A centrifugal pump

Abstract

This invention discloses a centrifugal pump, comprising: a pump casing and an impeller installed within the pump casing. The impeller includes n blades, with adjacent blades forming an impeller flow channel. The inner circumference of the pump casing is provided with a volute flow channel with a rectangular cross-section. An annular guide ring is provided between the inner ring of the volute flow channel and the outer diameter of the impeller. The annular guide ring includes m guide vanes, with adjacent guide vanes forming a guide flow channel; n and m are both positive integers. The centrifugal pump of this invention has advantages such as compact structure, easy installation, high reliability, and low kinetic energy loss. It can greatly reduce the eddies formed within the pump flow channel, thereby significantly improving the overall efficiency of the pump.

Description

Technical Field

[0001] This invention belongs to the technical field of centrifugal pump equipment for conveying liquids, and specifically relates to a centrifugal pump. Background Technology

[0002] Centrifugal pumps play a vital role in national economic development, indispensable in both industrial and agricultural production and daily life. Due to their diverse applications, they come in a wide variety of types and specifications. However, few people realize that this historically significant equipment contains numerous high-energy-consuming products. Some low-specific-speed centrifugal pumps have operating efficiencies of less than 75%, and even the most widely used single-stage, single-suction centrifugal pumps only achieve efficiencies of (60-80)%, with some even below 60% produced by various pump manufacturers. This undoubtedly results in significant resource waste in energy-scarce my country and causes unnecessary economic losses for users.

[0003] Figure 1 and Figure 2 The diagram illustrates the structure and discharge principle of an existing centrifugal pump. Let u2 be the tangent at point A, u2 be the circumferential velocity, and W2 be the relative velocity of the water flow at the blade exit, with an angle β2 between it and the blade tangent. The combination of these two velocities results in the absolute velocity C2, which has an angle α2 with the tangent. Figure 1 As can be seen, when a point mass A is ejected from the impeller outlet at an absolute velocity C2, because there is already low-speed water flowing forward in the annular channel, the water ejected from the blades will also move forward within this short period of time. When the fluid collides with the volute after passing through the impeller, it generates water hammer, deflection, and reflection. According to fluid dynamics, the process of a high-speed fluid moving from point A to the point of intersection with the volute is called undercurrent. Because the water ejected from the impeller's circumference resembles a "disc," and its radius continuously increases during the ejection process, the "disc" forms a dense "brushing" effect. After the full-circumference water flow reaches the volute wall, it generates strong water hammer, deflection, and reflection before merging into the lower-speed fluid on both sides of the annular flow channel. Furthermore, because the impellers of high-pressure pumps rotate at high speeds, the velocity ejected by the impeller is five times or more than the velocity of the flow in the annular flow channel. Also, because the "disc" in a high-pressure pump is thin and the velocity is high, it generates strong vortices. The most significant effects are water hammer and deflection. Before the fluid hits the volute wall, there is first undercurrent, followed by severe water hammer, deflection, and reflection; these processes consume a large amount of the fluid's kinetic energy. When the fluid impacts the wall at a deflection angle, the angle θ is approximately 42°. According to the Wiesbach equation in fluid mechanics, the drag coefficient is 0.0726 when the angle θ is 30°, and 0.1553 when θ is 42°. This means that approximately 15.5% of the pump's total head is lost. Therefore, the main reason for the low efficiency of high-pressure pumps is this wasted energy. Of course, there is also energy loss due to reflection after the deflection. As for the water hammer that occurs when the water ejected from the impeller hits the volute wall, the Wiesbach equation shows that when the angle θ is 90° (right-angle injection), the drag coefficient is 0.9855, meaning almost 100% of the fluid's kinetic energy is consumed. This is similar to the energy loss observed when water flows perpendicularly towards a plate. This is not energy conversion; it is all energy loss. Because once the fluid hits the perpendicular plate, it can no longer do work; all its kinetic energy is consumed. Of course, the water hammer caused by inclined jets depends on the angle and velocity of the water flow. The higher the pump head, the higher the flow velocity, and the greater the losses mentioned above. This is the biggest drawback of modern centrifugal pumps.

