mark drela mit aero & astro
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Low-Order Modeling for Conceptual Aircraft Design
and Development of the D8 Transport Concept
Mark Drela
MIT Aero & Astro
Stanford AA295 Seminar
25 May 11
Motivation: NASA’s N+3 Program
N+3 Objective:
Identify concepts and technologies needed
for 70% (!) reduction in Fuel / PAX-mile
from current-technology baseline by 2025
Reasonably safe assumption:
Tweaking current designs will not get us there
Presentation Outline
• Transport Aircraft System OPTimization (TASOPT)
• D8.x “Double Bubble” transport aircraft concept
TASOPT Motivation
Find global optimum in Aircraft + Engine + Ops design space
fuel economy isocontours
existing engines
existing airplanes
common apparent (false) optimum
W/S , M . . .
true optimum
FPR, T
.
.
.
t 4
Pratt’s, GE’s design domain
Boeing’s, Airbus’s design domain
TASOPT Summary - I
Collection of coupled low-order physical models
• Primary structure
– surface beam bending, pressurization loads
• Aero
– viscous/inviscid methods, Trefftz Plane
• Engine
– fan+core 1D flowpath simulation, turbine cooling
• Balance, trim, stability
– surface CL’s at operation and CG limits, static margin
• Performance
– flight trajectory simulation (takeoff, climb, cruise, descent)
TASOPT Summary - II
TASOPT does not use
• Historical correlations for primary structure weights
• Wetted-area× form-factor methods for drag prediction
• Specified-thickness airfoils
• Assumed engine parameters and performance
• Assumed trim conditions
→ These cannot be trusted for “outside the box” designs
Weight Breakdown
fspoi
w.att
flapslat
v.add
h.add
spoiler
aileronl.e., t.e.
wing
fuel
shell
floor
reserve
burn
1
f
cone
1
paddf
1
fstring
frameff fadd
skin
1
reservef
strut
eaddf
1
1
fhadd
1
fvadd
pylon
1
fpylon
window
seat
apu
fff
hpesys
lgnose
lgmain
1
flapffslatff
fribs
lete
f ribs
aile
watt
payload
fuselage
h.tail
v.tail
h.p.e. sysnose l.g.main l.g.
eng.add
eng.bare
nacelleengine
v.capv.web
h.webh.cap
w.add
w.web
w.cap
v.bendh.bend
insulation
web
pay.add
a.p.u.
MTOW
PAYLOAD
STRUCTURE
PROPULSION
EQUIPMENT fixed
CONTROLS
Primary Structure — Fuselage
• pressure vessel with added bending and torsion loads
• bending loads from distributed payload, point tail
p∆
(x)
x
W
Wtail
h
+ Wpay padd+ W +shell
+ hLrMh
(x)v
Lr vMv
N
N ( W )+ W + floorWwindow insul + Wseat
added bending stringers
xwbox
WN fix
Tail Load Bending Moments
• Max tail loads at VNE impart fuselage bending moments
• Moments substantially modified by inertial reaction relief
Lh Lv
wing mass
pitch acceleration yaw acceleration
(x)h
static moment(clamped wing root)
static moment(clamped wing root)
(x)vapproximation
approximation
maxmax
wing mass + yaw inertia
inertial relief
actual moment
Primary Structure — Fuselage
• “double-bubble” pressure vessel
• skin also takes torsion loads from vertical tail
• added longeron area for bending loads
⇒ Pressurization, Loads fully size all structural elements
R fuse
dbw
Lv
v
tτtσ
tσ db
added bending material
tskin
Askin
skincone cone
skin
skin
stringers
fuse
max
A
floor
floor beams
Primary Structure — Wing or Tail Surface
• Multiple linear-taper planform, with or without strut
• Aero loading p(η) via local cℓ factors, center and tip rolloffs
• Weight loading w(η) from structure, fuel, engine
η = 2 y/b
10 o
structural box
ηs
(projected)
Λ
Engine weight alternativeto strut force
∆Lt
∆Lo p(η)
(η)w
NWNWinn out
η
structural cross section
Wing or Tail Surface Cross-Section
• Box beam: bending caps with shear webs
• Non-structural LE/TE fairings, slats, flaps, spoilers
• Box interior defines maximum fuel volume
• Spanwise-constant material stresses
⇒ Bending Moments, Shears, fully size wingbox elements
tcap
twebh
fuelA
wc
box
box
hboxhr
Load Cases used for Sizing Primary Structure
Wing: Net load at Nlift
Tails: Max aero load at never-exceed speed VNE
Tailcone: Max torsion from vertical tail load at VNE
Body skin: Pressurization + Max vertical-tail torsion at VNE
Longerons: Payload loading + Tail loads, at Nland, VNE
Secondary Structure and Equipment Weights
Wfix fixed pilots, cockpit, instrumentation weight
W ′window window weight/length
W ′′insul insulation weight/area
fpadd attendants, seats, galleys, IFE, etc. weight/payload
fgear landing gear weight/MTOW
fhpesys hydraulics, pneumatics, electrical weight/MTOW
fflap flaps, ailerons weight/wingbox-weight
Airfoil Parameterization
Optimum tcstrongly depends on rest of design variables, so . . .
