Plasma-Driven Combustion of Aerosolized Energetic Ionic Liquids

We demonstrate plasma-driven combustion of energetic aerosolized ionic liquids under flowing conditions. A mixture of hydroxylammonium nitrate (HAN) and 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]) is atomized through high-pressure injection into a nozzle, where HAN serves as the oxidizer, similar to the monopropellant AF-M315E (i.e., ASCENT), and EtSO4 provides the fuel. The aerosolized stream of particles is directed several centimeters downstream into a coaxial transient plasma discharge driven by high-voltage nanosecond pulses at a repetition rate of 10 kHz. The interaction with the plasma initiates and sustains combustion, producing visible flame formation. The atomization step dramatically increases liquid surface area, accelerating combustion kinetics relative to bulk liquid systems. In situ optical emission spectroscopy confirms the presence of reactive atomic and diatomic species, including atomic hydrogen, oxygen, nitrogen, CN, and C2, while broad continuum emission indicates high temperatures consistent with an exothermic combustion process. The particle size distribution was measured using a scanning mobility particle sizer (SMPS) and found to span the range from 400 to 800 nm in diameter. This proof-of-concept configuration separates the plasma from the injection nozzle; however, future system architectures may integrate the nozzle directly into the coaxial configuration as the central electrode in the coaxial discharge to further enhance ignition and control.