A variable cycle jet engine is provided with a mixing duct assembly which mixes core engine exhaust gas with bypass air when the engine is operating in a turbofan mode and which blocks flow from the core engine and isolates the core engine from the bypass flow when the engine is operating as a ramjet

Dunbar, Lawrence W.

Orlando, Robert J.

NASA Technical Reports Server

I11111 111111111111111111111111111111111111 1111 11111 11111 1111l111111111111 
USOO538 1655A 
United States Patent 1193 [11] Patent Number: 5,381,655 
Orlando et al. [45] Date of Patent: Jan. 17, 1995 
[54] ADMISSION MIXING DUCT ASSEMBLY 
[75] Inventors: Robert J. Orlando, West Chester; 
Lawrence W. Dunbar, Loveland, 
both of Ohio 
Cincinnati, Ohio 
[73] Assignee: General Electric Company, 
[21] Appl. NO.: 58,181 
[22] Filed: May 10,1993 
[51] Int. ( 3 . 6  ................................................ F02K 3/02 
[52] U.S. Cl. ...................................... 60/226.3; 60/262 
[58] Field of Search ................. 60/262, 261, 244, 263, 
60/226.1, 226.3 
[561 References Cited 
U.S. PATENT DOCUMENTS 
2,934,895 5/1960 Gregory et al. ...................... 60/244 
3,153,904 10/1964 Ellis et al. . 
3,192,712 7/1965 Nash et al. . 
3,296,800 VI967 Keenan et al. . 
3,314,437 4/1967 Pike . 
3,324,660 6/1967 Lane et ai. . 
3,477,230 11/1969 Bauger et al. . 
3,508,403 4/1970 Neitzel .................................. 60/262 
3,514,955 6/1970 Paulson et al. ....................... 60/262 
3,635,029 VI972 Menioux . 
3,879,941 4/1975 Sargisson . 
4,039,146 8/1977 Wagenknecht . 
4,043,121 SA977 Thomas et al. . 
4,054,030 10/1977 Pedersen . 
4,064,692 12/1977 Johnson et al. . 
4,068,471 7/1978 Simmons . 
4,069,661 7/1978 Rundell et al. . 
4,080,785 3/1978 Koff et al. . 
4,222,235 9/1980 Adamson et al. . 
4,817,378 4/1989 Giffi, I11 et al. .................... 60/261 
5,117,628 6/1992 Koshoffer ............................. 60/261 
Primary Examiner-Richard A. Bertsch 
Assistant Examiner-Timothy S. Thorpe 
Attorney, Agent, or Firm-Jerome C. Squillaro; Bernard 
E. Shay 
[571 ABSTRACT 
A variable cycle jet engine is provided with a mixing 
duct assembly which mixes core engine exhaust gas 
with bypass air when the engine is operating in a turbo- 
fan mode and which blocks flow from the core engine 
and isolates the core engine from the bypass flow when 
the engine is operating as a ramjet. 
9 Claims, 4 Drawing Sheets 
https://ntrs.nasa.gov/search.jsp?R=20080004795 2019-08-30T02:37:36+00:00Z
U.S. Patent Jan. 17, 1995 Sheet 1 of 4 5,38 1,655 
M 
m\ 
US. Patent Jan. 17, 1995 Sheet 2 of 4 5,381,655 
24 
FIG. 3 
6 2 7  60, 
34L 
f 
FIG. 4 
U,S, Patent Jan. 17, 1995 
FIG. 5 
Sheet 3 of 4 5,381,655 
FIG. 6 
US, Patent Jan. 17, 1995 Sheet 4 of 4 5,381,655 
16 
FIG. 7 
5,381,655 
1 2 
fashion allows the assembly to use essentially all the 
available annular area for the separate flows and there- 
fore results in a more compact, less expensive and ligh- 
ter AMDA. 
The aforementioned objects, features and advantages 
of the invention Will, in part, be pointed Out with partic- 
ularity, and will, in part, become obvious from the fol- 
lowing more detailed description of the invention, taken 
in conjunction with the accompanying drawings, which 
BRIEF DESCRIPTION OF THE DRAWINGS 1. Field of the Invention 
The present invention relates in general to jet engines In the drawings: 
capable of operating either as a turbofan or as a ramjet FIG. 1 is a partial schematic view, in axial section, of 
and relates in particular to an assembly which mixes l5 an admission mixing duct constructed in accordance 
core engine exhaust flow with bypass air flow during 
turbofan operation and which isolates the engine turbo- FIG. 2 is a partial schematic view in radial section 
machinery from bypass air flow during ramjet opera- 
tion. FIG. 3 is a partial aft view looking forward along a 
2. Description of Prior Developments 2o similar radial section as taken in FIG. 2, showing an 
In order to efficiently operate aircraft jet engines at alternate design for reducing flow around the movable 
both lower and higher Mach numbers, aircraft engine doors; 
designers have combined gas turbine engine features FIG. 4 is a schematic top plan view of an alternate 
with ramjet engine features as shown, for example, in embodiment of the invention wherein turbine outlet U.S. Pat. Nos. 3,153,904, 3,324,660 and 3,6359029. cur- 25 guide vanes are formed integrally with admission duct 
rent studies for advanced air breathing engines indicate flow guides; 
the need for jet engines capable offlight in the Mach 4 FIG. 5 is a schematic partial perspective view detail- 
to 6 range. At Mach numbers less than about 3, such ing the general features of FIG. 4; 
engines typically operate in a turbofan mode while, at FIG. 6 is a schematic view in axial section of 
ADMISSION MIXING DUCT ASSEMBLY 
RIGHTS O F  THE GOVERNMENT 
fomance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, public Law 85-568 
(72 Stat. 435; 42 USC 2457). 
