EP2728114A1

EP2728114A1 - A platform cooling device for a blade of a turbomachine and a blade for a turbomachine

Info

Publication number: EP2728114A1
Application number: EP12190755.4A
Authority: EP
Inventors: Janos Szijarto
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2012-10-31
Filing date: 2012-10-31
Publication date: 2014-05-07
Anticipated expiration: 2032-10-31
Also published as: EP2728114B1

Abstract

A platform cooling device for a blade of a turbomachine is presented. A platform cooling device (10) includes a first portion (11) to be positioned at a platform (9) of the blade (1), a second portion (12) arranged at an angle to the first portion (11), to be positioned at a root portion (3) of the blade (1), an inlet (18) for a cooling fluid (27) on the second portion (12), and a channel (28) for directing the cooling fluid (27) from the inlet (18) to a plurality of impingement holes (20) for releasing the cooling fluid (27) at the first portion (11).

Description

The present invention relates to a blade for a turbomachine and more particularly to a platform cooling device for the blade of the turbomachine.
In modern day turbomachines various components of the turbomachine operate at very high temperatures. These components include the blade or vane component, which are in shape of an airfoil. In the present application, only "blade", but the specifications can be transferred to a vane. The high temperatures during operation of the turbomachine may damage the blade component, hence cooling of the blade component is important. Cooling of these components is generally achieved by passing a cooling fluid that may include air from a compressor of the turbomachine through a core passage way cast into the blade component.
The blade typically includes an airfoil portion and a root portion separated by a blade platform. The airfoil portion of the blade is cooled by directing a cooling fluid to flow through radial passages formed in the airfoil portions of the blades. Typically, a number of small axial passages are formed inside the blade airfoils that connect with one or more of the radial passages so that cooling air is directed over the surfaces of the airfoils, such as the leading and trailing edges or the suction and pressure surfaces. After the cooling air exits the blade it enters and mixes with the hot gas flowing through the turbine section.
However, adequate cooling of the blade platform is difficult since cooling air was not utilized in cooling the blade platform, the upper surfaces of which are exposed to the flow of hot gas from the combustors. Normally, cooling of blade platform is achieved by providing film cooling by flowing a portion of the cooling air discharged from the upstream vanes over the upper surfaces of the blade root platforms, however, the film cooling is insufficient to adequately cool the blade root platform resulting in oxidation and cracking in the platforms.
US patent number 6,120,249 describes a cooling concept for a gas turbine blade platform wherein cooling air passages are formed in the blade root platform which includes cavities formed in a radially inward facing surface of an overhanging surface of the blade airfoil. An impingement plate directs cooling air into these cavities for providing cooling.
It is an object of the present invention to provide a platform cooling device for a blade of a turbomachine which provides efficient cooling.
The object is achieved by providing a platform cooling device for a blade of a turbomachine according to claim 1 and a blade for a turbomachine according to claim 7.
According to the invention, a platform cooling device for a blade of a turbomachine is provided. The platform cooling device includes a first portion to be positioned at a platform of the blade, a second portion arranged at an angle to the first portion, to be positioned at a root portion of the blade, an inlet for a cooling fluid on the second portion, and a channel for directing the cooling fluid from the inlet to a plurality of impingement holes for releasing the cooling fluid at the first portion. By having the abovementioned platform cooling device the requirement for making channels or cavities for cooling the blade root platform is obviated. The platform cooling device provides an effective cooling by directing cooling fluid to various portions in the blade root platform. Furthermore, by having a first portion and a second portion the platform cooling device is securely attached to the blade.
