A gas-liquid mixed transportation low-noise three-screw pump

Abstract

The present invention relates to a gas-liquid mixed transportation low-noise three-screw pump, which has a pump body, a driving screw and two driven screws. The output shaft of the motor is fixedly connected to the driving shaft of the driving screw. A screw bushing is fixedly connected to the lower end surface of the connecting frame. An axial force balance drum of the driving screw is arranged between the upper part of the screw bushing and the driving shaft of the driving screw. The screw part of the driving screw is located in the screw bushing and is meshed and connected with the two driven screws. A pump body outlet cavity is arranged at the upper part of the pump body, and a pump body inlet cavity is arranged at the lower part. The screw bushing adopts a conchoidal profile streamline body shape, which can reduce vortexes and avoid violent collisions and impacts. The axial length of the screw bushing is greater than the spiral meshing part formed by the driving screw and the two driven screws, and an inlet cavity of the screw bushing and an outlet cavity of the screw bushing are formed, so that the part entering and flowing out of the spiral meshing part becomes a buffer zone, which can reduce the interference of the spiral flow channel on the inlet and outlet cavities of the pump body and is beneficial to low-noise operation.

Description

Technical Field

[0001] The present invention relates to the technical field of a three-screw pump for transporting lubricating media, in particular to a three-screw pump for low-noise transportation of a liquid with lubricating characteristics in a gas-containing state. Background Art

[0002] At present, it is very difficult for a three-screw pump to simultaneously achieve gas-liquid mixed transportation (that is, the transported medium contains a certain proportion of gas) and low noise. Although some design structures can improve this situation, the effect is often limited. Since the beginning of the design of the present invention, overall structures have been considered to lay a good foundation for low-noise gas-liquid mixed transportation, and then the sealed screw profile is designed into a non-sealed screw profile. Therefore, the present invention has great advantages in terms of vibration noise, external dimensions, and weight. Summary of the Invention

[0003] The present invention aims to provide a three-screw pump for low-noise gas-liquid mixed transportation, which is suitable for low-noise transportation of a lubricating medium liquid in a gas-containing state; has the advantages of a general design and is applicable to both low-pressure and high-pressure transportation. The overall structure of this three-screw pump has few components, and disassembly, installation, and maintenance are convenient.

[0004] To achieve the above object, the technical solution of the present invention is: a three-screw pump for low-noise gas-liquid mixed transportation, having a pump body, a driving screw, and two driven screws. The upper part of the pump body is fixedly connected to a motor through a connecting frame. The output shaft of the motor is fixedly connected to the driving shaft of the driving screw. A driving screw axial force balance drum is arranged between the upper part of the screw bushing fixedly connected to the lower end face of the connecting frame and the driving shaft of the driving screw. The screw part of the driving screw is located in the screw bushing of the pump body and is meshed with the two driven screws. The upper part of the pump body is provided with a pump body outlet cavity, and the lower part is provided with a pump body inlet cavity; the screw bushing adopts a conchoidal contour streamline body shape, which can reduce vortexes and avoid violent collisions and impacts. The axial length of the screw bushing is greater than the length of the spiral meshing part of the driving screw and the two driven screws, and forms an inlet cavity of the screw bushing and an outlet cavity of the screw bushing, so that the inlet and outlet of the spiral meshing part become a buffer zone, which can reduce the interference of the spiral flow channel on the pump body inlet cavity and the pump body outlet cavity, and is beneficial to low-noise operation.

[0005] Further, the pump body is a square pump body with a wide large arc chamfer, and the internal large cavity is beneficial to keeping the flow field in a low-speed state.

[0006] Further, the motor adopts a low-speed motor, so that the rotational linear speeds of the driving screw and the two driven screws are kept in a low rotational speed state.

[0007] Furthermore, the conchoidal contour streamline body shape of the screw bushing is formed by two conchoids with different constant quantities, and the contour lines formed by the conchoids are smoothly transitioned with large arcs.

