US2928650A - Rotor assemblies for gas turbine engines - Google Patents

Description

March 15, 1960 s. G. HOOKER ETAL 2,928,650

ROTOR ASSEMBLIES FOR GAS TURBINE ENGINES Filed NOV. 15, 1954 ROTCR ASSEIVIBLIES FOR GAS TURBINE ENGINES Application November 15, 1954, Serial No. 468,974

Claims priority, application Great Britain November '20, 1953 4 Claims. (Cl. 253-3915) This invention concerns rotor assemblies for gas turbine engines, which ,rotor assemblies are of the kind (hereinafter referred to as of the kind described) comprising a turbine rotor having a blade-carrying disc and a ring of turbine blades carried by the blade-carrying disc around its periphery, and a cooling-air-guide disc arranged for rotation co-axially with the blade-carrying disc, said cooling-air-guide disc defining with the blade carrying disc a. space through which cooling air may pass from the region of the centre of the blade-carrying disc to the region of its rim.

Hitherto such cooling-air-guide discs have in some cases been welded at their rims. to the blade-carrying disc, but this is not practicable with some materials or when it is desired that the cooling-air-guide'disc should extend to a'greater diameter than the tips of blade roots housed in slots extending from faceto face of the bladecarrying disc. In other cases the cooling air guide disc has been clamped to a hub portion of the blade-carrying disc andhas been provided with a ring of openings around the hub portion for theientry of the cooling air. This arrangement has the drawback that the cooling air openings cause high stress concentrations in the cooling-airguide disc and also that at. high rotational speeds ofthe rotorassembly air does not pass readilythrough the openings.

According to the present invention, thereis provided a rotor assembly of the .kind described, wherein the co'oling-air-guide disc has arim bearingagainst a substantially axially-facing surface on the turbine rotor and a central aperture by which it is drivingly mounted upon a member attached to the blade-carrying disc, which member is provided with passages through which cooling air can pass into said space. I

According to a feature of the present invention, said member mayhave a ring of spaced radially-extending 7 2 saidsubstantially axially-facing surfaceson the turbine rotor.

3 in Figure 1 with the cooling-air-guide disc removed;

Referring to Figures 1 and 2,. the rotor assembly co'mprises a hollow shaft 1 provided with a coupling flange 2 attached by bolts 3 to aturbine rotor having a bladecarrying disc 4 and a ring of blades 10 carried by the disc 4. The disc 4 has a thickened hub portion 5 surround: ing a central bore 6, the axis of rotation of the assembly being shown at 7. The disc 4 has slots 8 around'its periphery and extending from face to face of the disc. In each slot is mounted, by its root 9, a blade 10. In the example being described, the roots 9 are of fir-tree formation, and the blades v10 have internal passages, not shown, to which cooling air is admitted through a bore 11 extending through the blade root from a port 12 in one axial end face of each blade root.

Cooling air passes from the region of the centre of the assembly to the ports 12 through a space 13 formed be-.

tween the disc 4 and a cooling-air-guide disc 14 of annular configuration which is mounted coaxially. with the disc 4 for rotation therewith and which has a rim 15 bearing against axially facing'surfaces 16 (see Figure 3) spoke-like projections, the spaces between said projections constituting said passages.

.When the above mentioned feature is adopted it is preferred. that the cooling-air-guide disc be drivingly mounted upon said spaced spoke-like projections. Preferably, also, when said spaced spoke-like projections are provided, said projections are so shaped in cross-sectional planes that during operation of the rotor assembly they act as vanes which promote air flow into the space beformed on the turbine rotor. .In the example being described, the surfaces 16 are formed on the end surfaces of those parts of the blade roots which are disposed;

radially-outward and axially forward of the peripheral edge of the disc 4 and are contiguous to form a continuous ring. The disc 14, therefore, extends to agreater diameter than the radially inner ends 911 of the blade I roots 9. The disc 14is of forged material and has a central aperture 17 which receives a member generally indicated at 18 attached to the disc 4 by the coupling bolts 3. The member 18 has an apertured central portion 18a. Since only a single aperture 17 has to be provided at the centre of the disc 14 the disc can be designed to avoid high stress concentrations during operation of the rotor assembly. i r i i I The member 18 is formed around its periphery with aring of equally spaced radially-directed spoke-like projections or vanes 19 thespaces 20 between which constitute passages for cooling air to pass into the space 13, r

tion and rotating at high speed in the direction of the arrow 21, and the disc 14 is preferably mounted directly upon the radially outer ends of the projections, i.e. without an intermediate rim, asshown so that this machining operation is facilitated. As the member 18 is of comparatively small diameter and therefore unlike the disc 14 is not subjected to very great centrifugal stresses during operation of the rotor assembly, it is conveniently made as a casting in a suitable material of snfiicient tensile strength.

To ensure that centrifugal forces acting upon the disc 14 when the rotor assembly is in operation tend to maintain the rim 15 of the latter pressed against the end surl atented Mar. 15, 1960 A rotor assemly according to the present invention faces ofthe bladeroots that form surfaces 16 tbe disc V lasagna? .7 l

14 is slightly dished towards the disc 4 so that radial v:

from.radial lines sucheasafi, whichiareperpendicular :to

the axis of rotation. 7 and pass through the outermost;

mid-thickness points of ,the disc .14, such as .24, 1 towards the .disc 4 .on the side of .the. mid-thickness points .nearer the axis ottrotationfi, .In determining the outermostmidthickness Qpoints wsuch .as 24 it .is to 'be nnderstbojd that the'local thickening of the rim fis disregarded.