BACKGROUND OF THE INVENTION 
fie invention herein described was made in the per- 5 
10 form an integral part thereof. 
with the invention; 
taken along line 1-1 of FIG. 1; 
higher Mach numbers, they generally operate as a ram- 30 an alternate embodiment of the invention wherein an 
1 _L 
augmenter is constructed integrally with the flow A flow control assembly is required that will easily guides; and allow the engine to transition between turbofan opera- FIG. 7 is an aft view looking forward along section tion and ramjet operation. Such an assembly should line 7-7 of FIG. 6. provide for thorough mixing of bypass air and core 35 
engine gases during turbofan or engine In the various figures of the drawing, like reference 
operation in order to ensure efficient combustion in the 
augmenter or afterburner. The assembly should also 
block inlet airflow through the core engine during ram- 
jet operation so that virtually all inlet air is available for 40 
ramjet combustion. 
JCL. 
designate like parts. 
DETAILED DESCRIPTION OF THE 
PREFERRED EMBODIMENTS 
The present invention will now be described in con- 
junction with the drawings beginning with FIGS. 1 and 
2 which depict a portion of a high speed jet engine 10 of 
The present invention has been developed to fulfil the type capable Of Operating in either a turbofan mode 
the needs noted above and therefore has as an object the 45 or in a ramjet mode. Insofar as the general operation of 
provision of a multi-purpose assembly located down- such an engine is well known, O d Y  that Portion of the 
stream from the rear turbine frame for k i n g  bypass engine which mixes engine bypass air with core engine 
with core engine exhaust gas during turbofan operation exhaust gases is &Own- 
and for isolating the core engine from bypass air and Engine 10 includes an annular outer Casing O r  nacelle 
inlet air through-flow during ramjet operation. Such 50 12 which defines the radially outer boundary of the aft 
selective flow isolation also protects the turbomachin- portion of an annular air bypass duct 14- Bypass duct 14 
ery from the ramjet combustion chamber during ramjet routes air around a core engine for providing greater 
operation. engine control during the turbofan mode of operation 
Briefly, the invention is directed to a compact admis- and for providing combustion air to an aft augmenter or 
sion mixing duct assembly (“AMDA”) which acts as 55 afterburner. The radially inner boundary of bypass duct 
both a mixer during turbofan operation and as an isola- 14 is defied by an annular inner casing 16. 
tor during ramjet operation and allows jet engine opera- An aftmost row of turbine blades comprising a row of 
tion in either a turbofan mode or a ramjet mode. low pressure turbine blades 18 is mounted downstream 
The AMDA includes movable doors separated by of a core engine and its associated turbomachinery. The 
flow guides with alternate doors connected via cams 60 turbine blades 18 are located radially inwardly of inner 
and linkages. A significant feature of the AMDA is the casing 16 in an annular core engine exhaust gas duct 19 
combination of alternating door control in conjunction in a conventional fashion for rotation about engine cen- 
with the flow guides. This arrangement allows the tralaxis20. 
AMDA to act as a mixer during turbofan operation An array of turbine outlet guide vanes 22 is mounted 
when alternate doors are open and closed. 65 between an engine centerbody 24 and the inner casing 
The capability to close all the doors so as to block 16. Hot exhaust gases which drive the low pressure 
flow from the core engine allows the AMDA to func- turbine 18 are de-swirled by the turbine outlet guide 
tion as a core engine isolator. Moving the doors in this vanes 22. These exhaust gases then flow axially through 
SUMMARY OF THE INVENTION 
5,381,655 
3 4 
exhaust gas duct 19 across space 26 and enter an admis- half of the movable doors are driven open and half are 
sion mixing duct assembly (AMDA) 28. driven closed when the engine 10 is operating in the 
The AMDA 28 includes a plurality of circumferen- mixing or turbofan mode. During ramjet operation, all 
tially-spaced flow guides 30 which extend radially in of the movable doors are closed to isolate the turboma- 
the manner of a spoked array. The flow guides extend 5 chinery from the flow from bypass duct 14 and to sub- 
axially along centerbody 24 from a point aft of the tur- stantially block the flow of air through the exhaust duct 
bine outlet guide vanes 22 to a point near the aft end of 19. 
