Ignition of hydrogen peroxide with gel hydrocarbon fuels

Experimental counterflow and impinging jet studies and modeling analysis of hypergolic hydrogen peroxide (H₂O₂) and gel hydrocarbon fuel/particle mixtures were conducted to characterize condensed phase reaction rates and ignition delay times. The mixtures consisted of n-dodecane, n-heptane, and kerosene containing fumed silica and sodium borohydride (NaBH₄) particles. Scanning electron microscopy, x-ray photoelectron spectroscopy, and simultaneous thermogravimetric and differential scanning calorimetry analysis of the NaBH4 particles were performed to characterize particle size, size distribution, geometry, surface composition, and thermal decomposition. Liquid-phase counterflow experiments were used to derive a global rate constant for the condensed phase reaction between H₂O₂ and NaBH₄. Chemical kinetics calculations were performed using the condensed phase global reaction coupled with a detailed gas phase mechanism for hydrocarbon oxidation to phenomenologically study the ignition process. Shorter ignition delays were achieved when fuel flow was established before oxidizer injection. Ignition delay decreased with NaBH₄ addition until a limiting loading was achieved, after which ignition delay remained nearly constant. Elevating the reactant temperature reduced ignition delay, consistent with fuel volatility trends. Modeling results show that the ignition process relies upon the reaction between NaBH₄ and H₂O₂ to gasify and heat an ignition kernel to the H₂O₂/fuel mixture autoignition temperature.