JPH0351582A - Dry gas sealed apparatus - Google Patents

Abstract

PURPOSE: To prevent damage caused by temperature, temperature fluctuation, increase of peripheral speed and rotational speed by providing a centering joint which has spring-elasticity against a shaft bush at the time of expansion of the shaft, and prevents expansion of the shaft bush in an area of a seal surface in respect to the shaft. CONSTITUTION: A shaft 1 has, in an inner area 1', a cylindrically ring web 15 which surrounds the shaft 1 by means of a circular space 15'. An end 3' corresponding to a shaft bush 3 has a cylindrically circular groove 16 which is engaged with the web 15 to form a centering seat of a form-fitting type in a cooled state. An outer peripheral surface of a peripheyral wall 16' is sealed by an O-ring like packing 16" in respect to the web 15. The packing 16" follows up diameter fluctuation of the web 15 to some extent. An inner peripheral surface of the peripheryal wall 16' has a radial margin 4 in respect to the shaft 1 simillarly to the bush 3, while the margin 4 allows sufficient increase of the diameter of the shaft at the time of heating without contact. To the contrary, the peripheral wall 17 is spring-elastically composed, and is contact with the web 15 at an inward circular portion 17', for securing fitting of the shaft 1 at the time of temperature rise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a dry gas sealing device configured as an axially sliding ring packing for an illll1 rotating through a caning wall, the device comprising: The present invention is of the type having an axial bush which rotates therewith and is designed as a carrier for a sealing surface, and a circumferentially oriented sliding ring having a sliding surface which is pressed onto said sealing surface and is lubricated by gas.

[Conventional technology]

(3) Such a needle arrangement in the +Ill+ direction is known, for example from EP 13 678, and is used in the casing of a turbomachine, such as a turbocompressor or a turbine, under certain pressure. It is used to seal the chamber at the passage of the shaft to the outside or to the intermediate chamber to prevent the escape of pressure medium from the caning inner chamber. This prevention of outflow is carried out using a blocking medium, for example a sealing gas, which presses the sliding surface of the sliding ring against the sealing surface and thus minimizes the outflow of gas from the housing interior, in which case the sealing gas Leakage of the device is kept to the minimum possible value by appropriate packing rings. At the same time, a gap is created for contactless rotation of the sealing device.

A disadvantage in this case, especially for turbomachinery operating at high gas temperatures of several hundred degrees Celsius, is that high temperature rises and large temperature fluctuations occur at the shaft penetrations in the casing wall, resulting in individual This is to thermally expand the member. This thermal expansion causes unacceptable deformations (4) which impair the sealing action. Moreover, if the rate of rise is relatively high and this causes expansion of the shaft, the shaft bushing and some sealing bodies, usually made of ceramic, may break and cause damage to the turbomachine. subject to severe mechanical stress.

Particularly in high-speed turbo engines, a particularly large centrifugal force is generated in some parts of the casing, causing deformation. As a result of this deformation, at higher circumferential speeds, for example, the IW1 bushing, together with the sealing body, moves away from the shaft and a specific position and centering of the bushing is no longer maintained. This creates an imbalance and an unacceptable change in the seal gap. Due to the different elongations of the shaft bushing and the sealing body under the action of centrifugal force, mechanical stresses in the sealing body increase and there is a risk of damage.

For this reason, the permissible temperatures and temperature fluctuations as well as the speed of rotation are subject to limitations in known gas-barrier axial spooling devices.

[Problem to be solved by the invention]

It is an object of the present invention to eliminate the aforementioned drawbacks of the prior art and to improve an axial shaft sealing device, in particular of the type mentioned at the outset, so that the peripheral velocity and To enable a shaft to be properly sealed without the risk of damage even when the number of revolutions increases.

[Means to solve the problem]

The configuration means of the present invention for solving the above problem is such that a shaft deco with a sill flange encloses the shaft with radial play and is connected to the shaft by a form-fitting centering joint, and the centering joint is a type II111. It is configured to be spring-elastic with respect to the shaft bushing upon expansion and to prevent expansion of the shaft bushing in the area of the sealing surface relative to the shaft.

In this case, in order to produce an elastic centering joint of the above type between shaft bushing and shaft particularly advantageously,
The shaft has a cylindrical ring-shaped web surrounding the outer circumferential surface of the shaft at a radial interval, and the web fits into the cylindrical annular groove of the shaft puncture, and the web fits into the radially outer circumferential wall of the shaft groove. is spring-elastic, while the radially inner circumferential wall is of rigid construction. When the temperature rises and accordingly the shaft expands and the webbing moves in the radial direction, the circumferential wall of the radially outer edge of the groove is elastically deformed and the shaft deformation buttoned on the shaft is Helps to make shape-fitting centering fixed. The shaft bush itself is not deformed in this case, but rather is self-aligned so that the position of the sealing surface is not adversely influenced. Expansion of the groove in the shaft bushing due to centrifugal forces at increased rotational speeds is prevented by a positive fit between the rigid radially inner circumferential wall of the groove and the rigid web of the shaft.

