A gas turbine engine has an inlet duct formed to have a shape with a first ellipse in one half and a second ellipse in a second half. The second half has an upstream most end which is smaller than the first ellipse. The inlet duct has a surface defining the second ellipse which curves away from the first ellipse, such that the second ellipse is larger at an intermediate location. The second ellipse is even larger at a downstream end of the inlet duct leading into a fan

Florea, Razvan Virgil

Matalanis, Claude G.

Stucky, Mark B.

NASA Technical Reports Server

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(12) United States Patent 
Florea et al. 
(54) GAS TURBINE ENGINE INLET WALL 
DESIGN 
(71) 	 Applicant: UNITED TECHNOLOGIES 
CORPORATION, Hartford, CT (US) 
(72) 	 Inventors: Razvan Virgil Florea, Mancheser, CT 
(US); Claude G. Matalanis, 
Longmeadow, MA (US); Mark B. 
Stucky, Glastonbury, CT (US) 
(73) 	 Assignee: United Technologies Corporation, 
Hartford, CT (US) 
(*) 	 Notice: Subject to any disclaimer, the term of this 
patent is extended or adjusted under 35 
U.S.C. 154(b) by 52 days. 
(21) Appl. No.: 14/185,045 
(22) Filed: Feb. 20, 2014 
(65) Prior Publication Data 
US 2015/0122952 Al 	 May 7, 2015 
Related U.S. Application Data 
(60) Provisional application No. 61/770,506, filed on Feb. 
28, 2013. 
(51) Int. Cl. 
B64D 33102 	 (2006.01) 
F02C 7104 	 (2006.01) 
B64D 27120 	 (2006.01) 
(52) U.S. Cl. 
CPC . F02C 7104 (2013.01); B64D 27120 (2013.01); 
B64D 33102 (2013.01); B64D 203310286 
(2013.01); F05D 2220136 (2013.01); F05D 
2250114 (2013.01); YIOT 13710536 (2015.04) 
(lo) Patent No.: 	 US 9,291,101 B2 
(45) Date of Patent : 	 Mar. 22, 2016 
(58) Field of Classification Search 
CPC .... B64D 33/02; B64D 29/06; B64D 2241/00; 
YIOT 137/0536 
USPC ................... 244/53 B, 54; 137/15.1; 181/214 
See application file for complete search history. 
(56) 	 References Cited 
U.S. PATENT DOCUMENTS 
	
3,583,661 A * 	 6/1971 Stake .......................... 244/53 B 
	
4,787,421 A * 	 11/1988 Yu ................................. 138/178 
	
5,105,615 A * 	 4/1992 Herzog ........................... 60/803 
	
5,150,571 A * 	 9/1992 Herzog ........................ 60/200.1 
	
5,915,403 A * 	 6/1999 McConachie et al........ 137/15.1 
7,631,836 132 * 12/2009 Lebas ......................... 244/53 B 
	
7,784,732 132 * 	 8/2010 Owens et al . ............... 244/53 B 
	
8,096,131 132 	 1/2012 Ziaei 
	
8,262,780 132 	 9/2012 Smithies et al. 
2005/0258307 Al* 11/2005 Lebas ......................... 244/53 B 
2008/0164378 Al* 	 7/2008 Owens et al . ............... 244/53 B 
(Continued) 
FOREIGN PATENT DOCUMENTS 
EP 	 1243782 132 * 7/2013 
FR 	 2680830 Al * 3/1993 
WO 	 W02008017567 Al * 2/2008 ............. B64D 33/02 
Primary Examiner Benjamin P Lee 
(74) Attorney, Agent, or Firm Carlson, Gaskey & Olds, 
PC 
(57) ABSTRACT 
A gas turbine engine has an inlet duct formed to have a shape 
with a first ellipse in one half and a second ellipse in a second 
half. The second half has an upstream most end which is 
smaller than the first ellipse. The inlet duct has a surface 
defining the second ellipse which curves away from the first 
ellipse, such that the second ellipse is larger at an intermediate 
location. The second ellipse is even larger at a downstream 
end of the inlet duct leading into a fan. 
10 Claims, 2 Drawing Sheets 
20
";k 140 144 
142 
https://ntrs.nasa.gov/search.jsp?R=20160004236 2019-08-31T03:35:31+00:00Z
US 9,291,101 B2 
Page 2 
(56) 	 References Cited 	 2012/0138736 At * 	 6/2012 Cazals et al ..................... 244/54 
2015/0030445 At * 	 1/2015 Gonidec et at ................ 415/220 
U.S. PATENT DOCUMENTS 	 2015/0030446 At * 1/2015 Gonidec et at ................ 415/220 
2010/0108802 At * 	 5/2010 Marche et al . .................. 244/54 
2011/0108676  At * 5/2011 Colaprisco et al. ......... 244/53 B 	 * cited by examiner 
20~ 
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'vv 	 FIG.2 
ENGINE AXIS 
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AIP 
`32 
RUB 
~40 2% 
-40 
34 
FIG.3A 
U.S. Patent 	 Mar. 22 , 2016 	 Sheet 1 of 2 	 US 9 ,291,101 B2 
U.S. Patent 	 Mar. 22, 2016 	 Sheet 2 of 2 	 US 9,291,101 B2 
FIG.3C 
140 	 144 
I 
I 
I 
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------- 1 ----- 
142 FIGAA 
L 
344 340 
	
