NUMERICAL AND EXPERIMENTAL INVESTIGATION OF LIMITED CONDITIONS FOR IGNITION OF COMBUSTIBLE LIQUID VAPORS FROM IMPREGNATED CLOTH AT LOCAL HEATING

The results of numerical and experimental investigations of ignition for vapors of liquid combustible material coming from the surface of the impregnated fabric to them (with a thickness comparable to the size of the power source), at local heating. It was assumed that the initial time is known the volume fraction of the liquid fuel substance contained in the cloth. In contact with the heated surface of the cloth particles liquid evaporates, vapors of fuel and oxidizer are mixed, heated and ignite. The mathematical model includes the equations of motion, continuity, energy, diffusion, and the balance for the gas-vapor mixture with the oxidation reaction, the heat conductivity of a particle with the heat as a result of crystallization, the heat conductivity for fabric impregnated with liquid combustible. During the experimental research as a source of heating used a metal disc, which is heated to a temperature of 1473 K. The experiments were carried out for a typical fire-liquid — gasoline. Experimentally established that the size of the ignition source Rp = 3·10–3 m and Zp = 5·10–3 m minimum temperature steel particles at which the ignition is Tp = 1000 K. With an increase in Rp and Zp limit Tp decreases slightly, but not to reach 950 in any circumstances. Also found that, regardless of the temperature of the heat source for the local implementation of ignition must be the necessary condition of flammable liquid in the cloths > 30 %. Approximation dependences of ignition time delay for the system from the initial temperature of the heated metal particle and its size are received on the basis of results numerical investigations. In addition, illustrates a fairly good agreement between the results performed numerical and experimental investigations. Agood agreement between the results of the research with similar results for homogeneous structures — liquid fuels received.