• Family of airfoils over range of tc= 0.09 . . . 0.14
• Each is designed for good Mach drag rise behavior
• Drag polars are precomputed
Gives “rubber airfoil” database:
[cdf , cdp] = F(CL⊥, M⊥ ,
tc , Rec)
Parametric Airfoil Performance Model
Typical Cp(x), M(x, y)
Parametric Airfoil Performance Model
Offline-computed airfoil polars forM⊥ = 0.05 . . . 0.82, cℓ = 0.40 . . . 0.90
Parametric Airfoil Performance Model
Sweep theory with root corrections gives 3D wing profile drag
CDwing= F(CL , M∞ , Λ , t
c, Rec)
Λ V
V
Df
DpDp
shockpotential flow streamline
Cp lc
M fdc
dc p
oc
2ok c
shock
potential flow streamlines
( unswept−shock wing portion )Suns
Induced Drag Model
• Trefftz Plane analysis with wake contraction by fuselage
• Includes tail load from trim calculations
/2by
y’ /2b’y’
y
y’o
yo
Γ y’( )y’
z’
w
Γi−
wn
s’
ii
Fuselage Drag Model
• Potential flow via compressible source line+panel usingA(x)
• BL+wake flow via compressible integral BL method, withlateral divergence via body perimeter b0(x)
• XFOIL-type viscous/inviscid coupling and solution
• Used for fuselage drag and BL Ingestion calculations
CDfuse=
2Θwake
S
x
A(x)∆∗ ∗ΘΘ, , (x)
y
z ∗ ∗, , (x)δ θ θ
b (x)0
Θwake
(x)Λ
(x)λ
Fuselage Drag Model
Typical BL calculation
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 10 20 30 40 50 60
HkUe
Uinv
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0 10 20 30 40 50 60
Disstauw
Knowing BL state at engine location enables BLI accounting
Engine Performance Model
• Complete flowpath simulation for . . .
– . . . sizing at cruise design point,
– . . . operation at off-design takeoff, climb, descent, static.
– Includes effects of Boundary Layer Ingestion (BLI), if any
• Dispenses with engine-performance correlations
• Provides “rubber engine” for optimizer
.m
8
6
0
4
m.
.mα 3
5
7
4.52.5
αc
4.12
1.9
2.11.8
1.8
N NN G/
4.9
l hl
core
core
Turbine Film Cooling Sub-Model
Modified Horlock model, with two prediction modes:
αc = F(Tmetal , Tt 3 , Tt 4 ; StA , θf , ηc) (cooling flow sizing)
Tmetal = F( αc , Tt 3 , Tt 4 ; StA , θf , ηc) (Tmetal prediction)
combustor
T
T
pαc(1− ).m.αc m
.fm
IGV
u
mixingt 5
t 5
Tt 3p t 3
p
T
p
u
p4a
4aTt 4
p t 4
Tt 3u
turbines.m
t f
c
A
B
C
t 4.1
t 4.1
4.1
4.1
TtT TTfawTci Tco m
01
01
0 1η
f
actual adiabatic
y
Tco
T
Tm
Tfaw Tm
Tm
Tci
hypothetical adiabatic
Q.
