The gel fuel ignition at local conductive heating

[Display omitted] •Hot metal and nonmetal particles ignite gel fuels, including at initial temperatures close to 120 K.•The initial temperature of particle should be not less than 1050 K at its characteristic size over 10 mm.•The size and shape of particle do not affect significantly the process characteristics in the case of stable ignition.•The developed mathematical model reliably describes ignition process. An experimental study of ignition of a gel fuel at local conductive heating has been performed. The initial temperatures of the fuel samples were 120, 260, and 290 K. Metal particles in the shape of a sphere, a disk, and a parallelepiped with a characteristic size of 10 mm were used as ignition sources. The initial temperature of the heating sources varied in the range of 1050–1350 K. The use of software and hardware high-speed video recording (4200 frames per second at a maximum resolution of 1280 × 800 pixels) allowed analyzing the regularities of physical and chemical processes, occurring during the induction period. Limit conditions necessary for stable ignition of a gel fuel and dependences of ignition delay time on parameters of a local heating source have been established. A low-inertia (sampling rate of 100 Hz) measuring system based on miniature thermocouples and an oscilloscope served to establish the velocities of the gel fuel melting front motion from the contact boundary between the metal particle and the fuel in the direction of the thermal wave propagation during induction period and under stationary combustion. The mathematical model of ignition of the gel fuel has been developed within the framework of the mathematical apparatus of continuum mechanics and the theory of chemical kinetics. The results of numerical simulation are in good agreement with the experimental data obtained. The applicability limits of the developed model within which it reliably describes characteristics of ignition have been established. The mathematical model may be used to develop advanced energy-efficient technologies for ignition of new fuels in wide ranges of parameters of the system gel fuel/local heating source.