Contra-rotating multiphase pump system

Abstract

The invention belongs to the technical field of pumps, and particularly relates to a contra-rotating multiphase pump system which comprises a pump body, a collecting tank and a filter, and a pump outlet is connected with a tank inlet of the collecting tank through a pumping pipeline; and part of the liquid-phase material in the collecting tank is supplemented into the pump body after passing through the filter, so that the proportion of the liquid-phase material in the pumped material in the pump body is at least maintained at a set threshold value. If the proportion of the liquid-phase material in the multi-phase material is smaller than a set threshold value, slug flow can be formed, the slug flow can cause violent fluctuation of liquid holdup and pressure in the pipeline, so that the oil-gas mixed transportation pipeline running under the flow pattern bears pulse stress impact, and further the pipeline and equipment connected with the pipeline can be damaged; when the proportion of the liquid-phase materials in the multi-phase materials is smaller than a set threshold value, the liquid-phase materials in the collecting tank are supplemented into the pump shell, the proportion of the liquid-phase materials in the multi-phase materials is increased, and slug flow is avoided.

Description

[0001] This application claims priority to Chinese Patent Application No. 202510120378.3, filed on January 25, 2025, entitled “A Counter-rotating Mixed Pump”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention belongs to the field of pump technology, specifically relating to a counter-rotating mixed-transport pump system. Background Technology

[0003] In recent years, with the advancement of oil extraction technology, offshore oil and gas field development has gradually expanded from onshore extraction to deep-water offshore oil and gas fields. However, the development of oil and gas fields faces a series of technical and engineering challenges, including the inability of low-pressure reservoirs to flow spontaneously, insufficient reservoir pressure in the later stages of oil and gas field development, excessively high water cut in gas fields, and low gas recovery rates. These challenges not only affect the extraction efficiency of oil and gas fields but also impact their safety and economic benefits. Therefore, it is necessary to develop more effective technologies to improve the safety and economics of oil and gas fields. Among these, multiphase pressurization technology for offshore platforms has emerged as one of the key technologies for solving the aforementioned problems.

[0004] Multiphase pressurization technology for offshore platforms is a cutting-edge technology integrating offshore platform pressurization and multiphase pressurization, effectively solving some of the challenges faced in oil and gas field development. With the continuous development of offshore oil and gas resources, especially the increasing demand for oil and gas field extraction, traditional single-phase pressurization technologies (such as gas boosters and single-phase pumps) can no longer meet the requirements of oil and gas fields because they have limitations in handling fluids with different physical properties (gas, liquid, solid, etc.). Unlike traditional pressurization technologies, multiphase pressurization technology does not require separation equipment to separate and process fluids such as oil, gas, and water; instead, it directly processes mixed multiphase fluids. During oil and gas extraction, the properties of the oil, gas, and water mixture are constantly changing. Traditional pressurization equipment is usually unable to effectively handle fluids with high gas and water content, requiring solutions to cavitation problems common in single-phase pumps and surge phenomena in compressor pressurization. Therefore, designing a pressurization device that can effectively pressurize and cope with the challenges of multiphase fluids has become a key issue in multiphase pressurization technology.

[0005] Specifically, the working principle of multiphase pressurization technology is to directly pressurize a mixture of gas, oil, and water with a gas-liquid ratio between 0% and 100% using specially designed pressurization equipment, thus achieving multiphase fluid pressurization. In offshore oil and gas extraction, the presence of gas, oil, and water mixtures alters the flow characteristics of the fluid, a change that traditional single-phase pressurization technology cannot handle. Therefore, multiphase pressurization technology for offshore platforms not only needs to address pressurization cavitation but also how to effectively pressurize fluids with high gas and water content. Currently, multiphase pressurization technology for offshore platforms has been applied in several offshore oil and gas field projects with good results. With continuous technological development, several main multiphase pressurization technologies for offshore platforms have emerged, including helical axial flow multiphase pressurization technology, twin-screw multiphase pressurization technology, counter-rotating impeller multiphase pressurization technology, semi-axial flow blade technology, and centrifugal pressurization technology. Each of these technologies has its own characteristics and has been applied and validated in different oil and gas fields.

