Double-ladder shrinkage type spiral groove gas film sealing structure

Abstract

This invention discloses a double-step contraction spiral groove air film sealing structure. The spiral grooves on the sealing ring end face are sequentially arranged from the leeward side to the windward side, comprising a first spiral groove section, a second spiral groove section, and a third spiral groove section. The first spiral groove section is a three-stage contraction structure, and the second spiral groove section is a two-stage contraction structure. By employing a double-step contraction spiral groove structure, this invention effectively enhances the blocking and pressure-boosting effects of airflow within the spiral grooves, thereby increasing the opening force of the air film seal. Simultaneously, by setting different groove depth and length ratios, the guiding and shearing effects of airflow within the spiral grooves can be effectively enhanced, thereby reducing the leakage of the air film seal. Furthermore, this invention possesses advantages such as unique structure, good adjustability, and wide applicability, making it a promising new sealing structure.

Description

Technical Field

[0001] This invention belongs to the technical field of sealing the bearing cavity of aero-engine compressors, and relates to a spiral groove air film sealing structure, specifically a double-step contraction type spiral groove air film sealing structure. It utilizes the variation of groove depth to improve sealing performance and the variation of groove shape to optimize the air film sealing flow field, thereby reducing leakage and improving air film sealing performance. Background Technology

[0002] To meet the demands of higher engine speeds and more stringent thermodynamic cycle parameters in aero-engines, more stringent performance requirements are placed on compressors. In addition to traditional flow path design, a redesign of the sealing flow is necessary to satisfy these performance specifications. The sealing system is a crucial auxiliary system in the compressor, preventing high-pressure gas from leaking from the compressor's interior to the exterior. The amount of leakage directly impacts engine performance and reliability. Studies have shown that a 1% reduction in sealing system leakage leads to a 1% increase in engine thrust.

[0003] Currently, commonly used sealing structures in compressors include toothed seals, brush seals, and volute seals. These sealing structures are all based on the principle of contact sealing to prevent gas leakage, and their main drawbacks include large leakage, severe friction and wear, and short lifespan. Compared to traditional sealing structures, film seals are a non-contact sealing structure. They utilize the principles of fluid dynamics to form a stable gas film between the seal and the rotor to prevent gas leakage. They inherently have lower leakage and no contact wear during the sealing process, which can improve engine reliability and lifespan. In addition, film seals also have the advantages of strong adaptability, simple structure, and low manufacturing cost.

[0004] The key component of the gas film seal is the helical groove. The shape, depth, width, spacing, and inclination angle of the helical groove determine the performance of the gas film seal. In order to optimize the design of the gas film seal, based on the analysis of its flow field characteristics, the following three aspects need to be considered: (1) The opening force of the gas film seal. When the gas film seal is not working, it generates a thrust due to its inlet pressure being higher than its outlet pressure, forming an initial gap between it and the rotor. This thrust is called the opening force, which ensures the normal start-up of the gas film seal. Due to the high-altitude flight environment of the aero-engine, the inlet pressure of the gas film seal is low, resulting in a reduction in the opening force, which may cause the gas film seal to fail to start or to be damaged by contact with the rotor. (2) The load-bearing capacity of the gas film seal. When the gas film seal is working, a pressure difference is generated due to its internal flow field, forming a stable gap between it and the rotor. This pressure difference is called the load-bearing capacity, which ensures the normal operation of the gas film seal. The load-bearing capacity is related to the parameters of the helical groove and the working parameters, and needs to meet the condition that the load-bearing capacity is greater than the external load. Due to the high-speed rotation and high-temperature environment of the aero-engine, there is a large shear force and thermal deformation between the gas film seal and the rotor, which leads to an increase in external load and may cause insufficient load-bearing capacity of the gas film seal or damage to the rotor. (3) Leakage of the gas film seal. When the gas film seal is working, due to the certain flow resistance in its internal flow field, a leakage flow is generated at its outlet. The leakage is related to the structural parameters and operating parameters of the spiral groove, and the leakage needs to be reduced as much as possible. At the same time, it is also necessary to consider the influence of fluid viscosity, compressibility, turbulence effect and other factors on the leakage, as well as the coupling effect of eccentricity and dynamic deformation between the gas film seal and the rotor.