[0004] A drawback of traditional centrifugal pump impeller structures is the excessively large diffusion angle between the blades. This is because the fluid in the impeller channel is subjected to both centrifugal force and a Coriolis force (tangential to the direction of rotation) within the impeller flow channel. The Coriolis force causes the fluid to flow close to the working surface of the blades, creating a negative pressure cavitation region near the non-working surface. Due to this negative pressure cavitation region, the fluid at the larger radius between the blades experiences only centrifugal force and no suction force on the inlet fluid, as this negative pressure cavitation region easily draws in high-pressure fluid from outside the impeller, generating eddies. The diffusion angle area between the flow channels is not filled with fluid, thus failing to provide suction at the impeller inlet. Fluid entry into the flow channel relies solely on the centrifugal force generated by the fluid at the smaller radius of the impeller flow channel for suction at the impeller inlet, while the fluid at the larger radius only experiences centrifugal force without suction. This results in a low suction head for the centrifugal pump. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a centrifugal pump that is compact, easy to install, highly reliable and has low energy loss.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A centrifugal pump includes: a pump casing and an impeller installed inside the pump casing. The impeller includes n blades, and an impeller flow channel is formed between adjacent blades. A volute flow channel with a rectangular cross-section is provided on the inner circumference of the pump casing. An annular guide ring is provided between the inner ring of the volute flow channel and the outer diameter of the impeller. The annular guide ring includes m guide blades, and a guide flow channel is formed between adjacent guide blades. n and m are both positive integers.

[0008] As a further improvement of the present invention, the overlap length between adjacent guide vanes is a1, the length of a single guide vane is a2, and a1 > (a2 / 2).

[0009] As a further improvement of the present invention, the outlet normal width of the guide channel is c, and the throat width of the volute channel is d, where d≈(m-1)×c.

[0010] As a further improvement of the present invention, the cross-sectional cavity of the annular guide ring is funnel-shaped from the inside to the outside.

[0011] As a further improvement of the present invention, the inlet width b1 of the annular guide ring is greater than the outlet width b2 of the impeller to compensate for installation deviation; the outlet width of the annular guide ring is equal to the axial width of the volute flow channel.

[0012] As a further improvement of the present invention, the radial width of the volute flow channel gradually increases from the front edge of the tongue to the throat according to the Archimedean spiral law, the axial width of the volute flow channel is the same as that of the throat, and the cross-section of the volute flow channel at the throat is approximately square.

[0013] As a further improvement of the present invention, the cross-section of the volute flow channel gradually transitions from square to circular from the throat to the outlet.

[0014] As a further improvement of the present invention, the water entry angle of the guide vane is in the same direction and angle as the absolute velocity C2 in the water exit triangle of the vane; the water exit angle of the guide vane is equal to the helical angle of the outer wall of the pump casing.

[0015] As a further improvement of the present invention, the guide vane unfolds into an approximately long trapezoidal vane.

[0016] As a further improvement of the present invention, the impeller channel has almost no diffusion angle, the outlet arc length of the impeller channel is equal to or slightly wider than the inlet arc length, and the excess fan-shaped area is covered by thickening at the outlet end of the blade.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] 1. The centrifugal pump of this invention, by installing an impeller inside the pump casing and setting a rectangular cross-section volute annular flow channel on the inner circumference of the pump casing, and setting an annular guide ring near the inlet position in the volute flow channel, that is, setting an annular guide ring on the outer circumference of the impeller outlet, results in a centrifugal pump with a compact structure, easy installation, high reliability and low kinetic energy loss. The fluid to be transported is drawn into the impeller through the inlet, then output by the impeller to the annular guide ring, and finally output through the guide ring flow channel to the volute flow channel. The function of the annular guide ring is equivalent to several pairs of "pressing rollers" "pressing" the water column at the inlet of the annular guide ring into thin "water strips", which are stacked together at the same speed and flow smoothly forward. This completely eliminates the useless work phenomenon caused by undercurrent, water hammer and flow deflection in existing centrifugal pumps, and the operating efficiency of both high-pressure pumps and medium-pressure pumps is unprecedentedly improved.

