U.S. patent number 3,677,662 [Application Number 05/079,550] was granted by the patent office on 1972-07-18 for multilayer ring damped turbomachine rotor assembly.
This patent grant is currently assigned to Avco Corporation. Invention is credited to Val Cronstedt.
United States Patent |
3,677,662 |
Cronstedt |
July 18, 1972 |
MULTILAYER RING DAMPED TURBOMACHINE ROTOR ASSEMBLY
Abstract
The disclosure illustrates a centrifugal compressor comprising
an inducer hub telescoped over an adjacent shoulder of an impeller
hub. The inducer hub has an inner annular surface which receives a
plurality of stacked annular relatively thin split ring elements.
When the compressor rotates at high r.p.m.'s the split rings
frictionally engage one another and the inner annular surface of
the inducer hub to provide a highly effective means for damping
vibrations in the inducer.
Inventors: |
Cronstedt; Val (Williamsport,
PA) |
Assignee: |
Avco Corporation (Williamsport,
PA)
|
Family
ID: |
22151259 |
Appl.
No.: |
05/079,550 |
Filed: |
October 9, 1970 |
Current U.S.
Class: |
416/183; 416/500;
416/244R |
Current CPC
Class: |
F01D
5/045 (20130101); Y10S 416/50 (20130101) |
Current International
Class: |
F01D
5/04 (20060101); F01D 5/02 (20060101); F01d
005/26 () |
Field of
Search: |
;416/183,244,500,119,190,242,198 ;74/574 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwadron; Martin P.
Assistant Examiner: Schimikowski; Clemens
Claims
Having thus described the invention, what is claimed as novel and
desired to be secured by Letters Patent of the United States
is:
1. A damped turbomachine rotor assembly adapted to rotate at
relatively high rates, said rotor assembly comprising:
a generally annular hub spaced outward from its axis of rotation
having an outer surface defining the inner bounds of a flow path
for fluid and an inner annular surface;
a plurality of blades extending radially outward from the outer
surface of said hub substantially radially outward from said inner
annular surface, said blades being subjected to vibratory bending
forces, thereby producing deflections in said interior surface;
and
a plurality of stacked, annular, relatively thin ring elements
coaxial with one another and received within the inner annular
surface of the hub member and having the outermost ring element
conforming thereto, whereby centrifugal force urges said ring
members into frictional engagement with one another and the
outermost ring element with the inner surface of said hub for
damping vibrations.
2. A rotor assembly as in claim 1 wherein each of said ring
elements are split and the outermost ring element has an outside
diameter slightly larger than the diameter of said inner annular
surface, whereby the stacked ring elements are compressed for
insertion into said inner annular surface and are yieldably
maintained in position.
3. A rotor assembly as in claim 1 wherein said hub and blades
comprise an inducer of a centrifugal radial outflow compressor and
said rotor assembly further comprises:
a downstream radial outflow impeller hub;
a plurality of blades extending radially outward from said impeller
hub, said blades being out of contact with said inducer blades.
4. A rotor assembly as in claim 3 wherein said stacked rings each
have a thickness of approximately 0.001 inch.
Description
The present invention relates to turbomachine rotor assemblies and
more particularly to assemblies of the type that have provisions
for damping.
In the gas turbine art there have been numerous approaches directed
at providing damping in rotor assemblies. A departure from the
usual method of providing damping at the tips of rotor blades may
be found in the copending patent application entitled "Damped
Turbomachine Rotor Assembly" in the name of Wayne C. Shank, Ser.
No. 77,969, filed Oct. 5, 1970, and of common assignment with the
present invention. The present invention constitutes an improvement
over this copending application.
It is an object of the present invention to provide a highly
effective means for damping a turbomachine rotor.
The above end is achieved by a damped turbomachine rotor comprising
a generally annular hub spaced outward from its axis of rotation
and having an inner annular surface. A plurality of annular,
relatively thin stacked ring elements are received within and
conform to the surface so that centrifugal force urges the ring
members into frictional engagement with one another and with the
inner surface to damp vibrations in the blades.
The above and other related objects and features of the present
invention will be apparent from a reading of the description of the
accompanying drawing and the novelty thereof pointed out in the
appended claims.
