Lap joint type cylindrical surface gas film sealing structure imitating laval nozzle groove shape

Abstract

The invention discloses a lap joint type cylindrical surface gas film sealing structure simulating a laval nozzle groove shape, which comprises a sealing base body, two sealing side baffles, a laval nozzle type splicing block, a fixing bolt, an O-shaped sealing ring and a sealing surface, splicing block mounting grooves, dehumidification water conveying grooves and dehumidification liquid discharging holes which are evenly distributed in the circumferential direction are machined in the inner side of the sealing base body, and the splicing block mounting grooves, the dehumidification water conveying grooves and the dehumidification liquid discharging holes are axially communicated with the sealing base body. According to the lap joint type cylindrical surface air film sealing structure simulating the laval nozzle groove shape, a novel structural design is adopted, sealing teeth of a traditional labyrinth seal are changed into the laval nozzle groove shape, the groove shape can remarkably change the fluid movement path, the circumferential speed of fluid in the groove is increased when the fluid passes through channel fluid of the contraction section and the expansion section, and the sealing effect is improved. The energy dissipation and the axial total pressure drop of the fluid in a circumferential channel are increased, and the sealing leakage rate is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of cylindrical non-contact fluid sealing, in particular to an overlapped Laval nozzle groove-like cylindrical air film sealing structure. Background Art

[0002] The non-contact cylindrical gas film seal technology plays an important role in the energy saving and efficiency improvement of steam turbine mechanical seals in the field of power equipment in my country. Improving the steam state and leakage of steam turbine mechanical seals is an effective measure to improve the economic and reliability of unit operation.

[0003] In the prior art, more advanced honeycomb seals and hole-type damping seals are usually used to replace traditional labyrinth seals (labyrinth seals use a series of regular labyrinth structures with axial and radial gaps to expand and throttle the leaked fluid multiple times, thereby achieving the purpose of reducing leakage). Compared with labyrinth seals, honeycomb seals and hole-type damping seals have better damping characteristics. Moreover, due to the large surface area of ​​the regularly arranged core cells, the fluid forms a condensation effect due to the pressure reduction and temperature drop when passing through the cavity. The condensed and separated droplets will adhere to the wall of the cavity, reducing the humidity of the leaked gas and achieving the effect of dehumidification.

[0004] As in the prior art, a Chinese patent with publication number CN218408526U discloses a cylindrical air film seal flexible support structure with metal rubber and spiral grooves, which belongs to the field of non-contact mechanical seal technology. It includes a dynamic ring rotor, a floating static ring, a pressure block, an elastic foil, a metal rubber and an outer support sleeve. A dynamic pressure sealing area is formed between the journal of the dynamic ring rotor and the inner wall of the floating static ring, and the two sides of the floating static ring are respectively a high-pressure area and a low-pressure area; there are multiple elastic foil supports distributed circumferentially around the floating static ring, and the elastic support structure includes metal rubber and elastic foil superimposed supports, and the tail end of the elastic support structure is fixed to the outer support sleeve through a pressure block.

[0005] As another example in the prior art, a Chinese patent with publication number CN113775763A discloses a variable-depth split-petal airbag support hole-type damping seal, comprising a cylindrical sealing shell, an inner wall of which is provided with a damping sealing layer, and an end of the sealing shell is provided with a shell end cover; an annular liner is provided on the inner side of the damping sealing layer, and a hole depth adjustment layer and an airbag layer are provided on the outer side of the annular liner in sequence; the circumferential sealing ring surface formed by the annular liner has the same axis as the smooth rotating shaft; a plurality of hollow damping holes are provided on the annular liner, and a plurality of hole depth adjustment plugs are provided on the hole depth adjustment layer, and the inner sides of the hole depth adjustment plugs are inserted into the hollow damping holes; the outer sides of the hole depth adjustment plugs are connected to the high-pressure air source of the airbag layer, and the inner sides of the hole depth adjustment plugs can be flush with the inner mouths of the hollow damping holes.

[0006] The cylindrical air film sealing structure in the prior art is as described in the above materials. In order to avoid the friction between the conventional hole type and honeycomb seal and the rotating shaft during production, the designed sealing gap is at least above the sub-millimeter level. The leakage volume always accounts for a large part of the leakage loss, and the dehumidification effect is still unsatisfactory to a certain extent. In the working environment of the steam turbine machinery with a relatively high humidity content in the working fluid, the blades will still inevitably experience water erosion, which may lead to blade breakage accidents. The current cavity shape of the conventional non-contact cylindrical air film seal still has a lot of room for improvement. In addition, since the conventional non-contact cylindrical air film seal liner is inseparable in its overall structure, if part of the seal fails, the entire thing must be scrapped, the cost of use is high, and the service life is not long. Summary of the invention

