EP2599957A1 - Cooling fin system for a cooling channel and turbine blade - Google Patents

Abstract

The system has a cooling rib (8) arranged on a blade inner side (3) of a cooling passage protruding from the blade inner side such that cooling fluid (18) flowing in the cooling passage flows transversely onto the cooling rib. The cooling rib has a downstream rear side (12), which runs profiled towards the blade inner side such that the cooling fluid flow passes the rear side free of breakaway during operation of a turbine blade. The cooling rib includes a front side (9), which faces away from the rear side and projects perpendicular from the latter blade inner side.

Description

The invention relates to a cooling rib system for a cooling channel of a turbine blade.

A gas turbine has a turbine in which hot gas, which has previously been compressed in a compressor and heated to a combustion chamber, is depressurized for work recovery. For high mass flows of the hot gas and thus for high power ranges of the gas turbine, the turbine is designed in Axialbauweise, wherein the turbine is formed by a plurality of successively arranged in the flow direction blade rings. The blade rings have circumferentially disposed blades and vanes, the blades being mounted on a rotor of the gas turbine and the vanes secured to the housing of the gas turbine.

The thermodynamic efficiency of the gas turbine is the higher, the higher the inlet temperature of the hot gas into the turbine. In contrast, there are limits with regard to the thermal load capacity of the turbine blades. Thus, it is desirable to provide turbine blades, which have sufficient mechanical strength despite the highest possible thermal load for the operation of the gas turbine. For this purpose, corresponding materials and material combinations are available for the turbine blades, which, however, according to the current state of the art, only allow an insufficient expansion of the potential for increasing the thermal efficiency of the gas turbine. To further increase the allowable turbine inlet temperature, it is known to cool the turbine blades during operation of the gas turbine, whereby the turbine blade itself is exposed to a lower thermal load, as would be the case without the cooling due to the thermal load of the hot gas. It is known to make the turbine blade hollow, wherein the interior of the turbine blade serves as a cooling passage through which cooling fluid flows during operation of the gas turbine. Conventionally, the cooling fluid is air drawn from the compressor. As the cooling fluid flows through the cooling channel, convection removes heat from the turbine blade, thereby reducing the contact temperature at the surface of the turbine blade. As a result, the thermal load of the turbine blade is reduced, whereby the hot gas temperature can be increased accordingly, without the thermal load of the turbine blade is unacceptably high. To increase the convection effect, it is also known to provide the blade inside with cooling fins, via which an additional heat dissipation is achieved by the turbine blade.

The object of the invention is to provide a cooling fin system for a cooling channel of a turbine blade, wherein the turbine blade is effectively cooled with the cooling fin system.

The object is solved with the features of claim 1. Advantageous embodiments thereof are given in the further claims.

The cooling fin system according to the invention for a cooling channel of a turbine blade has at least one cooling rib which is arranged on the blade inner side of the cooling channel projecting therefrom, so that the cooling rib has flowing transversely through cooling fluid flowing in the cooling channel, wherein the cooling rib has a downstream rear side in such a profiled manner towards the inner side of the blade, that the flow of cooling fluid during the operation of the turbine blade passes through the rear side without a release.

The turbine bucket has the cooling passage in which the cooling fluid for cooling the turbine bucket flows during operation thereof, whereby the turbine bucket is cooled by the cooling fluid. This can be relaxed with the turbine blade hot gas at such a high temperature, without the Cooling would lead to an impermissibly high thermal load on the turbine blade. The cooling of the turbine blade via convection by means of the cooling fluid, whereby the Konvektionswirkung is increased by the provision of the cooling fin. Due to the fact that the cooling fluid flows off from the cooling rib at the rear without being detached, the flow resistance induced by the cooling rib is less than if the cooling rib had been provided with, for example, a rectangular cross section. In fact, in the case of the cooling rib with the rectangular cross section, the cooling fluid would detach downstream and form a separation region, which leads to high pressure losses. During operation of the turbine blade, there is the risk that these pressure losses are so high that an intake of the hot gas into the cooling channel, for example through cooling air bores provided in the turbine blade, occurs, as a result of which the cooling of the turbine blade is interrupted. As a result, the turbine blade would be subject to intense heating. In general, this heating of the turbine blade is so extreme that this leads to an unduly high thermal load on the turbine blade, whereby the turbine blade is destroyed. By providing the cooling fin according to the invention in the cooling channel whose rear side is designed so that the cooling fluid flow can flow off during the operation of the turbine blade free of charge, whereby any pressure losses in the cooling fluid flow are low. This advantageously prevents the possible entry of the hot gas into the cooling channel during operation of the turbine blade.

