1

15 - 17 september 2004 4th European Micro-UAV meeting

Toulouse

Micro engines for micro drones propulsion

Joël Guidez, Clément Dumand, Olivier Dessornes, Yves Ribaud

Office National d’Études et de Recherches Aérospatiales

2

Outline of the presentationOutline of the presentation

• 1/ Introduction : micro-systems

• 2/ Application to micro-drones

• 3/ Energetics micro-systems

• 4/ Micro-turbine

• 5/ Conclusion and perspectives

3

1 / INTRODUCTION1 / INTRODUCTION

What is a MEMS (Micro Electro-Mechanical System) ?

• Miniaturization • Components : silicon, silicon-carbide• Applications :

SiC

Si

- sensors

- actuators

- energetics micro-systems

4

What ’s MEMS ?What ’s MEMS ?

a sensitive element…

…frequently in silicon

Actuator(switch)

Accelerometer

electronics

packaging

puissance RFet transmission

capteur de température onvertisseur CAD

filtres digitaux

cea Leti

Gear

Miror

Pressure sensor

4

But, it ’s also : an energetics micro-systemBut, it ’s also : an energetics micro-system

Micro-turbine

Micron-scale counterflowheat exchanger

20 mm

MIT

1 mm

TMIT(Tokyo)

5

2 / APPLICATION TO MICRO-DRONES2 / APPLICATION TO MICRO-DRONES

• Mini and micro-drones

– fixed wing/rotating wing

– flapping wing

• Main specifications

6

MicrobatCaltech

7

Various MAV versions

Various MAV versions

8

Microdrone : specificationsMicrodrone : specifications

• «Flying binocular» : system for collection of proximity information

• Dimension up to 15 cm : length and wingspan• Hovering, flight at 50 km/h • Autonomy : 20 mn to 1h• Power : 20 to 50 W• Mass 80 g• Data transmission in real time

Sensor Actuator Micro motorFuel tank

Electronic

Electrical/mechanical converter

(Video or other)

9

3 / Energetics micro-systems : a lot of micro-systems and actors

3 / Energetics micro-systems : a lot of micro-systems and actors

• Micro-turbine :• MIT, Tokyo, Hoseï, Sendaï University, Tokyo Metropolitan Institute of Technology,

IHI, Onera, VKI, ERM, Leuwen University, National University of Singapore...

• Reciprocating free piston engine :• Georgia Tech, Berkeley, Birmingham University, KAIST (Corée)

• Wankel Micro-motor :• Berkeley, Birmingham University

• Thermoelectric micro-generator :• USC, Tohoku University, CEA, Onera, National University of Singapore

• Thermophotovoltaïc generator :• National University of Singapore, California State Polytechnic University ...

• Liquid rocket engine : • MIT, Uppsala University, QinetiQ, LAAS

10

Reciprocating free-piston engineReciprocating free-piston engine

Exhaust valve

Combustion chamber

piston

Main shaft

Inlet valve

stator of electric generator

Electrical leads

cea Leti

Single variation

KAIST Korea

1 mm thick glassCombustion chamber 1 mm

Piston 2 x 2 mm

10

11

Mini and micro-Wankel engineMini and micro-Wankel enginePresently 2.4 mm Si modelAim : Si fabrication, 1 mm x 300 µm10 to 100 mWSiC-coated Si

Berkeley

11

13 mm3 W10000 rpm

12

MIT Micro-turbine MIT Micro-turbine

13

hydrogene

air inlet compressor

turbine.,..

exhaust

ONERA micro-turbine « upper combustor without premixed channel » ONERA micro-turbine « upper combustor without premixed channel »

Combustion chamber

14

PP

P NN

Ceramic

Semi conductorP or N

MetallicConductor

Hot Junction

Cold junction

U

i

Thermoelectric microgeneratorThermoelectric microgenerator Thermoelectric wall

Ge-Si : 3 W/cm² 5%

THERMOELECTRIC GENERATORTHERMOELECTRIC GENERATOR

Combustion chamber

« Swiss roll »

USC

15

Comparison between micro-systemsComparison between micro-systems

• Reciprocating free piston

engine

• rotating engine (Wankel)

• turbine engine

• thermoelectric system

• thermophotovoltaïque

system

Difficulties

Heat losses, friction, low frequency

Low rotating speed and low power

Complexity, high rotating speed, journal bearing

Connectic, catlytic combustion

To control this technique

Advantages

Well known

Well known

Good conversion mecanic/electric

Quasi static system

Relatively simple System quasi static

16

4 / MICRO-TURBINE4 / MICRO-TURBINE

• Thermodynamic cycle

• Energetic balance

• Small scales problems...

• Combustion/ignition 4 mm

200 m

MIT

17

Thermodynamic cycleThermodynamic cycle

S

T

th = 1 - 1/c -1/

c = 3 th=0.27

c = 4 th=0.33

c=0.7 et t=0.6,

thus cycle 0.11 à 0.14

Brayton-Joule cycle

C

C

Ch comb T

T

Ch comb.

