EP1557533B1 - Cooling of a turbine blade with a raised floor between blade and tip - Google Patents

Description

The invention relates to a turbine blade with a turbine blade towards the tip, along a blade axis, arranged in the form of a hollow profile and a blade tip in the form of a hollow profile, wherein the blade at its turbine blade end facing side in the hollow profile transverse to the blade axis first Has wall and the blade tip on its side facing away from the turbine blade end side has a hollow profile transverse to the blade axis extending second wall, wherein the first wall and the second wall opposite to form a cooling means carrying double bottom opposite. The invention also relates to a gas turbine having an annular passage gas flow channel extending along an axis of the gas turbine for impinging a working fluid and a plurality of blade stages arranged along the axis, wherein a blade stage comprises a number of annularly arranged turbine blades radially extending into the flow passage , which can be acted upon by a cooling fluid.

In a gas turbine of the above type occur in the flow channel temperatures that can be in the range between 1000 ° C and 1400 ° C, when it is acted upon by a working fluid in the form of hot gas. Turbine blades which are exposed to the same for receiving the kinetic energy of the working fluid are to be designed in view of such loads. A turbine blade may be in the form of a rotor blade attached to a rotor and to the rotor. Furthermore, a turbine blade may be formed in the form of a fixedly attached to the housing of a turbine vane. Similarly, in both types of blades, in particular the tip of the turbine blade is exposed to high thermal loads. When a blade occurs In addition, the high mechanical stress caused by the rotational movement added.

The outer shape of the blade tip is primarily determined by an aerodynamic task. Furthermore, manufacturing reasons play an essential role in shaping. In addition, for the further embodiment a turbine blade, and in particular the blade tip, due to the high thermal loads, a cooling engineering design relevant. To achieve long service life, the tip must be cooled. Without cooling the blade tip, it would oxidize rapidly. However, the life requirements for vanes, and in particular buckets, are still increasing. This means that the component temperature must be kept within reasonable limits by using a cooling fluid. Moreover, in the cooling engineering design of a turbine blade, in particular a blade, in which in particular the design of the blade tip is relevant, the use of cooling fluid should be designed efficiently in order to increase the overall efficiency and performance of a gas turbine.

For cooling a turbine blade and in particular a turbine blade tip a number of measures have been proposed. The US 4,519,745 For cooling an airfoil in the form of a hollow profile, a corrugated division of the inner wall of the hollow profile is provided. For cooling a blade tip a plurality of channels and a recess in a bearing receiving surface for the blade tip is provided, so that the blade tip can be cooled from the outside with a transported through the channels and the recess cooling fluid.

The DE 198 131 73 A1 discloses a cooled blade of a gas turbine, the airfoil in the hollow profile carries a plurality of webs, which serve as swirling means. A shroud or deck or blade stiffening band is further disposed at the end of the blade. A cooling air opening and a cooling air outlet communicate with the hollow profile around this shroud. Furthermore, the shroud is deformed and has a narrow central portion, so that this shroud is made lightweight. Similarly, many shroud cooling air openings formed parallel to each other such that a shape is provided, by means of which the cooling air can be discharged from the cooling air outlet to the outside.

Furthermore, the shows US 6,164,914 a turbine blade with a squealer like a double bottom.

It is also known to intensively cool a blade tip by providing holes in the hollow profile of the blade tip itself in order to cool a blade tip as part of a film cooling process. In this case, a cooling fluid is driven out of the bores and settles in the form of a film cooling on the outer surface of the hollow profile. In the turbine blades mentioned above, there is the problem that on the one hand, the cooling of a blade tip can be made more efficient, but on the other hand, the cooling technology design of a blade tip is too complex compared to the blade, as that they could be manufactured advantageously produced.

It would be desirable to increase the performance and the overall efficiency of a gas turbine, a turbine blade, in which the use of cooling medium can be made as efficient as possible and also easier to manufacture.

At this point, the invention begins, whose object is to provide a turbine blade and a gas turbine with a turbine blade, in which an improved cooling of the blade tip is provided, which can be produced in a particularly simple manner.

With regard to the turbine blade, the object is achieved by the invention by means of the turbine blade mentioned above, in which according to the invention the blade tip and the blade are made separately and the second wall a closure means for a core holding bore in the first wall.

The cooling means are provided in particular for cooling the blade tip and are measures that support improved heat transfer between the blade and the cooling medium. The essential finding of the invention is that the raised floor formed by the first and the second wall is particularly effective for mounting cooling means as the heat transfer improving measure and thus can be used to a particularly efficient cooling of the blade tip. The invention is based on the consideration that the geometry of a double bottom is a particularly suitable basis for a cooling technical means. Different types of cooling-technical means come into question, all of which can be interpreted very effectively within the framework of the geometry of said double floor.

