EP2031302A1 - Gas turbine with a coolable component - Google Patents

Abstract

In a gas turbine (1) with a number of each combined to blade rows, on a turbine shaft (8) arranged blades (12) and with a number of each grouped to Leitschaufelreihen, with a turbine housing (16) connected vanes (14) and with a Number of hot gas-carrying components, in which a hot gas flow space (36) bounding outer wall (28) is integrated in each case a number of cooling channels (32) for acting on a cooling medium, which is itself in view of the limited space and a low efficiency aspired for Pressure loss sufficient cooling effect on the thermally highly stressed areas of the respective component can be achieved safely. For this purpose, at least one of the cooling channels (32) integrated into the outer wall (28) of the respective component is provided with turbulence-generating structural elements (34) on its inner wall (38) facing away from the hot gas flow space (36).

Description

The invention relates to a gas turbine with a number of each combined into rows of blades, arranged on a turbine shaft blades and a number of guide vanes combined, connected to a turbine housing vanes and with a number of hot gas components, in which a hot gas flow space bordering outer wall is integrated in each case a number of cooling channels for acting on a cooling medium.

Gas turbines are used in many areas to drive generators or work machines. In this case, the energy content of a fuel is used to generate a rotational movement of a turbine shaft. For this purpose, the fuel is burned in a combustion chamber, compressed air being supplied by an air compressor. The working medium produced in the combustion chamber by the combustion of the fuel, under high pressure and at high temperature, is guided via a turbine unit arranged downstream of the combustion chamber, where it relaxes to perform work. For guiding the hot gas flow into the turbine unit, a number of suitable hot gas-conducting components are provided, for example the combustion chamber per se or its outflow region and this downstream transition piece opening into the turbine unit.

To generate the rotational movement of the turbine shaft, a number of rotor blades, which are usually combined into blade groups or rows of blades, are arranged thereon and drive the turbine shaft via a momentum transfer from the working medium. To guide the working fluid in the turbine unit also usually connected between adjacent blade rows are connected to the turbine housing Leitschaufelreihen.

In the design of such gas turbines in addition to the achievable power usually a particularly high efficiency is a design target. An increase in the efficiency can be achieved for thermodynamic reasons basically by increasing the outlet temperature at which the working fluid from the combustion chamber and flows into the turbine unit. Therefore, temperatures of about 1200 ° C to 1300 ° C are sought for such gas turbines and achieved.

At such high temperatures of the working medium, however, exposed to this components and components are exposed to high thermal loads. In order nevertheless to ensure a comparatively long service life of the affected components with high reliability, cooling of the affected components, in particular of rotor blades and / or guide vanes of the turbine unit or of the hot gas-conducting components, is usually provided. These affected components, in particular the hot gas-carrying components such as combustion chamber walls or transition pieces, are therefore usually designed coolable, in particular, an effective and reliable cooling of the flow space of the hot gas directly limiting component walls should be ensured. For cooling, the affected outer wall of the respective component usually has a cooling channel integrated into the wall material for the application of a coolant such as, for example, air or steam.

In this way, a reliable cooling system for the respective component wall can be provided with comparatively simple means, wherein also thermally highly stressed zones of the component are suitable acted upon by coolant. However, it can prove to be problematic that, with regard to the wall thicknesses required for structural stability, the flow cross-sections achievable for the cooling channels are only limited. Too small a flow cross-section can help, among other things, that the flow resistance during the flow of the coolant through the cooling channel is undesirably high, which can have an effect-reducing effect. In order to limit this disadvantage, the flow rate of the coolant could generally be reduced, which, on the other hand, adversely affects the desired cooling effect again.

The invention is therefore an object of the invention to provide a gas turbine of the type mentioned above, in which even with regard to the limited space and a low efficiency for low pressure loss sufficient cooling effect on the thermally highly stressed areas of the respective component can be achieved safely.

This object is achieved according to the invention in that at least one of the cooling channels integrated into the outer wall of the respective component is provided with turbulence-generating structural elements at its inner wall facing away from the hot gas flow space.

The invention is based on the consideration that, in order to ensure a sufficient cooling effect on the mentioned components with acceptable pressure loss, the maximization of the parameter heat transfer / (pressure loss) ⁿ should always be taken into account as a design target for the respective cooling channels, the exponent n being one of the dependent component and their specific conditions of use is dependent coefficient. The maximization of this characteristic as the design target can be promoted by maximizing the heat transfer coefficient of the surface of the respective cooling channel. In order to obtain a particularly large value of this heat transfer coefficient, the inner wall of the respective cooling channel should be provided with turbulence-generating structures in order to generate a particularly intimate contact between the coolant and the channel wall and thus a particularly effective heat exchange between the channel wall by the turbulence thus flowing in the coolant channel and to ensure coolant. Just about the targeted generation of turbulence or vortices in the coolant, this high heat transfer is achievable, without at the same time an excessively high pressure loss in the coolant is to be accepted. In order to achieve a comparatively homogeneous temperature profile in such an arrangement while avoiding too high caused by temperature differences induced thermal stresses in the materials, such a high wall-side heat transfer but not for that channel wall, which in turn is directly in contact with the hot gas zone, but rather targeted be provided for this opposite channel wall. This reliably avoids an excessively high temperature gradient in the wall material.

