Non-sealed four-screw pump with two-stage oil-blocking exhaust

Abstract

This invention discloses a non-sealed four-screw pump with two-stage oil-blocking and venting. The driving screw is centrally mounted, and three driven screws are evenly arranged circumferentially around the driving screw. The sealing cavity between the driving and driven screws is a non-sealed cavity. The screw bushing body, the middle section of the screw bushing, and the upper section of the screw bushing are fitted onto the outside of the driving and driven screws. The middle section of the screw bushing is made of breathable steel. The screw bushing body and the middle section of the screw bushing form an annular pore, and the pore of the breathable steel connects the working cavity of the screw to the annular pore. The annular pore connects upwards to the vent valve, which has a Tesla valve flow channel structure. A float is installed at the top of the vent valve, and there is a certain gap between the float and the upper cavity of the vent valve. This invention solves the problem of high vibration and noise in existing screw pumps under gas-liquid mixed transport conditions, improving the operational stability under these conditions. This invention has a simple structure, few parts, and is suitable for low-noise, low-vibration transport under gas-liquid mixed transport conditions.

Description

Technical Field

[0001] This invention belongs to the technical field of screw pumps for conveying a certain lubricating medium. The lubricating medium includes, but is not limited to, fuel, lubricating oil and hydraulic oil. The medium is a clean medium and a certain amount of gas is allowed. Specifically, it is a non-sealed four-screw pump with two-stage oil blocking and venting that has a comparative advantage in conveying gas-liquid mixtures and has low noise requirements. Background Technology

[0002] The non-sealed four-screw pump mainly includes a pump body, a screw bushing assembly, one driving screw, three driven screws, and an exhaust accessory. The driving screw is centrally located, and the three driven screws are evenly arranged around the outside of the driving screw. Both the driving and driven screws adopt conventional profiles. Because the number of screw heads and screws is selected in this way, it does not conform to a strictly sealed cavity relationship; therefore, the sealing cavity between the screw pairs is a non-sealed cavity. Although the volume loss of the non-sealed cavity is relatively large, the cavity backflow can reduce the pressure difference between cavity stages, which is suitable for the mixed transportation of gas-liquid two-phase media at low pressures, and its vibration and noise can be controlled within a low range.

[0003] When the four-screw pump rotates, the instantaneous cross-sectional area of ​​the screw pair is the same, and its flow pulsation rate and pressure pulsation rate are very small, resulting in smooth delivery.

[0004] In industrial applications, four-screw pumps can be used for low-pressure, high-flow-rate lubricating oil transportation in the marine industry. To save valuable tank space, the marine industry uses high circulation rates in its lubricating oil transportation systems, resulting in a large amount of gas mixed in the lubricating oil. The lubricating oil is viscous, making it difficult for gas to quickly escape. Traditional three-screw pumps have sealed toothed screws, which can achieve low-noise transportation when there is little or no gas in the oil. However, when a large amount of gas bubbles increase, the sealed toothed screw cavity cannot handle the mixed gas-liquid transportation conditions. When the sealed cavity opens towards the outlet, the pressure suddenly increases, leading to a sharp increase in pressure and flow pulsations within the pump. This not only fails to achieve low noise but also damages reliable operation, representing a typical harsh transportation condition.

[0005] Existing patent document (CN1743676A) discloses a screw tooth profile for a high-flow, high-pressure three-screw pump. This patent uses a novel conjugate tooth profile with unequal tooth counts, and the screws are fully meshed and sealed. It is designed for high-pressure single-phase delivery and cannot be used for gas-liquid mixed-transmission conditions. The existing technology lacks a four-screw mixed-transmission pump solution that can actively release gas inside the pump chamber while simultaneously achieving two-stage oil resistance, thus both venting gas and suppressing oil leakage.