[0005] In summary, film seal technology shows promising application prospects in aero-engines. However, its application in aero-engines also faces a series of pressing technical challenges: First, to better meet the higher performance requirements of aero-engines, it is still necessary to further improve the sealing performance of the film seal and reduce its leakage. Second, due to the high-altitude flight environment of aero-engines, the inlet pressure of the film seal is lower, resulting in a reduced opening force and consequently a decrease in the stiffness-to-leakage ratio, thus reducing the load-bearing capacity of the film seal. Solving these technical problems requires meticulous engineering design and innovative solutions to further enhance the sealing performance and reliability of the film seal. Summary of the Invention

[0006] (I) Purpose of the Invention

[0007] To address the aforementioned deficiencies and shortcomings of existing technologies, and to solve the technical problems of large leakage, low opening force, and low stiffness-to-leakage ratio in traditional air-film seals under low inlet pressure, this invention aims to provide a double-step contraction spiral groove air-film seal structure. By optimizing the traditional spiral groove structure into a double-step contraction spiral groove structure, the sealing performance is improved by varying the groove depth and shape. The three-stage stepped design at the inlet optimizes the air-film seal flow field, thereby reducing leakage and improving air-film seal performance. Furthermore, its overall structure is relatively simple, and its manufacturing difficulty is no different from traditional air-film seal structures, but its sealing performance and lifespan are significantly improved, making it a promising candidate for widespread applications.

[0008] (II) Technical Solution

[0009] To achieve the objective of this invention, the present invention adopts the following technical solution:

[0010] The first objective of this invention is to provide a double-step contraction type spiral groove gas film sealing structure, comprising at least a sealing ring that rotates during operation. At least one end face of the sealing ring is formed as an annular sealing end face. The radially outer side of the annular sealing end face is the high-pressure gas side, and the radially inner side is the low-pressure gas side. A plurality of spiral grooves are provided circumferentially on the annular sealing end face. The end face region between adjacent spiral grooves forms a sealing weir, and the end face region between the spiral grooves and the low-pressure gas side forms a sealing dam. The invention is characterized by...

[0011] Each of the spiral grooves has a structure with one end open and the other end closed in the radial direction. The open end extends radially outward to communicate with the high-pressure gas side and forms the air inlet of the spiral groove. The closed end extends radially inward to the sealing dam and forms the groove root of the spiral groove. The two side walls of each spiral groove in the circumferential direction are respectively formed as its windward side and leeward side, wherein the windward side faces the inlet gas entering the spiral groove, and the leeward side is opposite to the windward side.

[0012] Each of the aforementioned spiral grooves spatially comprises a first spiral groove portion, a second spiral groove portion, and a third spiral groove portion arranged circumferentially from its leeward side to its windward side, and the three spiral groove portions extend radially from the opening end of the spiral groove to its root, wherein...

[0013] The first spiral groove portion is arranged on the windward side of the spiral groove in the circumferential direction, and spatially includes a first step portion, a second step portion, and a third step portion arranged sequentially from the radial outer side to the radial inner side. The first step portion has a constant groove depth h1 along its length direction, the second step portion has a constant groove depth h2 along its length direction, and the third step portion has a constant groove depth h3 along its length direction, wherein the groove depth h1 > groove depth h2 > groove depth h3, so that the first spiral groove portion is formed as a three-stage stepped contraction shape from the radial outer side to the radial inner side along its length direction.

[0014] The second spiral groove portion is located circumferentially between the first spiral groove portion and the third spiral groove portion, and spatially includes a stepped portion I and a stepped portion II arranged sequentially from the radially outer side to the radially inner side. The stepped portion I has a constant groove depth H1 along its length direction, and the stepped portion II has a constant groove depth H2 along its length direction, wherein the groove depth H1 > the groove depth H2, so that the second spiral groove portion is formed as a two-stage stepped contraction shape from the radially outer side to the radially inner side along its length direction.

