EP3369892B1 - Contouring of a blade row platform - Google Patents

Description

The present invention relates to a blade grid segment, a blade grid, a platform and a blade channel of a turbomachine and a turbomachine.

Fluid flow machines (such as gas and steam turbines) regularly have a flow channel for carrying a fluid through. The flow channel, which is also referred to as an annular space, is bounded radially inward by the shaft of a rotor and radially outward by a housing; the terms "radial" as well as "axial" and "circumferential direction" and terms derived therefrom are used in this Unless otherwise stated, font always refers to a (intended) axis of rotation of the rotor.

Blade grids are arranged in the annular space of a turbomachine (for which the term "blade ring" is also common). They each include guide vanes or rotor blades, which lie one behind the other in the circumferential direction at essentially regular intervals, as well as associated platforms, which are also referred to as "cover plates" and which each have an inflow-side and an outflow-side platform edge. These platform edges delimit the platform surface facing the blades (or blade blades) in the axial direction.

In this document, the "upstream" platform edge is the edge of the platform through which the (axial) main flow passing through the annular space of the turbomachine first passes, and the “downstream” platform edge is the other edge. The terms "downstream" and "upstream" relate accordingly to the main axial flow direction and only to the axial position, i.e. regardless of a possible shift in the circumferential direction: In particular, a point in this document is to be understood as "downstream of the leading edges", if it is arranged axially offset in the main flow direction for a direct connection of the leading edges on the platform surface.

The pressure side of one blade and the suction side of an adjacent blade each delimit a so-called blade channel in the circumferential direction. In the radial direction, this vane channel is delimited within the turbomachine by so-called side walls. These are formed on the one hand by the platforms and on the other hand by radially opposite sections: in the case of rotor blades, such a side wall is a radially outer section (in particular of the housing), in the case of guide vanes a radially inner section (in particular a Rotor hub).

The section of the platform surface that is created in the axial direction by the direct connections of the leading edges or the trailing edges of adjacent blades on the platform surface (or by a projection of a straight connection of the named edges in the radial direction onto the platform surface) and in the circumferential direction by their suction or pressure side is limited, is referred to in this document as "blade intermediate strip". The width of the blade intermediate strip in the circumferential direction is called the "pitch" of the blade grid. In particular, it can be measured as the distance between the leading edges of adjacent blades in the circumferential direction on the platform surface. The depth of the space between the blades in the axial direction, that is to say the distance, measured parallel to the intended axis of rotation of the turbomachine, between the leading edges of the blades and their trailing edges is referred to as the "grid width".

A fluid flow guided through a flow channel is regularly influenced by the surfaces of the side walls. Flow layers that run close to these surfaces are deflected more strongly than flow layers further away from the side walls because of their lower speed. This creates a secondary flow which is superimposed on an axial main flow and which in particular leads to eddies and pressure losses.

To reduce the secondary flows, contours in the form of elevations and / or depressions are often introduced into the side walls.

A large number of such so-called "sidewall contours" are known from the prior art. The patents or patent applications are exemplary EP 2 487 329 B1 , EP 2 787 172 A2 , and EP 2 696 029 B1 named by the applicant.

In addition, from the publication EP 1 126 132 A2 a flow channel with a side wall is known which has a radial recess in the region of the leading edges of the blades. This extends in the axial direction over the majority of the flow channel and only ends shortly before or even behind the trailing edge. This is intended to locally enlarge the surface of the flow area between the inflow and outflow edges, which is intended to improve the efficiency of the rotor.

The EP 2 372 088 A2 discloses an integrally manufactured turbine blade disk which has a ring with upstream and downstream edges, between which rotor blades and - in the region of the leading edges of the rotor blades - depressions in the surface of the ring are arranged.

The DE 10 2010 007 985 A1 discloses a steam turbine with stator blade profiles, behind which a slot for moisture absorption is arranged. From the WO 98/44240 A1 a flow channel with a wall having a groove structure is known and from US Pat US 2008/232968 A1 a sidewall contouring for a row of blades of a turbomachine. The EP 2 372 102 A2 discloses a platform section for a rotor of a gas turbine and the WO 2015/092204 A1 a turbine blade with a platform.

The object of the present invention is to provide an alternative technology for a turbo machine with which secondary flows can be reduced in an advantageous manner.