[0007] The object of the present invention is to provide an overlapping Laval nozzle groove-like cylindrical air film sealing structure to solve the problem of blade erosion and overall scrapping that increases costs mentioned in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a lapped Laval nozzle groove-like cylindrical air film sealing structure, comprising a sealing base, baffles on both sides of the seal, a Laval nozzle type splicing block, fixing bolts, an O-ring and a sealing surface, and also comprising:

[0009] The sealing base is annular in structure as a whole, and the inner side of the sealing base is processed with splicing block installation grooves, dehumidification water delivery grooves and dehumidification drainage holes that are evenly arranged in the circumferential direction, and the splicing block installation grooves, dehumidification water delivery grooves and dehumidification drainage holes are all axially connected with the sealing base;

[0010] The sealing base body is provided with an annular sealing ring installation sealing groove on the side thereof, and an O-type sealing ring is embedded and installed inside the annular sealing ring installation sealing groove;

[0011] The Laval nozzle type splicing block is spliced ​​into a ring structure, and a splicing block bottom slide rail is arranged on the outside of the Laval nozzle type splicing block, and the splicing block bottom slide rail is matched with the splicing block installation groove to slide into the installation;

[0012] The inner side of the Laval nozzle type splicing block is processed with a splicing block contraction section curved surface and a splicing block expansion section curved surface;

[0013] The Laval nozzle type splicing blocks are connected to each other to form a sealing surface, and sealing baffles are arranged on the left and right sides of the sealing surface.

[0014] Preferably, baffle threaded holes are provided at equal intervals on the edge positions of the baffles on both sides of the seal, and the baffle threaded holes correspond to the base threaded holes provided on the side surfaces of the seal base.

[0015] Preferably, fixing bolts threadedly connected thereto are inserted into the threaded holes of the base and the baffles, and O-rings are squeezed after the baffles on both sides of the seal are fixed.

[0016] Preferably, the curve at the contraction section surface of the splicing block is designed according to the Witoshinsky curve, Batchelor-Shaw method, bicubic curve and quintic curve formula.

[0017] Preferably, the ratio of the inlet radius R1 to the throat radius R2 of the curved surface of the contraction section of the splicing block is less than 0.7.

[0018] Preferably, the curved surface of the expansion section of the splicing block is designed according to the characteristic line method, the Foulkes method and the design method of equal slope expansion.

[0019] Preferably, the ratio between the throat radius r2 and the outlet radius r1 of the curved surface of the expansion section of the splicing block is less than 0.7.

[0020] Preferably, the circumferential arrangement number N1 of the Laval nozzle type splicing blocks is ≥6, and the axial arrangement number N2 of the Laval nozzle type splicing blocks is ≥2.

[0021] Preferably, the curved surface of the contraction section of the splicing block and the curved surface of the expansion section of the splicing block are arranged as a symmetrical structure.

[0022] Compared with the prior art, the beneficial effects of the present invention are: the overlapping cylindrical air film sealing structure of the Laval nozzle-like groove adopts a new structural design. The present invention changes the sealing teeth of the traditional labyrinth seal into a Laval nozzle-like groove. The groove can significantly change the fluid movement path, and accelerate the circumferential velocity of the fluid in the groove when the fluid passes through the contraction section and expansion section channel fluid, increase the energy dissipation of the fluid in the circumferential channel and the total axial pressure drop, and reduce the sealing leakage. In addition, when the humid gas flows through the Laval nozzle-like groove, adiabatic expansion occurs, the working fluid temperature decreases, the wet vapor is prone to condensation phase change and condenses into droplets, and the generated droplets can be discharged through the drainage holes and dehumidification drainage holes of the sealing substrate, effectively reducing the humidity of the working fluid. The specific contents are as follows:

[0023] 1. The Laval nozzle-shaped curved surface of the novel sealing structure proposed in the present invention is formed by embedding the Laval nozzle-shaped splicing block into the sealing matrix and overlapping it. Its unique Laval nozzle-shaped curved surface structure can effectively enhance the energy dissipation of the fluid, reduce the leakage loss of the unit, and improve the operating efficiency of the unit;

[0024] Furthermore, after the sealing liner and the rotating shaft collide and scratch, only the partially failed Laval nozzle-type splicing block can be replaced instead of replacing the entire sealing structure to restore its sealing performance, so that the sealing structure is more convenient to repair.

