DE102009033753A1 - Hollow turbine blade i.e. hollow guide vane, film cooling method, involves passive-controlling flow separation at blade, and bending nozzles under angle in transverse direction to mainstream direction of gas and under another angle - Google Patents

Abstract

The method involves forming a cooling film on a surface of a hollow turbine blade (12) i.e. hollow guide vane, at a convex suction side. An incineration gas flow separation at the blade is passive-controlled by eddies produced by cooling air currents, where small quantities of coolants are discharged into the area of a high mach number of the blade from cooling air nozzles (13) with small diameter. The nozzles are bent under an angle in a transverse direction to a mainstream direction (16) of the incineration gas and under another angle diagonal to the surface of the blade. An independent claim is also included for an arrangement for cooling a film of a turbine blade.

Description

The The invention relates to a method and an arrangement for film cooling of turbine blades.

From the EP 1 108 856 B1 are turbine blades, here guide vanes, with differently inclined film cooling holes already known. The vanes are hollow to contain a portion of the compressor discharge air used to cool the individual vanes. To protect the outer surface of the vanes from the hot combustion gases passing over it from the combustion chamber of the turbine, various radial rows of film cooling holes are created through the pressure and suction sides of the vanes. Because the leading edge of the vanes first receives the hot combustion gases, it typically has multiple rows of film cooling holes in a showerhead-like arrangement. The cooling air discharged from the film cooling holes creates along the outer surface of the vanes a cooling air protection film which is fed back to end with further cooling air from row to row. The film cooling air creates a barrier which protects the metal of the vanes from the hot combustion gases during operation. The trailing edge is typically cooled by a series of trailing edge exit holes. The convex suction side wall may further include a plurality of rows of film cooling exit holes between the leading edge and the maximum thickness portion of the vane, which provide cooling air films for protecting the suction side wall that flow thereover for added protection of the trailing edge. The various film cooling holes extend substantially in the radial blade direction.

such conventional high-pressure turbines with one or two stages Training work under high temperatures under or under subsonic conditions. In the single-stage training a high-pressure turbine can be the peak Mach number on the suction side reach a level of up to 1.5 times, with a two-stage training peak Mach numbers of about 1.2 times are achievable. trends for reducing the cost of a unit realized by a reduction in the number of components lead to higher claimed vanes or blades, reducing the size the aerodynamic stresses and the associated level the peak Mach number increased or increased.

attributable on the occurrence of compression shocks on the rear or further suction side of such highly stressed blades There is also a danger of high-pressure turbines both a flow shock induced by a compression shock demolition or higher than intended or expected thermal stresses, indicating the increase attributed to the heat transfer is that through the compression shocks and the possible Flow separation or the possible Stall can be effected. The high thermal stress the guide or blades of high pressure turbines, in particular in the first stage, requires effective cooling concepts. The cooling concepts known in the art include complex ones Arrangements of film cooling holes on both the pressure as well as on the suction side of the blades.

On the suction side prevent conventional design requirements Film cooling holes near the area the peak Mach number both because of the increased level at mixing losses as well as downstream of the opening area, suggesting the introduction of rules for execution analysis attributed to the mass flow calculation is.

After all consists of the components of conventional high-pressure turbines a minimum diameter for the film cooling holes, to ensure that small, in the secondary air system Existing particles do not affect the film cooling holes block, thereby possibly undesirable thermal error of the relevant components is effected.

attributable on the concepts of aerodynamics and cooling the suction side the blades must be the largest downstream Suction side film over a very long way towards Trailing edge of the blades are maintained, which in case the reduction of film cooling a significant risk for the integrity of the thermally very heavily loaded Area of the trailing edge of the blades exists. Furthermore are for highly aerodynamically loaded guide and -aufaufschaufeln of turbines both the achievable maximum lift and a effective operating range due to the compression shocks of increased strength with strengthening Peak Mach number limited. These reinforce the local Heat transfer and the risk of through Compression collisions induced flow separation.

Of the Invention is therefore based on the object, a method and an arrangement for improving the film cooling in particular on the suction side of turbine blades to create.

