Simulation of stability of ignition and combustion of energetic materials under action of pulsed radiation V.E. Zarko, L.K. Gusachenko Institute of Chemical Kinetics and Combustion, SB RAS, Novosibirsk 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

Initial compound Final compound YcYc Y3Y3 Ignition-combustion transients

Vaporization on the reacting surface is described by the Clausius-Clapeyron law (M/M 1 ) У g1,s P = const*exp(-L/RT s ) M -- molecular mass of gas mixture M 1 -- molecular mass of vapor У g1,s -- mass fraction of vapor above the EM surface L -- latent heat of evaporation. Problem Formulation

a) solid state (1) Problem Formulation

(3) (4) b) liquid state (2)

c) gas phase ( x L < x < 0) (5) (6) (7)(7)

c) gas phase ( x L < x < 0) at in other cases

Instability of self-sustaining combustion

k = (T s – T o ) (  lnr b /  T o ) p r = (  T s /  T o ) p  Q m = Q m /c(T s – T o )  = c / l m = (T m – T o )/(T s – T o ) Stability of steady-state combustion regimes

A → r = 2 (k*-1)/(k*+1); B → r = 2 (k-1)/(k+1); (stability limits at  =1,  Q m = 0.3) r = (  T s /  T o ) p k = (T s – T o ) (  lnr b /  T o ) p k*=1/(1+Q m )

Black colour  = m -1, Dark – grey  = m -1, Light grey  = 1500 m -1  = m -1 Stability of ignition transients kW/m 2 t H, s

Black colour  = m -1, Dark grey  = m -1, Light grey  = 1500 m -1 Stability of ignition transients kW/m 2 t e, s

Black colour   = m -1, Dark grey  = m -1, Light grey  = 1500 m -1 Stability of ignition transients

Extinguishing via action of a single radiant flux pulse, q 0 (  t)  =1000 cm -1  =115 cm -1 kW/m 2 kJ/m 2  t, 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 Q m and ∆T = T s -T m, 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.

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Stability of steady-state combustion regimes A → r = (k*-1)2/(k*+1);

c) gas phase ( x L < x < 0) (8) (9)(9)

at y1 + y2 + y3 = 1

On the burning surface: (10) (11) (12) (14) (13)