U.S. patent number 3,765,796 [Application Number 05/249,283] was granted by the patent office on 1973-10-16 for filament reinforced rotor assembly.
Invention is credited to Walter Pilpel, Siddiq A. Sattar, Hans Stargardter.
United States Patent |
3,765,796 |
Stargardter , et
al. |
October 16, 1973 |
FILAMENT REINFORCED ROTOR ASSEMBLY
Abstract
This invention relates to a rotor assembly reinforced with a
filament wound composite ring. The rotor assembly comprises a
rotatable member having an annular cavity concentric to the
member's axis. The composite ring is positioned within the cavity
and has an inner diameter somewhat larger than the diameter of the
rotor surface about which the ring is disposed. During rotor
operation the rotor surface diameter increases and comes into
centrifugal load bearing relationship to the composite ring,
whereupon the ring carries a portion of the centrifugal loads thus
reducing the strength requirement of the rotatable member.
Inventors: |
Stargardter; Hans (Bloomfield,
CT), Sattar; Siddiq A. (Bolton, CT), Pilpel; Walter
(West Hartford, CT) |
Family
ID: |
22942805 |
Appl.
No.: |
05/249,283 |
Filed: |
May 1, 1972 |
Current U.S.
Class: |
416/244R;
416/230; 416/218; 416/244A |
Current CPC
Class: |
F01D
21/045 (20130101); F01D 5/30 (20130101); F01D
5/282 (20130101); Y02T 50/672 (20130101); Y02T
50/60 (20130101) |
Current International
Class: |
F01D
21/00 (20060101); F01D 21/04 (20060101); F01D
5/00 (20060101); F01D 5/30 (20060101); F01D
5/28 (20060101); F01d 005/30 () |
Field of
Search: |
;416/218,230,241A,244A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Powell, Jr.; Everette A.
Claims
Having thus described typical embodiments of our invention that
which we claim as new and desire to secure by Letters Patent of the
United States is:
1. A filament reinforced rotor assembly comprising:
an annular rotatable member including a plurality of blade
receiving slots circumferentially spaced about its periphery and
having an axis and having an annular cavity therein concentric with
said axis, said cavity including a radially outwardly facing
annular surface concentric with said axis, said annular surface
being interrupted by a plurality of circumferentially spaced
slots;
an annular filament reinforced composite ring located within said
cavity and having an inner diameter slightly larger than the
diameter of said annular surface when said rotor is at rest, the
difference in diameters being adapted to assure that said ring
comes into centrifugal load bearing relationship to said rotatable
member at rotor assembly operational speeds and temperatures due to
the different centrifugal and thermal growth rates of said
rotatable member and said composite ring; and
a plurality of circumferentially spaced Bellville springs disposed
within said slots, each of said springs having a radially outwardly
facing surface, said springs being compressed by said composite
ring during rotor assembly operation, and when compressed said
outwardly facing surface being flush with said annular surface and
defining a substantially smooth continuous annular surface
therewith with substantially no gaps and no sharp edges to damage
the composite ring.
2. The filament reinforced rotor assembly according to claim 1
wherein said rotatable member comprises two joined annular rings
cooperating to form said annular cavity.
3. The filament reinforced rotor assembly according to claim 2
wherein said annular cavity is airtight and filled with inert gas
to prevent contamination of said ring.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to the use of circumferentially wound
filaments to reinforce a rotor assembly.
2. Description of the Prior Art
The use of circumferentially wound filaments to reinforce a rotor
assembly is well known in the prior art as evidenced by U.S. Pat.
No. 3,393,436 to Blackhurst, et al., and British Patent No.
1,252,544 issued Apr. 9, 1970 to General Motors Corporation. The
chief advantage of these filaments is their high tensile strength
and lightweight; when these filaments are circumferentially wound
about a rotatable body their high tensile strength translates into
a high hoop strength giving the filaments the ability to carry
large centrifugal loads.
Two basic problems are encountered with the use of these filaments.
One is the difference in thermal and centrifugal expansion rates
between the filaments and noncomposite materials; the other problem
is that many of these filaments, depending upon the material from
which they are made, deteriorate in certain environments, such as
in a high temperature oxygen environment as is present in gas
turbine engines.
SUMMARY OF THE INVENTION
An object of the present invention is a lightweight rotor assembly
having high strength.
Another object of the present invention is a rotor assembly with
the ability to withstand a contaminating environment such as a high
temperature oxygen environment.
Accordingly, the present invention contemplates a rotor assembly
comprising a rotatable member having an annular cavity therein and
an annular filament wound composite ring located within said cavity
and radially spaced from a radially outwardly facing annular
surface of said cavity and adapted to carry a portion of the
centrifugal loads of said rotor assembly during operation. Having
the filaments located within the annular cavity protects them from
direct exposure to whatever environment happens to surround the
rotatable member. When the rotor assembly reaches operating
temperatures and speeds, the ring carries a portion of the assembly
centrifugal loads.
More particularly, flexible positioning means, such as springs, may
be positioned about the inner diameter of said ring to locate said
ring concentrically with respect to said rotatable member and to
allow differential growth between the ring and rotatable member.
Also, if required, the annular cavity may be filled with an inert
gas to further protect the filaments from contaminating
substances.
The foregoing and other objects, features and advantages of the
present invention will become more apparent in the light of the
following detailed description of preferred embodiments thereof as
illustrated in the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a sectional view of a portion of a turbine rotor
assembly.
