U.S. patent application number 10/064470 was filed with the patent office on 2003-01-23 for double-wall blade for a turbine, particularly for aeronautical applications.
This patent application is currently assigned to FIATAVIO S.p.A.. Invention is credited to Ciacci, Paolo, Coutandin, Daniele, Schips, Carmine.
Application Number | 20030017051 10/064470 |
Document ID | / |
Family ID | 11459061 |
Filed Date | 2003-01-23 |
United States Patent
Application |
20030017051 |
Kind Code |
A1 |
Coutandin, Daniele ; et
al. |
January 23, 2003 |
Double-wall blade for a turbine, particularly for aeronautical
applications
Abstract
A double-wall blade for a turbine, particularly for aeronautical
applications, has a streamlined lateral wall, which extends along
an axis, surrounds the axis itself, and is defined by an inner wall
and an outer wall facing and integral with each other; the blade is
provided with inner channeling, which has a cavity into which, in
use, cooling air is admitted, and a number of ducts, which are
provided tangentially between the inner wall and outer wall, are
separated from one another by baffles which are transverse to the
axis and have respective intakes which are separate from one
another and communicate with the cavity in order, in use, each to
have a corresponding flow of cooling air pass through them.
Inventors: |
Coutandin, Daniele; (Torino,
IT) ; Schips, Carmine; (Torino, IT) ; Ciacci,
Paolo; (Torino, IT) |
Correspondence
Address: |
CARTER WHITE
HOWREY SIMON ARNOLD AND WHITE LLP
750 BERING DRIVE
HOUSTON
TX
77057
US
|
Assignee: |
FIATAVIO S.p.A.
|
Family ID: |
11459061 |
Appl. No.: |
10/064470 |
Filed: |
July 17, 2002 |
Current U.S.
Class: |
416/97R |
Current CPC
Class: |
F01D 17/162 20130101;
F01D 9/041 20130101; F05D 2240/81 20130101; Y02T 50/676 20130101;
F05D 2260/201 20130101; F01D 5/187 20130101; F05D 2260/22141
20130101; Y02T 50/673 20130101; Y02T 50/60 20130101 |
Class at
Publication: |
416/97.00R |
International
Class: |
B63H 001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2001 |
IT |
TO2001A000704 |
Claims
1. A double-wall blade (1) for a turbine, particularly for
aeronautical applications; the blade comprising a streamlined
lateral wall (20) extending along an axis (10), surrounding said
axis (10), and in turn comprising an inner wall (28) and an outer
wall (29) facing and integral with each other; and channeling means
(34) for a cooling fluid, comprising an intake cavity (15) for
intake of said cooling fluid into said blade (1), and a number of
cooling ducts (33) formed between said inner (28) and said outer
(29) wall and tangentially to said inner (28) and said outer (29)
wall; characterized in that said cooling ducts (33) extend in
respective directions crosswise to said axis (10) and parallel to
one another, are each airtight with respect to an adjacent duct
(33), and have respective intakes (38,39) separate from one another
and communicating with said intake cavity (15) so as to each guide
a relative flow of said cooling fluid, which does not mix with the
flow in the adjacent duct (33).
2. Blade according to claim 1, characterized in that said cooling
ducts (33) are separated and made airtight with respect to one
another by baffles (53) formed in one piece with said inner (28)
and said outer (29) wall.
3. Blade according to claim 2, characterized in that said baffles
(32) are disposed on respective planes at right-angles to said axis
(10).
4. Blade according to claim 1, characterized in that said
channeling means (34) additionally comprise means (44) for
regulation of the flow rate in order to diversify the flow rates of
said flows from one another.
5. Blade according to claim 4, characterized in that said means
(44) for regulation of the flow rate comprise for each said intake
(38,39) a corresponding hole (45,46) which has a cross-section of
passage calibrated in order to put the corresponding said cooling
duct (33) into communication with said intake cavity (15).
6. Blade according to claim 5, characterized in that said means
(44) for regulation of the flow rate are interposed between said
intake cavity (15) and said intakes (38,39).