the centerbody. An annular augmenter or afterburner The separation of the bypass air 34 and exhaust gas 36 
32 of known design is mounted within the engine at a by the flow guides 30 and movable doors 42 allows for 
position aft of the flow guides 30. Conventional flame 10 the formation of circumferentially alternating channels 
holders 33 are provided around the augmenter. for directing the respective flows through an axially and 
Flow guides 30 may take the shape of planar panels radially-extending series of tortuous mixing paths for 
which extend radially between the centerbody 24 and enhancing the mixing of these flows. Further mixing 
the outer casing 12. As seen in FIG. 1, the flow guides may be produced by forming the flow guides 30 as 
receive both bypass air 34 from bypass duct 14 and core 15 hollow panels through which bypass air may travel. 
engine exhaust gas 36 issuing from the core engine ex- Inlet ports 54 may be formed along the leading edge 
haust gas duct 19 across space 26. In this manner, the 56 of each flow guide 30 for admitting bypass air into 
flow guides circumferentially divide each of the respec- and through the panels. Exhaust ports 58 may be 
tive gas flows 34,36 into a plurality of separate CirCUm- formed along the trailing edge 60 of each flow guide as 
ferentially-spaced flow paths while providing signifi- 20 well as along the side surfaces 62 of the flow guides for 
cant structural support between the outer casing 12 and exhausting, mixing and distributing the bypass air into 
centerbody 24. the exhaust gas. 
As seen in FIG. 2, the bypass air 34 is Split by flow When the movable doors 42 are positioned in their 
guides 30 into a circumferentially-extending Series Of open or up position 50, a circumferentially extending 
radially outer bypass air *g ducts 38. The core 25 wedge-shaped gap 64 is left between each flow guide 30 
engine exhaust gas is likewise split into a CirCumferen- and the adjacent edge 66 of each movable door. Gaps 64 
tially-extending series of radially inner exhaust gas mix- could be reduced by increasing the circumferential 
ing ducts 40. Ducts 38 and 40, which in combination width of each flow guide 30 along its trailing edge as 
form the above-noted flowpaths between flow guides shown in phantom at 68 in FIG. 2. 
30, are further defined at least in part by a plurality Of 30 An additional set of flaps could also be employed to 
movable flaps or generally sector-shaped doors 42 reduce gaps 64 or, as shown in FIG. 3, a pair of spring- 
mounted between each pair of adjacent flow guides 30. loaded flow guide followers 69 may be mounted within 
The movable doors 42 may be pivotally mounted each door 42. Spring members 71 circumferentially bias 
adjacent the aft end of inner casing 16 via hinged pin each flow guide follower into sliding contact with the 
joints 44. As illustrated with respect to the central one 35 confronting side surfaces of each door. However, it 
of doors 42 shown in Fig. 2, each of doors 42 is may not be necessary to reduce the size of gaps 64 since 
pivotally mounted to a pair of circumferentially adja- the purpose of the AMDA is to mix the bypass air 34 
cent flow guides 30 via a pair of hinged pin joints 44 with the exhaust gas 36 and the gaps 64 tend to enhance 
such that each door 42 is pivotable about chord line 55 this mixing. 
which connects the adjacent pair of flow guides 30. 40 The extent of movement of the movable doors 42 
Any suitable actuator may be used for controlling the may vary depending on the particular engine applica- 
position of doors 42 such as hydraulic piston actuators tion. Moreover, for a particular engine cycle, it is possi- 
or electric drive motors. As seen in FIG. 1, each door ble to fm half of the movable doors in their closed posi- 
42 may be controllably and selectively driven over arc tions 52 during all flight conditions. This would signifi- 
46 by an actuation handle or lever 41 mounted within 45 cantly simplify the design of the AMDA, but not affect 
each door so as to vary the cross-sectional areas of its mixing and isolation functions. 
ducts 38 and 40. Links 43 interconnect alternate doors As indicated above, a space 26 has been left between 
42 via ball joints 45 to an outer actuation ring 47 and an the trailing edges 70 of the turbine outlet guide vane 22 
inner actuation ring 49. and the leading edges 56 of the flow guides 30. This 
As can be appreciated, the AMDA is capable of mix- 50 space is required to allow the core flow exhaust gas 36 
ing a variable amount of bypass air 34 with a variable to migrate circumferentially to every other duct 40 
amount of core engine exhaust gas 36 as these flows, while minimizing the static pressure circumferential 
which were previously isolated by the inner casing 16, variation at the exit of the low pressure turbine blades 
are free to mix and commingle as they travel axially 18. 
