EP3147456A1 - Turbine blade with groove in crown base - Google Patents

Abstract

The invention relates to a turbine blade (01) for a gas turbine with an airfoil (03), which (03) comprises a blade wall (04) and a crown bottom (07) arranged at the free end of the airfoil (03). The blade wall (04) in this case encloses at least a first and a second flow chamber (11, 12), between which (11, 12) first partition wall (08) is arranged, wherein between the first partition wall (08) and the crown bottom (07) free breakthrough (14) for connecting the first to the second flow chamber (11, 12) is present. Furthermore, at least one cooling air opening is present in the crown bottom (07). It is essential for the present invention that the cooling air opening is designed as a relief groove (21, 22a, 22b, 22c, 23), which extends at least in sections beyond the opening (14).

Description

The invention relates to a turbine blade for use in a gas turbine with a blade root and an airfoil, wherein a cooling air opening is present in the crown bottom of the airfoil.

Turbine blades for use in a gas turbine are known in various embodiments, these usually have at least one blade root for attachment in the respective turbine stage and an adjoining the blade root airfoil. The blade is in this case aerodynamically shaped, wherein the specific shape of the inventive embodiment is initially irrelevant. Here, the blade is first formed once by a blade wall, which extends from the blade root to a free end. There, as a rule, the free end of the blade is closed by means of a crown base.

Due to the high, occurring in a gas turbine temperatures, the turbine blade is further cooled in a known manner by means of cooling air. Cooling air ducts pass through the interior of the turbine blade. In this case, both embodiments are known in which the cooling air is returned to the blade root, as well as cooling air openings are arranged in the blade wall and in the crown bottom through which the cooling air can escape. Known embodiments for a turbine blade with cooling channels disclose the publications EP 1 557 553 A1 as well as the EP 2 863 013 A1 , For selective determination of the cooling air flow through the generally present in plurality cooling air openings on the blade this cooling air opening are distributed in a suitable manner and usually designed as a round hole. In addition, further embodiments are known in which the cooling air openings open in a funnel shape. Although advantageous cooling of the airfoil can already be achieved with the known embodiments, however, the problem arises that zones of different temperatures are produced by the airfoil cooling and thus local thermal stresses occur. These show up in a special way in the crown bottom, due to the high outside temperatures and the lower by the cooling air inside temperatures in the airfoil.

The object of the present invention is therefore to reduce thermal stresses due to different temperature distributions in the airfoil.

The stated object is achieved by an embodiment according to the invention according to the teaching of claim 1.

Advantageous embodiments are the subject of the dependent claims.

A generic turbine blade initially serves for use in a turbine of a gas turbine. In this case, the turbine blade has a blade root and an airfoil adjoining the blade root. In this case, the blade is curved aerodynamically, so that by means of the turbine blade effective generation of rotation in the rotor of the gas turbine can be effected. The blade is initially formed by a blade wall which extends from the blade root towards a free end. The blade wall comprises a pressure-side wall section and a suction-side wall section, both of which extend from a front edge (rounded off as a rule) of the blade to a trailing edge (usually pointed) of the airfoil. At the free end of the airfoil a crown bottom is arranged, which essentially shoots the airfoil at the free end. With regard to the specific arrangement of the crown bottom at the free end of the airfoil, it is initially irrelevant whether the Crown bottom is located directly at the end of the blade wall and at the same time forms the free end of the airfoil or whether the crown bottom is positioned back relative to the outer free end of the airfoil.

Through the blade wall with the two wall sections, the crown bottom and the blade flow, a cavity is formed, which encloses at least a first and a second flow chamber. In this regard, it is irrelevant whether further flow chambers are formed in the interior of the airfoil. At least the first flow chamber is separated from the second flow chamber by a first partition wall. In this case, both the first and second flow chambers, as well as the first partition also extend from the blade root in the direction of the free end of the airfoil. At the end of the first partition wall facing the crown bottom there is a free opening which forms a connection between the first and second flow chambers, so that the cooling air can flow from the second flow chamber through the opening into the first flow chamber. Here, it is initially irrelevant whether the breakthrough extends over the entire width of the partition wall and thus limited to the top or one with respect to the partition has smaller width and thus remains on one and / or other side a piece of the partition wall.