[0006] Despite the significant achievements of multiphase pressurization technology on offshore platforms in offshore oil and gas field development, several challenges remain in practical applications. First, the design and manufacture of pressurization equipment for offshore platforms must consider the complexity of the external environment, such as high pressure, low temperature, and corrosion, requiring sufficient durability and reliability. Second, as oil and gas field development progresses, the pressure in the reservoir decreases rapidly, placing higher demands on multiphase pressurization equipment on offshore platforms. Maintaining the stability and efficiency of pressurization equipment under extreme operating conditions is a pressing technological challenge.

[0007] However, with the continuous advancements in materials science, mechanical engineering, and fluid mechanics, the application prospects of multiphase pressurization technology for offshore platforms remain very broad. In the future, with continuous optimization of offshore platform pressurization technology, new pressurization equipment and technologies will continue to emerge to meet the increasingly demanding development needs of oil and gas fields. At the same time, multiphase pressurization technology for offshore platforms will continue to demonstrate its enormous potential in improving oil and gas field recovery rates, extending oilfield lifecycles, and reducing development costs. As a key technology in oil and gas field development, multiphase pressurization technology for offshore platforms has already been applied in numerous projects and achieved significant results. With continuous technological development and improvement, multiphase pressurization technology for offshore platforms will continue to provide strong support for the efficient exploitation of global offshore oil and gas resources, promoting the sustainable development of the offshore oil and gas industry.

[0008] Counter-rotating impellers are a variation of axial flow blades. The impeller body is positioned opposite each other, and a pair of motors rotating in opposite directions drive the moving and stationary blades of a conventional axial flow compressor, with variable frequency speeds for adjustment. Because the moving and stationary blades of the mixed-flow pump rotate relative to each other, good pressurization effects can usually be achieved at relatively low speeds. A significant feature of this device is its large flow rate; however, due to its operating principle being similar to that of an axial flow compressor, it only achieves truly ideal conveying performance when the gas content is above 90%.

[0009] From a process perspective, the counter-rotating mixed-transfer pump system does not require gas-liquid separation. The material directly enters the pump inlet and is pressurized by the counter-rotating rotor. After pressurization, the oil and gas are transported downstream through a cooler at the outlet. The counter-rotating mixed-transfer pump system effectively solves the surge problem.

[0010] The counter-rotating mixed-transfer pump system comprises an upper motor, a lower motor, and a set of counter-rotating compressor sections. The lower motor drives the lower shaft, which rotates the inner hub within the mixed-transfer pump section, with the impeller fixed to the inner hub. Similarly, the upper motor drives the upper shaft, which rotates the outer casing within the mixed-transfer pump section, with the impeller fixed to the outer casing. Notably, the upper and lower shafts rotate in opposite directions. The mixed-transfer pump section has an inlet and an outlet. The mixed-transfer pump section features staggered impellers mounted on the inner hub and outer casing, stacked sequentially on top of each other, and rotating in opposite directions. However, the pump's outlet is high-pressure, and the motor connection near the outlet experiences significant pressure, leading to severe sealing problems, resulting in a very complex pump structure and susceptibility to damage.

[0011] In addition, current counter-rotating mixed-transport pump systems face another problem: slug flow. Slug flow is a flow pattern that appears after bubble flow in vertical gas-liquid two-phase pipe flow. In flowing oil wells, slug flow, bubble flow, and pure oil flow are more common, while annular flow and mist flow are more common in high-yield condensate gas wells and water-producing gas wells with a large gas-liquid volume ratio. The formation process of slug flow is as follows: as the pressure decreases, the amount of gas separated from the oil increases. The separated bubbles expand, grow larger, and aggregate, forming projectile-shaped bubbles close to the pipe diameter, dividing the liquid into slugs, hence the name slug flow. In this process, the bubble velocity is much greater than the liquid velocity, pushing the liquid plug like a leaking piston, while the liquid remains a continuous phase. At the same time, a liquid film forms on the pipe wall outside the bubbles, and both the gas and liquid phases affect the frictional pressure loss.