The object is achieved by a blade grid segment according to claim 1, a blade grid according to claim 11, a blade channel according to claim 12, a platform according to claim 13 and a turbomachine according to claim 14. Advantageous embodiments are disclosed in the subclaims, the description and the figures.

A blade grid segment according to the invention for a blade grid of a turbomachine comprises a platform and at least two (adjacent) blade blades which, according to the above, define an intermediate blade strip with an axial grid width through their inflow and outflow edges on the platform surface. The platform has an upstream platform edge which has a contour with a depression. In the axial direction, this recess extends into the blade intermediate strip by at most 10% of the grid width. In particular, the depression can be arranged completely upstream of the leading edges, that is to say not protrude into the intermediate blade strip.

In relation to the platform edge on the inflow side, the depression is to be understood as a local expression of a line that results from the cross-section of a two-dimensional line Platform surface (flat) recess along the platform edge results. In this document, such a “depression” is to be understood as a local formation in the platform surface in which the latter extends towards the side facing away from the blade blades. The designation (as well as terms such as "lowered" or the like) is based on an orientation or a coordinate system in which the blades extend "up" from the platform surface and a depression accordingly in the opposite direction (down "down") ) leads.

The depression is thus arranged completely in the interior of a surface strip of the platform surface, the outflow-side delimitation of which extends in the axial direction by at most 10% of the grid width downstream of the leading edges; in particular in relation to this limitation, the depression is lowered in all its points (whereby an edge of the depression can be regarded as not belonging to it). In the contour of the platform edge on the inflow side, the recess is preferably formed continuously. According to a special embodiment, the outflow-side delimitation does not even run further than (at most) 5% of the grid width downstream of the leading edges of the blades.

A blade grid segment according to the invention can be in one piece or assembled. In particular, the platform can be in one piece or comprise two or more parts, from each of which one of the impeller blades protrudes, or the platform can be designed as at least one separate component that is or can be arranged between the impeller blades. Accordingly, a platform according to the invention is set up to adjoin a blade in the circumferential direction on each side and, together with the blades (none, one or both of which can be permanently formed on the platform), together a blade grid segment according to the invention according to one of those disclosed in this document Form embodiments.

A blade grid according to the invention comprises at least one blade grid segment according to the invention in accordance with one of the embodiments disclosed in this document. A turbomachine according to the invention comprises one or more blade grids according to the invention.

A blade channel according to the invention leads through a blade channel according to the invention Blade grid segment according to one of the embodiments disclosed in this document is therefore limited by such a blade grid segment and a side wall opposite its platform (facing the platform surface). In particular, the vane channel is delimited in the circumferential direction by the pressure side of one of the vane blades of the vane grid segment and by the suction side of the (adjacent) other of the vane blades opposite this.

A blade grid segment according to the invention, a blade grid according to the invention, a blade channel according to the invention, a platform according to the invention and a turbomachine according to the invention each enable an improvement in the secondary flows and thus a reduction in losses in the respective hub or housing area. In this way, a high degree of efficiency of the turbomachine can be achieved.

The blade grid segment or the blade grid or the flow channel or the platform can in particular be part of a low-pressure turbine. The vane grid can be a guide vane grid or a rotor blade grid, so the blade blades can each be guide blades or rotor blade blades. The platform can be designed to delimit a vane channel through the vane lattice segment to the radially inward or radially outward direction.

The platform edge on the inflow side is preferably designed to be used (at least essentially) adjacent to a further (separate) element (for example the hub or the housing or another vane grille) in the turbomachine. It can be set up to form a section of a wall of a gap through which cooling fluid is or can be introduced into the annular space of the turbomachine. In the circumferential direction, the platform edge on the inflow side (which can comprise sections of several parts of a multi-part platform) is preferably delimited by the (circumferential direction) positions of the leading edges of the two blades; these boundaries can have a physical expression (for example, in that the platform ends in them in perimeter viewing) or they can only be defined or defined abstractly to define the platform edge on the upstream side. In particular, the platform edge on the inflow side preferably has an extent (or length) in the circumferential direction which is (essentially) equal to the pitch.

An embodiment of the present invention has proven to be particularly advantageous in which the depression extends along the platform edge on the inflow side (preferably continuously) over at least 50% of the pitch.

The depression preferably has a positive distance (> 0) from the pressure side of one of the blades and / or from the suction side of the other blade, so that it does not touch the respective side. The recess can be spaced equally or differently from the two blades. In particular, the distance from the depression to the leading edge of one vane (e.g. the one on whose pressure side the vane interspace region is adjacent) can be greater or smaller than the distance between the recess and the leading edge of the other vane. Such an axial asymmetry can do justice to a different influencing of the flow by the suction and pressure side of the blades in the sense of a reduction of secondary flows.