7. Blade according to claim 6, characterized in that said means
(44) for regulation of the flow rate comprise an additional element
(44) which is connected integrally to said inner wall (28); said
holes (45,46) being provided in said additional element (44).
8. Blade according to claim 4, characterized in that said intake
cavity (15) is an axial cavity which is delimited by said inner
wall (28); said intakes (38,39) being provided through said inner
wall (28) along at least one axial row.
9. Blade according to claim 8, characterized in that said
streamlined lateral wall (20) has a leading edge (24); a trailing
edge (25); and a side (26) which is subjected to pressure and a
side (27) which is subjected to low pressure which extend between
said leading edge (24) and the trailing edge (25); the axial row of
said intakes (38,39) being provided at said leading edge (24).
10. Blade according to claim 9, characterized in that said cooling
ducts (33) comprise first ducts (36) provided along said side (26)
which is subjected to pressure and second ducts (37) provided along
said side (27) which is subjected to low pressure; means (35) for
separation being provided between said first duct (36) and second
duct (37) in order to define first intakes (38) in said first duct
(36) and second intakes (39) in said second duct (37).
11. Blade according to claim 10, said means (44) for regulation of
the flow rate comprising first (45) and second (46) holes which
have a calibrated cross-section of passage and are each associated
with a respective corresponding said first intake (38) and with a
corresponding said second intake (39).
12. Blade according to claim 1, characterized in that said
streamlined lateral wall (20) can be accommodated in an annular
duct (3) of said turbine, and in that it comprises a pair of end
walls (21)(22) which are disposed at the opposite axial ends of
said streamlined lateral wall (20), transversely to said axis (10)
and in use can be connected to respective platforms (4)(5) which
delimit said annular duct (3); said channeling means (34)
comprising at least one opening (64) which is provided through at
least one said end wall (21)(22).
13. Blade according to claim 12, characterized in that said
channeling means (34) comprise a number of said openings (64) for
each said end wall (21)(22).
14. Blade according to claim 12, characterized in that said
openings (64) communicate with said intake cavity (15) through said
cooling ducts (33).
15. Blade according to claim 14, characterized in that said
channeling means (34) comprise a first chamber (16) delimited by
said end walls (21)(22), by said inner wall (22) and by a wall (17)
which separates said intake cavity (15); said first chamber (16)
connecting said cooling ducts (33) and said openings (64).
16. Blade according to claim 1, characterized in that said
channeling means (34) comprise at least one passage (55) which is
provided in a tail portion (56) of said blade (1) and opens along a
trailing edge (25) of said streamlined lateral wall (20); said
cooling ducts (33) having respective outlets (54) which open into
said passage (55).
17. Blade according to claim 16, characterized in that said passage
(55) is delimited by said outer wall (29) and accommodates a number
of heat exchange elements (60) which project from said outer wall
(29).
18. Blade according to claim 15, characterized by comprising a
second chamber (66) formed in an intermediate position between said
intake cavity (15) and said first chamber (16); each said cooling
duct (33) comprising a relative first portion (69,70) having an
outlet (71,72) terminating in said second chamber (66), and a
relative second portion (73,74) having an intake (75,76)
terminating in said second chamber (66).
19. Blade according to claim 1, characterized in that said
channeling means (34) comprise turbulence generator means (51;52)
which are disposed in said cooling ducts (33).
20. Blade according to claim 19, characterized in that said
turbulence generator means comprise a number of ribs (51) which are
supported by at least one said inner wall (28) or outer wall (29)
and are transverse to a direction of advance (S) of said flows.
21. Blade according to claim 20, characterized in that said
turbulence generator means comprise a number of incisions (52)
which are provided in at least one said inner wall (28) or outer
wall (29) and are transverse to a direction of advance (S) of said
flows.
22. Blade according to claim 1, characterized in that said inner
wall (28) and outer wall (39) are spaced from one another by a
distance which is equal to the thickness of at least one said inner
wall (28) or outer wall (29).
23. Blade according to claim 1, characterized in that it comprises
pivoting portions (11,12) which are disposed on opposite axial
parts of said streamlined lateral wall (20) in order to rotate in
use around said axis (10).
