D8.x Aircraft Development — Update
Mark Drela
Aero & Astro Presentation
20 Oct 10
NASA’s N+3 Program
Chosen Current-Technology Baseline:
B737-800 mission: 3000 nmi, 180 PAX
N+3 Objective:
Identify concepts and technologies needed for
70% (!) reduction in Fuel / PAX-mile by 2025
Good bet: Tweaking current designs won’t do it
Presentation Outline
• Transport Aircraft System OPTimization (TASOPT)
• D8.x “Double Bubble” transport aircraft concept
TASOPT Objective
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
Collection of coupled low-order physical models
• Primary structure
• Aero
• Engine
• Balance, trim, stability
• Flight trajectory
TASOPT Operation
• Inner sizing loop (design closure)
– Specify design inputs
– Size airframe via L=W, stresses, stability&trim
– Size engines via T=D
– Size fuel burn for design range
– Iterate on initial weight guesses
• Middle optimization loop
– Evaluate fuel volume, takeoff performance
– Tweak chosen subset of inputs (design variables) to minimize fuel
burn, with chosen constraints on fuel volume, takeoff, span
– Back to inner loop
• Outer parameter-sampling loop
– Explicitly change chosen subset of inputs (design parameters)
– Back to inner loop
TASOPT Operation
Initial weight guesses
Structural gauges
Volumes and Weights
Y
N
Surface spans, areas
Loads, Shears, Moments
DesignVariables
Optimize Design Variables
Y
N
DesignParameters
Fuel burn minimized?
Drag, Engine size+weight
Trajectory, Fuel Weight
Total Weight converged?
i, j
i, j
for i = 1 : Ni for j = 1 : Nj
Sweep, Altitude, FPR, BPR, Tt4 ... Configuration, Weight, Fuel burn, T/O perf, ...
( j )
( i )
( Sweep, Altitude, FPR, BPR, Tt4 ... )
( Range, Payload, Mach Nmax, fstress OPR, Tmetal, lBFmax ... )
Calibration/Verification
B737-800 Sizing, Airframe+Ops Optimization (fixed engine)
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
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
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
D8.x Configuration (vs B737)
Wide double-bubble fuselage
• partial span loading via 216” wide fuselage (vs 154”)
• reduced floor-beam weight via center floor support
• shorter landing gear and load path
M(y) M(y)
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)
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
737−800
D8.x
30 x 6 per aisle
per aisle23 x 4
(30 minutes load,unload)
(15 minutes load,unload)
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
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 Sh = 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◦K
BPR 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
=
=
+
−
+−
+
++
+
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
Summary
• Examination of entire Airframe+Engine+Ops design space(TASOPT)
• Global optimization for minimum fuel burn
• N+3 D8.x configuration, reduction in Mach, give up to49% fuel burn decrease with conventional technology(45% decrease with 118 ft span constraint)
N+3 Phase II
• Detailed design of rear fuselage/engine installation
• Test 1:4 powered model of fuselage + stub wings
• Investigate performance of small-core engines (Pratt)
22x14 ft
D8.1 Low Speed1/4 scalePowered model
D8.5 Details
70
010
20
30
40
50
60
80
90
100
110
120 ft
10 20 30 40 50 60
22,23 rows180 seats19"x33"
70
010
20
30
40
50
60
80
90
100
110
120 ft
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"
70
10
20
30
40
50
60
80
90
100
110
120
130
140
150
160
170
180
190 ft
70
10
20
30
40
50
60
80
90
100
110
120
130
140
150
160
170
180
190 ft
10 20 30 40 50 60 70 80 90 100 11010 20 30 40
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"
70
10
20
30
40
50
60
80
90
100
110
120
130
140
150
160
170
180
190 ft
70
10
20
30
40
50
60
80
90
100
110
120
130
140
150
160
170
180
190 ft
10 20 30 40 50 60 70 80 90 100 110
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)
70
10
20
30
40
50
60
80
90
100
110
120
130
140
150
160
170
180
190 ft
70
10
20
30
40
50
60
80
90
100
110
120
130
140
150
160
170
180
190 ft
10 20 30 40 50 60 70 80 90 100 11010 20 30 40
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
70
10
20
30
40
50
60
80
90
100
110
120
130
140
150
160
170
180
190 ft
70
10
20
30
40
50
60
80
90
100
110
120
130
140
150
160
170
180
190 ft
10 20 30 40 50 60 70 80 90 100 11010 20 30 40
TASOPT Fuselage Loading Model
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
TASOPT Fuselage Section Model
R fuse
dbw
Lv
v
tτtσ
tσ db
added bending material
t skin
Askin
skincone cone
skin
skin
stringers
fuse
max
A
floor
floor beams
TASOPT Wing Geometry and Loading Model
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
TASOPT Wingbox Section Model
t cap
twebh
fuelA
wc
box
box
hboxhr
TASOPT Engine Model
.m
8
6
0
4
m.
.mα
πdπf
πb3
5
74a
πhcπlc ht lt
4.5πc
2.5
αc
4.1
πfnK inl
2
1.9
2.11.8
1.8
N NN G/
∆ ∆h h
4.9
πtn
l hl
core
core
TASOPT Fuselage Drag Model
x
A(x)∆∗ ∗ΘΘ, , (x)
y
z ∗ ∗, , (x)δ θ θ
b (x)0
Θwake
(x)Λ
(x)λ