U.S. patent application number 13/053765 was filed with the patent office on 2011-10-20 for blades.
This patent application is currently assigned to ROLLS-ROYCE PLC. Invention is credited to Stephen C. DIAMOND, Caner H. HELVACI, Roderick M. TOWNES.
Application Number | 20110255990 13/053765 |
Document ID | / |
Family ID | 42245384 |
Filed Date | 2011-10-20 |
United States Patent
Application |
20110255990 |
Kind Code |
A1 |
DIAMOND; Stephen C. ; et
al. |
October 20, 2011 |
BLADES
Abstract
A rotor blade for a gas turbine engine has an aerofoil portion
and a tip region. The tip region is at the radially outermost end
of the blade. The radially outermost surface carries abrasive
material (not shown) to interact with an abradable surface. The tip
has a recess in which cooling air outlets are formed. The recess is
open in a circumferential direction. This allows cooling air
outlets to be formed without interference from the abrasive
material, and inhibits any tendency for abrasion debris to collect
in the recess and interfere with the flow of cooling air.
Inventors: |
DIAMOND; Stephen C.; (Derby,
GB) ; HELVACI; Caner H.; (Derby, GB) ; TOWNES;
Roderick M.; (Derby, GB) |
Assignee: |
ROLLS-ROYCE PLC
London
GB
|
Family ID: |
42245384 |
Appl. No.: |
13/053765 |
Filed: |
March 22, 2011 |
Current U.S.
Class: |
416/97R |
Current CPC
Class: |
F01D 5/20 20130101; F16L
19/0225 20130101 |
Class at
Publication: |
416/97.R |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2010 |
GB |
1006451.7 |
Claims
1. A rotor blade having an aerofoil portion and a rotor tip at the
radially outermost end of the blade, the tip having a recess in
which cooling air outlets are formed, and the rotor tip includes at
least one winglet which projects transversely to shroud the tip,
and in which the recess is formed.
2. A rotor blade according to claim 1, wherein the recess extends
along an edge of the winglet.
3. A rotor blade according to claim 1, wherein the recess is open
in a circumferential direction.
4. A rotor blade according to claim 1, wherein the recess is open
toward the suction and/or the pressure side of the aerofoil
portion.
5. A rotor blade according to claim 1, wherein the radially
outermost surface of the tip is associated, in use, with another
surface to reduce leakage of combustion gases around the tip, one
of the surfaces carrying abrasive material, and the other one of
the surfaces being abradable.
6. A rotor blade according to claim 1, wherein the recess is open
at the radially outermost surface of the tip.
7. A rotor blade according to claim 1, wherein the rotor tip is
stepped back from the outermost surface of the tip to form the
recess.
8. A rotor blade according to claim 1, wherein the rotor tip is
chamfered back from the outermost surface of the tip to form the
recess.
9. A rotor blade according to claim 1, wherein the rotor tip is
curved from the outermost surface of the tip to form the
recess.
10. A rotor blade according to claim 1, wherein the rotor tip is
undercut to form the recess.
11. A rotor blade according to claim 1, wherein the recess extends
continuously around the radially outermost surface of the tip.
12. A rotor blade according to claim 1, wherein the radially
outermost surface of the tip is a surface of the winglet.
13. A rotor blade according to claim 12, wherein the recess extends
around at least part of the outline of the winglet.
14. A rotor blade according to claim 1, wherein the rotor tip has a
gutter extending across the radially outermost surface of the tip,
and the or each recess is open to one or more of the gutter, the
pressure side and the suction side.
15. A gas turbine engine comprising at least one rotor blade
according to claim 1.
Description
[0001] The present invention relates to rotor blades.