[0008] Furthermore, the downward force F3 and upward force F4 along the axis on the driving screw and the downward force F5 and upward force F1 along the axis on the driven screw achieve axial force balance; the driving screw is in a tensile state under the action of the downward force F3 and upward force F4 along the axis to form a low-pressure balance, and the driven screw is in a compressive state under the action of the downward force F5 and upward force F1 along the axis to form a high-pressure balance, so that the axial force balance of the driving screw and the driven screw is in a high-low pressure combination type, and the axial force balance action parts are dispersedly arranged, which is beneficial to the dissipation of the energy of the noise source and avoids the influence of the concentrated arrangement of the action parts on the low-noise operation.

[0009] Furthermore, the meshing side clearance between the driving screw and the driven screw adopts a non-strictly sealed structure of the profile side clearance. In the non-strictly sealed structure of the profile side clearance, the semi-central angles of the driving screw and the driven screw are both less than 28.8°.

[0010] Furthermore, the meshing side clearance between the driving screw and the driven screw adopts a non-strictly sealed structure of the chamfer. In the non-strictly sealed structure of the chamfer, the semi-central angles of the driving screw and the driven screw are both 28.8°, and the top circle and the profile transition part of the driving screw are chamfered.

[0011] Furthermore, a deep groove ball bearing is arranged between the driving shaft of the driving screw and the connecting frame and is sealed with a cartridge mechanical seal. An oil return hole for the driving screw is arranged at the upper part of the driving screw. The mechanical seal and the oil return hole for the driving screw form an internal channel oil return structure, so that the oil returned by the mechanical seal passes through the oil return hole for the driving screw and returns to the inlet cavity of the screw bushing.

[0012] Furthermore, the lower part of the driven screw is connected to the bottom of the screw cavity through an axial force thrust seat for the driven screw, and an oil return hole for the driven screw is arranged on the driven screw.

[0013] Furthermore, a safety protection device composed of a safety valve orifice ring, a safety valve core, a safety valve spring, a safety valve seat, a safety valve screw and a safety valve cover is arranged on the pump body.

[0014] The beneficial effects of the present invention are as follows:

[0015] 1. The theoretical pulsation rate is zero, and the actual pulsation is extremely small, which is suitable for the low-noise and low-vibration transportation of various viscosity liquids of lubricating media in the gas-containing state;

[0016] 2. Process adjustment is carried out according to the gas content, and it can adapt to the gas-liquid mixed transportation working conditions in various gas-containing states, and meet the use requirements in harsh environments such as land use, marine use and aviation.

[0017] 3. The overall structure has few components, making disassembly, assembly and maintenance convenient; it operates stably under the gas-containing state, with very small vibration and noise, and some technologies have been practically verified;

[0018] 4. The gas-liquid mixed transportation low-noise three-screw pump is very suitable for use in the ship environment where the cabin volume is small, the space is cramped, and there are high requirements for vibration and noise, external dimensions and weight. Moreover, the production cost is relatively low, which has very important market economic value.

[0019] In summary, the present invention is applicable to the low-noise transportation of lubricating medium liquid in the gas-containing state; it has the advantage of universal design, is applicable to both low-pressure and high-pressure transportation, and can be adjusted according to the gas content to adapt to the corresponding working conditions; it operates stably under the gas-containing state, with very small vibration and noise, and some technologies have been practically verified; the overall structure of the present invention has few components, making disassembly, assembly and maintenance convenient; the present invention is very suitable for use in an environment with cramped space and high requirements for vibration and noise, external dimensions and weight, and has very important market economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a main sectional view schematic diagram of a gas-liquid mixed transportation low-noise three-screw pump of the present invention;

[0021] Figure 2 It is a side partial sectional view schematic diagram of a gas-liquid mixed transportation low-noise three-screw pump of the present invention;

[0022] Figure 3 It is a cross-sectional view schematic diagram of the screw bushing of a three-screw pump;

