Impact of Aluminium and Titanium Additives on Ignition and Combustion in Boron-Loaded Gelled Jet A-1 Fuel

A high-energy metal has been identified as a possible supplementary energy source for liquid fuel, which can be used to fuel volume-limited propulsive devices. However, the stability of metal particles in liquid fuel is a significant disadvantage, which can be overcome by suspending the particles in the gel fuel network. Boron's (B) high energy density makes it a potential choice as fuel or energetic fuel additive for propulsion systems. However, the combustion of boron particles is challenging due to a native oxide layer on the boron particle surface that acts as an inhibitor. The influences of aluminum and titanium addition into the gel fuel containing boron particles have been investigated in the present study to understand whether Al or Ti positively enhances the ignition and combustion of boron particles. A droplet combustion study was conducted for gel fuel samples containing boron, boron-aluminum, and boron-titanium combinations. The key analyses include the feature of droplet diameter regression, the effect of Al/Ti additive on the ignition delay of boron particles through spectroscopic analysis, combustion of boron particles through chemiluminescence measurement of intermediate species of boron combustion (BO2) and flame imaging, and analysis of combustion residues. The obtained results and corresponding analyses suggest that the addition of Al particles improves the ignition of boron. In contrast, Ti particles significantly enhance the combustion of boron particles loaded in gel fuel.