RU2805714C1 - Brush seal and method for its manufacture - Google Patents

Abstract

FIELD: seal manufacturing.

SUBSTANCE: used in gas turbine construction, mechanical engineering, aircraft engine construction and other fields. The rotor brush seal is made in the form of a clamping flange and elements sequentially joined to it - an annular wire brush and a support flange, with the free end of the brush forming a contact surface equidistant to the rotor surface in the area of their contact. In this case, the clamping flange, the annular wire brush and the supporting flange are made curved under a radius R, ensuring that the free end of the brush protrudes forward towards the oncoming flow. A method in which support flanges are placed on the sides of the mandrel, wire is wound, then the wire winding is pressed with clamping flanges, aligning their outer cylindrical surfaces along the circumference of the wire winding trim, the wire winding is cut, and then the joined elements are welded along their outer cylindrical surfaces. In this case, the wire winding is bent in half by 180 degrees between two half-rings of the mandrel, forming a U-shaped bend, the bending radius of the wires R is formed and the wire winding is cut off at the top of its U-shaped bend.

EFFECT: improving the tightness of the brush seal and increasing its service life.

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Description

The invention relates to the technology of manufacturing seals and can be used in gas turbine construction, mechanical engineering, aircraft engine construction and other fields of technology.

Increasing the operating efficiency of gas and steam turbines is associated with improving the designs and manufacturing technologies of radial seals of the gas-air path, which make it possible to reduce leakage of the working medium between the separated cavities. One of the promising types of seals are brush seals, which are a circular array of many closely spaced small-sized sealing elements - bristles (for example, RF Patent No. 2210694. IPC F16J 15/32. Method for manufacturing a brush seal and a device for its implementation. Published 08/20/2003).

It is known that to ensure optimal seal performance, the sealing elements (bristles) must be sufficiently elastic to compensate for fluctuations in the radial clearance under high vibration conditions, and the amount of interference must correspond to the value at which the power expended to overcome the frictional force in one seal does not exceed 0.15% of the power consumed by the shaft at its maximum rotation.

A brush seal is known that contains an annular package of sealing elements free at one end and fixed at the other, the gaps between which are filled with a fixing and sealing composition, while the package is fixed between the side plates, and the sealing elements of the annular package are made in the form of capillary tubes filled with antifriction material ( A.S. USSR No. 1725609. IPC F16J 15/16. Brush seal. Publ. 2005).

The disadvantage of the seal in question is the destruction of the sealant as a result of heating of the elements of the brush seal upon contact with the rotating rotor, as a result of which the leakage of the working fluid increases and the service life of the seal decreases.

A brush seal is also known, made in the form of a pressing cheek and elements sequentially joined to it - a ring wire brush and a support cheek, while the joined elements are made identical in outer diameter (A.S. USSR No. 1462916. IPC F16J 15/16. Manufacturing method brush seal. Publ. 1996).

A disadvantage of the known devices is the increased leakage of the working fluid due to significant gaps between the wire bristles.

The closest technical solution to the claimed one is a brush seal containing bundles of wires placed around the circumference in the housing, located in a plane perpendicular to the axis of rotation of the shaft, and the wires are made of different materials. In this case, wires made of a material with a high thermal conductivity coefficient are located inside the bundles, and wires made of a material with a higher elastic modulus are located outside (A.S. USSR No. 1665136. IPC F16J 15/16. Brush seal. Bulletin No. 27 1991) .

The disadvantage of this design is that placing wires made of materials with different elastic modulus values in one bundle leads to uneven operation of the sealing elements and to an increase in the gaps between the bristles due to different plastic deformations of elements made of different materials. As a result, the effect of wedging some bristles by others occurs, which reduces the tightness of the seal and leads to increased leakage of the working fluid.

The required degree of tightness of the cavities is ensured by a certain number of tightly laid metal bristle wires in the gap of the sealed pair. In one compacting stage they are stacked one relative to the other in several layers and form a rather wide layer of brush elements between the side plates. It is possible to make a small number of layers of metal bristles between the side plates of one stage, but then to ensure the required tightness of the cavities, a set of such elements is formed in several stages. An increase in the density and number of layers of bristles leads to an increase in the rigidity of the array of brush elements and, as a result, to excessive compression of the sealing surface, which reduces the power on the motor shaft and its service life due to rapid wear of the contacting pairs.

Another disadvantage of the known seals (RF Patent No. 2210694, A.S. USSR No. 1725609, 1462916, 1665136) is the insufficiently high wear resistance of the bristles during friction against the contact surface, which leads to the loss of the functional properties of the seal and the possibility of the bristles tearing off during long-term operation .