[0023] Figure 4 It is a schematic diagram of the high-low pressure combination type for axial force balance of a three-screw pump;

[0024] Figure 5 It is a schematic diagram of the inner flow channel of a strictly sealed type three-screw pump;

[0025] Figure 6 It is a schematic diagram of the type surface side clearance non-strictly sealed type of a three-screw pump;

[0026] Figure 7 It is a schematic diagram of the chamfered non-strictly sealed type of a three-screw pump;

[0027] Figure 8 It is a schematic diagram of the mechanical seal oil return channel of a three-screw pump;

[0028] Figure 9 It is an implementation diagram of a double type surface side clearance non-strictly sealed type screw;

[0029] Figure 10 It is a schematic diagram of a single type surface side clearance non-strictly sealed type;

[0030] Figure 11 Implementation diagram of double chamfer non-strict sealing type screw (active screw top circle linear chamfer);

[0031] Figure 12 Implementation diagram of single chamfer non-strict sealing type screw (active screw top circle linear chamfer). Specific implementation manner

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] The three-screw pump of the present invention is based on the cycloidal tooth profile meshing principle, forming a strictly sealed spiral flow channel, and is widely used. The present invention is a gas-liquid mixed transportation low-noise three-screw pump, adopting a vertical single-suction structure, with the pump inlet located below and the pump outlet located on the side.

[0034] As Figure 1 , shown in FIG. 2, a gas-liquid mixed transportation low-noise three-screw pump of the present invention includes a motor 1, a coupling frame 2, an elastic pin coupling 3, a cartridge mechanical seal 4, a deep groove ball bearing 5, a pump body 6, a screw bushing 7, an active screw axial force balance drum 8, an active screw oil return hole 9, an active screw 10, a driven screw one 11, a driven screw oil return hole one 12, a driven screw axial force thrust seat one 13, a pump body inlet cavity 14, a pump body inlet cavity oil cup 15, a driven screw axial force thrust seat two 16, a driven screw oil return hole two 17, a driven screw two 18, a pump body outlet cavity 19, a pump body inlet cavity oil injection screw 20, a safety valve orifice ring 21, a safety valve core 22, a safety valve spring 23, a safety valve seat 24, a safety valve screw 25, and a safety valve cover 26.

[0035] The upper end of the pump body 6 is fixedly connected to the motor 1 through the coupling frame 2. The output shaft of the motor 1 is connected to the drive shaft of the active screw 10 through the elastic pin coupling 3. A deep groove ball bearing 5 is arranged between the drive shaft of the active screw 10 and the coupling frame 2 and is sealed with a cartridge mechanical seal 4. The lower end face of the coupling frame 2 is fixedly connected to the screw bushing 7. An active screw axial force balance drum 8 is arranged between the upper part of the screw bushing 7 and the drive shaft of the active screw 10. The screw part of the active screw 10 is located inside the screw bushing 7 and is connected in cooperation with the driven screw one 11 and the driven screw two 18. The driven screw one 11 and the driven screw two 18 are respectively provided with a driven screw axial force thrust seat one 13 and a driven screw axial force thrust seat two 16 below. The upper part of the active screw 10 is provided with an active screw oil return hole 9. The driven screw one 11 and the driven screw two 18 are respectively provided with a driven screw oil return hole one 12 and a driven screw oil return hole two 17. The upper part of the pump body 6 is provided with a pump body outlet cavity 19, and the lower part is provided with a pump body inlet cavity 14. The pump body 6 is provided with a safety protection device composed of a safety valve orifice ring 21, a safety valve core 22, a safety valve spring 23, a safety valve seat 24, a safety valve screw 25, and a safety valve cover 26.