[0012] The main characteristics of slug flow are the changes in pressure and differential pressure during the transient process of gas volume in mixed-gas pipelines. As a common flow pattern in oil and gas mixed-gas pipelines, slug flow causes drastic fluctuations in liquid holdup and pressure due to the alternating phases of gas and liquid. This inevitably subjects oil and gas mixed-gas pipelines operating under this flow pattern to pulse stress impacts, potentially leading to damage to the pipeline and connected equipment. Specifically, when slug flow passes through a pipeline, bubbles and liquid plugs appear alternately. As bubbles rise, they continuously expand, pushing the liquid plugs forward and simultaneously generating periodic impacts on the pipeline wall. These impacts cause periodic pressure fluctuations within the pipeline, with significant differences between peak and trough pressures, and the fluctuation frequency is related to factors such as the slug flow velocity and gas-liquid ratio. Furthermore, the liquid holdup in the pipeline also changes significantly with the slug flow, with higher holdup in the liquid plug section and lower holdup in the bubble section. This fluctuation in holdup further exacerbates pressure instability.

[0013] Long liquid plugs leaving the end of the pipeline can cause drastic fluctuations in the liquid level of downstream oil and gas processing equipment, thus affecting normal production. In oil and gas mixed transportation systems, downstream processing equipment, such as separators and buffer tanks, typically requires stable liquid levels to ensure their normal operation. When a long liquid plug from a slug flow enters these devices, it instantly increases the liquid level within the equipment, causing it to operate under overload and potentially leading to overflows or other safety accidents. After the plug passes, the liquid level in the equipment drops rapidly, leaving it operating at a low liquid level, affecting the oil and gas separation effect and subsequent processing. These drastic fluctuations in liquid level not only disrupt the normal operation of the equipment but also reduce the production efficiency and stability of the entire oil and gas mixed transportation system. Summary of the Invention

[0014] The purpose of this invention is to overcome the shortcomings of the prior art and provide a counter-rotating mixed pump system that is simple in structure and stable and reliable in operation.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is: a counter-rotating mixed-transfer pump system, including a pump body, a collection tank, and a filter. The pump body has a pump inlet and a pump outlet, and the pump outlet is connected to the inlet of the collection tank through a pumping pipeline. The pump body includes a pump casing, a booster pumping component, and a power component. The booster pumping component is disposed inside the pump casing, and the power component is connected to the booster pumping component. Part of the liquid phase material in the collection tank is replenished into the pump body after passing through the filter, so that the proportion of liquid phase material in the material pumped in the pump body is maintained at least at a set threshold.

[0016] Preferably, the set threshold is 5% of the volume ratio.

[0017] Preferably, the collection tank is connected to the filter through a return pipe, and an outer cover is provided on the outside of the pump casing. The outer cover is provided with a mixed transport inlet, and a low-pressure inlet is provided on the pump casing. Low-pressure multiphase materials enter the outer casing from the main inlet of the mixing and conveying system. The low-pressure multiphase materials inside the outer casing enter the pump casing from each low-pressure inlet. When the proportion of liquid material in the multiphase materials inside the outer casing is less than 5%, the return pipe is opened, and the collection tank replenishes the pump body with liquid material.

[0018] Preferably, the collection tank is connected to a heating mechanism for heating the liquid material.

[0019] Preferably, the filter is connected to a cooling mechanism for cooling the liquid material.

[0020] Preferably, the medium in the pumping pipeline enters the collection tank after passing through the gas-liquid separation mechanism, and the outlet of the collection tank is connected to the output pipe, with the outlet being higher than the inlet.