Description
BACKGROUND OF INVENTION
[0001] The present invention relates to a double-wall blade for a
turbine, particularly for aeronautical applications.
[0002] As is known, a blade for a gas turbine of an aeronautical
engine has an axis which is incident with the axis of the turbine
and has a streamlined profile defined by a lateral wall, which, in
use, is lapped by gas at a relatively high temperature and must
therefore be continually cooled, for example by means of air
obtained from a compressor disposed upstream from the turbine, in
order to limit firstly the thermal stresses and secondly the
mechanical stresses caused by the thermal expansion of the lateral
wall itself.
[0003] Blades of the so-called double-wall type are known, in which
the lateral wall comprises an outer wall and an inner wall, which
are opposite, spaced from and integral with one another.
[0004] The need exists to provide a double-wall blade which, in
use, is distinguished by a temperature range which is as regular as
possible amongst the various areas of the lateral wall.
[0005] In particular, the need exists to provide a blade which has
regular efficiency of heat exchange along the lateral wall, for
example by limiting any areas of stagnation of the air which can
cool the lateral wall. In addition, the need exists to remove
different quantities of heat from amongst the various areas of the
lateral wall according to a substantially predetermined map, since
it is found experimentally that, in use, the lateral wall heats up
differently from one area to another, in particular along the axis
of the blade.
SUMMARY OF INVENTION
[0006] The object of the present invention is to provide a
double-wall blade for a turbine, particularly for aeronautical
applications, which makes it possible to fulfil the above-described
requirements simply and relatively economically.
[0007] According to the present invention, there is provided a
double-wall blade for a turbine, particularly for aeronautical
applications; the blade comprising a streamlined lateral wall
extending along an axis, surrounding said axis, and in turn
comprising an inner wall and an outer wall facing and integral with
each other; and channeling means for a cooling fluid, comprising an
intake cavity for intake of said cooling fluid into said blade, and
a number of cooling ducts formed between said inner and said outer
wall and tangentially to said inner and said outer wall;
characterized in that said cooling ducts are each airtight with
respect to an adjacent duct, and have respective intakes separate
from one another and communicating with said intake cavity so as to
each guide a relative flow of said cooling fluid, which does not
mix with the flow in the adjacent duct.
BRIEF DESCRIPTION OF DRAWINGS
[0008] The invention will now be described with reference to the
attached drawings, which illustrate a non-limiting embodiment of
the invention, in which:
[0009] FIG. 1 illustrates in transverse cross-section a preferred
embodiment of the double-wall blade for a turbine, particularly for
aeronautical applications, produced according to the present
invention;
[0010] FIG. 2 illustrates on an enlarged scale and in perspective
the blade in FIG. 1 in cross-section along the line II-II in FIG.
1;
[0011] FIG. 3 is a partial view on an enlarged scale of an inner
detail of the blade according to the arrow A in FIG. 1;
[0012] FIG. 4 illustrates in perspective and with parts removed for
the sake of clarity an end of the blade in FIGS. 1 and 2;
[0013] FIG. 5 illustrates in perspective, with parts removed for
the sake of clarity and on an enlarged scale, a tail portion of the
blade in FIGS. 1 and 2;
[0014] FIG. 6 illustrates on a highly enlarged scale and with parts
removed for the sake of clarity a detail of the blade in FIG.
2;
[0015] FIG. 7 is similar to FIG. 6 and illustrates a variation of
the detail in FIG. 6; and
[0016] FIG. 8 is similar to FIG. 1 and shows a further variation of
the blade in the above figures.
DETAILED DESCRIPTION
[0017] In FIGS. 1 and 2, 1 indicates as a whole a blade, in
particular a blade of a stator 2 (illustrated partially and
schematically) in an axial gas turbine with variable geometry for
an aeronautical engine, to which the following description refers
explicitly without detracting from generality. The stator 2 defines
an annular duct 3 (partially illustrated), which is provided around
the axis of the turbine (not illustrated) and through which, in
use, expanding gas at a high temperature passes and which is
delimited radially by a pair of platforms 4,5 opposite one another,
which support a row of blades 1.