[0036] like Figure 3 As shown, the contour line of the cross section of the screw bushing 7 of the present invention is surrounded by two clam lines 27 and 28 with different constants, and the contour line surrounded by the clam lines is smoothly transitioned with a large arc. The clam line is called the Nicomedes clam line in the mathematical category, and the clam line formula is expressed in polar coordinates: ρ = a × sec (θ) + b, where a and b are constants. The screw bushing using the clam line as the contour line has a smooth and flowing streamlined body shape. During the flow of the conveying medium, the clam line streamline body can reduce the vortex effect or avoid the formation of vortex, thereby greatly reducing the fluid resistance and making the overall flow field in a uniform low-speed state. According to Bernoulli's principle, fluid velocity is related to pressure. In the low-speed state of the flow field, a low negative pressure will not occur, which can reduce the precipitation of soluble gas in the medium and avoid deteriorating the gas-liquid mixed transmission environment. At the same time, the low-speed state is conducive to low-noise operation.

[0037] like Figure 4 As shown, affected by the pressure difference between the inlet and outlet chambers, the active screw is subjected to a force F3 (53) downward along the axis and a force F4 (54) upward along the axis, and the driven screw is subjected to a force F5 (55) downward along the axis and F1 (51) upward along the axis, thereby achieving axial force balance. However, from the perspective of the force-bearing parts, the active screw is in a tensile state under the action of F3 and F4, and the driven screw is in an extrusion state under the action of F5 and F1. Usually, in the definition of axial force balance of a three-screw pump, the tensile state is called low-pressure balance, and the extrusion state is called high-pressure balance. In conventional design, the active screw and the driven screw are either low-pressure balanced or high-pressure balanced, and the axial force balance action parts are concentrated on the same side, which is beneficial to design processing or cost control. In the present invention, the active screw adopts low-pressure balance, the driven screw adopts high-pressure balance, the axial force balance is a high-low pressure combination type, and the axial force balance action parts are dispersedly arranged, which is beneficial to the dissipation of noise source energy and avoids the concentrated arrangement of the action parts affecting low-noise operation.

[0038] like Figure 5As shown, the semi-central angle of the driving screw one is 74, the semi-central angle of the driving screw two is 75, the semi-central angle of the driven screw one of the driven screw is 71, and the semi-central angle of the driven screw two of the driven screw is 73, all of which are 28.8° (0.16π). This is the basic characteristic of the strictly sealed screw parameters. The driven screw rotates automatically under the action of the inlet and outlet pressure difference. There is only relative rotational motion between the driving screw and the driven screw, without torque transmission. Therefore, the wear of the screw profile is extremely small, and the running noise of the three-screw pump is generally low. However, when the transported medium contains a certain amount of insoluble gas, the gas inhaled into the inlet chamber enters the outlet chamber along with the spiral flow path formed by the screws. At the moment when the outlet chamber is opened, the gas in the spiral seal chamber is rapidly compressed or extinguished under the action of the high pressure in the outlet chamber. The result of the compression and extinction of numerous bubbles has a great impact on the smooth transportation of the medium and the pressure pulsation. The lubricating oil pump produces a lot of noise and vibration, and a very loud "crackling" sound can be heard by the ear, seriously affecting the vibration and noise performance of the three-screw pump. This shows that the strictly sealed screw design structure of the three-screw pump can no longer maintain low noise and low vibration operation under this gas-liquid mixed transportation condition.

[0039] In the overall structural design of the present invention, a good foundation is laid for low-noise gas-liquid mixed transportation. The main innovation points are as follows: ① A square pump body 6 with a wide large arc chamfer is adopted. The large cavity design is beneficial to keeping the flow field speed at a relatively low state; ② The screw bushing 7 adopts a conchoidal contour streamline body shape, reducing vortexes and avoiding violent collisions and impacts, and keeping the overall flow path in the pump at a relatively low speed everywhere; ③ A relatively low rotational speed is adopted in the design, so that the rotational linear speeds of the driving screw 10, the driven screw one and two 11, 18 are kept at a relatively low state; ④ The axial length of the screw bushing 7 is greater than the spiral meshing part formed by the driving screw 10, the driven screw one and two 11, 18. Or rather, the screw bushing 7 wraps the spiral meshing part therein, resulting in the appearance of the inlet cavity 61 of the screw bushing and the outlet cavity 62 of the screw bushing. The appearance of these two cavities can be regarded as a buffer zone for the medium to enter and exit the spiral meshing part, reducing the interference of the spiral flow path on the pump body inlet chamber 14 and the pump body outlet chamber 19 to a certain extent, which is beneficial to low-noise operation.