We.claim: t 7 1 a, 1.For agas turbine engine, the sco'mbinationiwith a turbine. rotor c'omprising a blade carrying disc having an outer periphery and a. hubportion an'da ringoi turbine blades Icarried 'by'. said blade-carrying .disc round its ,pe-' ,ripheiry, eaener said turbine bladeslh'av'in'g a' substantially axially-facingsurface adjacent the outer, periphery ofsaid mid-thickness lines, such;asi22, of the disc 14 diverge disc, 'of, a mernber attached "to said blade-carrying jdisc coaxially'therewith, a cooling-air-guide disc spaced, axially from said blade-carrying disc, said cooling-.air-guide disc" being of annular configuration and having a rimbearing freely against said axially facing surfaces and having 1 only a singlecentral aperture providing the cooling-airguide disc with an inner periphery within which said member is. located, the. innerperiphery of saidtcoolin'gdisc with aninner periphery within which saidmem ber is located, tbeinner periphery of said 'cooling-air guide, 1

disc engaging and supported .on said member'for rotation with the member, said cooling-air-guide disc, said memher and said blade-carrying disctogether defining a space through which cooling air may pass from the region of the 'hub-'portion-:dfxsaid' blade-carrying fiiSC ftO tht, region of said axially-facing surface of each. blade, said member havingpassages adjacentsaid Lhnb, portion through which cooling air can passfinto said ,space radial amid-thickness lines or the cooling-air-guide disc diverging :fl'OlIl: radial lines perpendicular to the axis of said turbine rotor which pass through the outermost midfthickness points -of-the cooling-air guidedisc towardtsaid ,bladeacarryir g disc on the side of said mid-thicknessvpointsrnearer the axis of i said turbinerotor.

4. For a gas-turbine engine, the combination with a turbine rotor comprising a blade-carrying disc having an outer peripheryhnd "a hub portion-and a ring of turbine bladescarried byjsaid vblade-carrying disc around its pe riphery,cach of said turbinebla'des having .a substantially axially facing surface adjacent theouter periphery of said disc,of amember *attachedfto said'bladc-carrying disc air-guide disc engaging and supported on saidmember for rotationwith the member, said cooling-aifiguide disc,"

said member and saidblade-carrying disc togetherude- 7 fining a spacethroughwhich cooling air may pass from the regionrof the hub portion'of said blade-carrying disc V to the rcgionYof said axiallyfacing surface of each'blajd e,

said memberhaving-passages adjacent said hub :portion 1 throughwhichco'olingfair can pass intojs'aid space, said cool ing-air-guide ldiSC being "dished :towards said blade carrying "disc whereby during rotation of the turbine- .rotor-member blade carrying disc assembly the centrifugal force acting onthe cooling ainguideidis'c tends to main-,

tain the rim of the cooling-air-guide"disc'pressed against said axially facing surfaces of the blades.I '2. The combination as claimed in claim'fl, wherein radial mid-thickness lines er the cooling-air guide disc diverge, from radial 'lines per-pendicularto; the axis of said turbine rotor which pass through theouterrnost mid- 1 7 thickness points "ofthe "coolingair -guide disc, towards said blade=carrying disc on the side' of said mid-thickness points-nearer the axis of'said turbine rotor.

3. Fory a gas turbine engine, the "COI'HDIDZITJOII' with a turbine rotor comprising-a blade-carrying disc having an 7 outer periphery anda hub portion and -a ring of turbine blades carried'by said blade-carrying-disc round'its periphery,'eachof said turbine blades having a substantially-- axially facing surface adjacentthe outer periphery of said 7 disc, of'a member attached tosaid blade-carrying disc i coaxially therewith, a cooling-air-guidedisc spaced axially I from said blade-carryingdisc, said cooling-airguide disc i being nfannular configuraton and having a rim' bearing freely against said axially facing surfaces and having only a single central aperture providing the cooling-ainguide coaxially therewithgsaid member comprisinga central portion having a periphery and a ring of vanes carried-on 7 said central portion and spaced apart aroundlits periph ery, said vanes each projecting radially of said"central portion, 'a cooling-air-guide disc spaced axially from said blade-carrying disc, said coolingairguide disc*being oft annular configuration -an'd "having' fa rim"bfearin'g freely against-said axially facing surfaces and: having only :a single central aperture -providing the cooling air-guide disc with laninner periphery within whichi-said member is located, the-inner periphery of said; cooling-air-guide disc engaging and supported on the outer ends of'said vanes for rotating with said member, said cooling-airguide disc,- said; member and said blade-carrying discito 1 getherdefining-a space'through 'which cooling air a may pass from theregion o'f the hub portion of said blade carrying disc'to the region of" said axially facing surfaces, said vanes, during rotation ofthe turbine rotor, promoting air flow'intossaid :spa'ce, radial mid-thickness lines of the 'coolingvair-gui-de disc diverging fromradialj lines perpendicular to the axis of said turbine rotor which-pass through ;the' outermost mid-thickness points of the coolingair-guide disc towards,saidfblade-carrying iiisc on the side,

. of-said mid-thickness points nearerthe axisofsaid'turbinc 978,608 France .Nov.;29.:1950

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