EP1305504A1

EP1305504A1 - Suspension

Info

Publication number: EP1305504A1
Application number: EP01962582A
Authority: EP
Inventors: Klemens Hain
Original assignee: MTU Aero Engines GmbH
Current assignee: MTU Aero Engines AG
Priority date: 2000-08-03
Filing date: 2001-08-01
Publication date: 2003-05-02
Anticipated expiration: 2021-08-01
Also published as: WO2002012680A1; DE50107765D1; ATE307270T1; DE10037837A1; CA2391082A1; US6752591B2; ES2250458T3; JP2004506113A; US20030021689A1; DE10037837C2; EP1305504B1

Abstract

Suspension of an annular secondary structure on a primary structure, in the form of a spoke-type centering device having at least three sliding guides distributed uniformly over the structure circumference, each sliding guide allowing at least a linear relative movement of the structures transversely to their axial direction. The linear direction of movement of each sliding guide runs, in relation to the structure-related radial direction at the location of the sliding guide, at an angle having a radial and a tangential direction component.

Description

suspension

The invention relates to the suspension of an annular secondary structure on a primary structure, in particular a stator structure subjected to hot gas on a housing structure of a gas turbine, in the form of a so-called spoke centering, according to the preamble of claim 1.

Spoke centers are used to hang ring-shaped secondary structures centrally on mostly ring-shaped or tubular primary structures. Radial relative movements of the structures with respect to one another should largely be possible without constraining forces and deformations, while maintaining the concentricity. The principle is particularly useful when very different thermal expansions of two concentric structures have to be compensated for. If the secondary structure is relatively elastic, i.e. is not dimensionally stable, it should be stabilized and stiffened as much as possible via the suspension.

From DE 198 07 247 C2 a turbomachine with a rotor and stator is known, which has at least one specially designed guide vane ring. The latter is designed as a self-supporting component with reinforcement on the inner shroud and with a segmented, outer shroud. The guide vane ring is positioned via a spoke centering with at least three "spokes" in the housing of the turbomachine. The sliding guides of the spoke centering have bearing journals in bearing bushes, the linear direction of movement running radially in each slide guide, based on the guide vane ring and housing.

It is also common to realize the sliding guides with sliding blocks running in straight grooves, the direction of movement, as usual, being radial with respect to the coupled structures. Experience shows that heavy wear often occurs on the sliding elements of conventional spoke centers. Permanent deformations of the thin-walled secondary structures were found in some cases. Both types of damage indicate that there are obviously greater forces in the guides than they should occur under ideal rotationally symmetrical conditions. The cause is probably non-rotationally symmetrical expansion states of the structures which can be caused in gas turbines in particular by non-homogeneous gas temperature distributions. Particularly in the case of structures with a large diameter and a large number of sliding guides, ie of "spokes", the risk of high constraining forces increases. Due to the geometry, the orientation of the direction of movement changes only slightly from guide to guide, so that when the secondary structure area in between is stretched, Both guides can become jammed by falling below the friction angle, making free structural expansion impossible. Another disadvantage of conventional radial spoke centering is that these "soft" secondary structures only stiffen if the number of sliding guides ("spokes") is odd is.

In view of these disadvantages of known spoke centering, the object of the invention is to find a suspension for a ring-shaped secondary structure on a primary structure in the manner of a spoke centering with at least three differently oriented sliding guides, which prevents or largely reduces constraining forces and deformations as well as wear and tear and which stiffeners flexible secondary structures regardless of whether the number of sliding guides is even or odd.

This object is achieved by the features characterized in claim 1, in conjunction with the generic features in its preamble.

According to the invention, the linear direction of movement of each sliding guide is inclined by an angle β to the radial direction of the structures, so that the relative movement receives a radial and a tangential component. As a result, guide clamps with all of their disadvantages are avoided with a high degree of certainty. This applies to homogeneous and non-homogeneous dimensional changes in the secondary structure. In the case of homogeneous, rotationally symmetrical expansion or contraction of the secondary structure, this also makes a small relative rotation to the primary structure due to kinematics, which is tolerable in most cases. In the case of non-homogeneous, locally different expansion or contraction of the secondary structure, it is elastically deformed to a certain extent, in deviation from the circular ring shape. The resulting the sliding guide forces are much smaller than when clamping a conventional radial spoke centering. The shape deviations will also be kept within tolerable limits. The shape stability increasing effect of the invention can lead to the fact that the secondary structure can be made more elastic and lighter than with a conventional spoke centering.

Preferred embodiments of the suspension according to the main claim are characterized in the subclaims.

