Boron combustion enhancement using titanium and zirconium nanoparticles for fuel in ducted rocket applications

Boron’s exceptional energy density makes it a prime choice as a component of fuel and propellant in ramjet variants of ramjet like solid fuel ramjets (SFRJ) and solid fuel ducted rockets (SFDR). Experimental observations reveal that boron (B) combustion is hindered by a boron oxide (B2O3) shell on active boron particles. Researchers have proposed various strategies to enhance boron particle combustion, with the primary approach involving the addition of metal additives to potentially improve combustion efficiency. A ducted rocket (DR) is considered appropriate for the current study due to its provision of two combustion chambers, facilitating the two-stage combustion of boron particles. In the current study, paraffin wax with boron particles serves as the baseline fuel, while titanium (Ti) and zirconium (Zr) particles are burned alongside boron to assess their effects on boron particle combustion. The elevated combustion heats of Ti and Zr are expected to hasten the removal of B2O3. The addition of Ti and Zr also reduces the ignition time delay. The current study utilizes a hybrid fuel ducted rocket (HFDR) that relies on gaseous oxygen as its oxidizer. Three boron-based solid fuel grains are experimentally tested for their ducted rocket motor performance in a lab facility, and their combustion performance is assessed. These samples comprised paraffin wax containing B particles, paraffin wax incorporating B and Ti particles, and paraffin wax incorporating B and Zr particles. Thermal gravimetric analysis (TGA) was employed to determine the combustion efficiency by studying the active boron content in the condensed combustion product (CCP). It is expected that the addition of metal particles will elevate combustion efficiency as it will noticeably decrease the active boron content in the CCP compared with the fuel containing only boron.