[0040] By adopting the above measures, a good environment for low-noise operation under gas-liquid mixed transportation conditions can be created. However, the treatment method of the gas in the spiral seal cavity is the key design part considered in the present invention. One of the design methods of the present invention is the non-strict sealing structure of the flank clearance: that is, adjusting the angular values of the first half central angle 74 and the second half central angle 75 of the driving screw to be less than 28.8° required for the strict sealing type. The reduction of the half central angle significantly increases the flank clearance between the driving screw and the driven screw, breaking through the strict sealing structure, so that the high-pressure oil in the outlet cavity is introduced into the screw seal cavity along the flank clearance of the driving screw to pre-compress the gas in the screw seal cavity. When the gas in the screw seal cavity opens to the outlet cavity, there will be no instantaneous explosion, thus achieving the purpose of low noise and low vibration. Another design method of the present invention is the non-strict sealing structure of the chamfer: keeping the first half central angle 74, the second half central angle 75 of the driving screw and the first and second half central angles 71, 73 of the driven screw all at 28.8° (0.16π), chamfering the transition part between the top circle and the flank of the driving screw, resulting in the first flank chamfer 76 and the second flank chamfer 77 of the driving screw. The appearance of the chamfer also creates a spiral return channel, breaking through the strict sealing structure, and has the same effect as the non-strict sealing structure of the flank clearance. It should be noted here that the chamfer form of the driving screw is not limited to the straight chamfer shown in the figure, but also includes arc chamfers, cycloid chamfers, involute chamfers or other chamfers that can break through the strict sealing, and the chamfer direction and size are adjusted according to the design requirements.

[0041] As Figure 6 shown in the non-strict sealing structure of the flank clearance, the first and second half central angles 71, 73 of the driven screw are 28.8° (0.16π), but when the first half central angle 74 and the second half central angle 75 of the driving screw are 17°, it can be clearly seen that the adjacent seal cavities of the spiral channel are connected, and the screw seal has become a non-strict sealing type. Figure 5 The 17° here is for illustrative purposes and does not mean that 17° is adopted in the present invention. Instead, it is adjusted accordingly according to different requirements of gas-liquid mixed transportation, and the adjustment range is 0 to 28.8°. This design has three advantages: ① The oil guiding channel is naturally formed along the screw flank, smooth without sharp edges; ② The driven screw has lower rigidity and greater processing difficulty than the driving screw. Keeping the included angle of the top circle of the driven screw unchanged, its automatic rotation effect is not affected, and it has good general performance; ③ By adjusting the first half central angle 74 and the second half central angle 75 of the driving screw, with the adjustment range from 0 to 28.8°, different amounts of oil guiding can be achieved to adapt to gas-liquid mixed transportation under different gas contents.

[0042] As Figure 7The shown chamfered non-strict sealing structure keeps the half central angle of the driving screw one - 74, the half central angle of the driving screw two - 75, and the half central angles of the driven screw one and two - 71, 73 all at 28.8° (0.16π). Chamfers are made on the top circle of the driving screw, resulting in the chamfer one 76 and the chamfer two 77 of the driving screw profile. It can be clearly seen that the adjacent sealing cavities of the spiral channel are connected, and the screw seal has become a non-strict sealing type. Figure 6 The straight chamfer in it is for illustrative purposes and does not mean that the present invention only adopts straight chamfers. Instead, some chamfer forms that can break through strict sealing are adopted. This design has three advantages: ① The processing difficulty of the oil guiding channel is relatively small, and there are various types of chamfers, making it convenient to form a spiral oil return channel; ② The driven screw has less rigidity and greater processing difficulty than the driving screw. Keeping the included angle of the top circle of the driven screw unchanged, its automatic rotation effect is not affected, and it has good general performance; ③ By adjusting the chamfer values of the chamfer one 76 and the chamfer two 77 of the driving screw profile, different amounts of oil guiding can be achieved to adapt to gas-liquid mixed transportation under different gas contents.

