Arvind Rao & J.P. Buijtenen
Infrared Signature Modeling of Infrared Signature Modeling of Aircraft Exhaust PlumeAircraft Exhaust Plume
Faculty of Aerospace Engineering
Aircraft Survivability
It has been observed that linear changes in aircraft survivability produce exponential changes in force effectiveness and aircraft attrition rates. Thus, stealth technology helps aircraft to avoid high aircraft loss rates and completet h e m i s s i o n o b j e c t i v e s e f f e c t i v e l y
Leading Edge
Aircraft Nose
Inlet Lip Drop Tank Nose
FuselageNozzle
Exhaust Plume
Sun Glint
Sources of Infrared Signatures
Radar
Exhaust plume, exhaust duct, tail boom heated by exhaust plume and the direct view of hot engine parts like turbine blades. Engine parts at a temperature of 600-700oC.
Infrared Signatures Sources in a Helicopter
Tail boom heated by plume
Engine & Exhaust
AIM 4D, AIM 9L/M (Sidewinder), ASRAAM, MICA, Mistral, Python-3, R.530,
R.550, Shafrir, Stinger
AA-2, AA-3, AA-5, AA-6, AA-8, AA-10, AA-11, PL-2, PL-
5B, PL-7
Air to Air (AAM)
Chaparral, Mistral, Redeye, Stinger SA-7, SA-9, SA-13, SA-14, SA-16, SA-18
Surface to Air (SAM)
Western MissilesSoviet Block MissileMissile Type
Common heat-seeking missiles and their origin
The IR Threat
Plume IR Signature Modelling
5km
0º (Horizon)180ºSAM
90º (Zenith)
A Simple Mission
M = 0.8
The Modeling Strategy
ωd
∑ωplDetector element
Reticle
MISSILE IR SEEKER
IR Transparentwindow R
SAM
Plume (discretised)
aircraft
SAM IR Seeker (instantaneous field of view )
[ ] ( ) ( )( )min
1,
1,,,,,, )1(
ξ⋅
τ⋅⎭⎬⎫
⎩⎨⎧
−+−+τ−−∑ ∑= =
NEI
AIIAIIAII atm
N
itptpbgtp
N
ifuseifusebgfuseipliplplbgpli
pl fuse
RLO =
CFD Simulation of the Exhaust Plume
Nozzle exit plane
Diamond ShockExpansion fans
Mac
h N
o.
Magnified view
Direction of the Plume
Plume center line
Plume Mach number contours obtained from CFD
Nozzle exit plane
Diamond Shock
Stat
ic T
empe
ratu
re (K
)
Magnified view
Direction of the Plume
Plume center line
Plume static temperature contours obtained from CFD
Validation of the Exhaust Plume Simulation
Y/Rnz
0
0 .1
0 .2
0 .3
0 .4
0 .5
0 .6
0 .7
0 .8
0 .9
1
0 0.5 1 1.5 2 2.5 3 3.5 4
"te mp .txt ""te mp .txt "
"te mp _h.tx t "
(T-T
amb)/
(Tc-T
amb)
PresentGauffre
Heragu etal
Temperature profile across the jet at X/DN =10
Y/Rnz
Concentration profile across the jet at X/DN =10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5 2 2.5 3 3.5
"CO2.txt""CO2.txt""CO2.txt"
C/C
C
PresentGauffre
Heragu etal
0
50
100
150
200
250
300
350
400
450
500
3 4 5 6 7 8
"total.tx t""total.tx t"
"heragu1.txt"
Present Heragu etal. Measured
Wavelength (µm)
Inte
nsity
(W/m
2 ⋅Sr⋅µm
)
Comparison of predicted infrared intensity(Plume + Nozzle)
0
50
100
150
200
250
300
350
400
450
500
1 2 3 4 5 6 7 8
"total.txt""total.txt""total.txt"
Plume radiation Nozzle radiation Total radiation
Wavelength (µm)
Inte
nsity
(W/m
2 ⋅Sr⋅µ
m)
predicted infrared intensity(Plume + Nozzle)
Validation of the Exhaust Plume Simulation
Validation of the Exhaust Plume Simulation
0
20
40
60
80
100
120
140
160
180
0 2 4 6 8 10 12 14 16 18 20
"irr_5km.out"
Wavelength (µm)
Spec
tral I
nten
sity
(W⋅m
-2⋅S
r-1⋅µ
m-1
)
H2O
CO2, CO
H2O, CO2
CO2
Spectral radiant intensity of aircraft plume
Plume emissive bands absorbed by the atmosphere
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2 4 6 8 10 12 14 16 18 20
"temp.txt""temp.txt"
Non
-dim
ensi
onal
ised
plu
me
inte
nsity
/Atm
. tra
ns
Atm. TransPlume intensityAtm. TransPlume intensity
Exhaust Plume Solver Validation
Wavelength (µm)
2 2.5 3.0 3.5 4.0 4.5 5.0 5.50
25
50
75
100
Rel
ativ
e S
pect
ral I
nten
sity
(-)
La Rocca, A. J., “Artificial Sources,”The Infrared Handbook, 1985
Spectral intensity from airc`raft plume for Boeing passenger aircraft
Wavelength (µm)
0
5
10
15
20
25
30
35
40
45
2 2.5 3 3.5 4 4.5 5 5.5 6
"irr_5km.out"
Plume spectral radiant intensity as transmitted by atmosphere
Lock-on Range due to the Plume
5km
0º (Horizon)180º SAM
90º (Zenith)
Mission
0 2 4 6
1
2
3
4
5
6
7
Wavelength (µm)
Lock
on
Ran
ge (k
m)
Lock-on Range due to Plume Radiation
• A comprehensive methodology is presented to model the IR signature produced by the aircraft exhaust plume and to evaluate its susceptibility against an IR guided SAM.
• The results qualitatively match well with the results available in the literature.
• The prominent band for plume radiation are centered around 2.7 µm, 4.3 µm, 5.5 µm, 6.5 and 15 µm due to the emission by CO2 , CO and H2O present in the plume.
• Since the exhaust plume and the atmosphere have same radiative participating species, namely H2O, CO2, & CO, most of the IR radiation emitted by the plume is absorbed in the intervening atmosphere.
• Only the radiation emitted from the broadened wings of the plume emissive bands prominent in the 4.15-4.2 µm band reaches the missile IR detector in the non after burning mode.
• The aircraft is susceptible to ground based IR guided SAMs due to the radiation emitted by its plume.
Exhaust Plume Dilution and Mixing for Bell 205 Aircraft
Todda Rabba
Infrared Signature Suppression
AIRCRAFT
F117-A, Night hawk
Exhaust pipe of F-117A
F117 Nozzle Configuration for IR Signature Reduction
Schematic of the basic Centre Body Tailpipe used on Bell 205 (UH-1H)
Bell 205 using Infrared Flares to deceive an incoming IR missile
Exhaust Plume Dilution and Mixing for Bell 205 Aircraft