[0006] Existing patent document (CN217233779U) discloses a three-screw pump suitable for multi-bubble media. While this patent, through the ingenious design of "adding a long groove at the inlet end," alleviates the noise problem caused by bubble collapse to some extent, it still has significant limitations from the perspectives of fluid mechanics, pump and valve sealing mechanisms, and long-term operation under complex conditions. Furthermore, it fails to address the core pain points in gas-liquid mixed transport conditions. The core logic of this patent is to "directly transport the bubbles without them bursting." However, from a thermodynamic and fluid mechanics perspective, when bubbles are transported to the high-pressure zone at the discharge end, they will inevitably be subjected to severe compression. Under the high pressure at the discharge end, bubbles are prone to micro-collapse, still generating localized high temperatures, high-frequency vibrations, and noise, and damaging the lubricating oil film on the screw surface, leading to tooth wear. The gas is merely "transferred" rather than "eliminated." High-pressure oil carrying a large number of bubbles entering the downstream hydraulic or lubrication system can cause cavitation, sluggish operation, or control failure in downstream equipment. This solution lacks a mechanism to actively extract gas from the oil and discharge it outside the pump. This patent uses a traditional "one master, two slave" three-screw structure. This structure has a very tight meshing, but the enclosed volume within the pump chamber is small, lacking sufficient gas buffering and accumulation space. When processing media with high gas content, the gas-liquid mixture is difficult to effectively stratify within the pump chamber, leading to uneven screw stress and exacerbating operational vibration.

[0007] Therefore, in order to solve such harsh gas-liquid mixed transportation conditions, it is urgent to propose a non-sealed four-screw pump with two-stage oil blocking and venting. Summary of the Invention

[0008] The purpose of this invention is to provide a non-sealed four-screw pump with two-stage oil-blocking and venting capabilities, solving the problem of high vibration and noise in existing screw pumps under gas-liquid mixed transport conditions, and improving the operational stability of gas-liquid mixed transport. The four-screw pump of this invention has a simple structure, fewer parts, and is suitable for low-noise, low-vibration transport in gas-liquid mixed transport conditions.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A non-sealed four-screw pump with two-stage oil-blocking and venting includes a pump body, a screw bushing body, a middle section of the screw bushing, an upper section of the screw bushing, a driving screw, three driven screws, an vent valve, and a float. The driving screw is centrally mounted, and the three driven screws are evenly arranged around the outer periphery of the driving screw. The sealing cavity between the driving and driven screws is a non-sealed cavity for transporting gas-liquid two-phase media. The screw bushing body, the middle section of the screw bushing, and the upper section of the screw bushing are fitted around the driving and driven screws. The middle section of the screw bushing is made of breathable steel. Material: The screw bushing body and the middle section of the screw bushing form an annular pore (KQ). The pores of the ventilated steel in the middle section of the screw bushing connect the screw working chamber with the annular pore (KQ). Gas entrained in the medium can pass through the ventilated steel and enter the annular pore (KQ). The annular pore (KQ) is connected upward to the exhaust valve. The exhaust valve is equipped with a Tesla valve flow channel structure, which allows gas to flow upward and generates flow resistance on the oil that escapes with the gas, inhibiting the upward movement of the oil. A float is provided at the top of the exhaust valve, and there is a certain gap between the float and the upper part of the cavity of the exhaust valve.

[0011] Furthermore, the driving screw adopts a cycloidal profile with double-headed convex teeth; the driven screw adopts a cycloidal profile with double-headed concave teeth.

[0012] Furthermore, the lead number of the driving screw and the driven screw is not less than 1.5 times.

[0013] Furthermore, the screw bushing body and the upper section of the screw bushing are made of dense, non-permeable metal, and the middle section of the screw bushing corresponds to the annular pore (KQ).

[0014] Furthermore, the exhaust valve is arranged vertically, and the Tesla valve flow channel in the Tesla valve flow channel structure is provided with multiple sets of reverse blocking teeth inside the valve cavity, so that the upward flow resistance of gas is small, the upward flow resistance of oil is large, and the downward return resistance is small. The oil accompanying the airflow returns to the jacket cavity by its own weight.

[0015] Furthermore, when there is no large amount of liquid in the accompanying gas flow, the gas overflowing from the exhaust valve bypasses the float and enters the cone orifice and channel to be discharged outside the pump. When the amount of oil in the accompanying gas increases significantly, the float, affected by buoyancy, rises and blocks the cone orifice, achieving automatic closure; when the oil volume decreases, the float falls back, and the exhaust channel reopens.