Furthermore, the generic turbine blade in the crown bottom at least one cooling air opening, which opens into the first and / or second flow chamber and can escape through the consequently cooling air from the interior of the turbine blade to the free end.

The object is achieved according to the invention in that instead of a further distribution of cooling air openings over the surface of the crown base at least one cooling air opening is performed as a relief groove. In this case, the relief groove has at least a minimum length, which corresponds to half the width of the partition wall. Furthermore, it is effective Reduction of the thermally induced stresses required that the relief groove extends at least in sections until beyond the breakthrough.

By introducing a relief groove having a minimum length at least corresponding to half the width of the partition, a thermally induced material expansion in the upper region of the crown base in the relief groove is made possible without it directly to the otherwise occurring high thermal stresses due to the temperature differences.

The width of the partition is measured in this case at the end of the partition adjacent to the aperture as a distance between the pressure-side wall portion and the suction-side wall portion. The length of the relief groove can be determined in two ways. On the one hand, the minimum length relates to the immediate length of at least one relief groove regardless of its shape from one end to the other end of the relief groove. However, to take into account the effectiveness of the reduction of thermally induced stresses, the shape of the relief groove in relation to the position of the partition a role. Therefore, on the other hand, the effective length of the relief groove in a direction transverse to the partition wall is measured. In the case of a single relief groove, the immediate length is thus necessarily at least as great as the effective length.

An essential factor for the formation of the thermal stresses is the presence of the partition wall, which has a lower temperature and thus lower thermal expansion due to the cooling air, whereas the outside of the crown bottom is subjected to greater material expansion due to the high temperatures prevailing in the gas turbine. A compensation of these due to the temperature differences caused material expansions is particularly advantageous possible by the at least one relief groove on both sides over the breakthrough and thus extends over the underlying partition wall.

In both simple and advantageous manner, a single relief groove is used, which extends above the opening on both sides of the partition in the crown floor.

Alternatively, it is also advantageously possible to use at least two relief grooves, which in this case are to be arranged offset next to one another above the opening. They must overlap in such a way that there is an interruption in the crown bottom in the connection from the pressure-side wall section to the suction-side wall section on the material thickness of the partition wall. The two or more relief grooves are likewise to be arranged, as in the case of the use of a single relief groove, such that they extend on both sides beyond the opening when they are viewed together.

To compensate for thermal deformations to avoid unacceptably high thermal stresses, it is also advantageous if the individual relief groove or the two or more relief grooves are located substantially in the center of the crown floor. The exact position, however, is irrelevant, provided that thermally induced expansion of the top of the crown base due to the relief groove or relief grooves is possible on both sides.

Likewise, it is advantageous if the individual relief groove or, in an alternative embodiment, the two or more relief grooves are located substantially in the middle of the dividing wall. Since, in particular, the first partition wall is the cause of the thermal stresses in the crown bottom, it is correspondingly advantageous to arrange the relief groove or the relief grooves in the middle of this first partition wall. If the length of the relief groove is extended beyond the minimum length, then it is of secondary importance Meaning, whether the extension is only on one side of the partition.

The specific orientation of the relief groove or the plurality of relief grooves is initially irrelevant, provided that a corresponding thermal expansion of the crown base on the outwardly facing side due to the presence of the relief groove is possible. However, it is particularly advantageous when using a single relief groove when the relief groove extends substantially transversely to the first partition. Not required here is a rectilinear rectangular orientation, but it is sufficient if the relief groove runs according to the course of the pressure-side wall portion and the suction-side wall portion. In this respect, for example, angle deviations of +/- 15 ° from an orientation transverse to the partition wall irrelevant. If two or more relief grooves are used, the overlapping arrangement of the relief grooves already requires a slight angular deviation from a possible transverse to the partition orientation. Nevertheless, the angle deviation should not be more than 45 °, particularly advantageous not more than 30 ° to an orientation transverse to the partition as far as possible.

The effectiveness of the relief groove is improved in a particularly advantageous manner when the at least one relief groove has an effective minimum length corresponding to the width of the partition wall. In the presence of two or more relief grooves, this consideration of the minimum effective length applies to a common consideration of the two or more relief grooves measured in a direction transverse to the first bulkhead.