The objective and technical result of this invention is to increase the tightness of the brush seal and increase its service life.

The technical result is achieved due to the fact that in the brush seal of the rotor, made in the form of a pressing cheek and elements sequentially joined to it - an annular wire brush and a support cheek, with the free end of the brush forming a contact surface equidistant to the rotor surface in the area of their contact, in contrast from the prototype, the mentioned pressing cheek, the ring wire brush and the supporting cheek are made curved under a radius R, ensuring that the said free end of the brush protrudes forward towards the oncoming flow.

In addition, the following additional embodiments of the brush seal are possible: said radius R is selected from the range from 100 to 500 mm; the joined elements of the seal are made identical in outer diameter, and the seal is equipped with a technological ring placed on the joined elements and made in width corresponding to the total width of the mentioned elements, and the clamping jaw is made with an end protrusion as a joining element, while its outer cylindrical surface is made for the mounting nest;

Since the tightness of the seal is related to the density of the metal wire-bristles in the gap of the sealed pair, the bristles must be sufficiently elastic to maintain their dimensional and geometric characteristics during operation for a long time.

It is widely known [for example, L.L. Filimonova. Model of operation of the brush seal of a gas turbine engine. //Bulletin of engine building. No. 1, 2011, pp. 50-57.] that the main characteristics of the brush seal include such as the free length of the bristles, the protrusion of the bristles from the area of the pressing cheek, the diameter of the bristles and the density of their arrangement across the cross section of the brush. At the same time, with an increase in the diameter of the bristles, the seal provides a greater pressure drop, but the sealing deteriorates.

Increasing the amount of bristle protrusion increases the compliance of the seal, but reduces the pressure drop the seal can withstand. Increasing bristle density reduces seal leakage, but also increases the pressure drop the seal can withstand. Reducing the free length of the bristles allows you to increase the withstand pressure drop and reduce leakage, but leads to an increase in the rigidity of the brush seal, an increase in heat generation from the friction of the brushes on the rotor and a decrease in the service life of the brushes. However, as practice shows, it is undesirable to reduce leakage by reducing the free length of the bristles.

In this regard, in a brush seal it is proposed to increase the contact area at the seal-rotor interface due to the bending radius R of the brush. In this case, the larger the bending radius of the brush, the larger the contact area with the rotor surface, the greater the sealing effect. In addition, the radius R, when making a brush, ensures that the brush protrudes forward towards the oncoming flow, which makes it possible to ensure greater rigidity of the seal in the direction of the flow, while simultaneously increasing its compliance in radial deposition. This also makes it possible to increase both the free length of the bristles and their protrusion, without reducing the rigidity in the direction of the flow. Obviously, if you place the bristles with a protrusion in the direction of the flow, as proposed in the work [V.A. Mamedov, F.E. Aslan-zade. Application of non-metallic brush seals on large industrial gas turbine engines. //Bulletin of engine building. No. 1, 2012, pp. 83-91.], then with an increase in the compliance of the seal, its rigidity in the direction of the flow will be significantly reduced and the sealing effect of the seal will be sharply reduced.

There are also many different methods for making brush seals from metal wire.

Thus, according to the US patent (US Patent 6,505,835. F16J 15/32. Brush seals and methods of fabricating brush seals. 2003), the brush seal includes many bristles located in grooves. The method of securing the bristles is to place them in the grooves of the seal ring and secure the bristles in these grooves by rolling.

However, such fastening of the bristles is not reliable and does not allow the formation of a highly hermetic seal, since the bristles are distributed unevenly in the seal in the form of brushes.

There is a known method of manufacturing a brush seal for rotors (US Patent 7,653,993. F16J 15/32. Method of manufacturing a brush seal for sealing between stationary and rotary components. 2010), including winding wire onto a device that separates the wound coil of wire into two parts, followed by welding and cutting the coil of wire to form two packages of brush seals.

There is also a known method for manufacturing a brush seal (RF patent No. 2210694, IPC F16J 15/32. A method for manufacturing a brush seal and a device for its implementation. 2003), which consists in assembling a torus-shaped mandrel consisting of an annular base and two lateral annular clips Next, in the usual manner, the elastic material is wound onto the mandrel, pressed against it with annular cheeks, the elastic material is cut along the outer diameter of the mandrel and fastened to the adjacent holder and cheek, and then the elastic material is cut along the inner diameter to the required size. Before assembling the mandrel, side bevels are applied to the base, and inclined cuts are made on the holders; in addition, coaxial holes are drilled on the peripheral part of the holders, then the base is placed between the holders so that the inclined cuts of the holders are aligned with the bevels of the base. Additionally, the clips are connected to each other through drilled coaxial holes into which fasteners are inserted, as a result of which the base and two clips form a one-piece mandrel. To fix the elastic material along the outer and inner annular surfaces of the mandrel, axial notches are applied to it. When cutting the elastic material along the outer circumference, the adjacent peripheral parts of the clips along with the fasteners are cut along with it. When cutting the elastic material along the inner circumference, the adjacent part of the mandrel (base) is also removed. The last step is to separate the adjacent races and remove the remaining part of the base, obtaining two complete sets of brush seals. The invention reduces the consumption of elastic material.