[0015] The third spiral groove portion is arranged on the leeward side of the spiral groove in the circumferential direction, and includes a main stepped portion extending from the radially outer side to the radially inner side in space, the main stepped portion having a constant groove depth H0 along its length direction;

[0016] Furthermore, the opening end of each spiral groove includes a first step portion located in the first spiral groove portion, a step portion I located in the second spiral groove portion, and a main step portion located in the third spiral groove portion, and the groove depth H1 of the step portion I is greater than the groove depth h1 of the first step portion and the groove depth H0 of the main step portion, so that the opening end of the spiral groove is formed in a three-stage stepped contraction shape along the circumferential direction from the leeward side to the windward side;

[0017] Furthermore, the sum of the extension lengths of the first step portion and the second step portion in the first spiral groove portion is equal to the extension length of the step portion I in the second spiral groove portion, and the arc-shaped groove roots of the second step portion in the first spiral groove portion and the step portion I in the second spiral groove portion have the same second groove root radius R2 and are continuously integrated in the circumferential direction, and the second groove root radius R2 is smaller than the first groove root radius R3 of the arc-shaped groove root of the first step portion in the first spiral groove portion;

[0018] The sum of the extension lengths of the three steps in the first spiral groove portion is equal to the sum of the extension lengths of the two steps in the second spiral groove portion and the extension length of the main step in the third spiral groove portion. The arc-shaped groove roots of the third step in the first spiral groove portion, the step II in the second spiral groove portion, and the main step in the third spiral groove portion have the same third groove root radius R1 and are continuously integrated in the circumferential direction. The third groove root radius R1 is smaller than the second groove root radius R2.

[0019] Preferably, the first groove root radius R3 satisfies R3=2 / 3(R4-R1)+R1, and the second groove root radius R2 satisfies R2=1 / 3(R4-R1)+R1, where the radius R4 is the radius of the opening end of the spiral groove 3.

[0020] Preferably, the arc length at the entrance of the first step is S3, the sum of the arc lengths at the entrances of the first step 1 and step I1 is S2, and the sum of the arc lengths at the entrances of the first step, step I, and main step is S1, wherein S2 = 0.75S1 and S3 = 0.5S1.

[0021] Preferably, the groove depth h2 of the second step is the same as the groove depth H1 of step I, the groove depth h3 of the third step is the same as the groove depth H2 of step II and the groove depth H0 of the main step, and in the three steps of the first spiral groove, the groove depth h1 is about 4 to 5 μm, the groove depth h2 is about 3 to 4 μm, and the groove depth h3 is about 2 to 3 μm.

[0022] Preferably, the ratio of the extension lengths of the three steps in the first spiral groove portion is approximately 1:1:1, and the ratio of the extension lengths of the two steps in the second spiral groove portion is approximately 2:1.

[0023] Preferably, by flexibly adjusting the groove depth of the three stepped sections in the first spiral groove section and the two stepped sections in the second spiral groove section, the pressure-boosting effect of the spiral groove and the distribution of the inlet low-pressure zone can be adjusted, thereby reducing the leakage of the gas film seal and improving the rigid-leakage ratio of the gas film seal.

[0024] Preferably, a plurality of micro-grooves are provided on the annular sealing end face. The micro-grooves are distributed on the sealing weir and communicate with the high-pressure fluid side to increase the circumferential contact area between the airflow and the sealing weir, thereby enhancing the shearing effect and pressure boosting effect.

[0025] Preferably, a plurality of annular micro-partitions are provided on the annular sealing end face. The annular micro-partitions are distributed on the sealing dam and communicate with the low-pressure fluid side to reduce the circumferential contact area between the airflow and the sealing dam, thereby reducing the leakage and the stiffness-to-leakage ratio.

[0026] Preferably, micro-recesses are distributed on the three stepped portions in the first spiral groove portion and the two stepped portions in the second spiral groove portion to increase the contact area between the airflow and each stepped portion, thereby enhancing the shearing effect and pressure boosting effect.

[0027] The second objective of this invention is to provide a sealing structure for the bearing cavity of an aero-engine compressor, characterized in that the sealing structure is provided with the double-step shrinkage spiral groove air film sealing structure described in the first objective.

[0028] (III) Technical Effects

[0029] Compared with the prior art, the double-step shrinkage spiral groove air film sealing structure of the present invention has the following beneficial and significant technical effects:

[0030] (1) The double-step shrinkage spiral groove air film sealing structure of the present invention can increase the circumferential contact area between the airflow and the wall by setting the double-step shrinkage spiral groove structure, and better utilize the shear effect to increase the fluid dynamic pressure and increase the circumferential velocity of the fluid in the groove area, thereby reducing the radial outflow of the air film seal and reducing the leakage.