Due to the fact that the heat transfer characteristic of the cooling rib is essentially defined by the geometry of the front side facing the inflow, the profiling of the rear side of the cooling rib according to the invention has virtually no influence on the quality of the cooling of the cooling rib in the cooling duct compared with FIG for example, a rectangular cross-section having cooling rib. This advantageously achieves that the inventive cooling rib system provides effective cooling of the turbine blade, wherein For example, the collection of the hot gas is advantageously prevented in the cooling channel.

The cooling rib preferably has a front side facing away from the rear side, which protrudes perpendicularly from the blade inner side. In this case, it is preferable for the cooling rib to have a plateau which is arranged between the front side and the rear side and bridges over the front side and the rear side. The plateau is arranged parallel to the blade inner side, so that the edge formed by the front side and the plateau has a right angle. Preferred dimensions, the trailing edge is ramped, in particular rectilinear and / or convex and concave contours formed. In the surface of the rear side, a plurality of dimples is preferably provided, which are dimensioned and distributed such that the dents act as turbulators during operation of the turbine blade for the cooling fluid flow. By providing the dents, it is achieved that the degree of turbulence of the boundary layer of the cooling fluid flow at the rear side is increased. As a result, the flow of the cooling fluid at the rear side tends less to detach, whereby the rear side may tend to be formed steeper sloping towards the blade inner side. As a result, the extension of the cooling fin and thus their use of material is reduced. Further, by forming the turbulent boundary layer in the cooling fluid flow at the rear, the heat transfer from the cooling fin to the cooling fluid is improved. In the conventional cooling fin having the rectangular cross section, a recirculation area would be formed downstream of which a rebound cooling effect locally increases the heat transfer from the blade inner side to the cooling fluid in the area of the restarting. This effect, which would be lost by the free flow of the cooling fluid at the rear of the inventive fin equipped, is substantially compensated by the increase of the degree of turbulence of the boundary layer flow by means of the dimples.

The cooling fin is preferably swept, i. obliquely to the direction of flow, arranged. Furthermore, the cooling rib is preferably arranged in such a swept manner that a component can be generated in the cooling fluid flow from the trailing edge to the leading edge of the turbine blade. The temperature of the hot gas in the region of the trailing edge of the turbine blade tends to be lower than in the region of the leading edge. Due to the fact that the flow component of the cooling fluid from the trailing edge to the leading edge during operation of the turbine blade arises with the sweep of the cooling rib, the cooling rib system for the turbine blade acts more or less like a countercurrent heat exchanger.

The cooling rib preferably has laterally in each case one lateral flank delimiting the cooling rib, wherein the first side flank facing the inflow of the cooling fluid with the front side in the plan view of the cooling fin has a point angle and / or the second side flank facing away from the inflow of the cooling fluid with the front side in plan view the cooling fin forms a right angle. Furthermore, it is preferred that the cooling system has at least two cooling ribs which are arranged next to one another in a row. In this case, it is preferred that the cooling ribs are arranged at a distance from each other, so that in each case a gap is formed between the cooling ribs, which passes through the cooling fluid flow during operation of the turbine blade. The cooling fin system preferably has a plurality of rows formed by the cooling fins, wherein the rows are arranged one behind the other. The cooling fins are preferably arranged in the rows such that the cooling fins are in gap with their gaps in between. The fact that the rows are formed by the cooling fins are provided with the gaps, the relative to the flow resistance of the cooling fins is reduced, whereby the pressure loss induced by the cooling fins is additionally lowered. Further, by providing the gaps, the degree of turbulence of the cooling fluid flow is increased, thereby additionally increasing the heat transfer from the cooling fins to the cooling fluid.

Figur 1

einen Querschnitt einer ersten Ausführungsform der erfindungsgemäßen Kühlrippe;

Figur 2

einen Querschnitt einer zweiten Ausführungsform der erfindungsgemäßen Kühlrippe;

Figur 3

einen Querschnitt einer dritten Ausführungsform der erfindungsgemäßen Kühlrippe;

Figur 4

eine Draufsicht auf einen Querschnitt eines Kühlkanals mit dem erfindungsgemäßen Kühlrippensystems, das von einer Anordnung von der zweiten Ausführungsform der Kühlrippe gemäß Figur 2 gebildet ist, und

Figur 5

eine Draufsicht eines Querschnitts des Kühlkanals mit dem Kühlrippensystem, das von der Ausführungsform der Kühlrippe gemäß Figur 3 gebildet ist.

