FEATURES OF GELLED FUEL IGNITION AT LOCAL HEATING

Results of numerical investigations of interrelated physical and chemical processes and phase exchanges (melting, evaporation) at ignition of typical gelled fuel hydrazine – liquefied oxygen by heating source with limited heat content — heated metal particle are presented. Estimation of influence for temperature and sizes of particle which determine heat content on the main ignition characteristics is carried out. Limited values of main parameters (temperature, sizes) of ignition source at the ignition is possible are established. The dependence of the ignition time delay from heat content of particles is determined. Comparison of ignition conditions for gelled fuel at local heating with solid and liquid combustible substances is performed. It is shown that sizes of local heating source have significantly less impact in contrast to the solid and liquid condensed substances. Energy source temperature plays the main role. This is due to significant thermal effects endothermic phase exchanges in the gelled structure. Establishing small characteristic dimensions of the layer warmed gelled condensed substance, small ignition time delay, the position of the area of the leading oxidation reaction in a small neighborhood of the phase exchange, relatively low oxidant and fuel concentrations which are sufficient for ignition indicate a high fire risk, comparable to the earlier studied solid and liquid fuels.