The article presents the results of experimental studies of water droplets propagation through the sample of typical forest fuel materials: needles, leaves, and their mixture. Different conditions are considered: without any additional energy supply, with heating, in the course of intensive thermal decomposition and flaming combustion. Three methods of registration are applied: thermocouple measurements, control of the weight of the sample as a whole and of its individual layers, and high-speed video recording. Water-based compositions with special additives (bentonite, bischofite, and foaming agents) typical for forest fire extinguishing systems are used. The experiments are carried out using aerosol and single water drops, as well as a small group of the latter. It is shown that the mechanisms, conditions and characteristics of droplet propagation through the layers of needles, leaves and their mixtures differ significantly. The scientific novelty of the work is the determining of the values of all the key characteristics of these processes in the conditions of intensive pyrolysis of the material, as well as through its inert layers.

This article presents the main findings of the experimental research into the fire suppression by continuous spraying of water over the combustion zone and by pulsed liquid aerosol delivery according to two schemes. The test samples contained either birch leaves only or mixed of (leaves, twigs, and needles). We monitored the temperature in the fuel bed and used thermocouple readings to determine the conditions and characteristics of suppressing the combustion and thermal decomposition of the material. Using optical methods and high speed recording, we obtained the parameters of sprayed liquid-flow as well as the processes involved in the interaction between liquid aerosol and the decomposing forest fuel. The experimental study helped us establish how much time and quenching liquid is sufficient to suppress the forest fuel combustion. Furthermore, we determined the influence of the forest fuel volume on the conditions and characteristics of the processes under study. Finally, we identified the main physical principles of the thermal decomposition of forest fuel when using the proposed approaches to spraying water into the combustion zone. The research findings enable the optimization of aerial firefighting in terms of wildfire containment and suppression.