The course of the relief groove or the relief grooves is initially irrelevant, with a straightforward course is chosen in the simplest way. Alternatively, it is also possible that the pressure-side wall portion facing side surface of the relief groove or the relief grooves an arcuate Course has or have according to the curvature of the pressure-side wall portion. Analogously, it is possible that the suction-side wall portion facing side surface of the relief groove or the relief grooves has a curved course corresponding to the curvature of the suction-side wall portion or have. In this respect, the relief groove follows the course of the pressure-side or suction-side wall section.

With regard to the use of the exiting from the relief cooling air and taking into account the prevailing in the airfoil cooling air flow from the second flow chamber to the first flow chamber, it is also advantageous if the relief groove is performed inclined. For this purpose, it is advantageous if the pointing away from the blade root end of the relief groove, d. H. the end of the relief groove facing the outside, closer to the pressure-side wall portion than the end of the relief groove facing the blade root, d. H. the breakthrough adjacent end of the relief groove, is located.

Furthermore, it is advantageous for limiting the flow in the relief groove and taking into account the manufacturing possibilities when the one relief groove or at least one of the two or more relief grooves expands from a smallest free cross-section towards one end or both ends of the respective relief groove , In this respect, the flow from the first flow chamber is limited by the smallest free cross section, whereby the widening of the relief groove simplifies its production.

With regard to the arrangement of the crown base on the blade wall, various options are available. In a first and simple embodiment, the crown bottom is located exactly at the end of the blade wall and thus forms the end of the blade. In contrast, it is advantageous if the crown bottom opposite the end of the blade wall is reset, and insofar at least partially the pressure-side wall portion and / or the suction-side wall portion projects beyond the crown floor. In a further alternative, it is also possible to arrange the crown bottom at the end of the blade wall, however, to provide further ribs or webs or the like above the crown bottom.

The relief groove according to the invention is used in a particularly advantageous manner in a partition, which is located at a front of the trailing edge disposed first flow chamber. The trailing edge adjacent to the first flow chamber connects the pressure-side wall portion to the suction-side wall portion.

Furthermore, it is advantageous to use a relief groove if at least one second partition wall and one third flow chamber are present. In this case, the second partition also adjoins the second flow chamber and is located opposite the first partition wall in connection of the pressure-side wall section with the suction-side wall section. Above the partition is also a second free breakthrough. Adjacent to the second partition opposite to the second flow chamber is a third flow chamber, wherein cooling air can flow from the third flow chamber to the second flow chamber through the second passage.

In this case, the third flow chamber adjoins the leading edge in an advantageous manner, which connects the pressure-side wall section with the suction-side wall section opposite the trailing edge.

The size of the second breakthrough is initially irrelevant, which advantageously has the size of the first breakthrough. However, it is particularly advantageous if the second free opening has at least twice the size of the first free opening. In this case, both the second free breakthrough one compared to the width of the second Partition have a small width than extending in an advantageous manner, the second breakthrough to the width of the second partition and this limits insofar upward on the side facing the crown bottom side.

Furthermore, it is advantageous if there is also a free third breakthrough at the blade end facing the first partition, so that the cooling air from the third flow chamber via the second breakthrough in the second flow chamber and proportionately on the first breakthrough and majority on the third breakthrough can flow into the first flow chamber.

Furthermore, a coating is advantageously applied to the crown bottom. On the one hand, it can be provided that a coating is applied before the generation of the relief groove. On the other hand, it is advantageous if a coating is applied to the top of the crown provided with the relief groove. The second variant offers the particular advantage that the coating can be applied at least partially on the outside ends of the side surfaces of the relief groove, whereby its gap width is reduced. Thus, the cooling air flow can be reduced by the relief groove, wherein the desired expansion clearance is maintained to a sufficient extent.

In the following figures, an exemplary turbine blade is shown with relief grooves sketched by way of example.

FIG 1

eine Turbinenschaufel für ein Beispiel der Erfindung;

FIG 2

einen Schnitt durch das Schaufelblatt mittig zwischen dem druckseitigem und dem saugseitigem Wandabschnitt;

FIG 3

eine Draufsicht auf das Schaufelblatt mit einem ersten Ausführungsbeispiel einer Entlastungsnut;

FIG 4

eine Draufsicht auf das Schaufelblatt mit einer alternativen Anordnung von Entlastungsnuten;

FIG 5

einen Schnitt durch das Schaufelblatt parallel zur ersten Trennwand mit einer schräg gestellten Entlastungnut;

FIG 6

einen Schnitt analog FIG 5 mit einer sich aufweitenden Entlastungsnut.