In one embodiment, the second portion comprises a plurality of dumping holes for the cooling fluid. The dumping holes allow the cooling fluid to exit the platform cooling device into a space between the blades and from there as a leakage into the hot gas flow path.
In one embodiment, the platform cooling devices includes a first protrusion at the first portion for attaching to the platform and a second protrusion at second portion for attaching to the root portion such that a cavity is formed between the device and the blade for directing the cooling fluid from the impingement holes to the dumping holes. Protrusions at the first portion and the second portion allow an ease of attachment of the device with the platform and the root portion respectively. Due to the protrusions a cavity is formed between the device and the blade thereby allowing the impinged cooling fluid which gets heated after impinging on the blade platform, this heated cooling fluid is directed to the dumping holes through the cavity formed between the platform cooling device and the blade.
In one embodiment, the platform cooling device is brazed at the first protrusion and the second protrusion to the blade. Brazing does not melt the base metal of the joint and allows tighter control over tolerances, hence producing a clean joint. Furthermore, brazing allows dissimilar metals to be joined. Additionally, brazing produces less thermal distortion due to uniform heating of the brazed piece.
In one embodiment, the platform cooling device is formed from a nickel alloy. Nickel alloys can be easily brazed, have high strength, can withstand high temperatures and are corrosion resistant.
In one embodiment, the platform cooling device is formed through laser sintering. Laser sintering technique provides an efficient way of forming a desired three dimensional shape with channels to ensure cooling effectiveness.
According to an aspect of the present invention, a blade for a turbo machine is provided. The blade includes an airfoil portion and a root portion, wherein the root portion comprises a platform from which the airfoil portion extends in a radial direction, a platform cooling device disposed at the root portion, the device having a first portion and a second portion, wherein the first portion is adapted to be positioned at the platform and the second portion is adapted to be positioned at the root portion along the radial direction characterised in that the platform cooling device includes an inlet for a cooling fluid at the second portion, wherein the inlet is fluidly connected to a cooling fluid channel in the root portion, and a plurality of holes on the first portion for impinging the cooling fluid from the inlet against the platform, wherein the inlet is in flow communication with the holes for the cooling fluid. By having the present arrangement an effective cooling arrangement for the blade platform is achieved. The platform cooling device allows cooling fluid to be directed to portions of the platform where cooling is desired, obviating the need for making channels or cavities in the root portion of the blade.
In one embodiment, the first portion of the platform cooling device is attached to the platform at a first end and the second portion of the platform cooling device is attached to the root portion at a second end. Attaching the platform cooling device at the first end and the second end allows the device to be securely fixed and also create a cavity between the platform cooling device and the blade, which allows the flow of cooling fluid.
In one embodiment, the cavity extends from the first end to the second end, which allows the impinged fluid to further cool the portion of the blade in the cavity while travelling from the first end to the second end.
The above-mentioned and other features of the invention will now be addressed with reference to the accompanying drawings of the present invention. The illustrated embodiments are intended to illustrate, but not limit the invention. The drawings contain the following figures, in which like numbers refer to like parts, throughout the description and drawings.

