EP2850346A1

EP2850346A1 - Shaft seal arrangement

Info

Publication number: EP2850346A1
Application number: EP13745024.3A
Authority: EP
Inventors: Christian Kirchner
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2012-08-10
Filing date: 2013-07-25
Publication date: 2015-03-25
Also published as: US9657842B2; DE102012214276A1; US20150226336A1; CN104520618B; WO2014023581A1; CN104520618A

Abstract

The invention relates to a shaft seal arrangement (SSM) with a shaft (SH) extending along an axis (X) and with a stator (ST), wherein a rotating sealing ring (RSR) is arranged on the shaft (SH) and a static sealing ring (SSR) is arranged on the stator (ST), wherein the rotating sealing ring (RSR) has a rotating sealing surface (RSS) and the stationary sealing ring (SSR) has a stationary sealing surface (SSS), wherein these sealing surfaces (2SS) are arranged in such a way that they are located opposite one another in a sealing manner in a substantially radial sealing plane (SPL), wherein the shaft seal arrangement (SSM) is designed as a contactless gas seal, wherein at least one of the sealing surfaces (2SS) has a non-rotationally symmetrical surface contouring (SC). The object of the invention is to provide a shaft seal arrangement of a gas seal which requires comparatively little preparation effort with respect to the sealing gas. For this purpose, it is proposed that the surface contouring (SC) comprises depressions (DP) in the sealing surface (2SS), wherein the depressions (DP) in each case have a boundary line (LL) with respect to the other sealing surface (O2SS), and a bottom surface (FS) of the depression (DP) defined by means of the boundary line (LL) has a constant radial profile, wherein the depression (DP) at the boundary line (LL) adjoins the other sealing surface (O2SS) with a depth of 0.

Description

description

The invention relates to a shaft seal arrangement having a shaft extending along an axis and a stator, wherein a rotating sealing ring is arranged on the shaft and a static sealing ring is arranged on the stator, the rotating sealing ring a rotating sealing surface and the static sealing ring a standing sealing surface, wherein these sealing surfaces are arranged such that they face each other sealingly in a substantially radial plane, wherein the shaft seal assembly is formed as non-contact gas seal, wherein at least one of the sealing surfaces has a non-rotationally symmetrical surface contouring.

Gas seals are for turbomachines, in particular compressors, which are designed as turbomachinery, at higher pressures due to the relatively low leakage, the preferred sealing form. For example. Compared to conventional labyrinth seals, the order of magnitude lower leakage of the dry gas seal allows a significant increase in the efficiency of the corresponding turbomachine.

Compared to the relatively simple structure

Labyrinth seals are the modern dry gas seals comparatively demanding in terms of operating conditions. Safe operation of dry gas seals is only possible if a sliding film of dry gas between the two sealing rings is constantly supplied with gas of correspondingly high quality of preparation. The gas for supplying the gas film between the sealing rings on the one hand must be sufficiently dried and on the other hand also relatively free of foreign bodies. The auxiliary systems required for the gas treatment, for example, a process gas compressor, may well be of the order of magnitude of the actual compressor in terms of their space requirements and the investment costs. DE 690 19 296 T2, DE 692 04 703 T2, DE 693 03 749 T2, US 5,222,743 AI and US 6,152,452 AI each shaft seal assemblies are known, which are dependent on a high treatment quality of the sealing gas due to their operation.

From the search for DE 10 2012 214 276.2 are already the documents DE 19 64 150 A, DE 202 16587 Ul,

US 2003/0 209 859 A 1, US Pat. No. 6,341,782 Bl, DE 17 75 596 A, DE 2618682 Al, DE 38 39 106 A 1, DE 29 28 504 A 1,

EP 1 275 864 A 1, which also deals with shaft seals. Those who discuss gas seals are dependent on a high quality of the gasification of the gas and regularly bound by direction of rotation.

The invention has set itself the task of creating a shaft seal arrangement of a gas seal, which requires comparatively less treatment effort with respect to the sealing gas.

For the solution according to the invention it is proposed that a shaft seal arrangement of the type mentioned in the features of the characterizing part of claim 1 additionally.