FIG. 2 is a sectional view of the rotor assembly of FIG. 1 with the
blades and blade locks removed, taken along the line 2--2 of FIG.
1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As an example of a rotor assembly embodying the features of the
present invention consider the turbine rotor assembly shown in FIG.
1 and generally represented by the numeral 10. The turbine rotor
assembly 10 is suitably mounted within the turbine section (not
shown) of a gas turbine engine by means (not shown) well known to
one skilled in the art. The present invention is particularly
suited to use in a turbine rotor assembly due to the extremely high
temperatures and corrosive environment to which a turbine rotor
assembly is exposed; however, it should be obvious that this
invention may be useful in a compressor rotor assembly, or for that
matter in any rotor assembly subjected to any combination of high
temperatures, a corrosive environment and high centrifugal
loads.
Referring now to FIGS. 1 and 2, the rotor assembly 10 comprises a
rotatable member or disc 12 and a plurality of radially extending
circumferentially spaced blades 14 attached by suitable means to
the periphery 16 of said disc 12 such as by the use of a fir tree
root 18 and corresponding fir tree slots 20 shown in drawing and
well known in the art. Blade locks 22 or other suitable blade
retention means are also generally required. The blade attachment
means is simply a matter of choice and is not a part of the present
invention.
The disc 12 includes an annular cavity 24 formed therein.
Positioned within the annular cavity 24 is an annular filament
reinforced composite ring 26. The composite ring 26 comprises one
or more circumferentially wound filaments embedded in a matrix
material; in this embodiment it is contemplated that the filaments
be made from carbon and that the matrix material be made from
carbon. The filaments and matrix materials are a matter of choice
and depend on several factors such as maximum strength
requirements, maximum temperature requirements, and filament/matrix
thermal and stiffness compatibility. Examples of other possible
filament-matrix combinations are saphire-nickel, boron-titanium,
and graphite-graphite; the present invention, however, is not
limited to any particular filament-matrix combination. By
positioning the ring 26 within the cavity 24 the filaments and
matrix material are protected from direct contact from contaminants
which may surround the rotor assembly.
The annular cavity 24 has a radially outwardly facing surface 32
which in this exemplary embodiment is interrupted by a plurality of
circumferentially spaced slots 34 whose function will hereinafter
be made clear; however, for the purpose of this invention the
annular surface 32 may be continuous.
The composite ring 26 includes an inner annular surface 36 having a
diameter slightly larger than the diameter of the annular surface
32. This difference in diameters is necessary to account for the
differences in thermal and centrifugal growth rates between the
disc 12 and the composite ring 26; the composite ring 26 expands
considerably less than the disc 12 during operation, and the
difference in diameters is chosen such that the ring 26 will come
into centrifugal load bearing relationship to the disc 12 at
operating speeds and temperatures. In the present embodiment the
surface 36 will come into direct contact with the surface 32;
however, it is possible that some other hardware may be located
between the two surfaces.
To prevent unbalance within the rotor assembly 10 during transient
conditions (that is, until the ring 26 comes into centrifugal load
bearing relationship to the disc 12) flexible positioning means
such as a plurality of circumferentially spaced springs 38 locates
the ring 26 concentric to the annular surface 32. The springs 38
are of the well known Bellville type, and at least three of said
springs, equally spaced about the inner annular surface 36 of said
ring 26 are required to assure concentric positioning of the ring
26.
One requirement of the flexible positioning means is that it
permits essentially unhampered growth between the disc 12 and the
ring 26 until the ring comes into centrifugal load bearing
relationship to said disc 12; another requirement is that the
flexible positioning means does not operate to create unacceptable
stress concentrations within the composite ring. As regards the
latter requirement, the springs 38 are positioned within the slots
34 and are sized such that when fully compressed by the composite
ring 26 the ends 40, 42 of the spring 38 abut the sides 44, 46,
respectively, of the slot 34; if there were a gap between these
surfaces the composite material would tend to enter that gap and
the filaments might be damaged to the point of failure of the
composite ring. Additionally, the thickness of the spring 38 is the
same as the depth of the slot 34. Thus during operating conditions,
when the spring is fully compressed, the radially outwardly facing
surface 48 of the spring is flush with the surface 32 of the
annular cavity to form a substantially continuous annular surface
with no sharp edges to damage the composite ring 26.
As shown in FIG. 1 the disc 12 comprises left and right annular
rings 50, 52, respectively. Each of said annular rings 50, 52 has
an annular groove 54, 56, respectively. The annular rings 50, 52
are joined together by suitable means such as diffusion bonding at
58 and 60; it is also contemplated that the rings may be
mechanically joined. The grooves 44, 46 cooperate to form the
annular cavity 24.
Depending upon the particular materials chosen for the filaments
and the matrix material, it may be necessary or desirable to fill
the cavity 24 with an inert gas to assure that the filaments and
matrix material are not exposed to any contaminating substances
inside the cavity; in that case it is mandatory that the cavity be
airtight. Additionally, some filament and matrix materials may
react chemically with the disc material, damaging the filaments and
reducing the effective hoop strength of the composite ring. If that
is the case, it is desirable to insulate the composite ring from
the disc material. This might be accomplished in serveral ways, one
of which would be to encapsulate the composite ring within a tube
(not shown); another method might be to coat or line the walls of
the annular cavity with a suitable material.
Although the invention has been shown and described with respect to
a preferred embodiment thereof, it should be understood by those
skilled in the art that various changes and omissions in the form
and detail thereof may be made therein without departing from the
spirit and the scope of the invention.
* * * * *