FIG. 1 is a schematic diagram of a blade of a turbomachine including an exemplary platform cooling device;
FIG. 2 is a schematic diagram of the exemplary platform cooling device;
FIG. 3 is a sectional view of the root portion along with the platform cooling device of FIG. 2, in accordance with aspects of the present technique.

Embodiments of the present invention described below relate to a blade component in a turbo machine. However, the details of the embodiments described in the following can be transferred to a vane component without modifications, that is the terms "blade" or "vane" can be used in conjunction, since they both have the shape of an airfoil. The turbomachine may include a gas turbine, a steam turbine, a turbofan and the like.
FIG. 1 is a schematic diagram of an exemplary blade 1 of a rotor (not shown) of a turbomachine, such as a gas turbine. The blade 1 includes an airfoil portion 2 and a root portion 3. The airfoil portion 2 projects from the root portion 3 in a radial direction as depicted, wherein the radial direction means a direction perpendicular to the rotation axis of the rotor. Thus, the airfoil portion 2 extends radially along a longitudinal direction of the blade 1. The blade 1 is attached to a body of the rotor (not shown), in such a way that the root portion 3 is attached to the body of the rotor whereas the airfoil portion 2 is located at a radially outermost position. The airfoil portion 2 has an outer wall including a pressure side 6, also called pressure surface, and a suction side 7, also called suction surface. The pressure side 6 and the suction side 7 are joined together along an upstream leading edge 4 and a downstream trailing edge 5, wherein the leading edge 4 and the trailing edge 5 are spaced axially from each other as depicted in FIG. 1.
A platform 9 is formed at an upper portion of the root portion 3. The airfoil portion 2 is connected to the platform 9 and extends in the radial direction outward from the platform 9.
Furthermore, one or more cooling holes 8 are present on the pressure side 6 and the suction side 7 of the blade as depicted in FIG. 1. These cooling holes 8 aid in film cooling of the blade 1.
In accordance with aspects of the present technique, the blade 1 includes a platform cooling device 10 disposed at the root portion 3 of the blade 1 for cooling the platform 9. The exemplary platform cooling device 10 will be described in more detail hereinafter.
Referring now to FIG. 2 , an isometric view of the exemplary platform cooling device 10 is depicted. The platform cooling device 10 includes a first portion 11 and a second portion 12 wherein the second portion 12 is at an angle to the first portion 11.
It may be noted that the angle between the first portion 11 and the second portion 12 may be from about 80 degrees to about 110 degrees.
However, in the presently contemplated configuration the first portion 11 and the second portion 12 are perpendicular to each other.
The platform cooling device 10 includes a first protrusion 14 at the first portion 11 and a second protrusion 16 at the second portion 12. The first portion 11 of the platform cooling device 10 is adapted to be positioned at the platform 9 of the blade 1 and the second portion 12 is adapted to be positioned at the root portion 3 of the blade 1.
Additionally, the first protrusion 14 aids in attaching the first portion 11 of the platform cooling device 10 with the platform 9, and the second protrusion 16 aids in attaching the second portion 12 of the platform cooling device 10 with the root portion 3 of the blade 1.
An inlet 18 for a cooling fluid, such as, but not limited to cooling air, is provided at the second portion 12 of the platform cooling device 10, as depicted in FIG. 2. The inlet 18 is fluidly connected to a cooling fluid channel (not shown in FIG. 2) in the root portion 3 of the blade 1.
Furthermore, a plurality of impingement holes 20 is present in the first portion 11 of the platform cooling device 10. A channel (not shown in FIG. 2) within the platform cooling device 10 directs the cooling fluid from the inlet 18 to the plurality of impingement holes 20 for releasing the cooling fluid at the first portion 11. The released fluid impinges on a surface of the platform 9 thereby cooling the platform 9.
Additionally, the platform cooling device includes a plurality of dumping holes 22 for letting out the impinged fluid from the platform cooling device 10. The dumping holes 22 are located on the second portion 12 of the platform cooling device 10.
In accordance with aspects of the present technique, the platform cooling device 10 is manufactured by using laser sintering technique. The platform cooling device 10 may be formed of a material which is corrosion resistant and is capable of withstanding high temperatures. More particularly, the platform cooling device 10 may be formed of a nickel based alloy.
FIG. 3 shows a sectional view 25 of the blade 1 depicting the root portion 3 and the platform 9 with the platform cooling device 10. As previously noted, the platform cooling device 10 includes the first portion 11 and the second portion 12 substantially perpendicular to each other. The first portion 11 is attached to the platform 9 at a first end 32 and the second portion 12 is attached to the root portion 3 at a second end 34.
In accordance with aspects of the present technique, the platform cooling device 10 is brazed with the platform 9 and the root portion 3 at the first end 32 and the second end 34 respectively. Alternatively, the platform cooling device 10 may be attached by welding at the first end 32 and the second end 34. More particularly, brazing or welding is done at the first protrusion 14 and the second protrusion 16 thereby attaching the platform cooling device 10 at the first end 32 and the second end 34 respectively.
A cavity 30 is formed between the blade 1 and the platform cooling device 10 after attaching the platform cooling device 10 to the platform 9 and the root portion 3 at the first end 32 and the second end 34 respectively. As previously noted, the platform cooling device 10 includes the first protrusion 14 and the second protrusion 16. These protrusions 14, 16 form the cavity 30 extending from the first end 32 to the second end 34.
The cooling fluid 27 is directed via the inlet 18 into the platform cooling device 10 from a cooling fluid channel 26 in the root portion 3. More particularly, the inlet 18 is fluidly connected to the cooling fluid channel 26 in the root portion 3 for allowing the cooling fluid 27 to enter into the platform cooling device 10. The cooling fluid 27 is directed towards the plurality of impingement holes 20 via the channel 28.
After impinging against the platform 9, the cavity 30 directs the cooling fluid 27 to flow towards the second end 34. The second portion 12 of the platform cooling device 10 includes the plurality of dumping holes 22. The dumping holes 22 are located proximal to the second end 34 beyond the inlet 18 as depicted in FIG. 3.
In accordance with aspects of the present technique, the cooling fluid 27 after impinging against the platform 9 flows into the cavity 30 towards the plurality of dumping holes 22. The dumping holes 22 direct the fluid out from the blade into the hot gas flow path.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the embodiments of the present invention as defined.

