RDX flame

Temp and relative intensities of the combustion products detected as a function of height along an RDX flame are shown in Fig 8 (Ref 67d). Intense radiation from the OH radical is observed immediately next to the combustion surface of the RDX sample. The intensity of the radiation attains its max value at a distance of 0.1mm and varies slowly with further increase in height along the flame. Luminescence of the radicals C2, CN, and CH appears at a distance of 0.1—0.2mm from the combustion surface and increases markedly as the zone of max temp in the flame is approached... 

Ermolin et al. have theoretically investigated the detailed chemistry of the secondary luminous stage of an RDX flame which they have successfully compared... 

Table III. Calculated gas-solid boundary mass end energy conditions for an RDX flame at 1 atm and 20 atm.

Fig, 8. Temperature and species concentration (mole fraction) profiles as a function of distance (mm) for the RDX flame at 1 atm. Origin corresponds to the gas-solid interface. 

Fig. 9. Chemical production and removal rates as a funcion of distance ( im) for (a) HCN and (b) CO in the RDX flame at 17 atm, indicating the various reaction zones of the flame. Numbers on curves refer to the specific elementary reactions listed in the figure. The total rate for production or removal is also plotted.

Fig. 10. Chemical reaction flow diagrams for the (a) primary and (b) secondary stages (or zones) in the RDX flame at 17 atm. The spatial extent of the zones is indicated by the distances given in um. We have separately indicated the reaction chemistry of the carbon species, the nitrogen species of the amino group of the RDX ring, and the nitrogen chemistry of nitro group of RDX. A similar reaction flow diagram exists for other flame pressures except that the distances must be scaled. Thick arrows indicate major pathways, while thin arrows indicate minor pathways.

For the RDX flame, we can also use sensitivity analysis to determine the importance of condensed phase physical properties in affecting the bum velocity. The results are shown in Fig. 12. As expected, one sees that the burn rate is very sensitive to the initial temperature of the propellant. Similarly, one also sees a strong dependence on pressure. 

Fig. 11. Sensitivity analysis of the flame speed to changes in the pre-exponential rate constant for the elementary chemical reactions. A negative dependence means that increasing its rate constant would slow the burn rate. Shown in the figure are the most sensitive reactions affecting the bum rate to the RDX flame.

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