[0002] Rotor blades are used in gas turbine engines as turbine
blades to interact with combustion gases to convert kinetic energy
of the combustion gases into rotation of the rotor. Rotor blades
are also used as compressor blades to provide compression of the
gases, prior to combustion. The efficiency of the engine is
affected by the manner in which the combustion gases flow around
the rotor blades. One area of concern is to reduce losses
associated with over-tip leakage, in which combustion gases pass
around the radially outer end (tip) of the blade, between the tip
of the blade and the fixed casing within which the blade is
rotating.
[0003] Examples of the present invention provide a rotor blade
having an aerofoil portion and a rotor tip at the radially
outermost end of the blade, wherein the rotor tip comprises at
least one winglet which projects transversely to shroud the tip,
and in which a recess is formed, and the rotor tip further
comprises cooling air outlets formed in the recess.
[0004] The recess may extend along an edge of the winglet. The
recess may be open in a circumferential direction. The recess may
be open toward the suction and/or the pressure side of the aerofoil
portion.
[0005] The radially outermost surface of the tip may be associated,
in use, with another surface to reduce leakage of combustion gases
around the tip, one of the surfaces carrying abrasive material, and
the other one of the surfaces being abradable.
[0006] The recess may be open at the radially outermost surface.
The winglet may be stepped back from the outermost surface of the
tip to form the recess. The winglet may be chamfered back from the
outermost surface of the tip to form the recess. The winglet may be
curved from the outermost surface of the tip to form the recess.
The winglet may be undercut to form the recess.
[0007] The recess may extend continuously around the radially
outermost surface of the tip. The radially outermost surface of the
tip may be a surface of the winglet and the recess may extend
around at least part of the outline of the winglet.
[0008] The rotor tip may include a gutter extending across the
radially outermost surface of the tip, the or each recess being
open to one or more of the gutter, the pressure side and the
suction side.
[0009] Examples of the present invention also provide a gas turbine
engine comprising at least one rotor blade as defined above.
[0010] Examples of the present invention will now be described in
more detail, by way of example only, and with reference to the
accompanying drawings, in which:
[0011] FIG. 1 illustrates a section through a gas turbine
engine;
[0012] FIG. 2 is a general perspective view of a turbine blade for
use as a rotor blade in the engine of FIG. 1;
[0013] FIG. 3 is a perspective view of the tip region of a first
example embodiment of the invention, and FIG. 4 is a section along
the line 4-4 in FIG. 3;
[0014] FIG. 5 is a perspective view of the tip region of a first
example embodiment of the invention, and FIG. 6 is a section along
the line 6-6 in FIG. 5;
[0015] FIG. 7 is a perspective view of the tip region of a first
example embodiment of the invention, and FIG. 8 is a section along
the line 8-8 in FIG. 7;
[0016] FIG. 9 is a perspective view of the tip region of a first
example embodiment of the invention, and FIG. 10 is a section along
the line 10-10 in FIG. 9;
[0017] FIG. 11 is a perspective view of the tip region of a first
example embodiment of the invention; and
[0018] FIGS. 12 to 15 are sections generally corresponding with
FIGS. 4, 6, 8 and 10, illustrating further example embodiments of
the invention.
[0019] Referring to FIG. 1, a gas turbine engine is generally
indicated at 10 and comprises, in axial flow series, an air intake
11, a propulsive fan 12, an intermediate pressure compressor 13, a
high pressure compressor 14, a combustor 15, a turbine arrangement
comprising a high pressure turbine 16, an intermediate pressure
turbine 17 and a low pressure turbine 18, and an exhaust nozzle
19.
[0020] The gas turbine engine 10 operates in a conventional manner
so that air entering the intake 11 is accelerated by the fan 12
which produce two air flows: a first air flow into the intermediate
pressure compressor 13 and a second air flow which provides
propulsive thrust. The intermediate pressure compressor compresses
the air flow directed into it before delivering that air to the
high pressure compressor 14 where further compression takes
place.