To solve this problem, the invention provides a passive control of the flow separation or the stall on the blades by means of stream-like, vortex-generated vortexes, wherein small amounts of cooling agent are ejected into the high-Mach number range of the blades from small-diameter cooling air nozzles which are two times both transverse to the main flow and to the suction side surface of the blade are inclined. This improves both the film cooling on the suction side of the turbine blades and reduces the tendency for flow separation.

The The invention thus relates to a method for the production of flow-like vortices by means of cooling air nozzles, so-called air jet vortex generators (Air Jet Vortex Generator or AJVG) on the guide vanes or blades of high-pressure turbines in the subsonic or supersonic range. These cooling air nozzles (AJVG) improve the cooling air flow flow situation on the suction side of the blades and reduce the size the replacement and its irregularities. The method is based on the ejection of small quantities Coolant in the range of high-Mach number of Blades of cooling air nozzles (AJVG) with small Diameter, which is twice in both the transverse direction of the main flow or in the spanwise direction as well as to the surface of the suction side the blade are inclined.

The inventive arrangement of the cooling air nozzles or air jet vortex generators (AJVG) is about 10 to 30 times the boundary layer thickness upstream of the compression shock wave or of the detachment point. The inventive method and also the arrangement according to the invention are the same for controlling the separation of guide vanes and rotor blades highly loaded turbine blades usable.

According to the invention For turbine blades training with conventional Film cooling holes at the beginning of the suction side through downstream cooling air nozzles with a smaller diameter complemented, the so-called air jet vortex generators (Air Jet Vortex Generator or AJVG), which has a separate Cooling air duct are supplied and in two radial Directions are inclined. However, it emphasizes above all the fact that the cooling air nozzles (AJVG) also with one of the regular ones Cooling air ducts can be connected, and continue also the fact that the coolant consumption the cooling air nozzles, compared with the consumption the regular film cooling holes, low is.

The Design of the cooling air nozzles (AJVG) is through the following parameters are determined: diameter D, radial distance P of Nozzles, angle of inclination α of the nozzles opposite the flow direction and inclination angle θ the Axis of the nozzles to the surface of the suction side.

in the The scope of the invention has been a number of variations of the parameters and the cooling mass flow and investigated the potential for the detachment control demonstrated. It became a clear Difference of separation on a blade only with film cooling and the separation using the invention Cooling air nozzles (AJVG) detected.

The continuous actuation of the invention Cooling air nozzles thus causes a stabilization the separation region of the cooling air film on the surface of the suction side of the blades. this shows stabilizing the compression shock wave, when the cooling air nozzles (AJVG) are activated. It was found that in the case of the sole conventional Film cooling the force spectrum of the movement of the compression stroke shows a much stronger activity than compared with the case when the cooling air nozzles (AJVG) turned on are. This observation suggests an improved aerodynamic Stability of the aerodynamic actuation point and at a reduced level of mechanical stress Close vanes.

in addition comes that predictions about the film cooling effectiveness with Computational Fluid Dynamics (CFD) carried out for shovels in a cascade environment were. The results show a remarkable increase the film cooling efficiency downstream of the series of cooling air nozzles (AJVG), which are suitable for both examined versions are clearly distinguishable.

at an arrangement for uncooled turbine blades is the coolant for the actuation of Cooling air nozzles through feed openings in the form of holes, holes or slots in the area the standstill point of the flow delivered to the blade. Depending on the specific solution they supply Feed ports only one or a number of cooling air nozzles or air jet vortex generators (AJVG) if this with a common feeder room are connected, which is designed in the radial direction.