[0018] The blade 1 has its own axis 10 which is incident with the
axis of the turbine and comprises two opposite end portions 11, 12,
which are coaxial to one another along the axis 10 and are pivoted
respectively on the platforms 4 and 5, in order to allow the blade
1 to rotate around the axis 10 itself in order to vary the capacity
or geometry of the stator 2, and thus the flow rate of the gases
which pass through the stator 2 itself.
[0019] The blade 1 additionally comprises an intermediate axial
portion 14, which is integral with the portions 11,12, extends
along the axis 10 in the duct 3 and delimits two inner cavities
15,16, which are separated from one another by a wall 17 parallel
to the axis 10, and from which the cavity 15 extends along the axis
10 itself and communicates with the exterior via two axial passages
18 provided in the portions 11,12.
[0020] The portion 14 comprises a lateral wall 20 and a pair of end
walls 21,22 which are disposed at the opposite axial ends of the
lateral wall 20, transverse to the axis 10, delimit the cavity 16
axially and are connected in a sliding manner to the platforms 4
and 5 respectively.
[0021] Again as illustrated in FIGS. 1 and 2, the lateral wall 20
surrounds the axis 10, is lapped in use by the gases which flow in
the duct 3 and defines a streamlined profile which has a leading
edge 24, a trailing edge 25, and a side or surface 26 which is
subjected to pressure and is concave towards the exterior, and a
side or surface 27 which is subjected to low pressure, and is
convex towards the exterior, which sides extend between the leading
edge 24 and the trailing edge 25.
[0022] The blade 1 is of the so-called double-wall type, i.e. the
lateral wall 20 comprises an inner wall 28 and an outer wall 29,
which face one another and are integral with one another. The walls
28,29 are spaced from one another by a distance which is
substantially equal to their thickness, measured along a direction
at right-angles to the walls 28,29 themselves, and are connected to
one another by a number of baffles 32 disposed on planes which are
parallel to one another and at right-angles to the axis 10.
[0023] The baffles 32 separate from one another axially a number of
ducts 33, which have the same cross-section of passage, extend
around the axis 10 tangentially to the walls 28,29 and constitute
part of channeling 34 which also comprises the cavities 15,16 and,
in use, can convey cooling air through the blade 1.
[0024] The baffles 32 are intersected by a baffle 35, which extends
axially along the leading edge 24 and projects from the outer wall
29 towards the interior in order to divide the ducts 33 into a
number of ducts 36 provided along the side 26 which is subjected to
pressure and into a number of ducts 37 which are provided along the
side 27 which is subjected to low pressure. The ducts 36,37 have
respective intakes 38,39, which are provided in the wall 28 along
two rows parallel to the axis 10, communicate with the cavity 15
and are separated from one another by the baffles 35 and 32 in
order, in use, to allow a corresponding flow of cooling air which
is distinct from the other flows to pass through each duct
36,37.
[0025] With reference to FIGS. 1 and 3, between the intakes 38,39
and the cavity 15 there is interposed a plate-type element 44,
which is connected integrally to the inner wall 28, preferably by
means of brazing, and for each intake 38,39 has a corresponding
circular through hole 45,46. The cross-sections of passage of the
holes 45,46 have respective diameters which differ from one another
and are calibrated according to the flow rate of cooling air which
is to be made to flow through each duct 36,37.
[0026] With reference to FIGS. 6 and 7, the inner wall 28 and outer
wall 29 have respective surfaces 48,49 which are opposite one
another in order to delimit the ducts 36,37 and support a number of
turbulence generators which can interrupt the final layer of the
flow of cooling air along the surfaces 48,49 themselves. These
turbulence generators are transverse to a direction S of advance of
the flow of cooling air of the duct 33 and are defined according to
FIG. 6 by ribs 51, or according to the variation in FIG. 7 by
incisions 52 provided along the surfaces 48,49.
