Ignition, laser-induced

Fig. 5 Physiochemical processes involved in laser-induced ignition of RDX.

The theoretical model and numerical method outlined in the above sections were implemented to study steady-state combustion of nitramine monopropellants [33.34], laser-induced ignition of RDX [39,40], and steady-state combustion of nitramine/GAP pseudo-propellants [37-39]. The analyses were carried out over a broad range of operating conditions. Various important burning and ignition characteristics were investigated systematically, with emphasis placed on the detailed flame structure and the effect of the subsurface two-phase layer on propellant deflagration. 

The entire laser-induced ignition process of RDX in an argon environment has been studied in detail [39,40]. Figure 15 shows the predicted temporal evolution of the temperature field at an incident laser heat flux of 400 W/cm under atmospheric pressure. The initial temperature is 300 K. The interface between the subsurface and gas-phase regions is set to be x = 0, with negative and positive values of the. v-coordinate representing the subsurface and gas phase, respectively. The surface temperature is rapidly increased to 475 K within 1 ms, due to the high intensity of laser heat flux. The profiles for t < 1... 

Fig. 15 Evolution of temperature field during laser-induced ignition of RDX in argon at p = 1 atm and = 400 W/cm ...

The discrepancies among the existing experimental results may be attributed to the uncertainties associated with measurements under different types of experimental conditions. It is clearly evident that more measured data is needed for model validation. Nonetheless, the present model provides detailed insight into the key physiochemical processes involved in the laser-induced ignition of RDX, and can be effectively used to estimate ignition delay, heat release mechanisms, and flame structure. 

LDH LEU LIBD LAW LET LILW LIP LLNL LLW LMA LMFBR LOI LREE L/S LTA LWR Layered double hydroxide Low enriched uranium Laser-induced breakdown detection Low-activity waste Linear energy transfer Low- and intermediate-level nuclear waste Lead-iron phosphate Lawrence Livermore National Laboratory Low-level nuclear waste Law of mass action Liquid-metal-cooled fast-breeder reactor Loss on ignition Light rare earth elements (La-Sm) Liquid-to-solid ratio (leachates) Low-temperature ashing Light water reactor... 

The ignition of azides and other explosives is possible with laser beams of nonoptimized wavelength. A thermal mechanism of ignition is again the usual interpretation of data, but the precise role of laser-induced shock waves in these experiments has not been determined. Continuation of these investigations is... 

A brief summary of the theoretical formulation of physicochemical processes in various regions during the laser-induced RDX ignition process [40] is given below. The model for steady-state combustion can be treated as a limiting case by neglecting all the time-varying terms. 

Knapp M, Luczak A, Schltiter H, Beushausen V, Hentschel W, Andresen P. 1996., Crank-angle-resolved laser-induced fluorescence imaging of NO in a spark-ignition engine at 248 nm and correlations to flame front propagation and pressure release . Appl. Opt. 35(21) 4009-4017. 

Parr, T.P. and Hanson-Parr, D.M. (1986), The Application of Imaging Laser Induced Fluorescence to the Measurement of HMX and Aluminized Propellant Ignition and Deflagration Flame Structure Chemical Propulsion Information Agency Publication 457, Vol. 1, 249-261. 

J.A. Syage, E.W. Fournier, R. Rianda, R.B. Cohen, Dynamics of flame propagation using laser-induced spark initiation Ignition energy measurements. J. Appl. Phys. 64, 1499-1507 (1988)... 

The physical problem of concern is the ignition of a strand of RDX monopropellant induced by a continuous and radially uniform CO2 laser. The physiochemical processes involved are schematically illustrated in Fig. 5. The propellant and the ambient gas are initially at room temperature. Once the laser is activated, volumetric absorption of laser energy in the solid phase takes place, as shown in Fig. 5a. In the gas phase, only certain gaseous species, such as vapor RDX, absorbs a noticeable amount of laser energy at the wavelength of... 

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