CHARACTERISTICS OF MICROEXPLOSIVE DISPERSION OF GEL FUEL PARTICLES IGNITED IN A HIGH-TEMPERATURE AIR MEDIUM

Abstract

Gel fuels are the §ammable liquids, the rheological properties of which are changed by adding certain thickeners and performing a series of operations leading to the formation of the required consistency [1]. Until now, no attempts have been made to comprehensively study the processes of ignition and combustion of gel fuels based on cryogels (three-dimensional elastically deformable structure) with the addition of various ¦ne particles including the metal ones. Therefore, the purpose of this work is an experimental study using a software and hardware complex for high-speed video recording of the ignition and combustion processes of single particles of a group of compositions of modi¦ed gel fuels in a high-temperature motionless air medium under conditions of dispersion of melt droplets. An experimental study of the characteristics of the processes occurring during ignition and combustion of single particles (10 mg) of typical gel fuel in a high-temperature air environment was carried out using a software and hardware complex consisting of a high-speed video camera, LED spotlight. The group of fuel compositions is prepared on the basis of oil-¦lled cryogels without and with 30 %(wt.) addition of solid ¦nely dispersed components (coal particles, Si, or Cu). Polyvinyl alcohol was used as an organic polymer thickener (10 %(wt.) in an aqueous solution). As a result of experimental studies for a group of gel fuels compositions including those with the addition of ¦nely dispersed metal/ nonmetal particles, the di¨erence in the mechanisms of ignition andcombustion of single particles in a motionless high-temperature air environment has been established. Unlike single-component liquid fuels, the multicomponent composition of gel fuels has a positive effect on combustion and dispersion processes. Oil-¦lled cryogels were prepared with the addition of various ¦ne modi¦ers (coal particles, inert particles, and Cu) and without them. All resulting fuel compositions ignite upon radiant heating in the source temperature range of 600 1000 ◦C. However, the most intense ignition occurs for composition No. 2 with the addition of ¦ne coal particles. Gel fuel with inert particles (composition No. 3) demonstrates the lowest ignition and combustion characteristics (highest td and lowest Vp) which is due to the incombustibility of the additive. When the air temperature in the muªe furnace is varied from 600 to 1000 ◦C, the ignition delay times are set as well as the velocities of the §ying o¨ fragments during the dispersion of the fuel melt droplets. The ignition delay times vary from 1 to 10 s and the velocities of the fragments moving as a result of dispersion vary from 0.3 to 1.4 m/s for di¨erent fuel compositions. At temperatures of the heated air above 900 ◦C, the component composition of the fuel does not significantly a¨ect the ignition delay times.