[0016] Furthermore, the float has a hollow structure, which facilitates its floating in liquid.

[0017] Furthermore, the float is made of rubber, nylon, or coated with an elastic material, which helps to effectively seal the conical orifice opening after liquid overflows.

[0018] Furthermore, a sealing ring is provided between the exhaust valve and the pump cover to prevent leakage of pressurized oil from the outlet.

[0019] Furthermore, the pump utilizes a Tesla valve to allow gas to flow upwards by leveraging the unidirectional resistance characteristic of the fluid, thus blocking the oil that escapes with the gas. The upper end of the exhaust channel is connected to a float venting structure. When the amount of oil entering the channel increases and lifts the pump, the float can close the exhaust channel. When the amount of oil decreases, the float falls back and reopens the exhaust channel, achieving a two-stage oil blocking and exhaust system of "exhausting when there is more gas and self-sealing when there is more oil." This solves the problem of high vibration and noise in the gas-liquid mixed transport conditions of screw pumps and improves the operational stability of gas-liquid mixed transport conditions.

[0020] Compared with the prior art, the present invention has the following significant advantages: 1. This invention adopts a non-sealed four-screw gas-liquid mixed transport pump structure. The screw pair does not form a high-pressure sealed cavity, which greatly improves the throughput capacity of gas and liquid two-phase media and is suitable for gas-liquid mixed transport conditions.

[0021] 2. The middle section of the screw bushing is made of breathable steel. The gas carried by the medium inside the pump chamber can pass through the breathable steel and enter the annular pore KQ, realizing in-situ degassing inside the pump, reducing gas accumulation inside the pump chamber, and reducing vibration and flow pulsation.

[0022] 3. The exhaust channel is equipped with a two-stage oil-blocking and exhaust structure: The first stage is an exhaust valve with a Tesla valve flow channel inside, which allows gas to pass upward and creates resistance to the oil that is leaking out. Most of the oil flows back by its own weight. The second stage is a float venting design. When a large amount of oil leaks in, the float rises and blocks the cone orifice. When the oil level drops, the exhaust automatically opens, realizing "exhausting when there is too much gas and self-sealing when there is too much oil", which effectively inhibits oil leakage.

[0023] 4. The blocked oil can flow back into the pump chamber, reducing media loss. The overall structure is integrated inside the pump body, eliminating the need for additional complex external degassing equipment. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of the non-sealed four-screw pump with two-stage oil blocking and venting of the present invention (the four-screw pump is a vertical pump structure, and the hollow arrow indicates the direction of liquid flow inside the pump). Figure 2 This is a horizontal schematic diagram of the four-screw pump of the present invention (the hollow arrow indicates the direction of liquid flow inside the pump). Figure 3 This is a schematic diagram of the screw engagement of the four-screw pump of the present invention; Figure 4 This is a schematic diagram of the exhaust channel of the four-screw pump of the present invention; In the diagram, 1-driving screw; 1a-radial center hole; 1b-axial center hole; 2-mechanical seal; 3-pump cover; 3a-conical bore; 3b-channel; 3c-lower part; 4-driven screw; 5-upper section of screw bushing; 6-middle section of screw bushing; 7-screw bushing body; 7a-chamfered hole; 8-pump body; 9-exhaust valve; 9a-Tesla valve channel; 10-float; 11-rolling bearing; 12-shaft retaining ring; KQ-annular orifice. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0026] This invention proposes a non-sealed four-screw pump with two-stage oil-blocking and venting. While retaining the toothed structure of a conventional three-screw pump (one main screw and three driven screws evenly distributed circumferentially), it transforms the strict seal of the three-screw pump into a non-strict seal. During operation, the gas-liquid mixture in each screw's sealing chamber is gradually compressed and connects with the outlet pressure when the chamber opens, preventing sudden pressure changes and thus reducing the magnitude and amplitude of vibration and noise during high-gas-content operation. The pressure rise within each screw's sealing chamber becomes continuous and stable. The frequency of sudden bubble collapse is greatly reduced, making the three-screw pump operate more quietly.