film edge
θ
θ
g
g
Turbofan Weight Model
Weng =
mcore
100 lbm/s
b0
W0 + W1
OPR
30
b1+ W2
BPR
5
b2
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 2000 4000 6000 8000 10000 12000 14000 16000
wei
ght-
pred
ictio
n er
ror
W/W
i - 1
dry weight Wi [lb]
Operation Models — Mission Profiles
• Each design “flown” over specified total range mission to
– . . . size fuel weight,
– . . . evaluate takeoff performance
• Provides “rubber trajectory” for optimizer
γ
cruise−climb descentclimbtakeoff
h
W
WreserveW W W= fuel−dry MTO
CRγDE
totalR
MTOW
W W−MTO burn
0
hc
cR
Operation Models — Takeoff
Analytical model determines normal-takeoff and balanced-fieldlengths ℓTO, ℓBF .
l
V1
V2
l1
V 2
2
2
Aborted Takeofffull power
full power
maximum braking
V 2(l)
V 2(l)
V 2(l)
l
full power one engine outOne Engine−out Takeoff
Normal Takeoff
lBFTO
A
C
B
TASOPT Inputs (Free Parameters)
Wpay payload
Re range
MCR cruise Mach
ℓfield field length
Nlift max flight load factor
Nland max landing load factor
σcap wing sparcap allowable stress
ρcap wing sparcap density
fgear landing gear weight fraction
SMmin static margin at aft-CG case
CL hmintail lift coefficient at forward-CG case
. . . fuselage size and shape
. . . fuselage aero moment function
. . . engine component efficiencies
etc.
TASOPT Operation
Y
DesignVariables
i, j
for i = 1 : Ni for j = 1 : Nj
Configuration, Weight, Fuel burn, T/O perf, ...
Structural gauges
Volumes and Weights
N
Surface spans, areas
Loads, Shears, Moments
Y
Drag, Engine size+weight
Trajectory, Fuel Weight
Total Weight converged?
Optimize Design VariablesN
Fuel burn minimized?
Optimization
Design Closure
Parameter Sampling
DesignParameters i, j
( j )
( i )
( Range, Payload, Mach Nmax, fstress Tmetal, lBFmax ... )
Sweep, CL, AR, Altitude, FPR, BPR, Tt4 ...
( Sweep, CL, AR, Altitude, FPR, BPR, Tt4 ... )
TASOPT Outputs - I
Optimized design variables:
hCR start-of-cruise altitude
CLCRcruise lift coefficient
Λ wing sweep
t/co airfoil thickness at wing root
t/cs airfoil thickness at planform break
λs inner panel taper ratio
λt outer panel taper ratio
rcls cruise cls/clo at break
rclt cruise clt/clo at tip
OPRD design overall pressure ratio
FPRD design fan pressure ratio
BPRD design bypass ratio
Tt 4TO takeoff turbine inlet temperature
Tt 4CRcruise turbine inlet temperature
TASOPT Outputs - II
Airframe:
• Wing and tail areas
• Wingbox location on fuselage
• Structural gauges and weights
• Engine component sizes, areas
• . . .
Operating variables at all mission points:
• Fuel burn
• Speed, Altitude profiles
• Aero variables CL, CD, CLh. . .
• Engine variables n1, n2, FPR, OPR, Tt 3, Tt 5, ufan, ucore . . .
• . . .
