High-pressure and high-speed multi-stage centrifugal pump capable of replacing plunger pump

Abstract

The utility model discloses a high-pressure high-speed multistage centrifugal pump capable of replacing a plunger pump, which relates to the technical field of centrifugal pumps, and comprises a pump body, the pump body comprises a suction section, a discharge section, a middle section and a plurality of pull rods, the middle section is positioned between the suction section and the discharge section, and the suction section, the middle section and the discharge section are connected through the plurality of pull rods; the centrifugal pump further comprises guide vanes, a bearing seat, a pump shaft, a plurality of impeller assemblies, a balance assembly and a mechanical sealing assembly, the guide vanes are installed on the water inlet face of each middle section in the pump body, the balance assemblies are installed in the discharge section, and the bearing seat and the mechanical sealing assembly are both installed at one end of the discharge section. The mechanical sealing assembly is arranged between the discharge section and the bearing seat, a sliding bearing is installed in a cavity of the suction section, a double-row rolling bearing is installed in the bearing seat, and the pump shaft is installed in the sliding bearing and the double-row rolling bearing.

Description

Technical Field

[0001] The present invention relates to the technical field of centrifugal pumps, in particular to a high-pressure and high-speed multi-stage centrifugal pump which can replace a plunger pump. Background Art

[0002] Currently, plunger pumps are widely used as power delivery devices in fields such as zero-emission liquids, landfill leachate, RO water treatment, and seawater desalination. Plunger pumps are a type of positive displacement pump that rely on the reciprocating motion of a plunger within a cylinder, causing the volume of a sealed chamber to change to achieve liquid delivery. They are widely used in high-pressure applications.

[0003] Figure 1 It is a cross-sectional diagram of an existing plunger pump. Figure 1 It can be seen that the existing plunger pump has a large number of parts, including pump body, cylinder body, plunger and end cover. These parts have high processing precision requirements, complex manufacturing process, poor versatility and high price, which brings instability to subsequent maintenance and overhaul.

[0004] In addition, in actual use, the plunger pump has the following deficiencies:

[0005] First, the plunger pump is more sensitive to the medium it conveys. It is suitable for conveying oil or cleaning media, and its suction port must be equipped with a sophisticated filtering device. Secondly, the delivery pressure of the plunger pump is very high, which can reach more than 100MPA. As a result, the plunger pump is not suitable for applications with a delivery pressure between 4 and 16MPA. In addition, since the plunger pump is a volumetric pump, it operates intermittently, and its flow and pressure are discontinuous pulsations, resulting in high working noise. In situations where environmental requirements are high, a vibration reduction device must be configured. Moreover, when the medium is non-self-lubricating, it is extremely prone to wear, resulting in a reduced service life and high maintenance costs. Finally, the plunger pump cannot be directly connected to the motor, and relies on a pulley or gearbox for speed transmission, and cannot operate under high-speed conditions.

[0006] The existing market also uses typical stamping-type vertical multi-stage centrifugal pumps as an alternative to plunger pumps. These are made of 304 or 316 stainless steel, have simple structures, and low pressure tolerances, typically with output pressures below 2.5 MPa. For applications with flow rates of 5 to 500 m³ / h and output pressures of 2.5 to 16 MPa, there is a lack of suitable pump options, particularly impacting the development of zero-emission and reverse osmosis membrane technologies. Furthermore, the corrosion effects of chloride ions in wastewater projects and seawater desalination, the advancement and development of metal materials, and the exploration and development of non-metallic materials, are gradually driving the innovation and development of centrifugal pumps. Therefore, a new power pump is needed for applications in zero-emission, landfill leachate, RO water treatment, and seawater desalination, addressing the shortcomings of existing plunger pumps. Summary of the Invention

[0007] The object of the present invention is to provide a high-pressure, high-speed, multi-stage centrifugal pump that can replace the plunger pump, so as to solve the problems raised in the above background technology.

[0008] By adopting the above technical solution, the centrifugal pump can achieve the functions of continuous and stable operation, wide performance range, low noise and long service life.

