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

Abstract

The invention discloses a high-pressure and high-speed multi-stage centrifugal pump capable of replacing a plunger pump, and relates to the technical field of centrifugal pumps, the high-pressure and high-speed multi-stage centrifugal pump 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 located between the suction section and the discharge section, and the suction section, the middle section and the discharge section are connected through the 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 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] At present, plunger pumps are mostly used as power delivery devices in the fields of zero emission, landfill leachate, RO water treatment and seawater desalination. Plunger pumps are a type of positive displacement pump. They rely on the reciprocating motion of the plunger in the cylinder to change the volume of the sealed chamber to achieve liquid delivery. They are widely used in high-pressure occasions.

[0003] Figure 1 It is a cross-sectional schematic diagram of an existing plunger pump. Figure 1 It can be seen that the existing plunger pump has a large number of components, including pump body, cylinder body, plunger and end cover. These components 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 shortcomings: First of all, 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 precise 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 where the delivery pressure is 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 very easy 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 at high speeds.

[0005] There are also typical stamping vertical multi-stage centrifugal pumps on the market that replace plunger pumps. They are made of stainless steel 304 and 316, have simple structures, and are not high-pressure-bearing. The general output pressure is within 2.5MPA. There is no suitable pump type to choose from in the application field of flow rate 5-500m3 / h and output pressure 2.5-16MPA, which especially affects the development of zero emission and reverse osmosis membrane technology. In addition, considering the corrosion of chloride ions in wastewater projects and seawater desalination, the advancement and development of metal materials, and the exploration and trend of non-metallic materials, the process of innovation and development of centrifugal pumps is gradually promoted.

[0006] Therefore, a new power pump is needed for applications in the fields of zero discharge, landfill leachate, RO water treatment and seawater desalination to solve the shortcomings of existing plunger pumps. Summary of the invention

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

[0008] By adopting the above technical solution, the centrifugal pump achieves the functions of continuous stability, 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: 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; 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. 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 a plurality of impeller assemblies in sequence along the water flow direction, the plurality of impeller assemblies and the middle section are spaced apart from each other, a plurality of 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, an oil seal is installed on the outer wall of the bearing seat, and the bearing seat component comprises a sleeve, a double-row rolling bearing, a locking nut assembly, a labyrinth ring, and an oil slinger.

[0010] 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 a precision casting process is adopted to make the flow channel surface roughness Ra25 or less.

[0011] As a further technical solution, the impeller is a closed impeller, including a front cover plate, a rear cover plate and an intermediate blade. Considering the small flow, high head and low specific speed, the intermediate blade outlet width is narrow, only 5-8mm, the front and rear cover plates are 3-5mm thick, the blade inlet is tangent to the extended line of the suction section flow channel, and the outlet is beveled to the outer diameter of the front and rear cover plates. The blade type is a twisted blade with uniform thickness.

[0012] 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.

[0013] 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 meet and exceed the national standard requirements.

[0014] 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.

[0015] As a further technical solution, except for the rotating assembly farthest from the suction section, a primary wear ring is provided between each middle section of the rotating assembly installed on the pump shaft and the adjacent impeller front cover plate.

[0016] The primary wear ring and the secondary wear ring are used as wearing parts between the rotating assembly and the stator assembly. For a long time, the commonly used wear rings are mostly made of bronze, which is acid and alkali resistant, wear-resistant, and has good lubricity. The running clearance between the wear ring and the rotating assembly directly affects the operating efficiency of the pump. If the clearance is too large, the amount of liquid flowing back through the clearance will be too large, reducing the volumetric efficiency of the centrifugal pump; if the clearance is too small, it may cause the wear ring to touch the rotating assembly, aggravating the wear, or causing the centrifugal pump rotor and stator to bite.

[0017] The wear ring of this high-pressure multistage centrifugal pump adopts a new type of high-molecular wear-resistant thermosensitive polymer Vesconite. The non-metallic wear ring has high load-bearing capacity, good wear resistance, low friction coefficient, certain self-lubricating properties, easy processing, and can operate within a strict tolerance range.

[0018] This allows the high-pressure, high-speed, multi-stage centrifugal pump to operate at high speeds. The operating clearance is extremely small, 0.05 to 0.15 mm, which reduces volume loss, improves pump operation efficiency, and reduces 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 submerged bearing is also provided between the balance drum and the suction section. The material of the submerged bearing is also the aforementioned high molecular wear-resistant thermosensitive polymer Vesconite. The operating clearance between the inner ring of the submerged 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. It can operate continuously well under harsh operating conditions and has a long service life.

[0020] In addition, a sealing body is installed between the discharge section and the bearing seat, and the pump shaft passes through the sealing body. A containerized high-pressure mechanical sealing component is installed between the pump shaft and the sealing body. A balancing chamber is provided between the left side of the sealing body and the balancing drum. The medium is still under high pressure after the primary balancing action of the balancing drum. It is connected to the low-pressure area of ​​the suction port of the suction section through the balancing pipe for secondary balancing, thereby protecting the mechanical sealing components and bearing components on the right side and extending their service life.