[0027] As illustrated in FIGS. 1 and 5, each duct 36,37 ends in a
corresponding main outlet 54, which is aligned with the duct 36,37
itself and communicates with a slot 55 provided in a tail portion
56 of the blade 1. The slot 55 constitutes part of the channeling
34, is delimited by the end walls 21,22 and by two flat surfaces 58
of the outer wall 29, opens along the outlet edge 25 through a
number of ducts 59 and accommodates a number of cylindrical
portions or tabs 60, which connect the surfaces 58 to one
another.
[0028] As illustrated in FIGS. 1 and 4, each duct 36,37 has a
corresponding secondary outlet 61 (FIG. 1), which is provided
through the inner wall 28 in order to open into the cavity 16,
whereas the channeling 34 comprises a number of through holes 64
which are provided in the end walls 21,22 and communicate with the
cavity 16 in order, in use, to convey the cooling air which is
obtained from the outlets 61 and to cool the areas of connection
between the end walls 21,22 and the platforms 4,5.
[0029] FIG. 8 shows a blade 1a, the component parts of which are
indicated, where possible, using the same reference numbers as for
blade 1.
[0030] Blade 1 a differs from blade 1 by portion 14 comprising, in
addition to cavity 15,16, an intermediate chamber 66 separated from
cavity 15 by a wall 17, and from cavity 16 by a wall 67
substantially parallel to wall 17.
[0031] As of intakes 38,39, each duct 36,37 comprises a relative
first portion 69,70 terminating inside chamber 66 through an outlet
71,72 formed in inner wall 28; and a relative second portion 73,74
which extends from chamber 66 through a relative intake 75,76
formed in inner wall 28, and terminates with outlets 54,61.
[0032] In use, the cooling air, which is obtained for example from
a compressor disposed upstream from the turbine, is conveyed in a
manner which is known and is not described in detail through a
passage 18 in the cavity 15, from which it enters into each duct
36,37 through the corresponding hole 45,46 and the corresponding
intake 38,39. In each duct 36, 37 there flows a corresponding flow
of cooling air, the flow rate of which is substantially constant
and equal to a value which is dependent on the calibrated
cross-section of the corresponding hole 45,46, which is established
a priori for the same pressure difference between the cavity 15 and
the outlets 54,61 and in regular thermal conditions.
[0033] The baffles 32 are therefore formed in one piece with walls
28,29 (FIG. 2) and transmit heat by means of conduction from the
outer wall 29 which is lapped by the gases towards the inner wall
28, whereas the cooling air flows in the ducts 36,37 tangentially
to the baffles 32 and to the inner wall 28 and outer wall 29, thus
removing heat by convection. The part of the cooling air which
flows from the outlets 61 enters into the cavity 16 and passes
through the through holes 64 in order to form between the platforms
4,5 and the walls 21,22 a veil of air, which is particularly, but
not exclusively suitable for turbines with variable geometry,
since, as well as carrying out a cooling function, it prevents the
gases from filtering between the platforms 4,5 and the walls 21,22
on the side 26 which is subjected to pressure, towards the side 27
which is subjected to low pressure.
[0034] The part of the cooling air which flows from the outlets 53
flows into the slot 55 tangentially to the surfaces 58 and around
the cylindrical portions 60 in order to remove heat by convection
from the tail portion 56 until it is output into the duct 3. In
particular, the cylindrical portions 60 define respective thermal
bridges which transmit heat by conduction between the surfaces
58.
[0035] It is apparent from the foregoing description that the
channeling 34 makes it possible to cool the blade 1,1a such as to
obtain a substantially regular range of temperatures along the
lateral wall 20.
[0036] In fact, on the one hand, the channeling 34 makes it
possible to make flows of cooling air flow along a direction of
advance S which is tangential to the baffles 32 and to the walls
28,29, such that the efficiency of heat exchange between the
cooling air itself and the lateral wall 20 is relatively high, in
particular in comparison with other solutions in which transverse
jets of air are provided which cover the lateral wall of the
blade.