The disadvantage of the known methods is that they do not provide for the formation of a brush seal, which makes it possible to simultaneously increase the compliance of the seal in the radial direction and increase its rigidity in the axial direction, which would provide increased tightness of the brush seal and increase its service life.

The objective and technical result of this invention is to increase the tightness of the brush seal and increase its service life.

The technical result is achieved due to the fact that in the method of manufacturing a rotor brush seal, in which support cheeks are placed on the sides of the mandrel with half rings, wire is wound on two half rings, then the wire winding is compressed with clamping jaws, aligning their outer cylindrical surfaces along the circumference of the wire winding trim, the wire winding is fixed and cut, and then the joined elements are welded along their outer cylindrical surfaces and machining is carried out, unlike the prototype, before crimping with clamping jaws, the said wire winding is bent in half by 180 degrees between two half-rings of the mandrel, forming a symmetrical U-shape, ensuring a bending radius R selected from the range from 100 to 500 mm, fix the said bending radius of the wires R on the winding, move the half-rings of the mandrel relative to each other parallel to the plane of the U-shaped symmetry passing through the axis of symmetry at an angle α selected from the range from 30 to 45 degrees, ensure that the resulting shape of the wires in the winding is maintained by plastically deforming them, then the wire winding is cut off at the top of its U-shaped bend.

In addition, additional methods for implementing the method of manufacturing a brush seal are possible: the aforementioned plastic deformation of the wires in the winding is carried out using a magnetic pulse method; select the diameter of said wire from the range from 0.3 to 1.4 mm; use the mentioned wire made of cobalt or nickel alloy.

To implement the method, a device for manufacturing a rotor brush seal can be used, containing a mandrel in the form of rings installed concentrically with a gap relative to each other and fastened around the circumference with screws, a device for winding and laying wire, and a coil of wire.

The essence of the invention is illustrated by drawings. In fig. Figure 1 shows the rotor brush seal. In fig. 2 is a schematic representation of the method for manufacturing the brush seal of FIG. 2a is a diagram of winding wire onto a winding device, FIG. 2b - diagram of bending wire winding by 180 degrees, FIG. 2c - diagram of the formation of a U-shaped bend, 2d - diagram of cutting the wire winding at the top of its U-shaped bend. In fig. Figure 3 shows a diagram of the formation of the longitudinal inclination of the bristles in the seal (rotation of the half-rings of the mandrel relative to each other parallel to the plane of the U-shaped symmetry passing through the axis of symmetry). In fig. Figure 4 shows the finished seal brush. Figures 1-4 contain: 1 - wire brush, 2 - clamping cheek, 3 - support cheek, 4 - stator, 5 - rotor, 6 - half-ring mandrel, 7 - wound layers of wire, 8 - coil of wire, 9 - wire, 10, 11 - device for bending wire, 12 - brush welding area, 13 - brush rounding area, 14 - wire cutting line. Radius R - radius of curvature of the brush seal. Hollow arrows indicate the direction of deformation of the winding wire during the manufacturing process of the seal, solid arrows indicate the rotation of the mandrel half-rings relative to each other parallel to the plane of the U-shaped symmetry passing through the axis of symmetry; characters "." and “+” direction of movement of the semirings: “.” - towards the observer, “+” - from the observer.

The rotor brush seal (Fig. 1) consists of a pressing cheek 2 and an annular wire brush 1 and a support cheek 3 connected in series with it. The outer cylindrical surface of the pressing cheek 2 is made for an installation socket in the stator 4.

The connecting elements are made identical in outer diameter. A locking pin can be installed in the support jaw 3 of the brush seal.

To manufacture a brush seal for the rotors, a device is used (Fig. 2), which includes a half-ring mandrel 6 containing outer, middle and inner rings fastened together. The device is equipped with a coil 8 with wire 9. The device is also equipped with centering cages with hubs connected by fasteners.

