U.S. patent application number 15/683339 was filed with the patent office on 2018-03-15 for turbine blade cooling.
This patent application is currently assigned to ROLLS-ROYCE plc. The applicant listed for this patent is ROLLS-ROYCE plc. Invention is credited to Stefano CALONI, David J. HUNT, Haidong LI, Martin MOTTRAM, Shahrokh SHAHPAR.
Application Number | 20180073370 15/683339 |
Document ID | / |
Family ID | 59677159 |
Filed Date | 2018-03-15 |
United States Patent
Application |
20180073370 |
Kind Code |
A1 |
MOTTRAM; Martin ; et
al. |
March 15, 2018 |
TURBINE BLADE COOLING
Abstract
A blade includes a root and an elongate portion extending to a
tip, the elongate portion having an aerofoil-shaped cross-section.
The aerofoil has leading and trailing edges, and suction and
pressure sides. The tip includes a squealer defining a gutter at
the tip, the squealer extending from the trailing edge along the
entirety of a first of the suction and pressure sides, around the
leading edge and partly along a second of the suction and pressure
sides leaving a gap between the trailing edge and an end of the
wall. A main trailing edge cooling channel extends within the
elongate portion in a direction from root to tip adjacent the
trailing edge and exits into the gutter. The main trailing edge
cooling channel includes a bend just downstream of the exit, the
exit displaced from a camber line of the blade elongated portion
towards the second side.
Inventors: |
MOTTRAM; Martin; (Bristol,
GB) ; HUNT; David J.; (Lichfield, GB) ; LI;
Haidong; (Bristol, GB) ; SHAHPAR; Shahrokh;
(Derby, GB) ; CALONI; Stefano; (Derby,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROLLS-ROYCE plc |
London |
|
GB |
|
|
Assignee: |
ROLLS-ROYCE plc
London
GB
|
Family ID: |
59677159 |
Appl. No.: |
15/683339 |
Filed: |
August 22, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 5/186 20130101;
F05D 2240/304 20130101; F05D 2250/52 20130101; F01D 5/20 20130101;
F05D 2260/202 20130101; F01D 5/141 20130101; F05D 2240/307
20130101; F05D 2250/314 20130101 |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2016 |
GB |
1615571.5 |
Sep 14, 2016 |
GB |
1615573.1 |
Claims
1. A blade comprising a root portion and an elongate portion
extending from the root portion to a tip, the elongate portion
having an aerofoil-shaped cross section having a leading edge, a
trailing edge, a suction side and a pressure side, the tip
including a squealer defining a gutter at the tip wherein the
squealer comprises a wall extending from the trailing edge along
the entirety of a first of the suction side and pressure side,
around the leading edge and partly along a second of the suction
side and pressure side leaving a gap between the trailing edge and
an end of the wall on the second side, a main trailing edge cooling
channel extending within the elongate portion in a direction from
root to tip adjacent the trailing edge and exiting into the gutter,
wherein the main trailing edge cooling channel includes a bend just
upstream of the exit such that the exit is displaced from a camber
line of the blade elongated portion towards the second side.
2. A blade as claimed in claim 1 wherein the first side is the
pressure side and the main trailing edge cooling channel bends
towards the suction side.
3. A blade as claimed in claim 1 wherein the first side is the
suction side and the main trailing edge cooling channel bends
towards the pressure side.
4. A blade as claimed in claim 1 wherein the gutter is shallower
adjacent the leading edge than it is at the trailing edge.
5. A blade as claimed in claim 1 wherein the gutter in the region
of the trailing edge is inclined from the first side towards the
second side whereby to maintain a surface which is substantially
orthogonal to the walls of the main trailing edge cooling channel
where they meet the gutter.
6. A blade as claimed in claim 1 further comprising a gallery
channel integrally cast into the blade using an adapted core which
defines both the main trailing edge cooling channel and has an
extension defining the gallery channel.
7. A blade as claimed in claim 5 wherein the gallery channel is
provided in a shape which minimises flow restriction in the gallery
channel.