The invention proposes that the airfoil and the blade tip, as part of the manufacturing process, are separated, e.g. in a casting process. In this way, it is particularly easy to produce the above double floor and thus available for cooling measures available cavity. Casting technically, the formation of such a geometry usually presents a problem if the turbine blade as a whole had to be cast. The arrangement of the above cavities and said cooling means can be particularly easily effected by the separate production of the blade and blade tip.

In a separate casting process for the airfoil and the blade tip is in the context of the casting process for the airfoil expediently in the first wall, a holding bore for the airfoil, also referred to as core holding bore provided. In a separately cast show The tip of the fel tip expediently carries the second wall with a stopper or another closure means for the core holding bore, so that in an assembled state of the blade and the blade tip, the closure means on the second wall closes the core holding bore in the first wall.

Advantageous developments of the invention can be found in the dependent claims and provide in particular advantageous ways to design the turbine blade with regard to the cooling of the blade tip with a whole series of further advantages over previously customary measures. Advantageously, the first and / or the second wall is a wall which extends across the entire cross section of the hollow profile in the interior of the hollow profile transversely to the blade axis, preferably perpendicular to the blade axis, ie horizontally. Thus, the false bottom formed according to the concept of the invention and carrying cooling means provides for the formation of a cavity between the first wall and the second wall.

Conveniently, the cooling means is an agent selected from the group consisting of: turbulator, impingement coolant and film coolant. That is expedient come to increase the cooling efficiency of the principle of turbulence ren, impingement cooling and film cooling or other measures to increase the cooling effect of the cooling medium used or to lower the external hot gas temperature individually or in combination for use.

Advantageously, to form the turbulator means, the first wall and / or the second wall carries a number of turbulence elements. Such swirling elements serve to swirl a cooling fluid when the turbine blade is exposed to a cooling fluid. For this purpose, in particular, the turbulence of the cooling fluid between the first wall and the second wall, ie in the above-mentioned cavity, expedient. Suitably, an arrangement of nipples, dimples or other suitable formations, e.g. Webs, etc., on the hollow profile or the walls. Further swirling elements also have an advantageous effect in terms of heat dissipation from the blade tip, such as e.g. a suitable arrangement of ribs or joints.

Conveniently, to form an impingement coolant, the first wall carries a number of impingement cooling apertures which, upon impingement of the turbine blade with cooling fluid, allow the cooling fluid to impinge on the second wall. For this purpose, a cooling fluid from the blade to the blade tip is first passed through the first wall and then optionally additionally through the second wall. An impingement cooling opening in the first wall is characterized in particular in that it is arranged at an angle in the range of approximately 0 ° relative to the blade axis, that is to say perpendicular to the second wall. Proper spatial proximity of the second wall to the first wall results in a cooling fluid passing through the impingement cooling holes with a suitable pressure impinging on the second wall and cooling the latter and the blade tip particularly efficiently as part of the impingement cooling. This measure can be made even more effective in particular by an arrangement of Verwirbelungselementen above type on the second wall.

Conveniently, to form a film coolant, the second wall and / or the airfoil of the blade tip carries a number of film cooling apertures which, upon exposure to the turbine blade with cooling fluid, will produce a film of cooling fluid on the wall structure of the blade tip. In particular, such film cooling openings thus lead obliquely from the inside to the outside in the direction of the turbine blade end and guide cooling fluid to the inner wall and / or outer wall of the blade tip. A film cooling opening is therefore arranged essentially at an angle of ≦ 90 ° and significantly greater than 0 ° relative to the blade axis in the second wall. In addition, film cooling openings for cooling the airfoil may possibly also be provided on the first wall. Further measures can be realized by further cooling openings or cooling channels.

According to an advantageous development of the invention, the wall structure of the blade tip may have a higher porosity and / or a smaller wall thickness than the wall structure of the blade leaf. This applies above all to the outer walls of the blade tip and the blade. This has the advantage that the mass of a blade tip to be cooled is kept as low as possible. Furthermore, it is possible to manufacture the airfoil and the blade tip from different materials in order to obtain particular advantages, e.g. low weight or high thermal conductivity of the blade tip or e.g. To be able to realize high strength of the blade at the same time.