[0021] Preferably, the booster pumping assembly includes a first impeller and a second impeller, and the power assembly includes a first power unit and a second power unit. The first impeller is disposed inside the second impeller, and the pump casing is disposed outside the second impeller. The pump casing is provided with a low-pressure inlet and a high-pressure outlet. The first impeller and the second impeller are provided with a plurality of blades. The first power unit is connected to the first impeller, and the second power unit is connected to the second impeller. Both the first power unit and the second power unit are disposed on the low-pressure inlet side of the pump casing. The second power unit has a hollow structure. The output shaft of the first power unit passes through the second power unit and is connected to the first impeller, or the first impeller passes through the second power unit and is connected to the first power unit.

[0022] Preferably, a toothed sealing structure is provided between the pump casing and the second impeller.

[0023] Preferably, the toothed sealing structure includes a plurality of sealing teeth disposed on the outside of the second impeller and a plurality of sealing teeth disposed on the inside of the pump casing, the plurality of sealing teeth being spaced apart along the axial direction of the second impeller, and the plurality of sealing teeth on the outside of the second impeller and the plurality of sealing teeth inside the pump casing being staggered; or it includes a plurality of sealing teeth disposed on the outside of the second impeller, the plurality of sealing teeth being spaced apart along the axial direction of the second impeller; or it includes a plurality of sealing teeth disposed on the inside of the pump casing, the plurality of sealing teeth being spaced apart along the axial direction of the second impeller.

[0024] Preferably, the toothed sealing structure includes a spiral sealing structure outside the second impeller or a spiral sealing structure disposed inside the pump casing.

[0025] Preferably, both the first power unit and the second power unit are shielded motors.

[0026] Preferably, the pump casing is further provided with an outer cover, which has a mixed transport inlet and multiple low-pressure inlets on the pump casing.

[0027] Preferably, the end of the second impeller near the low-pressure inlet is connected to the output shaft of the second power unit via a connecting flange.

[0028] Preferably, bearings are provided on the outer side of the first impeller, the second impeller, and the output shafts of the first motor and the second motor, and bearing lubrication pipes are provided between the filter and each bearing.

[0029] Preferably, it also includes a motor housing, and the first motor and the second motor are disposed inside the motor housing.

[0030] Preferably, it also includes an outer cover, which is located on the outside of the pump casing. The outer cover is provided with a mixed conveying main inlet, and the pump casing is provided with multiple low-pressure inlets. The low-pressure inlets are the pump inlet, and the high-pressure outlet is the pump outlet. The liquid phase material in the collection tank passes through the filter and then enters the pump casing through the mixed conveying main inlet and the low-pressure inlet in sequence.

[0031] Preferably, the medium in the pumping pipeline enters the collection tank after passing through the gas-liquid separation mechanism, and the outlet of the collection tank is connected to the output pipe, with the outlet being higher than the inlet.

[0032] Preferably, the filter is disposed between the collection tank and the pump body.

[0033] Compared with existing technologies, the above technical solution has the following beneficial effects: 1. If the proportion of liquid phase material in a multiphase material is less than a set threshold, slug flow will form. Slug flow will cause drastic fluctuations in liquid holdup and pressure in the pipeline, causing the oil and gas mixed transport pipeline operating under this flow pattern to be subjected to pulse stress impact, which may lead to damage to the pipeline and the equipment connected to the pipeline. It will also cause friction overheating in the pump body. Therefore, a collection tank is installed. When the proportion of liquid phase material in the multiphase material is less than the set threshold, the liquid phase material in the collection tank is replenished into the pump casing to increase the proportion of liquid phase material in the multiphase material and avoid the occurrence of slug flow.

[0034] 2. In this invention, both the first power unit and the second power unit are located on the low-pressure inlet side of the pump casing. The second power unit is a hollow structure. The output shaft of the first power unit passes through the second power unit and connects to the first impeller, or the first impeller passes through the second power unit and connects to the first power unit. The pressure of the multiphase material on the low-pressure inlet side is low, and the multiphase material has little impact on the sealing of the connection between the first and second power units. This extends the service life of the power units and avoids the connection from bearing large pressure, which could lead to serious sealing problems and make the power units prone to damage.

