A dry gas seal structure with a controllable gap combining dynamic pressure and static pressure

Abstract

A dry gas sealing structure with a combined dynamic and static pressure convergent gap includes a dynamic ring and a stationary ring. The sealing end face of the dynamic ring is divided into a diaphragm mating surface, a grooved end face with a fluid dynamic pressure groove, and a sealing dam. The ungrooved area on the grooved end face serves as a sealing dam. The stationary ring consists of a stationary ring sealing end face, a diaphragm assembly, a drainage channel, a fluid equalization groove, and a static pressure hole. The stationary ring sealing end face has circumferentially distributed axial drainage holes, which connect to the fluid equalization groove through the drainage channel and to an external gas supply pipeline through the static pressure hole. A one-way valve is installed on the gas supply pipeline near the static pressure hole. In this invention, gas is introduced into the sealing end face through the axial drainage holes and opened before the dry gas seal is started. When the seal is operating normally, the high-pressure gas at the root of the dynamic pressure groove is forced into the equalization groove, causing the diaphragm to deform differently due to the different forces on both sides, forming a convergent gap along the radial leakage direction of the medium, ultimately becoming a dry gas sealing structure with a combined dynamic and static pressure convergent gap.

Description

Technical Field

[0001] This invention relates to the field of shaft end sealing technology for various high-speed compressors, turbopumps and other rotating machinery, and particularly to a dry gas sealing structure with a controllable clearance combining dynamic and static pressure. Background Technology

[0002] Various dynamic and static pressure grooves are created on the sealing end face to enhance the fluid film's load-bearing capacity and rigidity, enabling non-contact operation between the sealing pairs—a common technique in gas or liquid lubricated mechanical seals. A mechanical seal pair consists of a rotating ring that follows the shaft and a mating stationary ring. When the rotating ring rotates, the dynamic pressure grooves on its end face pump the fluid medium from the sealing cavity into the sealing gap. Under the combined action of pressure difference and circumferential shear, the fluid medium flows downstream towards the low-pressure side and the windward side within the grooves, continuously being compressed. This increases the gas film pressure on the windward side and at the groove root, creating a dynamic pressure effect. This results in a gas film several micrometers thick between the sealing end faces, ensuring the sealing pairs operate without contact between the end faces. Dry gas seals have a much smaller sealing gap in the non-working phase than in the stable working phase, and the process from end face opening to the formation of a stable gas film often leads to unnecessary losses. Traditional dry gas seals, after processing, can only adjust the sealing gap during assembly by applying pre-deformation; in the working phase, they rely on a rigid gas film to form the sealing gap. During the opening phase, the dynamic and static ring end faces of dry gas seals often fail due to insufficient gas film bearing capacity and stiffness, as well as inadequate resistance to external disturbances, leading to end face rubbing or vibration instability. Therefore, reducing end face rubbing or vibration instability during the opening phase or low film thickness operation, and achieving rapid transition to stable operation, is crucial for the design and application of dry gas seals in shaft end seals of various high-speed compressors, turbopumps, and other rotating machinery. Summary of the Invention

[0003] To overcome the above problems, the present invention provides a dry gas sealing structure with a controllable gap that combines dynamic and static pressure.

[0004] The technical solution adopted in this invention is: a dry gas sealing structure with controllable gap combining dynamic and static pressure, the dry gas sealing structure is composed of a dynamic ring (1) and a stationary ring (2), the inner diameter side of the stationary ring (2) is the low pressure side, and the outer diameter side is the high pressure side; the sealing end face of the dynamic ring (1) is divided into a diaphragm mating surface (11), a groove end face (12) with a fluid dynamic pressure groove (121) and a sealing dam (123), the ungrooved area on the groove end face (12) is a sealing weir (122);

[0005] The stationary ring (2) includes a stationary ring sealing end face (21), a diaphragm assembly (22), a drainage channel (23), a fluid equalization groove (24), and a static pressure hole (25). The diaphragm assembly (22) includes a diaphragm (221), a diaphragm mating surface (26), a fastening screw (222), and a pressure ring (223). The stationary ring sealing end face (21) has circumferentially distributed axial drainage holes (231), which are connected to the fluid equalization groove (24) through the drainage channel (23). It is connected to an external air supply line through a static pressure hole (25), and a one-way valve (3) is installed on the side of the air supply line near the static pressure hole (25); the diaphragm (221) is made of high-strength elastic metal material and is fixed on the diaphragm mating surface (26) together with the pressure ring (223) by the fastening screw (222); the drainage channel (23) of the static ring (2) is composed of an axial drainage hole (231), a radial flow hole (232) and an axial outlet hole (233). Among them, the axial drainage hole (231) is connected to the sealing end face (21) of the static ring, the axial outlet hole (233) is connected to the fluid equalization groove (232), and the radial flow hole (232) is connected to the static pressure hole (25) located on the outer side of the static ring (2) and is centrally symmetrically distributed;

[0006] When the dry gas seal is operating normally, the inner side (2211) of the diaphragm (221) is subjected to constant gas pressure from the axial drainage hole (231) in the fluid equalization groove (24), and the outer side (2212) of the diaphragm (221) is subjected to leakage gas pressure between the sealing end faces of the dynamic and static rings. The pressure difference between the inner side (2211) and the outer side (2212) gradually increases along the leakage direction of the medium, which causes the radial micro-deformation of the diaphragm (221) to increase accordingly, and finally forms a convergent gap with the mating surface (11) of the diaphragm along the radial leakage direction of the medium.