According to a particularly preferred embodiment of the invention, it has proven to be particularly advantageous in the context of the above-explained concept that the blade and the blade tip, in the context of the manufacturing process, separately, for example in a casting process, is produced. In this way, it is particularly easy to produce the above double floor and thus available for cooling measures available cavity.

Conveniently, to form a film coolant, the second wall and / or the airfoil of the blade tip carries a number of film cooling apertures which, upon exposure to the turbine blade with cooling fluid, will produce a film of cooling fluid on the wall structure of the blade tip. In particular, such film cooling openings thus lead obliquely from the inside to the outside in the direction of the turbine blade end and guide cooling fluid to the inner wall and / or outer wall of the blade tip. A film cooling opening is therefore arranged essentially at an angle of ≦ 90 ° and significantly greater than 0 ° relative to the blade axis in the second wall. In addition, film cooling openings for cooling the airfoil may possibly also be provided on the first wall. Further measures can be realized by further cooling openings or cooling channels.

According to an advantageous development of the invention, the wall structure of the blade tip may have a higher porosity and / or a smaller wall thickness than the wall structure of the blade leaf. This applies above all to the outer walls of the blade tip and the blade. This has the advantage that the mass of a blade tip to be cooled is kept as low as possible. Furthermore, it is possible to produce the blade and the blade tip from different materials in order to realize special advantages such as low weight or high thermal conductivity of the blade tip or eg high strength of the blade at the same time.

Furthermore, it has also proved to be advantageous in the context of the above preferred embodiment of the invention that the airfoil and the blade tip are cast from different materials. In particular, the airfoil is cast from a high strength material. In particular, the blade tip is cast from a highly heat-conductive material. This type of training is based on the consideration that the blade should be designed especially with regard to mechanical requirements, especially due to the rotational load of a blade. In contrast, especially the blade tip is to be interpreted in terms of cooling technical measures due to the higher thermal load compared to an airfoil.

Advantageously, the blade tip is soldered to the blade in a joining process and / or welded. A mechanical connection is also possible in addition or as an alternative.

The invention also leads to a gas turbine of the type mentioned, in which the turbine blades are formed above explained type.

• FIG 1 eine schematisierte Darstellung einer mit Kühlfluid beaufschlagten Laufschaufel an einem Rotor einer Gasturbine,
• FIG 2 eine Laufschaufel mit einem Schaufelblatt und einer Schaufelspitze gemäß dem Oberbegriff des Anspruchs 1, wobei das Schaufelblatt und die Schaufelspitze getrennt hergerstellt werden,
• FIG 3 eine Laufschaufel mit einem Schaufelblatt und einer Schaufelspitze gemäß einer bevorzugten Ausführungsform der Erfindung.

Embodiments of the invention are described below with reference to the drawing. This is not intended to represent the embodiments significantly, but the drawing, where appropriate for explanation, executed in a schematized and / or slightly distorted form. With regard to additions to the teachings directly recognizable from the drawing reference is made to the relevant prior art. In detail, the drawing shows in:

• FIG. 1 1 is a schematic representation of a rotor blade acted upon by a cooling fluid on a rotor of a gas turbine,
• FIG. 2 a bucket with an airfoil and a blade tip according to the preamble of claim 1, wherein the airfoil and the blade tip are made separately,
• FIG. 3 a blade with an airfoil and a blade tip according to a preferred embodiment of the invention.

FIG. 1 FIG. 1 shows a rotor blade 1 attached to a rotor 3 of a gas turbine, not shown. The rotor blade 1 is one of a number of annularly arranged, radially extending in a flow channel 5 of the gas turbine turbine blades, which form in its entirety a blade stage, which in the annular cross section of the flow channel 5 extends. A variety of such annular blade stages is as well as the Flow channel arranged along an axis 7 of the gas turbine, not shown. The flow channel 5 is acted upon by a working fluid 9 in the form of a hot gas mixture, which relaxes under the drive of the moving blade 1 and thus emits its kinetic energy while rotating the rotor to drive a generator, not shown.

The rotor blade 1 points toward the turbine blade end 29, along its blade axis 11 one after the other arranged on a platform portion 13, arranged in the form of a hollow profile blade 15 and arranged in the form of a hollow blade blade tip 17. The platform region 13 in this case comprises a blade platform for limiting the flow channel 5 and a blade root, which are not shown in detail. The blade 1 is as schematically indicated, acted upon via a channel system 19 with a cooling fluid 21. The cooling system 19 also has suitable dosing means 23 which can control the supply 25 of the cooling fluid 21 into the blade and which are indicated here only schematically by the reference numeral 23.