In particular, an embodiment of the present invention has proven to be advantageous in which the upstream platform edge (or its contour) is designed asymmetrically to its radial central axis, that is, a radial axis that runs through the center of the upstream platform edge.

In a preferred embodiment variant of the present invention, the platform surface comprises a surface area which is arranged between the depression and a pressure side of one (the first) of the airfoils. Such a surface area is preferably covered by the platform edge on the inflow side. The contour of the platform edge on the inflow side then comprises an edge of the surface area, which is referred to below as the “pressure-side” surface area. In particular, an edge section of the platform edge on the inflow side, in which it covers the surface area on the pressure side, can extend in the circumferential direction preferably over at least 10% or at least 20% of the pitch. Each point of the depression is preferably lowered compared to each point of the pressure-side surface area (in the radial direction).

Analogously, the platform surface can comprise a surface area which is arranged between the depression and a suction side of the other (second) of the airfoils. Such a surface area is preferably formed by the platform edge on the inflow side detected. The contour of the platform edge on the inflow side then comprises an edge of the surface area, which is referred to below as the “suction-side” surface area. In particular, an edge section of the platform edge on the inflow side, in which it covers the surface area on the suction side, can extend in the circumferential direction preferably over at least 10% or at least 20% of the pitch. Each point of the depression is preferably lowered compared to each point of the suction-side surface area (in the radial direction).

A combination of these embodiments has proven to be particularly advantageous, in which the platform surface thus includes both a pressure-side and a suction-side surface section (possibly with the further properties mentioned). According to one embodiment, an edge section in which the inflow-side platform edge encompasses the suction-side surface area is larger than an edge section of the inflow-side platform edge in which it encompasses the suction-side surface area; in another variant it is the other way round, and in a further embodiment both sections are of the same size.

Outside the recess, the platform surface can be designed to be uncontoured.

In the following, preferred embodiments of the invention are explained in more detail with reference to drawings. It goes without saying that individual elements and components can also be combined differently than shown. Reference symbols for elements that correspond to one another are used across the figures and may not be described anew for each figure.

Figur 1:

ein abgewickeltes Schaufelgittersegment einer exemplarischen Ausführungsform der vorliegenden Erfindung in Draufsicht; und

Figur 2:

ein abgewickeltes Schaufelgittersegment einer alternativen exemplarischen Ausführungsform der vorliegenden Erfindung in Draufsicht.

They show schematically:

Figure 1:

a developed vane grid segment of an exemplary embodiment of the present invention in plan view; and

Figure 2:

a developed airfoil segment of an alternative exemplary embodiment of the present invention in plan view.

In Figure 1 is schematically an exemplary (developed) embodiment of a Vane grid segment 1 according to the invention shown in plan view; the viewing direction corresponds to the radial direction (outwards or inwards, depending on whether the platform 10 is part of an outer or an inner side wall). The vane grid segment comprises adjacent vane blades 20, 30 and a platform 10 according to the invention, which has a platform surface 12, an inflow-side platform edge 10a (with reference to the intended axial main flow direction X) and an outflow-side platform edge 10b. The upstream platform edge 10a can - although not shown - comprise sections of several parts of a multi-part platform. It is limited by the (circumferential) positions of the leading edges 23, 33 of the two blades 20, 30; In particular, the extent (or length) of the platform edge 10a on the inflow side in the circumferential direction is thus equal to the pitch t.

The pressure side 21 of one blade 20 and the suction side 32 of the other blade 30 delimit a blade intermediate strip 11 in the circumferential direction U of the associated blade grid; In the axial direction, this intermediate blade strip is limited by a straight connection 11a of the leading edges 23, 33 running along the platform in plan view (i.e. a corresponding projection) and by a corresponding connection 11b of the trailing edges 24, 34 of the blade blades 20, 30. The result is an (axial) grid width g.

The platform surface has a recess 13 which is captured by the platform edge 10a on the inflow side. In cross-section (along a plane to which the intended axis of rotation is normal) it follows that the inflow-side platform edge 10a has a contour with the recess 13 (in the form of a depression) (not shown directly in the figure, but implied by it) .