[0035] 3. A portion of the liquid material returning from the collection tank is transported to each bearing of the motor through the bearing lubrication pipeline to cool and lubricate the bearings. At the same time, by transporting liquid material to each bearing, similar to the principle of air-floating bearings, the bearings are aligned so that each bearing is coaxial with the output shaft.

[0036] 4. A toothed seal structure is provided between the pump casing and the second impeller. Even if the high-pressure medium leaks from between the second impeller and the pump casing to the low-pressure inlet end, the high-pressure medium will be depressurized layer by layer as it passes through the toothed seal structure. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the rotary mixed-transmission pump system of the present invention.

[0038] Figure 2 for Figure 1 Enlarged view of point A in the middle.

[0039] Figure 3 This is a schematic diagram of the light oil recovery process of the present invention.

[0040] The components include: 1. Mixed transport inlet; 2. Outer casing; 3. Pump casing; 4. Pump end cover; 5. High pressure outlet; 6. First impeller; 7. Second impeller; 8. Toothed seal structure; 9. Low pressure inlet; 10. Second motor; 11. First motor; 12. Hollow shaft; 13. Connecting flange; 14. Solid shaft; 15. Thrust bearing; 16. Sliding bearing; 17. Motor housing; 18. Pump body; 19. Pumping pipeline; 20. Collection tank; 21. Output pipe; 22. Heating mechanism; 23. Return pipe; 24. Filter; 25. Bearing lubrication pipeline; 26. Supplementary pipeline; 27. Cooling mechanism. Detailed Implementation

[0041] Figures 1-3 This is the preferred embodiment of the present invention, which is described below in conjunction with the accompanying drawings. Figures 1-3 The present invention will be further described below.

[0042] like Figure 1As shown, a counter-rotating mixed-transfer pump of the present invention includes a pump casing 3, a first impeller 6, a second impeller 7, a first power unit, and a second power unit. The first impeller 6 is disposed inside the second impeller 7. A plurality of blades are provided on the outer side of the first impeller 6 and the inner side of the second impeller 7, and the blades of the first impeller 6 and the second impeller 7 are arranged in an alternating pattern. The pump casing is disposed outside the second impeller 7 and has a low-pressure inlet 9 and a high-pressure outlet 5. Low-pressure multiphase material is introduced into the low-pressure inlet 9, and high-pressure multiphase material is pumped out from the high-pressure outlet 5. The first power unit is connected to the first impeller 6, and the second power unit is connected to... The second impeller 7, in this invention, both the first power unit and the second power unit are located on the low-pressure inlet 9 side of the pump casing 3. Since the first impeller 6 and the second impeller 7 are coaxially arranged, the second power unit is set as a hollow structure. The output shaft of the first power unit passes through the second power unit and connects to the first impeller 6, or the first impeller 6 passes through the second power unit and connects to the first power unit. The first impeller 6 and the second impeller 7 rotate in opposite directions. The pressure of the multiphase material on the low-pressure inlet 9 side is small, and the multiphase material has little impact on the sealing at the connection between the first power unit and the second power unit, thereby extending the service life of the power unit.

[0043] In this embodiment, both the first power unit and the second power unit are shielded motors. The first power unit is the first motor 11, and the second power unit is the second motor 10. The second motor 10 has a hollow structure and is located near the low-pressure end of the first impeller 6 and the second impeller 7. The output shaft of the second motor 10 is a hollow shaft 12, which is connected to the low-pressure end of the second impeller 7 through a connecting flange 13. The first motor 11 is connected to the side of the second motor 10 away from the impeller. The output of the first motor 11 is a solid shaft 14, which passes through the middle of the hollow shaft 12 and is connected to the low-pressure end of the first impeller 6.

