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Simulation of stability of ignition and combustion of energetic materials under
action of pulsed radiation
V.E. Zarko, L.K. GusachenkoInstitute of Chemical Kinetics and
Combustion, SB RAS, Novosibirsk 630090
EUCASS 2011
Melted and evaporated in the combustion wave EMs →→ classical explosives (RDX, HMX); recently synthesized HNF, ADN, and CL-20
Radiation driven transient combustion regimes →→→ practical applications / / source of information on chemical kinetics characteristics
Specific coupling between physical and chemical processes on the burning surface
INTRODUCTION
The goals of the research Developing theoretical model for describing radiation assisted transient combustion behavior of EM in order to study
• Stability limits of steady-state pyrolysis modes of semi-transparent EM in dependence on radiation absorption parameters and power level
• Ignition stability of semi-transparent EM under action of radiant fluxes of various time history
• Extinguishment of stationary burning EM upon action of single radiation energy pulse
Ignition transients
Initial compound
Final compound
YcY3
Ignition-combustion transients
Vaporization on the reacting surface is
described by the Clausius-Clapeyron law
(M/M1) Уg1,s P = const*exp(-L/RTs)
M -- molecular mass of gas mixture
M1 -- molecular mass of vapor
Уg1,s -- mass fraction of vapor above the EM surface
L -- latent heat of evaporation.
Problem Formulation
a) solid state Rm xxtx )(
)exp()(2
2
xtqx
T
x
TV
t
TC c
сc
mc
cc
(1)
Rm xxtx )(
,,0
,),(,)0,( 0
dt
dxV
x
T
TtxTTxT
mm
Rx
c
mmcc
Problem Formulation
cc
cmm
cc
c x
y))VV(
x
xV(
t
y
(3)
)RTEexp(yA,Q ccccccccc
(4)
cmmxxc
mmccmc VLx
TTtxTTxTtxy
m
00 )(,),(,)0,(,1),(
)exp()())((2
2
xtqx
T
x
TVV
x
xV
t
TC c
cl
ccm
mc
ccl
b) liquid state mxx0
(2)
c) gas phase (xL < x < 0)
W)x
T(
xx
T)
x
yD
C
CVV(
t
TC 21
3
1i
ii
p
picp
(5)
11
11
c1 )
x
yD(
xx
y)VV(
t
y
(6)
122
22
c2 )
x
yD(
xx
y)VV(
t
y
(7)
c) gas phase (xL < x < 0)
),RTEexp()y(A 1N
1111
),RTEexp()y(A 2N
2222
qzconstW
at ,tzttz,0xx 21L
0W in other cases
Instability of self-sustaining combustion
k = (Ts – To) ( lnrb/To)p
r = (Ts /To)p
Qm = Qm/c(Ts – To)
= c / l
m = (Tm – To)/(Ts – To)
Stability of steady-state combustion regimes
Stability of steady-state combustion regimes
A → r = 2 (k*-1)/(k*+1); B → r = 2 (k-1)/(k+1);
(stability limits at =1, Qm = 0.3)
r = (Ts /To)p
k = (Ts – To) ( lnrb/To)p
k*=1/(1+Qm)
11 /||
)0(/)0(
/
/
f
uuS st
11 /||
)0(/)0(
/
/
f
uuS st
11 /||
)0(/)0(
/
/
f
uuS st
Black colour = 100000 m-1, Dark – grey = 11500 m-1, Light grey = 1500 m-1
= 11500 m-1
Stability of ignition transients
kW/m2kW/m2
tH, s
tH, s
Black colour = 100000 m-1, Dark grey = 11500 m-1, Light grey = 1500 m-1
Stability of ignition transients
kW/m2
te, s
Black colour = 100000 m-1, Dark grey = 11500 m-1, Light grey = 1500 m-1
Stability of ignition transients
Extinguishing via action of a single radiant flux pulse, q0(Dt)
a=1000 cm-1
a=115 cm-1
kW/m2 kW/m2
kW/m2
kJ/m2
Dt,s
Radiation driven combustion of evaporated EMs is a source of information about the combustion mechanism.
Self-sustaining combustion regime fails for the EMs with significant heat release in the condensed phase and evaporation on the burning surface due to formation of temperature maximum in subsurface layer.
CONCLUSIONS
CONCLUSIONS (cont’d)
Melting heat makes effect on the stability of self-sustaining combustion: the larger the values of Qm and ∆T = Ts-Tm, the narrower combustion stability domain.
Stability of transition from ignition to stationary self-sustaining combustion depends on the steepness of radiant flux cut-off and transparency of EM.
CONCLUSIONS (cont’d)
• Further development of theoretical knowledge on transient combustion regimes urgently needs experimental substantiation.
• This, in turn, takes essential improvement of experimental techniques for measuring instantaneous burning rate and structure of the combustion wave.
Благодарю за внимание!Thanks for your patience!
Stability of steady-state combustion regimes
A → r = (k*-1)2/(k*+1);
c) gas phase (xL < x < 0)
(8)
0x
)V(
xV
t c
MTRp
2221113
3
2
2
1
1 Q,Q,M
y
M
y
M
y
M
1
(9)
0
0)0,()0,(;)0,(
21
210
x
y
x
y
x
T
xyxyTxT
at Lxx
y1 + y2 + y3 = 1
Dyx
Dyx
Dyx1
12
23
3 0
On the burning surface:
Lvyqx
T
x
Tcccrx
ccx
00 || (10)
v v y Dy
xy vc c c c1 1
1(11)
v v y Dyx
y vc c c c2 22 1 (12)
v v vc c c
bs TTR
LM
M
My
11exp 11
1 (14)
(13)