Guide vane for a gas turbine

The invention relates to a guide vane for a gas turbine, in particular a low-pressure turbine, with an airfoil extending between an inner platform and an outer platform, said outer platform having attachment means for attachment to a housing, a vane segment of at least three vanes and a Leitkranzverbund ,

Vanes of low-pressure turbines are made of metal and are generally brazed together in the development phase into segments of three or six vanes. In the investigations of the aerodynamic design of the profile of the blades, a plurality of stator blade segments are combined to form a closed Leitkranzverbund as in a real gas turbine engine, the individual Leitschaufelsegmente to compensate for thermal expansion are not rigidly interconnected. The vanes are attached to their outer platforms in a (engine) housing and od on their inner platforms by metal brackets. like. releasably clamped together. By clamping on the inner platforms, the vibration behavior of the blades should be improved. The use of the bracing brackets as additional components has the disadvantage of a more complex installation and higher costs.

For the calibration of aerodynamic design methods and for the rapid determination of experimental data from pressure, velocity or flow field measurements, guide vanes made of usually carbon fiber reinforced plastics are used and in so-called aerodynamic<img file="EP0899426A2_D0001.tif" />Such guide vanes are much faster and cheaper to produce than corresponding metal vanes and are therefore preferred in the upstream investigations used in the test stand, the vanes made of plastic at significantly lower temperatures (about 130 ° C) than in the real Operation, but loaded with gas forces of the same magnitude as in the real engine.

The problem is to take over the geometry of the outer and inner platform of the metal vanes for those made of plastic, as they can not withstand the stresses of high, real gas forces. Bonding three or six vanes each to individual vane segments from which the vane assembly is formed has not solved this problem any more than clamping the vanes by means of bolts provided in the lateral end faces of the outer and inner platforms. The vibration amplitudes were too large and led to fractures of the vanes.

The invention has for its object to provide a guide vane of the type described above, which has an improved dynamic vibration behavior, limits the vibration amplitude of adjacent vanes and manufacturing technology is simple and inexpensive to manufacture.

The object of the invention is characterized in that in that at least one of the outer or inner platform at a first lateral end face has a projection with a protruding side surface and at a second, opposite, lateral end face has a receptacle for the positive reception of a projection of an adjacent guide vane, whose sizing is tailored to the lead, that the inner and outer platforms of adjacent vanes are aligned in the mounted state.

The advantage is that, for example, adjoining vanes of adjacent vanes segments (for example, three interconnected vanes) are positively coupled to each other in the axial direction and caused by the friction on the contact surfaces a damping effect. In addition, the projections cause a seal between columns occurring between the platforms.

In a preferred embodiment, the side surface of the projection is perpendicular to the first, generally in the radial direction end face of the outer or inner platform. The side surface of the projection thus extends in the direction of the gas flow heavily loaded circumferential direction, where it allows damping due to friction at the contact surfaces.

Preferably, the side surface of the projection protrudes at least 3 mm beyond the first end surface of the outer or inner platform, so that there is a sufficiently large frictional or contact surface with the receptacle of an adjacent guide vane.

It is advantageous that the projection makes up at least 30% of the (cross-sectional) area of ​​the first end face so that the adjacent guide vanes are not only selectively coupled to one another and a reliable limitation of the oscillation amplitude is made possible.

Furthermore, it is preferable that the projection is seated with clearance in the exception of the adjacent vane, so that, for example, adjacent vanes of adjacent vane segments can easily move away from each other and toward each other due to thermal expansion.

Most preferably, an inner surface of the receptacle adjacent to the second end surface extends parallel to the side surface of the projection in the mounted state, so that secure frictional contact between the inner surface of the receptacle and the side surface of the projection is ensured.

It is preferred that the outer platform comprises a platform and a stiffening wall connected by spaced transverse struts and / or the inner platform comprises a platform and a reinforcing wall. As a result, the torsional and bending stiffness of the inner platform and in particular the existing of the platform, the stiffening wall and the two transverse struts outer platform, which is also provided with the attachment means for attachment of the guide vane on the engine housing, significantly increased. By this geometric measure, the vane holds even when using relatively weaker materials, such as fiber reinforced plastic, the relatively high real gas forces.

In a preferred embodiment, the vane is integrally formed so that it can be inexpensively manufactured by metal or injection molding.

Most preferably, the vane made of carbon fiber reinforced plastic, so that they are in so-called. Aerodynamic <img file="EP0899426A2_D0002.tif" />Cold test stands can be examined. This allows much faster and less expensive experimental data to be obtained for the calibration of aerodynamic design methods than is the case with the use of metal vanes. Such experimental plastic vanes can be connected by gluing also to Leitschaufelsegmenten of three or six vanes. The side surface of the projection offers for this purpose adhesive surfaces which, in contrast to the first and second end faces of the outer or inner platforms are not subjected to tension / compression, but to shearing. This is the much cheaper form of load for glued joints.

Further embodiments of the invention are described in the subclaims.

In the following the invention with reference to an embodiment will be explained in more detail with reference to a drawing. It shows:<dl id="dl0001"><dt>Fig. 1</dt><dd>a longitudinal section in perspective view of an embodiment of the guide vane according to the invention,</dd><dt>Fig. 2</dt><dd>a side view of the vane of Fig. 1,</dd><dt>Fig. 3</dt><dd>a side view of the oscillating vane of FIGS. 1 and 2,</dd><dt>Fig. 4</dt><dd>a longitudinal section in perspective view of a vane segment of three vanes of FIG. 1 to 3 and</dd><dt>Fig. 5</dt><dd>a perspective view of the vane segment of Fig. 4th</dd></dl>

Fig. 1 shows a generally designated 1 embodiment of the guide vane according to the invention, which consists of carbon fiber reinforced plastic and is produced by injection molding. Such a vane 1 is in so-called. Aerodynamic<img file="EP0899426A2_D0003.tif" />Cold test rigs are used to quickly and inexpensively determine test data from pressure, velocity and flow field measurements for calibration of aerodynamic design procedures.