• – Die Kühlluftdüsen (AJVG) sind zur Richtung des Hauptstromes unter einem Winkel von α = 60° bis 90° geneigt.
• – Die Kühlluftdüsen (AJVG) sind quer zum Hauptstrom der Verbrennungsgase gerichtet.
• – Die Kühlluftdüsen (AJVG) sind unter dem Winkel θ = 20° bis 45° zur Oberfläche der Saugseite der Schaufel geneigt.
• – Die Kühlluftdüsen (AJVG) sind unter einem kleinen Winkel schwach zur Oberfläche der Saugseite der Schaufel geneigt.
• – Der Durchmesser „D” der Kühlluftdüsen (AJVG) beträgt zwischen dem 1- bis 3-Fachen der Grenzschichtverdrängungsdicke δ1 (boundary layer displacement thickness) des Kühlluftfilmes auf der Oberfläche der konvexen Saugseite der Schaufel.
• – Das Verhältnis zwischen dem Abstand „P” und dem Durchmesser „D” der Kühlluftdüsen liegt bei P/D = 10 bis 30.
• – Die Länge der Kühlluftdüsen oder des Luftstrahl-Wirbelgenerators (AJVG) beträgt wenigstens das 3- bis 5-fache des Durchmessers „D”.
• – Die Luftzufuhr ist passiv, d. h. es werden keine zusätzlichen Energiequellen für die Kühlluft benötigt, und die Luftzufuhr erfolgt von einem Kühlungskanal oder von der Oberfläche der Turbinenschaufel im Bereich der Vorderkante.

The essential features of the invention are:

• - The cooling air nozzles (AJVG) are inclined to the direction of the main flow at an angle of α = 60 ° to 90 °.
• - The cooling air nozzles (AJVG) are directed across the main flow of the combustion gases.
• - The cooling air nozzles (AJVG) are inclined at an angle θ = 20 ° to 45 ° to the surface of the suction side of the blade.
• - The cooling air nozzles (AJVG) are weak at a small angle to the surface of the Saugsei te the blade inclined.
• The diameter "D" of the cooling air nozzles (AJVG) is between 1 to 3 times the boundary layer displacement thickness δ1 of the cooling air film on the surface of the convex suction side of the blade.
• - The ratio between the distance "P" and the diameter "D" of the cooling air nozzles is P / D = 10 to 30.
• - The length of the cooling air nozzles or the AJVG is at least 3 to 5 times the diameter "D".
• - The air supply is passive, ie no additional energy sources are needed for the cooling air, and the air is supplied from a cooling duct or from the surface of the turbine blade in the area of the front edge.

The Invention allows higher aerodynamic loads by delaying the flow separation and thus an improvement of the film cooling effect the rear suction side of the blades or vanes of turbines. Due to the arrangement of the cooling air nozzles denser to the thermally critical area in the area of the trailing edge of the Suction side can also save on total consumption Coolant can be achieved. The procedure is a passive one Method and does not require additional energy for the operation of the cooling air nozzles. It becomes the coolant used by the turbine blades. As a result, the cooling air jet operated by the cooling system does not require additional cooling volume, and it becomes one of Elements of the hole cooling system. The same is true, though the cooling air from the area of the leading edge of the blade is supplied. The invention provides stabilization effects on the behavior of the compression shock by the stabilization and reducing the size of the separation area.

The inventive method for film cooling on turbine blades is described below with reference to the invention Arrangement of cooling air nozzles in the form of air jet vortex generators (AJVG) explained in more detail. It shows:

1 a cross section through a guide vane of a high-pressure turbine with conventional cooling holes for producing a cooling air film on the suction side of the guide vane according to the prior art,

2 a perspective, partially sectioned view of the suction side of a blade with the inventive arrangement of cooling air nozzles or air jet vortex generators (AJVG),

3 the arrangement of the prior art known film cooling holes and the cooling air nozzles according to the invention (AJVG) in a sectional view of a blade,

4 a schematic representation of the angular orientation of the cooling air nozzles according to the invention or air jet vortex generators (AJGV),

5 the arrangement of the cooling air nozzles according to the invention or air jet vortex generators and their cooling air supply in turbine blades without film cooling and

• a) mit Kühlluftzufuhr aus einem inneren Kühlluftkanal der Laufschaufel und
• b) mit Kühlluftzufuhr aus dem Bereich der Vorderkante der Turbinenschaufel.

6 the arrangement of the cooling air nozzles according to the invention or air jet vortex generators (AJGV),

• a) with cooling air from an inner cooling air duct of the blade and
• b) with cooling air supply from the region of the leading edge of the turbine blade.