[0025] 2. The new sealed Laval nozzle curved surface structure and its supporting structure proposed in the present invention have the functions of liquid intake, liquid collection and liquid discharge, which can significantly reduce the moisture content in the working fluid, effectively reduce the erosion of water droplets on the blades, improve the safety of turbine blades, and reduce the possibility of water erosion failure of turbine blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall cross-sectional layered structure of the present invention;

[0027] Figure 2 It is a schematic diagram of the layered structure of the three-dimensional structure section of the sealing substrate of the present invention;

[0028] Figure 3 This is a schematic diagram of the assembly structure of the Laval nozzle-shaped splicing block and the sealing base of the present invention;

[0029] Figure 4 This is a schematic diagram of the three-dimensional structure of the baffles on both sides of the seal of the present invention;

[0030] Figure 5 This is a schematic diagram of the three-dimensional structure of the Laval nozzle-shaped splicing block of the present invention;

[0031] Figure 6 This is a schematic diagram of the layered structure of the sealed structure section of the second embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram of the structure of a sealed special-shaped Laval nozzle type splicing block according to the second embodiment of the present invention.

[0033] In the figure: 1. Sealing base; 1-1. Base threaded hole; 1-2. Annular sealing ring installation sealing groove; 1-3. Joint block installation groove; 1-4. Dehumidification water supply groove; 1-5. Dehumidification drainage hole; 2. Sealing baffles on both sides; 2-1. Baffle threaded hole; 3. Laval nozzle type joint block; 3-1. Joint block bottom slide rail; 3-2. Joint block contraction section curved surface; 3-3. Joint block expansion section curved surface; 4. Fixing bolt; 5. O-ring; 6. Sealing surface. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1: Please refer to Figure 1-Figure 5The present invention provides a technical solution: a lap-jointed Laval nozzle groove-like cylindrical air film sealing structure, comprising a sealing base 1, baffles 2 on both sides of the seal, a Laval nozzle type splicing block 3, fixing bolts 4, an O-ring 5 and a sealing surface 6, the sealing base 1 is annular in structure as a whole, and the inner side of the sealing base 1 is processed with splicing block mounting grooves 1-3, dehumidification water delivery grooves 1-4 and dehumidification drainage holes 1-5 that are evenly arranged in the circumferential direction, and the splicing block mounting grooves 1-3, dehumidification water delivery grooves 1-4 and dehumidification drainage holes 1-5 are all axially connected with the sealing base 1, and the side of the sealing base 1 is provided with an annular sealing The sealing ring is installed in the sealing groove 1-2, and an O-ring 5 is embedded and installed inside the annular sealing ring installation sealing groove 1-2. The Laval nozzle type splicing block 3 is spliced ​​into a ring structure, and a splicing block bottom slide rail 3-1 is arranged on the outside of the Laval nozzle type splicing block 3, and the splicing block bottom slide rail 3-1 is matched and slid into the splicing block installation groove 1-3. The inside of the Laval nozzle type splicing block 3 is processed with a splicing block contraction section curved surface 3-2 and a splicing block expansion section curved surface 3-3. The Laval nozzle type splicing blocks 3 are mutually connected to form a sealing surface 6, and sealing side baffles 2 are arranged on the left and right sides of the sealing surface 6.

[0036] The edge positions of the baffle plates 2 on both sides of the seal are provided with baffle plate threaded holes 2-1 with equal spacing, and the baffle plate threaded holes 2-1 correspond to the base body threaded holes 1-1 opened on the side of the sealing base body 1, and the base body threaded holes 1-1 and the baffle plate threaded holes 2-1 are penetrated with fixing bolts 4 threadedly connected thereto, and the baffle plates 2 on both sides of the seal are fixed and squeezed with O-rings 5, and the curve at the contraction section surface 3-2 of the splicing block is calculated according to the Witosinski curve, the Batchelor-Shaw method, and the bicubic curve. The ratio of the inlet radius R1 to the throat radius R2 of the contraction section surface 3-2 of the splicing block is less than 0.7. The expansion section surface 3-3 of the splicing block is designed according to the characteristic line method, the Fuerst method and the design method of equal slope expansion. The ratio of the throat radius r2 to the outlet radius r1 of the expansion section surface 3-3 of the splicing block is less than 0.7. The circumferential arrangement number N1 of the Laval nozzle type splicing block 3 is ≥6, and the axial arrangement number N2 of the Laval nozzle type splicing block 3 is ≥2.

[0037] The Laval nozzle-type curved surface formed by the closely arranged Laval nozzle-type splicing blocks 3 can effectively change the axial motion component of the fluid, increase energy dissipation, and reduce leakage. The gas velocity increases and the pressure decreases on the splicing block contraction section curved surface 3-2; the velocity decreases on the splicing block expansion section curved surface 3-3, forming a shock wave, separating the gas and condensing water vapor, and discharging condensed water through the dehumidification water delivery trough 1-4 and the dehumidification drainage hole 1-5, thereby reducing the humidity of the working medium;

[0038] Since the Laval nozzle type splicing block 3 is a splicing structure, after the sealing liner and the rotating shaft collide and scratch, only the Laval nozzle type splicing block 3 that may fail locally can be replaced instead of replacing the entire sealing structure to restore its sealing performance, so the sealing structure is more convenient to repair.