A shaft seal arrangement according to the invention means an arrangement comprising a shaft seal which is also suitable for higher rotational speeds of the rotor. These include, for example, dry gas seals for high-speed turbo compressors. Unsuitable for this purpose are, for example, stuffing boxes. The dry gas seal is particularly suitable for the high-speed rotation due to the contactlessness of the two opposing sealing surfaces. The contactlessness is usually present only when a gas sliding film between the two opposite sealing surfaces from a certain

Boundary speed has formed. While the claim form stipulates that one sealing ring is standing and the other Sealing ring is provided for rotation, it is only relevant for the shaft seal assembly according to the invention that a relative rotation between the stationary and the rotating sealing ring takes place. In this respect, no absolute state of motion or rest is claimed. Of particular importance is the surface contouring at least one of the two opposite sealing surfaces. This surface contouring is inventively introduced by a targeted manufacturing in the sealing surface and not the result of lying in the manufacturing tolerance ripple of the sealing surface. The surface contouring according to the invention is also non-rotationally symmetrical, wherein a rotationally symmetric surface contouring is not excluded by the invention as an additional feature. In particular, an advantageous development of the invention provides that at least one of the two opposing sealing surfaces, preferably both opposing sealing surfaces, have a specific rotationally symmetrical convex shape. In this case, the convex shape is preferably so pronounced that a targeted gaping of the radial edge regions in the case of central radial abutment of the two sealing surfaces against one another is present from approximately 1 μm to 10 μm. Preferably, the gap is 1.5 to 3 μπι. The advantage of the surface contouring according to the invention lies in the fact that-unlike in the prior art-no dirt can accumulate in the surface contour, which in particular could influence the lift-off properties of the shaft seal arrangement In operation, it can be kept free of the dirt of the sealing gas because it can only badly adhere to the geometry according to the invention. The relatively sharp edges or discontinuities of the surface contouring or sealing surface which are usual in the prior art lead to small eddies or "dead water". Flows that favor the deposition of particles in the contouring or their contamination. Accordingly, in conventional surface contouring geometry a particular effort in the preparation of the sealing gas to be invested, which effort can be significantly lower in the geometry of the invention, since the new shaft seal assembly is more tolerant to contamination due to their self-cleaning.

Since the continuous radial course of the bottom surface of the recess according to the invention in the sealing surface already a significant advance in terms of self-cleaning

Sealing surface brings with it, the self-cleaning is further improved if the bottom surfaces also has a continuous tangential course.

For the purposes of the invention, a continuous course means that the corresponding course line or course contour is continuously differentiable in the indicated direction. Accordingly, there is a discrete - ie finite - derivative value at the locations of the required continuity. In other words, the course has no corners or edges with respect to the indicated course direction in the corresponding area. A further advantageous development provides that the defined bottom surface of the surface contouring or depression in the radial direction is twice continuously differentiable. A further advantageous embodiment provides that the bottom surface of the recess in the radial direction and in the tangential direction is twice continuously differentiable. A further advantageous development provides that the sealing surface in the radial and / or tangential direction in the region of the boundary line is simply continuously differentiable. A further advantageous development provides that the sealing surface in the region of the boundary line and especially on the boundary line is twice continuously differentiable.

The above-mentioned features with regard to constant differentiability are increasingly graded in order to minimize a tendency to fouling. All directional information, including the information on differentiability, refer to a coordinate system from the axis in the direction of the shaft axis, a radial direction perpendicular thereto and a direction tangential to these two directions. A further advantageous embodiment provides that the depression attaches steadily to the boundary line on the other sealing surface. This training additionally favors a minimization of the tendency to fouling. If, instead, a reduction in the "lift-off" speed is to be effected, it may be expedient if the recess in the region of the boundary line adjoins the remaining sealing surface discontinuously.

For improved modularization of the shaft seal arrangement according to the invention, it is expedient for the depressions to be symmetrical in relation to a radial plane, so that a rotation direction-independent

A sealing effect and "lift-off" rotational speed is produced Another advantageous development provides that the

Boundary line in the respective sealing surface forms a closed line. Alternatively, the boundary line may begin and end at a boundary edge of the respective sealing surface, thereby decreasing the lift-off speed.

In the case that the boundary line of the depression starts and ends at a boundary edge of the sealing surface or has a first end there and has a second end (in fact the boundary line is not directed) - ie forms an open geometry - it is expedient the boundary line (in the plan view of the sealing surface) has a parable shape. Also from the point of view of the production of the surface contouring, it is expedient if the depression has the geometry of a conic section (ie circle or ellipse or parabola or triangle). On the one hand, these contours can be used to achieve good "lift-off" properties and, on the other hand, they can cause good contamination tolerances, since the boundary edge of the sealing geometry is basically a circle with a relative degree is a large radius and not a straight line, the recesses are only under the proviso that the outer contour or the boundary edge is to be regarded with its large radius as a straight line and the section of a cone or a Kustrstump- fes.

According to the invention and particularly expediently, the bottom surface of the depression defined by means of the boundary line has a continuous course, in particular rising radially. Under a steady course is to be understood according to the invention that the course is jump-free. The continuous radial course means that a function of the depth of the depression as a function of the radius for each circumferential position fulfills the requirements of continuity to a real-valued function. These requirements are defined, for example, with the epsilon-delta criterion. Preferably and according to the invention, this requirement applies to all circumferential positions of the depression, including the boundary line, the boundary line lying in the sealing plane.