[0019] 2. The centrifugal pump of the present invention designs the cross-section of the volute flow channel as a rectangular structure, and gradually increases the radial width of the volute flow channel from the tongue to the throat according to the Archimedean spiral law. The axial width of the volute flow channel is the same as that of the throat. The cross-section of the volute flow channel at the throat is slightly square. The volute flow channel gradually transitions to a circular structure from the throat to the outlet. This effectively avoids the lateral migration and mutual displacement disturbance of the fluid in the volute flow channel, and makes the fluid uniformly fill the volute flow channel, thereby improving the stability of fluid transportation and the suction head of the centrifugal pump. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structural principle of an existing centrifugal pump.

[0021] Figure 2 This is a schematic diagram of the water discharge principle of an existing centrifugal pump.

[0022] Figure 3 This is a schematic diagram illustrating the structural principle of the centrifugal pump of the present invention.

[0023] Figure 4 This is a partial cross-sectional view of the centrifugal pump of the present invention from another perspective, illustrating its structural principle.

[0024] Figure 5 for Figure 4 A schematic diagram of the structural principle at point D.

[0025] Figure 6This is a schematic diagram illustrating the principle of water output in a specific application example of the present invention.

[0026] Legend: 1. Pump casing; 2. Main shaft; 3. Impeller; 31. Blade; 32. Impeller flow channel; 4. Annular guide ring; 41. Guide blade; 42. Guide flow channel; 5. Base; 6. Outlet; 7. Inlet; 8. Volute flow channel. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0028] Example

[0029] like Figures 3 to 6 As shown, the centrifugal pump of the present invention includes: a pump casing 1 and an impeller 3 installed inside the pump casing 1. A base 5 is provided at the bottom of the pump casing 1. The impeller 3 is connected to the main shaft 2 and rotates under the drive of the main shaft 2 and the drive component. The working surface of the impeller 3 faces the inlet 7. The impeller 3 includes n blades 31, and an impeller flow channel 32 is 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 slightly larger than the inlet arc length. The excess fan-shaped area is covered by thickening at the outlet end of the blades 31, making the impeller flow channel 32 so that the outlet and inlet are almost the same width. A volute flow channel 8 with a rectangular cross-section is provided on the inner circumference of the pump casing 1. An annular guide ring 4 is provided between the inner ring of the volute flow channel 8 and the outer diameter of the impeller 3. The annular guide ring 4 includes m guide blades 41, and a guide flow channel 42 is formed between adjacent guide blades 41; n and m are both positive integers. It is understandable that, in order to improve the stiffness of the annular guide ring 4, ductile iron or similar metallic materials can be used to fabricate the annular guide ring 4.

[0030] It is understandable that the impeller flow channel 32 should not be set with an excessively large diffusion angle. Strictly speaking, several undesirable conditions in the operation of a centrifugal pump (such as overload, hump, and cavitation) are closely related to the diffusion angle of the impeller flow channel 32. Therefore, making the inlet and outlet widths of the impeller flow channel 32 almost equal or with a slight diffusion angle can eliminate or greatly reduce the aforementioned undesirable conditions.

[0031] In this embodiment, by installing an impeller 3 inside the pump casing 1, and providing a volute flow channel 8 with a rectangular cross-section on the inner circumference of the pump casing 1, and setting an annular guide ring 4 between the inner ring of the volute flow channel 8 and the outer diameter of the impeller 3 near the inlet 7, that is, setting an annular guide ring 4 on the outer circumference of the outlet of the impeller 3, the phenomena of undercurrent, water hammer and flow obstruction of fluid in the pump casing are completely eliminated, resulting in a centrifugal pump with a compact structure, easy installation, high reliability and low kinetic energy loss. The fluid to be transported is drawn into the impeller 3 through the inlet 7, then output from the impeller 3 to the annular guide ring 4, and then from the guide channel 42 of the annular guide ring to the volute channel 8, and finally output from the outlet 6. The entire process is independent and flows smoothly forward. The function of the annular guide ring 4 is equivalent to several pairs of "pressing rollers" that "press" the water column at the inlet of the annular guide ring 4 into thin "water strips", which are stacked together at the same speed and flow smoothly forward. This completely eliminates the useless work caused by undercurrent, water hammer and deflection in existing centrifugal pumps. The operating efficiency of both high-pressure and medium-pressure pumps is unprecedentedly improved, and even low-pressure pumps can show advantages.