244 	 I 	
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242 	
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F1GAC 
FIG.4A 	 FIG.4B FIG.4C 
210 
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ENGINE_ AXIS 
FIG.6  
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off 
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212 
US 9,291,101 B2 
GAS TURBINE ENGINE INLET WALL 
DESIGN 
CROSS-REFERENCE TO RELATED 
APPLICATION 
This application claims priority to U.S. Provisional Appli-
cation No. 61/770,506, filed Feb. 28, 2013. 
STATEMENT REGARDING FEDERALLY 
SPONSORED RESEARCH OR DEVELOPMENT 
This invention was made with government support under 
Contract No. NNCO7CB59C, awarded by NASA. The Gov-
ernment has certain rights in this invention. 
BACKGROUND 
This application relates to an inlet wall design for use in an 
embedded gas turbine engine. 
Gas turbine engines are known and typically include a fan 
delivering air into a bypass duct and into a core engine. In the 
core engine the air is compressed at a compressor and then 
mixed with fuel and ignited in a combustion section. Products 
of the combustion pass downstream over turbine rotors, driv-
ing them to rotate. 
Gas turbine engines have historically been mounted on a 
tail or beneath the wings of an aircraft. However, a next 
generation of aircraft seeks to dramatically increase fuel effi-
ciency, reduce emissions, and decrease fuel burn. A design for 
such aircraft utilizes a blended wing design wherein the body 
and wing merge smoothly into each other. Such designs have 
typically been proposed with embedded engines, which are 
mounted within a fuselage or body of the aircraft. 
In such an engine, the area upstream of an inlet to the 
engine is different on circumferential locations adjacent to the 
body than at locations spaced away from the body. A bound-
ary layer or area of low momentum air will be formed leading 
into the inlet and the fan at circumferential locations associ-
ated with the body. 
SUMMARY 
2 
In another featured embodiment, a blended wing aircraft 
has a blended wing fuselage and at least one embedded gas 
turbine engine in the fuselage. The gas turbine engine has an 
inlet duct formed to have a first ellipse in one half and a 
5 second ellipse in a second half. The second half has an 
upstream most end which is smaller than the first ellipse. The 
inlet duct has a surface defining the second ellipse which 
curves away from the first ellipse, such that the second ellipse 
is larger at an intermediate location. The second ellipse is 
10 
even larger at a downstream end of the inlet duct leading into 
a fan. 
In another embodiment according to any of the previous 
embodiments, a center of the inlet duct cross-section is 
15 defined between the first and second ellipses and, a distance 
between the center and the surface defining the second ellipse 
increasing as one moves further into the inlet duct and toward 
the fan. 
In another embodiment according to any of the previous 
20 embodiments, a vertical semi-axis of the first ellipse is gen-
erally constant from the upstream end to the downstream end. 
In another embodiment according to any of the previous 
embodiments, the first ellipse is in a vertically upper half of 
the inlet duct. 
25 In another embodiment according to any of the previous 
embodiments, the first ellipse is in a vertically lower half of 
the inlet duct. 
These and other features may be best understood from the 
following drawings and specification. 
30 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 shows a blended wing aircraft. 
FIG. 2 shows an inlet duct for a gas turbine engine as may 
35 be included in the FIG. 1 embodiment. 
FIG. 3A shows a first geometric consideration for an inlet 
duct. 
FIG. 3B shows another dimension of the inlet duct. 
FIG. 3C shows a graph of one inlet duct design. 
40 	 FIG. 4A shows the inlet duct at an upstream most location. 
FIG. 4B shows the inlet duct at an intermediate location. 
FIG. 4C shows the inlet duct immediately upstream of a 
In a featured embodiment, a gas turbine engine has an inlet 
duct formed to have a shape with a first ellipse in one half and 45 
a second ellipse in a second half. The second half has an 
upstream most end which is smaller than the first ellipse. The 
inlet duct has a surface defining the second ellipse which 
curves away from the first ellipse, such that the second ellipse 
is larger at an intermediate location. The second ellipse is 50 
even larger at a downstream end of the inlet duct leading into 