In the example shown, the recess is arranged completely upstream of the blade intermediate strip 11. It extends continuously along the platform edge 10a on the inflow side (that is to say continuously) over an extent d which is greater than 50% of the division t. In this case, an outflow-side delimitation 13b of the recess 13 has an axial distance, which changes with its course, from the inflow-side platform edge 10a; According to another embodiment (not shown), an outflow-side delimitation of the recess 13 could extend essentially without axial deviations in the circumferential direction U, in a radial projection onto the The platform surface thus run parallel to the platform edge 10a on the inflow side (not shown).

The platform surface has a pressure-side surface section 14 arranged between the pressure side 21 of the airfoil 20 and the recess 13 and reaching the front platform edge 10a as well as a suction-side surface section 15 arranged between the suction side 32 of the airfoil 30 and the recess 13 and reaching the front platform edge . The recess 13 is completely lowered in the radial direction compared to each point of the pressure-side section 14 and each point of the suction-side section 15 (which is again not visible in the figure due to the representation as a plan view).

The pressure-side surface section 14 reaching up to the front platform edge 10a extends in a continuous edge section 14a along the front platform edge 10a. Analogously, the suction-side section 15 reaching the front platform edge extends in a continuous edge section 15a along the front platform edge 10a. Im in the Figure 1 The embodiment shown, the edge portion 15a is smaller than the edge portion 14a. In particular, the upstream platform edge 10a is asymmetrical to its radial central axis (not shown in the figure), that is to say to a radial axis which runs through the center of the upstream platform edge 10a.

Figure 2 shows schematically a developed alternative embodiment of a blade grid segment 1 'according to the invention in a plan view. It has like that in Figure 1 The vane grid segment 1 shown has vane blades 20, 30 and a platform 10 according to the invention with an upstream platform edge 10a (based on the intended, axial main flow direction X) and a downstream platform edge 10b.

The platform surface of the platform 10 of the blade lattice segment 1 ′ comprises a recess 13 ′ which runs along the platform edge 10a on the inflow side and is covered by the platform edge 10a on the inflow side. In cross-section (along a plane to which the intended axis of rotation is normal) there is also a contour encompassing the recess 13 'in the form of a contiguous depression in the inflow side platform edge 10a (again not shown directly in the figure, but implied by it) .

An outflow-side delimitation 13'b of the recess 13 'also has in FIG Figure 2 The example shown shows a distance in the axial direction that changes with its course from the platform edge 10a on the inflow side; According to other exemplary embodiments (not shown), an outflow-side delimitation of the recess extends essentially without axial deviations in the circumferential direction (ie runs parallel to the inflow-side platform edge 10a in the projection onto the platform surface). The recess 13 'is arranged in the interior of a surface strip of the platform surface 12', the downstream boundary of which runs in the circumferential direction and is located downstream of the leading edges 23, 33 of the blades 20, 30 by the axial distance a. According to the invention, a 0.1g applies, where g is the axial grid width. The recess 13 ′ thus protrudes at most 10% of the axial grid width g into the blade intermediate strip 11.

The platform surface has a pressure-side surface section 14 'arranged between the pressure side 21 of the airfoil 20 and the depression 13' and reaching the front platform edge 11, as well as a suction-side surface section 14 'arranged between the suction side 32 of the airfoil 30 and the recess 13' and reaching the front platform edge Surface section 15 '. The recess 13 'is completely lowered in the radial direction compared to each point of the pressure-side section 14' and each point of the suction-side section 15 '(which in turn is not visible in the figure due to the representation as a top view).

The surface section 14 'on the pressure side reaching the front platform edge extends in an edge section 14'a continuously along the front platform edge 10a. Analogously, the suction-side section 15 'reaching the front platform edge extends continuously in an edge section 15'a along the front platform edge 10a. Im in the Figure 2 The embodiment shown, the edge section 15'a is larger than the edge section 14'a; In a special embodiment, the edge section 15'a can be at least 1.5 times or even at least twice as large as the edge section 14'a.

A blade grid segment 1, 1 'for a blade grid of a turbomachine is disclosed, which comprises a platform 10 and at least two blade blades 20, 30 which, through their inflow and outflow edges 23, 33, 24, 34, form an intermediate blade strip 11 with an axial grid width on the platform surface determine g. An upstream Platform edge 10a has a contour with a recess 13, 13 '. In the axial direction, this recess 13, 13 ′ extends into the blade intermediate strip 11 by at most 10% of the grid width g.

