Effect of the fluid–vapor phase transition in the combustion of calcium with iron trifluoride

Combustion of a $\mathrm{Ca}$–$\mathrm{FeF}_3$–$\mathrm{Fe}$ model system is under study. It is shown that the combustion front propagation in the $\mathrm{Ca}$–$\mathrm{FeF}_3$–$\mathrm{Fe}$ system is focal. The foci of ignition of calcium particles arise ahead of the front, followed by the expansion of the reaction zone until the foci completely merge with each other and with the formation of new centers of ignition in the heating zone. The dependences of the temperature and the burning rate on the degree of dilution with iron and pressure in the system are presented. Thermodynamic calculations are performed, and the calculated and experimental data are compared. Under the general tendency of an increase in the burning rate with increasing pressure, its decrease was found to be associated with the vapor – calcium metal liquid phase transition.