a fan. 
In another embodiment according to the previous embodi-
ment, a center of the inlet duct cross-section is defined 
between the first and second ellipses and, a distance between 55 
the center and the surface defining the said second ellipse 
increasing as one moves further into the inlet duct and toward 
the fan. 
In another embodiment according to any of the previous 
embodiments, a vertical semi-axis of the first ellipse is gen- 60 
erally constant from the upstream end to the downstream end. 
In another embodiment according to any of the previous 
embodiments, the first ellipse is in a vertically upper half of 
the inlet duct. 
In another embodiment according to any of the previous 65 
embodiments, the first ellipse is in a vertically lower half of 
the inlet duct.  
fan. 
FIG. 5 schematically shows an engine. 
FIG. 6 shows a second inlet duct. 
DETAILED DESCRIPTION 
An aircraft 20 is illustrated in FIG.1 having a blended wing 
body or fuselage 22 and a plurality of embedded gas turbine 
engines 24. As known, the embedded gas turbine engines 24 
include a fan at an upstream location delivering air into a 
compressor and into a bypass duct. The air is mixed with fuel 
and ignited in a combustor downstream of the compressor and 
products of that combustion pass downstream over turbine 
rotors driving them to rotate. 
There are challenges with regard to the embedded gas 
turbine engines 24. As an example, as shown in FIG. 2, an 
upstream most end 100 of an embedded gas turbine engine 24 
will sit on the fuselage 22. There will be a boundary layer 
leading into a bottom surface 32 of an inlet duct for the engine 
24. As shown, in this design a shape of the bottom or lower 
surface 32 is closer to a horizontal shape and an upper or top 
surface 30 is closer to a cylindrical shape. 
Applicant has designed the shape of the inlet duct by uti-
lizing ellipses and optimizing the curves, lengths and shape of 
the overall duct. 
US 9,291,101 B2 
3 
As shown in FIG. 3A, the shape of inlet duct 40 may be a 
super ellipse, having a first ellipse 44 at an upper surface or 
spaced away from the fuselage 22 and a second ellipse 42 at 
a lower portion or spaced adjacent to the fuselage 22. A center 
line 34 is defined to separate ellipses 42 and 44. A formula for 
calculating the shape of the ellipses may be: 
[X/aj'+[Y/bp—1 
In this formula a and b are constants (known as ellipse 
semi-axes) corresponding to a half-width of the inlet and a 
height derived from the center line 34 and the upper/lower 
walls respectively. The constants p and q are exponents which 
shape the ellipses. The values of the constants for each quarter 
of a super ellipse are a function of the cross-sectional area, 
which varies linearly as a function of axial position. 
FIG. 3B shows the inlet duct 40 varying over an axial 
length. As shown, the centroid C or line 34 is spaced below a 
central axis of the engine X. As can be appreciated, the bottom 
surface 32 curves away from the upper surface 30. The ver-
tical ellipse semi-axis corresponding to upper surface 30 var-
ies linearly, with the axial position, while the vertical ellipse 
semi-axis corresponding to lower surface 32 can be seen to 
expand away from the center C as one moves into the inlet 
duct 40. 
FIG. 3C graphically shows the location of the center 34, the 
bottom surface 32, and the upper or top surface 30 as one 
moves further into the engine, or locations L. As can be 
appreciated, the vertical ellipse semi-axes corresponding to 
surfaces 30 and 32 generally vary linearly with the axial 
position. 
As shown in FIG. 4A, at the inlet end 140 of the inlet duct, 
the super ellipse has a very small area lower ellipse 142 and an 
upper ellipse 144, which is of a much larger area. This may be 
at the upstream most point on the inlet duct and immediately 
downstream of the fuselage 22. 
FIG. 4B shows another location 240 which is somewhat 
intermediate in the duct, and wherein the lower ellipse 242 
has a much larger area than it was in the FIG. 4A. The ellipse 
244 may be generally the same as ellipse 144. 
FIG. 4C shows a downstream location 340 wherein the 
ellipses 342 and 344 are generally equal in area. Immediately 
downstream of this location would be the fan, which is shown 
schematically in FIG. 5 at 200. A bypass duct B is shown. As 
known, a core engine including compressor 202, combustion 
section 204 and turbine 206 is downstream of the fan 200. In 
fact, as can be appreciated, the ellipses which form the inlet 
