zone, the fluid at the large radius between the blades has only centrifugal force and no suction effect on the inlet fluid, because this negative pressure cavitation zone easily sucks the high pressure fluid outside the impeller to generate vortex. The area of the diffusion angle between the flow channels is not full of fluid, so that the suction force to the inlet of the impeller cannot be exerted. The fluid entering the runner can only rely on the centrifugal force generated by the fluid at the small radius of the runner of the impeller to suck the fluid at the inlet of the impeller, and the fluid at the large radius has only centrifugal force and no suction force, thus causing the adverse effect of lower water lift of the centrifugal pump.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the centrifugal pump which has the advantages of compact structure, easy installation, high reliability and low kinetic energy loss.

In order to solve the technical problems, the invention adopts the following technical scheme:

a centrifugal pump, comprising: the impeller comprises n blades, an impeller runner is formed between every two adjacent blades, a volute runner with a rectangular cross section is arranged on the inner periphery of the impeller shell, a ring-shaped guide ring is arranged between the inner ring of the volute runner and the outer diameter of the impeller, the ring-shaped guide ring comprises m guide blades, and a guide runner is formed between every two adjacent guide blades; n and m are positive integers.

As a further improvement of the invention, the overlap length between adjacent guide vanes is a ₁ The length of the single guide vane is a ₂ ，a ₁ ＞(a ₂ /2)。

As a further improvement of the invention, the normal width of the outlet of the diversion flow passage is c, and the throat width of the volute flow passage is d, and d is approximately equal to (m-1) multiplied by c.

As a further improvement of the invention, the inner cavity of the cross section of the annular guide ring is in a horn shape from inside to outside.

As a further improvement of the invention, the water inlet width b of the annular guide ring ₁ The width b of the water outlet is larger than that of the impeller ₂ To compensate for installation deviations; the width of the water outlet of the annular guide ring is equal to the axial width of the volute flow channel.

As a further improvement of the invention, the radial width of the volute flow channel is gradually widened from the front edge of the partition tongue to the throat part according to the Archimedes spiral rule, the axial width of the volute flow channel is the same as the width of the throat part, and the cross section of the volute flow channel at the throat part is approximately square.

As a further improvement of the invention, the cross section of the volute runner gradually transits from square to round from the throat to the water outlet.

As a further improvement of the invention, the water inlet angle of the guide vane and the absolute speed C in the triangle of the water outlet of the vane ₂ Equidirectional and equiangular; the water outlet angle of the guide vane is equal to the spiral line angle of the outer edge wall of the pump shell.

As a further improvement of the invention, the guide vane is an approximately long trapezoid vane after being unfolded.

As a further development of the invention, the impeller flow channel has almost no diffusion angle, the outlet arc length of the impeller flow channel is equal to or slightly wider than the inlet arc length, and the redundant fan-shaped area is covered by the thickening of the outlet end of the blade.

Compared with the prior art, the invention has the advantages that:

1. according to the centrifugal pump, the impeller is arranged in the pump shell, the volute annular flow passage with the rectangular cross section is arranged at the inner periphery of the pump shell, and the annular flow guide ring is arranged at the position, close to the water inlet, in the volute flow passage, namely the annular flow guide ring is arranged at the outer periphery of the water outlet of the impeller, so that the centrifugal pump which is compact in structure, easy to install, high in reliability and low in kinetic energy loss is obtained; the fluid to be conveyed is sucked into the impeller from the water inlet, is output into the annular guide ring from the impeller, and is finally output into the volute flow channel from the guide ring flow channel, the annular guide ring has the function of a plurality of pairs of 'surface pressing rollers' to 'press' the water column at the inlet of the annular guide ring into a strip of thin 'water belt', and the strip of thin 'water belt' is respectively overlapped into a whole at the same speed and then stably flows forwards, so that the idle work phenomenon caused by the undercurrent, the water hammer and the baffling existing in the conventional centrifugal pump is thoroughly eliminated, and the operation efficiency of the high-pressure pump or the medium-pressure pump is unprecedentedly improved.

2. The centrifugal pump of the invention designs the cross section of the volute flow passage into a rectangular structure, gradually increases the radial width of the volute flow passage from the partition tongue to the throat according to the Archimedes spiral rule, keeps the same width with the throat in the axial width of the volute flow passage, and the cross section of the volute flow passage is slightly square, and gradually transits into a circular structure from the throat to the water outlet, thereby effectively avoiding the transverse migration and mutual dislocation disturbance of fluid in the volute flow passage, ensuring that the fluid is uniformly filled in the volute flow passage, and improving the stability of fluid transportation and the water absorption and lift of the centrifugal pump.