[0021] Among them, the containerized high-pressure mechanical seal components include high-pressure mechanical seal components, sleeves, sealing rings, balance rings, mechanical seal glands, etc. The left side of the mechanical seal cavity is the medium pressure after the balance drum and balance pipe are double balanced, and the right side is the mechanical seal gland, which is equipped with a metal flushing pipe to connect the cavity composed of the first-stage impeller and the first-stage middle section to form a reflux path to flush and dissipate heat for the components in the mechanical seal cavity, improve lubrication conditions, prevent dry operation, and effectively extend 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, back-to-back angular contact ball bearings are arranged side by side in the right bearing seat, and 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 from the root.

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

[0025] In addition, in the present invention, the suction section, middle section, guide vane, impeller and discharge section and other flow-through parts are all made of duplex steel. It combines the excellent properties of ferrite steel and austenite two-phase stainless steel, has good pitting resistance and high stress and strain resistance, and is resistant to high pressure. It is widely used in RO water treatment, seawater desalination and other fields.

[0026] Compared with the prior art, the present invention has the following beneficial effects: 1. In actual use, by increasing or decreasing the number of middle sections and impeller components, different power outputs can be provided, thereby better meeting the pressure output requirements of different levels for primary and secondary treatments in the field of reverse osmosis; 2. The present invention has a simple structure, a smaller volume, and saves space. The pump body and the impeller assembly are both casting parts, and maintenance is convenient and flexible; 3. The present invention operates continuously and smoothly, has a wide performance range, low noise, and long service life, and can obtain different flow rates and output pressures through valve throttling or frequency conversion control. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of an existing plunger pump; Figure 2 It is a structural schematic diagram of the present invention; Figure 3 is a schematic structural diagram of an impeller assembly in an embodiment; Figure 4 is a schematic diagram of the structure of the blade in the embodiment; Figure 5 is a schematic structural diagram of the water inlet surface of the guide vane in the embodiment; Figure 6 It is a schematic diagram of the end structure of the present invention; Figure 7 This is a top view of the present invention; Figure 8 It is a flowchart of the control unit of the present invention.

[0028] 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, blades; 53, rear cover plate; 54, rear hub; 6, balance assembly; 60, balance drum; 61, balance disk; 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 throwing ring; 200, balance pipe; 201, flushing pipe. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0030] See also Figure 2-Figure 7 The present invention provides a technical solution: a high-pressure and high-speed multistage centrifugal pump that can replace a plunger pump, comprising a pump body, the pump body comprising 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, 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, the balancing assembly 6 and A mechanical seal assembly 7, a plurality of impeller assemblies 5 are sequentially arranged on the outer wall of the pump shaft 4 along the direction of water flow, the plurality of impeller assemblies 5 are spaced apart from the middle section 102, a plurality of 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 provided with a mechanical seal assembly 7 and a bearing seat 3, the two ends of the pump shaft 4 are respectively mounted inside the suction section 100 and the bearing seat 3, an oil seal 11 is mounted on the outer wall of the bearing seat 3, and the bearing seat 3 components include a sleeve 21, a double-row rolling bearing 22, a locking nut assembly 23, a labyrinth ring 24, and an oil slinger 25.

[0031] 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.

[0032] like Figure 4 As shown, in this embodiment, six blades 52 are evenly distributed on the impeller assembly 5 along the circumferential direction of the pump shaft 4, the thickness of the blade 52 increases first and then decreases from the blade root, and the blade tail of the blade 52 is beveled. In actual use, since water flows into the blade 52 from the blade root and then is thrown out from the blade tail, the hydraulic loss and clearance loss of the water flow at the blade root and blade tail can be reduced by increasing the thickness of the blade 52 from the blade root and then decreasing, and the hydraulic loss can be reduced by beveling the blade tail of the blade 52, thereby improving the working efficiency of the present invention.

[0033] Specifically, in this embodiment, the middle section 102 includes a first cavity and a second cavity, and 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, 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, and 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. The materials of the primary wear ring 8 and the secondary wear ring 9 are both polymer composite materials.

[0034] The polymer composite material is Vesconite, and the friction coefficient of the primary wear ring 8 and the secondary wear ring 9 is between 0.13 and 0.18, which is equivalent to half of bronze or nylon. It can run at 4000-5000RPM or higher speed conditions, has good wear resistance and long service life. In addition, the running clearance of the primary wear ring 8 and the secondary wear ring 9 is small, between 0.05 and 0.15mm, which reduces the volume loss, improves the operating efficiency of the pump and reduces the maintenance time and cost.

