RU2698170C1 - Finger seal - Google Patents

Abstract

FIELD: engine building.

SUBSTANCE: invention relates to turbo and propulsion engineering and can be used in designs of gas turbine engines and steam turbines to seal radial clearances. Finger seal comprises annular parts adjoining each other, each of which comprises pins regularly spaced along circumference, formed by making slots in annular parts, wherein the ring parts are installed so that the fingers of each annular part overlap the slots of the adjoining another circular part. Slots in annular part are made in form of alternating inner and outer radial cuts, wherein internal and external cuts extend respectively to inner and outer surfaces of annular part, number of internal and external cuts is equal to each other, at the same depth of the upper notches and at the same depth of the lower cuts, at the depths of the cuts, which do not exceed in the radial direction the width of the annular part, and if the pitch t of the notches location is equal, and mutual overlapping of slots of each annular part by pins of other annular part adjoining to it is provided due to shift in tangential direction of circular parts relative to each other.

EFFECT: higher efficiency of finger seal at considerable deviations of rotor.

6 cl, 3 dwg

Description

The invention relates to the field of turbo and engine building and can be used in the construction of gas turbine engines and steam turbines for sealing radial clearances.

Radial clearances in the flow part of steam and gas turbines make it possible to exclude “jamming” of the rotor and stator during operation. At the same time, the requirement to minimize the overflow of the working medium through the annular gap between the rotor and the stator (between the working blades and the nozzle apparatus, the shaft and the housing, etc.) makes it necessary to install seals in the flow part.

One of the most effective radial clearance seals is finger seals. It is known, for example, a reversible finger seal, containing at least two pairs of thin ring parts folded into a stack, each of which contains an annular array of radially and tangentially entering fingers, between which there are gaps. The ring parts of each of the pairs are arranged so that the fingers of one ring part overlap the slots in the other. Moreover, the fingers of the ring parts of one of the pairs are located at an angle in a clockwise direction, and the fingers of the ring parts of the other pair are in a counterclockwise direction (US patent No. 5031922, IPC F16J 15/447, Bidirectional finger seal. 1991).

The disadvantage of this seal is that it cannot compensate for significant deviations of the rotor due to thermal and mechanical deformation, because the shape of the fingers is not optimal in terms of the elastic properties of this design. The insufficient flexibility of the fingers leads to the fact that during operation due to excessive compression of the sealing surface, burns may occur on the contacting surfaces of the fingers and the rotor surface, a decrease in power on the motor shaft, and increased wear of the contacting pairs.

The closest in technical essence to the proposed one is a finger seal containing two adjacent ring parts, each of which contains fingers evenly spaced around the circumference, formed by making slits in the ring parts, at least one of which has protruding pads made integrally with the corresponding fingers, and the annular parts are mounted so that the fingers of each annular part overlap the slots adjacent to the other ring Second part. All fingers have the same thickness and are separated from each other by the same slots (US Pat. No. 5,754,545, IPC F16J 15/447, Noncontacting finger seal with hydrodynamic foot portion. 1998).

The disadvantage of this invention, as well as the previous one, is the insufficiently high flexibility of the fingers, which does not allow it to be used with significant deviations of the rotor during operation. Another disadvantage of this seal is that due to the one-sided tilt of the fingers (clockwise or counterclockwise), it cannot be used for efficient sealing of rotors with the possibility of reverse movement.

The technical result of the claimed invention is to increase the efficiency of the finger seal with significant deviations of the rotor during operation and increase the reliability of the seal by improving the flexibility of the ring parts and fingers of the seal.

The indicated technical result is achieved in that the finger seal containing annular parts adjacent to each other, each of which contains fingers evenly spaced around the circumference, formed by making slits in the annular parts, and the annular parts are installed so that the fingers of each annular part overlap the slots adjacent to it another annular part, unlike the prototype, the slots in the annular part are made in the form of alternating internal and external radial addresses located at the same pitch, with internal and external notches extending respectively to the inner and outer surfaces of the annular part, the number of internal and external notches is equal to each other, and they have the same depth, not radially exceeding the width of the annular part, and the mutual overlap of the slots each ring part with the fingers adjacent to it another ring part is provided due to the shift in the tangential direction of the ring parts relative to each other.

The specified technical result is also achieved by the fact that in the finger seal the amount of shift in the tangential direction of the ring parts relative to each other is (0.2 to 0.8) t, where t is the pitch of the incisions.

The specified technical result is also achieved by the fact that in the finger seal: at least one of the annular parts has protruding pads made in one piece with the corresponding fingers; the inner surfaces of the protruding pads of at least one of the annular parts have a honeycomb structure in the form of an array of cells with a ratio of the depth of the cells to the diameter of the circles inscribed in them in the range of 0.3 ... 0.5; cells are hexagonal or round, or square, or triangular; the diameter of the circle inscribed in the cells is not more than 1 mm.

The execution in the annular part of the slots in the form of alternating internal and external radial cuts allows one to increase the flexibility of the seal, reduce wear and eliminate damage to the contacting pairs, which, accordingly, increases the efficiency and reliability of the finger seal.

In this case, the internal and external cuts extend respectively to the inner and outer surfaces of the annular part, which allows the annular part to be made in the form of a zigzag spring spanning the mating part (turbine rotor). To ensure a zigzag shape of the spring, the number of internal and external notches is taken equal to each other. The uniformity of pressing the annular seal to the mating part is achieved under the following conditions: the same depth of the upper cuts, the same depth of the lower cuts, with the depth of the cuts not radially exceeding the width of the annular part and if the pitch t of the cuts is equal. The tightness of the seal is ensured by the mutual overlapping of the slots of each annular part with the fingers of the adjoining other annular part, which is achieved due to the shift in the tangential direction of the annular parts relative to each other.