TASOPT Calibration/Verification
B737-800 Sizing, Airframe+Ops Optimization
WMTO Wfuel S Λ◦ λt AR CLCRhCR
Actual 171000 39000 1250 25.00 0.250 10.20 0.550 33500Sized only 166001 38474 1229 25.00 0.250 10.20 0.550 33500Optimized 163862 36923 1289 24.33 0.144 10.61 0.530 34070
OptimizedSized only
Effect of Design Space Expansion
Addition of airfoil, engine, trajectory to design spacegives significantly reduced fuel burn
6
6.5
7
7.5
8
8.5
0.7 0.72 0.74 0.76 0.78 0.8
PF
EI
[ k
J / k
g-km
]
Mach
(none)CL, sweep
t/c, AR, CL, sweepfixed opt engine, t/c, AR, CL, sweep
hCR, rubber opt engine, t/c, AR, CL, sweep
Optimum Aircraft Variation vs Mach, Material Stress
Airframe, engine, trajectory all vary on min-fuel airplane
0.72 0.74 0.76 0.78 0.84
5
6
7
8
9
Mach
PF
EI
[K
J/kg
−km
]
fstress
= (blue) 1.0, 1.25, 1.50 (red)
0.72 0.74 0.76 0.78 0.85
10
15
20
25
Mach
AR
L/D
0.72 0.74 0.76 0.78 0.80
10
20
30
Mach
swee
p [d
eg]
0.72 0.74 0.76 0.78 0.80.1
0.12
0.14
0.16
Mach
t/c
0.72 0.74 0.76 0.78 0.80.5
0.6
0.7
0.8
Mach
CL
C
Lper
p
0 50 100
−100
−50
0
0.72 0.74 0.76 0.78 0.83
3.5
4
4.5
5x 10
4
Mach
Fto
[lb
]
0.72 0.74 0.76 0.78 0.8200
250
300
350
400
Mach
u fan
uco
re [
m/s
]
0.72 0.74 0.76 0.78 0.830
35
40
Mach
alt.
[kft]
N+3 Design Problem Statement
Chosen baseline-aircraft mission (Boeing 737-800):
Payload: 38700 lb (215 lb × 180 pax)Range: 3000 nmi
Find:
“Rubber Airframe + Rubber Engine + Rubber Ops”combination which
- has minimum fuel burn over mission
- meets field length, fuel volume constraints
Transport Configuration Considerations
• Weight characteristics
– Fuselage load paths, structure
– Landing gear length
– Wing lift fraction (wing size and weight)
– Stability and CG range (H tail size and weight)
– Engine-out moments (V tail size and weight)
– Nacelle and engine-mount weights
• Drag characteristics
– Stability and CG range (H tail area and drag)
– Engine-out moments (V tail area and drag)
– “Interference” drags
– Nacelle and pylon drag
– Boundary Layer Ingestion?
• Cabin layout
• . . .
Final N+3 Designs
D8.1 (Aluminum) D8.5 (Composite)
B737−8000.80 Mach15.2 L/D166k MTOW8000 ft field
0.72 Mach22.0 L/D130k MTOW5000 ft field
0.74 Mach24.9 L/D100k MTOW5000 ft field
−70% Fuel Burn−49% Fuel Burn
−45% Fuel Burn
D8.1b19.5 L/D120k MTOW
Fuselage Comparison
700 10 20 30 40 50 60 80 90 100 110 120 ft
9
700 10 20 30 40 50 60 80 90 100 110 120 ft
D8.x
B737−800
8
D8.1 Details
70
010
20
30
40
50
60
80
90
100
110
120 ft
22,23 rows180 seats19"x33"
70
010
20
30
40
50
60
80
90
100
110
120 ft
10 20 30 40 50 60
optionalthrustreverser
N+3 D8.1
Dfan = 49 inFPR = 1.58BPR = 7.1OPR = 35.8
8
Mach = 0.72Area = 1298 ft^2Span = 150 ftMAC = 10.6 ftAR = 17.3L/D = 22.0MTOW = 129965 lbWfuel= 20233 lbRange= 3000 nmiField= 5000 ft
Sh=252 ft^2Sv=144 ft^2
D8.x Configuration (vs B737)
Lifting nose, rear flat fuselage
• increased fuselage carryover lift → smaller wing
• built-in nose-up moment from nose lift → smaller tail
D8.x
B737−800
D8.x Configuration (vs B737)
Wide double-bubble fuselage with lifting nose
• partial span loading via 216” wide fuselage (vs 154”)
• reduced floor-beam weight via center floor support
• improved propulsive efficiency via fuselage BL Ingestion
• reduced profile drag via fuselage BL Ingestion
• shorter landing gear and load path
M(y) M(y)
B737 D8.1
D8.x Configuration (vs B737)