[0035] The existing primary wear ring 8 and secondary wear ring 9 are made of metal materials such as bronze. Although bronze is acid-resistant, wear-resistant and has certain lubricity, the primary wear ring 8 and secondary wear ring 9 made of metal materials have problems in actual use. In the present invention, since the non-metal primary wear ring 8 and secondary wear ring 9 have the advantages of high load-bearing capacity, good wear resistance, low friction coefficient, certain self-lubricating performance, easy processing and can run within a strict tolerance range, the present invention can be operated at a high speed, and the operating clearance is between 0.05 and 0.15 mm, which reduces volume loss and maintenance time and cost, and improves the operation efficiency of the pump.

[0036] 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 convert 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.

[0037] like Figure 2 As 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 communicated with the interior of the suction section 100 through the balance pipe 200 .

[0038] from 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 disk 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 disk 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.

[0039] The process of balancing the axial force of the balancing assembly 6 in this embodiment is as follows: The pressurized liquid coming out of the impeller assembly 5 on the far right is decompressed from the radial irregular gap of the balance drum 60 and flows into the balance chamber 10, and the balance chamber 10 is in a high-pressure state. After the balance sleeve and the balance disc 61 are combined, the balance pipe is connected to the low pressure of the suction section 100, and its pressure is approximately the inlet pressure. Due to the unequal pressure on both sides, a backward axial thrust is generated, which is opposite to the axial force, and thus automatically balances the axial thrust of the rotor. When the axial thrust of the impeller assembly 5 is greater than the balancing force of the balance disc 61, the pump shaft 4, the impeller assembly 5 and the balance drum 61 will move toward the suction section 100. This movement will cause the axial clearance of the balance disc 61 to be excessively reduced, so that the leakage is reduced and the pressure of the balance chamber 10 is increased, so that the balancing force on the balance disc 61 increases, and finally reaches the axial thrust of the impeller assembly 5, and the pump shaft 4, the impeller assembly 5 and the balance drum 60 are moved toward the discharge section 101, forming an automatic balance.

[0040] In addition, the material of the intermediate bearing in this embodiment is also Vesconite, and 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 on one side. It has high efficiency and internal self-lubrication, and can operate continuously well under harsh operating conditions and has a long service life.

[0041] like 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 mounted on the discharge section 101. A mechanical seal cavity is provided in the seal body 70. The mechanical seal component 71 is mounted 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 between the pump shaft 4 and the seal body 70. Figure 8 As shown, the mechanical seal chamber is connected to the first-stage flow channel chamber composed of the first-stage impeller and the first-stage middle section through the flushing pipe 201. In actual use, the mechanical seal component 71 can be flushed and heat dissipated through the flushing pipe 201.

[0042] like Figure 7 As 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 Figure 7 In the middle, there are labyrinth rings 24, 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 slinger 25, the locking nut assembly 23 and the second labyrinth ring. The double-row rolling shaft 22 is sleeved on the sleeve 21. The first labyrinth ring and the second labyrinth ring are connected to the bearing seat 3 through connecting parts, wherein the connecting parts can be screws.

[0043] In addition, in this embodiment, the materials of the suction section 100, the middle section 102, the discharge section 101, the guide vane 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.

[0044] 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 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 on 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.

[0045] 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, the motor rotational speed is related to the power frequency output by the inverter, and 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.

[0046] 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.

[0047] In this embodiment, the reference voltage setting unit is used to set the size of the set voltage representing the size of 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 conversion result of the set voltage and 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 end 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 reduces the output value of the digital-to-analog conversion unit, thereby reducing the voltage input to the voltage control signal input end of the frequency converter, reducing the pump shaft speed and the water flow rate, when the set voltage is the same as the analog signal, the main control unit keeps the output value of the analog-to-digital conversion unit unchanged, thereby ensuring the stability of the pump shaft speed and the water flow rate. In addition, the buffer can ensure the stability of the voltage input to the voltage control signal input end of the frequency converter.

[0048] The above is based on the present invention as an inspiration. Through the above description, relevant staff can make various changes and modifications without departing from the technical idea of ​​this invention. The technical scope of this invention is not limited to the content in 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); 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 impeller assemblies (5) in sequence along the water flow direction; the plurality of impeller assemblies (5) and the middle section (102) are arranged at intervals; the plurality of 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 provided with a mechanical seal assembly (7) and a bearing seat (3); the two ends of the pump shaft (4) are respectively mounted inside the suction section (100) and the bearing seat (3); an oil seal (11) is mounted on the outer wall of the bearing seat (3); and the bearing seat (3) comprises 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); 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 of the blades (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 slinger (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 slinger (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. A 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) comprises 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. A 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) is installed inside the discharge section (101); a mechanical seal cavity is provided inside the seal body (70); the mechanical seal component (71) is installed at the center of 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 between the pump shaft (4) and the seal body (70); the impeller assembly (5) and the middle section (102) constitute a first-stage flow channel cavity; a flushing pipe (201) is connected between the mechanical seal cavity and the first-stage flow channel cavity.

10. A high-pressure, high-speed, multi-stage centrifugal pump that can replace a plunger pump according to claim 1, characterized in that: It 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 mounted on one side of the discharge section (101), 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 arranged 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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