The invention is subsequently explained in more detail with reference to the figures. Simplified, not to scale, show:

FIG. 1 shows a cross-section through a suspension with 8 sliding guides, showing two different, rotationally symmetrical expansion states of the secondary structure,

2 shows a partial cross section through the suspension according to FIG. 1 with an asymmetrical stretching state of the secondary structure, FIG. 3 shows a sliding guide with rigid sliding block and groove, FIG. 4 shows a sliding guide with pivotable sliding block and groove, and FIG. 5 shows a sliding guide with pin and bush.

The representations according to FIGS. 1 and 2 are largely schematic in order to reproduce the invention as simply and understandably as possible. The suspension 1 in the form of a so-called spoke centering comprises eight sliding guides 10 which are evenly distributed over the circumference and whose angular spacing is therefore 45 ° in each case. The structures coupled by means of the suspension 1, primary structure 2 and secondary structure 6, are specifically only indicated as hatched fragments in the upper area of FIG. 1. Instead of the real, ring-shaped secondary structure 6, a closed polygon with rigid chords S 1 to S8 and with joints between the chords in the slide guides 10 is considered here. The eight radial straight lines starting from the center of the structure and each offset by 45 ° only show the structure-related radial direction R to or in the tendon joints and are not to be understood as structural elements. The sliding guide 10 on the bisector (45 °) of the right upper quadrant shows that the linear direction of motion device L of the sliding guide 10 deviates by an angle β from the radial direction R and thus has in fact a radial and a tangential movement component. The angle β is preferably chosen to be greater than the maximum friction angle to be expected in the sliding guide 10, so that there is no fear of the sliding pair jamming with high certainty. In the present mentally simplified suspension 1 with an articulated tendon polygon, the sliding guides 10 of which are inclined clockwise by an angle β to the radial direction R, the change in length (extension, contraction) of a tendon leads to a sliding movement in the sliding guide at the clockwise end of the tendon, since only one slide guide is inclined by more than the friction angle to the transverse direction of the tendon per tendon, whereas the other slide guide is approximately transverse to the tendon.

For better understanding of this kinematics, the slide guide 10 is provided with additional information at the top right in FIG. 1. In addition to the structure-related radial direction R at the location of the sliding guide, the linear direction of movement L of the sliding guide 10 and the angle β between R and L, the straight extension V of the chord S8, the transverse direction / transverse direction T - at a 90 ° angle - to the chord can be recognized by dash-dotted lines S8 and the angle ßeff between L and T. Furthermore, the so-called friction cone of the sliding guide 10 is indicated by dots, the tip angle of which is twice as large as the friction angle α. Since the direction of movement L here runs perpendicular to the adjacent chord S7, the friction cone is mirror-symmetrical with respect to S7. Since the extension V lies clearly outside the friction cone, a change in length of S8 leads to a defined, jamming-free movement of the “joint” between S8 and S7 in the L direction. Thus, it would theoretically be sufficient to choose the angle βeff larger than α a real, homogeneous secondary structure behaves differently than the simple, articulated tendon polygon, for safety's sake the angle ß should be larger than α.

For a better understanding, terms such as the coefficient of friction and the angle of friction will be briefly discussed here. The relationship between the coefficient of friction f and the angle of friction α is as follows: f = tan Thus α is the inverse function of the tangent of f: α = inv tan f The following values for f can be found in technical dictionaries:

Solid friction f

Metal / metal 0.3 - ^■ 1.5

Ceramic / ceramic 0.2 ^ - 1.5

Plastic / metal 0.2 * ^■ 1.5

Limit friction 0.1 - ^■ 0.2

Mixed friction 0.01-0.1

Fluid friction »0.01

When specifying specific coefficients of friction, the following friction angles result:

f α

0.2 1 1.3 °

0.3 16.7 °

0.5 26.6 °

1.0 45.0 °

In the case of the suspension 1 shown with 8 “spokes”, the angle β is 22.5 °. This inclined position would presumably be sufficient for a maximum coefficient of friction f <0.4. With higher friction, the inclined position β to the radial would have to be increased accordingly.

In Figure 1, the tendons S1 to S8 are each shown twice, namely as a solid and a dashed line. The solid tendon polygen stands for a "cold" contracted state of the secondary structure 6. The dashed, larger tendon polygon stands for a "hot", evenly stretched state of the secondary structure 6. The primary structure 2 should - for the sake of simplicity - remain geometrically unchanged so that the part of the sliding guides 10 belonging to the primary structure does not move. With the same stretch - or contraction - all The tendon joint angles of the tendon polygon remain unchanged. For the real secondary structure 6, this means that its diameter changes, but not its shape (circular ring), the concentric position to the primary structure 2 also remaining. It can also be seen that the chord polygon - and thus the secondary structure - executes a small rotary movement by an angle γ in the clockwise direction during the transition from the solid position to the dashed position, specifically as a result of the angle β of the sliding guides 10. In practical applications, this is due to the invention , little twist for the structural function usually irrelevant.