A particularly thin channel wall between the cooling channel and the hot gas flow space can be achieved if that wall of the cooling channel which faces the hot gas flow space is free of turbulence-generating structures.

The desired high heat transfer between the coolant and the channel wall can be achieved in an advantageous embodiment by providing mixer fins, rib structures or other suitably selected structural elements projecting from the wall material into the flow region of the coolant as turbulence-generating structural elements to the respective channel wall or wall zone. In a particularly advantageous embodiment, however, local wall recesses, also referred to as so-called "dimples" or concave indentations in the wall surface, are provided as turbulence-generating structural elements. Such local wall recesses or "dimples" may have various outer contours such as circular, square, triangular, hexagonal or the like, various basic shapes such as spherical, cylindrical or the like, and geometry parameters such as embossing depths, effective surface area and the like. Compared to other turbulence-generating structural elements such impressions or local wall recesses have the particular advantage that Such structures, the specific heat transfer at the interface can be significantly increased, without thereby increasing the pressure loss in particular measure. In particular, the pressure loss to be taken into account for a desired increase in the heat transfer through such local wall depressions is usually only about half as large as in the case of structures protruding from the wall surface.

A particularly uniform flow course and thus a particularly uniform heat transfer with limited pressure loss, also with regard to the swirling or turbulence generated as intended in the flowing coolant, can be achieved by arranging the turbulence-generating structural elements in a further advantageous embodiment in an associated surface region of the inner wall in a regular grid arrangement. As a grid arrangement, a hexagonal grid is provided in a further advantageous embodiment, in which a particularly high packing or area density of the structural elements can be achieved. The turbulence-generating structural elements are adapted in a further advantageous embodiment in its outer contour to the grid structure. When selecting a hexagonal grid for the grid arrangement, a hexagonal outer contour for the structural elements is thus provided in this embodiment.

In a particularly advantageous embodiment, said turbulence-generating structuring means are used in a cooling channel of a combustion chamber wall or of a transition piece of the gas turbine connected downstream of the combustion gas side on the hot gas side.

The advantages achieved by the invention are in particular that by attaching turbulence-generating structural elements and in particular of concave wall depressions on the inner wall of an integrated into the outer wall of the hot gas leading component cooling channel with limited pressure loss, a particularly high heat transfer and thus even with limited space for the cooling system a particularly effective cooling of thermally highly loaded zones can be guaranteed. In particular, by the arrangement of these structural elements on the side facing away from the hot gas flow chamber inner wall of the cooling channel is also an excessively high temperature gradient in the wall material immediately adjacent to the flow space of the hot gas safely avoided.

In principle, various suitable processes can be considered for producing the surface structures, such as, for example, casting, etching, machining, cold forming by pressing or the like. In view of the possibly limited accessibility of the affected surfaces in the inner wall region of the cooling channels is particularly advantageous in the manner of a so-called Völbstrukturierung production by the use of a "natural folding", the materials under suitable environmental conditions under exposure to external hydrostatic pressure.

FIG 1

einen Halbschnitt durch eine Gasturbine,

FIG 2

einen Ausschnitt aus einem Längsschnitt der Gasturbine nach FIG 1 mit der Darstellung eines Kühlkanals in einer Außenwand einer Brennkammer, und

FIG 3

einen Ausschnitt aus der Oberfläche einer Innenwand des Kühlkanals nach FIG 2.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

FIG. 1

a half-section through a gas turbine,

FIG. 2

a section of a longitudinal section of the gas turbine after FIG. 1 with the representation of a cooling channel in an outer wall of a combustion chamber, and

FIG. 3

a section of the surface of an inner wall of the cooling channel after FIG. 2 ,

Identical parts are provided with the same reference numerals in all figures.

The gas turbine 1 according to FIG. 1 has a compressor 2 for combustion air, a combustion chamber 4 and a turbine 6 for driving the compressor 2 and a generator, not shown or a work machine. For this purpose, the turbine 6 and the compressor 2 are arranged on a common, also called turbine rotor turbine shaft 8, with which the generator or the working machine is connected, and which is rotatably mounted about its central axis 9.

The combustion chamber 4 is equipped with a number of burners 10 for the combustion of a liquid or gaseous fuel.

The turbine 6 has a number of rotatable blades 12 connected to the turbine shaft 8. The blades 12 are arranged in a ring on the turbine shaft 8 and thus form a number of blade rows. Furthermore, the turbine 6 comprises a number of fixed vanes 14, which are also fixed in a ring shape with the formation of rows of vanes on an inner casing 16 of the turbine 6. The blades 12 serve to drive the turbine shaft 8 by momentum transfer from the turbine 6 flowing through the working medium M. The vanes 14, however, serve to guide the flow of the working medium M between two seen in the flow direction of the working medium M consecutive blade rows or blade rings. A successive pair of a ring of vanes 14 or a row of vanes and a ring of blades 12 or a blade row is also referred to as a turbine stage.