[0044] A motor housing 17 is provided outside the first motor 11 and the second motor 10. An outer cover 2 is provided outside the pump housing 3. A mixing inlet 1 is provided on the outer cover 2. Low-pressure multiphase materials enter the outer cover 2 from the mixing inlet 1. Multiple low-pressure inlets 9 are provided at the lower part of the pump housing 3. Low-pressure multiphase materials in the outer cover 2 enter the pump housing 3 from each low-pressure inlet 9. Multiple high-pressure outlets 5 are provided on the upper side of the pump housing 3. After being pressurized by the mixing pump, the high-pressure multiphase materials are pumped out from the high-pressure outlets 5. A pump end cover 4 is provided at the high-pressure end of the mixing pump. An output port is provided on the pump end cover 4. The output port is connected to the pumping pipeline 19 to pump out the high-pressure mixed medium.

[0045] like Figure 2As shown, a toothed sealing structure 8 is provided between the pump casing 3 and the second impeller 7. The toothed sealing structure 8 is a non-contact seal. In this embodiment, the toothed sealing structure 8 includes a number of sealing teeth disposed on the outside of the second impeller 7 and a number of sealing teeth disposed on the inside of the pump casing 3. The number of sealing teeth are spaced apart along the axial direction of the second impeller 7, and the number of sealing teeth on the outside of the second impeller 7 and the number of sealing teeth on the inside of the pump casing 3 are staggered but not crossed. Even if the high-pressure medium leaks from the second impeller 7 and the pump casing 3 to the low-pressure end, the high-pressure medium will be depressurized layer by layer after passing through the toothed sealing structure 8.

[0046] In other embodiments, the toothed sealing structure 8 may include only a number of sealing teeth disposed on the outside of the second impeller 7 or only a number of sealing teeth disposed on the inside of the pump casing 3.

[0047] In other embodiments, the toothed sealing structure 8 may also be a spiral sealing structure including the outside of the second impeller 7 or a spiral sealing structure disposed inside the pump casing 3. The spiral sealing structure can allow the multiphase material at the low pressure end to be spirally conveyed to the high pressure end along the spiral sealing structure, thereby further preventing the high pressure multiphase material from leaking to the low pressure end.

[0048] like Figure 3 As shown, a counter-rotating mixed-transfer pump system of the present invention includes a pump body 18, a collection tank 20 and a filter. The pump body 18 has a pump inlet and a pump outlet. Low-pressure multiphase material enters from the pump inlet, and the pump outlet is connected to the inlet of the collection tank 20 through a pumping pipeline 19. After passing through the pump body 18, the low-pressure multiphase material is pumped from the pump outlet to the collection tank 20.

[0049] The pump body 18 includes a pump casing 3, a booster pumping assembly, and a power assembly. The booster pumping assembly is located inside the pump casing 3, and the power assembly is connected to the booster pumping assembly. The booster pumping assembly includes a first impeller 6 and a second impeller 7. The power assembly includes a first motor and a second motor. The pump casing 3 is located outside the second impeller 7. The pump casing 3 is provided with a low-pressure inlet 9 and a high-pressure outlet 5. The low-pressure inlet 9 is the pump inlet, and the high-pressure outlet 5 is the pump outlet. The first impeller 6 and the second impeller 7 are provided with a number of blades. The first motor is connected to the first impeller 6, and the second motor is connected to the second impeller 7. The first impeller 6 and the second impeller 7 rotate in opposite directions.

[0050] Low-pressure multiphase materials enter the pump casing 3 through the low-pressure inlet 9. After passing through the collection tank 20, some of the liquid phase material is filtered and then replenished into the pump body 18, ensuring that the proportion of liquid phase material in the pumped material in the pump body 18 is maintained at least at a set threshold. The proportion of liquid phase material is generally a volume ratio, but it can also be a mass ratio. If the proportion of liquid phase material in the multiphase material is less than the set threshold, slug flow will occur. Therefore, the collection tank 20 is set up. When the proportion of liquid phase material in the multiphase material is less than the set threshold, the liquid phase material in the collection tank 20 is replenished into the pump body 18 to increase the proportion of liquid phase material in the multiphase material and avoid the occurrence of slug flow.

