principles of regenerative electric-powered flight j. philip barnes 04 april 2014 update 1...

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Principles of Regenerative Electric-powered FlightJ. Philip Barnes 04 April 2014 Update

Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014 www.HowFliesTheAlbatross.com

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Presentation Contents

• Nature’s “Regen” ~ the Great Frigate Bird• Regen aircraft elements & operating modes• “Windprop” aero design and performance• DC motor-generator, controller, and battery• “Regenosoar” vehicle & system performance • Summary & Recommendations

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Nature’s Regen Aircraft ~ the Great Frigate Bird

• Flight sustained by atmospheric vertical motion• Energy rate sensor ~ air temp, air pressure...?• Permeable plumage ~ no water landing or takeoff• Feed by surface plucking ~ Pterodactyl heritage?

• Self-contained takeoff• Emergency thrust • Sortie radius to 1800 km • Sortie duration up to 4 days

• Thermal day and night up to 2800 m• Lowest wing loading of any bird

Data: Henri Weimerskirch, et.al. Nature Jan 2003

Photography: Phil Barnes

30-year lifespan


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Windprop• Fixed rotation direction• Sign change with mode

• Thrust, Torque• Power, Current

• Self-contained takeoff • Emergency cruise/climb• Exploit vertical air motion

Optional solar panel

Energy Storage:• Battery• Ultra capacitor• Flywheel motor-generator

ESU

Regen Aircraft Elements and Operation


MotorGen

SpeedControl

5

0

0

0

0

1

0

0

0

000

2

00

0

0

0

3

4

Radius from Centerline, m0 100 200 300 400 5000100200300400500

Elevation, zo ~ m

0

500

1000

1500

2000

2500

3000

3500

4000

u, m/s

Thermal Updraft Contours

Total Energy = Kinetic + Potential

Total Energy = Kinetic + Potential + Stored

• 1oC warmer-air column• 20-minute lifetime• ~ solar power x 10


U ~ m/s

Elevation, zo ~ m

12

34

6

Dual-role Propeller andAirborne Wind Turbine

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Blade angle (b ) at radius (r)is measured from rotationplane to the chord line at (r)

Propeller Wake, Pitch, and Blade Angles

More blades at fixed thrust & diameter:• More wakes (one per blade)• Higher pitch ~ wakes farther aft / rotation• Lower rotational speed, lower tip Mach • Upshot: ~ similar efficiency, 2 to 8 blades

• Wake induces downwash (normal to local section) •Pitch:

helix length per rotation htip = 2 p R tan btip

• Uniform pitch: r tan b = R tan btip

• Blade tip angle (btip): 14o ~ low pitch 30o ~ high pitch


HorseshoeVortices

r

R

8

Windprop Blade Angle and Operational Mode

v

wr

b

w

Pinwheel

• Pinwheeling: Zero angle of attack, root-to-tip- No thrust, no torque, small drag

v

wr

L b

w

Propeller

• Efficient prop: Rotate ~115% of “pinwheel RPM,” or fly at 87% of “pinwheel airspeed”

v w

r -L

b

w

Turbine

• Efficient turbine: Rotate ~ 87% of “pinwheel RPM,” or fly at 115% of “pinwheel airspeed”

• Define: “Speed ratio,” s v / vpinwheel = v / [ wr tan b ]

• Specify symmetrical sections & uniform pitch


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Speed Ratio, s ≡ v / ( w R tan btip) 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Force Coefficient, F ≡ f/(qpR2)

B=2

2

B=8

8

F

Low-RPM 8 Blades, btip = 30o

Pinwheel

F= -0.011 @ B=2

F= -0.008 @ B=8

Propeller ~ climb

Max efficiencyRegeneration Max capacity

Regeneration

Propeller ~ cruise

Speed Ratio, s ≡ v / ( w R tan btip) 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

Efficiency

0.0

0.2

0.4

0.6

0.8

1.0

h Turbine t w / (f v)

Blades_btip

2_14o

8_30o

c l_minc l_max

Propellerf v / ( t w)

