A comprehensive analysis of laser-induced ignition of RDX monopropellant

A comprehensive analysis of laser-induced ignition of 1,3,5-trinitrohexahyd ro-s-triazine (RDX) monopropellant has been performed with consideration of detailed chemical kinetics. The model considers the transient development in the entire combustion zone, including the solid-phase, subsurface two-ph ase, and gas-phase regions. The formulation accommodates detailed chemical kinetics and transport phenomena in the gas phase, as well as thermal decom position and subsequent reactions in the subsurface two-phase region. Therm odynamic phase transition and volumetric radiant energy absorption are also considered for completeness. The analysis is capable of treating the compl ete ignition process from surface pyrolysis to steady-state combustion, wit h the instantaneous burning rate and surface conditions treated as part of the solutions. Numerical experiments were conducted at atmospheric pressure in argon with CO2 laser heat flux from 35 to 600 W/cm(2). Excellent agreem ent was obtained between the calculated and measured ignition delays. The p ropellant gasification rate increases with increasing laser intensity, whic h in turn shortens the ignition delay. The entire process can be divided in to six stages: inert heating, thermal decomposition, occurrence of primary flame, preparation and formation of secondary flame and, finally, establish ment of steady-state combustion. The major process in the primary flame is identified as the consumption of CH2O, HONO, NO2, H2CN, H2CNNO2, and HNO. I n the secondary flame, the conversion of NO and HCN to N-2, CO, H2O, and H- 2 is the key exothermic process causing ignition in the gas phase. (C) 2001 by The Combustion Institute.