Claims

A platform cooling device (10) for a blade (1) of a turbomachine comprising:
- a first portion (11) to be positioned at a platform (9) of the blade (1),

- a second portion (12) arranged at an angle to the first portion (11), to be positioned at a root portion (3) of the blade (1),

- an inlet (18) for a cooling fluid (27) on the second portion (12), and

- a channel (28) for directing the cooling fluid (27) from the inlet (18) to a plurality of impingement holes (20) for releasing the cooling fluid (27) at the first portion (11).
The platform cooling device (10) according to claim 1, wherein the second portion (12) comprises a plurality of dumping holes (22) for the cooling fluid (27).
The platform cooling device (10) according to claims 1 and 2, further comprising a first protrusion (14) at the first portion (11) for attaching to the platform (9) and a second protrusion (16) at second portion (12) for attaching to the root portion (3) such that a cavity (30) is formed between the platform cooling device (10) and the blade (1) for directing the cooling fluid (27) from the impingement holes (20) to the dumping holes (22).
The platform cooling device (10) according to any of the claims 1 to 3, wherein the platform cooling device (10) is brazed at the first protrusion (14) and the second protrusion (16) to the blade (1).
The platform cooling device (10) according to any of the claims 1 to 4, wherein the platform cooling device (10) is formed from a Nickel alloy.
The platform cooling device (10) according to any of the claims 1 to 5 wherein the device (10) is formed through laser sintering.
A blade (1) for a turbomachine comprising:
- an airfoil portion (2) and a root portion (3), wherein the root portion (3) comprises a platform (9) from which the airfoil portion (2) extends in a radial direction,

- a platform cooling device (10) disposed at the root portion (3), the device (10) having a first portion (11) and a second portion (12), wherein the first portion (11) is adapted to be positioned at the platform (9) and the second portion (12) is adapted to be positioned at the root portion (3) along the radial direction
Characterised in that
the platform cooling device (10) comprises
- an inlet (18) for a cooling fluid (27) at the second portion (12), wherein the inlet (18) is fluidly connected to a cooling fluid channel (26) in the root portion (3), and

- a plurality of impingement holes (20) on the first portion (11) for impinging the cooling fluid (27) from the inlet (18) against the platform (9), wherein the inlet (18) is in flow communication with the impingement holes (20) for the cooling fluid (27).
The blade (1) for a turbomachine according to claim 7, wherein the platform cooling device (10) further comprises a channel (28) for directing the cooling fluid (27) from the inlet (18) to the plurality of impingement holes (20).
The blade (1) for a turbomachine according to claims 7 and 8, wherein the first portion (11) of the platform cooling device (10) is attached to the platform (9) at a first end (32) and the second portion (12) of the platform cooling device (10) is attached to the root portion (3) at a second end (34).
The blade (1) for a turbomachine according to claim 9, further comprising a cavity (30) between the platform cooling device (10) and the blade (1), wherein the cavity (30) extends from the first end (32) to the second end (34).
The blade (1) for a turbomachine according to claim 10, wherein the cavity (30) directs the fluid (27) after impinging against the platform (9) towards a plurality of dumping holes (22).
The blade (1) for a turbomachine according to claim 11, wherein the plurality of dumping holes (22) is located on the second portion (12) of the platform cooling device (10).
The blade (1) for a turbomachine according to any of the claims 7 to 12, wherein the platform cooling device (10) is attached at the first end (32) and the second end (34) through brazing.
The blade (1) for a turbomachine according to any of the claims 7 to 13, wherein the platform cooling device (10) is formed through laser sintering.