[0032] like Figure 3 As shown, in this embodiment, the overlap length between adjacent guide vanes 41 is a1, and the length of a single guide vane 41 is a2, where a1 > (a2 / 2). By reasonably setting the number of guide vanes 41, the overlap length between adjacent guide vanes 41 reaches more than half the length of a single guide vane 41. This is beneficial for guiding the fluid out along the guide channel 42 and for maintaining the fluid output angle in the same direction as the spiral angle inside the volute channel 8. That is, the outlet angle of each guide vane 41 is parallel to the mainstream direction inside the volute channel 8, and the flow velocity is also similar. This allows the fluid to flow forward synchronously in the guide channel 42, avoiding phenomena such as undercurrent, water hammer, and deflection in the fluid inside the volute channel 8.

[0033] like Figure 3 As shown, in this embodiment, the normal outlet width of the guide channel 42 is c, and the throat width of the volute channel 8 is d, where d ≈ (m-1) × c. Since the distance between the tongue and the throat is equal to the outlet width of the guide channel 42, the sum of the normal widths of the guide channel 42 outlets minus this distance is close to the throat width of the volute channel 8. Even if there is a slight difference in the outlet velocity of the annular guide ring 4, it will instantly achieve automatic balance within the volute channel 8, without causing significant disturbance.

[0034] With the above structure, the guide vane 41 unfolds and flattens into a curved blade that is approximately a long trapezoid. Because the blade is relatively long, the angles on both sides of its trapezoid are not large, which is beneficial for the diffusion of water throughout the entire space. As for the appropriate outer diameter of the guide wheel, it is generally advisable to take the height of one side as about one-tenth of the impeller diameter for ease of manufacturing. When high-speed water is sprayed onto the curved blade, it will naturally diffuse into a thin fan-shaped water layer, eventually forming a water band, which helps to reduce the flow velocity and convert energy. Each fan-shaped water layer outlet becomes a continuous "water band" that merges into a whole and pushes the water in the volute flow channel 8 forward continuously at a constant speed. In this way, almost all of the fluid's kinetic energy can be converted into static pressure, while the loss of kinetic energy will be greatly reduced.

[0035] like Figure 5 As shown, in this embodiment, the cross-sectional cavity of the annular guide ring 4 is funnel-shaped from the inside out. Furthermore, the inlet width b1 of the annular guide ring 4 is slightly larger than the outlet width b2 of the impeller 3, for example, b1 can be 2mm to 4mm larger than b2 to prevent assembly deviation; the outlet width of the annular guide ring 4 is equal to the axial width of the volute flow channel 8.

[0036] like Figure 3 and Figure 4 As shown, in this embodiment, the radial width of the volute channel 8 gradually increases from the leading edge of the tongue to the throat according to the Archimedean spiral pattern. The axial width of the volute channel 8 is the same as that of the throat, and the cross-section of the volute channel 8 at the throat is approximately square. The average flow velocity in the volute channel 8 is approximately 6 m / s, and the flow velocity at the outlet is approximately 3 m / s. Furthermore, the cross-section of the volute channel 8 gradually transitions from square to circular from the throat to the outlet.

[0037] In this embodiment, the cross-section of the volute flow channel 8 is designed as a rectangular structure. The radial width of the volute flow channel 8 gradually increases from the tongue to the throat according to the Archimedean spiral law. The axial width of the volute flow channel 8 is the same as that of the throat. The cross-section of the volute flow channel 8 at the throat is slightly square. The volute flow channel 8 gradually transitions to a circular structure from the throat to the outlet. This effectively avoids the lateral migration and mutual displacement disturbance of the fluid in the volute flow channel 8, and makes the fluid uniformly fill the volute flow channel 8, thereby improving the stability of fluid transportation and the suction head of the centrifugal pump.