The method for manufacturing a rotor brush seal is as follows. First, the half-ring mandrel 6 is assembled (Fig. 2a). Then a layer of wire 9 is wound onto the mandrel of the half ring 6 from the coil 8, forming a wire winding 7. The wire winding 7 (Fig. 2b) is bent with a device for bending the wires 10 and 11 in half by 180 degrees between the two mandrels of the half rings 6, forming a symmetrical U-shape , providing a radius R selected from the range from 100 to 500 mm in the rounding zone of the brush 13, fix the mentioned bending radius of the wires R on the winding 7, rotate the half-rings of the mandrel 6 (Fig. 2c and Fig. 3) relative to each other parallel to the plane passing through the axis of symmetry U-shaped winding 7 at an angle α, selected from the range from 30 to 45 degrees. They ensure that the resulting shape of the wires in the winding 7 is maintained by plastic deformation, then the wire winding 7 is cut (Fig. 2d) at the top of its U-shaped bend along the cutting line 14, then the winding 7 is welded at the point of contact with the mandrel of the half ring 6 along their outer cylindrical surfaces, it is mechanically processed and two wire brushes 1 are obtained (Fig. 4).

Example

To evaluate the performance of brush seals, the following tests were carried out. Samples of brush seals were manufactured both according to the prototype method (RF patent No. 2210694) and according to the proposed method. The diameter of the wires for the brush seal in both cases was 0.3 mm, 1 mm, 1.4 mm. Test conditions: linear speed - 80 m/s, gap - 90 microns. α from 30 to 45 degrees

Table
Average Leakage from Comparing Brush Seal Options No. Type of seal Wire bending radius R Angle α, degrees Inlet pressure, kPa Flow rate through seal, kg/s 1 Prototype - (∞) thirty 200 0.038 300 0.056 45 200 0.034 300 0.049 2 Proposed 100 thirty 200 0.012 300 0.027 45 200 0.010 300 0.024 250 thirty 200 0.013 300 0.026 45 200 0.011 300 0.024 500 thirty 200 0.014 300 0.027 45 200 0.013 300 0.025 800 thirty 200 0.028 300 0.036 45 200 0.027 300 0.034

The proposed brush seal made it possible to reduce the amount of leakage by an average of almost three times (table).

The average wear of seals over 150 hours of operation was:

- for the prototype - 0.33 mm.

- for the proposed seal - 0.16 mm.

Thus, the proposed brush seal and the method of its manufacture made it possible to achieve the technical result set in the invention - increasing the tightness of the brush seal and increasing its service life.

Claims (8)

1. A rotor brush seal, made in the form of a pressing cheek and elements sequentially coupled to it - a ring wire brush and a support cheek, with a free end of the brush forming a contact surface equidistant to the rotor surface in the area of their contact, characterized in that the said pressing cheek, the annular wire brush and the support cheek are made curved under a radius R, ensuring that the said free end of the brush protrudes forward towards the oncoming flow. 2. Brush seal according to claim 1, characterized in that said radius R is selected from the range from 100 to 500 mm. 3. Brush seal according to any one of paragraphs. 1, 2, characterized in that the mated seal elements are made identical in outer diameter, and the seal is equipped with a technological ring placed on the mated elements and made in width corresponding to the total width of the mentioned elements, and the clamping jaw is made with an end protrusion as a docking element, while its outer cylindrical surface is made for an installation socket. 4. A method for manufacturing a rotor brush seal, in which support jaws are placed on the sides of the mandrel with half rings, the wire is wound on two half rings, then the wire winding is pressed with pressing jaws, aligning their outer cylindrical surfaces along the circumference of the wire winding trim, the wire winding is fixed and cut, and then the joined elements are welded along their outer cylindrical surfaces and mechanical processing is performed, characterized in that before crimping with clamping cheeks, the said wire winding is bent in half by 180 degrees between two half-rings of the mandrel, forming a symmetrical U-shape, providing a bending radius R selected from the range from 100 to 500 mm, fix the mentioned bending radius of the wires R on the winding, move the half-rings of the mandrel relative to each other parallel to the plane of the U-shaped shape passing through the axis of symmetry at an angle α, selected from the range from 30 to 45 degrees, ensure that the resulting shape of the wires is maintained in winding by plastically deforming them, then cutting the wire winding at the top of its U-shaped bend. 5. The method according to claim 4, characterized in that the said plastic deformation of the wires in the winding is carried out using a magnetic pulse method. 6. The method according to claim 5, characterized in that the diameter of said wire is selected from the range from 0.3 to 1.4 mm. 7. Method according to any one of paragraphs. 4-6, characterized in that they use the mentioned wire made of cobalt alloy. 8. Method according to any one of paragraphs. 4-6, characterized in that they use the mentioned wire made of a nickel alloy.