[0031] (2) The double-step contraction spiral groove air film sealing structure of the present invention forms three stepped groove root regions, i.e., three blocking regions, in the radial direction by setting a double-step contraction spiral groove structure. This allows the airflow to be continuously compressed in the reverse direction along the radius, and continuously blocks the airflow at the groove root, promoting the conversion of fluid dynamic pressure into fluid static pressure effect. Therefore, a significant pressure increase effect will occur at the groove root of the two stepped contraction spiral grooves, thereby increasing the overall opening force of the air film seal.

[0032] (3) The double-step contraction spiral groove air film sealing structure of the present invention, by setting a three-step inlet configuration, can form a good guiding effect on the inlet airflow and form a good constraint on the flowing fluid. At the same time, thanks to the contraction spiral groove structure, three stepped opening end regions are formed in the circumferential direction, that is, three guiding regions, which allow the airflow to be continuously guided in the reverse direction along the circumference, and continuously create airflow guidance at the opening end, promoting uniform distribution of fluid circumferential velocity.

[0033] (4) The double-step shrinking spiral groove air film sealing structure of the present invention can effectively adjust the pressure-boosting effect of the spiral groove and the distribution of the inlet low-pressure zone by flexibly adjusting the groove depth and length ratio of each step in the double-step shrinking spiral groove, thereby reducing the leakage of the air film seal and improving the rigid-leakage ratio of the air film seal.

[0034] (5) The double-step contraction spiral groove air film sealing structure of the present invention, by setting several micro-grooves, annular micro-partitions and micro-recesses on the annular sealing end face, can further enhance the shear effect and pressure boosting effect, increase the contact area between the airflow and the sealing weir, sealing dam and each step, and reduce the leakage and stiffness-to-leakage ratio. These auxiliary structures can be flexibly designed and adjusted according to different working conditions and requirements to improve the adaptability and reliability of the air film seal.

[0035] (6) Compared with the prior art, the double-step shrinkage spiral groove air film sealing structure of the present invention can effectively improve the sealing performance and service life of the air film seal, and has broad application prospects. The double-step shrinkage spiral groove air film sealing structure of the present invention has a unique structure, good adjustability, and wide application. It has passed the numerical simulation verification of air film sealing under different parameters, and its technical effect is reliable and repeatable. Attached Figure Description

[0036] Figure 1 The diagram shown is an overall schematic diagram of the double-step shrink-type spiral groove air film seal of the present invention;

[0037] Figure 2 As shown Figure 1 Schematic diagram of section 6-6;

[0038] Figure 3 As shown Figure 1 Schematic diagram of section 7-7;

[0039] Figure 4 As shown Figure 1 Schematic diagram of section 8-8;

[0040] Figure 5 The diagram shown is a partial structural schematic of a single groove of the double-step shrinking spiral groove air film seal of the present invention.

[0041] Figure 6 The diagram shows a comparison of the radial pressure distribution of the double-step shrinkage spiral groove air film sealing structure of the present invention with that of the original structure (traditional stepless spiral groove air film sealing structure).

[0042] Figure 7 The diagram shows a comparison of pressure cloud diagrams between the double-step shrinkage spiral groove air film sealing structure of the present invention and the traditional spiral groove structure. (a) is the pressure cloud diagram of the traditional spiral groove structure, and (b) is the pressure cloud diagram of the double-step shrinkage spiral groove air film sealing structure of the present invention.

[0043] Explanation of reference numerals in the attached figures:

[0044] 1-Sealing dam, 2-Sealing weir, 3-Spiral groove, 4-Single double-step shrinkable spiral groove air film sealing structure, 5-Rotation direction, 6-First spiral groove section, 61-First step section, 62-Second step section, 63-Third step section, 7-Second spiral groove section, 71-Step section I, 72-Step section II, 8-Third spiral groove section, 80-Main step section. Detailed Implementation

[0045] To better understand the present invention, the following embodiments further illustrate its content. Throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The described embodiments are some, but not all, of the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The structure and technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings, providing one embodiment of the present invention.

[0046] Figure 1 The diagram shows the overall design of the double-step contraction spiral groove air film seal of the present invention. It can be seen that this structure optimizes the spiral groove structure based on the traditional spiral groove air film seal. Figure 5 The diagram shown is a partial structural schematic of a single groove of the double-step contraction type spiral groove air film seal of the present invention. The radial contraction is designed as three spiral groove sections; the inlet contracts circumferentially, designed as a three-stage contraction step. Figures 2-4 As shown Figure 1 Schematic diagram of the cross-sectional structure at sections 6-6, 7-7, and 8-8.