[0007] Furthermore, the radius of the center line connecting the axial drainage holes (231) of the stationary ring sealing end face (21) is equal to the radius of the root of the dynamic pressure groove (121) of the dynamic ring (2) sealing end face.

[0008] Furthermore, the groove end face (12) of the moving ring (1) is not on the same plane as the diaphragm mating surface (11), and the protrusion height of the groove end face (12) relative to the diaphragm mating surface (11) is 0.02 to 0.10 mm.

[0009] Furthermore, the static pressure hole (25) is connected to the external gas supply line, and a one-way valve (3) is used to prevent high-pressure gas from the axial drainage hole (231) from entering the gas supply line.

[0010] Furthermore, the outer end face (2212) of the diaphragm (221) and the sealing end face (21) of the stationary ring are on the same plane, and the thickness of the diaphragm (221) is 0.05 to 0.20 mm.

[0011] Furthermore, the diaphragm (221) is secured to the stationary ring (2) by means of a pressure ring (223) through the through holes of its inner and outer rings by multiple fastening screws (222).

[0012] The principle of this invention is:

[0013] The classic dry gas seal end face mainly consists of three parts: a dynamic pressure groove, a sealing weir, and a sealing dam. The area circumferentially between adjacent dynamic pressure grooves is the sealing weir, which plays a role in blocking the circumferential flow of the sealing medium during the operation of the dry gas seal. The sealing dam is used to block the radial flow of the sealing medium. When the rotating ring rotates, the sealing medium is pumped into the sealing gap through the dynamic pressure groove and pressurized due to the flow obstruction effect of the sealing weir and sealing dam, thus forming a significant high-pressure zone near the windward side wall and groove root. This dynamic pressure effect is more pronounced under low film thickness and high speed conditions. Extensive theoretical research and engineering application experience show that dry gas seals are characterized by small sealing gaps and difficulty in pumping in sealing gas during start-up and shutdown phases and operation with low film thickness. During this process, seal instability and end face rubbing are very likely to occur.

[0014] When the dry gas seal of this invention is used as a shaft end seal, high-pressure gas is introduced into the sealing gap through the static pressure hole during the opening phase, allowing the end face to open rapidly. As the rotating ring rotates, the sealing medium is pumped into the sealing groove from the outer diameter side and continuously compressed within the groove, causing the gas film pressure on the windward side and at the groove root to increase. The high-pressure sealing gas at the groove root enters the air inlet channel through the air inlet groove on the stationary ring end face and enters the fluid equalization groove through the drainage channel, forming a high-pressure ring on the inner end face of the diaphragm that is higher than the end face gap pressure, creating a pressure difference with the sealing gap, thereby causing the diaphragm to undergo a slight convex bending deformation. When the dry gas seal enters the stable operation phase, the one-way pressure regulating valve closes, and the pressure in the fluid equalization groove is uniformly distributed radially due to Dalton's law of partial pressure. However, the gas pressure in the gas film gap continuously decreases from the outer diameter to the inner diameter. Therefore, the pressure difference between the inner and outer diameters of the diaphragm is inconsistent, with the pressure difference being greater closer to the inner diameter side. This results in a greater load on the diaphragm, causing greater deformation of the diaphragm, which leads to a convergent gap between the end faces of the rotating and stationary rings, facilitating the pumping of sealing gas. The dry gas seal structure of the present invention, which combines dynamic and static pressure and features a variable gap for air intake in the middle of the stationary ring end face, can achieve rapid opening of the sealing end face, enhance the stability of the dry gas seal under low film thickness operation, and adapt the deformation of the diaphragm to the rotational speed and pressure. It is suitable for shaft end sealing of rotating machinery under various working conditions.

[0015] The beneficial effects of this invention are:

[0016] (1) By introducing air through the static pressure hole, the sealing end face can be opened quickly, avoiding the occurrence of end face rubbing.

[0017] (2) After high-pressure gas is introduced into the fluid equalization groove, the diaphragm on the sealing end face can deform to generate a convergent gap, which enhances the stability of the dry gas seal during operation. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the dynamic and static ring pair in an embodiment of the present invention.