In this case, it makes sense and according to the invention that the recess attaches obliquely to the other sealing surface on the entire boundary line (LL), which attaches the depression with a depth of 0 to the other sealing surface along the entire boundary line.

An advantageous development of the invention provides that the bottom surface of the recesses has uneven sections. This makes it possible to improve the sliding properties.

Alternatively or additionally, for the same motivation, the bottom surface of the recesses may have flat sections.

Preferably, the sealing surface outside the recesses only on planar portions. In other words, the sealing surface is completely flat outside the recesses - in the frame the usual at this point manufacturing tolerances. In this way, the sliding properties are further improved.

A further advantageous development of the invention provides that attaches to the boundary surface of the depression on the other sealing surface with an obliquity, said obliquity is defined as an angle ALPHA between the other sealing surface to a tangent to the bottom surface of the recess directly to the Boundary line and perpendicular to the boundary line ALPHA <= 0, 03 ⁰ .

A further advantageous embodiment of the invention provides that for the depth T of the depression to the other bottom surface is 3 * (10 ^{^} -6) m <T <5 * (10 ^{^} -6) m.

A further advantageous embodiment of the invention provides that a maximum extent of the recess in the circumferential direction is between 10-40 mm. A further advantageous development of the invention provides that at least one boundary line, preferably all boundary lines in the sealing surface itself do not form a closed line. A further advantageous development of the invention provides that, in the case of a non-closed boundary line which adjoins the outer diameter of the sealing surface, an extension of the depression in the circumferential direction is between 10-40 mm at the outer diameter of the sealing surface.

A further advantageous embodiment of the invention provides that in a parabolic boundary line of the depression, the bottom surface has parabolic height height lines or lines of equal depths.

A further advantageous development of the invention provides that the boundary lines identify straight sections, which run at least partially obliquely to a radial beam or a radial.

In the following, the invention is explained in more detail with reference to drawings for exemplary clarity.

1 shows a perspective view of a

Shaft seal arrangement according to the invention,

FIGS. 2.6: each show a perspective and schematic illustration of a sealing surface according to the invention with a depression;

FIGS. 3, 7, 12, 13: in each case a section in the circumferential direction of a plan view of a sealing ring with indentations according to the invention,

Figures 4,9,10, 11: in each case a radial section through

Sealing rings according to Figures 3 and 7, wherein the designated therein with Roman numerals sections in their numerical value respectively correspond to the figure numbering, Figures 5.8: respectively a view from radially outward on the sealing ring perimeter segments of Figures 3 and 7, wherein the same context with respect Roman numerals and the figure numbering is given. FIG. 1 shows a shaft seal arrangement SSM according to the invention with a shaft SH extending along an axis X. Unless otherwise indicated, directional data - such as axial, radial, tangential or circumferential direction - in this document refers to this axis X. A plane, for example a sealing plane of a shaft seal is usually characterized in its extension by means of the surface normals or equivalently, at least two spatial directions are specified which are suitable for defining a plane. For example, an axial plane extends perpendicular to the axis (eg, shaft axis X) so that this plane extends radially and circumferentially.

A stationary relative to the shaft SH stator ST surrounds the shaft SH. The shaft seal assembly SSM further includes a shaft sleeve SSL fixedly attached to the shaft SH. Together with the shaft sleeve SSL and the shaft SSH, a rotating sealing ring RSR also rotates. The rotating one

Sealing ring RSR opposite is a static seal SSR, which is rotatably connected to the stator ST. The static sealing ring SSR has a standing sealing surface SSS, which is located in a substantially radial sealing plane SPL of a rotating sealing surface RSS of the rotating sealing ring RSR opposite. An elastic spring ESP biases the standing sealing surface SSS against the rotating sealing surface RSS. Hereinafter, the rotating sealing surface RSS and the standing sealing surface SSS, if it does not depend on their distinction, also simply referred to as the sealing surface 2SS. At least one of the sealing surfaces 2SS is provided with a non-rotationally symmetric surface contouring SC introduced by targeted production. The surface contouring SC has depressions DP, with the depressions DP having a boundary line LL to the other sealing surface 02SS. The depression DP within the boundary line LL is defined by a bottom surface FS. wrote, as shown in perspective in the figures 2, 6.