[0009] In view of the above problems, the technical solution proposed by the present invention is:

[0010] A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump comprises a pump body, wherein the pump body comprises a suction section, a discharge section, a middle section, and a plurality of tie rods, wherein the middle section is located between the suction section and the discharge section, and the suction section, the middle section, and the discharge section are connected by the plurality of tie rods;

[0011] It also includes a guide vane, a bearing seat, a pump shaft, a plurality of impeller assemblies, a balancing assembly and a mechanical seal assembly. The pump body is provided with a guide vane on the water inlet surface of each middle section, the balancing assembly is installed in the discharge section, the bearing seat and the mechanical seal assembly are both installed at one end of the discharge section, the mechanical seal assembly is arranged between the discharge section and the bearing seat, a sliding bearing is installed in the cavity of the suction section, a double-row rolling bearing is installed in the bearing seat, the pump shaft is installed inside the sliding bearing and the double-row rolling bearing, and the pump shaft passes through the guide vane, the middle section, the balancing assembly and the mechanical seal assembly. Assembly and mechanical seal assembly, the outer wall of the pump shaft is provided with multiple impeller assemblies in sequence along the direction of water flow, the multiple impeller assemblies and the middle section are spaced apart from each other, multiple middle sections, guide vanes, closed impellers, primary wear rings, and secondary wear rings are connected in series between the suction section and the discharge section, one end of the discharge section is provided with a mechanical seal assembly and a bearing seat, the two ends of the pump shaft are respectively installed inside the suction section and the bearing seat, the outer wall of the bearing seat is installed with an oil seal, and the bearing seat component includes a sleeve, a double-row rolling bearing, a locking nut assembly, a labyrinth ring and an oil slinger.

[0012] As a further technical solution, the suction section, middle section, guide vanes, discharge section and other flow-passing components are all integrally cast parts, and the precision casting process is adopted to make the flow channel surface roughness Ra25 or less.

[0013] As a further technical solution, the impeller is a closed impeller, comprising a front shroud, a rear shroud, and intermediate blades. Considering low flow rates, high head, and low specific speed, the intermediate blade outlet width is narrow, only 5-8 mm. The front and rear shrouds are 3-5 mm thick. The blade inlet transitions tangentially to the extended line of the suction section flow path, while the outlet transitions obliquely to the outer diameter of the front and rear shrouds. The blades are twisted, with uniform thickness.

[0014] As a further technical solution, compared with the problem of low efficiency of ordinary centrifugal pumps under conditions of small flow and high head, modern computational fluid dynamics (CFD) is used to optimize the design of its hydraulic part, ensuring higher hydraulic efficiency.

[0015] As a further technical solution, compared with the problem of low efficiency of ordinary centrifugal pumps under conditions of small flow and high head, a high-speed motor is used and the pump adopts a rigid shaft design, so that the operating speed of this high-pressure and high-speed multi-stage centrifugal pump is 4000-5000RPM, and it runs smoothly, and the vibration and noise levels meet and exceed national standards.

[0016] As a further technical solution, the impeller hub passes through the guide vane, and a secondary wear ring is provided between the guide vane and the impeller hub. 4 to 6 twisted back blades are evenly arranged on the right side of the guide vane along the circumferential direction of the pump shaft, and the thickness varies evenly.

[0017] As a further technical solution, each rotating assembly mounted on the pump shaft, except for the one farthest from the suction section, is equipped with a primary wear ring between each intermediate section and the adjacent impeller front cover. These primary and secondary wear rings serve as consumable parts between the rotating and stator assemblies. For a long time, bronze has been the most commonly used metal material for wear rings, which is acid- and alkali-resistant, wear-resistant, and has good lubricity. The operating clearance between the wear ring and the rotating assembly directly affects the pump's operating efficiency. If the clearance is too large, the amount of liquid flowing back through the gap is excessive, reducing the volumetric efficiency of the centrifugal pump. If the clearance is too small, the wear ring may contact the rotating assembly, exacerbating wear or causing the centrifugal pump rotor and stator to seize.

