A hole-type damping seal structure with dovetail guide groove

Abstract

A cylindrical hole-shaped damping seal structure with a dovetail-type guide groove comprises a sealing shell, a sealing liner and a hollow sealing hole with a dovetail-type guide groove. The sealing liner is processed with a number of hollow sealing holes with dovetail-type guide grooves arranged regularly. The dovetail-type guide grooves are composed of dovetail-shaped grooves symmetrically distributed on both sides of the downstream of the hollow sealing hole along the sealing axis direction, and are not connected to the adjacent hollow sealing holes downstream; the sealing liner is inserted into the sealing shell and fixed with the sealing shell to form a damping seal. The present invention utilizes the interference between the holes in the cylindrical annular porous seal, and at the outlet of the hollow sealing hole with a dovetail-type guide groove, the fluid flowing out of the cavity of the hollow sealing hole changes from the flow direction of the pressure drop along the axis to the flow direction at a certain inclination angle to the axis direction, thereby forming a turbulent vortex in the cavity of the adjacent hollow sealing hole downstream, and forming a local low-speed zone on the cross section of the sealing gap area here, thereby reducing the gas leakage.

Description

Technical Field

[0001] The invention relates to a hole-type damping seal with a dovetail guide groove, which is suitable for shaft ends and interstage sealing devices of large turbine machinery such as various gas turbines, steam turbines, compressors, etc., and belongs to the technical field of cylindrical non-contact fluid sealing. Background Art

[0002] Deep hole damping seals are mainly used to seal gas media and are widely used in interstage seals, shaft end seals and blade tip seals in rotating machinery such as steam turbines, gas turbines, centrifugal compressors, and aircraft engines, or in pre-seals of other dynamic seals. Advanced honeycomb seals or deep hole damping seals have considerable improvements in leakage characteristics and damping characteristics compared to traditional labyrinth seals, which can effectively reduce the seal leakage rate and increase effective damping. Compared with honeycomb seals, hole-type damping seals are mostly made of aluminum alloy materials. The hole processing is simpler than honeycomb seals, and the hole shape processing is more diverse. The leakage prevention mechanism of hole-type damping seals is as follows: After the gap fluid flows into the sealing gap, it is divided into two main parts. One part of the fluid enters the hole for vortex dissipation, which has the effect of throttling and reducing pressure, and the other part flows to the low-pressure side at high speed close to the rotor wall, increasing the leakage of the seal. Compared with labyrinth seals, hole-type damping seals can effectively suppress the circumferential flow of gas, so they have a higher damping effect. However, the fluid in the sealing gap that does not enter the hole cavity still flows around the rotor in a spiral line. The unsteady airflow excitation force generated in the sealing chamber induces the instability of the sealed rotor, reducing the stability of the unit. In order to improve the above problems of traditional hole-type damping seals, researchers have proposed bag-type damping seals (Li Jun, Li Zhigang. Research progress on leakage flow and rotor dynamic characteristics of bag-type damping seals. Progress in Mechanics, 2011, 41(5): 519-536), a method of using damping seals and labyrinth seals in series (US20060267289A1: Hybrid abradable labyrinth damper seal), and tapered cylindrical honeycomb rough texture damping seals (IKEDA T, SAITO T, ITO S. Experimental study on static and dynamic characteristics of liquid annular convergent-tapered damper seals with honeycomb roughness pattern [J]. ASME Journal of Tribology, 2003, 125(3): 592-599.) and tapered gap hole type damping seal (Sun Dan, Li Shengyuan, Xiao Zhonghui, et al. Dynamic characteristics analysis and vibration suppression mechanism of tapered gap hole type damping seal [J]. Journal of Aerospace Power, 2018, 33(7): 1544-1552.) However, the effect is not significant due to the complex structure, strong influence of external factors and operating conditions, and heavy reliance on the accurate installation of the seal. The purpose of suppressing the spiral flow of the fluid along the rotating shaft has not been achieved. Summary of the invention

[0003] The present invention aims to overcome the above-mentioned disadvantages of the prior art and provides a hole-type damping sealing structure with a dovetail guide groove.

[0004] The present invention is based on bionic design theory and bionic engineering principles. Based on a large amount of research, the present invention processes a dovetail-shaped guide groove at the air flow outlet of the hollow sealing cavity, that is, on the downstream side of the leakage air flow, and changes the direction of gas flowing out of the cavity, thereby reducing the sealing leakage rate and improving the leakage resistance and dynamic characteristics of the seal.