Drawings

Fig. 1 is a schematic diagram of the structural principle of a conventional centrifugal pump.

Fig. 2 is a schematic diagram of the water discharge principle of a conventional centrifugal pump.

Fig. 3 is a schematic structural diagram of the centrifugal pump of the present invention.

Fig. 4 is a schematic view of a schematic partially cut-away structure of a centrifugal pump according to another view of the present invention.

Fig. 5 is a schematic diagram of the structural principle at D in fig. 4.

Fig. 6 is a schematic diagram of the principle of the present invention in the water outlet in the specific application example.

Legend description: 1. a pump housing; 2. a main shaft; 3. an impeller; 31. a blade; 32. an impeller runner; 4. an annular guide ring; 41. a guide vane; 42. a diversion flow passage; 5. a base; 6. a water outlet; 7. a water inlet; 8. a volute flow passage.

Detailed Description

The invention is further described below in connection with the drawings and the specific preferred embodiments, but the scope of protection of the invention is not limited thereby.

Examples

As shown in fig. 3 to 6, the centrifugal pump of the present invention includes: the impeller pump comprises a pump shell 1 and an impeller 3 arranged in the pump shell 1, wherein a base 5 is arranged at the bottom of the pump shell 1, the impeller 3 is connected with a main shaft 2 and is driven by the main shaft 2 and a driving part to rotate, and the working surface of the impeller 3 faces to a water inlet 7. The impeller 3 comprises n blades 31, and impeller flow passages 32 are formed between adjacent blades 31; the impeller flow channel 32 has almost no diffusion angle, the outlet arc length of the impeller flow channel 32 is almost equal to the inlet arc length or the outlet arc length is slightly larger than the inlet arc length, the redundant fan-shaped area is covered by the thickening of the outlet end of the blade 31, and the impeller flow channel 32 is made into the same width as the inlet. The inner periphery of the pump shell 1 is provided with a volute flow channel 8 with a rectangular cross section, a ring-shaped guide ring 4 is arranged between the inner ring of the volute flow channel 8 and the outer diameter of the impeller 3, the ring-shaped guide ring 4 comprises m guide vanes 41, and a guide flow channel 42 is formed between every two adjacent guide vanes 41; n and m are positive integers. It will be appreciated that in order to increase the rigidity of the annular deflector ring 4, the annular deflector ring 4 may be manufactured from a metallic material such as ductile iron.

It will be appreciated that the impeller flow passage 32 is not preferably configured with an excessively large diffusion angle, and that, strictly speaking, several undesirable conditions in the operation of the centrifugal pump (e.g., overload, hump, cavitation) are associated with the diffusion angle of the impeller flow passage 32. Therefore, the above-mentioned adverse conditions can be eliminated or greatly reduced by making the inlet and outlet widths of the impeller flow passage 32 nearly equal or slightly divergent.

In this embodiment, by installing the impeller 3 in the pump casing 1, and arranging the volute flow channel 8 with rectangular cross section on the inner periphery of the pump casing 1, and arranging a ring-shaped guide ring 4 in the volute flow channel 8 at a position close to the water inlet 7, that is, between the inner ring of the volute flow channel 8 and the outer diameter of the impeller 3, that is, arranging the ring-shaped guide ring 4 on the outer periphery of the water outlet of the impeller 3, the phenomena of undercurrent, water hammer, baffling and the like of fluid in the pump casing are thoroughly eliminated, and the centrifugal pump with compact structure, easy installation, high reliability and low kinetic energy loss is obtained. The fluid to be conveyed is sucked into the impeller 3 through the water inlet 7, is output into the annular guide ring 4 through the impeller 3, is output into the volute runner 8 through the guide runner 42 of the annular guide ring, and is finally output through the water outlet 6, and the whole process is free from interference and steadily flows forwards; the annular guide ring 4 has the function of a plurality of pairs of 'surface pressing rollers' to 'press' the water column at the inlet of the annular guide ring 4 into a strip of thin 'water belt', and the strip of thin 'water belt' is respectively overlapped into a whole at the same speed and then steadily flows forward, so that the idle work phenomenon generated by the undercurrent, water hammer and baffling in the existing centrifugal pump is thoroughly eliminated, the operation efficiency of the high-pressure pump or the medium-pressure pump is unprecedentedly improved, and the advantages are also shown even for the low-pressure pump.