[0038] like Figure 6 As shown, in this embodiment, the water entry angle of the guide vane 41 of the annular guide ring 4 is the same as the absolute velocity C2 in the water outlet triangle of the impeller 3; the water outlet angle of the guide vane 41 of the annular guide ring 4 is equal to the spiral angle of the pump casing 1 wall; so that the fluid maintains a better flow state in the centrifugal pump and completely eliminates the loss of kinetic energy due to the fluid hitting the inner wall of the volute flow channel 8.

[0039] Depend on Figure 6 From the outlet triangle of the impeller channel, it can be seen that the absolute velocities C2 and α2 are constrained by the impeller linear velocity u2 and the relative outlet velocity W2. Once u2 and β2 are determined, only one optimal new W2 should exist, and given a new β2 angle, another optimal W2 will exist. C2 and α2 will also change accordingly. Here, C2 and α2 are not constrained by the shape and flow regime inside the volute; rather, once β2 and u2 are determined, the magnitude of W2 directly affects the values ​​of C2 and α2. This is only generated instantaneously at the impeller channel outlet; how the fluid flows within the volute channel is irrelevant. After relevant calculations, it can be seen that for pumps with low head, the optimal combination angle for α2 and β2 is α2 = 11.53696° and β2 = 39.23152°. For pumps with high head, the hydraulic friction loss at the rear end increases rapidly due to the increased impeller diameter. Therefore, a larger β2 angle should be selected to reduce the impeller diameter. This reduction in friction torque may be more cost-effective. In this case, the β2 angle can be selected to be between 40° and 50°.

[0040] It is understandable that the technical concept of this invention is also suitable for use with fans, since air and water are both collectively referred to as fluids, differing only in density, and are both subjects of fluid mechanics research. Many industrial sectors, such as mining and metallurgy, industrial boilers and heating, ventilation, dust removal, and drying processes in the paper and food industries, require centrifugal blowers with medium to high pressure. These blowers have relatively high power and low efficiency. Because these blowers are auxiliary equipment used by the users, they are not easily noticed by the users, making this a significant problem that needs to be solved. The above technical solution can be applied to improve the operating efficiency of these blowers, benefiting numerous production units. It is hoped that the operating efficiency of all single-stage centrifugal pumps and centrifugal fans can be increased to over 90%, including double-suction high-lift pumps.

[0041] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A centrifugal pump, characterized by include: The pump casing (1) and the impeller (3) installed in the pump casing (1) are provided. The impeller (3) includes n blades (31). An impeller flow channel (32) is formed between adjacent blades (31). 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. The excess fan-shaped area is covered by thickening at the outlet end of the blades (31). The inner circumference of the pump casing (1) is provided with a volute flow channel (8) with a rectangular cross-section. An annular guide ring (4) is provided between the inner ring of the volute flow channel (8) and the outer diameter of the impeller (3). The annular guide ring (4) includes m guide blades (41). A guide flow channel (42) is formed between adjacent guide blades (41). n and m are both positive integers. The overlap length between adjacent guide vanes (41) is a1, and the length of a single guide vane (41) is a2, where a1 > (a2 / 2). The outlet normal width of the guide channel (42) is c, and the throat width of the volute channel (8) is d, where d≈(m-1)×c; The cross-sectional cavity of the annular guide ring (4) is funnel-shaped from the inside to the outside; The inlet width b1 of the annular guide ring (4) is greater than the outlet width b2 of the impeller (3) to compensate for the installation deviation; the outlet width of the annular guide ring (4) is equal to the axial width of the volute flow channel (8).

2. The centrifugal pump of claim 1, wherein The radial width of the volute flow channel (8) gradually increases from the front edge of the tongue to the throat according to the Archimedes spiral law. The axial width of the volute flow channel (8) is the same as that of the throat. The cross-section of the volute flow channel (8) at the throat is square.

3. The centrifugal pump of claim 2, wherein, The cross-section of the volute flow channel (8) gradually transitions from square to circular from the throat to the outlet.

4. The centrifugal pump of claim 2, wherein, The water inlet angle of the guide vane (41) is in the same direction and angle as the absolute velocity C2 in the water outlet triangle of the vane (31); the water outlet angle of the guide vane (41) is equal to the spiral angle of the outer wall of the pump casing (1).

5. The centrifugal pump of claim 1, wherein, The guide vane (41) unfolds into a trapezoidal vane.

Images