A corresponding platform, a blade grid, a blade channel and a turbo-machine are also disclosed.

Reference number

1, 1 '

Blade grille segment

10

platform

10a

Upstream platform edge

10b

Downstream platform edge

11

Shovel strips

11a

Upstream boundary of the blade intermediate strip

11b

Downstream limitation of the blade intermediate strip

12, 12 '

Platform surface

13, 13 '

deepening

13b, 13'b

Downstream limitation of the depression

14, 14 '

surface section on the pressure side

14a, 14'a

Edge section of the surface section on the pressure side

15, 15 '

suction-side surface section

15a, 15'a

Edge section of the suction-side surface section

20, 30

Shovel blade

21st

Pressure side of the airfoil 20

23, 33

Leading edge

24, 34

Trailing edge

32

Suction side of the airfoil 30

a

axial distance of the downstream boundary of the recess 13 'from the leading edges 23, 33 of the blades

d

Extension of the recess 13, 13 'in the circumferential direction

G

axial grid width

t

Pitch

U

Circumferential direction

X

intended axial main flow direction

Claims (14)

1. Blade cascade segment (1, 1') for a blade cascade of a turbomachine, the blade cascade segment comprising a platform (10) having a platform surface (12) and an upstream platform edge (10a), and least two airfoils (20, 30) which, by means of leading and trailing edges (23, 33, 24, 34) thereof, determine an intermediate blade strip (11) having an axial cascade width (g) on the platform surface (12), the upstream platform edge (10a) having a contour which has a recess (13, 13') in the shape of a depression, the recess (13, 13') extending in the axial direction into the intermediate blade strip (11) by at most 10% of the cascade width (g), characterized in that the recess (13, 13') extends continuously along the upstream platform edge (10a), over at least 50% of the pitch distance (t).
2. Blade cascade segment according to claim 1, wherein the platform surface (12) has a pressure-side surface portion (14) which is arranged between a pressure side (21) of a first airfoil (20) of the at least two airfoils (20, 30) and the recess (13) and extends as far as the upstream platform edge (10a), and has a suction-side surface portion (15) which is arranged between a suction side (32) of a second airfoil (30) of the at least two airfoils (20, 30) and the recess (13) and extends as far as the upstream platform edge (10a), wherein, in comparison with each point of the pressure-side portion (14) and each point of the suction-side portion (15), the recess (13) is completely lowered in the radial direction.
3. Blade cascade segment (1, 1') according to claim 1, wherein the platform surface comprises a pressure-side surface region (14, 14') which is arranged between a pressure side (21) of one of the airfoils (20) and the recess (13, 13').
4. Blade cascade segment (1, 1') according to either claim 2 or claim 3, wherein an edge portion (14a, 14'a) in which the upstream platform edge (10a) covers the pressure-side surface region (14, 14') comprises at least 10% or at least 20% of the pitch distance (t).
5. Blade cascade segment (1, 1') according to claim 1, wherein the platform surface comprises a suction-side surface region (15, 15') which is arranged between a suction side (32) of one of the airfoils (30) and the recess (13, 13').
6. Blade cascade segment (1, 1') according to either claim 2 or claim 5, wherein an edge portion (15a, 15'a) in which the upstream platform edge (10a) covers the suction-side surface region (15, 15') comprises at least 10% or at least 20% of the pitch distance (t).
7. Blade cascade segment according to any of the preceding claims, wherein the recess (13) is arranged completely upstream of the leading edges (23, 33).
8. Blade cascade segment according to any of the preceding claims, wherein the blade cascade is a guide vane cascade or a rotor blade cascade.
9. Blade cascade segment according to any of the preceding claims, wherein a downstream boundary (13'b) of the recess extends substantially in parallel with the upstream platform edge (10a).
10. Blade cascade segment according to any of the preceding claims, wherein the upstream platform edge (10a) is asymmetrical to the radial central axis thereof.
11. Blade cascade having two or more blade cascade segments (1, 1') according to any of the preceding claims.
12. Blade channel of a turbomachine that is delimited by a blade cascade segment (1, 1') according to any of claims 1 to 10, and by a lateral wall which is opposite the platform (10) of the blade cascade segment.
13. Platform (10) for a blade cascade segment according to any of claims 1 to 10, wherein the platform is designed to be adjacent to the at least two airfoils (20, 30) in the circumferential direction (U).
14. Turbomachine having at least one blade cascade according to claim 11.

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