[0005] The present invention processes a dovetail-shaped guide groove at the air flow outlet of the sealing cavity, that is, the downstream side of the leakage air flow, to control the direction of fluid flowing out of the cavity to always form a certain angle with the axis of the rotating shaft, strengthen the interference between the holes in the cylindrical porous damping seal, and form two turbulent low-speed vortices in the cavity, thereby effectively reducing the leakage loss of the unit, inhibiting the flow of the spiral fluid along the rotating shaft in the gap, and improving the operating efficiency of the unit.

[0006] The following technical solutions are implemented:

[0007] The present invention provides a hole-type damping sealing structure with a dovetail guide groove, comprising a cylindrical sealing shell 2, a sealing liner 1 being arranged on the inner wall of the sealing shell 2, a plurality of regularly arranged hollow sealing holes being distributed on the sealing liner 1, and the axis of the hollow sealing hole being parallel to the central axis of the sealing shell 2, characterized in that: the hollow sealing hole 1 is provided with two guide grooves 3-2 symmetrically distributed along the axis on the air flow outlet side of the cavity on the basis of a traditional circular shape, and the overall shape of the guide groove 3-2 is dovetail-shaped; and two adjacent rows of hollow sealing holes 3 are staggered along the axial direction.

[0008] The hollow sealing hole main cavity 3-1 is used to dissipate the energy of the leaking fluid, and the outlet dovetail guide groove 3-2 can change the direction of the fluid entering the next axial cavity. The sealing liner 1 processed with the hollow sealing hole 3 is inserted into the sealing shell 2 and fixed thereto to form a sealing body. The present invention utilizes the interference between the holes in the porous annular seal, and processes the dovetail guide groove 3-2 at the outlet of the hollow sealing hole, so that the direction of the fluid flowing out of the cavity is changed from the pressure drop direction to a direction with a certain inclination angle to the axial direction, thereby forming a turbulent vortex in the next adjacent cavity, and forming a local low-speed zone on the cross section of the corresponding sealing gap, thereby reducing the leakage gas flow of the seal.

[0009] The hole type parameters of the hole type damping seal structure of the dovetail guide groove are defined as follows: θ is the distance between two holes in the same row in the axial direction, l z is the circumferential spacing between two adjacent rows of holes, l θ1 is the axial spacing between two adjacent rows of holes in the circumferential direction, R1 is defined as the radius of the axial spacing circle, and its value is determined by the axial spacing lθ Other basic parameters of the hole type are that the radius of the hollow sealing hole main cavity 3-1 is r, the outer contour radius of the dovetail guide groove 3-2 is R, the angle between the center line of the dovetail guide groove 3-2 and the sealing axis is the axial inclination angle β, and the dovetail guide groove 3-2 groove tip extension ratio is e, e = (Rr) / (R1-R) (such as Figure 4 ).

[0010] Furthermore, the main body cavity of the hollow sealing hole 3 is a through hole, and its cross-sectional shape is hexagonal, circular, triangular, etc.

[0011] Furthermore, the dovetail guide groove 3-2 is a through groove, and its shape is triangular or semi-leaf, wherein the wide end is connected to the main cavity 3-1 of the hollow sealing hole, and the narrow end corner is not connected to the next hollow sealing hole.

[0012] Furthermore, the hole-type damping seal structure with a dovetail guide groove is characterized in that the optimal axial inclination angle β is 40 to 60°, and the optimal range of the extension ratio e is 0.8<e<1.

[0013] The working principle of the present invention is:

[0014] The purpose of the present invention is to improve a new type of hole-type damping seal that can artificially change the direction of fluid flowing out of the hole cavity, thereby increasing the vortex dissipation intensity in the hole cavity and reducing the leakage gas flow of the seal. The new type of sealing hole is based on the traditional circular shape and has two symmetrically distributed dovetail guide grooves along the axis at the air flow outlet of the hole cavity. In order to facilitate the processing of the new type of hole cavity with dovetail guide grooves on the stator surface, the sealing structure adopts a layered structure. First, the hole cavity is hollowed out on the sealing liner using a CNC machining method, and then it is expanded together with the sealing shell or the sealing liner and the sealing shell are locked with screws, thereby forming a damping seal main structure.

[0015] After the fluid flows into the sealing gap, part of it enters the main cavity for vortex dissipation. Due to the flow-guiding effect of the dovetail groove, the fluid flowing out of the cavity will flow into the next cavity at a certain axial inclination angle. The fluid flowing in obliquely forms two turbulent dissipation vortices in the cavity, and two low-speed zones are formed at the sealing gap corresponding to the cavity. The existence of this low-speed zone can reduce the sealing leakage on the one hand, and effectively inhibit the flow of the gap jet along the spiral line of the rotating shaft on the other hand, thereby improving the dynamic characteristics of the seal.

