This application claims priority under 35 U.S.C. 119 to Russian Federation application no. 2010148720, filed 29 Nov. 2010, the entirety of which is incorporated by reference herein.
1. Field of Endeavor
The present invention relates to gas turbines, and more specifically to an axial flow gas turbine
Yet more specifically, the invention relates to a stator heat shield protecting the vane carrier of an axial-flow turbine used in a gas turbine unit.
2. Brief Description of the Related Art
An example of an axial flow gas turbine is shown in
The gas turbine 10 according to
The stator heat shields are installed in gas turbine housings above blade rows. The stator heat shields preclude hot gas penetration into the cooling air cavity and form the outer surface of the turbine flow path 22. For the purposes of economy, sometimes a cooling air supply between a vane carrier and a stator heat shield is not used. However, in this case stator heat shields are also necessary to protect the vane carrier.
One of numerous aspects of the present invention includes a gas turbine with an improved and highly efficient cooling scheme
Another aspect includes a gas turbine that comprises a rotor with alternating rows of air-cooled blades and rotor heat shields, and a stator with alternating rows of air-cooled vanes and stator heat shields mounted on a vane carrier, whereby the stator coaxially surrounds the rotor to define a hot gas path in between, such that the rows of blades and stator heat shields, and the rows of vanes and rotor heat shields are opposite to each other, respectively, and a row of vanes and the next row of blades in the downstream direction define a turbine stage, and whereby the blades are provided with outer blade platforms at their tips.
Yet another aspect includes that the outer blade platforms comprise on their outside a plurality of teeth running parallel to each other in the circumferential direction and being arranged one after the other in the direction of the hot gas flow, said teeth are divided into first and second teeth, whereby the second teeth are located downstream of the first teeth, the first teeth are opposite to a downstream projection of the adjacent vanes of the turbine stage, and the second teeth are opposite to the respective stator heat shields. With such an axially “shortened” version of the stator heat shields it especially becomes possible to feed air used up in the adjacent vane airfoil to simultaneously protect the stator heat shield and cool the outer blade platform.
Another aspect includes that the blade platforms comprise, on their outside, three teeth, the first teeth comprise the first tooth in the downstream direction, and the second teeth comprise the second and third tooth in the downstream direction.
In yet another aspect, the adjacent vanes of the turbine stage are cooled with cooling air, and the utilized air from the adjacent vanes effuses between the stator heat shields and the adjacent vanes into the hot gas path to flow along and externally cool the stator heat shields and opposite outer blade platforms.
Another aspect includes that the stator heat shields are mounted on an inner ring, which on its part is mounted on the vane carrier with a first cavity being provided between the inner ring and the vane carrier, and the vanes are mounted on the vane carrier with a second cavity being provided between the vanes and the vane carrier, which second cavity is supplied with cooling air from a plenum, whereby a leakage of cooling air from the first and second cavities exists between the stator heat shields and the adjacent vanes with their downstream protections, and whereby the leaked cooling air flows along the outside of the outer blade platforms in the downstream direction.
Another aspect includes that the stator heat shields are each mounted on an inner ring with the possibility of extending freely under action of heat in both axial and circumferential directions by a forward hook and a rear hook being integral with the stator heat shields and extending in the circumferential direction, and the rear hooks are each chamfered at both ends over a predetermined length to reduce high stress concentrations due to high temperature deformation of the stator heat shields.
Another aspect includes that the stator heat shields are fixed in a circumferential slot of the inner ring in the axial direction by a radial projection, and in the circumferential direction by a pin, which enters into an axial slot under the action of the spring.
The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawings.
Opposite to the row of blades 20 there is positioned a ring of segmented stator heat shields 27, which are each mounted to an inner ring 26. A single stator heat shield 27 is shown in a perspective view in
The stator heat shields 27 can have diverse shapes depending on the design of the vane carrier 25 and the outer blade platform 45. The shape disclosed in
The inner ring 26, which carries the stator heat shields 27, is mounted in respective slots of the vane carrier 25. The stator heat shields 27 are fixed in a slot in the inner ring 26 in the axial direction by a radial projection 36 (see
Thus, due to this kind of mounting, the stator heat shields 27 can extend freely under action of heat in both the axial and circumferential directions. As can be seen in
Such a design makes it possible to avoid both additional cooling air supply into the cavity 32 to cool the stator heat shields 27 and further transportation of this air through holes within the stator heat shields to cool the opposite outer blade platforms 45.
Thus, a non-cooled stator heat shield is proposed. Furthermore, the outer blade platform 45 is assumed to be cooled by air used up in the vane airfoil (utilized air 35). In so doing, turbine efficiency increases due to this double cooling air utilization.
As shown in
On the other hand, no chamfers are provided at the forward hook 39, since with regard to shape of the outer blade platform, the stator heat shield 27 is provided there with a flexure to increase its stiffness in its forward portion.
Some characteristics and advantages can be summarized as follows:
1. The “shortened” version of the stator heat shields, provided with honeycomb above the last two outer blade platform teeth 46b,c, provides the possibility of using air, which has already been utilized in the vane airfoil, for simultaneous protection of the stator heat shields and cooling the outer blade platform 45 (see
2. The shortened version of the stator heat shield 27, provided with honeycombs above the last blade platform teeth 46b, c, provides the possibility of using cooling air leakages 34 from cavities 29 and 31 for additional cooling of the platform 45 since the projection 33 rules out any possibility for air leakage upstream of the first tooth 46a of blade platform 45.
3. Chamfers in the rear hook 38 of the stator heat shield 27 reduce the stress level in the stator heat shield 27 to a sufficient extent, and increase its life-time considerably, when it is operated in the gas turbine.
The combination of stress-decreasing chamfers and a shortened part shape in the same stator heat shield simultaneously makes it possible to create a non-cooled stator heat shield with a long-term lifespan, and increase turbine efficiency due to air saving.
10,30 gas turbine
11 compressor
12,16 fuel supply
13 burner
14,17 combustion chamber
15 high-pressure turbine
18 low-pressure turbine
19 vane carrier (stator)
20 blade
21 vane
22 hot gas path
23 plenum
24 hot gas
25 vane carrier
26 inner ring
27 stator heat shield
28 sealing plate
29,31,32 cavity
33,36 projection
34 leakage
35 utilized air
37 slot
38 rear hook
39 forward hook
40 slot (for sealing plates)
41 honeycomb
42 zone
43 edge
44 pin
45 blade outer platform
46
a-c tooth
L length
MA machine axis
TS turbine stage
While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.
Number | Date | Country | Kind |
---|---|---|---|
2010148720 | Nov 2010 | RU | national |