High-RPM 2 Blades, btip = 14o

Windprop Efficiency and Thrust

r / R 0.00 0.25 0.50 0.75 1.00

Blade Geometry

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Thickness

Chord, c/ R

Sym. Sectionsr tan b = R tan b tip

hub


sc

NF

DT

DD

sc

NF

vLDn

z

D

T

D

wp

D

wp

n

22

/

/1

)/(1

RR

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How Flow the ElectronsMotor-generator principles

Synergy: motor-gen & windpropDC Voltage conversion

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e

t

w

E

N turns

Generating

i

vi vq

Fp

Fq

B

i

Electromotive force, e= potential energy / charge= work / charge, (Fp / q) L= 2 N w (D/2) B L e = NDBL w ≡ k w

Change to generator mode:Same direction, rotation, wSame sign for EMF, e Sign change of torque, t Sign change of current, i

Torque, t = 2N (D/2) B (dx/dt) dq = 2N (D/2) B (dq/dt) dxt = NDBiL = NDBL i = k i

(+) Charge (q) with velocity, V in magnetic field of strength, B:Force vector, F = q V x B

e

t

w

E

N turns

Motoring

B

i

vi vq

Fp

Fq

B

i

L

Motor-generator Principles

=tw eiBoth

modes


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System Motoring and Regeneration Efficiencies

Pulse-width modulation (PWM) d ≡ “Duty cycle” ; h ≈ 0.99 d 0.25

(Refs 1,2)

"Ideal system efficiency" ignoring controller & torque lossesh system motor ≈ t w/(eb i) ≈ e i / (eb i) = e / eb = k w / eb h system regen ≈ eb i / (tw) ≈ eb i / (ei) = eb / =e eb / (k w)

Inverter(for brushless MG)

h ≈ 0.98 (Ref.3) Rm

Torque lossbrushes,iron loss,windage...

em

t+Dt

w

Vm

Rb

eb

Vb

ebQuote regen power here

Refs: (1) AiAA 2010-483, Lundstrom, p.8 ; (2) NASA CP 2282, Echolds, p.89 ; (3) Technical Soaring, Vol. xxi, No. 2, Rehmet, p. 39

i MotorRegen


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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Speed Ratio, kw/eb = EMF Ratio, emg/eb

Non-dimensional Characterization of Permanent-magnet DC Motor-generator-battery System Performance ~ Theory and Test Data

eb

Rt

em

Motor-generator & Battery ~ Performance Envelope and Data

REGENERATIONLMC "generator curve"48V / 3,600 RPMk = 0.16 N-m/ARt = 0.041 OhmLMCLTD.net

MOTORINGEEMCO 427D10024V / 15,000 RPMk = 0.015 N-m/ARt = 0.075 Ohm

THEORETICAL EFFICIENCY, kw/e bCURRENT GROUP, i R

t / eb

TORQUE GROUP, t Rt / (k e

b )

Phil

Barn

es A

pr-0

8-20

11

eb /(kw)

i

t

100% Duty Cycle


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Battery effectiveshuffled position

Takeoff / climb

Cruise

~Pinwheel

Best regen

Max regen

MotorGen

Periodic (about once per minute) battery shuffle via rotary switchensures equal time for all batteries at each “totem pole” position

Regeneration enjoys reduced active battery resistance

“Low-tech” Regen DC Electric Propulsion With Battery Shuffler

VoltageNode

Electrical Ground

4

5

3

2

1

Negativeterminalof batterynumber:

E D C BF

EDC

B

BATTERYSHUFFLESWITCH

1

5

Positiveterminal of battery number:

DCBAE

DCB

A2

3

4

Applicable: Brushed or Brushless, but no pulse-width modulation

Phil

Barn

es 0

7 Ap

r 201

1

F

E

D

C

B

A

Battery Series “Totem Pole” Voltage Node

Rotate 80o

Clockwise,then counter

clockwise


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• DCBC: Key enabler, efficient bi-directional power management– Only the motoring mode is shown in the introductory graphic above

• “Boosts” DC voltage ~ 0-500 % with minor input/output ripple • Enables low-voltage battery to drive high-voltage LED lamp*• Enables reduced battery totem pole length, i.e. Toyota Prius* • DC voltage “boost” is controlled by PWM “duty cycle”• Power in ~ Power out: DC output current is thus reduced• Options: brushed-DC/low voltage or brushless/high voltage• Adjusts effective battery voltage to efficiently drive the M-G• Boosts motor-gen effective EMF for efficient battery recharge