The cooling of the blade 1 extends in particular to the blade 15 and the blade tip 17th

In detail is in FIG. 2 an embodiment of the design of the cooling system 19 in the region 27 between the blade 15 and the blade tip 17 is shown. FIG. 3 shows the embodiment according to the invention. In this case, the transition region 27 comprises in particular the airfoil 15 on its side facing the turbine blade end 29 of the turbine blade 1 and the blade tip 17 on its side facing away from the turbine blade end 29 of the rotor blade 1.

While the above-described concept of the invention is particularly useful for the embodiments shown herein a blade, it should nevertheless be clear that the described concept can be implemented equally within the framework of a gas or steam turbine vane.

FIG. 2 shows a blade according to the preamble of claim 1, wherein the blade and the blade tip are made separately 31 in the transition region 27 of FIG. 1 in a perspective sectional view. The rotor blade 31 has an airfoil 33 designed as a hollow profile and a blade tip 35 designed as a hollow profile. The hollow profile of the blade 33 in this case has a cavity 37 and the hollow profile of the blade tip 35 in this case has a cavity 39, the part of in FIG. 1 are shown cooling system 19 and can be acted upon with cooling fluid. The airfoil 33 has at its in FIG. 1 shown turbine blade end 29 of the turbine blade 31 side facing a transverse to the blade axis 11 extending first wall 41. The blade tip 35 has at its from the in FIG. 1 shown turbine blade end 29 of the turbine blade 1 facing away from a transverse to the blade axis 11 extending second wall 43. The first wall 41 and the second wall 43 are opposed to form a double bottom 45. Through the formation of a double bottom 45, a cavity 47 is formed between the first wall 41 and the second wall 43, both of which extend horizontally over the entire cross section of the hollow profile. The double bottom 45 carries thereby cooling technical means, which are explained in detail below.

In the present embodiment, the second wall 43 carries a number of swirling or turbulator elements in the form of nipples 49 and dimples 51. A nipple 49 is formed in the cavity 47 on the second wall 43. A dimple 51 expands the cavity 47 in the form of a recess in the second wall 43. The said swirling elements serve primarily to swirl a cooling fluid which flows through the impingement cooling openings 53 in the first Wall 41 can be supplied to the cavity 47. In particular, the impact cooling openings 53 are arranged perpendicular to the second wall 43. In addition, the first wall 41 is arranged so close to the second wall 43, that a correspondingly pressurized cooling medium bounces on the second wall 43 via the impingement cooling openings 53 and the blade tip 35 effectively cools via the second web 43 in the context of impingement cooling. By means of said turbulence elements in the form of nipples 49 and dimples 51, this illustrated impingement cooling is enhanced. That is, heat received in the blade tip is effectively dissipated by the cooling fluid.

In addition, the second wall 43 has a first number of film cooling holes 55 and a second number of film cooling holes 57. A first film cooling opening 55 is aligned obliquely from the inside to the outside in the direction of the turbine blade end 29 of the turbine blade 31 and can thus afford a film of cooling fluid on the inner wall 59 of the blade tip 35 in a suitably gentle manner.

An even more obliquely arranged second film cooling opening 57 makes it possible to produce a further film of cooling fluid on the outer wall 61 of the blade tip 35 via the same mechanism.

In order to keep the mass of the blade tip 35 to be cooled as low as possible, the wall structure of the blade tip 35 has a wall thickness 63 which is smaller than the wall thickness 65 of the wall structure of the blade 33. In addition, the wall structure of the blade tip 35 has the same reason a higher porosity, not shown, than the wall structure of the airfoil 33.

In the case of the rotor blade 31 illustrated here, the double bottom 45 of the rotor blade 31, which comprises a cavity 47, is advantageously provided with cooling-technical means, which it allow to effectively cool the blade tip 35 and thus save cooling medium, which can increase the overall efficiency of a gas turbine. In particular, the in FIG. 2 illustrated, blade 31 advantageously produce in the context of a manufacturing process, which provides a separate casting process, and thus a separate production of the airfoil 33 on the one hand and the blade tip on the other. The separately cast blade tip 35 is then soldered to the separately cast airfoil 33 to form the double bottom 45 and the cavity 47. The particularly advantageous double bottom 45 with cavity 47 and cooling means can thus be particularly useful to achieve via a separate casting process for blade tip 35 and blade 33 as explained. In addition, advantageously, that the airfoil 33 can be cast from a different material than the blade tip 35. Thus, the airfoil 33 is expediently cast in terms of its greater mechanical stress of a high-strength material, while the blade tip 35 with respect to their higher thermal stress of a highly heat-conductive material , For example, a cobalt material is poured.