[0043] As Figure 8 Shown, the mechanical seal oil return passes through the oil return hole 9 of the driving screw for oil return, which belongs to the internal channel oil return mode, different from the traditional external pipeline oil return to the pump inlet mode. This is also one of the innovation points of the present invention. This design has three advantages: ① By internally returning oil through the oil return hole 9 of the driving screw, the external oil return pipeline is cancelled, making the appearance of the pump set simple, avoiding pollution caused by pipeline breakage or leakage, avoiding noise at the pump inlet due to pipeline air leakage, and being conducive to the quick repair and disassembly and reinstallation of the pump set; ② The mechanical seal oil return is at positive pressure. Through the oil return hole 9 of the driving screw, it reaches the inlet cavity 61 of the screw bushing, which is conducive to suppressing the precipitation of gas in the medium in a negative pressure environment to a certain extent, is conducive to anti-cavitation performance, and is also conducive to low-noise operation.

[0044] There are the following several embodiments of the non-sealing structure of the screw in the gas-liquid mixed transportation low-noise three-screw pump:

[0045] Embodiment 1: Figure 9 In the implementation drawing (the half central angle of the driving screw 1 = 17°, the half central angle of the driving screw 2 = 17° are for illustrative purposes), the half central angle of the driving screw 1 = 17°, the half central angle of the driving screw 2 = 17°. It should be noted here that 17° is for illustrative purposes. The implementation scheme is that the half central angle of the driving screw one and the half central angle of the driving screw two are both less than 28.8°, and the half central angle of the driving screw one is not necessarily equal to the half central angle of the driving screw two. This scheme can achieve different profile side clearance return channels, facilitating gas-liquid mixed transportation.

[0046] Embodiment 2: Figure 10In the implementation scheme diagram, the semi-central angle 1 of the driving screw is 28.8°, and the semi-central angle 2 of the driving screw is 17°. It should be noted here that 17° is for illustrative purposes. The implementation scheme is that the semi-central angle two of the driving screw is less than 28.8°. This scheme can achieve a flank side clearance return channel with a high volumetric efficiency and is convenient to adjust.

[0047] Example 3: Figure 11 In the implementation scheme diagram (the straight chamfer at the top circle of the driving screw is for illustrative purposes), keep the semi-central angle 1 of the driving screw at 74, the semi-central angle 2 of the driving screw at 75, and the semi-central angle 1 and 2 of the driven screw at 71 and 73 all at 28.8° (0.16π). Chamfer the top circle of the driving screw twice, resulting in the driving screw flank chamfer 1 at 76 and the driving screw flank chamfer 2 at 77. Two spiral return channels appear along the top circle of the driving screw, breaking through the strict sealing structure. The chamfering form and size of the driving screw flank chamfer 1 at 76 and the driving screw flank chamfer 2 at 77 can be different. This scheme can achieve two chamfered spiral return channels, facilitating gas-liquid mixed transportation.

[0048] Example 4: Figure 12 In the implementation scheme diagram (the straight chamfer at the top circle of the driving screw is for illustrative purposes), keep the semi-central angle 1 of the driving screw at 74, the semi-central angle 2 of the driving screw at 75, and the semi-central angle 1 and 2 of the driven screw at 71 and 73 all at 28.8° (0.16π). Chamfer the top circle of the driving screw once, resulting in the driving screw flank chamfer 1 at 76. One spiral return channel appears along the top circle of the driving screw, breaking through the strict sealing structure. The chamfering form and size of the driving screw flank chamfer 1 at 76 can be different. This scheme can achieve one chamfered spiral return channel, which not only maintains a high volumetric efficiency but also is convenient for processing.