[0047] Specifically, such as Figures 1-5 As shown, the double-step contraction type spiral groove air film sealing structure of the present invention includes at least one sealing ring that rotates during operation, and the direction of rotation is as follows: Figure 1As shown in Figure 5, at least one end face of the sealing ring is formed as an annular sealing end face. The radially outer side of the annular sealing end face is the high-pressure gas side, and the radially inner side is the low-pressure gas side. A plurality of spiral grooves 3 are provided on the annular sealing end face along its circumference. The end face area between adjacent spiral grooves 3 forms a sealing weir 2, and the end face area between the spiral groove 3 and the low-pressure gas side forms a sealing dam 1. Each spiral groove 3 has a structure with one end open and one end closed in the radial direction. Its open end extends radially outward to communicate with the high-pressure gas side and forms the air inlet of the spiral groove. Its closed end extends radially inward to the sealing dam 1 and forms the groove root of the spiral groove 3. The two side walls in the circumferential direction of each spiral groove 3 are respectively formed as its windward side and leeward side. The windward side faces the inlet gas entering the spiral groove 3, and the leeward side is opposite to the windward side.

[0048] Each spiral groove 3 spatially comprises a first spiral groove portion 6, a second spiral groove portion 7, and a third spiral groove portion 8 arranged circumferentially from its leeward side to its windward side. All three spiral groove portions extend radially from the opening end of the spiral groove 3 to its root. The first spiral groove portion 6 is arranged circumferentially near the windward side of the spiral groove 3 and spatially comprises a first step portion 61, a second step portion 62, and a third step portion 63 arranged sequentially from radially outer to radially inner. The first step portion 61 has a constant groove depth h1 along its length, the second step portion 62 has a constant groove depth h2 along its length, and the third step portion 63 has a constant groove depth h3 along its length, wherein groove depth h1 > groove depth h2 > groove depth h3, such that the first spiral groove portion 6 extends radially from its leeward side to its windward side. The entire spiral groove 7 is formed in a three-stage stepped contraction shape from the radial outer side to the radial inner side. The second spiral groove portion 7 is located between the first spiral groove portion 6 and the third spiral groove portion 8 in the circumferential direction, and includes a step portion I 71 and a step portion II 72 arranged sequentially from the radial outer side to the radial inner side in the spatial direction. The step portion I 71 has a constant groove depth H1 along its length direction, and the step portion II 72 has a constant groove depth H2 along its length direction. The groove depth H1 > the groove depth H2, so that the second spiral groove portion 7 is formed in a two-stage stepped contraction shape from the radial outer side to the radial inner side in the spatial direction. The third spiral groove portion 8 is arranged on the leeward side of the spiral groove 3 in the circumferential direction, and includes a main step portion 80 extending from the radial outer side to the radial inner side in the spatial direction. The main step portion 80 has a constant groove depth H0 along its length direction.

[0049] Furthermore, the opening end of each spiral groove 3 includes a first step portion 61 located in the first spiral groove portion 6, a step portion I 71 located in the second spiral groove portion 7, and a main step portion 80 located in the third spiral groove portion 8. The groove depth H1 of the step portion I is greater than the groove depth h1 of the first step portion, which is greater than the groove depth H0 of the main step portion 80. This makes the opening end of the spiral groove 3 form a three-stage stepped contraction shape along the circumferential direction from the leeward side to the windward side. The sum of the extension lengths of the first step portion 61 and the second step portion 62 in the first spiral groove portion 6 is equal to the extension length of the step portion I 71 in the second spiral groove portion 7. The arc-shaped groove roots of the second step portion 62 in the first spiral groove portion 6 and the step portion I 71 in the second spiral groove portion 7 have the same second groove root radius R2 and are continuously integrated in the circumferential direction. The second groove root radius R2 is smaller than the first groove root radius R3 of the arc-shaped groove root of the first step portion 61 in the first spiral groove portion 6.

[0050] Furthermore, the sum of the extension lengths of the three steps in the first spiral groove portion 6 is equal to the sum of the extension lengths of the two steps in the second spiral groove portion 7 and the extension length of the main step portion 80 in the third spiral groove portion 8. Moreover, the arc-shaped groove roots of the third step portion 63 in the first spiral groove portion 6, the step portion II 72 in the second spiral groove portion 7, and the main step portion 80 in the third spiral groove portion 8 have the same third groove root radius R1 and are continuously integrated in the circumferential direction. Furthermore, the third groove root radius R1 is smaller than the second groove root radius R2.