In the present embodiment, as shown in FIG. 3, the overlap length between adjacent guide vanes 41 is a ₁ The length of the individual guide vane 41 is a ₂ ，a ₁ ＞(a ₂ /2). By reasonably setting the number of the guide vanes 41, the overlapping length between the adjacent guide vanes 41 reaches more than half of the length of a single guide vane 41, which is favorable for guiding fluid to be output along the guide flow channel 42, and is favorable for keeping the fluid output angle and the spiral angle inside the spiral case flow channel 8 in the same direction, namely, the outlet angle flow direction of each guide vane 41 is parallel to the main flow direction inside the spiral case flow channel 8, and the flow speed is similar, so that fluid synchronously flows forward in the guide flow channel 42, and phenomena such as undercurrent, water hammer, baffling and the like of the fluid in the spiral case flow channel 8 are avoided.

In the present embodiment, as shown in FIG. 3, the normal outlet width of the diversion flow passage 42 is c, and the throat width of the scroll flow passage 8 is d, d.apprxeq. (m-1). Times.c. The difference between the separating tongue and the throat is a distance of the width of the outlet of the diversion flow passage 42, so that the sum of the normal widths of the outlets of the diversion flow passages 42 minus the width of the outlet of the diversion flow passage 42 is close to the throat width of the volute flow passage 8, even if the outlet flow velocity of the annular diversion ring 4 has a small difference, automatic balance can be realized in the volute flow passage 8 instantaneously, and large disturbance can not be caused.

After the above structure is adopted, the guide vane 41 is unfolded and flattened to be a curved vane similar to a long trapezoid. Because the blades are longer, the angles of the two sides of the trapezoid are not large, and the water flow diffusion device is beneficial to the full space of water flow diffusion. As for the outer diameter of the guide wheel, the single side height is about one tenth of the diameter of the impeller in order to facilitate the processing technology. The high-speed water flow sprayed on the curved blade is naturally diffused into a thin fan-shaped water layer, and finally forms a water band, which is beneficial to reducing the flow speed and converting energy. The outlets of each fan-shaped water layer are formed into a continuous water band, and the water band is integrated and then pushes the water flow in the volute runner 8 to continuously flow forwards at a constant speed, so that almost most of kinetic energy of the fluid can be converted into static pressure, and the lost kinetic energy can be greatly reduced.

In this embodiment, as shown in fig. 5, the inner cavity of the cross section of the annular diversion ring 4 is flared from inside to outside. Further, the water inlet width b of the annular guide ring 4 ₁ Width b of water outlet of impeller 3 ₂ Slightly larger, e.g. b ₁ Can be compared with b ₂ 2mm to 4mm larger to prevent assembly deviation; the water outlet width of the annular guide ring 4 is equal to the axial width of the volute runner 8.

As shown in fig. 3 and 4, in this embodiment, the radial width of the spiral casing flow channel 8 is widened gradually from the front edge of the partition tongue to the throat according to the archimedes spiral rule, the axial width of the spiral casing flow channel 8 is as wide as the throat, and the spiral casing flow channel 8 is approximately square at the cross section of the throat. The average flow rate in the scroll flow path 8 is about 6m/s and the flow rate at the outlet is about 3m/s. Further, the cross section of the volute flow channel 8 gradually transits from square to round from the throat to the water outlet.

In this embodiment, the cross section of the spiral casing flow channel 8 is designed into a rectangular structure, the radial width of the spiral casing flow channel 8 is gradually increased from the partition tongue to the throat according to the archimedes spiral rule, the axial width of the spiral casing flow channel 8 is kept the same as the width of the throat, the spiral casing flow channel 8 is slightly square at the cross section of the throat, the spiral casing flow channel 8 is gradually transited into a circular structure from the throat to the water outlet, the transverse migration and mutual dislocation disturbance of fluid in the spiral casing flow channel 8 are effectively avoided, the spiral casing flow channel 8 is uniformly filled with the fluid, and the stability of fluid delivery and the water absorption lift of the centrifugal pump are improved.

In the present embodiment, as shown in FIG. 6, the water inlet angle of the guide vane 41 of the annular guide ring 4 and the absolute velocity C of the impeller 3 in the triangle ₂ Equidirectional and equiangular; the water outlet angle of the guide vane 41 of the annular guide ring 4 is equal to the spiral line angle of the wall of the pump shell 1; the fluid is kept in a better flowing state in the centrifugal pump, and the loss of kinetic energy caused by the impact of the fluid on the inner wall of the volute runner 8 is thoroughly eliminated.