In the following the invention will be explained in more detail with reference to the attached schematic drawings. Show it:

FIG. 1

a cross section of a first embodiment of the cooling fin according to the invention;

FIG. 2

a cross section of a second embodiment of the cooling fin according to the invention;

FIG. 3

a cross section of a third embodiment of the cooling fin according to the invention;

FIG. 4

a plan view of a cross section of a cooling passage with the cooling fin system according to the invention, that of an arrangement of the second embodiment of the cooling fin according to FIG. 2 is formed, and

FIG. 5

a plan view of a cross section of the cooling passage with the cooling fin system, of the embodiment of the cooling fin according to FIG. 3 is formed.

In FIGS. 4 and 5 2, a section of a turbine blade 1 is shown, wherein the top view of a cut-open cooling channel 2, which is formed within the turbine blade 1, is shown. In FIGS. 4 and 5 is essentially lying in the plane of a blade inside 3, which defines the cooling channel 2. Further, the cooling channel 2 limits a front edge wall 5 arranged at the front edge 4 of the turbine blade 1 and a channel wall 6 arranged opposite the front edge wall 5. At the blade inner side 3, according to FIG FIGS. 4 and 5 each arranged a cooling fin system 7, wherein the cooling fin system 7 according to FIG. 4 a plurality of cooling fins 8 and the cooling fin system 7 according to FIG. 5 a single cooling fin 8 has.

In FIGS. 1 to 3 are cross sections of embodiments of the cooling fin 8 shown. During operation of the turbine blade 1, the cooling rib 8 is flown by a cooling fluid flow 18, wherein the direction of the cooling fluid flow 18 in FIGS. 1 to 3 from left to right. In the FIG. 1 shown first embodiment of the cooling fin 8 has a front side 9 which protrudes perpendicularly from the blade inner side 3. Facing away from the blade inner side 3, the front side 9 with a plateau 11 forms an edge 10 at which a right angle is enclosed by the front side 9 and the plateau 11 and the plateau 11 is arranged parallel to the blade inner side 3. Downstream of the plateau 11 includes a rear side 12, which is formed in a ramp shape and extends to a cooling fin end 13 of the plateau 11 to the blade inner side 3 out linear. The contour transitions from the plateau 11 to the rear side 12 and from the rear side 12 to the blade inner side 3 via the cooling fin end 13 are designed so that during operation of the turbine blade 1, the cooling fluid flow 18 flows around the cooling rib 8 without a release.

In FIG. 2 the second embodiment of the cooling fin 8 is shown, which differs from the first embodiment according to FIG. 1 only differs in that the rear side 12 is formed bent, whereas the rear side 12 according to the first embodiment according to FIG. 1 is formed straight. According to the second in FIG. 2 shown embodiment, the rear side 12 includes kink-free to the plateau 11 and runs downstream of the plateau 11 convexly curved toward the blade side 3. The third in FIG. 3 shown embodiment of the cooling fin 8 differs from the second in FIG. 2 shown embodiment in that in the plateau 11 and the rear side 12 a plurality of dents 14 are arranged. The dimples 14 act as turbulators, so that the boundary layer of the cooling fluid flow 18 at the plateau 11 and at the rear 12 has a high degree of turbulence.

In the FIG. 4 shown embodiment of the cooling fin system 7 is formed by a plurality of cooling fins 8, the second embodiment according to FIG. 2 correspond. The cooling fins 8 are arranged in four successive rows, 18 gaps 17 are provided in each row between the individual cooling fins, whereby the individual cooling fins 8 are arranged in each row at a distance from each other. The cooling fins of each of the rows are arranged in alignment with each other, wherein the cooling fins are arranged in the individual rows such that the individual rows are in gap. That is, one of the cooling fins of the adjacent row is arranged transversely to each gap 17 of each of the rows, so that the cooling fluid flow 18 has a meandering flow path when passing through the gaps 17. The cooling ribs 8 are arranged in the cooling channel on the blade upper side 3 with respect to the front edge 4 of the turbine blade 1, whereby the cooling fluid flow 18 receives a flow component to the leading edge 4 during the flow around the cooling ribs 8. As a result, the tendency for the fluid flow 18 to flow is that the cooling fluid flow 18 flows from the channel wall 6 to the front edge wall 5.