duct could be said to have a first set of ellipses as the lower 
ellipses 142/242/342, and a second set of ellipses as the upper 
ellipses 144/244/344. 
By designing the inlet duct 40 according to the teachings 
above, the airflow will be more uniform by the time it reaches 
the fan 200, and the effects of the boundary layer from the 
fuselage 22 will be dramatically reduced. 
FIG. 6 shows another duct embodiment 210. In duct 
embodiment 210, the lower or bottom surface 212 is formed 
such that it has a generally constant vertical semi-axis, while 
the upper or top surface 214 expands much like the lower 
surface 32 of the FIG. 3B embodiment. 
A worker of ordinary skill in this art would recognize when 
either of the inlet shape options would be most efficient to 
utilize. Of course, other shapes may be utilized as well. 
Although an embodiment of this invention has been dis-
closed, a worker of ordinary skill in this art would recognize 
that certain modifications would come within the scope of thi s 
4 
invention. For that reason, the following claims should be 
studied to determine the true scope and content of this inven-
tion. 
The invention claimed is: 
5 	 1. A gas turbine engine comprising: 
an inlet duct formed to have a shape with a first set of ellipse 
sections along one longitudinal half and a second set of 
ellipse sections along a second longitudinal half, with 
said second set of ellipse sections having an upstream 
most end which is smaller in area than an area of an 
10 
upstream most end of said first set of ellipse sections, 
and said inlet duct having a surface defining said second 
set of ellipse sections which curves away from said first 
set of ellipse sections, such that said second set of ellipse 
sections has a larger area at an intermediate location, and 
15 said second set of ellipse sections has an even larger area 
at a downstream end of said inlet duct leading into a fan. 
2. The gas turbine engine as set forth in claim 1, wherein a 
center of the inlet duct cross-section is defined between said 
first and second sets of ellipse sections and, a distance 
20 between said center and said surface defining said second set 
of ellipse sections increasing as one moves further into said 
inlet duct and toward said fan. 
3. The gas turbine engine as set forth in claim 2, wherein a 
vertical semi-axis of said first set of ellipse sections is gener-
25 ally constant from said upstream end to said downstream end. 
4. The gas turbine engine as set forth in claim 3, wherein 
said first set of ellipse sections is in a vertically upper half of 
said inlet duct. 
5. The gas turbine engine as set forth in claim 3, wherein 
30 said first set of ellipse sections is in a vertically lower half of 
said inlet duct. 
6. A blended wing aircraft comprising: 
a blended wing fuselage and at least one embedded gas 
turbine engine in said fuselage; and 
35 	 said gas turbine engine having an inlet duct formed to have 
a first set of ellipse sections along one longitudinal half 
and a second set of ellipse sections in a second longitu-
dinal half, with said second set of ellipse sections having 
an upstream most end which is smaller in area than an 
40 area of an upstream most end said first set of ellipse 
sections, and said inlet duct having a surface defining 
said second set of ellipse sections which curves away 
from said first set of ellipse sections, such that said 
second set of ellipse sections has a larger area at an 
45 intermediate location, and said second set of ellipse 
sections has an even larger area at a downstream end of 
said inlet duct leading into a fan. 
7. The blended wing aircraft as set forth in claim 6, wherein 
a center of the inlet duct cross-section is defined between said 
50 first and second sets of ellipse sections and, a distance 
between said center and said surface defining said second set 
of ellipse sections increasing as one moves further into said 
inlet duct and toward said fan. 
8. The blended wing aircraft as set forth in claim 7, wherein 
55 a vertical semi-axis of the first set of ellipse sections is gen-
erally constant from said upstream end to said downstream 
end. 
9. The blended wing aircraft as set forth in claim 8, wherein 
said first set of ellipse sections is in a vertically upper half of 
60 said inlet duct. 
10. The blended wing aircraft as set forth in claim 8, 
wherein said first set of ellipse sections is in a vertically lower 
half of said inlet duct. 


Gas Turbine Engine Inlet Wall Design

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