The present invention relates to an arrangement of a rotor and at least a blade. The rotor and the at least a blade are part of a gas turbine engine.
Gas turbines engines typically comprise a compressor for an oxidizer such as air, a combustion chamber for combusting the compressed air with a fuel generating hot gas and a turbine for expanding the hot gas and collecting mechanical work.
The turbine in particular has a duct and vanes extending from the casing into the duct and blades extending from a rotor into the duct.
In order to connect the blades to the rotor, the rotor has seats and the blades have roots (usually shaped like fir trees) that are connected into the seats to radially fix the blade position. In addition, in order to fix the axial position of the blades, lock plates are provided connected to both the rotor and the blade.
Since the roots undergo high stress and can be subject to high temperature, for example due to leakages of hot gas from the duct, the roots (but also other rotor and blade parts close to the roots) need to be cooled. For this reason, a chamber is usually provided between the roots and the rotor (i.e. below the roots) and, in addition, a shank cavity is provided between the roots and blade platforms (i.e. above the blade roots).
Cooling air is then typically supplied into each chamber via a cooling channel of the rotor, and from the chamber cooling air is supplied into each shank cavity via passages indented in the sides of the roots, i.e. in the parts of the blades that connect the blades to the rotor.
For this reason the connection surface between the roots and the rotor is reduced; this can cause increased stress in the roots. In addition, since often the cooling channel is indented in terminal parts of the connection surface, stress of the root can be non-uniform over the connection surface axial length. Moreover, since the passages for supplying cooling air from the chamber into the shank cavity have strict constrains deriving from the fact that they are indented in the roots, their configuration could not be optimized for cooling, such that heat removal could, be non-optimal.
An aspect of the invention includes providing an arrangement of a rotor and at least a blade in which the stress distribution in the root is optimized.
Another aspect of the invention includes providing an arrangement of a rotor and at least a blade in which the heat removal from around the blade root can be optimized.
These and further aspects are attained by providing an arrangement of a rotor and at least a blade in accordance with the accompanying claims.
Advantageously, cooling the root can be decoupled from the mechanical constrains of the root.
Further characteristics and advantages will be more apparent from the description of a preferred but non-exclusive embodiment of the arrangement, illustrated by way of non-limiting example in the accompanying drawings, in which:
1 schematically shows a gas turbine engine,
2 schematically shows a duct with vanes and blades,
With reference to the figures, these show a gas turbine engine 1 having a compressor 2 for an oxidizer such as air, a combustion chamber 3 where a fuel is combusted with the compressed oxidizer generating hot gas G and a turbine 4 where the hot gas is expanded to gather mechanical work on a gas turbine rotor.
The turbine 4 has a duct 5 (usually with an annular shape) into which vanes 6 extend from a casing 7 and blades 8, 8a, 8b extend from a rotor 9.
The rotor 9 carries a plurality of blades of different stages. For example 2 shows the blades 8a, 8b, 8 of three stages next to one another.
The rotor 9 includes seats for the roots 10 of the blade 8. In particular, the root 10 has side walls 15 which complement side walls of the seat and axial walls 16 between the side walls 15.
When the blades 8 are connected in the seats, chambers 17 are provided between the root 10 and the rotor 9 (i.e. below the root); in addition shank cavities 18 are provided between the root 10 and the platform 11.
Further, lock plates 20 facing an axial wall 16 (preferably the axial wall 16 facing the compressor 2) are connected to the rotor 9 and the blade 8. The lock plates 20 have borders 21a and opposite sides 21b.
With this connection the root 10 (with its fir tree configuration) radially block the blade 8 and the lock plate 20 axially block the blade 8; the blade 8 is thus fixed to the rotor 9.
The lock plate 20 has one or more slots 22 on its side 21b facing the root 10 of the blade 8 it is connected to. The slots 22 extend in a substantially radial direction (the axis R identifies the radial axis of the turbine 4); substantially radial direction is not to be intended in a limitative way but the slots can also depart from a strict radial direction but generally develop over a radial direction (see for example
For example,
Preferably at least one slot 22 faces a root 10; this helps cooling the root and removing possible hot gas leakages from a zone around the root.
In addition, in a preferred embodiment, at least some of the plurality of slots 22 are connected together, for example via a cut out 23. In this case the cut out 23 preferably faces at least partly the chamber 17; this helps cooling air entrance from the chamber 17 into the cut out 23 and slots 22.
Between the slots 22 there are defined ribs 25. These ribs increase rigidity of the lock plate 20 and help preventing lock plate bending caused by the centrifugal forces.
Still with reference to
Likewise, the opposite end of the root 10 can also have a protrusion 29 facing away from the lock plate 20 in order to pre-define the cooling air that moves out of the chamber 17. For example this air moving out from the chamber 17 via the opening defined by the protrusion 29 is forwarded to other blades for their cooling. For example, with reference to 2, the blade 8a is connected to a cooling channel 26 whereas the blade 8b is not connected to any cooling channel similar to the cooling channel 26; in this case the blade 8b is cooled by the cooling air coming from the blade 8a via the opening defined by the protrusion 29.
Each of the protrusions 28 and 29 extends preferably radially, anyhow one or both the protrusions 28, 29 can also extend axially or radially/axially.
The operation of the arrangement is apparent from that described and illustrated and is substantially the following.
Hot gas G generated in the combustion chamber passes through the duct 5 and expands, while transferring mechanical power to the blades 8 and thus to the rotor 9.
With reference to 3, during operation cooling air A enters the chamber 17 via the cooling channel 26. From the chamber 17 the cooling air A enters the slots 22 (possibly via the cut out 23 when provided) and enters the shank cavity 18, cooling it.
In addition, cooling air moves out of the cavity 17 passing the projection 29 and moving towards other use, such as for example cooling of other blades.
Since passages for forwarding cooling air from the chambers 17 into the shank cavities 18 are not provided (or at least have a small extension) on the side walls 15 of the roots 10 but are defined by the slots 22 of the lock plates 20, stress distribution of the roots can be optimized and reduced.
In addition, since the slots 22 for cooling the roots 10 and the area around are indented in the lock plates 20, the configuration of the slots 22 can be selected according to the cooling needed at the roots 10 and possibly at the shank cavities 18 (but usually cooling at the shank cavities 18 is less burdensome than cooling of the roots 10 and is usually not troubling). Moreover, since cooling air passes between the roots 10 and the lock plates 20, possible leakages of hot gas that could overcome the lock plates 20 and reach the roots 10 are diluted by the cooling air and drawn away from the roots 10 into the shank cavities 18.
Naturally the features described may be independently provided from one another.
In practice the materials used and the dimensions can be chosen at will according to requirements and to the state of the art.
1 gas turbine engine
2 compressor
3 combustion chamber
4 turbine
5 duct
6 vane
7 casing
8, 8a, 8b blade
9 rotor
10 root
11 platform
12 airfoil
15 side wall
16 axial wall
17 chamber
18 shank cavity
20 lock plate
22 slot
23 cut out
25 rib
26 cooling channel
28 protrusion
29 protrusion
30 local restriction
b height of the slot
h width of the slot
A cooling air
G hot gas
R radial axis
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14198451 | Dec 2014 | EP | regional |
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0 801 208 | Oct 1997 | EP |
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2 436 879 | Apr 2012 | EP |
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Entry |
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European Search Report dated Jun. 16, 2015 for Application No. 14198451.8. |
Number | Date | Country | |
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20160177750 A1 | Jun 2016 | US |