[0027] The four-screw pump of this invention is a non-sealed design. Since noise and vibration are caused by the enlargement of air bubbles in the inlet pipe and inlet cavity, followed by their rapid collapse when the fluid pressure rises, suppressing bubble generation can solve the problem of increased vibration and noise. Therefore, a driven screw is added to the original structure of the three-screw pump, resulting in a structure with one driving screw and three driven screws. The driving and driven screws remain unchanged. According to the Mendelssohn equation, the screw sealing cavity becomes non-fully sealed, with an internal leakage channel running through each screw sealing cavity, connecting the inlet and outlet cavities. However, this channel is long and winding, allowing the gas-liquid mixture in each screw sealing cavity to be gradually compressed and connected to the outlet pressure when opening towards the outlet cavity, preventing sudden pressure changes and thus reducing the magnitude and amplitude of vibration and noise during high gas content operation. In this way, the pressure rise in each screw sealing cavity becomes continuous and stable. The number of sudden bubble collapses is greatly reduced, making the three-screw pump operate more quietly.

[0028] The screw bushing of this four-screw pump uses permeable steel in the middle section, allowing gas trapped inside the medium to pass through the permeable steel and enter the annular pores. These pores are connected to an exhaust valve, allowing the gas to be discharged from the pump body through the exhaust port on the pump cover. The exhaust valve contains a Tesla valve flow channel, utilizing its unidirectional resistance characteristic to allow gas to flow upwards, thus blocking the oil that escapes with the gas. The upper end of the exhaust channel connects to a float venting structure. When the amount of oil entering the channel increases and lifts the pump, the float closes the exhaust channel. When the oil volume decreases, the float falls back and reopens the exhaust channel, achieving a two-stage oil-blocking and venting mechanism: "exhaust when there is too much gas, self-sealing when there is too much oil." This solves the problem of high vibration and noise in existing screw pumps operating under gas-liquid mixed transport conditions, improving the operational stability of gas-liquid mixed transport.

[0029] Example: like Figures 1 to 4 As shown, the present invention provides a non-sealed four-screw gas-liquid mixing pump with two-stage oil blocking and venting, including a pump body 1, a screw bushing body 7, a middle section of the screw bushing 6, an upper section of the screw bushing 5, a driving screw 1, three driven screws 4, and parts such as an venting valve 9 and a float 10; Figure 3 In this four-screw pump, one driving screw 1 and three driven screws 4 form the screw meshing. Axially, the driving and driven screws use a slotted fixing structure, creating a low-pressure balance structure. The driving screw 1 has a radial center hole 1a and an axial center hole 1b inside, allowing the oil from the friction pair between the rotating and stationary rings of the mechanical seal 2 to flow back to the pump inlet. This simple structure avoids the need for external piping.

[0030] The driving screw is centrally mounted, and three driven screws are evenly arranged around the outer periphery of the driving screw. The sealing cavity between the driving and driven screws is a non-sealed cavity used for the mixed transport of gas and liquid media. The screw bushing body 7, the middle section of the screw bushing 6, and the upper section of the screw bushing 5 are fitted outside the driving screw 1 and the driven screw 4. Only the middle section of the screw bushing 6 is made of breathable steel. The screw bushing body 7 and the middle section of the screw bushing 6 form an annular pore KQ (see...). Figure 2 (The hollow arrow indicates the direction of liquid flow in the pump). The pores of the permeable steel connect the working chamber of the screw and the annular pore KQ. Gas entrained in the medium can pass through the permeable steel and enter the annular pore KQ. The annular pore KQ is connected upward to the exhaust valve 9. The exhaust valve 9 is equipped with a Tesla valve flow channel structure, which allows gas to flow upward and generates flow resistance on the oil that escapes with gas, thus inhibiting the upward movement of the oil.

[0031] A float 10 is installed at the top of the exhaust valve 9, and there is a certain gap between the float 10 and the upper cavity of the exhaust valve 9. Therefore, when there is no large amount of liquid in the accompanying gas flow, the gas overflowing from the exhaust valve 9 bypasses the float 10 and enters the conical orifice 3a and channel 3b to be discharged outside the pump. When the amount of oil in the accompanying gas increases significantly, the float 10 is affected by buoyancy and rises to block the conical orifice 3a, achieving automatic closure; when the oil decreases, the float 10 falls back, and the exhaust channel reopens.