The design of the proposed finger seal is illustrated by the schematic drawings.

In FIG. 1 is a schematic isometric view of a fragment of a finger seal; in FIG. 2 is a diagram of the superposition of two annular adjacent annular parts of a finger seal; in FIG. 3 is an isometric view of a finger seal and a shaft to be sealed.

Figures 1-3 contain: 1, 2 - ring details; 3, 4 - sealing fingers; 5, 6 — slotted holes; 7 - protruding pads seals; 8 - external radial cuts; 9 - internal radial cuts; 10 - ring covers; 11 - detail of the rotor. The arrows indicate the direction of rotation of the rotor relative to the seal.

The finger seal consists of two annular parts 1 and 2 adjacent to each other (Fig. 1), each of which contains fingers 3 and 4 evenly spaced around the circumference (Figs. 1 and 2), between which there are slots 5 and 6, corresponding to them. On the annular part 1, located on the side of the low-pressure cavity, there are protruding pads 7, made in one piece with the corresponding fingers 3. The annular parts 1 and 2 are oriented through holes made in the annular parts 1 and 2 (not shown) and installed relative to friend so Thus, the fingers of each annular part overlap the gaps between the fingers in another annular part, the width of the fingers being greater than the width of the slots they overlap. Mutual overlapping of the slots of each annular part with the fingers of the adjoining other annular part is ensured by a shift in the tangential direction of the annular parts relative to each other. The shift in the tangential direction of the ring parts relative to each other is (0.2 to 0.8) t, where t is the pitch of the incisions.

In an expanded embodiment of the design of the finger seal, the annular parts 1 and 2 can be pressed from the side of the low and high pressure cavities by the ring caps 10 (Fig. 3) to increase the rigidity of the structure in the axial direction.

A package of annular parts 1, 2 and annular covers can be secured using connecting elements, such as rivets (not shown in the drawings), located in through holes around the circumference of the finger seal. To improve the accuracy of the installation of ring parts, spike-groove joints can be used.

The above description of the finger seal is made for the case of using two ring parts with fingers, but does not exclude the use of a larger number of ring parts.

Finger seal works as follows.

Between the rotor part 11 (Fig. 3) and the fingers 3 and 4, the minimum allowable clearance is set, which is selected from the condition that the rotor part 11 does not touch the protruding pads 7 during normal operation (depending on the dimensions of the rotor and the operating conditions, the gap is 0.05 ... 0.2 mm).

In the process of starting and changing the engine operating mode, when significant deviations of the rotor part 11 occur, the fingers 3 and 4 come into contact with the surface of the rotor part 11. In this case, the fingers 3 and 4 are deformed, which prevents “jamming” of the rotor and stator parts.

In contrast to the known finger seals, the proposed design has increased elastic properties, which allows the use of this seal with significant rotor vibrations without compromising the operability of the structure.

Another advantage of the proposed design is that protruding platforms due to the elasticity of the annular part provided by the alternation of internal and external radial cuts (forming a zigzag spring from the annular part) are deflected mainly in the radial direction, which allows the use of this design to seal rotors that have the ability to reverse movement (Fig. 3).

To obtain finger seal gaps, for example, pulsed electrochemical processing can be used, the main advantages of which are the following: no wear of the electrode tool during processing, absence of a thermally changed layer, sharp edges and burrs on the treated surface, the ability to simultaneously treat all inter-finger grooves with a special electrode - tool, rather low processing error (maximum 20 ... 30 mm), the good performance of the roughness (R _a 0.2 ... 1.25 mm - depending m material).

Thus, the proposed invention due to the increased flexibility of the ring parts and fingers allows you to use it with significant deviations of the rotor during operation, and also increases the reliability of the seal by reducing wear and the likelihood of damage to the contacting pairs.

Claims (6)

1. A finger seal containing annular parts adjacent to each other, each of which contains fingers evenly spaced around the circumference, formed by making slits in the ring parts, the ring parts being installed so that the fingers of each ring part overlap the slots of the adjacent other ring parts, characterized in that the slots in the annular part are made in the form of alternating with each other internal and external radial cuts located at the same pitch, and inside The cuts and the external cuts extend respectively to the inner and outer surfaces of the annular part, the number of internal and external cuts is equal to each other, and they have the same depth that does not radially exceed the width of the annular part, and the mutual overlap of the slots of each ring part with the fingers adjacent to it annular parts is provided due to a shift in the tangential direction of the annular parts relative to each other. 2. A finger seal according to claim 1, characterized in that the amount of shear in the tangential direction of the ring parts relative to each other is (0.2 to 0.8) t, where t is the pitch of the incisions. 3. A finger seal according to claim 1, characterized in that at least one of the annular parts has protruding pads made in one piece with the corresponding fingers. 4. Finger seal according to claim 3, characterized in that the inner surfaces of the protruding pads of at least one of the ring parts have a honeycomb structure in the form of an array of cells with a ratio of the cell depth to the diameter of the circles inscribed in them in the range of 0.3 ... 0.5 . 5. The finger seal according to claim 4, characterized in that the cells have a hexagonal, or round, or square, or triangular shape. 6. A finger seal according to claim 5, characterized in that the diameter of the circle inscribed in the cells is not more than 1 mm.

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