Modeling of Plasma Ignition of Low Cetane Fuels in an Aerial Internal Combustion Engine

Reliable ignition of low-cetane fuels under engine-relevant, lean, or low-temperature conditions remains a critical challenge for advanced aerial internal combustion systems. The present study numerically investigates low cetane (CN 17) alcohol-to-jet (ATJ) synthetic aviation fuel (SAF) ignition assisted by nanosecond repetitively pulsed (NRP) discharges, using a novel two-stage modeling framework. The plasma discharge is represented using a phenomenological model, which partitions each pulse’s energy into vibrational and electronic excitation of N2, where, the latter subsequently quenches, resulting in ultra-fast O2 dissociation and gas heating, thereby capturing the key thermal and non-thermal effects of NRP discharges in a computationally efficient manner. To enable tractable simulations with detailed chemistry, a reduced chemical kinetic model comprising 49 species was developed from a detailed CRECK mechanism using the Directed Relation Graph with Error Propagation (DRG-EP) technique, and was employed in all simulations presented in this study. Firstly, non-reacting CFD simulations of a single-cylinder compression-ignition engine are conducted to generate realistic pressure, temperature, and mixture profiles. These fields are then used as initial conditions for 3D plasma-assisted ignition simulations of a single discharge and multiple NRP discharges at different deposited energies. Results from single-pulse simulations first demonstrate effective plasma-fuel interaction only upon strategically placing the plasma igniter, evidenced by rapid OH radical production within the discharge volume. Furthermore, the analysis reveals that a strategy of multiple lower-energy pulses yields superior ignition characteristics compared to a single high-energy discharge. This effectiveness is confirmed under high-altitude conditions, where multiple pulses at just 5 mJ/pulse successfully ignite the CN 17 fuel, whereas a conventional high-energy spark (60 mJ) fails to initiate combustion. These findings highlight the critical advantage of accessing specific kinetic pathways via non-equilibrium plasma to ensure reliable ignition where pure thermal methods fall short.