Designing eVTOL for Urban Air Mobility
Skye Weaver Worster Holton-Arms ’20
Emily Fisler Anubhav Datta Clark Doctoral Fellow Associate Professor Alfred Gessow Rotorcraft Center Department of Aerospace Engineering Objectives for Summer Internship
• Learn about and analyze existing eVTOL vehicles
• Design a VTOL aircraft
• Test LiPo batteries
• Design an eVTOL aircraft using collected data
2 Power and Disk Loading for Various eVTOL Aircraft
Source: World eVTOL Directory http://evtol.news/aircraft/
3 Mission for My eVTOL
Range 14.7 miles, 12.8 nautical miles (25.6 round-trip) Additional 5 minute hover
4 Mission Criteria
Maximum weight (gross takeoff weight) 2000 lbs Payload (weight of people and cargo) 400 lbs
Edgewise rotor Tiltrotor Lift/drag ratio = 5 Lift/drag ratio = 9 structure factor 0.24 structure factor 0.3 Cruise velocity 70 kt Cruise velocity 150 kt 5 Design Process
1. Objective and criteria
2. Conventional (turboshaft) design
3. Battery testing
4. Conversion to electric power
6 Convergence of Design
2000 Starting Weight 2000 1800
s Guess #1 = 2000 500
b
l
,
t 1600
h
g
i
e 1400
W
f
f
o 1200
e
k
a
T 1000
s
s
o r 800 Final weight ~1300
G
d Guess #2 = 500
e 600
t
c
i
d
e 400
r
P 200
0 0 2 4 6 8 10 12 14 16 18 20 Iteration Number Disk loading = 8 lb/sqft Structure weight = 0.24 GTOW 8 Disk Loading
푤푒𝑖𝑔ℎ푡 퐷퐿 = 푡표푡푎푙 푟표푡표푟 푎푟푒푎
퐴푟푒푎 = # 푟표푡표푟푠 × 휋 × 푟푎푑𝑖푢푠2
Surface area 푤푒𝑖𝑔ℎ푡 퐷퐿 = of 4 rotors # 푟표푡표푟푠 × 휋 × 푟푎푑𝑖푢푠2
9 Weight Predictions
2000
1800
1600
1400
1200
s
b
l
,
t h 1000
g
i
e
W 800
600 Payload Weight 400
200 Fuel Weight
0 4 6 8 10 12 14 Disk Loading, lbs/sqft 10 Rotor Radius
5
4.5
4
3.5
t
f
, 3
s
u
i
d a 2.5
R
r
o
t o 2
R
1.5
1
0.5
0 4 6 8 10 12 14 Disk Loading, lbs/sqft 13 Design Method
1. Objective and criteria
2. Conventional (turboshaft) design
3. Battery testing
4. Conversion to electric power
14 Battery Basics
Voltage Charge Current (Volts) (Coulomb, Ampere hour) (Ampere)
The force pushing The total energy in a battery The amount of electricity electricity through a circuit moving through a circuit
Charge (how full the water gun is)
Current (how fast water flows through the nozzle)
Voltage (the force put on the trigger)
15 Battery Discharge
Power C-Rate Energy (Watts) (Ampere hour) (Watt hours)
The rate at which electrical The rate at which a battery is discharged The total electrical force force is applied applied over time, usually Inversely effects discharge time: if a battery takes 1 kilowatt hours hour to discharge at 1 C, it will take 30 minutes at 2C
Power C–rate= Energy
푎푚푝푒푟푒 퐶표푢푙표푚푏 = 푊푎푡푡푠 = 푉표푙푡푠 ∗ 퐴푚푝푠 푠푒푐표푛푑 푊푎푡푡 ℎ표푢푟푠 = 푊푎푡푡푠 ∗ ℎ표푢푟 푉표푙푡 = 퐴푚푝푠 ∗ 푟푒푠𝑖푠푡푎푛푐푒
16 Batteries
Lithium Polymer Batteries (LiPo)
3 950 milliamp hours (0.95 Ah) 4 7.4 Volts 2 cells 1 1300 milliamp hours (1.3 Ah) 2 11.1 Volts 2 cells
17 Experiment Setup
LiPo battery Discharge unit
Fireproof battery Battery monitor safe bag
18 Raw Data
12.5
12 Test 1 Test 2 11.5 Test 3 11
]
V
[
e g 10.5
a
t
l
o
V 10
9.5
9
8.5 0 2 4 6 8 10 12 14 16 18 Time [min] 19 Data from Battery 1
LiPo1 103
102
]
g
k
/
W
[
r e 101
w
o
P
c
i
f
i
c
e
p
S 100
10-1
10 30 60 100 150 200 Specific Energy [Wh/kg] 20 Data from Battery 1
LiPo1 103
102
]
g
k
/
W
[
r e 101
w
o
P
c
i
f
i
c
e
p
S 100
10-1
10 30 60 100 150 200 Specific Energy [Wh/kg] 21 Data from Battery 1
LiPo1 103
102
]
g
k
/
W
[
r e 101
w
o
P
c
i
f
i
c
e
p
S 100
10-1
10 30 60 100 150 200 Specific Energy [Wh/kg] 22 Data from Battery 2
LiPo2 103
102
]
g
k
/
W
[
r e 101
w
o
P
c
i
f
i
c
e
p
S 100
10-1
10 30 60 100 150 200 Specific Energy [Wh/kg] 23 Data from Battery 3
LiPo3 103
102
]
g
k
/
W
[
r e 101
w
o
P
c
i
f
i
c
e
p
S 100
10-1
10 30 60 100 150 200 Specific Energy [Wh/kg] 24 Data from Battery 4
LiPo4 103
102
]
g
k
/
W
[
r e 101
w
o
P
c
i
f
i
c
e
p
S 100
10-1
10 30 60 100 150 200 Specific Energy [Wh/kg] 25 Final Data
All LiPo Batteries 103
102
]
g
k
/
W
[
r e 101
w
o
P
c
i
f
i
c
e
p
S 100
10-1
10 30 60 100 150 200 Specific Energy [Wh/kg] 26 Design Method
1. Objective and criteria
2. Conventional (turboshaft) design
3. Battery testing
4. Redesign for electric power
27 Redesign for Electric Power
• Engine Motor
• Fuel Battery
• Data collected from batteries used to estimate
gross takeoff weight, power, and energy
28 Weight Predictions
4000
3500
3000
2500
s
b
l
,
t h 2000
g
i
e
W 1500
1000
500 Payload Weight
0 2 4 6 8 10 12 14 Disk Loading, lbs/sqft 29 Rotor Radius
9
8
7
6
t
f
,
s
u
i 5
d
a
R
r
o 4
t
o
R 3
2
1
0 2 4 6 8 10 12 14 Disk Loading, lbs/sqft 32 Weight vs Rotor Size
Weight increases with disk loading… But rotor size decreases with disk loading! .
4000 9
3500 8
7 3000
6
t
2500 f
,
s
s
b
u
l
i 5
,
d
t
a h 2000
R
g
i
r
e
o 4
t
W
o
1500 R 3
1000 2
500 1
0 0 2 4 6 8 10 12 14 2 4 6 8 10 12 14 Disk Loading, lbs/sqft Disk Loading, lbs/sqft
33 Final eVTOL Specifications
lbs Disk Loading = 4 ft2 Gross takeoff weight = 1907 lbs
Payload = 400 lbs
Battery weight = 810 lbs
Rotor radius = 6.2 feet
Total Mission Time = 27 minutes
Mission Range = 25.6 nautical miles (29.5 miles) 34 Thank You!
35