[0051] In a further preferred embodiment of the present invention, the first groove root radius R3 satisfies R3 = 2 / 3(R4-R1) + R1, and the second groove root radius R2 satisfies R2 = 1 / 3(R4-R1) + R1, where radius R4 is the radius of the opening end of the spiral groove 3. By setting different groove root radii, a radially contracting structure of the spiral groove is achieved, thereby enhancing the blocking effect and pressure boosting effect of airflow at the groove root and improving the opening force of the air film seal. Specifically, when the airflow enters the spiral groove from the high-pressure side, upon encountering the first step 61 on the windward side, its larger groove depth and larger opening radius R4 result in a greater dynamic pressure loss and a smaller static pressure gain. After bypassing the first step 61, upon encountering the second step 62 on the leeward side, its smaller groove depth and smaller second groove root radius R2 result in a smaller dynamic pressure loss and a larger static pressure gain. After bypassing the second step 62, upon encountering the third step 63 on the windward side, its even smaller groove depth and smaller third groove root radius R1 result in a smaller dynamic pressure loss and a larger static pressure gain. Therefore, in each spiral groove, three contraction regions of varying degrees alternate on the windward and leeward sides, causing the airflow to be continuously compressed and blocked radially, forming a high-pressure region at the end of each contraction region.

[0052] In a further preferred embodiment of the present invention, the arc length at the inlet of the first step portion 61 is S3, the sum of the arc lengths at the inlet of the first step portion 61 and step portion I 71 is S2, and the sum of the arc lengths at the inlet of the first step portion 61, step portion I 71, and main step portion 80 is S1, wherein S2 = 0.75S1 and S3 = 0.5S1. The groove depth h2 of the second step portion 62 is the same as the groove depth H1 of step portion I 71, and the groove depth h3 of the third step portion 63 is the same as the groove depth H2 of step portion II 72 and the groove depth H0 of main step portion 80. In the three steps of the first spiral groove portion 6, the groove depth h1 is about 4-5 μm, the groove depth h2 is about 3-4 μm, and the groove depth h3 is about 2-3 μm. The ratio of the extension lengths of the three steps in the first spiral groove portion 6 is about 1:1:1, and the ratio of the extension lengths of the two steps in the second spiral groove portion 7 is about 2:1. By setting different groove depth and length ratios, a circumferentially contracting structure of the spiral groove is achieved, thereby enhancing the guiding and shearing effects of airflow at the opening end and reducing the leakage of the air film seal.

[0053] The working principle of the double-step contraction type spiral groove air film sealing structure of the present invention is as follows:

[0054] Structurally, this invention arranges spiral grooves circumferentially from the leeward side to the windward side, sequentially forming a first spiral groove portion 6, a second spiral groove portion 7, and a third spiral groove portion 8. The first spiral groove portion 6 is designed as a three-stage stepped contraction along its length from the radially outer side to the radially inner side, the second spiral groove portion 7 is designed as a two-stage stepped contraction along its length from the radially outer side to the radially inner side, and the third spiral groove portion 8 is designed as a single-stage stepped contraction along its length from the radially outer side to the radially inner side. As a result, the opening end of the spiral groove is formed as a three-stage stepped contraction along its circumferential side from the leeward side to the windward side. When airflow flows into the air-film sealed spiral groove 3 from the inlet, the rotation of the annular sealing end face will cause the airflow to rotate circumferentially. By setting a double-step contraction structure, the circumferential contact area between the airflow and the wall can be increased, and the shear effect can be better utilized to increase the fluid dynamic pressure and increase the circumferential velocity of the fluid in the groove area. Furthermore, the three-stage stepped inlet design effectively guides the inlet airflow and provides good constraint on the flowing fluid. Simultaneously, thanks to the contraction-type spiral groove structure, three stepped groove root regions—three blocking regions—are formed in the radial direction. This allows the airflow to be continuously compressed in the reverse direction along the radius, continuously blocking the airflow at the groove roots and promoting the conversion of fluid dynamic pressure into fluid static pressure. Therefore, a significant pressure increase occurs at the groove roots of the two stepped contraction-type small spiral grooves, thereby increasing the overall opening force of the gas film seal. Moreover, the strong blocking and shearing effects caused by the double-step contraction structure further reduce the radial outflow of the gas film seal, thus reducing leakage.

