Centre de Toulouseunité MH
Thermal gradient estimation using rainbow thermometry
ONERA Research team
Nicolás GARCIA ROSAYves BISCOSGérard LAVERGNE
MUSCLES meeting Karlsruhe, September 21 2004
MUSCLES meeting -- Karlsruhe, September 21 2004
Experimental device
Temperature measurements
Objectives
Theoretical aspects
Solving methods
Thermal gradient estimations : examples
PRESENTATION OUTLINE
MUSCLES meeting -- Karlsruhe, September 21 2004
EXPERIMENTAL DEVICE
Rainbow system ;
LIF system ; Shadowgraphy
.
Monodisperse injector ; Argon laser (514,5
nm) ;
MUSCLES meeting -- Karlsruhe, September 21 2004
LIF AND RAINBOW MEASUREMENTSEvaporating 100µm droplets tinj = 54 °C ta = 24 °C
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
0 5 10 15 20 25 30 35 40 45 50 55 60
Distance to injector (mm)
Te
mp
era
ture
(°C
)
1 st order2 nd orderLIF
MUSCLES meeting -- Karlsruhe, September 21 2004
Combustion 100µm droplets tinj = 37 °C ta = 25 °C
20
25
30
35
40
45
50
55
60
65
70
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70Distance to injector (mm)
Te
mp
era
ture
(°C
)
1 st order2 nd orderLIF
LIF AND RAINBOW MEASUREMENTS
Ignitor
MUSCLES meeting -- Karlsruhe, September 21 2004
Improvement of the rainbow technique :
OBJECTIVES
considerable thermal
gradients during heating
phase
– Correction of temperature measurement ;
– Estimation of thermal gradients ;
average temperature of a heating droplet
LIF : gradient-insensitive measurement Two solving methods
MUSCLES meeting -- Karlsruhe, September 21 2004
Generalized Lorenz-Mie theory (GLMT)-based
calculations
Measurements from experimental device
evaporation model :
34.5
35
35.5
36
36.5
37
37.5
38
0 0.2 0.4 0.6 0.8 1
reduced radius r/R
Tem
per
atu
re (
in °
C)
AVAILABLE TOOLS
expected spherical temperature profile
scattered intensity
theoretical models
simple correlation
MUSCLES meeting -- Karlsruhe, September 21 2004
LIGHT SCATTERING AROUND DROPLET
correlations used
MUSCLES meeting -- Karlsruhe, September 21 2004
THEORETICAL ASPECTS
– Geometrical optics ;
– Airy-Walker theory ;
– Lorenz-Mie theory ;
– Generalized Lorenz-Mie theory.
Geometrical optics
Lorenz-Mie theory Generalized Lorenz-Mie theory
Gaussian, off-axis laser beam
MUSCLES meeting -- Karlsruhe, September 21 2004
COMBINING THE DIFFERENT TOOLS
MUSCLES meeting -- Karlsruhe, September 21 2004
SOLUTION OF THE SYSTEM
MUSCLES meeting -- Karlsruhe, September 21 2004
RECALL OF THE TWO SOLVING METHODS
MUSCLES meeting -- Karlsruhe, September 21 2004
SIMULTANEOUS MEASUREMENT of MEAN TEMPERATURE and THERMAL
GRADIENT
2-periodicity :multiple
solutions !
MUSCLES meeting -- Karlsruhe, September 21 2004
GRADIENT ESTIMATIONS : evaporating droplets
set-up
Airy-Walker classical rainbow inversion
Airy-Walker classical rainbow inversion
LIF measurement
Rainbow/LIF estimation
MUSCLES meeting -- Karlsruhe, September 21 2004
GRADIENT ESTIMATIONS : burning droplets
set-up
Airy-Walker classical rainbow inversion
Airy-Walker classical rainbow inversion
LIF measurement
Rainbow/LIF estimation
MUSCLES meeting -- Karlsruhe, September 21 2004
CONCLUSIONS, PERSPECTIVES
–New correlation obtained from the fringe pattern phase in forward direction.
–The coupling LIF / Rainbow gives a good evaluation of the thermal gradients, especially in burning regime.
–The second order rainbow provided no additional information.
–Some problems must be resolved to get simultaneously the mean temperature and the thermal gradients from the above refractometry technique.
–Actually the coupling of the two techniques : Infrared and Rainbow is going on. The obtention of the surface temperature by infrared method will be another important information to be used for the validation of thermal gradients measurement.
MUSCLES meeting -- Karlsruhe, September 21 2004
1
2,
).(5
2
kThccn e
hcTL
IR MEASUREMENT
IR thermal flux
IR detector
T°cn
Black body spectral energy Planck ‘s law
with : h = Planck’s constant = 6.6262 10-34 J.K-1
k = Boltzmann’s constant = 1.3806 10 -23 J.K-1
c = Light speed = 2.9979 108 m.s-1
Thermal flux emission in the IR range
en [W.Sr-1.m-3]
Black body
...)(.,, gcng TLTL Real body brightness
MUSCLES meeting -- Karlsruhe, September 21 2004
MESUREMENT TECHNIQUE : SIGNAL SHUT-OFF METHOD
Black body
Droplet stream
injector
IR signal
Peri
od
T
IR detector
+ non-intrusive+ no calibration needed+ correction of the system’s non-linearities- droplet position / time relation
Time
Voltage
V=0 => equal fluxes
Droplet signal ( Tgoutte > Tcn )
Blackbody signal
Period T
MUSCLES meeting -- Karlsruhe, September 21 2004
SPECTRAL BAND SELECTION :MEASUREMENT PROCESS
),(
1.
sin. 02 TAd
fDTEB
[K]
with
dTLT
DT goutteBLIPgoutte .,).().(),( *
: merit factor
1E+8
1E+9
1E+10
270 280 290 300 310 320 330
Droplets temperature (K)
Band 3-5 micronsBand 8-12 microns
DTEBEmissivity
Emissivity calculated by Mie theory
Ethanol droplets
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Wavelength (µm)
Em
issi
vity
Droplet emissivity
Detector 10.13 spectral reponse
Droplet
AmbientField of view
Lens aperture
Sensor (Ad)
Cold filterLens