U.S. patent application number 09/472259 was filed with the patent office on 2002-03-28 for throat configuration for axisymmetric nozzle.
Invention is credited to JOHNSON, JAMES STEVEN.
Application Number | 20020036241 09/472259 |
Document ID | / |
Family ID | 23874772 |
Filed Date | 2002-03-28 |
United States Patent
Application |
20020036241 |
Kind Code |
A1 |
JOHNSON, JAMES STEVEN |
March 28, 2002 |
THROAT CONFIGURATION FOR AXISYMMETRIC NOZZLE
Abstract
The radius of the hinged portion of the convergent/divergent
axisymmetrical exhaust nozzle of a gas turbine engine is configured
at the surface seeing the flow to be contoured at a critical radius
so to enhance the flow characteristics of the nozzle and improve
the low observables. The liner normally associated with the
convergent flap is cut back at the juncture adjacent the hinged
point connecting the divergent flap to be below the radar sight at
the tail of the engine.
Inventors: |
JOHNSON, JAMES STEVEN;
(SHELTON, CT) |
Correspondence
Address: |
NORMAN FRIEDLAND
11300 US HIGHWAY ONE
SUITE 400
NORTH PALM BEACH
FL
33408
|
Family ID: |
23874772 |
Appl. No.: |
09/472259 |
Filed: |
December 29, 1999 |
Current U.S.
Class: |
239/265.33 |
Current CPC
Class: |
F02K 1/1223 20130101;
F02K 1/822 20130101; Y02T 50/675 20130101; B64D 33/04 20130101;
Y02T 50/60 20130101 |
Class at
Publication: |
239/265.33 |
International
Class: |
F02K 001/00 |
Claims
It is claimed:
1. A convergent/divergent nozzle of an axisymmetrical exhaust
nozzle for a gas turbine engine including a hinged pivot at the
juncture of where the convergent/divergent portion of said nozzle
meet, said convergent nozzle comprising circumferentially spaced
axially extending flaps and said divergent nozzle having
circumferentially spaced axially extending flaps, a radius throat
at the juncture of the hinged pivot, said radius throat being
defined by a curvature formed on the flaps of the divergent nozzle
and falling in the range of from 2 inch radius to 10 inch
radius.
2. A convergent/divergent nozzle of an axisymmetrical exhaust
nozzle for a gas turbine engine as claimed in claim 1 wherein said
radius is substantially equal to 7.0 inches.
3. A convergent/divergent nozzle of an axisymmetrical exhaust
nozzle for a gas turbine engine including a hinged pivot at the
juncture of convergent portion and the divergent portion of said
nozzle, said convergent nozzle comprising circumferentially spaced
axially extending flaps and said divergent nozzle having
circumferentially spaced axially extending flaps, a radius throat
at the juncture of the hinged pivot, a liner attached to the
surface of said convergent flaps exposed to the engine's working
fluid for dissipating heat away from said convergent flaps, said
liner extending along the length of said convergent flaps and
terminating short of said hinged pivot and falling below the high
point of said curvature and being out of the line of sight from the
tail of the gas turbine engine.
4. A convergent/divergent nozzle of an axisymmetrical exhaust
nozzle for a gas turbine engine as claimed in claim 3 wherein the
radius of said radius radius throat being defined by a curvature
formed on the flaps of the divergent nozzle and falling in the
range of from 2 inch radius to 10 inch radius.
5. A convergent/divergent nozzle of an axisymmetrical exhaust
nozzle for a gas turbine engine as claimed in claim 4 wherein said
radius is substantially equal to 7.0 inches.
Description
TECHNICAL FIELD
[0001] This invention relates to the exhaust nozzle of a gas
turbine engine for powering aircraft and particularly to the
configuration of the throat of a convergent/divergent nozzle of the
exhaust of the gas turbine engine.
BACKGROUND OF THE INVENTION
[0002] As one skilled in this art will appreciate, the
axisymmetrical nozzle of a gas turbine engine serves to adjust the
throat of the nozzle be adjusted for different engine operating
modes so as to give a different flow characteristics in the throat
area. One of the problems with the heretofore known throat is that
the interface between the convergent flap portion and divergent
flap portion, particularly where the two portions are hinged, not
only impairs the flow there over or fails to provide a streamlined
flow stream adjacent the boundary layer, it presents itself in the
sight of radar and hence, is radar reflective. Where it is
desirable to minimize the radar reflectiveity of aircraft,
particularly, military aircraft, this portion of the axisymmetrical
exhaust nozzle presents is one of the more significant
problems.
[0003] I have found that I can provide an improved streamlined flow
over the hinged area of the convergent/divergent nozzle of a gas
turbine engine designed for military aircraft by changing the hinge
configuration. This change in configuration also improves the low
observable characteristics of the nozzle. The invention is
characterized as being capable of providing these improvements
noted in the above, and is characterized as being simple in
construction, inexpensive and capable of being used to retrofit
existing axisymmetrical nozzles.