A blade according to claim 1, is in FIG. 3 In particular, with a view to simplifying the manufacturing process in addition to the in FIG. 2 having shown blade further elements. The remaining features of FIG. 2 are in FIG. 3 provided with the same reference numerals.

In the blade 71 shown here, the airfoil 73 provides a core-holding bore 77 in the first wall 79, which in the present case is closed by a plug 81 in the second wall 83 of the blade tip 85 as soon as the separately prepared blade tip 85 and the separately manufactured airfoil 73 abut one another are joined. Because the here explained challenging geometry of the blade tip 85 does not have to be poured together with the blade 73, the cast of the blade 71 is simplified.

Furthermore, with the attached tip 85, the core holding hole 77 shown here, which is available by casting, can be closed particularly reliably. The connection between the blade tip 85 and the blade 73 is in the present case produced by a particularly suitable welding method in the joining region 87. The connecting surfaces between blade tip 85 and blade 73 in the joining region 87 can be produced in a particularly simple and precise manner. The closure of the core holding hole 77 is carried out in the context of a specially measured fit of the plug 81 on the core holding hole 77th

Both at the in FIG. 2 shown blade 31 as well as in the FIG. 3 shown blade 71 can in a separate production of airfoil 33, 73 and blade tip 35, 85 relatively complex cooling means still in a relatively simple manner in a casting technology manufacturing process in the blade profile 31, 71 provide and thus a particularly efficient cooling of the blade tip 35, Reach 85.

In summary, a turbine blade according to claim 1 is designed for more efficient cooling of a blade tip 85.

Claims (9)

1. Turbine blade (71) comprising an aerofoil (73), arranged in the form of a hollow profile along a blade axis (11) towards the turbine blade end (29), and comprising a blade tip (85) in the form of a hollow profile,
   in which turbine blade (71) the aerofoil (73), on its side facing the turbine blade end (29), has a first wall (79) running in the hollow profile transversely to the blade axis (11), and
   the blade tip (85), on its side facing away from the turbine blade end (29), has a second wall (83) running in the hollow profile transversely to the blade axis (11), wherein
   the first wall (79) and the second wall (83) are opposite one another, with a raised floor (45) having cooling means being formed,
   characterized in that
   the blade tip (85) and the aerofoil (73) are separately produced and
   the second wall (83) has a closure means for a core exit hole in the first wall (41, 79).
2. Turbine blade (71) according to Claim 1, characterized in that the cooling means is one of the group consisting of turbulator means, impingement-cooling means and film-cooling means.
3. Turbine blade (71) according to Claim 1 or 2, characterized in that, to form a turbulator means, the first wall (79) and/or the second wall (83) has a number of nipples, dimples, ribs, seams or other swirl elements.
4. Turbine blade (71) according to one of Claims 1 to 3, characterized in that, to form an impingement-cooling means, the first wall (79) has a number of impingement-cooling openings which, when cooling fluid is admitted to the turbine blade, enable the cooling fluid to impinge on the second wall (83).
5. Turbine blade (71) according to one of Claims 1 to 4, characterized in that, to form a film-cooling means, the second wall (83) and/or the hollow profile of the blade tip (85) has a number of film-cooling openings (55) which, when cooling fluid is admitted to the turbine blade (71), enable a film of cooling fluid to be produced on the wall structure of the blade tip (85).
6. Turbine blade (71) according to one of Claims 1 to 5, characterized in that the wall structure of the blade tip (85) has higher porosity and/or a smaller wall thickness than the wall structure of the aerofoil (73).
7. Turbine blade (71) according to one of Claims 1 to 6, characterized in that the aerofoil (73) and the blade tip (85) are produced from different materials, the aerofoil (73) being cast from a high-strength material and the blade tip (85) being produced from a material having high thermal conductivity.
8. Turbine blade (71) according to one of Claims 1 to 7, characterized in that the blade tip (85) is joined to the aerofoil (73), the blade tip (85) and the aerofoil (73) in particular being brazed or welded in place.
9. Gas turbine (1) comprising a flow duct (5) which extends along an axis (7) of the gas turbine (1) and has an annular cross section for the admission of a working fluid (9), and comprising a number of blade stages arranged along the axis, a blade stage having a number of turbine blades (71) according to one of the preceding claims, which turbine blades (71) are arranged in an annular manner and extend radially into the flow duct (5) and to which a cooling fluid can be admitted.

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