[Effect]

The function of the sealing device of the invention is therefore virtually independent of the operating temperature of the turbomachine, and also of the shaft rotational speed or circumferential speed. The spring-elastic centering joint according to the invention provides a fixed positioning of the shaft bushing on the shaft, in any case independent of the temperature, circumferential speed and material of the parts that influence the sealing gap (7). It is possible to use materials with different coefficients of thermal expansion for the shaft and shaft bushing. In particular, this makes it possible, for example, to match the thermal expansion of the shaft bushing to the thermal expansion of the sealing body, which results in a further improved sealing effect and a further reduced risk of breakage.

〔Example〕

Next, embodiments of the present invention will be explained in detail based on the drawings.

In the embodiment shown, the shaft 1 is guided in a gas-tight manner, for example through the housing wall 2 of a turbomachine, from a high-pressure Pi region to a low Pa pressure region. The sealing device is shaft 1
It has a shaft bushing 3 mounted on the shaft bushing, which encloses the shaft 1 with a radial play 4, so that changes in the diameter of the shaft 1 due to heating during operation are absorbed without deformation of the shaft bushing 3. . On the other hand, in the outer region 1 of the shaft 1, the bushing 3 is resiliently supported on the shaft 1 by means of the sleeve-like end 3. Absorbed without affecting the seal gap.

The shaft bushing 3 is made of a metal having a coefficient of thermal expansion smaller than that of the shaft 1, such as high nickel alloy steel known under the trade name Amber. is advantageous. The shaft bushing 3 supports a seal body 5 on its outer circumferential surface, and the shank seal body forms an annular sealing surface 6 on its outer circumferential surface. Advantageously, the sealing body 5 consists of a hard metal having a coefficient of thermal expansion similar to that of the shaft bushing 3, for example silicon carbide. However, tungsten carbide or other materials with similar sliding properties are also suitable.

The illustrated sealing device consists of a slide I which is arranged circumferentially in position, i.e. non-rotatably, in a packing holder 2' inserted into the casing wall 2, but which is somewhat slidable in the axial direction.
It has a sliding ring 7 which is centered on the inner peripheral side 7' with respect to the extension 8 of the packing holder 2'.

The sliding ring 7 and the packing holder 2' are advantageously made of a metal with a low thermal expansion capacity, for example a high nickel alloy steel, such as is known under the trade name Amber. The sliding D ring 7 is on the side of the internal bridge.
A sliding body 9 having a sliding surface 9' facing the annular sealing surface 6
The sliding body is made of a material with good sliding properties, for example a carbon ceramic material, to which metal additives may be added to improve the thermal conductivity.

The shaft sealing device is supplied with sealing gas via a line 10 through the housing wall 2 at a pressure Ps, which pressure may be slightly higher than the high pressure Pi to be sealed of the turbomachine. The pressure P8 can then be taken off from the turbomachine itself or supplied as an external gas. The sealing gas passes through the gap 11 and reaches the back surface 7'' of the sliding ring 7 and presses the sliding IJ ring against the shaft bushing 3, so that the sealing surface 6 of the rotating seal body 5 is aligned with the circumferentially oriented sliding body 9. It rests on the sliding surface 9', thus effectively preventing the escape of gas from the interior of the casing.Nevertheless, the trace gases that escape are conducted off via the conduit 13.The lubrication of the sliding surface is then This is carried out in a known manner, for example aerodynamically via pockets or grooves in the sliding surface or sill surface, or aerostatically by supplying gas to the sliding surface through the sliding body.

In this embodiment, in addition to the sealing device described above, a sliding sealing device 14 having almost the same structure is provided in order to further improve the sealing effect or as an emergency sealing device in the event of a failure. The sliding ring sealing device can also be omitted in some cases.

During operation of the turbomachinery, the outer diameter of the shaft 1 becomes larger than the inner diameter of the shaft bushing 3 during operation of the turbomachinery in the case where the shaft 1 and the shaft bushing 3 can have significantly different temperatures. The problem arises that it expands significantly. On the contrary,
As the rotational speed increases, the shaft bushing 3 tends to expand more significantly than the shaft 1. Shaft 1 and shaft bushing 3 (11
) The shaft punch 3 is connected to the shaft 1 by a spring-elastic joint to absorb the diameter variation of the shaft, and the spring-elastic joint allows the occurrence of a difference in radial expansion at the joint, but the spring effect This is a joint that does not adversely affect the position of the shaft bushing 3 and the dimensions of the shaft bushing in the Nohru surface area, which are important for the construction of the shaft bushing.