* Wikipedia, “DC boost converter”

Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014

DC boost converter enables efficient motoring & regen

CL

VB

M-GiGBTPWM

16Regenerative Electric-powered Flight J. Philip Barnes 04 Apr 2014

|-- --|dt t

d ≡ duty cycle ; t ≡ periodiGBT gate PWM

CL

VB

Mot-gen

iGBTPWM

VM

DC boost converter – Equivalent circuits

L diB /dt

C dVM/dtVB

iB

iM

VM

iGBT off

C dVM/dt

L diB /dt

iB

VB

iM

VM

iGBT on


DC boost converter – Voltage gain & conversion efficiency

L DiB2 /[(1-d)t]

C DVM2 /[(1-d)t]VB

iB

iM

VM

Segment 2: iGBT off for Dt = (1-d)t

C DVM1/(dt)L DiB1 /(dt)

iB

VB

iM

VM

Time segment 1: iGBT on for Dt = dt

[a] Voltage loop: VB - L DiB1 /(dt) = 0[c] Output current: iM - C DVM1 /(dt) = 0

[b] VB - L DiB2 /[(1-d)t] = VM

[d] iB - C DVM2 /[(1-d)t] = iM

[e] PWM cycle: DiB1 + DiB2 = 0 [f] DVM1 + DVM2 = 0

• Voltage & current gains set by duty cycle (d) alone [high-frequency assumed]• Efficiency is unity (resistance neglected) and is thus unaffected by L, C, d, t• “Deltas” (D) represent ripple applied to input current (iB) & outputs (iM, VM)

[g] Combine [a,b,e]: VM/VB = 1/(1-d) [h] via [c,d,f]: iM/iB = 1-d

Combine [g,h]: h ≡ iMVM /(iBVB) = 1


DC boost converter - efficiency and regen application

• 90o rotary mode selector switch for motoring or regeneration• Low-voltage option: Batteries in parallel, brushed-DC motor-gen• Hi-voltage option: Batteries in series, inverter & brushless DCMG

Regen

M-G

Motor

"Evaluation of 2004 Toyota Prius,"Oakridge National Lab, U.S. Dept. of Energy

233 Vdc in

5 10 15 20 kW

PWMiGBT

CL VB

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"RegenoSoar" Air Vehicle and System Performance

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RegenoSoar Design Rationale

Configuration Rationale• Maximum laminar airflow aero & counter-rotation props• Pusher avoids windprop helix downstream aero upset• One-person handling/steering (remote or in the cockpit)• Winglets include tip wheels (wings flex up under load)


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RegenoSoar ~ In Flight

Applications and Operations• Fleet broadcast energy rate• High-altitude earthwatch• Jet-stream rider• Storm rider


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Vehicle Performance ~ New Formulation, New Insight

L= nn w

T-D

w

v

f

g

Frigate Bird• T/D=0 (no thrust)• sink rate (-dz/dt) = nn(D/L)v

Frigate Bird and Regen• sink increases with g-load (nn)• sink increases with airspeed (v)

Regen T/D• climb: 6.3 • cruise: = 1.0 • solar-augmented glide: 0.5• pinwheel glide: -0.1• efficient regen (thermal): -0.4 • capacity regen (descent): -1.0

g

norientatio of regardless

1][(T/D)v(D/L)ndz/dt

Therefore,

γvsindz/dtrate,climb)3

(T/D)(D/w)/w)2

D/Ln(L/W)(D/L)/W)1

vsinγ(D/W)]v[(T/W)

/Wndefinev/W;bymultiply

state}{steadysinγT

n

n

n

T

D

L

WDDerive steady-climb Equation

Note: nn= cos g /cosf cL = nn w / (qs)


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Regenerative Flight Equation

“Total Climb”

Rate of change oftotal specific energy

Updraft “Total Sink”

Still-air “clean” sink rate

Effect ofwindprop

D

Tv

L

Dnuz nt 11

“Exchange Ratio,” as applicable:• turbine system efficiency ~71% • 1 / propeller system efficiency• 0 for pinwheeling (no exchange)


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Ground-relative Climb Rate, m/sMax-capacity Regeneration in the Thermal