Reduced M = 0.72 with unswept wing (vs M = 0.80)
• reduced CDi, via larger AR allowed by unsweep
• LE slat can be eliminated, via increased CLmax from unsweep
• NLF on wing bottom possible, via unsweep and no slat
• faster load/unload of two aisles compensates for slower cruise
D8.x
30 x 6 per aisle
per aisle23 x 4
(30 minutes load,unload)
(15 minutes load,unload)
B737−800
D8.x Engine/Tail Configuration
• Rear fuselage and tails double as flow-aligning nacelles– only minimal nacelles needed
– shield fan faces from ground observers
• Provides Boundary Layer Ingestion (BLI)– local potential flow M ≃ 0.6 matches fan requirement
– no additional BL diffusion – no streamwise vorticity into fan
• Fin strakes synergystically exploited:– function as pylons carrying engine loads and tail surface loads
– shield fan faces from ground observers
D8.1 BL Profiles at Cruise
• local potential flow M ≃ 0.6 matches fan requirement
• little nacelle diffusion – no streamwise vorticity into fan
• only fan does BLI — core intake sees clean flow- avoids core surge risk
- ideal situation for best overall SFC
1 ft
θ
e
k
M = 0.784H = 1.217 = 0.074 ft
θ
e
k
M = 0.724H = 1.265 = 0.108 ft
θ
e
k
M = 0.623H = 1.372 = 0.185 ft
Breguet Parameter Comparison
Wfuel = WZF
exp
TSFC′
M
D′
L
R
a
− 1
≃ WZF
TSFC′
M
D′
L
R
a
737-800 D8.1 D8.1b D8.5
WMTO 166001 129965 120366 99756
Wfuel 38474 20233 21174 11296
WZF 127528 109732 99192 88460
TSFC′/M 0.694 0.628 0.633 0.500
L/D′ 15.18 22.00 19.53 24.85
W WZF fuelM LW WZF fuelM L W WZF fuelM L
1
0
D8.1 D8.5B737−800
TSFC’ TSFC’ TSFC’D’ D’ D’
D8.1b
CD/CL Breakdown by Component
Induced Fuselage WingTOTAL / 2
B737
Tails Nacelles
0.0193
0.01570.0176
0.0085
0.0053
0.00310.0013
0.0664
0.0151 0.0137
0.0184
0.0512D8.1b
D8.1 Fuselage-BLI Benefit Breakdown
No BLI With BLI With BLIηfan = 0.92 ηfan = 0.90 ηfan = 0.92
WMTO 134585 129997 129721
Wfuel 21925 20504 20172
WZF 112660 109493 109549
TSFC′/M 0.6573 0.6367 0.6267
L/D′ 22.03 22.10 22.08
W WZF fuelM LW WZF fuelM L
0TSFC’ TSFC’D’ D’
fanη = 0.92With BLIfan
W WZF fuelM LTSFC’ D’
With BLIfan1.0
0.9
No BLIη = 0.90 η = 0.92
Wing-Body Panel Solutions
737-800 D8.1
Fuselage Centerline Pressures at Cruise
737-800 D8.1
-0.4
-0.2
0
0.2
0.4
0 20 40 60 80 100 120
Cp
x
-0.4
-0.2
0
0.2
0.4
0 20 40 60 80 100 120x
D8.x fuselage has
• larger carryover lift
• positive moment from nose lift
CM Components About Wing+Fuse A.C.
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.4 0.5 0.6 0.7 0.8 0.9 1
CM
_ac
CL
D8.1 fuse
D8.1 wing+fuse
D8.1 wing
B737 wing
B737 fuse
B737 wing+fuse
D8.x fuselage gives ∆CM=+0.125 built-in trim offset benefit
D8.1 Fuselage Lift and Moment Benefits
• Smaller horizontal tail required for forward-CG sizing case
• Smaller trim drag at all flight conditions
• Smaller wing for given required cruise SCL
D8.1 Spanload at Landing, Forward CG
D8.1 Loading at Landing, Forward CG
D8.1 Spanload at Cruise, Mid-range CG
D8.1 Fuselage Lift and Moment Benefit Breakdown
Std. Fuselage D8.x Fuselage∆fLo = −0.3∆CM = −0.125
WMTO 132813 129721
Wfuel 21374 20172
WZF 111439 109549
TSFC′/M 0.6285 0.6267
L/D′ 21.29 22.08
W WZF fuelM LW WZF fuelM L
0TSFC’ TSFC’D’ D’
1.0
0.9
Standard Fuselage D8.x Fuselage
Tail Size and Loads Comparison
D8.1 horizontal tail is 28% smaller and 27% lighter.Two-point support reduces bending moment and weight.