[0021] The compressed air exhausted from the high pressure
compressor 14 is directed into the combustor 15 where it is mixed
with fuel and the mixture combusted. The resultant hot combustion
products then expand through, and thereby drive, the high,
intermediate and low pressure turbines 16, 17 and 18 before being
exhausted through the nozzle 19 to provide additional propulsive
thrust. The high, intermediate and low pressure turbines 16, 17 and
18 respectively drive the high and intermediate pressure
compressors 14 and 13 and the fan 12 by suitable interconnecting
shafts 26, 28, 30.
[0022] FIG. 2 shows a rotor blade 32, in this case a turbine blade,
such as those in the turbines 16, 17 and 18. The rotor blade 32 of
FIG. 2 is illustrated in order to describe various features which
are common to each of the examples to be described below.
[0023] An aerofoil portion 38 of the rotor blade 32 extends
generally radially away from the rotor 36. The aerofoil portion 38
extends to the tip region 40 of the blade 32. The aerofoil portion
38 interacts with passing combustion gases, during use, to drive
the rotor 36 (in the case of a turbine blade), or to compress the
combustion gases (in the case of a compressor blade).
[0024] The tip region 40 has features to reduce over-tip leakage
losses associated with combustion gases passing around the tip of
the blade 32. Two winglets 42, 43 project generally transversely
from the tip of the aerofoil portion 38 to shroud the tip. The
winglets 42, 43 project, respectively, from the suction face 46 and
the pressure face 48 of the aerofoil portion 38.
[0025] A gutter 50 extends across the radially outer face of the
tip 40. The presence of the gutter 50 assists in reducing over-tip
leakage and associated losses.
[0026] Turning to the remaining drawings, examples of the present
invention will now be described in more detail with reference to
turbine blades. In each of these examples, reference numerals used
above are used again in relation to those features which correspond
with the features just described in relation to FIG. 2. It is to be
understood that the invention can also be applied to compressor
blades.
EXAMPLE 1
[0027] FIGS. 3 and 4 illustrate a first example. The blade 52 has
an aerofoil portion 38, a tip region 40, and a gutter 50, as
described above. The rotor tip region 40 is at the radially
outermost end of the blade 52, and has a radially outermost surface
54. The radially outermost surface 54 of the tip 40 is associated,
in use, with another surface 58 to reduce leakage of combustion
gases around the tip 40. In this example, the radially outermost
surface 54 carries abrasive material 56 (shown in FIG. 4, but not
in FIG. 3, for reasons of clarity) and the surface 58 (FIG. 4) is
abradable, for reasons to be described. In an alternative
arrangement, the abrasive and abradable properties may be reversed,
with abrasive material being carried by the surface 58, and the
radially outermost surface 54 being abradable. Other examples may
omit the use of abrasive and abradable materials, leaving the blade
uncoated at its tip.
[0028] The abradable surface 58 forms part of a stationary shroud
and seal arrangement within which the rotor blade rotates. It is
desirable to minimise the gap 66 between the abradable surface 58
and the tip region 40 in order to reduce leakage of combustion
gases around the tip region 40, through the gap 66. However,
tolerances on manufacture and assembly are expected to result in
some variation of the width of the gap 66 at different positions
around the rotor. The adverse effects of this can be mitigated by
allowing the abrasive material 56 to cut into the abradable surface
58, thereby cutting a track which takes into account any
manufacture or assembly tolerances to improve the sealing and
reduce over-tip leakage. The abrasive and abradable surfaces may be
reversed, as noted above.
[0029] The winglet 42 has a recess 60 in which cooling air outlets
62 are formed. The recess 60 is formed in the winglet 42. The
recess 60 is open in a circumferential direction 64.
[0030] In this description, the term "circumferential direction" is
used to refer to the direction (in either sense) in which rotor
blades move as they turn around their operating axis and which is,
at any point, generally perpendicular to the radial direction which
extends out from the operating axis.
[0031] The recess 60 is open at the radially outermost surface 54.
