EP2218880A1 - Active clearance control for gas turbines - Google Patents

Abstract

The system (1) has multiple guide vanes combined to guide vane rows and fastened to a guide vane support, and a membrane (16) subjected with fluid media. The membrane is arranged in a region adjacent to the guide vane rows, and forms a peripheral wall of a chamber (14), where the peripheral wall faces a turbine axis. The chamber is arranged in a ring segment (2) attached at the guide vane support, and channels (18) supply the fluid media to the membrane. The membrane and the chamber are arranged in a circumferential direction, where sodium is utilized as the fluid media.

Description

The invention relates to a vane carrier system, in particular for a gas turbine, with a number of vanes combined into a vane carrier and attached to a vane carrier. It further relates to a gas turbine with such a Leitschaufelträgersystem.

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.

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. For guiding the flow of the working medium, guide vanes are also usually arranged between adjacent rotor blade rows and connected to the turbine housing, which are combined into rows of guide blades. These are attached to a usually hollow cylindrical or hollow cone-shaped vane carrier.

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, with the working medium from the combustion chamber and flows into the turbine unit. Temperatures of about 1200 ° C to 1500 ° C for such gas turbines are sought and achieved.

At such high temperatures of the working medium, however, exposed to this components and components are exposed to high thermal loads. Therefore, the hot gas channel is usually lined by so-called ring segments, which form the inner wall of the hot gas channel. These are usually fastened via hooking elements on the guide blade carrier, so that the entirety of the ring segments in the circumferential direction as well as the guide blade carrier form a hollow conical or hollow cylindrical structure.

The components of the gas turbine can be deformed by different thermal expansion in different operating conditions, which has a direct influence on the size of the radial gaps between the blades and the inner wall of the hot gas duct, d. H. has the ring segments. These radial gaps are differently dimensioned when starting and stopping the turbine than in regular operation. In the construction of the gas turbine components such as guide blade carrier, inner wall or blades are always to be dimensioned so that the radial gaps are kept sufficiently large to cause damage to the gas turbine in any operating condition. However, a correspondingly comparatively generous design of the radial gaps leads to considerable losses in the efficiency.

The invention is therefore based on the object to provide a guide vane system, which allows a particularly high efficiency while maintaining the greatest possible operational safety and durability.

This object is achieved according to the invention by arranging a membrane which can be acted upon by a pressure medium in one axially adjacent region of the respective row of guide blades.

The invention is based on the consideration that a particularly high efficiency by reducing the radial gap in normal operation, d. H. For example, in full load operation of the gas turbine would be possible. In this case, a comparatively large dimension of the radial gaps is required in particular because the components of the gas turbine deform differently in different operating states. When starting and stopping the gas turbine other radial gaps are present than in regular operation. Furthermore, set in partial load operation also different column than in full load operation. Responsible for this temporal change of the radial gap are the different thermal inertia behavior of the individual components, the centrifugal force expansion and transverse contraction of the rotor, the play in the thrust bearing and the ovalization of the housing as a result of montagebedingter bias and uneven heating.

Since the size of the radial gap in operation is determined by such diverse factors, therefore, an adaptation of the radial gaps should not be done by a corresponding design in the construction of the gas turbine or the Leitschaufelträgersystems, but it should be adaptive adjustment of the radial gaps during operation of the gas turbine , The radial gaps are determined by the distance between the blade tips to the respective opposite, the guide vanes adjacent areas of the guide blade carrier. Therefore, an adaptive adaptation of the radial gaps could be achieved by a possibility for radial movement of the inner wall components of the guide vane carrier. For this purpose, in a region adjacent to the respective row of guide blades, a membrane which can be acted upon by a pressure medium, i. H. be arranged an elastic, stretchable surface.

In an advantageous embodiment, the membrane is arranged in a region of the guide blade carrier which is intended for enclosing a blade row of the gas turbine. Thereby It is ensured that an optimal positioning of the membrane takes place directly on the blades of the opposite regions of the guide blade carrier, so that a particularly good influence of the radial gaps is achieved by a different loading of the membrane with a pressure medium. As a result, an even better efficiency of the gas turbine can be achieved.

A particularly simple construction of such a membrane is possible if the membrane forms a peripheral wall of a chamber which can be acted upon by the pressure medium. The chamber then forms a pressure chamber, which can be acted upon by the pressure medium in each required amount. The membrane should form each of the turbine axis facing the surrounding wall of the chamber. Depending on the pressure in the chamber, the elastic membrane then expands more or less as the surrounding wall of the chamber and thus influences the extent of the radial gaps.