[0051] The medium in the pumping pipeline 19 enters the collection tank 20 after passing through the gas-liquid separation mechanism. The outlet of the collection tank 20 is connected to the output pipe 21, and the outlet is set higher than the inlet. A filter is set between the collection tank 20 and the pump body 18. The collection tank 20 is connected to a heating mechanism 22 for heating the liquid material, and the filter 24 is connected to a cooling mechanism 27 for cooling the liquid material. After the heating mechanism 22 heats the liquid material in the collection tank 20, it facilitates the return of the liquid material. After being cooled by the cooling mechanism 27, the liquid material is transported to the pump body 18 to facilitate the cooling of the pump body 18.

[0052] It also includes an outer cover 2, which is located outside the pump casing 3. The outer cover 2 is provided with a mixed transport inlet, and the pump casing 3 is provided with multiple low-pressure inlets 9. After the liquid phase material in the collection tank 20 is heated by the heating mechanism 22, it is transported to the filter 24 through the return pipe 23. After being cooled by the cooling mechanism 27 in the filter 24, it enters the pump casing 3 through the mixed transport inlet 1 and the low-pressure inlet 9 in sequence to replenish the proportion of liquid phase material in the multiphase material. In this embodiment, the threshold is set to a volume ratio of 5%. When the proportion of liquid phase material in the multiphase material in the outer cover 2 is less than 5%, the return pipe 23 is opened, and the collection tank 20 replenishes the liquid phase material into the pump body 18.

[0053] Bearings are provided on the outer side of the first impeller 6, the second impeller 7, the first motor 11, and the second motor 10 output shafts. The bearings include thrust bearings 15 and sliding bearings 16. A bearing lubrication pipe 25 is provided between the filter and each bearing. The bearing lubrication pipe 25 is connected to the filter 24. The liquid material output from the return pipe 23 enters the filter 24. After being filtered by the filter 24 and cooled by the cooling mechanism 27, part of the liquid material enters the pump body 18 through the replenishment pipe 26 to replenish the proportion of liquid material and cool the pump body 18. Part of the liquid material enters each bearing through the bearing lubrication pipe 25 to achieve cooling and lubrication of each bearing. At the same time, by conveying liquid material to each bearing, similar to the principle of air bearing, each bearing is aligned so that each bearing is coaxial with the output shaft.

[0054] In use, the first motor 11 and the second motor 10 are located on the low-pressure inlet 9 side of the pump casing 3. The second motor 10 has a hollow structure, and its output shaft is a hollow shaft 12. The hollow shaft 12 of the second motor 10 is connected to the low-pressure end of the second impeller 7 through a connecting flange 13. The first motor 11 is connected to the side of the second motor 10 away from the impeller. The output of the first motor 11 is a solid shaft 14, which passes through the middle of the hollow shaft 12 and connects to the low-pressure end of the first impeller 6. The pressure of the multiphase material on the low-pressure inlet side is low, and the multiphase material has little impact on the sealing of the motor connection, thereby extending the service life of the motor.

[0055] Low-pressure multiphase material enters through the pump inlet, and the pump outlet is connected to the inlet of the collection tank 20 via the pumping pipeline 19, pumping the high-pressure multiphase material to the collection tank 20. The upper side of the collection tank 20 is provided with an outlet and connected to the outlet pipe 21 to output the multiphase material. The collection tank 20 is connected to the filter 24 via the return pipe 23. After the liquid phase material is heated in the collection tank 20, it is filtered and cooled by the filter 24, and then connected to the pump body 18 via the replenishment pipeline 26 to replenish the liquid phase material and prevent slugging. Some of the liquid phase material is filtered and cooled by the filter 24 and then enters each bearing through the bearing lubrication pipeline 25 to cool and lubricate each bearing, and at the same time, to straighten each bearing and make each bearing coaxial with the output shaft.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A mixed flow pump system of the contra-rotating type, characterized in that: The pump body (18) has a pump inlet and a pump outlet, the pump outlet is connected with a tank inlet of the collecting tank (20) through a pumping pipeline (19); the pump body (18) comprises a pump shell (3), a booster pumping assembly and a power assembly, the booster pumping assembly is arranged in the pump shell (3), and the power assembly is connected with the booster pumping assembly; part of liquid-phase material in the collecting tank (20) is supplemented into the pump body (18) after passing through the filter (24), so that the proportion of the liquid-phase material in the pumped material in the pump body (18) is maintained at least at a set threshold.