between the flow guides 30. Moreover, by closing all of 55 As an alternative, it is possible to construct the tur- 
the movable doors 42 radially inwardly to the position bine outlet guide vanes 22 as an integral part of the flow 
shown in solid lines in FIG. 1, the movable doors 42 guides 30. As seen in FIGS. 4 and 5, the flow of exhaust 
isolate and protect the core engine and turbomachinery gas 36 is turned and diffused between the airfoil shaped 
during ramjet operation. The turbine outlet guide vanes front portion of these contoured flow guides which 
22 and low pressure turbine blades 18 are protected 60 serve as outlet guide vanes 22. The aft portion of these 
from the heat generated in ramjet combustion chamber flow guides opens up internally to provide internal 
48 as the movable doors 42 in their closed position block space 72 for the rear bypass duct flow, i.e. bypass air 34. 
flow from the core engine and thereby causing virtually Thus, the core flow 36 is squeezed circumferentially 
all inlet flow to travel through bypass duct 14. between sidewalls 62 while diffusing radially to make 
During turbofan operation, movable doors 42 may be 65 room for the bypass air flow 34. This is done in such a 
selectively positioned in their open position 50 and in manner so as to minimize the static pressure circumfer- 
their closed position 52 in an alternating fashion as ential variation just behind the low pressure turbine 
shown in FIG. 2. Alternate doors 42 may be simulta- blades 18. It is also possible to incorporate the aug- 
neously opened and closed by one or more annular menter 32 as part of the trailing edges 60 of the flow 
actuation cams or actuation rings 47,49 such as noted guides 30. As seen in FIGS. 6 and 7, the augmenter is 
above which operate alternate doors. In this manner, connected to the trailing edges 60 by brackets 100. 
5,381,655 
5 
These modifications allow for a more compact engine 
design. 
There has been disclosed heretofore the best embodi- 
ment of the invention presently contemplated. How- 
ever, it is to be understood that various changes and 5 
modifications may be made thereto without departing 
from the spirit of invention. 
within a jet engine, comprising: 
What is claimed is: 
1. An apparatus for mixing bypass air and exhaust gas 
annular bypass duct means for channeling bypass air 
through said engine; 
annular exhaust gas duct means located radially in- 
wardly of said annular bypass duct means for chan- 
neling core engine exhaust gas through said engine; 
a plurality of circumferentially spaced flow guides for 
receiving said bypass air from said bypass duct and 
for receiving said exhaust gas from said exhaust gas 
duct; and 
a plurality of movable doors mounted between and 
cooperating with said flow guides so as to define a 
circumferentially extending series of radially outer 
bypass air mixing ducts and a circumferentially 
extending series of radially inner exhaust gas mix- 25 
ing ducts; 
wherein said plurality of movable doors comprises a 
plurality of generally sector-shaped doors which 
each pivot about a chord line connecting an adja- 
cent pair of said flow guides, said doors being 30 
pivotable into said bypass air mixing ducts and into 
said exhaust gas w n g  ducts so as to control the 
respective flows of said bypass air and said exhaust 
gas therethrough. 
10 
15 
20 
35 
6 
2. The apparatus of claim 1, wherein said movable 
doors comprise means for substantially blocking flow of 
said exhaust gas through said exhaust gas ducts. 
3. The apparatus of claim 1, further comprising a 
centerbody and wherein said movable doors cooperate 
with said flow guides and said centerbody to substan- 
tially block said flow of exhaust gas through said appa- 
ratus. 
4. The apparatus of claim 1, further comprising an 
aftmost row of turbine blades located within said ex- 
haust gas duct means at a position upstream of said 
movable doors and an augmenter located downstream 
of said movable doors. 
5. The apparatus of claim 4, further comprising tur- 
bine outlet guide means disposed within said exhaust gas 
duct means downstream of said aftmost row of turbine 
blades and wherein said flow guides are located down- 
stream from said turbine outlet guide means. 
6. The apparatus of claim 1, wherein said flow guides 
comprise outlet guide means integrally connected 
thereto for de-swirling said exhaust gas. 
7. The apparatus of claim 1, wherein said flow guides 
comprise hollow panels having inlet ports and outlet 
ports formed therein for respectively admitting said 
bypass air into said flow guides and mixing said bypass 
air with said exhaust gas. 
8. The apparatus of claim 1, further comprising an 
augmenter integrally connected to an aft end portion of 
said flow guides. 
9. The apparatus of claim 1, further comprising at 
least one fued door located between said flow guides so 
as to permanently block a portion of said exhaust gas 
from flowing through said apparatus. * * * * *  
40 
45 
50 
55 
60 
65 


Admission mixing duct assembly

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server