18

56 Wconvection 8 Wradiation 48 W

Thermal losses inexhaust gases( T = 1103 K )

430 W

Net Power

Work efficiency3.4 %

34 W Internal Heat Exchanges

External Heat Losses56 W

convection 8 Wradiation 48 W

Air flow0.4 g/s

Tair = 288 K

Tcompressor = 670 K

Tturbine= 840 K

Tchamber = 1600 K

Tstator = 930 K

Fuel : 46.6 g/h

6 W

19 W 33 W

16 W

12 W

23 W

3 W

34 W 82 W

28 W

9 W

51 W

MICRO-TURBINE : ENERGETIC BALANCE MICRO-TURBINE : ENERGETIC BALANCE

P comb = 503 W

Net power17 W

Global efficiency3,4 %

18

19

COMPARISON OF PERFORMANCES COMPARISON OF PERFORMANCES

1

10

100

1000

10000

1 10 100 1000 10000 100000

BATTERIES

SUPER CAPACITORS

MICRO TURBINE

1,7%<global efficiency<10% Fuels : H2, CxHy

Specificenergy

Wh/kg

Specificpower

W/Kg

Autonomy : 1 h 20 mn

20

Micro-scale combustorsSpecific problems

Micro-scale combustorsSpecific problems

• 1/ Low Reynolds number (< 1000)

• 2/ Residence time close to reaction time (Da around 1)

• 3/ Important heat losses (ratio S/V unfavourable)

• 4/ To improve ignition system (reusable)

• 5/ Quenching, self ignition in premixed channel

mixing

21

Combustion :mixing, residence time, quenching

Combustion :mixing, residence time, quenching

Da = residence time/ reaction time

Da > 1 c 0,5 ms, thus Vmin = m’.c.r.T/P (4 mm)3

Quenching distance : d// = Pe.a/SL 0,2 mm (H2) 0,7 mm (Propane)

fuel

air

Mixing fuel/air

Mixing fresh gas/burned gas

22

0D model results 0D model results

= s m

Residence time inthe micro-combustor

Heat losses Mixing ratio

PSR

PASR

23

Y

Z

-0.0005 0 0.0005-0.0025

-0.002

-0.0015

-0.001

-0.0005

0

Y

Z

-0.0005 0 0.0005-0.0025

-0.002

-0.0015

-0.001

-0.0005

YZ

-0.0005 0 0.0005-0.0025

-0.002

-0.0015

-0.001

-0.0005

0

X

Z

0.002999940.003499940.003999940.004499940.004999940.00549994

-0.0024

-0.0022

-0.002

-0.0018

-0.0016

-0.0014

-0.0012

-0.001

-0.0008

-0.0006

-0.0004

-0.0002

0Temperature

240023002200210020001900180017001600150014001300120011001000900800700600500400300

Temperature240023002200210020001900180017001600150014001300120011001000900800700600500400300

ONERA ’s CFD codeONERA ’s CFD code

Development tool in order to select the best configurations of the micro-combustor

m’ = 0,1 g/sP = 3 barTp = 950 KModel : Ecklund (7 reactions)Equi.ratio = 0,6

24

Set-up for combustion testsSet-up for combustion tests

Vessel cooled by nitrogen

Injection strut cooled,air and fuel inlet

Window for optical measurements(IR caméra, Raman...)

Micro-combustion chamber

Air and fuel inlet

ExhaustCombustion products

Vessel with micro-combustor Micro-combustor

25

X

Z

0.002999940.003499940.003999940.004499940.004999940.00549994

-0.0024

-0.0022

-0.002

-0.0018

-0.0016

-0.0014

-0.0012

-0.001

-0.0008

-0.0006

-0.0004

25072369223120931955181716781540140212641126988850

5 / SUMMARY AND CONCLUSIONS5 / SUMMARY AND CONCLUSIONS

PhD work :> experimental study of mixing without combustion : 2004 and 2005> computations : 0D and 3D (for the design of the future combustors)

Combustion tests :> to carry out ignition tests (hot wire or film, electrical discharge)> to assess the flame stability (influence of heat losses, equivalence ratio, type of fuel (hydrogen or hydrocarbon) ...> to evaluate the combustor efficiency (heat balance, RAMAN scattering)Micro-systems : > to study new concepts of micro-turbines and specific combustors for direct electrical generation (catalytic combustion)...> thrust and journal bearings

Cooperations :> with other ONERA’s department for PLIF, RAMAN, thermoelectricity, igniter, flow simulation inside micro-compressor ...> CEA (LITEN), INPG/LEG, Silmach, NEDO (post doc.), TMIT ... Manufacturing, mehanical/electrical conversion

26

Micro-manufacturingMicro-manufacturing

Centrifugal Compressor

Centripetal turbine

Si, Sic, Si3N4

MIT

5 / MICRO-TECHNOLOGIES 5 / MICRO-TECHNOLOGIES

27

GAS THRUST BEARING AND JOURNAL BEARING

GAS THRUST BEARING AND JOURNAL BEARING

• Rotating speed about 1 million rpm

200 m

MIT