Show it:

FIG. 1

a turbine blade for an example of the invention;

FIG. 2

a section through the airfoil midway between the pressure-side and the suction-side wall portion;

FIG. 3

a plan view of the airfoil with a first embodiment of a relief groove;

FIG. 4

a plan view of the airfoil with an alternative arrangement of relief grooves;

FIG. 5

a section through the airfoil parallel to the first partition wall with an inclined relief groove;

FIG. 6

a section analog FIG. 5 with a widening relief groove.

The FIG. 1 shows by way of example a turbine blade 01 with a blade root 02 and a subsequent blade on the blade airfoil 03. The embodiment of the blade root 02 is irrelevant to the present invention and in that respect will not be discussed in detail in this regard. The airfoil 03 comprises first of all the blade wall 04, which 04 is formed in this embodiment by a pressure-side wall section 05 (lying in front of the drawing plane) and a suction-side wall section 06 (lying in the drawing plane behind), which 05, 06 both from a leading edge to extend to a trailing edge. Here, the blade wall 04 encloses a cavity, which in turn is formed by flow chambers 11, 12, 13. At the free end of the airfoil 03 is the crown bottom 07, which 07 is slightly reset in this embodiment relative to the end of the airfoil 03. Within the airfoil 03, the cavity is separated by a first separating element 08 and a second separating element 09 into a first flow chamber 11 between the trailing edge and the first dividing wall 08 and a second flow chamber 12 between the first dividing wall 08 and the second dividing wall 09 and into a third flow chamber 13 divided between the second partition wall 09 and the front edge. On the top side, the relief groove 21 in the crown bottom 07 can be seen.

The FIG. 2 now schematically shows a section through the blade 03 in a view cut centrally between the pressure-side wall portion 05 and the suction-side wall portion 06. First, the blade wall 04 with the leading edge and the trailing edge can be seen. On the upper side is the crown bottom 07, which 07 is slightly set back relative to the end of the blade wall 04. Within the airfoil 03 are the first partition 08 and the second partition 09, which 08, 09 subdivide the cavity in the interior of the airfoil 04 in the first flow chamber 11, the second flow chamber 12 and the third flow chamber 13. In this exemplary example, it is provided that a flow of cooling air flows from the third flow chamber 13 into the second flow chamber 12 and subsequently into the first flow chamber 11. For the realization of the transition of the cooling air from the first flow chamber 11 to the second flow chamber 12 is located between the second partition 09 and the crown bottom 07, a second free opening 15th

To reduce the thermal stresses in the crown bottom 07 according to the invention, a first free opening 14 is initially arranged in the first partition wall 15 at the end facing the crown bottom 07. Furthermore, there is at least one relief groove 21 in the crown bottom 07. This 21 extends centrally through the opening 14 and thus allows thermal expansion of the upper side of the crown bottom 07 while holding the pressure-side wall section 05 with the suction-side wall section 06 through the first partition wall 08.

The FIG. 3 now shows a plan view of the airfoil 03, wherein first again the blade wall 04 with the pressure-side wall portion 05 and the suction-side wall portion 06 can be seen. Inside the airfoil 03 Below the crown floor 07 are the first partition 08 and the second partition 09. Above the first partition 08 is centrally disposed in the crown floor 07 relief 21. This 21 has in this embodiment has a length L, measured transversely to the partition, which L approximately equal to the width B of the partition.

In the following FIG. 4 is in a further embodiment analogous to FIG. 3 outlined a plan view of the blade 03. In contrast to the previous embodiment, instead of a single relief groove 21 now three parallel and mutually offset relief grooves 22a, 22b and 22c are used in the crown floor. These 22, 22b2, 22c extend in this case also over the first partition wall 08 and in this case are arranged centrally to the first partition wall 08. The length L of the considered three relief grooves 22a, 22b and 22c measured transversely to the first partition wall 08 is hereby slightly larger than the width B of the first partition wall 08th