Sh = 350 ft Sh = 252 ft2 2
B737 D8.1
Wh = 2320 lb Wh = 1690 lb
Tail Size and Loads Comparison
D8.1 vertical tail total is 50% smaller and 70% lighter.5x smaller engine-out yaw moment no longer sizes the VT.
Sv = 144 ft 2
Sv = 284 ft 2
B737 D8.1
Wv = 1570 lbWv = 470 lb
Optimum-Engine “Surprises”
• Optimized takeoff turbine inlet temperature is modest→ Excessive takeoff Tt 4 carries cooling-flow penalty in cruise
• Optimized Bypass Ratio and Fan Pressure Ratio are modest→ BLI favors smaller engine and higher fan loading
D8.1 GE90Tt 4TO 1543◦K 1770◦KBPR 7.1 9.0FPR 1.58 1.50
u u2
Fnet
jetE
( ) Fnet( )=
( ) ( )jetE<
A
B
B
B A
A
. .m u.
m u. 21
2
=
=
+
−
+−
+
++
+
B737-800 → “Morphing” Study
Modifications are made sequentially in 8 steps:
0. B737-800, CFM56, M=0.80, lBF ≤ 8000ft, not optimized
1. B737-800, optimized airframe+ops (engine fixed)
2. Fuselage replaced by double-bubble D8.x fuselage
3. Reduced speed to M=0.76
4. Reduced speed to M=0.72
5. Engines moved from wing, to rear fuselage with BLI
6. Optimized airframe+ops+engines, with 15-year engine im-provements
7. Removed slats (less weight, excrescence drag)
8. Reduced field length to lBF ≤ 5000ft
Span constraint for all cases: b ≤ 118 ft
B737-800, optimized airframe+ops, engine fixed
-120
-100
-80
-60
-40
-20
0
20
-100 -80 -60 -40 -20 0 20 40 60 80 100
Case 0Case 1
Fuselage replaced by double-bubble D8.x fuselage
-120
-100
-80
-60
-40
-20
0
20
-100 -80 -60 -40 -20 0 20 40 60 80 100
Case 1Case 2
Reduced speed to M=0.76
-120
-100
-80
-60
-40
-20
0
20
-100 -80 -60 -40 -20 0 20 40 60 80 100
Case 2Case 3
Reduced speed to M=0.72
-120
-100
-80
-60
-40
-20
0
20
-100 -80 -60 -40 -20 0 20 40 60 80 100
Case 3Case 4
Engines moved from wing, to rear fuselage with BLI
-120
-100
-80
-60
-40
-20
0
20
-100 -80 -60 -40 -20 0 20 40 60 80 100
Case 4Case 5
Optimized airframe+ops+engines
-120
-100
-80
-60
-40
-20
0
20
-100 -80 -60 -40 -20 0 20 40 60 80 100
Case 5Case 6
Removed slats for reduced weight and excrescence drag
-120
-100
-80
-60
-40
-20
0
20
-100 -80 -60 -40 -20 0 20 40 60 80 100
Case 6Case 7
Reduced field length to lBF=5000ft
-120
-100
-80
-60
-40
-20
0
20
-100 -80 -60 -40 -20 0 20 40 60 80 100
Case 7Case 8
Total and Fuel Weight Sequence
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 1 2 3 4 5 6 7 8
Alt_
toc
[ ft ]
W
eigh
t [ lb
]
Case
737-
800,
M=
0.8
737-
800
opt.
DB
fuse
lage
.
slow
to M
=0.
76
slow
to M
=0.