2. A mixed flow pump system according to claim 1, wherein: The set threshold is 5% in volume ratio.

3. A mixed flow pump system according to claim 2, wherein: The collecting tank (20) is connected with the filter (24) through a backflow pipeline (23), the outer side of the pump shell (3) is further provided with an outer cover (2), the outer cover (2) is provided with a mixed-transport total inlet (1), and a low-pressure inlet (9) is arranged on the pump shell (3); The low-pressure multiphase material enters into the outer cover (2) from the mixed-transport total inlet (1), the low-pressure multiphase material in the outer cover (2) enters into the pump shell (3) from each low-pressure inlet (9), and when the proportion of the liquid-phase material in the multiphase material in the outer cover (2) is less than 5%, the backflow pipeline (23) is opened, and the collecting tank (20) supplements the liquid-phase material into the pump body (18).

4. A mixed flow pump system according to claim 1, wherein: The collecting tank (20) is connected with a heating mechanism (22) for heating the liquid-phase material.

5. A mixed flow pump system according to claim 1, wherein: The filter (24) is connected with a cooling mechanism (27) for cooling the liquid-phase material.

6. A mixed flow pump system according to claim 1, wherein: The medium of the pumping pipeline (19) enters into the collecting tank (20) after passing through a gas-liquid separation mechanism, the tank outlet of the collecting tank (20) is connected with an output pipeline (21), and the tank outlet is arranged higher than the tank inlet.

7. A mixed flow pump system according to claim 1, wherein: The booster pumping assembly comprises a first impeller (6) and a second impeller (7), the power assembly comprises a first power unit and a second power unit, the first impeller (6) is arranged on the inner side of the second impeller (7), the pump shell (3) is arranged on the outer side of the second impeller (7), the pump shell (3) is provided with the low-pressure inlet (9) and a high-pressure outlet (5), a plurality of blades are arranged on the first impeller (6) and the second impeller (7), the first power unit is connected with the first impeller (6), and the second power unit is connected with the second impeller (7); the first power unit and the second power unit are both arranged on the low-pressure inlet (9) side of the pump shell (3), the second power unit is in a hollow structure, an output shaft of the first power unit passes through the second power unit and is connected with the first impeller (6), or the first impeller (6) passes through the second power unit and is connected with the first power unit.

8. A mixed flow pump system according to claim 7, wherein: A gear-shaped sealing structure (8) is arranged between the pump shell (3) and the second impeller (7).

9. A mixed flow pump system according to claim 8, wherein: The tooth-shaped sealing structure (8) comprises a plurality of sealing teeth arranged outside the second impeller (7) and a plurality of sealing teeth arranged inside the pump shell (3), the plurality of sealing teeth are arranged at intervals along the axial direction of the second impeller (7), and the plurality of sealing teeth outside the second impeller (7) are arranged alternately with the plurality of sealing teeth inside the pump shell (3); or the tooth-shaped sealing structure (8) comprises a plurality of sealing teeth arranged outside the second impeller (7), and the plurality of sealing teeth are arranged at intervals along the axial direction of the second impeller (7); or the tooth-shaped sealing structure (8) comprises a plurality of sealing teeth arranged inside the pump shell (3), and the plurality of sealing teeth are arranged at intervals along the axial direction of the second impeller (7).

10. A mixed flow pump system according to claim 8, wherein: The tooth-shaped sealing structure (8) comprises a spiral sealing structure outside the second impeller (7) or a spiral sealing structure arranged inside the pump shell (3).

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