In the following FIG. 5 By way of example, the relief groove 21 is sketched in a section parallel to the dividing wall 08. In contrast to a straight-line perpendicular to the crown bottom 07 possible embodiment of the relief groove 21, the relief groove 21 is inclined in this embodiment. In this case, the upper-side, outwardly facing end of the relief groove 21 is located approximately centrally in the crown bottom 07 between the pressure-side wall section 05 and the suction-side wall section 06. On the side of the opening 14 above the first partition wall 08, however, the relief groove 21 is located closer to the suction-side wall section ,

In FIG. 6 a further embodiment of a relief groove 23 is sketched, the representation analog FIG. 5 is executed. In this embodiment, the relief groove 23 centrally between the two ends of the relief groove on a smallest cross-section, starting from which the relief groove 23 in both directions, ie inwards and expands outside. This allows on the one hand a limitation of the cooling air and on the other hand this simplifies the production of the relief groove 23rd

Claims (13)

Turbine blade (01) for a gas turbine,
with a blade root (02) and with an aerodynamically curved airfoil (03), which (03) has a blade wall (04) and a crown bottom (07) arranged at the free end of the airfoil (03), the blade wall (04) having a pressure side and a suction-side wall portion (05, 06) and at least a first and a second flow chamber (11, 12) encloses, between which (11, 12) a wall portions (05, 06) connecting first partition wall (08) is arranged, the first dividing wall (08) has a free opening (14) for connecting the first to the second flow chamber (11, 12) at the end facing the crown bottom (07), and at least one cooling air opening is present in the crown bottom (07),
characterized,
that the cooling air hole as a relief groove (21, 22a, 22b, 22c, 23) is carried out, which (21, 22a, 22b, 22c, 23) at least a minimum length (L) corresponding to half the width (B) of the partition (08) and extends at least in sections until beyond the opening (14). Turbine blade (01) according to claim 1,
characterized,
in that a single relief groove (21, 23) is provided, which (21, 23) extends beyond the aperture (14) on both sides. Turbine blade (01) according to claim 1,
characterized,
in that at least two relief grooves (22a, 22b, 22c) are arranged offset next to one another, which (22a, 22b, 22c) extend beyond the opening (14) on both sides. Turbine blade (01) according to one of claims 1 to 3,
characterized,
that the relief grooves (22a, 22b, 22c) or the single relief groove (21, 23) the center of the crown base (07) are arranged / is. Turbine blade (01) according to one of claims 1 to 4,
characterized,
in that the relief grooves (22a, 22b, 22c) or the individual relief groove (21, 23) are arranged centrally to the dividing wall (08). Turbine blade (01) according to one of claims 1 to 5,
characterized,
that the relief grooves (22a, 22b, 22c) measured together or individual relief groove (21, 23) at least a minimum length (L) transverse to the partition wall (08) corresponding to the width (B) of the partition (08) have / has. Turbine blade (01) according to one of claims 1 to 6,
characterized,
that the wall sections (05, 06) zugwandten side surfaces of the relief grooves (22a, 22b, 22c) or the relief groove (21, 23) have a rectilinear course or an arcuate profile corresponding to the curvature of the respective wall portion (05, 06) / comprising. Turbine blade (01) according to one of claims 1 to 7,
characterized,
that from the blade root (02) pioneering end of the relief groove (21, 22a, 22b, 22c, 23) closer facing the pressure side wall portion (05) than the blade (02) end of the relief groove (21, 22a, 22b, 22c, 23 ) is located. Turbine blade (01) according to one of claims 1 to 8,
characterized,
in that at least one relief groove (21, 22a, 22b, 22c, 23) widens starting from a smallest free cross section towards one end or both ends of the relief groove (21, 22a, 22b, 22c, 23). Turbine blade (01) according to one of claims 1 to 9,
characterized,
that at least sections of the pressure-side and / or the suction-side wall portion (05, 06), in particular the blade wall (04), the crown bottom (07) surmounted. Turbine blade (01) according to one of claims 1 to 10,
characterized,
that the first flow chamber (11) is disposed at a the pressure-side wall portion (05) with the suction-side wall portion joined (06) trailing edge. Turbine blade (01) according to one of claims 1 to 11,
characterized,
that adjacent to the second flow chamber (12) a second partition wall (09) and opposite to the first flow chamber (11) includes a third flow chamber (13) is arranged. Turbine blade (01) according to claim 12,
characterized,
that between the second partition wall (12) and the crown bottom (07), a second free aperture (15) is present, which at least the size, in particular at least twice the size of the first free aperture (14).

Images