Note: Descriptions are shown in the official language in which they were submitted.
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¦ TURBINE BLADE
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I BACKGROUND OF T~IE INVEN~ION
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This invention relates in general to turbine blades
and deals more particularly with an improved convectively cooled
turbine blade particularly adapted for use in the second stage
of an industrial gas turbine engine.
In gas turbine engines and the like a turbine operated
by burning gases drives a blower or compressor which furnishes
air to a burner. Such turbine engines operate at relatively high
temperatures. The capacity of such an engine is limited to a
large extent by the ability of the material from which the turbine
blades are made to withstand thermal stresses which develop at
such relatively high operating temperatures. The problem may be
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¦particularly ~evere in an industrial engine because oi the rela-
¦tively large slze and ~as~ oi englne parts. To enable higher
¦operatin~ temperatures nnd lncreased engine eiiiciency ~thout
¦rlsk of blade ia~lure, hollow convectively cooled tur~ine blades
¦are irequently utilized. Such blades generally have intricate
¦interior paqsageway~ which provlde torturou~ flow paths to as~ure
¦efficient cooling whereby all portlon~ oi the blades may be main-
talned at relatively unliorm te~perature. However, such blades
are dii~lcult and expen~ive to ~anuiacture. The present inven-
¦ tlon i9 concerned with thls proble~, and lt is the general aim
¦ of this invention to provlde an i~proved convectively cooled
turblne blade ~hlch ~atlsfie~ requirod de~lgn crlteria and whlcb
¦ ~ay be ~anuiactured ~t relatlvely low co~t and up-rated for in-
I crea~ed cooling without expensive reoperation or redesign.
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;¦ UMUARY 0~ THE INVENTION -~
In accordance wlth the present invention an i~proved
convectlvely cooled turbine blade has a three-pa~s cooling passage-
; way which include~ an inlet openlng at the root end o~ the turbine
and a plurality of connected pn~saee ~ections whlch define a
)reversing flow path through its blnde portion to an array of out-
let ~lot~ ~hlch e~tend along lts tralllng edge. Pede~tal~ or
turnin~ vane~ are located at turnin~ area~ w~thin the passa~eway
control separation o~ flow to prevent localized hot ~pot~. Ad-
itlonal pede~tals extend between the ~ldewalls ln a ~idchord
iortlon oi the pa~sageway to prevent sidewall vibration and en-
ance cooling eiflciency. A ~eterlng plate attached to the root
nd of the blade governs ~agnltude oi coollng ilow through the
urbine blade.
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In accordance with a particular embodiment of the
invention there is provided a turbine blade having a hollow
elongated body including longitudinally extending leading and
trailing edges and having a root portion at its inner end and
: a blade portion extending from said root portion and terminat-
ing at a closed tip at its outer end, said body having walls
defining a triple-pass fluid passageway including three series
connected passage sections providing a reversing fluid flow
path through said body from said inner end to said trailing
edge, said walls including a leading edge wall defining said
leading edge, opposing side walls extending between said leading
and trailing edges, and rib walls connected to and extending
transversely between said side walls, said rib walls including
: a forward rib wall spaced rearwardly from said leading edge _
wall and extending in a generally longitudinally inclined :
; direction within said blade portion from said inner end toward
said leading edge wall and in the direction of said outer end,
said forward rib wall having a terminal end longitudinally
spaced from said closed tip, said leading edge wall and said
forward rib wall partially defining a forward passage section
therebetween opening through said inner end and extending . :
through said root portion and into said blade portion in the
region of said leading edge and terminating within said blade :
portion at an outer turning region proximate said closed tip,
one part of said leading edge wall defining the portion of said
forward passage section within said blade portion having an
abrupt forward offset relative to another part of said leading
edge wall defining 'che portion of said forward passage section
` within said root portion, said forward offset occurring prox-
30 imate the junction of said root and blade portions, said
~ ~ forward passage section having an abruptly enlarged cross-
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sectional area at the junction of said root and blade portions
and generally converging within said blade portion and toward
said outer turning region, said rib walls including a rear .
rib wall spaced rearwardly from said forward rib wall and
: extending in a generally longitudinally inclined direction from -
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said closed tip toward said forward rib wall and in the general ~
direction of said inner end, said rear rib wall having a ter- -
minal end proximate the junction of said root and blade portions,
: said forward rib wall and said rear rib wall partially defining
a midchord passage section communicating with said forward
passage section at said outer turning region between the
terminal end of said forward rib wall and said closed tip, said
midchOrd passage section converging within said blade portion
and in the direction of said inner end, said rear wall rib
and said trailing edge partially defining a rear passage
section within said blade portion in the region of said trail- .
.l ing edge and terminating at said closed tip, said rear passage
section communicating with said midchord passage section at an
inner end, said rear passage section converging within said
body portion and in the direction of said closed tip, said body
including a longitudinally spaced series of partitions conn-
ected to and extending between said side walls generally ad-
jacent.said trailing edge and defining a longitudinal series
of slots opening through said trailing edge and communicating
;, with said rear passage section, said body having a plurality of
pedestal members connected to and extending between said side
walls within said forward passage section and proximate the
junction of said root and blade portions.
