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.