Normal Load Factor, Nn

1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

Elevation, m

0

500

1000

1500

2000

2500

3000

0.0

1.0

1.51.6

0.5

Ground-relative Climb Rate, m/sMax-efficiency Regeneration in the Thermal

Normal Load Factor, Nn1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

Elevation, m

0

500

1000

1500

2000

2500

3000

3500

2.2

0.0

1.01.5

2.0

0.5

Total Specific Energy-gain Rate, m/sMax-efficiency Regeneration in the Thermal


1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

Elevation, m

0

500

1000

1500

2000

2500

3000

3500

2.5

0.0

1.01.5

0.5

2.0

Climb and Regeneration in the Thermal (minimum-sink airspeed)


Climb rate Contours Energy rate Contours

Equilibrium Regeneration

Optimum

Total Specific Energy-gain Rate, m/sMax-capacity Regeneration in the Thermal


1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.80

500

1000

1500

2000

2500

3000

0.0

1.01.5

2.0

0.5

2.1

Elevation, m Elevation, m

Elevation, m

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Item / mode ---> Climb max L/D Cruise max L/DPinwheel max L/D

Regen max efficiency, minimum sink,

zo=1480-m

Regen max capacity, minimum sink,

zo=1480-m

Airspeed, v ~ km/hr 85.0 85.0 85.0 77.2 77.2

Updraft, u ~ m/s 0.00 0.00 0.00 3.72 3.72

Turn radius, r ~ m n/a n/a n/a 56.5 56.5

Load factor, n ~ g 1.00 1.00 1.00 1.30 1.30

Lift coefficient, cL 0.64 0.64 0.64 1.12 1.12

Drag coefficient, cD (clean) 0.022 0.022 0.022 0.040 0.040

Installed thrust/drag ratio, T/D 6.33 1.00 -0.10 -0.40 -1.01

Installation penalty, D/D= -T/D 0.17 0.09 0.10 -0.03 -0.03

Clean sink rate, still air, n (D/L)v ~ m/s 0.75 0.75 0.75 1.03 1.03

Climb rate in still-air, dz/dt ~ m/s 4.00 0.00 -0.83 -1.43 -2.06

Total energy rate, dz t /dt ~ m/s -5.40 -1.05 -0.83 2.58 2.18

Ground-observed climb, dz o /dt ~ m/s 4.00 0.00 -0.83 2.29 1.66

Windprop speed ratio, s 0.57 0.85 1.00 1.15 1.75

Windprop speed ~ RPM 1096 735 625 494 324

Windprop Force group, F 0.92 0.14 -0.0070 -0.10 -0.26

Windprop efficiency, ht or hp 0.63 0.84 n/a 0.85 0.64

Powertrain efficiency (non-windprop) 0.80 0.85 n/a 0.85 0.8

System efficiency hst or hsp 0.50 0.71 n/a 0.72 0.51

Exch. ratio, 1/hsp : hst : 0 applic.) 1.98 1.40 0.0 0.72 0.51

Total Shaft power, tw ~ kW 29.5 3.50 0.00 -1.36 -2.58

Energy storage rate ~ kW -36.9 -4.12 0.00 1.16 2.07

0.82

0.870.82

0.88

Regenerative Flight Equation Applied for RegenoSoar


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Summary and Recommendations Regenerative Electric-powered Flight

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Regenerative Electric-powered Flight

• The Great Frigate Bird ~ nature’s “regen”– Self-contained takeoff & emergency thrust on demand– Energy extracted from vertical atmospheric motion– Energy rate sensor, flight sustained day-and-night

• “Energy Synergy” of the Windprop & Motor-Gen– Optimum “speed ratios” about 87% & 115% by mode

• Windprop: 8 blades spin slow, quiet, & efficient– Pinwheeling ~ imposes only minor performance penalty

• DC boost converter - efficient bi-directional power• Climb/sink rates, any mode, g-load, orientation• Climb in the thermal, even with maximum regen• Regen in ridge and wave lift to extend flight• Regenerative Flight Equation ~ total energy rate• We’re good to go ~ Let’s emulate the Frigate Bird


principles of regenerative electric-powered flight j. philip barnes 04 april 2014 update 1...

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