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BRIEF-DEscRIprIoN OF TlilE D~AWING
Fig. 1 19 a longitudinal ~ectional view oi an airfoil
¦shaped turbine blade embodying the pre~ent inventlon.
¦ Fig. 2 is a ~omewbat enlar~ed ~rag~entary sectio~al
¦view taken along the line 2-2 oi Fig. 1.
~: ¦ ~ig. 3 i9 a ~ragmeutary lo~gitudinal sectional view
¦si~ilar to Flg. l a~d shows a modified iorm o~ the turbine blade
¦ oi Fig. 1.
I DETA~LED, DESCRIPTION~OF .PREFERn~D EUBODI~ENT
) I Turning no~ to the dra~lng, the lnvention is lllustrated . -:
: I and described wlth r~erence to an air cooled turbine blade, de-
¦ signated generally by the numieral 10, and partlcularly adapted
ior u~e ln the ~econd fitage of an axial ~low ga~ turbine engine ...
o~ an lndu~tsial type (not ~ho~n) wbiich hias a plurality of alr-
~i I ~oil shaped turbine rotox blades mounted in an~ularly ~paced re- : :
¦ lation on a rotor disc. The turbine blade 10 has a more or le~s .
: I conYentional outer confi6uration and comprlseæ a hollow elo~igatQd
body, lndicated generally at 12, which i~cludes a concave inner
¦ ~lde ~all 14 and an oppo~ing convex outer sidewall 16. The slde-
~) ¦ wall8 terminate at longitudlnally extendlng leading and trailing ..
edgee lndlcated, re6pectlvely at 18 a~id 20. The body 12 further
lnclude~ a root portion 22 at one end and elongated blade portion
¦ 24 whlch extends iro~ the root portlon and termlnates at a tlp
I 2ff, whlch 1~ clo~ed by a separately ln~erted sealing plate 28. : :
S A platiorm 30 extendY outwardly ~rom the body at the ju~iction ~ :, between the root and blade portloDi. The root portion i8 pre- .
; ~erablg provlded with attach~ient ~houlders (not ~howni) whlch may ~
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have a conventionnl fir tree configuration for mounting the tur-
b1ne blade 10 in complementary ~lot~ in a rotor disc.
In accordance wlth the present invention, a three-
pass ~eries ~lo~ cooling pas~a~eway sys~;rS is provided ~or con-
vectively cooling the blade 10 and lndicated generally by the
nu~eral 3~. The passageway system 32 oompri~es three ~eries
connected passage sections 34, 36 and 38 which generall~ deiine
a rever~lng fluid ~low path between the inner or root end o~
the turbine blade 10 and a lollgltudinally spaced ~erie~ of out-
let passage~ or ~lots 40, 40 ~ormed in the trailing edge 20. The
pa~sageway system 32 further includes two blind passage sectlons
42 and 44 whl¢h are rormed ~ithln the root portion 22 and which
merge wlth the pas~age ~ection~ 36 and 38 proximate the junction
o~ the latter sectlons.
The pa~age ~ection 34 i~ de~ined, in part, by the
i~ner wall of the leading edge }8, the latter wall being designed
by the numeral 46. It will be noted that the part o~ the wall
46 which deilnes the portlon o~ the passage sectlon 34 withln
;~ the leading ed~e of the blade portion 20 i~ ~orwardly o~set ~rom
the part of the wall 46 whlch derine8 the portion o~ the passage
~ectlon 36 within the root portlon 22~ Thi~ of~et o¢curs pro-
xi~ate the Junction between tbe root and blade portions. The
pa~sageway 34 i~ rurther de~ined by a wall rib 48 which extends
txan~versely between the ~idewaIls 14 and 16 and is spaced rear-
3 wardly o~ the wall 46. The wall rib 48 extends ~rom the root
: end oi the turblne blade 10 toward its tlp 26 and terminates in
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longitudinally spaced relation to the sealing plate 28. As
shown in Fig. 1, the wall rib 48 is outwardly inclined in the
direction of the leading edge 18, so that the passageway section
34 generally converges in the direction of the tip 26. ~ -
The rear passageway 36, is defined in part by the wall
rib 46, and is further defined by another wall rib 50 which
extends from the tip end 26 and in the direction of the root end -
of the turbine blade. The wall rib 50 extends between the side-
walls 14 and 16 and is inclined inwardly and in the direction of
the wall rib 48 relative to the longitudinal axis of the turbine
blade. The wall rib 50 terminates proximate the junction be-
tween the root and blade portions 22 and 24, substantially as
' shown. Another wall rib 52 extends from the root end in the
direction of the tip 26 and terminates in longitudinally spaced
; relation to the wall rib 50. The wall rib 52 cooperates with
the portion of the wall rib 48 to define the blind passageway
42 and also cooperates with a trailing edge wall 54 to define
the other blind passage section 44.