The 1 shows a cross section through an internally hollow guide vane 1 according to the prior art in a conventional high-pressure turbine. The convex suction side 2 and the concave duck side 3 are located between the hot from the combustion chamber of the turbine hot combustion gas flow 6 first streamed leading edge 4 and the trailing edge 5 the vane 1 , In the hollow interior of the vane 1 are cooling air channels 7 . 8th designed for cooling the vane 1 supplied with compressor outlet air. In the area of the front edge 4 as well as at the beginning and in the middle of the printed page 3 are in the metallic wall 11 the vane 1 several rows of cooling air holes 9 . 10 provided, which extends substantially radially through the metallic wall 11 the vane 1 extend.

The cooling air holes 9 . 10 have a relatively large diameter to ensure that small particles present in the secondary air system of the compressor discharge air are the cooling air holes 9 . 10 do not block.

The from the cooling air holes 9 . 10 discharged cooling air generated along the outer surface of the vane 1 , in particular on the convex suction side 2 , a boundary layer in the form of a cooling air film, from row to row of the cooling air holes 9 . 10 is fed with cooling air again. The cooling air film creates a barrier that holds the metal of the vane 1 protect during operation against the hot combustion gases.

The cooling air film must be on the convex suction side 2 the vane 1 from the front edge 4 to the trailing edge 5 be maintained over a very long way, which in the case of reducing the cooling air film on this long way a significant risk to the thermal Unver Consistency of the thermally very heavily loaded area of the trailing edge 5 the vane 1 consists. Also are aerodynamically very heavily loaded vanes 1 limited both the achievable maximum lift and an effective operating range by occurring in the cooling air film compression shocks of increased strength with increasing peak Mach number. These increase the local heat transfer and the risk of detachment of the cooling air film.

The 2 shows a perspective, partially sectional view of the convex suction side 15 a hollow turbine blade 12 with the inventive arrangement of cooling air nozzles 13 in the form of air jet vortex generators (Air Jet Vortex Generator or AJVG). These are in the range of under- or supersonic even before the range of the highest speeds on the convex suction side 15 the turbine blade 12 arranged and improve the cooling air flow on the convex suction side 15 the turbine blade 12 significantly, by reducing the size of the separation of the cooling air film and its irregularities. The cooling air nozzles 13 are at a distance from the front edge fourteen in the convex suction side 15 the turbine blades 12 introduced and formed with a small diameter D. The cooling air nozzles 13 are according to 4 for generating flow-side vortex at a first angle α between 60 ° and 90 ° in the transverse direction to the main flow direction 16 of the combustion gas and at a second angle θ of 20 ° to 45 ° obliquely to the surface of the convex suction side 15 the turbine blades 12 arranged inclined. Through the cooling air nozzles 13 (AJVG) with a small diameter, twice in both the transverse direction of the combustion gas flow 16 or in the spanwise direction as well as obliquely to the surface of the turbine blades 12 are arranged inclined, small amounts of coolant in the range of high-Mach number of turbine blades 12 pushed out. The arrangement of the cooling air nozzles 13 is about 10 to 30 times the boundary layer thickness upstream of the compression shock wave or the separation point.

The 2 shows next to the arrangement of the cooling air nozzles 13 (AJVG) Diagram the projection 20 of the transversely to the combustion gas flow 16 aligned cooling air nozzles 13 generated vortex core 21 the cooling air jet jet 22 , The flow stabilizing effect of the cooling air nozzles 13 (AJVG) is based on the fact that the steep angular adjustment in the radial direction introduces a strong radial component of the vorticity into the wall-near flow region (boundary layer), which energizes the boundary layer and thereby delays a flow separation.

The arrangement according to the prior art 1 previously known cooling air holes 9 . 10 and the cooling air nozzles according to the invention 13 or air jet vortex generators (AJVG) is in 3 in a schematic sectional view through the hollow turbine blade 12 shown. It is the arrangement of conventional cooling air holes 9 . 10 essentially in front of the leading edge fourteen or at the beginning of the convex suction side 15 the turbine blade 12 and the arrangement of the present invention, located downstream and two-fold inclined in the radial direction cooling air nozzles 13 or air-jet vortex generators (AJVG) in the further course of the convex suction side 15 shown, with the cooling air nozzles 13 via a separate cooling air duct 17 be supplied with cooling air.