The vane 1 comprises an airfoil 2, an outer platform 3 comprising a platform 3 'and a stiffening wall 4 spaced therefrom, and an inner platform 5 comprising a platform 5' and a reinforcing wall 6 connected thereto and also spaced therefrom. Both the outer and the inner platform 3 and 5 is provided at a first end face 7 with a projection 8, which in each case has a about the first end face 7 by about 3 mm protruding side surface 9.

When a plurality of stator blades 1 are assembled into an annular diaphragm assembly and secured in an engine casing, the airfoil 2 is disposed substantially in the radial direction of the engine assembly with its longitudinal extent m between the outer and inner platforms 3 and 5, respectively.

FIG. 2 shows the vane 1 of FIG. 1 in a side view in which the substantially parallel to the (outer) platform 3 'extending stiffening wall 4 and with the (inner) platform 5' connected, extending over several corners reinforcing wall 6 are shown. On the outer platform 3, two hook-like fastening means 10 for attaching the guide vane 1 are formed on an engine casing (not shown). The between the (outer) platform 3 ', the stiffening wall 4 and extending therefrom cross struts 10 on the one hand and the (inner) platform 5' and the reinforcing wall 6 on the other hand present cavity each forms a receptacle 12, with the second end face 13 of the outer and inner platform 3 or 5 is provided.

If multiple vanes 1 are assembled into a Leitkranzverbund, a projection 8 of an adjacent vane 1 is received in a form-fitting manner in this receptacle 12, wherein its dimensioning is adapted to that of the projection 8 so that the outer and inner platforms 3 and 5 adjacent vanes 1 in the assembled state are aligned, as this in Fig. 4 and 5 can be seen. The receptacle 12 has an inner surface 14 adjoining the second end surface 13, which in the installed state forms a contact surface with the side surface 9 of the projection 8 due to the coordinated dimensioning of the projection 8 and the receptacle 12. In this way, a seal between adjacent vanes 1 is also achieved. In Fig. 2 It can be seen that the projection 8 and the receptacle 12 more than 50% of the lying in the image plane cross-sectional area of ​​the first or second end face 7 or 13 account.

FIG. 3 shows a single, axially oscillating vane 1, wherein two different vibration states are shown. The in Fig. 3 in particular on the inner platform 5 or their amplification wall 6 clearly recognizable oscillation amplitude is thereby effectively limited in the arranged in a Leitkranzverbund, inventive guide vane 1, that each of the projection 8 is received in a form-fitting manner in the receptacle 12 of an adjacent vane 1. In addition, a damping of the vibration takes place by the occurring between the inner surfaces 14 of the receptacle 12 and the side surface 9 of the projection 8 friction.

FIG. 4 shows a consisting of three vanes 1 vane segment 15th Such guide blade segments, from which an annular Leitkranzverbund is formed, serve to reinforce the individual vanes. 1 The plastic vanes 1 are not only connected by the positive engagement between the projection 8 and the receptacle 12 adjacent vanes 1 and the friction present in the contact surface with each other, but additionally at least on the side surface 9 of the projection 8 and the inner surface 14 of the receptacle 12 glued together. In addition, the guide vanes 1 also at their first and second end faces 7 and 13 be glued together. The adhesive bond between the side surface 9 of the projection 8 and the inner surface 14 of the receptacle 12 is subjected to shearing under the loads occurring during operation and is thus significantly higher load than a claimed on train / pressure adhesive bond between the first and second end face 7 and 13th

To form an annular Leitkranzverbunds several vanes segments 15 are assembled, which are not glued together to compensate for thermal expansion, but only by the Fomschluß between the projection 8 and the receptacle 12 are coupled together. However, the positive engagement causes by the friction occurring between the side surface 9 of the projection 8 and the inner surface 14 of the receptacle 12, a damping effect and thus an improvement of the dynamic vibration behavior of the guide vane. 1 In addition, due to the positive engagement, the above-described limitation of the oscillation amplitude and a sealing of the gaps between adjacent vane segments.

In each case a guide vane 1 of a vane segment 15, a bore 16 is provided in the stiffening wall 4 of the outer platform 3, provided with a bore (not shown) on the housing side and engages the vane against gas / flow forces in the circumferential direction. As shown in FIG. 4 shown, the stiffening wall 4 is locally thickened around the bore 16 around to reduce the surface pressure. The bore 16 is formed in the axial direction of the engine assembly as a slot, so that the gas or Flow forces are directed in the axial direction over the rear, hook-like fastening means 11 in the illustration and not in the engine housing over the bolt.

FIG. 5 shows the vane segment 15 of FIG. 4 in a perspective view, in which the profile of the blades 2 is hinted to recognize. It can also be seen that the dimensioning of the projection 8 and the receptacle 12 are coordinated so that the outer and inner platform 3 and 5 aligned in the assembled state. In the left part of the drawing of FIG. 5 the projections 8 are shown on the outer and inner platforms 3, 5, which are received positively in a receptacle 12 of a guide blade 1 of an adjacent guide blade segment 15 within a Leitkranzverbundes, but not glued.