[0055] It can be seen that the double-step shrinkage spiral groove air film sealing structure of the present invention can bring the following benefits: (1) The two stepped shrinkage spiral grooves of the double-step shrinkage spiral groove of the present invention can effectively enhance the shear effect and blocking effect, thereby reducing the leakage; (2) The continuous radial shrinkage of the two stepped shrinkage spiral grooves at the root of the groove will have a significant pressure boosting effect, which will improve the opening force of the air film seal; (3) The three-stage stepped inlet setting can form a good guiding effect on the inlet airflow and form a good constraint on the flowing fluid; (4) From the definition of the stiffness-leakage ratio of the air film seal, it can be seen that it is equal to the ratio of leakage to air film stiffness. When the leakage of the air film seal decreases and the opening force increases, it will inevitably lead to an increase in the stiffness-leakage ratio, thereby improving the bearing capacity of the air film seal.

[0056] The above-mentioned double-step contraction spiral groove air film sealing structure of the present invention has passed the numerical simulation verification of air film sealing under different parameters, such as... Figure 6 , 7 As shown, Figure 6 The diagram shows a comparison of the radial pressure distribution of the double-step contraction spiral groove air film sealing structure of the present invention relative to the original structure (traditional stepless spiral groove air film sealing structure). Figure 7 The image shows a pressure cloud diagram comparison between the double-step contraction spiral groove air film sealing structure of the present invention and the traditional spiral groove structure. From... Figure 6 , 7 As can be seen, compared with the traditional spiral groove sealing structure, the radial pressure of the double-step contraction spiral groove structure of this invention is significantly increased, with maximum pressure increases of 39.9% and 49.3%, respectively. Furthermore, the leakage of the double-step contraction spiral groove structure is significantly reduced, the opening force is significantly increased, the stiffness-to-leakage ratio is significantly increased, and the distribution of the inlet low-pressure zone is significantly altered. Typical operating condition analysis shows that the average leakage is reduced by 3.7%, the opening force is increased by 16%, and the stiffness-to-leakage ratio is increased by 10.4%. At the same time, this structure is unique, has wide applicability, and is a promising new sealing structure.

[0057] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A double-step contraction type spiral groove gas film sealing structure, comprising at least one sealing ring that rotates during operation, wherein at least one end face of the sealing ring is formed as an annular sealing end face, the radially outer side of the annular sealing end face is the high-pressure gas side and the radially inner side is the low-pressure gas side, a plurality of spiral grooves are provided on the annular sealing end face along its circumference, the end face area between adjacent spiral grooves forms a sealing weir, and the end face area between the spiral grooves and the low-pressure gas side forms a sealing dam, characterized in that, Each spiral groove has a structure with one end open and the other end closed in the radial direction. Its open end extends radially outward to communicate with the high-pressure gas side and forms the air inlet of the spiral groove. Its closed end extends radially inward to the sealing dam and forms the groove root of the spiral groove. The two side walls of each spiral groove in the circumferential direction form its windward side and leeward side, respectively. The windward side faces the inlet gas entering the spiral groove, and the leeward side is opposite to the windward side. Each spiral groove spatially comprises a first spiral groove portion, a second spiral groove portion, and a third spiral groove portion arranged circumferentially from its leeward side to its windward side, and the three spiral groove portions extend radially from the opening end of the spiral groove to its root. The first spiral groove portion is arranged on the windward side adjacent to the spiral groove in the circumferential direction, and spatially includes a first step portion, a second step portion, and a third step portion arranged sequentially from the radial outer side to the radial inner side. The first step portion has a constant groove depth h1 along its length direction, the second step portion has a constant groove depth h2 along its length direction, and the third step portion has a constant groove depth h3 along its length direction, wherein the groove depth h1 > groove depth h2 > groove depth h3, so that the first spiral groove portion is formed as a three-stage stepped contraction shape from the radial outer side to the radial inner side along its length direction. The second spiral groove portion is located circumferentially between the first spiral groove portion and the third spiral groove portion, and spatially includes a stepped portion I and a stepped portion II arranged sequentially from the radially outer side to the radially inner side. The stepped portion I has a constant groove depth H1 along its length direction, and the stepped portion II has a constant groove depth H2 along its length direction, wherein the groove depth H1 > the groove depth H2, so that the second spiral groove portion is formed as a two-stage stepped contraction shape along its length direction from the radially outer side to the radially inner side. The third spiral groove portion is arranged on the leeward side of the spiral groove in the circumferential direction, and includes a main stepped portion extending from the radially outer side to the radially inner side in space, the main stepped portion having a constant groove depth H0 along its length direction; Furthermore, the opening end of each spiral groove includes a first step portion located in the first spiral groove portion, a step portion I located in the second spiral groove portion, and a main step portion located in the third spiral groove portion. The groove depth H1 of the step portion I is greater than the groove depth h1 of the first step portion and the groove depth H0 of the main step portion, so that the opening end of the spiral groove is formed in a three-stage stepped contraction shape along the circumferential direction from the leeward side to the windward side. Furthermore, the sum of the extension lengths of the first step portion and the second step portion in the first spiral groove portion is equal to the extension length of the step portion I in the second spiral groove portion, and the arc-shaped groove roots of the second step portion and the step portion I in the second spiral groove portion have the same second groove root radius R2 and are continuously integrated in the circumferential direction, and the second groove root radius R2 is smaller than the first groove root radius R3 of the arc-shaped groove root of the first step portion in the first spiral groove portion; The sum of the extension lengths of the three steps in the first spiral groove section is equal to the sum of the extension lengths of the two steps in the second spiral groove section and the extension length of the main step in the third spiral groove section. The arc-shaped groove roots of the third step in the first spiral groove section, the step II in the second spiral groove section and the main step in the third spiral groove section have the same third groove root radius R1 and are continuous in the circumferential direction. The third groove root radius R1 is smaller than the second groove root radius R2. The first groove root radius R3 satisfies R3=2 / 3(R4-R1)+R1, and the second groove root radius R2 satisfies R2=1 / 3(R4-R1)+R1, where the radius R4 is the radius of the opening end of the spiral groove; The arc length at the entrance of the first step is S3, the sum of the arc lengths at the entrances of the first step and step I is S2, and the sum of the arc lengths at the entrances of the first step, step I, and main step is S1, where S2 = 0.75S1 and S3 = 0.5S1.