SUMMARY OF THE INVENTION
[0004] An object of this invention is to provide an improved
convergent/divergent nozzle assembly for an axisymmetrical
discharge nozzle for a gas turbine engine powering aircraft.
[0005] A feature of this invention is to provide a configuration of
the flaps adjacent the hinge connection of the convergent and
divergent portions of the discharge nozzle that enhance the flow
characteristics adjacent thereto and the low radar
observables..
[0006] The foregoing and other features of the present invention
will become more apparent from the following description and
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a fragmentary view in elevation illustrating the
convergent and divergent flap of a axisymmetrical nozzle utilizing
this invention;
[0008] FIG. 2 is an enlarged view illustrating the throat
configuration of this invention; and
[0009] FIG. 3 is a partial view in perspective illustrating this
invention in the axisymmetrical exhaust nozzle of a gas turbine
engine.
[0010] These figures merely serve to further clarify and illustrate
the present invention and are not intended to limit the scope
thereof
DETAILED DESCRIPTION OF THE INVENTION
[0011] This invention is an improvement over the exhaust nozzle
described and claimed in U.S. Pat. No. 4,440,347 granted to Madden
et al on Apr. 3, 1984 and commonly assigned to the assignee of this
patent application and whose subject matter is incorporated herein
by reference.
[0012] This invention can best be understood by referring to FIGS.
1-3 which shows the portion of the convergent/divergent nozzle
generally illustrated as reference numeral 10 as having a plurality
of circumferentially spaced axially extending convergent flaps 12
and a similar number of circumferentially spaced axially extending
divergent flaps 14 that are hingedly connected at the throat 16 by
the hinge connection 18. These flaps 14 and 18 are articulated in a
well known manner in order to change the throat area of he throat
16.
[0013] The convergent/divergent flaps are suitably mounted in the
transition duct 20 which interconnects with the afterburner (not
shown) which in turn interconnects with the main engine. As is
typical in the axisymmetrical exhaust nozzle the transition duct
and convergent flap incorporate liner 22 to transport the heat away
from the main components of the nozzle. The convergent flap
likewise is provided with a suitable liner 24. Also, typical in
this construction is the use of cooling air as depicted by the
arrows A and B taken from the compressor (not shown) which flows
over the the components intended to be cooled and discharged from
an ejector 25 . Articulation of the convergent/divergent flaps to
change the throat area is suitably effectuated by the bellcrank
lever 22 which pivots flaps 12 and 14 about the hinged pivot 23 to
adjust the throat 25 at the radius throat 26. The external flaps 28
consisting of a plurality of circumferentially spaced axial flap
member is attached to the mode strut and bracket assembly 30 and
articulate with the movement of the convergent/divergent flaps. A
unison ring 32, similar to the unison ring depicted in U.S. Pat.
No. 4,440,347 is similarly used to move all of the individual flap
elements synchronously. A balancing flap 36, that is also a
plurality of circumferentially spaced axial flap elements serves to
minimize the load on the actuation members. The dogbone link 38
attached to the static structure 40 supports the
convergent/divergent assembly through the static structure 40 that,
in turn, is grounded to the transition duct.
[0014] Since the structural details of the axisymmetrical nozzle
are well known a detailed description thereof is omitted here from
for the sake of simplicity and for a more detailed description
reference should be made to U.S. Pat. No. 4,440,347, supra. Suffice
it to say that the convergent/divergent flaps serve to adjust the
throat area (defined by the radius C) of the exhaust nozzle to
provide the desired flow characteristics during certain operating
conditions within the engine's operation envelope. The invention
can best be seen in FIG. 2 where the liner 24 is cut back from the
pivot hinge 23 and the surface 40 adjacent the hinge 23 defines a
smooth transition portion of the divergent flap and creates a
smooth transition relative to the convergent flap (radius throat
26). In accordance with this invention the range of radii of
surface 40 or radius throat 26, at this location is between 2
inches (") to 10" and preferably being at 7". This configuration of
the radius throat 26 is critical and is applied to all the visible
surfaces of the nozzle throat including, as required, the flaps and
the seals adjacent to the flaps which serve to prevent the hot
gases of the engine to escape and bypass the exhaust nozzle. By
adhering to the critical radius as described above the throat 25
when articulated remains on a station line (a vertical plane
passing through each location of the engine and nozzle) of the
nozzle so that it does not alter the basic kinematics of the nozzle
while providing a smooth transition for the radar energy and at the
same time enhancing the aerodynamic performance of the nozzle.
[0015] What has been shown by this invention is a radius throat
adapted for use on a well known axisymmetrical nozzle throat which
serves to reduce the radial reflextivity characteristics of the
nozzle while collaterally improving the aerodynamic performance of
the nozzle. This invention has been tested and found to reduce the
radar reflectivity from the typical axial station line throat
design approach by three (3) to four (4) orders of magnitude.
[0016] Although this invention has been shown and described with
respect to detailed embodiments thereof, it will be appreciated and
understood by those skilled in the art that various changes in form
and detail thereof may be made without departing from the spirit
and scope of the claimed invention.
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