[0019] Figure 2 This is an exploded view of the dry gas sealing structure of the dynamic-static pressure combined convergent gap in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the dynamic ring end face of an embodiment of the present invention;

[0021] Figure 4 This is a schematic diagram of the stationary ring end face of the mounting diaphragm in an embodiment of the present invention;

[0022] Figure 5 This is a three-dimensional perspective view of a partial cross-section of the static ring in an embodiment of the present invention;

[0023] Figure 6 This is a schematic diagram of the diaphragm deforming under stress to form a convergent gap in an embodiment of the present invention. Detailed Implementation

[0024] The technical solution of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Reference Figure 1 , 2 3, 4, 5, and 6 describe a dry gas sealing structure with a convergent gap that combines dynamic and static pressure. The dry gas seal consists of a dynamic ring 1 and a stationary ring 2. The inner diameter side of the stationary ring 2 is the low-pressure side, and the outer diameter side is the high-pressure side. The sealing end face of the dynamic ring 1 is functionally divided into a diaphragm mating surface 11, a grooved end face 12 with a fluid dynamic pressure groove 121, and a sealing dam 123. The ungrooved area on the grooved end face 12 is a sealing dam 122. The stationary ring 2 consists of a stationary ring sealing end face 21, a diaphragm assembly 22, a drainage channel 23, a fluid equalization groove 24, and a static pressure hole 25. The diaphragm assembly 22 consists of a diaphragm 221, a diaphragm mating surface 26, and a pressure ring 223. The stationary ring sealing end face 21 has circumferentially distributed axial drainage holes 231, which are connected to the fluid equalization groove 24 through the drainage channel 23 and to the external air supply pipeline through the static pressure hole 25. A one-way valve 3 is installed on the air supply pipeline near the static pressure hole 25. The diaphragm 221 is made of high-strength elastic metal material and is fixed to the diaphragm mating surface 26 by the fastening screw 222 and the pressure ring 223.

[0028] The flow channel 23 of the stationary ring 2 consists of an axial flow channel 231, a radial flow channel 232, and an axial outflow channel 233. The axial flow channel 231 connects to the sealing end face 21 of the stationary ring, the axial outflow channel 233 connects to the fluid equalization groove 232, and the radial flow channel 232 connects to the static pressure holes 25 on the outer surface of the stationary ring 2, and they are centrally symmetrically distributed. The function of the static pressure holes 25 is to inject static pressure gas from the external gas supply line during the sealing opening phase, forming a static pressure gas film between the sealing end faces, thus enabling the end faces to open rapidly.

[0029] When the rotating ring 1 is in a rotating state, the sealing gas continuously increases in pressure as it flows along the dynamic pressure groove 121 towards the groove root. It then enters the fluid equalization groove 24 through the axial drainage hole 231 on the stationary ring end face, creating a positive pressure difference between the fluid equalization groove 24 and the sealing end face. The diaphragm 221 can undergo slight deformation under the influence of the airflow pressure difference between the fluid equalization groove 24 and the sealing gap, forming a convergent gap with the diaphragm mating surface 11. The radius of the center line connecting the axial drainage holes 231 on the stationary ring sealing end face 21 is equal to the radius of the groove root of the dynamic pressure groove 121 on the rotating ring 2 sealing end face.

[0030] The rotating ring 1 has a height difference between its rotating ring sealing end face 12 and the diaphragm mating surface 11 to prevent the diaphragm from contacting the rotating ring sealing end face due to excessive deformation, thus avoiding the adverse effect of end face rubbing. The protrusion height ranges from 0.02 to 0.10 mm. The static pressure hole 25 is connected to the external air supply pipeline, and the intake pressure is controlled by the one-way valve 3.

[0031] The diaphragm 221 is securely fixed to the stationary ring 2 by means of multiple fastening screws 222 passing through the through holes of its inner and outer rings, respectively, and by means of a pressure ring 223. The outer end face 2212 of the diaphragm 221 is on the same plane as the sealing end face 21 of the stationary ring, and the thickness of the diaphragm 221 is 0.05 to 0.20 mm.