72
engi
nes
to r
ear
opt.
eng
ines
mis
c. m
ods
lBF
< 5
000
ft
WMTO / 2
Wfuel
Alt_toc
Fuel Weight Sensitivity to Span Constraint
0.9
0.95
1
1.05
1.1
1.15
90 100 110 120 130 140 150 160
span [ft]
D/L / D/L_opt
WZF / WZF_opt
Wfuel / Wfuel_opt
737 Wfuel737 D / L 737 W_ZFD8.1 WfuelD8.1 D / L D8.1 W_ZF
20:1 Low-Speed Wind Tunnel Model
L/D from Measurement, Re-Correction
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 2 4 6 8 10 12 14 16 18 20
CL
L/D
D8.1 model, 21 Sep 10
80 mph120 mph
tripped 80 mphtripped 120 mph
Measured L/D = 16.1 for tripped model at 120 mphcorrects to L/D = 22.8 at full-scale Re, low MachD8.1 calc. L/D = 22.0 at full-scale Re, M=0.72
Conclusions
• Transport fuel burn minimization in global design space:
– Airframe: t/c, AR, taper, sweep
– Aero: cruise CL, spanload shape
– Engine: fan pressure ratio, bypass ratio, takeoff T4, cruise T4
– Operation: cruise altitude
• N+3 D8.x configuration and optimization gives up to-49% fuel burn with current Al technology + BLI-70% fuel burn with 2035 forecast tech. + BLI
• Physical origins of improvements have been identified
• Preliminary WT data supports predicted performance
Extra Slides
D8.5 Details
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22,23 rows180 seats19"x33"
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optionalthrustreverser
N+3 D8.5Mach = 0.74Area = 1162 ft^2Span = 170 ftMAC = 8.12 ftAR = 24.85L/D = 25.3MTOW = 101590 lbWfuel= 11485 lbRange= 3000 nmiField= 5000 ft
Dfan = 52 inFPR = 1.42BPR = 20OPR = 50
D13.1 (777 size, M=0.72, 1-class, Aluminum)
Dfan = 93 inFPR = 1.55BPR = 8.0
Sh=744 ft^2Sv=590 ft^2
Range= 7600 nmiMach = 0.83Area = 4780 ft^2Span = 213 ftMAC = 26.7 ftAR = 9.5L/D = 21.1MTOW = 640100 lbWfuel= 212500 lb
42,43 rows500 seats19"x33"
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thrustreverser
D13.1
D15.1 (777 size, M=0.83, 1-class, 3-aisle, Aluminum)
Dfan = 93 inFPR = 1.55BPR = 8.0 Sh=709 ft^2
Sv=710 ft^2
22,23 rows500 seats19"x33"
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LDz
Range= 7600 nmiMach = 0.83Area = 3650 ft^2Span = 226 ftMAC = 15.8 ftAR = 14.0L/D = 24.0MTOW = 440000 lbWfuel= 98000 lb
D15.1
D17.1 (787 size, M=0.85, 3-class, Aluminum)
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thrustreverser
12 x 14 rows = 168 seats 33"x19"
D17.18 x 6 rows = 48 seats 39"x26"
4,6 x 2 rows = 10 seats 60"x30"
Dfan = 60 inFPR = 1.79BPR = 6.70
Range= 8000 nmiMach = 0.85Area = 2410 ft^2Span = 163 ftMAC = 17.8 ftAR = 11.0L/D = 19.0MTOW = 274000 lbWpay = 50000 lbWfuel= 102500 lb
Sh=344 ft^2Sv=340 ft^2
D17.4 (787 size, M=0.85, 3-class, Composite)
thrustreverser
12 x 14 rows = 168 seats 33"x19"
8 x 6 rows = 48 seats 39"x26"
4,6 x 2 rows = 10 seats 60"x30"
D17.4Range= 8000 nmiMach = 0.85Area = 2240 ft^2Span = 192 ftMAC = 14.0 ftAR = 16.4L/D = 20.8MTOW = 200000 lbWpay = 50000 lbWfuel= 60600 lb
Dfan = 72 inFPR = 1.54BPR = 22.0
Sh=338 ft^2Sv=349 ft^2
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