Claims

1. A gas-liquid mixed transportation low-noise three-screw pump, which has a pump body, a driving screw and two driven screws, is characterized in that: The upper part of the pump body is fixedly connected to the motor through a connecting frame. The output shaft of the motor is fixedly connected to the drive shaft of the active screw. The lower end face of the connecting frame is fixedly connected to a screw bushing. An active screw axial force balance drum is arranged between the upper part of the screw bushing and the drive shaft of the active screw. The screw part of the active screw is located inside the screw bushing and is meshed and connected with two driven screws. The upper part of the pump body is provided with a pump body outlet cavity, and the lower part is provided with a pump body inlet cavity. The screw bushing adopts the shape of a conchoidal contour streamline body, which can reduce vortexes and avoid violent collisions and impacts. The axial length of the screw bushing is greater than the spiral meshing part of the active screw and the two driven screws, and forms an inlet cavity of the screw bushing and an outlet cavity of the screw bushing, making the inlet and outlet of the spiral meshing part a buffer zone, which can reduce the interference of the spiral flow channel on the pump body inlet cavity and the pump body outlet cavity and is conducive to low-noise operation. The pump body is a square pump body with a wide large arc chamfer, and the internal large cavity is conducive to keeping the flow field in a low-speed state. The conchoidal contour streamline body shape of the screw bushing is surrounded by two conchoids with different constant quantities, and the contour line surrounded by the conchoids is smoothly transitioned with a large arc.

2. The gas-liquid mixed transportation low-noise three-screw pump according to claim 1, characterized in that: The motor adopts a low-speed motor, so that the rotational linear speeds of the active screw and the two driven screws are kept in a low rotational speed state.

3. The gas-liquid mixed transportation low-noise three-screw pump according to claim 1, characterized in that: The downward force F3 along the axis and the upward force F4 along the axis on the active screw and the downward force F5 along the axis and the upward force F1 along the axis on the driven screw achieve axial force balance. Under the action of the downward force F3 along the axis and the upward force F4 along the axis, the active screw is in a tensile state to form a low-pressure balance. Under the action of the downward force F5 along the axis and the upward force F1 along the axis, the driven screw is in a compressive state to form a high-pressure balance. Thus, the axial force balance of the active screw and the driven screw is in a high-low pressure combination type, and the axial force balance action parts are dispersedly arranged, which is conducive to the dissipation of the energy of the noise source and avoids the influence of the concentrated arrangement of the action parts on the low-noise operation.

4. The gas-liquid mixed transportation low-noise three-screw pump according to claim 1, wherein: The meshing side clearance between the active screw and the driven screw adopts a non-strictly sealed type surface side clearance structure. In the non-strictly sealed type surface side clearance structure, the semi-central angles of both the active screw and the driven screw are less than 28.8°.

5. The gas-liquid mixed transportation low-noise three-screw pump according to claim 1, wherein: The meshing side clearance between the active screw and the driven screw adopts a non-strictly sealed type chamfer structure. In the non-strictly sealed type chamfer structure, the semi-central angles of both the active screw and the driven screw are 28.8°, and the top circle of the active screw and the transition part of the surface are chamfered.

6. The gas-liquid mixed transportation low-noise three-screw pump according to claim 1, wherein: A deep groove ball bearing is arranged between the drive shaft of the active screw and the connecting frame and is sealed with a cartridge mechanical seal. An active screw oil return hole is arranged on the upper part of the active screw. The mechanical seal and the active screw oil return hole form an internal channel oil return structure, so that the oil returned by the mechanical seal reaches the inlet cavity of the screw bushing through the active screw oil return hole.

7. The gas-liquid mixed transportation low-noise three-screw pump according to claim 1, wherein: The lower part of the driven screw is connected to the bottom of the screw cavity through a driven screw axial force thrust seat, and a driven screw oil return hole is arranged on the driven screw.

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