[0018] The wear rings of this high-pressure, multistage centrifugal pump utilize a new, wear-resistant, and thermosensitive polymer, Vesconite. This non-metallic wear ring offers high load-bearing capacity, excellent wear resistance, a low coefficient of friction, a certain degree of self-lubrication, and ease of machining, allowing it to operate within tight tolerances. This enables the high-pressure, high-speed, multistage centrifugal pump to operate at high speeds. The operating clearance is extremely small, 0.05 to 0.15 mm, minimizing volumetric losses, improving pump efficiency, and reducing maintenance time and costs.

[0019] As a further technical solution, a balance drum is installed in the discharge section of the pump body, and the pump shaft passes through the balance drum. A submersible bearing is also provided between the balance drum and the suction section. Its material is also the aforementioned high-molecular wear-resistant and thermosensitive polymer Vesconite. The operating clearance between the inner ring of the submersible bearing and the outer ring of the balance drum is between 0.05 and 0.15 mm on one side. It has high efficiency and internal self-lubrication, can operate continuously well even under harsh operating conditions, and has a long service life.

[0020] In addition, a seal is installed between the discharge section and the bearing housing, through which the pump shaft passes. A cartridge-type high-pressure mechanical seal is installed between the pump shaft and the seal. A balancing chamber is located between the left side of the seal and the balance drum. After the medium is initially balanced by the balance drum, it remains under high pressure. This is then connected to the low-pressure area of the suction section via a balancing pipe for secondary balancing, protecting the mechanical seal and bearing components on the right side and extending their service life.

[0021] The assembled high-pressure mechanical seal components include high-pressure mechanical seal components, sleeves, sealing rings, balance rings, and mechanical seal glands. On the left side of the mechanical seal cavity is the medium pressure after dual balancing by the balance drum and balance pipe. On the right side is the mechanical seal gland, which is equipped with a metal flushing pipe that connects the cavity consisting of the first-stage impeller and the first-stage midsection, forming a reflux path to flush and dissipate heat from the components within the mechanical seal cavity, improving lubrication conditions, preventing dry running, and effectively extending the service life of the mechanical seal.

[0022] As a further technical solution, a high-molecular wear-resistant and heat-sensitive polymer Vesconite sliding bearing is installed in the inner cavity of the left suction section, and back-to-back angular contact ball bearings are arranged side by side in the right bearing seat. The left and right parts of the pump shaft are respectively installed in the sliding bearing and two angular contact ball bearings.

[0023] In actual use, water flows into the blade from the root of the blade and is then thrown out from the tail. In order to reduce the hydraulic loss and clearance loss of water at the root and tail of the blade, as a further technical solution, 4 to 6 blades are evenly distributed on the impeller along the circumferential direction of the pump shaft, and the thickness of the blade increases first and then decreases starting from the root.

[0024] Furthermore, the blade tail is beveled. The blade tail is set to be beveled in an arc shape through the tangent line of the outer circle of the cover plate, which reduces hydraulic loss and improves the working efficiency of the pump.

[0025] Furthermore, the present invention utilizes duplex steel for all flow-through components, including the suction section, midsection, guide vanes, impeller, and discharge section. This steel combines the superior properties of ferritic and austenitic two-phase stainless steels, offering excellent pitting corrosion resistance, high stress and strain resistance, and high pressure resistance. This makes it widely used in applications such as RO water treatment and seawater desalination.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. In actual use, by increasing or decreasing the number of middle sections and impeller assemblies, different power outputs can be provided, thereby better meeting the different levels of pressure output requirements for primary and secondary treatment in the field of reverse osmosis;

[0028] 2. The present invention has a simple structure, smaller size, and saves space. The pump body and impeller assembly are both cast parts, making maintenance convenient and flexible.