Each of the in FIG. 4 shown cooling ribs 8 has a first side edge 15 and a second side edge 16, wherein the side edges 15, 16 respectively delimit their associated cooling rib 8 side. The first side edge 15 closes with the front side 9 in the in FIG. 4 shown top view, while the second side edge 16 with the front side 9 in the in FIG. 4 shown top view includes a right angle. The first side flank 15 is that side flank of the cooling rib 8 which is arranged facing the inflow of the cooling fluid flow 18, wherein the second side flank 16 is that of the side flanks of the cooling fin 8 which faces the outflow of the cooling fluid flow 18.

In the FIG. 5 shown embodiment of the cooling fin system 7 is formed by a cooling fin 8, the third in FIG. 3 shown embodiment of the cooling fin 8 corresponds. The cooling fin 8 extends transversely of the channel from the channel wall 6 to the front edge wall 5, wherein the cooling fin 8 is arranged with its front side 9 and its rib end 13 swept in the cooling channel 12. As a result, the cooling fluid flow 18 when flowing over the cooling fin 8 has a tendency to flow from the channel wall 6 to the front edge wall 5. The arranged in the plateau 11 and the rear side 12 of the fin 8 dents 14 serve as turbulators and increase the degree of turbulence of the boundary layer of the cooling fluid flow 18 in the region of the plateau 11 and the rear 12. This is the one hand, the separation tendency of the boundary layer of the cooling fluid flow 18 at overcurrents of Cooling fin 8 reduced and on the other hand, the heat transfer from the cooling fin 8 to the cooling fluid flow 18 increases.

While the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (13)

Cooling rib system for a cooling channel (2) of a turbine blade (1),
with at least one cooling rib (8) arranged on the blade inner side (6) of the cooling channel (2), so that the cooling rib (8) flows transversely through cooling fluid (18) flowing in the cooling channel (2), wherein the Cooling fin (8) has a downstream rear side (12) which is profiled to the blade inner side (3) out that the cooling fluid flow (18) in the operation of the turbine blade (1) free of charge, the rear side (12) passes. Cooling fin system according to claim 1,
wherein the cooling rib (8) has a rear side (12) facing away from the front side (9) which projects perpendicularly from the blade inner side (3). Cooling fin system according to claim 2,
wherein the cooling fin (8) has a plateau (11) which is arranged between the front side (9) and the rear side (12) and bridges over the front side (9) and the rear side (12). Cooling fin system according to claim 3,
wherein the plateau (11) is arranged parallel to the blade inner side (3), so that the edge (10) formed by the front side (9) and the plateau (11) has a right angle. Cooling fin system according to one of claims 1 to 4, wherein the rear side (12) is ramped, in particular rectilinear and / or convex and concave contours, is formed. Cooling fin system according to one of claims 1 to 5, wherein in the surface of the rear side (12) a plurality of dimples (14) is provided, which are dimensioned and distributed such that the dents (14) in the operation of the turbine blade (1) for the cooling fluid flow (18) act as turbulators. Cooling fin system according to one of claims 1 to 6, wherein the cooling rib (8) is arranged in an arrowed manner. Cooling fin system according to claim 7,
wherein the cooling rib (8) is arranged in such a way that a component can be generated in the cooling fluid flow (18) from the trailing edge to the leading edge (4) of the turbine blade (1). Cooling fin system according to claim 7 or 8,
wherein the cooling rib (8) has laterally in each case one side edge flank (15, 16) delimiting the cooling rib (8) laterally,
wherein the inflow (18) of the cooling fluid facing first side edge (15) with the front (9) in the plan view of the cooling fin (8) with an acute angle and / or the inflow (18) of the cooling fluid facing away from the second side edge (16) the front side (9) in the plan view of the cooling fin (8) forms a right angle. Cooling fin system according to one of claims 1 to 9, wherein the cooling fin system (7) has at least two of the cooling ribs (8), which are arranged in a row next to each other. Cooling fin system according to claim 10,
wherein the cooling ribs (8) are arranged at a distance from each other, so that in each case a gap (17) is formed between the cooling ribs (8), which passes through the cooling fluid flow (18) during operation of the turbine blade (1). Cooling fin system according to claim 11,
wherein the cooling fin system (7) has a plurality of the rows formed by the cooling ribs (8),
wherein the rows are arranged one behind the other. Cooling fin system according to claim 12,
wherein the cooling fins (8) are arranged in the rows such that the cooling fins (8) with their intermediate gaps (17) are in gap.

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