In hitherto customary gas turbines, ring segments are arranged in the regions adjacent to the guide vanes, which segments form the inner peripheral wall of the hot gas duct of the gas turbine and protect the guide vanes from damage due to the penetration of hot working medium. Therefore, in an advantageous embodiment, the pressurizable with the pressure medium chamber should be arranged in such, attached to the guide vane ring segment. This allows an adaptive reduction of the radial gaps, while the protection of the guide vane carrier against ingress of hot gas remains guaranteed.

Advantageously, channels are introduced into the guide vane carrier system for feeding the pressure medium to the membrane. These may be incorporated, for example, in the vane carrier and the ring segments, which allows easy delivery and control of the pressure on the membrane from the outside during operation of the gas turbine.

In order to be able to compensate in particular the ovalization of the guide vane carrier in a particularly targeted manner, the radial extent of the membrane should be able to be influenced separately depending on the circumferential position. For this purpose, a plurality of membranes and possibly chambers is advantageously arranged in the circumferential direction, so that a separate admission of the membranes or chambers with different pressures is possible. Thus, in the case of an ovalization of the guide blade carrier, a greater pressure can be deliberately applied to the membrane in peripheral areas with larger radial gaps that are set up so that a uniform, comparatively small radial gap is achieved over the entire circumference.

In an advantageous embodiment, the pressure medium is sodium. Sodium has particularly good heat transfer properties, a low melting point and at the same time a large liquid temperature range and is thus particularly suitable as a pressure medium.

In an advantageous embodiment, such a vane carrier is part of a gas turbine and such a gas turbine part of a combined cycle power plant.

The advantages achieved by the invention are, in particular, that an adaptive hydraulic adjustment of the radial gaps during operation is made possible by the arrangement of an elastic membrane which can be acted upon by a pressure medium in an area of a guide blade carrier adjacent to the respective row of guide blades. When the membrane is pressurized with the pressure medium, the membrane is expanded towards the blade and thus the ring diameter is reduced. This also reduces the radial gap between the blade and the housing. This makes it possible to achieve an improvement in the efficiency of the gas turbine, with the adaptation of the radial gaps only taking place during operation and not necessarily influencing the design in the construction of the gas turbine.

Such a hydraulic radial gap closure also eliminates the disadvantages of previous solutions such as an axial displacement of the entire turbine shaft to the compressor inlet, which causes a reduction of the radial column in the turbine by the conical shape of the vane support, but an increase in the gap and thus a reduction in efficiency in the compressor result. The reduction of the radial gaps by a membrane which can be acted upon by a pressure medium thus enables a targeted individual radial gap adjustment for compressor and turbine and thus enables a particularly high efficiency of the entire gas turbine.

FIG 1

einen perspektivischen Halbschnitt durch ein Leitschaufelsystem mit einer mit einem Druckmedium beaufschlagbaren Membran im entspannten Zustand,

FIG 2

das Leitschaufelträgersystem mit der Membran im Spannungszustand,

FIG 3

das Leitschaufelträgersystem aus FIG 1 in anderer Perspektive,

FIG 4

das Leitschaufelträgersystem aus FIG 2 in anderer Perspektive, und

FIG 5

einen Längsteilschnitt durch eine Gasturbine.

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

FIG. 1

a perspective half section through a guide vane system with a pressure medium can be acted upon membrane in the relaxed state,

FIG. 2

the vane carrier system with the membrane in tension,

FIG. 3

the vane carrier system FIG. 1 in a different perspective,

FIG. 4

the vane carrier system FIG. 2 in a different perspective, and

FIG. 5

a longitudinal section through a gas turbine.

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

FIG. 1 shows a part of a Leitschaufelträgersystems 1, here in particular one on a guide vane not shown here fixed ring segment 2, which forms the inner wall 4 of the hot gas channel of a gas turbine and adjacent to a number of blades not shown in detail surrounds a number of blades 6. The rotor blades 6 are arranged on a turbine shaft 8 and rotate during operation of the gas turbine.

In order to keep the efficiency of the gas turbine particularly large, the radial gap 10 between the tips 12 of the guide vanes 8 and the inner wall 4 should be kept as low as possible.

For this purpose, a number of chambers 14 is introduced into the ring segment 2, the turbine axis facing the surrounding wall is formed from a membrane 16. The membrane 16 is in the FIG. 1 shown in the relaxed state and can expand when exposed to a corresponding pressure medium. For this purpose, 2 channels 18 are introduced into the ring segment, through which the chamber 14 with a pressure medium, such as sodium, can be filled. This leads to a corresponding admission of the membrane 16.

Depending on the size of the pressure of the pressure medium while the membrane 16 is placed in a state of stress, as in FIG. 2 shown. The membrane 16 then expands in the direction of the tip 12 of the blades 6 and thus reduces the radial gap 10 between the inner wall 4 and blade 6, which has an overall higher efficiency of the gas turbine result.