[0029] 3. The present invention has continuous and stable operation, a wide performance range, low noise, and long service life. Different flow rates and output pressures can be obtained through valve throttling or frequency conversion control. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural diagram of an existing plunger pump;

[0031] Figure 2 It is a structural schematic diagram of the present invention;

[0032] Figure 3 Schematic diagram of the structure of the impeller assembly in the embodiment;

[0033] Figure 4 A schematic diagram of the structure of the blade in the embodiment;

[0034] Figure 5 Schematic diagram of the structure of the water inlet surface of the guide vane in the embodiment;

[0035] Figure 6 It is a schematic diagram of the end structure of the present invention;

[0036] Figure 7 This is a top view of the present invention;

[0037] Figure 8 This is a flowchart of the control unit of the present invention.

[0038] In the figure: 100, suction section; 101, discharge section; 102, middle section; 103, pull rod; 2, guide vane; 3, bearing seat; 4, pump shaft; 5, impeller assembly; 50, impeller body; 51, front cover plate; 52, blade; 53, rear cover plate; 54, rear hub; 6, balance assembly; 60, balance drum; 61, balance disc; 7, mechanical seal assembly; 70, seal body; 71, mechanical seal component; 8, primary wear ring; 9, secondary wear ring; 10, balance chamber; 11, oil seal; 20, twisted back blade; 21, bushing; 22, double-row rolling shaft; 23, locking nut assembly; 24, labyrinth ring; 25, oil slinger ring; 200, balance pipe; 201, flushing pipe. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] See also Figure 2-Figure 7 The present invention provides a technical solution: a high-pressure, high-speed multi-stage centrifugal pump that can replace a plunger pump, including a pump body, the pump body including a suction section 100, a discharge section 101, a middle section 102 and a plurality of tie rods 103, the middle section 102 is located between the suction section 100 and the discharge section 101, and the suction section 100, the middle section 102 and the discharge section 101 are connected by a plurality of tie rods 103; the pump body also includes a guide vane 2, a bearing seat 3, a pump shaft 4, a plurality of impeller assemblies 5, a balancing assembly 6 and a mechanical seal assembly 7, a guide vane 2 is installed on the water inlet surface of each middle section 102 inside the pump body, the balancing assembly 6 is installed in the discharge section 101, the bearing seat 3 and the mechanical seal assembly 7 are both installed at one end of the discharge section 101, the mechanical seal assembly 7 is arranged between the discharge section 101 and the bearing seat 3, and a sliding bearing is installed in the cavity of the suction section 100. A double-row rolling bearing 22 is installed in the bearing seat 3, and the pump shaft 4 is installed inside the sliding bearing and the double-row rolling bearing 22, and the pump shaft 4 passes through the guide vane 2, the middle section 102, the balance assembly 6 and the mechanical seal assembly 7. The outer wall of the pump shaft 4 is provided with multiple impeller assemblies 5 in sequence along the direction of water flow. The multiple impeller assemblies 5 and the middle section 102 are spaced apart from each other. Multiple middle sections 102, guide vanes 2, closed impellers, primary wear rings 8, and secondary wear rings 9 are connected in series between the suction section 100 and the discharge section 101. One end of the discharge section 101 is set as a mechanical seal assembly 7 and a bearing seat 3. The two ends of the pump shaft 4 are respectively installed inside the suction section 100 and the bearing seat 3. The outer wall of the bearing seat 3 is installed with an oil seal 11. The components of the bearing seat 3 include a sleeve 21, a double-row rolling bearing 22, a locking nut assembly 23, a labyrinth ring 24 and an oil slinger 25.

[0041] like Figure 3 As shown, in this embodiment, the impeller assembly 5 includes an impeller body 50, a front cover plate 51, blades 52, a rear cover plate 53 and a rear hub 44. Six blades 52 are evenly distributed on the impeller body 50 along the circumferential direction of the pump shaft 4.