In contrast to FIG. 1, FIG. 2 shows an asymmetrical stretching of the tendon polygon. In the practice of turbomachinery, operating states with a strongly asymmetrical temperature distribution over the flow cross-section can occur. According to FIG. 2, essentially only the tendon S1 is to be thermally stretched. The sliding guide 10 in the "joint" between S1 and S8 makes an evasive movement at an angle β obliquely upward to the right. The tendon S8 is pivoted about its right "joint" to the tendon S7, but its length is practically not changed. The kinematics predefined by the slide guides 10 means that a movement in the slide guide 10 between S1 and S8 upward to the right with a constant chord length of S8 only results in a negligibly small movement in the slide guide between S8 and S7 - to the bottom left - which is practically not representable in Figure 2. Thus, the tendon S8 de facto only swivels around its "joint" to S7, the tendon S7 remains in its position, just like the tendon S2. However, it can be seen that the "joint angle" between the tendons S2 / S 1, Change S 1 / S8 and S8 / S7. For the real secondary structure 6, this means that it is deformed asymmetrically and is no longer exactly circular. However, the actual changes in size and shape are usually so small that their effects on function and mechanical stress can be neglected. The constraining forces and deformations occurring without the present invention would generally be more harmful. Figures 3 to 5 show specific embodiments of sliding guides 1 1 to 13 with the inclined position β according to the invention.

FIG. 3 shows a sliding guide 11 with a sliding block 14 in a groove 17. The groove 17 is integrated in the primary structure 3, the sliding block 14 is firmly connected to the secondary structure 7 or machined out of it. The sliding block 14 is deliberately shown with rounded corners and with sliding surface play in the groove 17. In operation, e.g. in the case of asymmetrical structural deformation, there can be small tilting movements of the sliding block 14 in the groove 17, play and corner rounding being intended to prevent excessive friction, wear and clamping.

FIG. 4 also shows a sliding guide 12 with a groove 18 integrated in the primary structure 4 and with a sliding block 15, the latter, however - in contrast to FIG. 3 - being pivotable about an axis 16 which is firmly connected to the secondary structure 8. As a result, small relative rotations of the structures 4, 8 are possible without any problems. The fit of the sliding block 15 in the groove 18 can be carried out precisely and largely without play.

FIG. 5 finally shows a sliding guide 13 with a pin 19 in a bushing 21. The pin 19 is here firmly connected to the primary structure 5, the circular cylindrical bushing 21 is integrated in a thickening of the secondary structure 9. The lateral surface 20 of the pin 19 is spherical and rotationally symmetrical in shape in order to avoid edge wear or jamming during structural rotation. In extreme cases, the spherical shape can correspond to a spherical shape.

Claims

claims

1. Suspension of an annular secondary structure on a primary structure, in particular a stator structure subjected to hot gas on a housing structure of a gas turbine, in the form of a so-called spoke centering with at least three sliding guides distributed at equal angular intervals over the structural circumference, each of which has at least one linear relative movement between the primary and secondary structure transversely to their axial direction, the linear movement direction changing from one slide guide to the next by an angle which corresponds to the angular distance of the slide guides, characterized in that the linear movement direction (L) of each slide guide (10 to 13) to the structure-related radial direction (R ) at the location of the sliding guide at an angle (ß) with radial and tangential direction components.

2. Suspension according to claim 1, characterized in that the angle (β) is defined as a function of the maximum friction angle (α) to be expected in each sliding guide (10 to 13).

3. Suspension according to claim 1 or 2, characterized in that each sliding guide (10 to 13) comprises a sliding block (14, 15) and a groove (17, 18) or a pin (19) and a bushing (21), wherein the sliding block (14, 15) or the pin (19) is connected to one, the groove (17, 18) or the bushing (21) to the other of the two structures (2 to 5; 6 to 9).

4. Suspension according to claim 3, characterized in that the sliding block of each sliding guide has convexly curved sliding surfaces, or that the pin (19) of each sliding guide (13) has a spherical outer surface (20).

5. Suspension according to claim 3, characterized in that the sliding block

(15) each slide guide (12) is arranged to be pivotable about an axis (16) oriented in the axial direction of the primary and secondary structure (4; 8). Suspension according to one of claims 3 to 5, characterized in that at least one of the two sliding elements (14, 15), groove (17, 18) or pin (19), bushing (21), a wear-resistant, metallic and / or has ceramic sliding surface coating.