[0016] The advantages and beneficial effects of the present invention are:

[0017] The present invention has the following effects:

[0018] (1) The processing of the new circular hole damping seal is relatively simple, and the existence of the dovetail guide groove can reduce the leakage of the seal and effectively reduce the leakage loss of the unit. Studies have shown that compared with circular hole damping seals with the same opening area, the maximum leakage rate can be reduced by about 20%.

[0019] (2) The low-speed vortex in the hole of the new hole-type damping seal with dovetail guide groove can extend to the sealing gap and form several local low-speed zones in the corresponding sealing gap. The existence of the low-speed zone can effectively inhibit the flow of the gap jet along the spiral line of the rotating shaft, thereby improving the dynamic characteristics of the seal and improving the sealing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a layered structural diagram of a hole-type damping sealing structure with a dovetail guide groove of the present invention.

[0021] Figure 2 It is a structural diagram of the sealing liner of the present invention.

[0022] Figure 3a It is a partial enlarged view of the hollow sealing cavity with dovetail guide groove of the present invention. Figure 3b yes Figure 3a A partial enlarged view of .

[0023] Figure 4 It is a schematic diagram of the distribution of adjacent sealing holes with dovetail guide grooves of the present invention.

[0024] Figure 5a 1 is a schematic diagram of a hole-type damping seal interference-fitting structure with a dovetail guide groove according to an embodiment of the present invention. Figure 5b yes Figure 5a A schematic diagram of another angle of the structure shown.

[0025] Figure 6 It is a schematic diagram of a screw fixing structure between hole-type damping seal layers with a dovetail guide groove according to another embodiment of the present invention.

[0026] The parts numbers in the figure are: sealing liner 1, sealing shell 2, sealing shell left baffle 2-1, sealing shell right baffle 2-2, hollow sealing hole 3, hollow sealing hole main cavity 3-1, dovetail guide groove 3-2, installation push ear 3-3, locking screw 4. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described in detail with reference to the accompanying drawings:

[0028] Embodiment 1:

[0029] Reference Figure 1 to Figure 5b :

[0030] The present invention provides a hole-type damping seal interference-fitting structure with a dovetail guide groove, comprising a cylindrical sealing shell 2, the inner wall of which is provided with a sealing liner 1, on which are distributed a plurality of regularly arranged hollow sealing holes, the axis of the hollow sealing hole being parallel to the central axis of the sealing shell 2, and the hollow sealing hole being provided with two dovetail guide grooves 3-2 symmetrically distributed along the axis at the airflow outlet of the cavity on the basis of a traditional circular shape.

[0031] The air flow direction is along the axis direction.

[0032] The hollow sealing hole main cavity 3-1 is used to dissipate the energy of the leaking fluid, and the outlet dovetail guide groove 3-2 can change the direction of the fluid entering the next axial cavity. The sealing liner 1 processed with the hollow sealing hole 3 is inserted into the sealing shell 2 with interference fit, and the sealing liner and the sealing shell baffles 2-1 and 2-2 are fixed with the locking screws 4 on both sides to form a sealing body. When disassembly is required, the locking screws 4 on both sides need to be removed, and the inner sealing liner 1 is taken out. The present invention utilizes the interference effect between the holes in the porous annular seal, and processes the dovetail guide groove 3-2 at the outlet of the hollow sealing hole, so that the direction of the fluid flowing out of the cavity is changed from the pressure drop direction to the direction with a certain inclination angle to the axial direction, thereby forming a turbulent vortex in the next adjacent cavity, and forming a local low-speed zone on the cross section of the corresponding sealing gap, thereby reducing the leakage gas flow of the seal. The hole type damping seal hole type parameters of the dovetail guide groove are defined as follows: l θ is the distance between two holes in the same row in the axial direction, l z is the circumferential spacing between two adjacent rows of holes, l θ1 is the axial spacing between two adjacent rows of holes in the circumferential direction, R1 is defined as the radius of the axial spacing circle, and its value is determined by the axial spacing l θ Other basic parameters of the hole type are that the radius of the hollow sealing hole main cavity 3-1 is r, the radius of the dovetail guide groove 3-2 is R, the angle between the center line of the dovetail guide groove 3-2 and the sealing axis is the axial inclination angle β, and the dovetail guide groove 3-2 groove tip extension ratio is e, e = (Rr) / (R1-R) (such as Figure 4 ).