[0042] like Figure 4As shown, in this embodiment, the impeller assembly 5 has six blades 52 evenly distributed along the circumference of the pump shaft 4. The thickness of the blades 52 increases first and then decreases from the blade root, and the blade tails of the blades 52 are beveled. In actual use, since water flows into the blades 52 at the blade roots and is then ejected from the blade tails, by increasing the thickness of the blades 52 first and then decreasing from the blade roots, hydraulic losses and clearance losses at the blade roots and blade tails can be reduced. By beveling the blade tails of the blades 52, hydraulic losses can be reduced, thereby improving the operating efficiency of the present invention. Specifically, in this embodiment, the middle section 102 includes a first cavity and a second cavity, which are arranged sequentially along the water flow direction. The guide vanes 2 are located in the first cavity, and the front cover plate 51 of the impeller assembly 5 is located in the second cavity of the adjacent middle section 6. A primary wear ring 8 is provided between the front cover plate 50 of the impeller assembly 5 and the inner wall of the second cavity of the adjacent middle section 102. A secondary wear ring 9 is provided between the rear hub 44 of the impeller assembly 5 and the inner wall of the adjacent guide vane 2. Both primary and secondary wear rings 8 and 9 are made of a polymer composite material. The polymer composite material is Vesconite. The friction coefficient of the primary and secondary wear rings 8 and 9 is between 0.13 and 0.18, which is equivalent to half that of bronze or nylon. The impeller can operate at speeds of 4000 to 5000 RPM or higher, and has excellent wear resistance and a long service life. Moreover, the operating clearance between the primary wear ring 8 and the secondary wear ring 9 is small, ranging from 0.05 to 0.15 mm, which reduces volume loss, improves the operating efficiency of the pump, and reduces maintenance time and cost.

[0043] Existing primary and secondary wear rings 8 and 9 are made of metal materials, such as bronze. Although bronze is acid- and alkali-resistant, wear-resistant, and has a certain degree of lubricity, metal primary and secondary wear rings 8 and 9 are often used in practice. In contrast, the present invention utilizes non-metallic primary and secondary wear rings 8 and 9, which offer advantages such as high load-bearing capacity, good wear resistance, low friction coefficient, certain self-lubricating properties, ease of machining, and the ability to operate within a strict tolerance range. This allows the present invention to operate at high speeds with an operating clearance of 0.05 to 0.15 mm, reducing volume loss, maintenance time and costs, and improving pump efficiency.

[0044] like Figure 5 As shown, the left side of the guide vane 2 is provided with a flow channel, and the right side of the guide vane 2 is evenly distributed with six twisted back blades 20 along the circumferential direction of the pump shaft 4. In actual use, the six twisted back blades 20 can absorb the high-speed liquid flow at the outlet of the current stage impeller assembly 5 and gradually transfer the energy to the inlet of the next stage impeller assembly 5, thereby reducing the hydraulic loss caused by the fluid flow, avoiding cavitation in the present invention, and improving the efficiency of the present invention. Figure 2As shown, a balancing chamber 10 is provided between the mechanical seal assembly 7 and the balancing assembly 6. Figure 7 As shown, the balance chamber 10 is connected to the interior of the suction section 100 through the balance pipe 200. Figure 2 It can be seen that the balancing assembly 6 in this embodiment includes a balancing drum 60, a combined balancing sleeve and a balancing disc 61, the pump shaft 4 passes through the balancing drum 60, an intermediate bearing is provided between the balancing drum 60 and the discharge section 101, and the combined balancing sleeve and the balancing disc 61 are arranged on the periphery of the balancing drum 60; in a certain embodiment, the balancing assembly 6 only includes the balancing drum 60, the pump shaft 4 passes through the balancing drum 60, and an intermediate bearing is provided between the balancing drum 60 and the discharge section 101.