8. A blade as claimed claim 5 wherein the gallery channel is spout
shaped having a larger diameter at an open end where it intersects
the main trailing edge cooling channel and a smaller diameter at a
closed end which sits just behind an apogee of the trailing
edge.
9. A blade as claimed in claim 5 wherein a tip facing surface of
the gallery channel is profiled to complement and extend in
parallel with the surface of the gutter in the trailing edge
region.
10. A blade as claimed in claim 5 wherein the gallery channel is
shaped to follow variations in the depth of the gutter.
11. A blade as claimed in claim 5 further comprising an array of
film cooling channels extending from the gallery channel and
through the squealer wall.
12. A blade as claimed in claim 1 wherein the depth of the squealer
wall varies from a first depth at the leading edge to a second and
greater depth at the trailing edge.
13. A blade as claimed in claim 1 wherein the width of the squealer
wall is variable.
14. A blade as claimed in claim 13 wherein the width of the
squealer wall reduces from a maximum width at a first end of the
squealer wall to a minimum width at a second end of the squealer
wall.
15. A blade as claimed in claim 1 wherein the squealer wall
includes a locally extended portion adjacent the trailing edge on
the first side, the extended portion extending in a widthwise
direction with respect to the squealer wall and away from the
gutter.
16. A blade as claimed in claim 1 configured for use in a gas
turbine engine.
Description
FIELD OF DISCLOSURE
[0001] The present disclosure relates to shroudless turbine blades
having squealer tips. More particularly the invention relates to
the arrangement of internal cooling channels in this region of the
blade and the geometry of squealer tips which accommodate the
cooling channels.
BACKGROUND
[0002] In a gas turbine engine, a compressor is arranged to
compress air for delivery to a combustor. The combustor mixes the
compressed air with fuel and ignites the mixture. Gas products of
this combustion are directed at a turbine blade assembly causing
rotation of the blades and the production of power from the turbine
assembly. Combustion temperatures may exceed 1400.degree. C. and
typical configurations expose the turbine blade assemblies to these
high temperatures. Turbine blades are made of materials capable of
withstanding such high temperatures and often contain cooling
systems for prolonging the life of the blades, reducing the
likelihood of failure as a result of exposure to these excessive
temperatures.
[0003] A turbine blade has a root portion at one end and an
elongated portion of aerofoil shaped cross section extending from
the root portion. In a turbine blade assembly, the root portion is
coupled to a platform, typically a radially outer surface of a
circumferential wall of a rotor disc. The elongated portion extends
radially outwardly and terminates in a tip. The aerofoil shaped
cross section has a leading edge and a trailing edge joined by a
suction side and a pressure side.
[0004] Efforts are continually being made to improve efficiency in
gas turbine engines. It is known that a significant factor in
reducing efficiency of the turbine assembly is attributable to the
leakage of the combustion gas products over the tips of the turbine
blades through a small gap between the tips of the blade assembly
and a surrounding circumferential housing. It is believed such
losses could account for 30% or more of total losses in the turbine
assembly. As well as reduced efficiency, consequences include
reduced life of turbine components due to high thermal stresses in
this region.
[0005] It is known to provide turbine blade tips with seals to
reduce this gap. Such tip seals are referred to as squealer tips
and these are typically machined into a cast turbine blade. A
squealer tip is formed as a wall extending around a substantial
portion of the aerofoil at the blade tip defining a gutter within.
Cooling air which has passed through the elongate portion of the
blade may be expelled into this gutter and dispersed into the main
gas stream.
[0006] For aerodynamic efficiency, it is desirable to minimise the
thickness of a blade at its trailing edge. However, thinner
sections of blade are more susceptible to the extreme temperatures
and are at risk of deformation and damage a consequence of which
may be reduced engine efficiency and potential failure of the
component. Thus, the trailing edge of the blade must be well
cooled.
[0007] In known blades having squealer tips, a main trailing edge
cooling channel is provided in the elongated portion of the blade
and extends from root to tip of the blade. Multiple smaller
diameter cooling channels (typically including effusion cooling
channels) extend from the main trailing edge channel through the
squealer wall in the region of the trailing edge and through the
elongate portion to the thinnest parts of the trailing edge.