[0033] The main body cavity of the hollow sealing hole 3 is a through hole, and its cross-sectional shape can be hexagonal, circular, triangular, etc., and two adjacent rows of hollow sealing holes 3 are arranged alternately along the axial direction.

[0034] The dovetail guide groove 3-2 is a through groove, and its shape is triangular or semi-leaf, wherein the wide end is connected to the main cavity 3-1 of the hollow sealing hole, and the narrow end corner is not connected to the next hollow sealing hole.

[0035] The hole-type damping seal structure with a dovetail guide groove has a characteristic optimal axial inclination angle β of the dovetail guide groove in the range of 40 to 60 degrees, and an optimal range of the extension ratio e is 0.8<e<1.

[0036] The hole-type damping seal interference-fitting structure with a dovetail guide groove can be processed into a petal-type structure for axial sealing of large-diameter rotating machinery, or can be processed into an integral structure for small-diameter rotating sealing.

[0037] Embodiment 2:

[0038] Reference Figures 1 to 4 , Figure 6 :

[0039] In the second embodiment, a hole-type damping seal interlayer screw fixing structure with a dovetail guide groove is provided. Its structure is basically the same as the new hole-type damping seal in the first embodiment, and the main difference is the different installation method of the liner. Figure 6 , a T-shaped groove 2-3 is opened on the inner side of the sealing shell, and a left baffle 2-1 is provided at one axial end of the shell, and no baffle is provided at the other end. A T-shaped boss is also processed at the corresponding position on the outer side of the sealing liner 3, and a mounting push ear 3-3 is processed at one axial end. During the specific installation, the sealing liner 3 is pushed into the sealing shell along the T-shaped boss and locked, and then the locking screw is passed through the mounting push ear 3-3 at one end of the liner to lock it with the sealing shell 2. When the seal needs to be disassembled, the locking screw 4 on one side needs to be removed, and then the inner sealing liner 1 needs to be taken out.

[0040] The contents described in the embodiments of this specification are merely an enumeration of implementation forms of the inventive concept. The protection scope of the present invention should not be deemed to be limited to the specific forms described in the embodiments. The protection scope of the present 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 hole-type damping seal structure with a dovetail guide groove, comprising a cylindrical sealing shell (2), the inner wall of the sealing shell (2) is provided with a sealing liner (1), a plurality of regularly arranged hollow sealing holes are distributed on the sealing liner (1), and the axis of the hollow sealing hole is parallel to the central axis of the sealing shell (2), characterized in that: The hollow sealing hole (1) is provided with two guide grooves (3-2) symmetrically distributed along the axis on the air flow outlet side of the cavity on the basis of a traditional circular shape, and the overall appearance of the guide grooves (3-2) is dovetail-shaped; two adjacent rows of hollow sealing holes (3) along the axial direction are staggered.

2. The hole-type damping seal structure with dovetail guide groove according to claim 1, characterized in that: The hole parameters are defined as follows: θ is the distance between two holes in the same row in the axial direction, l z is the circumferential spacing between two adjacent rows of holes, l θ1 is the axial spacing between two adjacent rows of holes in the circumferential direction, R1 is defined as the radius of the axial spacing circle, and its value is determined by the axial spacing l θ The other basic parameters of the hole type are as follows: the radius of the hollow sealing hole main cavity (3-1) is r, the outer contour radius of the dovetail guide groove (3-2) is R, the angle between the center line of the dovetail guide groove (3-2) and the sealing axis is the axial inclination angle β, and the groove tip extension ratio of the dovetail guide groove (3-2) is e, e=(Rr) / (R1-R).

3. A hole-type damping seal structure with a dovetail guide groove according to claim 1, characterized in that: The main body cavity of the hollow sealing hole (3) is a through hole, and its cross-sectional shape is one of a hexagon, a circle, and a triangle.

4. A hole-type damping seal structure with a dovetail guide groove according to claim 2, characterized in that: The dovetail-shaped guide groove (3-2) is a through groove, and its shape is triangular or semi-leaf-shaped, wherein the wide end is connected to and through the main cavity (3-1) of the hollow sealing hole, and the top angle of the narrow end is not connected to the next hollow sealing hole.

5. The hole-type damping seal structure with dovetail guide groove according to claim 3, characterized in that: The optimal axial inclination angle β of the dovetail guide groove is 40-60°, and the optimal range of the extension ratio e is 0.

8. <e<1。

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