[0045] The process of balancing the axial force by the balancing assembly 6 in this embodiment is as follows:

[0046] The pressurized liquid exiting the rightmost impeller assembly 5 is decompressed through the irregular radial gap of the balance drum 60 and flows into the balance chamber 10, which is now at high pressure. After the balancing sleeve and balance disc 61 are combined, a balancing pipe is connected to the low-pressure area of the suction section 100, where its pressure is approximately equal to the inlet pressure. Due to the unequal pressure on both sides, a backward axial thrust is generated, which opposes the axial force and automatically balances the axial thrust of the rotor. When the axial thrust of the impeller assembly 5 exceeds the balancing force of the balance disc 61, the pump shaft 4, impeller assembly 5, and balance drum 61 will move toward the suction section 100. This movement causes the axial clearance of the balance disc 61 to decrease excessively, reducing leakage and increasing the pressure in the balance chamber 10. This increases the balancing force on the balance disc 61, ultimately reaching the axial thrust of the impeller assembly 5, moving the pump shaft 4, impeller assembly 5, and balance drum 60 toward the discharge section 101, achieving automatic balancing.

[0047] In addition, the material of the intermediate bearing in this embodiment is also Vesconite. The operating clearance between the inner ring of the intermediate bearing and the outer ring of the balance drum 60 is between 0.05 and 0.15 mm per side. It has high efficiency and internal self-lubrication. It can run continuously under harsh operating conditions and has a long service life. Figure 2 As shown, the mechanical seal assembly 7 in this embodiment includes a seal body 70 and a mechanical seal component 71. The seal body 70 is installed on the discharge section 101. A mechanical seal cavity is provided in the seal body 70. The mechanical seal component 71 is installed on the seal body 70 and is located in the mechanical seal cavity. The pump shaft 4 passes through the mechanical seal component 71. The mechanical seal component 71 is installed at the center of the seal body 70. Figure 8 As shown, the mechanical seal chamber is communicated with the first-stage flow channel cavity composed of the first-stage impeller and the first-stage middle section through a flushing pipe 201. In actual use, the mechanical seal component 71 can be flushed and heat-dissipated through the flushing pipe 201.

[0048] like Figure 7As shown, the pump shaft 4 of the present invention is provided with a first labyrinth ring, a sleeve 21, an oil slinger 25, a locking nut assembly 23 and a second labyrinth ring in sequence on the right side of the mechanical seal assembly 7. For ease of display, the first labyrinth ring and the second labyrinth ring are shown in FIG. Figure 7 The labyrinth rings 24 are both in the middle. The labyrinth ring 24 on the left is the first labyrinth ring, and the labyrinth ring 24 on the right is the second labyrinth ring. The pump shaft 4 passes through the first labyrinth ring, the sleeve 21, the oil-slinging ring 25, the locking nut assembly 23 and the second labyrinth ring. The double-row rolling bearing 22 is mounted on the outer wall of the sleeve 21. The first labyrinth ring and the second labyrinth ring are both connected to the bearing seat 3 through connecting parts, where the connecting parts can be screws.

[0049] In addition, in this embodiment, the materials of the suction section 100, the middle section 102, the discharge section 101, the guide vanes 2 and the impeller assembly 5 are all duplex steel. Duplex steel combines the excellent properties of ferritic steel and austenitic two-phase stainless steel, has good pitting corrosion resistance and high stress and strain resistance, and is widely used in RO water treatment, seawater desalination and other fields.

[0050] Secondly, in order to realize the constant flow control of the present invention, as Figure 8 As shown, the present invention also includes a flow meter, a frequency converter, a motor and a drive circuit board. The rotating end of the motor is connected to the pump shaft, the power output end of the frequency converter is electrically connected to the power input end of the motor, the flow meter is installed on the discharge section, and the drive circuit board is provided with an analog-to-digital conversion unit, a main control unit, a digital-to-analog conversion unit, a buffer and a reference voltage setting unit. The signal output end of the flow meter and the voltage output end of the reference voltage setting unit are respectively electrically connected to the input end of the analog-to-digital conversion unit, the output end of the analog-to-digital conversion unit is electrically connected to the main control unit, the main control unit is electrically connected to the input end of the digital-to-analog conversion unit, the output end of the digital-to-analog conversion unit is electrically connected to the input end of the buffer, and the output end of the buffer is electrically connected to the voltage control signal input end of the frequency converter.