[0032] The driving screw 1 and driven screw 4 adopt the screw tooth profile of a conventional three-screw pump, i.e., the driving screw adopts a cycloidal profile with double-headed convex teeth; the driven screw also adopts a cycloidal profile with double-headed concave teeth; there is one driving screw and three driven screws. According to the relevant Montgomery formula, one driving screw and three driven screws cannot form a strictly sealed cavity, therefore the sealing cavity between the screw pairs is a non-sealed cavity. Although the volumetric loss of the non-sealed cavity is relatively large, the cavity backflow can reduce the pressure difference between cavity stages, which is suitable for the mixed transportation of gas-liquid two-phase media at low pressure, and its vibration and noise can be controlled within a low range. To ensure that the volumetric efficiency of the pump is within an acceptable range, the screw lead is not less than 1.5 times, as shown in Table 1.

[0033] Table 1. Comparison of geometric parameters between the four-screw pump and the three-screw pump of this invention.

[0034] The exhaust valve 9 is vertically arranged. Multiple sets of reverse-flow blocking teeth are installed inside the valve chamber of the Tesla valve flow channel 9a. This results in low resistance to upward gas flow, high resistance to upward oil flow, and low resistance to downward backflow. The oil accompanying the airflow can return to the annular pore KQ of the jacket by its own weight. A hollow arrow below the exhaust valve 9 indicates the gas flow direction. The exhaust valve has a Tesla valve structure inside, with the Tesla valve channel 9a. The flow direction of the exhaust valve 9 is the direction of high resistance for the Tesla valve. This direction has high resistance to liquid flow; even if liquid leaks in, it has little impact on gas escape. Therefore, the exhaust valve 9 minimizes liquid leakage while allowing gas to pass through. The gas is discharged from the pump through the conical orifice 3a and channel 3b.

[0035] The top cavity of the exhaust valve 9 is equipped with a float 10. When there is no large amount of liquid in the accompanying airflow, the gas overflowing from the exhaust valve 9 bypasses the float 10 and enters the conical orifice 3a and channel 3b to be discharged outside the pump. When the amount of oil in the accompanying gas increases significantly, the float 10 is affected by buoyancy and rises to block the conical orifice 3a, achieving automatic closure; when the oil decreases, the float 10 falls back, and the exhaust channel reopens.

[0036] The float 10 has a hollow structure, which facilitates its floating in liquid. The float 10 is made of rubber, nylon, or has a surface coated with an elastic material, which allows it to effectively seal the conical orifice 3a after liquid overflows. The sealing ring 13 is located between the exhaust valve 9 and the pump cover 3 to prevent leakage of pressurized oil from the outlet chamber.

[0037] The lower part 3c of the pump cover 3 is fitted with the screw bushing body 7 with a clearance stop to facilitate assembly and positioning.

[0038] The screw bushing body 7 and the upper section 5 of the screw bushing are made of dense, non-permeable metal, while the middle section 6 of the screw bushing is made of permeable steel. The middle section 6 of the screw bushing corresponds to the annular pore KQ.

[0039] Among the components of the four-screw pump, only the middle section 6 of the screw bushing is made of permeable steel, which is a powder metallurgy sintered porous stainless steel produced using a high-temperature sintering method. Although the permeable steel used for the middle section 6 of the screw bushing is manufactured using powder metallurgy and its rigidity is significantly lower than that of conventional cast or forged steel parts, its rigidity is sufficient to meet the requirements for the screw bushing, which primarily bears the sealing function. The middle section 6 of the screw bushing, made of permeable steel, forms a three-dimensional interconnected network of micropores, allowing gas to permeate and partial leakage of liquid under a certain pressure difference. Air bubbles within the screw sealing cavity, under the positive pressure of the screw sealing cavity, enter the annular pores KQ through the permeable steel.

[0040] The gas that has penetrated the screw bushing body 7 enters the annular pore KQ formed by the screw bushing body 7 and the middle section 6 of the screw bushing, and then enters the exhaust valve 9 through the chamfered hole 7a.