[0032] Reference Figure 6 This paper mainly explains the formation mechanism of the convergent gap in the dry gas sealing structure of the dynamic-static pressure combined convergent gap of the present invention. The inner diameter side of the sealing pair is the high-pressure side, and the outer diameter side is the low-pressure side. During the opening stage, high-pressure gas is introduced into the sealing gap through the static pressure hole 25, which causes the dynamic ring sealing end face 12 to open quickly. As the dynamic ring 1 rotates, the sealing medium is pumped into the dynamic pressure groove 121 from the outer diameter side and is continuously compressed in the groove, resulting in an increase in the gas film pressure on the windward side and at the root of the groove. The high-pressure sealing gas at the root of the groove enters the drainage channel 23 through the axial drainage hole 233 of the static ring sealing end face 21, and enters the fluid equalization groove 24 through the axial outlet hole 233. A high-pressure gas ring with a pressure higher than the end face gap is formed in the fluid equalization groove 24, and a pressure difference is formed between it and the sealing gap. At this time, the load acting on the inner end face 2211 of the diaphragm is greater than the load F2 on the outer end face 2212 of the diaphragm, which causes the diaphragm 221 to undergo a slightly convex bending deformation. When the dry gas seal enters a stable operating phase, the one-way pressure regulating valve 3 closes. The pressure within the fluid equalization groove 24 is uniformly distributed radially due to Dalton's law of partial pressures. However, the gas film pressure in the end-face gap continuously decreases from the outer diameter to the inner diameter. Therefore, the pressure difference between the inner and outer diameters of the diaphragm 221 is inconsistent, with the pressure difference increasing closer to the inner diameter. This results in a greater load on the diaphragm, causing greater deformation and leading to a convergent gap between the end faces of the rotating and stationary rings. This facilitates the pumping of sealing gas.

[0033] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this invention should not be considered as limited to the specific forms stated in the embodiments. The scope of protection of this invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A dry gas sealing structure with a controllable gap combining dynamic and static pressure, the dry gas sealing structure comprising a dynamic ring (1) and a stationary ring (2), wherein the inner diameter side of the stationary ring (2) is the low-pressure side and the outer diameter side is the high-pressure side; characterized in that: The sealing end face of the dynamic ring (1) is divided into a diaphragm mating face (11), a groove end face (12) with a fluid dynamic pressure groove (121) and a sealing dam (123). The ungrooved area on the groove end face (12) is a sealing weir (122). The stationary ring (2) includes a stationary ring sealing end face (21), a diaphragm assembly (22), a drainage channel (23), a fluid equalization groove (24), and a static pressure hole (25). The diaphragm assembly (22) includes a diaphragm (221), a diaphragm mating surface (26), a fastening screw (222), and a pressure ring (223). The stationary ring sealing end face (21) has circumferentially distributed axial drainage holes (231), which are connected to the fluid equalization groove (24) through the drainage channel (23) and to an external air supply pipeline through the static pressure hole (25). A one-way valve (3) is installed on the side of the air supply pipeline near the static pressure hole (25). The diaphragm (221) is made of high-strength elastic metal material and is fixed to the diaphragm mating surface (26) together with the pressure ring (223) by the fastening screw (222); the drainage channel (23) of the stationary ring (2) is composed of an axial drainage hole (231), a radial flow hole (232) and an axial outflow hole (233); wherein, the axial drainage hole (231) is connected to the sealing end face (21) of the stationary ring, the axial outflow hole (233) is connected to the fluid equalization groove (24), and the radial flow hole (232) is connected to the static pressure hole (25) located on the outer side of the stationary ring (2) and is centrally symmetrically distributed; When the dry gas seal is operating normally, the inner end face (2211) of the diaphragm (2211) is subjected to constant gas pressure from the axial drainage hole (231) in the fluid equalization groove (24), and the outer end face (2212) of the diaphragm is subjected to leakage gas pressure between the sealing end faces of the dynamic and static rings. The pressure difference between the inner end face (2211) and the outer end face (2212) of the diaphragm gradually increases along the leakage direction of the medium, which causes the radial micro-deformation of the diaphragm (221) to increase accordingly, and finally forms a convergent gap with the mating surface (11) of the diaphragm along the radial leakage direction of the medium. The radius of the center line connecting the axial drainage holes (231) of the stationary ring sealing end face (21) is equal to the radius of the root of the dynamic pressure groove (121) of the dynamic ring (1) sealing end face.

2. The dry gas sealing structure with controllable gap based on dynamic and static pressure as described in claim 1, characterized in that: The groove end face (12) of the moving ring (1) is not on the same plane as the diaphragm mating surface (11), and the protrusion height of the groove end face (12) relative to the diaphragm mating surface (11) is 0.02~0.10mm.

3. The dry gas sealing structure with controllable gap based on dynamic and static pressure as described in claim 1, characterized in that: The static pressure hole (25) is connected to the external gas supply line and a one-way valve (3) prevents high-pressure gas from the axial drainage hole (231) from entering the gas supply line.

4. The dry gas sealing structure with controllable gap based on dynamic and static pressure as described in claim 1, characterized in that: The outer end face (2212) of the diaphragm (221) and the sealing end face (21) of the stationary ring are on the same plane, and the thickness of the diaphragm (221) is 0.05~0.20mm.

5. The dry gas sealing structure with controllable gap based on dynamic and static pressure as described in claim 1, characterized in that: The diaphragm (221) is secured to the stationary ring (2) by means of a pressure ring (223) through the through holes of its inner and outer rings by multiple fastening screws (222).

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