Typically a gallery channel is provided just beneath the gutter
surface of the squealer and extends from the main trailing edge
cooling channel towards an apogee of the trailing edge. Effusion
cooling channels extend through the squealer wall to the gallery
channel. The main trailing edge cooling channel is typically
integrally cast into the blade. The gallery channel and effusion
cooling channels may be added in a subsequent machining step. The
gallery channel is typically machined from the apogee of the
trailing edge and its end at the apogee subsequently plugged or
welded closed to encourage maximum flow to the effusion cooling
channels.
[0008] An example of a prior art arrangement is shown in FIG. 1.
The figure shows the tip of a blade from a plan view, pressure side
view and trailing edge end view. As can be seen, the tip has an
aerofoil shaped cross section with a leading edge 1, a trailing
edge 2, a suction side 3 and a pressure side 4. A squealer
comprises a squealer wall 5 which extends from the trailing edge 2
along the suction side 3, around leading edge 1 and along the
pressure side 4 returning to the trailing edge 2. The wall defines
a gutter 6. Main cooling channels extend along the elongated
portion of the blade and exit into the gutter 6. The main cooling
channels include a main trailing edge cooling channel 7. A gallery
channel 8 is drilled into the trailing edge 2 from the apogee 9 of
the trailing edge 2. A first plurality of effusion cooling channels
10 extend from the gallery channel 8 and through the squealer wall
5. As can be seen, in the region of the tip, the apogee 9 of the
trailing edge 2 is flared 12 and enlarged to accommodate the
drilling of the gallery channel 8. A second plurality of effusion
cooling channels 11 extends from the main trailing edge cooling
channel into the thinnest region of the trailing edge exiting on
the pressure side 4 adjacent the apogee 9 of the trailing edge
2.
[0009] The large overhang 12 of the squealer results in a larger
wetted area and hence increased heat flux into the tip during
engine operation. This increases the cooling requirement for this
region. Other disadvantages of the arrangement include sub-optimal
aerodynamic performance at the trailing edge resulting in
efficiency losses and a weight penalty.
[0010] The present disclosure seeks to provide an improved cooling
arrangement and associated squealer tip design which contributes to
the mitigation of the problems identified above.
SUMMARY
[0011] In accordance with the present disclosure there is provided
a blade comprising a root portion and an elongate portion extending
from the root portion to a tip, the elongate portion having an
aerofoil-shaped cross section having a leading edge, a trailing
edge, a suction side and pressure side, the tip including a
squealer defining a gutter at the tip wherein the squealer
comprises a wall extending from the trailing edge along the
entirety of a first of the suction side and pressure side, around
the leading edge and partly along a second of the suction side and
pressure side leaving a gap between the trailing edge and an end of
the wall on the second side, a main trailing edge cooling channel
extending within the elongate portion in a direction from root to
tip adjacent the trailing edge and exiting into the gutter, wherein
the main trailing edge cooling channel includes a bend just
upstream of the exit such that the exit is displaced from a camber
line of the blade elongated portion towards the gap on the second
side.
[0012] In some embodiments the first side is the pressure side. In
other embodiments the first side is the suction side. The end of
the squealer wall on the second side may be curved.
[0013] In some embodiments, the gutter in the region of the
trailing edge is inclined from the first side towards the second
side whereby to maintain a surface which is substantially
orthogonal to the walls of the main trailing edge cooling channel
where they meet the gutter surface.
[0014] The depth of the squealer wall may vary from a first depth
at the leading edge to a second and greater depth at the trailing
edge. The width of the squealer wall may reduce from a maximum
width at a first end of the squealer wall to a minimum width at a
second end of the squealer wall. Optionally, the squealer wall may
be locally thinned or thickened to accommodate internal passages
within the wall or to satisfy manufacturing requirements.
[0015] The squealer wall may include a locally extended portion
adjacent the trailing edge on the first side, the extended portion
extending in a widthwise direction with respect to the squealer
wall and away from the gutter. The extended portion may accommodate
a gallery channel and associated effusion cooling channels for
cooling the trailing edge at the tip.