[0037] At the same time, the efficiency of heat exchange is regular
between the various areas of the lateral wall 20, since the ducts
33 have respective intakes and outlets which are different from one
another, and thus convey flows of air which are different from one
another and are free from localized losses of load or areas of
stagnation, caused for example by any elbowed sections, in relation
to the flows of air themselves.
[0038] The fact that walls 28,29 are connected integrally by
baffles 32 (FIG. 2) contributes towards making ducts 33 along axis
10 airtight and therefore independent of one another, and permits
material continuity between walls 28,29, so that the heat from the
gases in duct 3 flows by conduction from outer wall 29 to inner
wall 28 in the material interposed axially between-ducts 33, the
only thermal resistance being the conductivity of the material
itself.
[0039] If baffles 32 simply rested on one of walls 28, 29, as
opposed to being formed in one piece with walls 28, 29, the heat
would encounter greater thermal resistance due to the inevitable,
albeit minor, discontinuity of the material of baffles 32 and walls
28,29, thus reducing the amount of heat removed and impairing
thermal exchange efficiency.
[0040] In addition, if applicable, the baffles 32 which are
transverse to the axis 10 make it possible to differentiate from
one another the various flows of air in the ducts 33 along the axis
10.
[0041] In particular, the channeling 34 makes it possible to remove
heat according to a substantially predefined map, since it is
possible to establish a priori with good approximation the flow
rate of the flows of air between the various ducts 36,37, by
differentiating the flow rate of these flows both in the direction
parallel to the axis 10 and between the side which is subjected to
pressure 26 and the side which is subjected to low pressure 27.
Thus, for example, it is possible to admit a flow rate of air which
is greater in the ducts 36,37 which are provided along the axis 10
approximately halfway along the portion 14 in order to remove a
greater quantity of heat from the central portions of the lateral
wall 20, which in use are normally subjected to greater
heating.
[0042] The flow rate of the flows of cooling air is regulated by
the element 44 which can be added in a second stage to the
remaining part of the blade 1,1a so as to calibrate the holes
45,46, for example according to the type of aeronautical engine and
the position in which the blade 1,1a itself will be fitted.
[0043] The fact of cooling the walls 21,22 also makes it possible
to limit the thermal expansions, and thus the mechanical stresses
at the areas of connection of the blade 1,1a to the platforms 4,5,
whereas the fact of using only the part of the air which is
recuperated from the outlets 61 makes it possible not to affect
substantially the cooling of the lateral wall 20. This recuperation
is extremely simple, owing to the existence of the wall 17, which
firstly separates the cavities 15 and 16 from one another in a
manner sealed against fluid, and secondly contributes towards
strengthening the blade 1.
[0044] The ribs 51, the incisions 52 and the cylindrical portions
60 generate in the flows of cooling air turbulent motion which
increases the efficiency of the heat exchange.
[0045] Finally, the construction characteristics of blade 1a enable
it to be produced more easily in one piece.
[0046] Blade 1a, in fact, is produced using a disposable core (not
shown) made of ceramic material, in the form of a negative of the
material of blade 1a, and comprising an intermediate portion
eventually defining chamber 66. By virtue of outlets 71,72 and
intakes 75,76, the intermediate portion joins at an intermediate
point the lateral portions of the core eventually defining ducts 36
and 37, so that the core is easier to produce and stronger than the
one required for blade 1, and the lateral portions of the ducts of
which are joined slely at the ends, i.e. at intakes 38,39 and
outlets 54,61.
[0047] Finally it is apparent from the foregoing description that
modifications and variations which do not depart from the field of
protection of the present invention can be made to the blade 1 ,1a
described and illustrated.
[0048] In particular, the ducts 33 could have arrangements
different from that indicated by way of example, provided that they
are transverse to the axis 10, and or dimensions different from
those indicated by way of example. In addition, the ducts 33 could
have cross-sections of passage with dimensions which differ from
one another in order to have flow rates of air passing through them
which differ from one another.
[0049] In addition, cylindrical portions or tabs similar to the
cylindrical portions 60 could also be provided in the ducts 33.
[0050] Finally, the channeling 34 could also be provided in a fixed
stator blade or in a rotor blade.
* * * * *