[0051] Since the water output flow rate of the pump is related to the rotational speed of the pump shaft 4, the rotational speed of the pump shaft 4 is related to the motor rotational speed, and the motor rotational speed is related to the power frequency output by the inverter, the output power frequency of the inverter can be controlled by buttons on the inverter, by a peripheral controller sending a control command to the inverter, and by inputting voltage signals of different amplitudes to the voltage control signal input terminal of the inverter. When voltage signals of different amplitudes are input to the voltage control signal input terminal of the inverter, the power frequency output by the inverter can be adjusted.

[0052] Since the flow meter outputs an analog signal, the voltage amplitude of the analog signal is positively correlated with the water outlet flow rate; therefore, by comparing the amplitude of the analog signal output by the flow meter with the set value, which represents the set water outlet flow rate, it is possible to detect whether the water outlet flow rate has reached the set value.

[0053] In this embodiment, a reference voltage setting unit is used to set the set voltage representing the set water flow rate. The analog-to-digital conversion unit performs analog-to-digital conversion on the set voltage and the analog signal output by the flow meter. The main control unit obtains the conversion result from the analog-to-digital conversion unit and compares the set voltage with the conversion result of the analog signal. When the set voltage is greater than the analog signal, the main control unit increases the output value of the digital-to-analog conversion unit, thereby increasing the voltage input to the voltage control signal input terminal of the frequency converter, increasing the pump shaft speed and the water flow rate. When the set voltage is less than the analog signal, the main control unit decreases the output value of the digital-to-analog conversion unit, thereby decreasing the voltage input to the voltage control signal input terminal of the frequency converter, reducing the pump shaft speed and the water flow rate. When the set voltage is equal to the analog signal, the main control unit maintains the output value of the analog-to-digital conversion unit unchanged, thereby ensuring stable pump shaft speed and water flow rate. In addition, a buffer can ensure the stability of the voltage input to the voltage control signal input terminal of the frequency converter. The above is based on the present invention as a guide. Based on the above description, relevant personnel can make various changes and modifications without departing from the scope of the technical spirit of this invention. The technical scope of this invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump, comprising a pump body, characterized in that: The pump body comprises a suction section (100), a discharge section (101), a middle section (102) and a plurality of tie rods (103); the middle section (102) is located between the suction section (100) and the discharge section (101); the suction section (100), the middle section (102) and the discharge section (101) are connected via the plurality of tie rods (103); The pump body further comprises a guide vane (2), a bearing seat (3), a pump shaft (4), a plurality of impeller assemblies (5), a balancing assembly (6) and a mechanical seal assembly (7), wherein the guide vane (2) is installed on the water inlet surface of each middle section (102) inside the pump body, the balancing assembly (6) is installed in the discharge section (101), the bearing seat (3) and the mechanical seal assembly (7) are both installed at one end of the discharge section (101), the mechanical seal assembly (7) is arranged between the discharge section (101) and the bearing seat (3), a sliding bearing is installed in the cavity of the suction section (100), a double-row rolling bearing (22) is installed in the bearing seat (3), the pump shaft (4) is installed inside the sliding bearing and the double-row rolling bearing (22), and the pump shaft (4) passes through the guide vane (2), the middle section (102) and the balancing assembly (6). and a mechanical seal assembly (7), the outer wall of the pump shaft (4) is provided with a plurality of the impeller assemblies (5) in sequence along the water flow direction, the plurality of impeller assemblies (5) and the middle section (102) are spaced apart from each other, the plurality of middle sections (102), guide vanes (2), closed impellers, a primary wear ring (8), and a secondary wear ring (9) are connected in series between the suction section (100) and the discharge section (101), one end of the discharge section (101) is provided with a mechanical seal assembly (7) and a bearing seat (3), the two ends of the pump shaft (4) are respectively installed inside the suction section (100) and the bearing seat (3), the outer wall of the bearing seat (3) is provided with an oil seal (11), and the bearing seat (3) components include a shaft sleeve (21), a double-row rolling bearing (22), a locking nut assembly (23), a labyrinth ring (24), and an oil slinger (25).