[0039] Embodiment 2: The structure provided in this embodiment is basically the same as the novel damping seal in Embodiment 1, the main difference being the design of the expansion section of the Laval nozzle type splicing block. Figure 6 and Figure 7 As shown, the design of the splicing block expansion section surface 3-3 is the same as the splicing block contraction section surface 3-2. Compared with the implementation case 1, this design method has a balanced ratio between the contraction section and the expansion section, is easy to process, and is more suitable for some high-speed turbine machinery shaft ends with smaller shaft diameters. The splicing block contraction section surface 3-2 and the splicing block expansion section surface 3-3 are set to a symmetrical structure.

[0040] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lapped Laval nozzle groove-like cylindrical air film sealing structure, comprising a sealing base (1), baffles (2) on both sides of the seal, a Laval nozzle type splicing block (3), fixing bolts (4), an O-ring (5) and a sealing surface (6), characterized in that: Also includes: The sealing base (1) is annular in structure as a whole, and the inner side of the sealing base (1) is processed with splicing block installation grooves (1-3), dehumidification water delivery grooves (1-4) and dehumidification drainage holes (1-5) which are evenly arranged in the circumferential direction, and the splicing block installation grooves (1-3), dehumidification water delivery grooves (1-4) and dehumidification drainage holes (1-5) are all axially connected to the sealing base (1); An annular sealing ring installation sealing groove (1-2) is provided on the side of the sealing base (1), and an O-type sealing ring (5) is embedded and installed inside the annular sealing ring installation sealing groove (1-2); The Laval nozzle type splicing block (3) is spliced ​​into a ring structure, and a splicing block bottom slide rail (3-1) is arranged on the outside of the Laval nozzle type splicing block (3), and the splicing block bottom slide rail (3-1) is matched with the splicing block installation groove (1-3) for sliding installation; The Laval nozzle type splicing block (3) is processed with a splicing block contraction section curved surface (3-2) and a splicing block expansion section curved surface (3-3) on the inner side; The Laval nozzle-type splicing blocks (3) are connected to each other to form a sealing surface (6), and sealing baffles (2) are provided on the left and right sides of the sealing surface (6).

2. The overlapping Laval nozzle groove-like cylindrical air film sealing structure according to claim 1 is characterized in that: Baffle threaded holes (2-1) are provided at equal intervals on the edges of the baffles (2) on both sides of the seal, and the baffle threaded holes (2-1) correspond to the base threaded holes (1-1) provided on the sides of the seal base (1).

3. The overlapping Laval nozzle groove-like cylindrical air film sealing structure according to claim 2 is characterized in that: Fixing bolts (4) threadedly connected thereto are inserted into the base threaded holes (1-1) and the baffle threaded holes (2-1), and the baffles (2) on both sides of the seal are fixed and then the O-type sealing rings (5) are squeezed.

4. The overlapping Laval nozzle groove-like cylindrical air film sealing structure according to claim 1, characterized in that: The curve at the contraction section surface (3-2) of the splicing block is designed according to the Witoshinsky curve, Batchelor-Shaw method, bicubic curve and quintic curve formula.

5. The overlapping Laval nozzle groove-like cylindrical air film sealing structure according to claim 4, characterized in that: The ratio of the inlet radius R1 to the throat radius R2 of the contraction section curved surface (3-2) of the splicing block is less than 0.

7.

6. The overlapping Laval nozzle groove-like cylindrical air film sealing structure according to claim 1, characterized in that: The splicing block expansion segment curved surface (3-3) is designed according to the characteristic line method, the Foulkes method and the design method of equal slope expansion.

7. The overlapping Laval nozzle groove-like cylindrical air film sealing structure according to claim 6, characterized in that: The ratio between the throat radius r2 and the outlet radius r1 of the splicing block expansion section curved surface (3-3) is less than 0.

7.

8. The overlapping Laval nozzle groove-like cylindrical air film sealing structure according to claim 1, characterized in that: The number N1 of the Laval nozzle type splicing blocks (3) arranged in the circumferential direction is ≥6, and the number N2 of the Laval nozzle type splicing blocks (3) arranged in the axial direction is ≥2.

9. The overlapping Laval nozzle groove-like cylindrical air film sealing structure according to claim 1, characterized in that: The splicing block contraction section curved surface (3-2) and the splicing block expansion section curved surface (3-3) are arranged in a symmetrical structure.

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