As can be seen from the triangle of the flow path outlet in FIG. 6, the absolute velocity C thereof ₂ And alpha ₂ The angle is the linear velocity u of the driven impeller ₂ And outlet relative velocity W ₂ Is limited by the size of (b), u ₂ And beta ₂ After the angle is determined, there should be only one new W ₂ Exists and gives a new beta ₂ There will be an optimum W after the angle ₂ Presence, C ₂ And alpha ₂ Will also change together, where C ₂ And alpha ₂ Is not limited by the shape and flow state in the volute, but is limited by beta ₂ Angle sum u ₂ After determination W ₂ The size of (2) directly affects C ₂ And alpha ₂ Is a value of (a). This is only a momentary occurrence of fluid at the impeller flow passage outlet, irrespective of how the fluid flows in the volute flow passage. After the related calculation, for the pump with lower lift, alpha is known ₂ And beta ₂ The most efficient combination angle of (a) is alpha ₂ ＝11.53696°、β ₂ = 39.23152 °; for pumps with higher head, because of impeller diameterThe hydraulic friction loss of the enlarged rear end surface rises rapidly, so that a larger beta should be selected ₂ Angle to reduce impeller diameter to a point where the reduced friction torque may be more cost effective, beta ₂ The angle of (2) may be selected to be 40 to 50.

It will be appreciated that the inventive concept is also applicable to fans, as air and water are both collectively referred to as fluids, but are different in density, and are the subject of hydrodynamic studies. Many industrial sectors such as mining and metallurgy, industrial boilers and heating ventilation, dust removal, drying engineering of paper and food industry, etc. require centrifugal blowers above medium pressure, the power of these blowers is large and the efficiency is low, because these blowers are auxiliary equipment of the use units and are not easily perceived by users, the above technical scheme can be fully applied to improve the operation efficiency of these blowers, and numerous production units benefit. It is desirable that the operating efficiency of all single stage centrifugal pumps and centrifugal fans be increased to above 90%, including double suction high lift pumps.

While the invention has been described with reference to preferred embodiments, it is not intended to be limiting. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present invention or equivalent embodiments using the method and technical solution disclosed above without departing from the spirit and technical solution of the present invention. Therefore, any simple modification, equivalent substitution, equivalent variation and modification of the above embodiments according to the technical substance of the present invention, which do not depart from the technical solution of the present invention, still fall within the scope of the technical solution of the present invention.

Claims

1. A centrifugal pump, comprising: the impeller comprises a pump shell (1) and an impeller (3) arranged in the pump shell (1), wherein the impeller (3) comprises n blades (31), an impeller flow channel (32) is formed between every two adjacent blades (31), a volute flow channel (8) with a rectangular cross section is arranged on the inner periphery of the pump shell (1), a ring-shaped guide ring (4) is arranged between the inner ring of the volute flow channel (8) and the outer diameter of the impeller (3), the ring-shaped guide ring (4) comprises m guide blades (41), and a guide flow channel (42) is formed between every two adjacent guide blades (41); n and m are positive integers.

2. Centrifugal pump according to claim 1, wherein the overlap between adjacent guide vanes (41) has a length a ₁ The length of the single guide vane (41) is a ₂ ，a ₁ ＞(a ₂ /2)。

3. Centrifugal pump according to claim 1, wherein the outlet normal width of the flow guide channel (42) is c and the throat width of the scroll channel (8) is d, d≡ (m-1) ×c.

4. Centrifugal pump according to claim 1, wherein the cross-sectional cavity of the annular deflector ring (4) is flared from inside to outside.

5. Centrifugal pump according to claim 4, wherein the water inlet width b of the annular deflector ring (4) ₁ Is larger than the water outlet width b of the impeller (3) ₂ To compensate for installation deviations; the width of the water outlet of the annular guide ring (4) is equal to the axial width of the volute runner (8).

6. Centrifugal pump according to any one of claims 1-5, wherein the radial width of the scroll flow channel (8) is widened gradually from the front edge of the partition tongue to the throat according to the archimedes spiral rule, the axial width of the scroll flow channel (8) is as wide as the throat, and the cross section of the scroll flow channel (8) at the throat is approximately square.

7. Centrifugal pump according to claim 6, wherein the cross-section of the volute flow channel (8) gradually transitions from square to circular from throat to outlet.

8. Centrifugal pump according to claim 6, wherein the guide vane (41)The water inlet angle and the absolute speed C in the triangle of the water outlet of the blade (31) ₂ Equidirectional and equiangular; the water outlet angle of the guide vane (41) is equal to the spiral line angle of the outer edge wall of the pump shell (1).

9. Centrifugal pump according to any one of claims 1-5, wherein the guide vanes (41) are approximately trapezoidal blades after deployment.

10. Centrifugal pump according to any one of claims 1-5, wherein the impeller flow channel (32) has no diffusion angle, the outlet arc length of the impeller flow channel (32) is equal to the inlet arc length, and the redundant fan-shaped area is covered by the thickening of the outlet ends of the blades (31).