In the circumferential direction, a plurality of separate chambers 14 and diaphragms 16 is provided, which makes it possible, depending on the circumferential position, to apply different pressures to the chambers 14 in order to control the radial extent of the respective membrane 16 separately. This makes it possible in particular to compensate for ovalization of the ring segments 2 caused by thermal deformation of the guide blade carrier.

The guide vane support system 1 shown with the ring segment 2 can be used both within the turbine of a gas turbine and in the compressor. The 3 and 4 show once again the representations of FIG. 1 respectively. FIG. 2 in a different perspective.

A gas turbine 101, as in FIG. 5 has a compressor 102 for combustion air, a combustion chamber 104 and a turbine unit 106 for driving the compressor 102 and a generator, not shown, or a working machine. For this purpose, the turbine unit 106 and the compressor 102 are arranged on the common turbine shaft 8, which is also referred to as a turbine runner and to which the generator or the work machine is also connected, and which is mounted rotatably about its turbine axis 109. The combustor 104, which is in the form of an annular combustor, is equipped with a number of burners 110 for combustion of a liquid or gaseous fuel.

The turbine unit 106 has a number of rotatable blades 6 connected to the turbine shaft 108. The blades 6 are arranged in a ring shape on the turbine shaft 8 and thus form a number of blade rows. Furthermore, the turbine unit 106 includes a number of stationary vanes 114 which are also annularly attached to a vane support 116 of the turbine unit 106 to form rows of vanes. The blades 6 serve to drive the turbine shaft 8 by momentum transfer from the turbine unit 106 flowing through the working medium M. The vanes 114, 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 114 or a row of vanes and a ring of blades 6 or a blade row is also referred to as a turbine stage.

Each vane 114 has a platform 118 which is arranged to fix the respective vane 114 to a vane support 1 of the turbine unit 106 as a wall element. The platform 118 is a thermally comparatively heavily loaded component, which forms the outer boundary of a hot gas channel for the turbine unit 106 flowing through the working medium M. Each blade 112 is fastened to the turbine shaft 108 in an analogous manner via a platform 119, also referred to as a blade root.

Between the spaced-apart platforms 118 of the guide vanes 114 of two adjacent rows of guide vanes, a ring segment 2 is arranged on a guide blade carrier 116 of the turbine unit 106. The outer surface of each ring segment 2 is also exposed to the hot, the turbine unit 106 flowing through the working fluid M and spaced in the radial direction from the outer end of the opposite blades 6 through the radial gap 10. The arranged between adjacent rows of stator ring segments 2 are used in particular as cover that protect the inner housing in the guide blade carrier 1 or other housing-mounting components from thermal overload by the turbine 106 flowing through the hot working medium M.

The combustion chamber 104 is configured in the exemplary embodiment as a so-called annular combustion chamber, in which a plurality of burners 110 arranged around the turbine shaft 108 in the circumferential direction open into a common combustion chamber space. For this purpose, the combustion chamber 104 is configured in its entirety as an annular structure, which is positioned around the turbine shaft 8 around.

By using a vane support system 1 of the above-mentioned embodiment in a gas turbine 101, a particularly high efficiency can be achieved with simultaneously high operational safety and service life. Due to the hydraulic radial gap optimization, the radial gaps 10 can be separately optimized in each operating state both in the compressor 102 and in the turbine unit 106 of the gas turbine 101.

Claims (9)

Guide vane system (1),
in particular for a gas turbine (101),
comprising a number of vanes (114), joined to a vane support (116) and combined into vane rows;
wherein in a region of the respective row of guide blades adjacent a pressurizable with a pressure medium membrane (16) is arranged. Guide vane carrier system (1) according to claim 1,
in which the membrane (16) is arranged in a region of the guide blade carrier (116) intended for enclosing a row of blades of the gas turbine (101). Guide vane carrier system (1) according to claim 1 or 2,
in which the membrane (16) forms the surrounding wall of the turbine axis (109) of a chamber (14) which can be acted upon by the pressure medium. Guide vane carrier system (1) according to claim 3,
in which the chamber (14) is arranged in a ring segment (2) attached to the guide blade carrier (116). Guide vane carrier system (1) according to one of claims 1 to 4,
in which channels (18) for feeding the pressure medium to the membrane (16) are introduced into the guide vane carrier system (1). Guide vane carrier system (1) according to one of claims 1 to 5,
in which in the circumferential direction a plurality of membranes (16) and optionally chambers (14) is arranged. Guide vane carrier system (1) according to one of claims 1 to 6,
where the pressure medium is sodium. Gas turbine (101) with a vane carrier system (1) according to one of claims 1 to 7. Gas and steam turbine plant with a gas turbine (101) according to claim 8.

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