2. A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 1, characterized in that: The impeller assembly (5) comprises an impeller body (50), a front cover plate (51), blades (52), a rear cover plate (53) and a rear hub (54), and six blades (52) are evenly distributed on the impeller body (50) along the circumferential direction of the pump shaft (4).

3. A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 2, characterized in that: The thickness of the six blades (52) first increases and then decreases from the blade root, and the blade tails (52) are beveled.

4. A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 3, characterized in that: The middle section (102) comprises a first cavity and a second cavity, wherein the first cavity and the second cavity are arranged in sequence along the water flow direction, the guide vane (2) is located in the first cavity, the front cover plate (51) of the impeller assembly (5) is located in the second cavity of the adjacent middle section (102), a primary wear ring (8) is provided between the front cover plate (51) of the impeller assembly (5) and the inner wall of the second cavity of the adjacent middle section (102), and a secondary wear ring (9) is provided between the rear hub (54) of the impeller assembly (5) and the inner wall of the adjacent guide vane (2).

5. A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 1, characterized in that: The pump shaft (4) is provided with a pair of labyrinth rings (24), a shaft sleeve (21), an oil-slinging ring (25), and a locking nut assembly (23) in sequence on one side of the mechanical seal assembly (7); the pump shaft (4) passes through one of the labyrinth rings (24), the shaft sleeve (21), the oil-slinging ring (25), the locking nut assembly (23), and the other labyrinth ring (24); the double-row rolling bearing (22) is sleeved on the outer wall of the shaft sleeve (21); and the pair of labyrinth rings (24) are connected to the bearing seat (3) by screws.

6. A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 1, characterized in that: A flow channel is provided on one side of the guide vane (2), and six twisted back blades (20) are evenly distributed along the circumferential direction of the pump shaft (4) on the other side.

7. A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 1, characterized in that: A balancing chamber (10) is provided between the mechanical seal assembly (7) and the balancing assembly (6), and a balancing pipe (200) is connected between the balancing chamber (10) and the suction section (100).

8. The high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 1, characterized in that: The balancing assembly (6) includes a balancing drum (60), a combined balancing sleeve and a balancing disc (61); the pump shaft (4) passes through the balancing drum (60); an intermediate bearing is provided between the balancing drum (60) and the discharge section (101); the combined balancing sleeve and the balancing disc (61) are arranged on the periphery of the balancing drum (60); and the operating clearance between the inner ring of the intermediate bearing and the outer ring of the balancing drum (60) is set to 0.05 to 0.15 mm on one side.

9. The high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 1, characterized in that: The mechanical seal assembly (7) comprises a seal body (70) and a mechanical seal component (71), the seal body (70) being mounted inside the discharge section (101), a mechanical seal cavity being provided inside the seal body (70), the mechanical seal component (71) being mounted at the center of the seal body (70) and being located in the mechanical seal cavity, the pump shaft (4) passing through the mechanical seal component (71), the mechanical seal component (71) being between the pump shaft (4) and the seal body (70), the impeller assembly (5) and the middle section (102) constituting a first-stage flow channel cavity, and a flushing pipe (201) being connected between the mechanical seal cavity and the first-stage flow channel cavity.

10. The high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 1, characterized in that: The invention also includes a flow meter, a frequency converter, a motor and a drive circuit board, wherein the rotating end of the motor is connected to the pump shaft (4), the power output end of the frequency converter is electrically connected to the power input end of the motor, the flow meter is installed on one side of the discharge section (101), and an analog-to-digital conversion unit, a main control unit, a digital-to-analog conversion unit, a buffer and a reference voltage setting unit are provided inside the drive circuit board, the signal output end of the flow meter and the voltage output end of the reference voltage setting unit are electrically connected to the input end of the analog-to-digital conversion unit respectively, the output end of the analog-to-digital conversion unit is electrically connected to the main control unit, the main control unit is electrically connected to the input end of the digital-to-analog conversion unit, the output end of the digital-to-analog conversion unit is electrically connected to the input end of the buffer, and the output end of the buffer is electrically connected to the voltage control signal input end of the frequency converter.

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