2. The double-staged converging spiral groove gas film seal structure according to claim 1, wherein, The groove depth h2 of the second step is the same as the groove depth H1 of step I, and the groove depth h3 of the third step is the same as the groove depth H2 of step II and the groove depth H0 of the main step. In the three steps of the first spiral groove, the groove depth h1 is 4~5 μm, the groove depth h2 is 3~4 μm, and the groove depth h3 is 2~3 μm.

3. The double-staged converging spiral groove gas film seal structure according to claim 1, wherein, The ratio of the extension lengths of the three steps in the first spiral groove is 1:1:1, and the ratio of the extension lengths of the two steps in the second spiral groove is 2:

1.

4. The double-staged converging spiral groove gas film seal structure according to claim 1, wherein, By flexibly adjusting the groove depth of the three stepped sections in the first spiral groove section and the two stepped sections in the second spiral groove section, the pressure-boosting effect of the spiral groove and the distribution of the inlet low-pressure zone can be adjusted, thereby reducing the leakage of the gas film seal and improving the rigid-leakage ratio of the gas film seal.

5. The double-staged converging spiral groove gas film seal structure according to claim 1, wherein, The annular sealing end face is provided with several micro-grooves, which are distributed on the sealing weir and connected to the high-pressure fluid side to increase the circumferential contact area between the airflow and the sealing weir, thereby enhancing the shearing effect and pressure boosting effect.

6. The double-staged converging spiral groove gas film seal structure according to claim 1, wherein, A plurality of annular micro-partitions are provided on the annular sealing end face. The annular micro-partitions are distributed on the sealing dam and are connected to the low-pressure fluid side to reduce the circumferential contact area between the airflow and the sealing dam, thereby reducing the leakage and the stiffness-to-leakage ratio.

7. The double-staged converging spiral groove gas film seal structure according to claim 1, wherein, Micro-recesses are distributed on the three steps in the first spiral groove section and the two steps in the second spiral groove section to increase the contact area between the airflow and each step section, thereby enhancing the shearing effect and pressure boosting effect.

8. An aircraft engine compressor bearing cavity seal structure, characterized by, The sealing structure is provided with the double-step shrinkage spiral groove air film sealing structure as described in any one of claims 1 to 7.

Images