[0016] The gutter may be shallower adjacent the leading edge than
it is at the trailing edge. Variation in gutter depth may be
achieved by providing an inclined surface to the tip within the
gutter. Alternatively, variation in gutter depth is achieved by
varying the height of the wall of the squealer between the trailing
edge and the leading edge. Gutter depth may vary gradually along an
incline, alternatively or in addition, gutter depth may vary due to
one or more steps within the gutter. The gallery channel may be
shaped to follow variations in the depth of the gutter. For
example, the gallery channel may include a stepped section to
accommodate a step in the gutter.
[0017] A gallery channel may be integrally cast into the blade
using an adapted core which defines both the main trailing edge
cooling channel and has an extension defining the gallery
channel.
[0018] The gallery channel may be provided in a shape which
minimises flow restriction in the gallery channel. For example the
gallery channel is conically tapered from its open end to its
closed end. In more complex embodiments, the cross sectional shape
of the gallery channel may be varied in a manner designed to tune
coolant flow to suit cooling requirements in different regions of
the blade tip and squealer. For example, the gallery channel is
shaped to encourage optimum flow rates to the film cooling holes in
accordance with cooling requirements at the exits of the film
cooling holes. For example, to control the impact of aerodynamics
in a known operational environment in which the blade is to be
used, the gallery may be configured to bias cooling towards one of
the suction side and pressure side.
[0019] The film cooling channels may comprise effusion cooling
channels. Axes of the effusion cooling channels may be inclined to
a surface of the squealer wall. The effusion cooling channels may
have a varying cross section, for example the effusion cooling
channels may include a fanned portion adjacent the exit to a
squealer wall surface. Film cooling channels may be introduced
after a blade has been cast. For example, the film cooling channels
may be drilled using an EDM process.
[0020] The blade may be configured for use in a gas turbine engine,
for example the blade may be configured for use in a compressor
section or turbine section of a gas turbine engine. One useful
application of the design of the invention is in blades of a high
pressure turbine stage in a gas turbine engine.
BRIEF DESCRIPTION OF DRAWINGS
[0021] For the purposes of exemplification, some embodiments of the
invention will now be described with reference to the accompanying
Figures in which;
[0022] FIG. 1 shows a blade tip having a squealer and cooling
channel arrangement as is known from the prior art;
[0023] FIG. 2 shows a core for defining a main trailing edge
cooling channel in a blade in accordance with the invention;
[0024] FIG. 3 shows the core of FIG. 2 positioned with respect to a
surface of a blade made in accordance with the invention;
[0025] FIG. 4 shows an alternative core positioned with respect to
a surface of a blade made in accordance with the invention;
[0026] FIG. 5 shows a view from the tip of a blade manufactured in
accordance with the invention;
[0027] FIG. 6 shows an embodiment of a squealer arrangement of a
blade in accordance with the invention;
[0028] FIG. 7 shows an alternative embodiment of a squealer
arrangement of a blade a blade in accordance with the
invention;
[0029] FIG. 8 shows an example of a gas turbine engine into which
blades in accordance with the invention may usefully be
incorporated.
DETAILED DESCRIPTION OF DRAWINGS AND EMBODIMENTS
[0030] FIG. 1 has already been described above.
[0031] FIG. 2 shows a core suited to defining a main trailing edge
cooling channel in an embodiment of a blade in accordance with the
invention. The core 20 has a main trailing edge cooling channel
section 21 which is elongate and proportioned to extend in a root
to tip direction within a mould which defines the elongate portion
of a blade to be cast in the mould. Towards the tip end, the main
trailing edge cooling channel section 21 has an inclined portion 22
as compared to the remainder of the main trailing edge cooling
channel section 21. Within a mould, the main trailing edge cooling
channel section 21 sits substantially in alignment with a camber
line of the blade mould. The inclined portion 22 results in an exit
of the main trailing edge cooling channel section 21 being
positioned to one side of the camber line. Depending on
requirements, the incline could be towards the pressure surface
side or the suction surface side of the blade. The core further
includes a gallery channel portion 23. The gallery channel portion
23 extends in a leading edge to trailing edge direction within the
blade mould. The gallery channel portion 23 has a substantially
flat upper wall 24 which defines a wall of the gallery channel in a
blade which is substantially in parallel with a surface of a gutter
in the tip of the blade. A lower surface 25 of the gallery channel
23 is curved to form a spout shaped gallery channel portion 23.