The rear passage section 38 extends through the blade
portion 24 in the region of its trailing edge and is defined in
part by the wall rib 50. A plurality of partitions or elongated
pedestal members 56, 56 are arranged in Venetian blind array
and extend between the sidewalls 14 and 16 generally adjacent
the trailing edge 20 to define the slots 40, 40 which commun-
icate with the rear passage section 38.
Four generally cylindrical pedestal members 58, 58
disposed within the forward passage section 34 and extend between ~
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the sidewalls 14 and 16 proximate the junction of the rib and -
blade portions 22 and 24 at a turn in the forward passage section
34. The latter pedestals are disposed in a generally in-line
arrangement inclined to the longitudinal axis of the turbine
blade, substantially as shown in Fig. 1. A plurality of gener-
ally cylindrical pedestal members 60, 60 are disposed within the
` midchord passageway section 36 and extend between the sidewalls
14 and 16. Two additional pedestal mernbers 62, 62, which extend
between the sidewalls, are disposed at the entry end of the rear
10 passage section 38 proximate the junction between the root and
blade portions and adjacent the downstream end of the inner turn
in the passageway system 32.
A pair of airfoil shaped turning vanes 64 and 66 extend
between the sidewalls 14 and 16 proximate the entry end of the
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i midchord passage section 36 and generally between the terminal
end of the wall rib 48 and the sealing plate 28, substantially
as shown in Fig. 1. A metering plate 68 attached to the inner
end of the turbine blade 10 provides closures for the blind pas-
sageways 42 and 44 and has a metering orifice 70 which communi-
20 cates with the passage section 34. The metering plate 68 is
preferably welded or brazed to the inner end of the body 12, which
is preferably made by a casting process. To facilitate casting
the body 12 is made with an opening at its tip end 26. The
latter opening is closed by the sealing plate 28, which, as
shown, is received within a slot in the tip end of the body.
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Cooling air ~rom the blade disc (not shown) enters the
forward passage section 34 through the metering orliice 70. The
cross-sectional area o~ the ~orwar~ passage sectlo~ 34 increases
abruptly at the junction between the root and blade portions due :
: ~o the ~orward o~fset oi the leading edge inner wall 46. The
four pedestals 58, 58 prevent local flow separatio~ at this turn
in the flow path by causlng turbulence in the ~low and iorcing it
outwardly against the inner wall 46 and inwardly agal~t the wall ~ : :
rib 48 thereby preventing the development o~ a hot ~pot in this
region o~ the blade. The cooling air ~lows the full spa~ o~ the
blade through the iorward pa~sa~e section 34 until it reache~ the .,
tip end ~6 where it i~ bloc~ed by the ~ealing plate as. The
turning vane~ 64 and 66 a6sist iR directing the ~low o~ cooling
air into the ~idchord pas~age section 36, as lndicated by the
~low arrows ln the Flg. 1, and control ~eparation o~ ~low to pre-
: vent development o~ hot spots in thi~ outer turning regio~.
: The pedestal ~embers 60, 60 in the midchord pa~sage ~ ;
section 36 preveut sidewall vlbration and cause turbulent ~lou
within the pa~sage ~ectlon 36 which re9ults in n scrubblng action
D on the wall~ o~ the passa~e ~ection ~or more ei~lcient coollng.
~ter ~lowlng through the ~idchord pas~age section 36 the CooliR~
air rounds the inner end o~ the wall rib 50 at a~ inner turning
region and passes over the pedestal members 62, 62 and into the : .
reax passage ~ectlon 38 where it emlts irom the slots 40-4C.at
.5 the inner end o~ the rear passage ~ection 38 generally ad~acent .
the lnner turnlng reglon, lndlcated by the ~low arrow in Flg. 1.
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The pedestal members 62, 62 prevent flow separation and cause
flow to emit from the trailing edge slots 40-40 near the inner
end of the blade portion 20, thereby preventing development of
a hot spot in this region.
The metering plate 60 governs the magnitude of cooling
flow through the turbine blade 10 and permits future modification
of the blade cooling system, such as an up-rating of the cooling
system, without expensive alteration or blade redesign. Present-
ly, .5% engine air is used to cool the turbine blade 10. How-
ever, the criteria in determining the amount of cooling air whichmust flow through the blade is determined by the maximum temp-
erature to which the blade will be subjected. A 1500 F max-
imum blade temperature is thought to be desirable to prevent
fuel products deposits from sticking to the blade.
~ In Fig. 3 there is shown a turbine blade lOa for a
;j "first generation" gas turbine engine. The hollow body 12a of
the blade lOa is substantially identical to the body 12 of the
previously described blade 10. However, the separate plate 68a,
which is attached to the inner end of the body 12a serves only
as a closure for the blind passage section 42a and 44a. The
passage section 34a which opens through the inner end of the body
allows maximum cooling air flow through the passage system 32a.
It will now be apparent that the magnitude of cooling
flow through the turbine blade may be altered by attaching to
the inner end of the body a separate metering plate having a
metering orifice of appropriate size. Thus, the rating of the
cooling system ~ay be changed without altering the body of the
turbine blade.
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