The cooling air nozzles 13 (AJGV) can also use one of the regular cooling air ducts 7 . 8th be connected, but the coolant consumption of the cooling air nozzles 13 compared to the consumption of the regular cooling air holes 9 . 10 much lower.

The 4 shows a schematic representation of the angular orientation of the cooling air nozzles according to the invention 13 or air jet vortex generators (AJVG) on the surface of the convex suction side 15 the turbine blade 12 , The arrangement and design of the cooling air nozzles 13 is characterized by the parameters:
Diameter D of the cooling air nozzles 13 : D = 0.2 to 0.6 mm radial distance P of the cooling air nozzles 13 from each other,
Inclination angle α of the cooling air nozzles 13 opposite to the direction of the combustion flow 16 : α = 60 ° to 90 °
Inclination of the cooling air nozzles 13 to the surface θ of the convex suction side 15 : θ = 20 ° to 45 °.

In 5 is an arrangement of the cooling air nozzles according to the invention 13 , ie air jet vortex generators (AJVG), and their cooling air supply to a turbine blade 12 shown without conventional film air cooling. Here is the cooling air for the operation of the cooling air nozzles 13 through feed openings 19 supplied in the form of holes, holes or slots from the area of the standstill point of the main flow. Depending on the specific solution, the feed openings supply 19 only one or a number of cooling air nozzles 13 (AJVG), when they are connected to a common supply channel, which is designed in the radial direction.

The 6 shows the arrangement of the cooling air nozzles according to the invention 13 , in 9a with cooling air from one in the hollow turbine blade 12 trained cooling air duct 17 and in 9b with cooling air supply via a feed opening 19 from the area of the front edge fourteen of the turbine blade 12 ,

LIST OF REFERENCE NUMBERS

1

vane (hollow)

2

suction (convex)

3

pressure side (concave)

4

leading edge

5

trailing edge

6

Combustion gas flow

7, 8th

Cooling air duct

9 10

Cooling air holes

11

wall

12

turbine blade (hollow)

13

Cooling air nozzle (Air jet vortex generator)

14

leading edge

15

suction (convex)

16

Combustion gas flow

17

Cooling air duct

18

trailing edge

19

supply opening

20

projection

21

vortex core

22

Cooling air jet

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1108856 B1 [0002]

Claims (6)

A method for film cooling turbine blades, wherein on the surface of the turbine blades, in particular on the convex suction side, a cooling film is formed, characterized in that a passive control of the stall is provided on the blades by means of generated by cooling air flows vortex, wherein small amounts of coolant in the area of high mach number of the blades are ejected from small diameter cooling air nozzles which are inclined at a first angle in the transverse direction to the main flow of the combustion gas and at a second angle oblique to the surface of the blades. Arrangement for carrying out the method according to claim 1, characterized in that at a distance from the leading edge ( fourteen ) in the suction side ( 15 ) of the blades ( 12 ) Cooling air nozzles ( 13 ) are introduced with a small diameter (D), which for generating flow-like vortex at a first angle (α) between 60 ° and 90 ° in the transverse direction to the main flow direction ( 16 ) of the combustion gas and at a second angle (θ) of 20 ° to 45 ° obliquely to the surface of the suction side ( 15 ) of the blades ( 12 ) are arranged inclined. Arrangement according to claim 2, characterized in that the diameter (D) of the cooling air nozzles ( 13 ) is between 0.2 and 0.6 mm. Arrangement according to claim 2 or 3, characterized in that the length (L) of the cooling air nozzles ( 13 ) is 3 to 5 times the diameter (D). Arrangement according to one of claims 2 to 4, characterized in that the cooling air nozzles ( 13 ) with one in a hollow turbine blade ( 12 ) formed cooling air duct ( 17 ) and supplied with cooling air via this. Arrangement according to one of claims 2 to 4, characterized in that the cooling air nozzles ( 13 ) near the leading edge ( fourteen ) of a turbine blade ( 12 ) arranged feed openings ( 19 ) to be supplied with cooling air.

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