In the drawing:
FIG. 1 is a longitudinal sectional view of a centrifugal compressor
rotor assembly embodying the present invention;
FIG. 2 is a view taken on lines 2--2 of FIG. 1 which illustrates
the fundamental mode of vibration of the compressor hub;
FIG. 3 is a perspective illustration of a plurality of split ring
elements incorporated in the impeller of FIG. 1.
Referring now to FIG. 1, there is shown a centrifugal compressor
rotor assembly 10 with which the present invention may be used. The
rotor assembly comprises a first generally annular shaped hub 12
spaced outwardly from its axis of rotation A. The hub 12 has a
series of radially extending blades 14 to form the impeller portion
of the rotor assembly 10. A second hub 16 is positioned upstream of
the hub 12 and is also annular and spaced outwardly from the axis
of rotation A. An annular surface 15 is formed on the inner side of
hub 16. Hub 16 has a series of inducer blades 18 which extend
radially outward but are cambered so as to efficiently receive air
from an axially directed inlet, shown in phantom and designated by
reference character 21. The inducer blades 18 are spaced from but
correspond with the impeller blades 14 to form a generally annular
flow path across the centrifugal compressor rotor 10.
Hub 12 has an elongated shaft portion 26 over which hub 16 is
telescoped. A tapered pilot diameter 28 on the elongated shaft
portion 26 and a corresponding tapered diameter 30 on the inducer
hub 16 centers it on elongated shaft portion 26 of hub 16. An
internally threaded nut 32 is screwed onto the threaded portion 35
of the elongated portion 26 by a suitable tool which engages slots
34 in element 32. Element 32 holds the inducer hub 16 against a
shoulder 20 on the impeller hub 12.
A plurality of annular, relatively thin ring elements 36 are
received within and conform to the inner annular surface 15 of hub
12. Preferably the rings 36 are split at 38, as shown in FIG. 3
which shows the individual rings peeled away for illustrative
purposes. The rings are formed so that they fit within one another
in stacked fashion and the outermost ring element has an outside
diameter slightly greater than the diameter of the inner annular
surface 15. The plurality of ring elements 36 are then compressed
for insertion into the inner annular surface and once they are in
position they are yieldably maintained in place.
In operation the centrifugal compressor rotor assembly many rotates
at a high rate of speed. Due to manny exciting forces the blades 18
and 14 tend to vibrate in their several modes. As shown in FIG. 2,
the resultant vibration causes deflection of the inner annular
surface 15 of annular inducer hub 16 from which the blades 18
extend radially. The deflection of the hub for a swing of blades 18
to the left is shown in exaggerated proportion by the phantom lines
of FIG. 2. It can be seen that this deflection generally resembles
a sine wave superimposed on the annular shape of the inner annular
surface 15. A swing of the blades to the right causes a similar
deflection in the opposite direction.
The outermost ring element 36 is urged radially outward by
centrifugal force into frictional engagement with the deflected
portion of the inner annular surface 15. In addition, the adjacent
ring element 36 is urged against the outermost ring element by
centrifugal force. Centrifugal force urges each of the ring
elements into its adjacent outer element.
As the blades swing, the ridges and valleys in the inner annular
surface 15 rub against the outermost ring element 36. The resultant
frictional engagement of this element and the other ring elements
absorbs the energy created by the blade vibration.
It can be seen that the provision of the multilayered rings greatly
increases the surface area over which there is frictional
engagement. This provides a substantial increase in damping over
the copending application referred to above without necessitating
any increase in the diameter of the inner annular surface 15. The
reason for this is that the individual ring elements have a very
thin section, for example, 0.001 inch thick, and the effective
radius of the rings is approximately that of the inner annular
surface. This causes approximately an equal centrifugal force on
the rings when compared to the force on the single ring set forth
in the above patent application.
For a rotational speed of over 50,000 r.p.m. the weight of the
individual rings is magnified approximately 100,000 times their
radius in inches. However, the frictional area for damping is
greatly increased over the copending application referred to above,
since it has a single ring whose outer surface only is in
frictional contact. In the multilayer arrangement both sides of
each ring element, except for the innermost element, provide a
frictional engaging surface. It can be seen that the rubbing area
is increased to a high degree, thereby providing a very effective
means to damp the vibrations.
While the present invention has been described in connection with
the inducer portion of a centrifugal compressor, it is believed
that those skilled in the art can adapt the invention to other
turbomachine rotors, such as axial flow type or centripetal turbine
assemblies without departing from the spirit and scope of the
present invention.
* * * * *