Each vane 14 has a platform 18, also referred to as a blade root, which is arranged to fix the respective vane 14 on the inner housing 16 of the turbine 6 as a wall element. The platform 18 is a thermally comparatively heavily loaded component, which forms the outer boundary of a hot gas channel for the working medium M flowing through the turbine 6. Each blade 12 is attached to the turbine shaft 8 in an analogous manner via a platform 20, also referred to as a blade root.

Between the spaced-apart platforms 18 of the guide vanes 14 of two adjacent rows of guide vanes is in each case a guide ring 21 on the inner housing 16 of the turbine 6 is arranged. The outer surface of each guide ring 19 is also exposed to the hot, the turbine 6 flowing through the working fluid M and spaced in the radial direction from the outer end 22 of the blade 12 opposite it through a gap. The guide rings 19 arranged between adjacent guide blade rows serve in particular as cover elements which protect the inner wall 16 or other housing mounting parts from thermal overload by the hot working medium M flowing through the turbine 6.

To achieve a comparatively high efficiency, the gas turbine 1 is designed for a comparatively high outlet temperature of the working medium M emerging from the combustion chamber 4 from about 1200 ° C. to 1300 ° C. In order to make this possible, at least some of the rotor blades 12 and the guide vanes 14, as well as hot gas-carrying components, the outer wall 28 of the combustion chamber 4 and a transition piece downstream of this cooled by cooling air as the cooling medium.

These are, as in the enlarged view in FIG. 2 can be seen, in the outer wall 28 of the combustion chamber 4 cooling channels 32 integrated, which are suitably acted upon with cooling air as the cooling medium. An analogous embodiment is also provided for the outer wall of the combustion chamber 4 downstream Überströmstücks.

In the design and refinement of the cooling channels 32 integrated into the outer wall 28 of the respective hot gas-carrying component, particular consideration is given to achieving a particularly high efficiency of cooling with the pressure loss as limited as possible, especially with regard to the limited space available for the cooling system due to the wall thickness. To make this possible, is the respective Cooling channel 32 is provided on its inner wall with turbulence-generating structural elements 34, which increase the heat transfer from guided in the cooling passage 32 coolant into the wall with only a limited increase in the pressure loss. As the illustration in FIG. 2 can be removed, these turbulence-generating structure elements 34 are arranged in the embodiment exclusively on the side facing away from the hot gas flow chamber 36 inner wall 38 of the cooling channel 32. In the exemplary embodiment, the inner wall 40 of the cooling channel 32 facing the hot gas flow space 36 is kept free of such structural elements, so that an excessively high temperature gradient in the region between the hot gas flow space 36 and the inner wall 40 of the cooling channel 32 facing the latter can be avoided. In other words, the inner wall 40 of the cooling channel 32 is smooth or even.

As the representation of a surface section of the inner wall 38 of the cooling channel 32 according to FIG. 3 can be removed, the turbulence-generating structure elements 34 are configured in the embodiment as local wall recesses or concave depressions 42, so-called "dimples". In principle, these local depressions can have any suitable outer contours such as, for example, circular, square or the like. In the exemplary embodiment, however, the recesses are provided with a hexagonal or hexagonal outer contour. Furthermore, the recesses 42 are arranged in a regular grid structure on the surface, wherein in the embodiment, a hexagonal grid structure is selected. Thus, the recesses 42 are adapted in their outer contour to the grid structure.

Claims (7)

A gas turbine (1) comprising a number of rotor blades (12), each arranged in a row of blades, and having a number of guide vanes (14) combined with a turbine housing (16) and with a number of guide vanes hot gas-carrying components, in whose hot gas flow space (36) delimiting outer wall (28) is integrated in each case a number of cooling channels (32) for acting on a cooling medium,
wherein at least one of the cooling channels (32) is provided at its from the hot gas flow space (36) facing away from the inner wall (38) with turbulence-generating structure elements (34). Gas turbine (1) according to claim 1, in which the wall of the cooling channel (32),
which faces the hot gas flow space, is free of turbulence-generating structural elements. Gas turbine according to claim 1 or 2,
in which mixer fins are provided as turbulence-generating structural elements (34). Gas turbine according to claim 1, 2 or 3,
in which local wall recesses (40) are provided as turbulence-generating structural elements (34). Gas turbine according to one of claims 1 to 4,
in which the turbulence-generating structural elements (34) are arranged in an associated surface region of the inner wall (38) in a regular grid arrangement, preferably in the manner of a hexagonal grid. Gas turbine according to claim 5,
in which the turbulence-generating structural elements (34) are adapted in their outer contour to the grid structure. Gas turbine according to one of claims 1 to 5,
in which the turbulence-generating structural elements (34) are arranged in a cooling channel (32) of a combustion chamber wall or of a transition piece (30) arranged downstream of the hot gas side (30).

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