That is, the recess 60 is not covered when the tip region 40 is
viewed along a radius toward the rotation axis of the blade 52. The
recess 60 extends along an edge 68 (FIG. 3) which, in this example,
is an edge forming part of the outline of the winglet 42, along the
gutter 50. The winglet 42 extends from the suction face 48. The
winglet 42 is stepped back at 70 to form a generally rectilinear
recess 60, having a wall 72 which is generally radial in direction,
and a floor 74 which is generally circumferential. Accordingly, the
recess 60 is also open to the gutter 50, in a circumferential
direction 64.
[0032] The cooling air outlets 62 are formed in the floor 74.
Consequently, the cooling air outlets 62 are formed in the winglet
42. The cooling air outlets 62 are supplied with cooling air
through a passage 76 which is in communication with a void 78
within the aerofoil portion 38 of the blade 52.
EXAMPLE 2
[0033] FIGS. 5 and 6 illustrate a second example. This rotor blade
52a has many features in common with, or equivalent to features
described above in relation to FIGS. 3 and 4. In relation to those
features, the same numerals are used again, with the suffix
"a".
[0034] The principal difference between this example and the first
example is the location of the recess 60a. The recess 60a is formed
in the winglet 43. The recess 60a again extends along an edge 68a
which, in this example, is an edge forming part of the outline of
the winglet 43, along the gutter 50. The winglet 43 extends from
the pressure face 46 of the aerofoil portion 38.
[0035] The winglet 43 is stepped back at 70a to form a generally
rectilinear recess 60a, having a wall 72a which is generally radial
in direction, and a floor 74a which is generally circumferential.
Accordingly, the recess 60a is also open to the gutter 50a, in a
circumferential direction 64a.
[0036] Cooling air outlets 62a are formed in the floor 74a.
Consequently, the cooling air outlets 62a are formed in the winglet
43. The cooling air outlets 62a are supplied with cooling air
through a passage 76a which is in communication with a void 78a
within the aerofoil portion 38a of the blade 52a.
[0037] This example also differs from the first example, in that
neither the radially outermost surface 54 nor the surface 58 is
coated with abrasive material. Some sealing is achieved by the
proximity of the surfaces 54, 58, but is not enhanced by abrasion
between them.
EXAMPLES 3 AND 4
[0038] FIGS. 7 and 8 illustrate a third example. FIGS. 9 and 10
illustrate a fourth example. These examples can conveniently be
described together. These rotor blades 52b,c again have many
features in common with, or equivalent to features described above
in relation to FIGS. 3 and 4. In relation to those features, the
same numerals are used again, with the suffixes "b" and "c".
[0039] The principal difference between these examples and the
previous examples is the location of the recesses 60b,c. The
recesses 60b,c are formed in the winglets 42, 43. The recesses
60b,c again extend along edges 68b,c. In these examples, the
recesses 60b,c are formed along the outer edges 68b,c of the
winglets 42, 43, over the suction face 48 and pressure face 46,
respectively.
[0040] In each of these examples, one of the winglets 42, 43 is
stepped back at 70b,c to form a generally rectilinear recess 60b,c,
having a wall 72b,c which is generally radial in direction, and a
floor 74b,c which is generally circumferential. Accordingly, the
recesses 60b,c are also each open in a circumferential direction
64b,c, respectively to the suction side and pressure side of the
blade 52b,c.
[0041] Cooling air outlets 62b,c are formed in the floors 74b,c.
Consequently, the cooling air outlets 62a are formed in the winglet
43. The cooling air outlets 62a are supplied with cooling air
through passages 76b,c which are in communication with voids 78b,c
within the aerofoil portions 38b,c of the blades 52b,c.
EXAMPLE 5
[0042] FIG. 11 illustrates a fifth example. This rotor blade 52d
has many features in common with, or equivalent to features
described above in relation to FIGS. 3 and 4 and in relation to
those features, the same numerals are used again, with the suffix
"d".