[0032] FIG. 3 shows a wireframe view of the core of FIG. 2 arranged
behind a pressure surface side 36 of a blade 30 in accordance with
the invention. The main trailing edge cooling channel core 31, 32
has an elongate section 31 and inclined section 32. The elongate
section 31 extends in a root to tip direction through the blade 30
passing through a camber line of the blade. The inclined section 32
tilts the channel away from the camber line and towards a suction
surface side (not shown) of the blade 30. A spout shaped gallery
channel portion 33 extends from the elongate section 31 towards an
apogee 39 of the trailing edge of the blade 30. A closed end of the
gallery channel portion 33a sits behind the apogee 39. A top
surface 33b of the gallery channel portion 33 is planar and extends
in parallel with a surface of a gutter 38 which is bordered by a
squealer wall 37. The gallery channel portion 33 extends beneath
the surface of the gutter 38. The inclined portion 32 exits into
the gutter 38 towards the suction surface side of the camber
line.
[0033] FIG. 4 shows a wireframe view of an alternative core
arranged behind a pressure surface side 46 of a blade 40 in
accordance with the invention. The main trailing edge cooling
channel core 41, 42 has an elongate section 41 and inclined section
42. The elongate section 41 extends in a root to tip direction
through the blade 40 passing through a camber line of the blade.
The inclined section 42 tilts the channel away from the camber line
and towards a suction surface side (not shown) of the blade 40 and
exits through gutter 48 at a position to the suction surface side
of the camber line. In this arrangement, there is no gallery
channel section to the core. A gallery channel may be added after
casting by drilling from the apogee 49 side through to the elongate
section 41. In such a case the end of the gallery channel at the
apogee 49 may be plugged or welded to close the gallery
channel.
[0034] FIG. 5 shows the tip end of a blade having an
aerofoil-shaped cross section. The blade has a suction side 51 and
a pressure side 52 which meet to form a leading edge 53 and a
trailing edge 54. The elongate portion of the blade terminating in
the tip extends from a root portion 55. Around a perimeter of the
tip is provide a squealer wall 56 which extends from a first end
56a at the trailing edge 54 to a second end 56b midway along the
suction side 51 leaving a gap along the remainder of the suction
side 51 to the trailing edge 54.
[0035] The wall 56 defines a gutter 57 in the tip. As can be seen a
plurality of cooling channels 58a, 58b, 58c, 58d, 58e exit the
elongate portion of the blade in the gutter 57. Exits to cooling
channels 58b, 58c, 58d and 58e sit along a camber line C-C of the
blade. Cooling channel 58a is the main trailing edge cooling
channel which includes the inclined portion as discussed in
accordance with the invention. As can be seen, this channel 58a has
an exit which is positioned towards the suction side 51 of the
camber line C-C. In a subsequent manufacturing step, the cooling
channels 58a, 58b, 58c, 58d and 58e may be blocked at the blade tip
by weld caps, each weld cap having a small diameter hole through it
(typically 0.5 mm) to allow egress of dust from the internal
passages. Film cooling channels may be provided through the suction
side and/or pressure side walls to connect with the channels.
Capping at the tip encourages greater flow to these film cooling
channels.
[0036] The gutter 57 includes a step 59 which results in the gutter
57 being deeper towards the trailing edge 54 end of the gutter than
the leading edge 53 end of the gutter 57 and also provides an
incline from the suction side towards the pressure side. This
incline is selected to ensure that the surface of the gutter 57
around the exit of channel 58a is approximately orthogonal to walls
of the channel 58a at the exit.
