Regression rates and burning characteristics of boron-loaded paraffin-wax solid fuels in ducted rocket applications

Boron based solid fuels have remained attractive for solid fuel ducted rocket (SFDR) applications since long due to their potential to release high energy on combustion. However, boron's energetic potential has not been successfully harnessed even till date in any practical combustion system. In view of this, present investigation is focused on utilizing boron nanoparticles embedded in paraffin-wax in various proportions (5-20% by weight) as solid fuel. To evaluate its performance an opposed flow burner (OFB) is used in presence of gaseous oxygen (GOX) and the oxidizer mass flux (Gox) varies from 5 to 30 kg/m2 s to estimate its regression rates relative to paraffin-wax. Burning process of boron loaded samples was captured using a high-speed camera to understand the ejection trajectory of the particles/agglomerates. Further, different material characterization techniques were employed on the pre- and post-burnt samples to understand the chemical and morphological changes and interlink that with overall burning characteristics. The active boron content determined from thermogravimetric analysis of pre-burnt sample, ejected agglomerates and post-burnt residue were 78.8, 34 and 18.7% respectively which confirm the combustion of boron nanoparticles up to a significant extent in the present OFB configuration. The present study may be helpful in futuristic application of hybrid propellant-based gas generator for SFDR systems.