For this purpose, the shaft 1 has in its inner region 1' a cylindrical ring-shaped web 15 which surrounds it with an annular gap 15'. On the other hand, the corresponding end 3' of the shaft bushing 3 has a cylindrical annular groove 16, which groove is connected to the web 15 integrally formed on the shaft 1.
are designed to engage to form a form-fit centering seat in the cooled state. For this purpose, the radially inner circumferential wall 16' of the annular groove 16 is designed with a wall thickness such that the wall is relatively rigid and, in other words, not deformable. The outer circumferential surface of the radially inner circumferential wall 16' is sealed against the web 15 by an O-ring-shaped packing 16'', which is capable of following a certain (12) diameter variation of the web 15. The inner circumferential surface of the radially inner circumferential wall 16' has a radial play 4 with respect to the shaft 1, similar to the full-shaft disk 3, and the radial play has a sufficient amount of the shaft during heating. An increase in diameter is allowed without contact, whereas the radially outer circumferential wall 17 of the cylindrical annular groove 16 is constructed in a spring-elastic manner and presses against the web 15 by means of the button 9 and the inward ring 17'; This makes it possible to ensure a firm centering even when the temperature of the shaft 1 increases.However, during thermal expansion of the shaft 1 buttoning in the inner region 1', and thus also when the diameter of the web 15 increases, the radially outward shift can be ensured. However, due to this elastic deformability, the shaft bushing 3 remains in its position in the area of the sealing surface and is not subjected to any stresses. 1 does not cause deformation of the seal gap and there is no risk of damage to the function of the shaft bushing 3.On the other hand, the expansion of the cylindrical annular groove 16 of the shaft bushing 3 increases the rigidity of the groove. This is prevented by the engagement of the radially inner peripheral wall 16' with the cylindrical ring-shaped web 15 of the shaft 14, so that the shaft bushing 3 can also be adjusted to its position and centering without deforming the sill gap. hold

〔Effect of the invention〕

In short, the shaft sealing device of the present invention is suitable for turbomachines with high temperatures that cause significant temperature fluctuations in the shaft penetration part during operation, and also for turbomachines with high rotational speeds and high circumferential speeds. There is. The shaft reeling device according to the invention provides a high operating performance of turbomachines without the need for expensive cooling measures. 'At the same time, it enables operation at high rotational speeds.

Equivalently, the slipping C IJ near the low pressure Pa in the outer area 1''
This also applies to the centering joint between the shaft and shaft bushing that is attached to the button sealing device 14; in this case, the shaft bushing is
5I11. so that temperature-induced expansion of the shaft occurs in the sealing surface area and no deformation is transmitted to the shaft bushing. sexually +
1°4 is formed.

[Brief explanation of drawings]

The drawing is a cross-sectional view along the axis of a shaft packing as an embodiment of the dry gas seal device according to the present invention. 1...IQL 1'...1 no 1 part'' precept, 1''...
・Outer area, 2...Casing=L 2'...Packing holder, 3...11q11 bushing, 3'...Corresponding end, 3"...Sleeve-shaped end, 4...Radius Directional play, 5... Seal body, 6... Annular sill surface, 7.
...Sliding ring, 7'...Inner peripheral surface side, 7"...Back surface, 8...Additional part, 9...Sliding body, 9'...Sliding surface, 1 o, 1 3- m tube, P1
... 11 fortune-telling・j L''2, Pa ---
Low L pi, P day... Seal gas pressure, 14...
・Sliding IJ seal installation, 15...Cylindrical ring-shaped web, 15'...Annular gap, 16...Cylindrical annular groove, 16'...Radially inward peripheral wall, 16"...・・・
○Ring, 17... Radial outer peripheral wall, 17'.
・Inward ring part (15)

Claims (1)

Claims: 1. Dry gas sealing device configured as an axial sliding ring packing for a shaft (1) rotating through a casing wall (2), rotating together with said shaft (1). a circumferentially oriented sliding ring having an axial bush (3) configured as a carrier for a sealing surface (6) and a sliding surface (9') pressed against said sealing surface (6) by means of gas and lubricated; (7), in which the shaft bushing (3) with a sealing flange encloses the shaft (1) with a radial play (4) and a positive-fit centering joint (15, 1
6) to said shaft (1), said centering joint being connected to said shaft bushing (3) when said shaft (1) expands.
Dry gas sealing device, characterized in that it is spring-elastic against the shaft (1) and is configured to prevent expansion of the shaft bushing (3) in the area of said sealing surface (6) relative to the shaft (1). . 2. A centering joint between the shaft (1) and the shaft bushing (3) has a cylindrical ring-shaped web (15) on one member (1), and the web has a cylindrical ring-shaped web (15) provided on the other member (3). 2. The dry gas sealing device according to claim 1, wherein the centering joint fits in a groove (16) of the centering joint, and at least a portion (17) of the centering joint is configured radially elastically. 3. A cylindrical ring-shaped web is located inside the casing (1'
) is arranged axially on the shaft 1 towards the outer area of the casing and surrounds the shaft with a gap (15).
and a cylindrical annular groove is provided on the side of the sealing flange of the shaft bushing (3) opposite to the sealing surface (6) and surrounding the cylindrical ring (15).
16) The dry gas seal device according to claim 2, configured as: 16). 4. The groove (16) connects the packing (
a radially inner rigid peripheral wall (16') sealed by a radially inner rigid peripheral wall (16') and at least an inner region end (17');
4. Dry gas sealing device according to claim 3, characterized in that it is formed by a radially outer spring-elastic circumferential wall (17) which presses against the outer circumferential surface of the web (15) at a point 1). 5. The dry gas seal device according to any one of claims 1 to 4, wherein the coefficient of thermal expansion of the shaft bushing (3) is smaller than the coefficient of thermal expansion of the shaft (1).