[0037] The second end 56b of the squealer wall 56 is gently curved
to discourage turbulent flow of cooling air which exits into the
gutter 57 from the channels 58a-58e and flows towards the trailing
edge 54 to join a main flow of hot air delivered from the combustor
to generate work from a turbine assembly of which the blade forms a
part.
[0038] FIG. 6 shows the tip end of a blade in accordance with
invention. As can be seen, the blade has a suction side 61, a
pressure side 62, a leading edge 63 and a trailing edge 64. A
squealer wall 66 extends from a first end 66a along the pressure
side 62, around the leading edge 63 and part way along the suctions
side 61 to a second end 66b. The second end 66b is smoothly curved.
The wall 66 defines a gutter 67 which has a first depth d.sub.1 at
the trailing edge 64 and a second depth d.sub.2 at the leading edge
63. The first depth d.sub.1 is greater than the second depth
d.sub.2. This is achieved by an incline on the gutter 67 surface
from the leading edge 63 to the trailing edge 64. The wall has a
first width w.sub.1 adjacent the trailing edge 64 on the pressure
side 62 and a second width w.sub.2 adjacent second end 66b on the
suction side 61. The first width w.sub.1, is greater than the
second width w.sub.2 and smoothly varies from suction side to the
pressure side In other embodiments, the variation may be reversed
with width w.sub.2 being greater than width w.sub.1, the wall 66
being generally thinner along the pressure side. The first width
w.sub.1 is increased by the inclusion of an extension 68 adjacent
the first end 66a which extends from the trailing edge 64 a short
distance along the pressure side 62.
[0039] In the embodiment of FIG. 7, in contrast to the embodiments
of FIGS. 1 and 2, the squealer wall 76 extends from a first end 76a
at the trailing edge 74 entirely along the suction side 71, around
the leading edge 73 and terminates at a second end 76b part way
along the pressure side 72. The wall defines a gutter 77 which may
include a gradual incline (not shown) from the leading edge 73 to
the trailing edge 74. The wall has an extension 78 on the suction
side 71 adjacent the trailing edge which serves to increase the
wall width w.sub.1 at this location such that it is wider than a
wall width w.sub.2 near the second end 76b on the pressure side
72.
[0040] With reference to FIG. 8, a gas turbine engine is generally
indicated at 600, having a principal and rotational axis 611. The
engine 600 comprises, in axial flow series, an air intake 612, a
propulsive fan 613, a high-pressure compressor 614, combustion
equipment 615, a high-pressure turbine 616, a low-pressure turbine
617 and an exhaust nozzle 618. A nacelle 620 generally surrounds
the engine 600 and defines the intake 612.
[0041] The gas turbine engine 600 works in the conventional manner
so that air entering the intake 612 is accelerated by the fan 613
to produce two air flows: a first air flow into the high-pressure
compressor 614 and a second air flow which passes through a bypass
duct 621 to provide propulsive thrust. The high-pressure compressor
614 compresses the air flow directed into it before delivering that
air to the combustion equipment 615.
[0042] In the combustion equipment 615 the air flow is mixed with
fuel and the mixture combusted. The resultant hot combustion
products then expand through, and thereby drive the high and
low-pressure turbines 616, 617 before being exhausted through the
nozzle 618 to provide additional propulsive thrust. The high 616
and low 617 pressure turbines drive respectively the high pressure
compressor 614 and the fan 613, each by suitable interconnecting
shaft.
[0043] For example the blades of the high and low pressure turbines
616, 617 may be configured in accordance with blades of the
invention described herein.
[0044] Other gas turbine engines to which the present disclosure
may be applied may have alternative configurations. By way of
example such engines may have an alternative number of
interconnecting shafts (e.g. three) and/or an alternative number of
compressors and/or turbines. Further the engine may comprise a
gearbox provided in the drive train from a turbine to a compressor
and/or fan.
[0045] It will be understood that the invention is not limited to
the embodiments above-described and various modifications and
improvements can be made without departing from the concepts
described herein and claimed in the appended claims. Except where
mutually exclusive, any of the features may be employed separately
or in combination with any other features and the disclosure
extends to and includes all combinations and sub-combinations of
one or more features described herein.
* * * * *