[0043] The principal difference between this example and the first
example is the provision of two recesses 60d, and the form of the
recesses 60d. The recesses 60d are formed in the winglets 42, 43.
The recesses 60d again extend along the outline of the winglets 42,
43. In this example, the recesses 60d extend continuously around
the respective winglet 42, 43.
[0044] The winglets 42, 43 are stepped back in the manner described
above, to form generally rectilinear recesses 60d. Accordingly, the
recesses 60d are open in a circumferential direction, around the
entire outline of the winglets 42, 43.
[0045] Cooling air outlets 62d are formed in the floors 74d.
Consequently, the cooling air outlets 62a are formed in the winglet
43. The cooling air outlets 62a are supplied with cooling air
through passages (not shown) which are in communication with a void
within the aerofoil portion of the blade.
FURTHER EXAMPLES
[0046] In all of the examples described above, the recesses have
been described as having a generally rectilinear form defined by a
radial wall and a circumferential floor. Other geometries can be
used. Several additional examples are illustrated in the remaining
drawings. In each of these, the recesses are shown open to the
gutter 50, but it will be readily apparent to the skilled reader
that these geometries can be incorporated in any of the examples
described above.
[0047] In FIG. 12, the recess 60e is formed as a sloping chamfer
along the edge of one of the winglets, and is open in a
circumferential direction 64e.
[0048] In FIG. 13, the recess 60f is defined by a curve formed
along the edge of one of the winglets, and is open in a
circumferential direction 64f.
[0049] In FIG. 14 and FIG. 15, the recess 60g,h is defined by an
undercut. In FIG. 14, the undercut is partial, so that part of the
recess 60g is covered by a lip 80, and part is open in the radially
outer direction. In FIG. 15, a longer lip 80a fully covers the
recess 60h in the radial direction. However, both recesses 60g, h
are open to the gutter 50g, h in the circumferential direction
64g,h.
CONCLUDING REMARKS
[0050] In each of these examples, the cooling air outlets are not
formed in the radially outermost surface, but in the recess. In
those examples which use abrasive and abradable material, debris
from the abrasion process may enter the recesses during use, but is
unlikely to be captured in the recess, because the recess is open
for the debris to leave in a circumferential direction. In all of
the examples, including those which do not use abrasive and
abradable materials, any debris arising for other reasons is
unlikely to be captured in the recess, for similar reasons.
Consequently, we envisage that even when debris is being created by
the abrasion process or arises for other reasons, the cooling flow
from the cooling air outlets will not be choked or obstructed, so
that the tip region 40 will be cooled as intended, and will not
tend to overheat. In addition, initial formation of the cooling air
outlets and associated passages is expected to be facilitated, for
example by drilling after the abrasive material is in place, but
without requiring the abrasive material to be drilled, which is
likely to be very difficult. Alternatively, the cooling air outlets
and associated passages can be formed before the abrasive material
is in place, with reduced risk of the outlets being clogged by
abrasive material, because the abrasive material is not required on
the surfaces of the recess.
[0051] In each of these examples, the recess or recesses are
described as formed in the winglet or winglets because they extend
wholly or partly beyond the suction face or pressure face of the
aerofoil portion, in a circumferential direction.
[0052] Recesses and cooling air outlets have been described at
various positions in the various examples. These examples of
recesses can be used in combination with each other, if desired.
The sizes and relative sizes of the recesses, cooling air outlets
and other features can be varied widely, according to design
choices. In particular, design choices can be made in relation to
the length of each recess along the corresponding edge, the radial
depth of the recess, the extent of the recess in the
circumferential direction, and in the size and number of cooling
air outlets.
[0053] It will be understood by the skilled reader that many other
geometries, sizes, shapes and materials could be used within the
examples described above.
[0054] Examples of the present invention can be embodied in rotor
blades for gas turbine engines, such as high-pressure turbine
blades. The gas turbine engines can be used for aerospace, marine,
or other propulsion purposes, or for static power generation
purposes.
* * * * *