FIGS. 2 to 5 essentially show an embodiment of the recess DP according to the invention. Neglecting the curvature of the radially outer boundary edge on the side of the sealing surface 2SS of the sealing ring and considers this due to the large radius as a straight line so describes the recess DP of Figure 2, in particular in the projection of Figure 3, a triangle. In particular, in the projection of Figure 3 it is clear that this triangle is divided into two equal halves through the section IV, so that a symmetry of the depression DP is formed with respect to a radial section. This means, as in the other embodiments, an independence of the sealing ring 2SS, or obtained

Sealing effect, with respect to the direction of rotation of the shaft seal arrangement SSM according to the invention. The depression DP sets with the boundary line LL on the other sealing surface 02SS with a depth of 0, so it is continuous in approach. This grounding applies in particular to the course of the depression DP with regard to the radial section IV or in accordance with the illustration of FIG. 4. The bottom surface FS of the depressions DP itself is continuous in the region of the radial section IV as well as with regard to all other possible radial cuts. This consistency promotes minimization of the tendency to deposit contaminants.

FIGS. 6 to 11 show an arrangement whose geometry of the depression DP in the bottom surface FS is continuous not only with respect to all radial progressions but also with respect to the tangential progressions. Furthermore, this geometry - in the sense of a preferred embodiment of the invention - as evidenced by Figure 10 and Figure 8 in the radial and tangential direction continuously derivable. A particular embodiment is shown in FIG. 11, according to which the depression DP is also continuous in the region of the boundary line LL or the transition of the bottom surface FS to the other sealing surface 02SS not only in the approach of the course is. For this purpose, the bottom surface FS preferably comprises in radial section at least one point of inflection WP. Such a continuous and derived continuous geometry can be provided to minimize the tendency to foul the entire boundary line LL.

The boundary line LL in the above simplified geometric view (large radius of the boundary edge of the sealing ring is approximately a straight line) in relation to the other dimensions of the depression be designed triangular or as two half-lines, the angle at the radially innermost point of the recess DP be educated. Another preferred embodiment of the invention provides that the boundary line LL is designed as the geometry of a conic section or truncated cone section. The boundary line LL can be formed as a closed circle (FIG. 12) or as an ellipse (FIG. 13) or as a parabola (FIG. 6, FIG. 7) or as a triangle (FIG. 3, 2).

Claims

claims

Shaft seal assembly (SSM) with a along an axis (X) extending shaft (SH) and a

Stator (ST), wherein on the shaft (SH) a rotating sealing ring (RSR) is arranged and on the stator (ST) a static sealing ring (SSR) is arranged, wherein the rotating sealing ring (RSR) has a rotating axial sealing surface (RSS) and the standing seal (SSR) has a standing axial

Sealing surface (SSS), wherein these axial sealing surfaces (2SS) are arranged such that they face each other sealingly in a substantially axial sealing plane (SPL), wherein the shaft seal assembly (SSM) is designed as non-contact gas seal, wherein at least one of the sealing surfaces ( 2SS) has a non-rotationally symmetric surface contouring (SC),

characterized in that

the surface contouring (SC) comprises depressions (DP) in the sealing surface (2SS), the depressions (DP) each having a delimiting line (LL) to the other sealing surface (02SS) and a bottom surface (FS) defined by the delimiting line (LL) the recess (DP) has a continuous course, wherein the depression (DP) attaches at the boundary line (LL) with a depth of 0 at the other sealing surface (02SS).

2. shaft seal assembly (SSM) according to claim 1,

where a continuous tangential course identifies the floor surface (FS).

3. shaft seal assembly (SSM) according to claim 1,

whereby the recess (DP) at the boundary line (LL) on the other sealing surface (02SS) steadily attaches.

4. Shaft seal arrangement (SSM) according to claim 2 or 1, wherein the depression (DP) at the boundary line (LL) on the other sealing surface (02SS) discontinuously attaches.

5. shaft seal assembly (SSM) according to any one of the preceding claims,

wherein the boundary line (LL) forms a closed line in the sealing surface (2SS).

6. Shaft seal arrangement (SSM) according to one of the preceding claims 1 to 4,

wherein the boundary line (LL) starts and ends at an outer radial boundary edge of the sealing surface (2SS).

7. Shaft seal arrangement (SSM) according to one of the preceding claims 1 to 4,

wherein the boundary line (LL) starts and ends at an inner radial boundary edge of the sealing surface (2SS).

8. Shaft seal arrangement (SSM) according to one of the preceding claims,

wherein the boundary line (LL) has a parabolic shape.

9. shaft seal assembly (SSM) according to claim 6,

wherein the boundary line (LL) consists of two straight lines arranged at an angle to each other.

10. Shaft seal arrangement (SSM) according to one of the preceding claims,

wherein the depression (DP) is symmetrical with respect to an axial radial plane.