Double flame structure in AP combustion

Burning of ammonium perchlorate (AP) in composite solid propellants was simulated, employing a counterflow burner in which the heat feedback from the hot, inert opposing flow stabilized the AP monopropellant flame above a pressed AP strand. The heat feedback mechanism was investigated using thermocouples and a heat flux meter. The regression rates of AP were analyzed by use of activation energy asymptotics and the overall activation energy of the AP flame was found to be 14.3 kcal/mole. Results showed the typical burning structure of AP at 1 atm to consist of a 5000 μm thick thermal layer in the solid phase and a 500 μm thick AP flame in the gas phase. Temperature measurements using fine thermocouples showed the surface temperature to be 810 K and the flame temperature to be 1220 K. The lower flame temperature suggests that AP burns under a non-equilibrium condition.