[0041] The commonly used specifications for the venting steel pores in the middle section 6 of the screw bushing are 7 micrometers, 25 micrometers, and 35 micrometers. 7 micrometers minimizes liquid leakage and is suitable for degassing ordinary oils. Due to the sealing, volumetric efficiency, and practical requirements of four-screw pumps, the actual delivery pressure is very low. Therefore, the pore size can be adjusted according to actual usage requirements to adapt to the delivery pressure and medium viscosity needs, ensuring that the middle section 6 of the screw bushing is only vented and not oil-proof.

[0042] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the concept and scope of the present invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A non-sealed four-screw pump with two-stage oil-blocking venting, characterized in that: The pump includes a pump body, a screw bushing body, a middle section of the screw bushing, an upper section of the screw bushing, a driving screw, three driven screws, an exhaust valve, and a float. The driving screw is centrally mounted, and the three driven screws are evenly arranged around the outer periphery of the driving screw. The sealing cavity between the driving and driven screws is a non-sealed cavity for transporting gas-liquid two-phase media. The screw bushing body, the middle section of the screw bushing, and the upper section of the screw bushing are fitted onto the outside of the driving and driven screws. The middle section of the screw bushing is made of breathable steel. The middle section of the screw bushing forms an annular pore (KQ). The pores of the venting steel in the middle section of the screw bushing connect the screw working chamber with the annular pore (KQ). Gas entrained in the medium can pass through the venting steel and enter the annular pore (KQ). The annular pore (KQ) is connected upward to the exhaust valve. The exhaust valve is equipped with a Tesla valve flow channel structure, which allows gas to flow upward and generates flow resistance for the oil that escapes with the gas, thus inhibiting the upward movement of the oil. A float is provided at the top of the exhaust valve, and there is a certain gap between the float and the upper part of the cavity of the exhaust valve.

2. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 1, characterized in that, The driving screw adopts a cycloidal profile with double-headed convex teeth; the driven screw adopts a cycloidal profile with double-headed concave teeth.

3. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 1, characterized in that, The lead number of the driving screw and the driven screw is not less than 1.5 times.

4. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 1, characterized in that, The screw bushing body and the upper section of the screw bushing are made of dense, non-permeable metal, and the middle section of the screw bushing corresponds to the annular pore (KQ).

5. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 1, characterized in that, The exhaust valve is arranged vertically. The Tesla valve flow channel structure has multiple sets of reverse blocking teeth inside the valve cavity, which makes the upward flow resistance of gas small, the upward flow resistance of oil large, and the downward return resistance small. The oil accompanying the airflow returns to the jacket cavity by its own weight.

6. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 1, characterized in that, When there is no large amount of liquid in the accompanying gas flow, the gas overflowing from the exhaust valve bypasses the float and enters the cone orifice and channel to be discharged outside the pump. When the amount of oil in the accompanying gas increases significantly, the float, affected by buoyancy, rises and blocks the cone orifice, achieving automatic closure; when the oil volume decreases, the float falls back, and the exhaust channel reopens.

7. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 6, characterized in that, The float has a hollow structure, which facilitates its floating in the liquid.

8. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 6, characterized in that, The float is made of rubber, nylon, or coated with an elastic material, which allows it to effectively seal the conical orifice opening after liquid overflows.

9. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 1, characterized in that, A sealing ring is installed between the exhaust valve and the pump cover to prevent leakage of pressurized oil from the outlet.

10. The non-sealed four-screw pump with two-stage oil-blocking venting according to claim 1, characterized in that, This pump utilizes a Tesla valve to allow gas to flow upwards, blocking the oil that escapes with the gas, by leveraging the unidirectional resistance characteristic of the fluid. The upper end of the exhaust channel is connected to a float venting structure. When the amount of oil entering the channel increases and lifts it up, the float can close the exhaust channel. When the amount of oil decreases, the float falls back and reopens the exhaust channel, achieving a two-stage oil blocking and exhaust system of "exhausting when there is more gas and self-sealing when there is more oil". This can solve the problem of high vibration and noise in the gas-liquid mixed transportation condition of screw pumps and improve the operational stability of gas-liquid mixed transportation conditions.

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